Factors required for Complex Life
The following is a list of things required in order to maintain/ sustain complex life- (outside of the required chemical processes at the cellular level). The point of the list is to show how very incredibly lucky we are. We won the cosmic lottery! Or is there a purpose for our existence? Does Occam’s Razor really favor one designed universe over multiple chance collisions & multiple lucky events? Does science really favor the chance collisions & multiple lucky events scenario? (also mixed in are the ways the factors aid in scientific discovery)
ID vs. sheer dumb luck- You decide.
Factors for complex life:
1. Liquid water
a. Enough surface water to help regulate the planet’s temperature
b. Good solvent
c. Transports minerals
d. The presence of liquid water means the planet is in the habitable zone of it’s local star (Sun)
e. The presence of liquid water defines the CHZ (Circumstellar Habitable Zone. The CHZ of our solar system lies between Venus & Mars. Some scientists have narrowed it to:
-If the Earth were 5% closer to the Sun – too hot, no liquid water
-If the Earth were 20% father away from the Sun- too cold carbon dioxide would build up
2. Carbon based
a. Great bonding affinities
b. Allows for complex macro-molecules
3. Terrestrial planet
a. Crust thin/ thick and pliable enough to allow for plate tectonics
b. Recycling of minerals
c. Plate tectonics means the crust is sitting on an active core
d. Must retain enough heat for convection, i.e. keep the core liquid
e. Convection mixes the elements & shapes the continents
f. Active iron core is required to generate a protective magnetic field
g. Magnetic field has to be strong enough to withstand the solar winds
h. Must provide protection from radiation
4. Oxygen atmosphere
a. Our oxygen/ nitrogen mix is good
b. Clear- allows for good viewing
c. Ours is <1% of planet’s diameter
d. Allows in the right kind of light for viewing
5. Stable circular orbit
6. Large Moon (see also Gonzalez, G., “Wonderful Eclipses,” Astronomy & Geophysics 40, no. 3 (1999): 3.18- 3.20) (J. Laskar et al., “Stabilization of the Earth’s Obliquity by the Moon,” Nature 361 (1993): 615-17)
a. Our Moon is ¼ the size of Earth
b. Stabilizes the Earth’s axis of rotation
c. Gives our oceans a required tidal action
d. Just so happens that our Moon is 400x smaller than the Sun, which is 400x farther away
e. Both with a very circular shape
f. Allows for perfect solar eclipses
g. Confirmed Einstein’s prediction with the 1919 solar eclipse (gravity bends light) when scientists photographed the Stars behind it. We could have only made that discovery during a total solar eclipse.
h. Light spectrum
i. Observing & studying the Sun’s chromosphere is made possible
7. Gas Giants
a. Protection from intruding cosmic debris
b. Great for observing & scientific discovery
8. Sun- Spectral type G2 dwarf main sequence star-
a. If it were smaller the habitable zone would shrink and any planets in that zone would be locked into a synchronous orbit (rotation = revolution) as our Moon is with us
b. Total number estimated in the Milky Way- 100 billion
c. Over 80% are low-mass red dwarfs (most likely lack a habitable zone)
d. 1-2% are massive short-lived blue giants
e. Only about 4% of the stars are early G-type, main-sequence stars like our Sun
f. 50% of those are in binary systems
g. Then we have to consider what % of those are in the Galactic Habitable Zone
9. Location in the galaxy- Galactic Habitable Zone
a. We are between spiral arms
b. Perfect for viewing
c. Not a lot of activity
d. Not too close to the violent and very active center
e. More radiation near the center
Neighbors
Not a good viewing platform from which to discover
Not so far away where the heavy elements are scarce
10. Fine-tuning
a. Laws of Nature
b. Laws apply here also apply anywhere
c. Constants that are independent of those laws
Summary:
Within the Galactic Habitable Zone
Within the Circumstellar Habitable Zone
Liquid water
Orbit a Spectral type G2 dwarf main sequence star
Protected by gas giants
Nearly circular orbit-
Oxygen rich
Correct mass
Large moon to stabilize the angle of rotation
Moderate rate of rotation
Terrestrial planet
Ratio of water to continents
Plate tectonic re-cycling
Magnetic field
Both plate tectonics and the magnetic field require the core have enough heat to keep it liquid. The convection currents mix the minerals before recycling and also produce the required magnetic field as it flows around the iron inner core.
The Earth’s orbit is slightly elliptical. When the Earth is closest to the Sun (perigee) the southern hemisphere is enjoying summer, i.e. the Earth’s axis of rotation has the southern hemisphere at a better angle (than the northern hemisphere) towards the Sun for absorbing its vital rays. The Earth has the bulk of its continents in the northern hemisphere. Water stores the heat and then transfers it around the globe.
The above list contains factors required for complex life, but life is not guaranteed to arise even if all factors are met. The fact that a large, stabilizing moon is required and ours just happens to provide us with a huge natural setting in which we can & have conducted a multitude of scientific experiments that have increased our knowledge base and confirmed scientific predictions, is just the tip of the iceberg when it comes to evidence to support their finding that habitability = measure-ability. Think about it. In the accepted age view of the solar system & Earth, with the Moon’s recession rate coupled with the Sun’s expansion rate, these perfect solar eclipses, along with the scientific discoveries that accompany them, will soon be gone (10 million years). The best place for viewing eclipses, is also the only place in the solar system with perfect solar eclipses, is also the only place with conscious observers and we, intelligent observers, just happened to arrive when the scenario was best for scientific discovery.
Earthquakes, even though very destructive, are a necessary byproduct of the required plate tectonic recycling. They also offer us a way to measure the density of the material between designated points via the sound waves produced by plate movement. Volcanoes offer a way to vent the internal pressure. Without vents the internal pressure would build uncontrolled, until the planet exploded. Plate tectonics also means that there is an active core. An active core like the Earth’s creates a protective electro-magnetic field. The size of the field is important- too small and the solar winds blow it away; too large and life is a no-no. Volcanoes are part of the mineral recycling process. Volcanic ash also covers the ground, not only providing rich soil for future generations but also in some cases creating a time vault that enables scientists to get an excellent view of the past. To support plate tectonics a crust that is thick enough to support oceans and continents is required, but it can’t be so thick that it doesn’t have subducting plates to recycle vital minerals.
The laws that govern nature are independent of the constants that control them. IOW fudge with the constants and even though the outcome is changed, the law still remains true. And that change will, in all likely-hood, prevent the conditions required for complex life.
Did we win the “cosmic lottery”? Or is intentional design, design with the purpose of having said design be understandable and ensuring beings exist that can grow to understand it, the better explanation?
See also:
The Privileged Planet
ID vs. sheer dumb luck- You decide.
Factors for complex life:
1. Liquid water
a. Enough surface water to help regulate the planet’s temperature
b. Good solvent
c. Transports minerals
d. The presence of liquid water means the planet is in the habitable zone of it’s local star (Sun)
e. The presence of liquid water defines the CHZ (Circumstellar Habitable Zone. The CHZ of our solar system lies between Venus & Mars. Some scientists have narrowed it to:
-If the Earth were 5% closer to the Sun – too hot, no liquid water
-If the Earth were 20% father away from the Sun- too cold carbon dioxide would build up
2. Carbon based
a. Great bonding affinities
b. Allows for complex macro-molecules
3. Terrestrial planet
a. Crust thin/ thick and pliable enough to allow for plate tectonics
b. Recycling of minerals
c. Plate tectonics means the crust is sitting on an active core
d. Must retain enough heat for convection, i.e. keep the core liquid
e. Convection mixes the elements & shapes the continents
f. Active iron core is required to generate a protective magnetic field
g. Magnetic field has to be strong enough to withstand the solar winds
h. Must provide protection from radiation
4. Oxygen atmosphere
a. Our oxygen/ nitrogen mix is good
b. Clear- allows for good viewing
c. Ours is <1% of planet’s diameter
d. Allows in the right kind of light for viewing
5. Stable circular orbit
6. Large Moon (see also Gonzalez, G., “Wonderful Eclipses,” Astronomy & Geophysics 40, no. 3 (1999): 3.18- 3.20) (J. Laskar et al., “Stabilization of the Earth’s Obliquity by the Moon,” Nature 361 (1993): 615-17)
a. Our Moon is ¼ the size of Earth
b. Stabilizes the Earth’s axis of rotation
c. Gives our oceans a required tidal action
d. Just so happens that our Moon is 400x smaller than the Sun, which is 400x farther away
e. Both with a very circular shape
f. Allows for perfect solar eclipses
g. Confirmed Einstein’s prediction with the 1919 solar eclipse (gravity bends light) when scientists photographed the Stars behind it. We could have only made that discovery during a total solar eclipse.
h. Light spectrum
i. Observing & studying the Sun’s chromosphere is made possible
7. Gas Giants
a. Protection from intruding cosmic debris
b. Great for observing & scientific discovery
8. Sun- Spectral type G2 dwarf main sequence star-
a. If it were smaller the habitable zone would shrink and any planets in that zone would be locked into a synchronous orbit (rotation = revolution) as our Moon is with us
b. Total number estimated in the Milky Way- 100 billion
c. Over 80% are low-mass red dwarfs (most likely lack a habitable zone)
d. 1-2% are massive short-lived blue giants
e. Only about 4% of the stars are early G-type, main-sequence stars like our Sun
f. 50% of those are in binary systems
g. Then we have to consider what % of those are in the Galactic Habitable Zone
9. Location in the galaxy- Galactic Habitable Zone
a. We are between spiral arms
b. Perfect for viewing
c. Not a lot of activity
d. Not too close to the violent and very active center
e. More radiation near the center
Neighbors
Not a good viewing platform from which to discover
Not so far away where the heavy elements are scarce
10. Fine-tuning
a. Laws of Nature
b. Laws apply here also apply anywhere
c. Constants that are independent of those laws
Summary:
Within the Galactic Habitable Zone
Within the Circumstellar Habitable Zone
Liquid water
Orbit a Spectral type G2 dwarf main sequence star
Protected by gas giants
Nearly circular orbit-
Oxygen rich
Correct mass
Large moon to stabilize the angle of rotation
Moderate rate of rotation
Terrestrial planet
Ratio of water to continents
Plate tectonic re-cycling
Magnetic field
Both plate tectonics and the magnetic field require the core have enough heat to keep it liquid. The convection currents mix the minerals before recycling and also produce the required magnetic field as it flows around the iron inner core.
The Earth’s orbit is slightly elliptical. When the Earth is closest to the Sun (perigee) the southern hemisphere is enjoying summer, i.e. the Earth’s axis of rotation has the southern hemisphere at a better angle (than the northern hemisphere) towards the Sun for absorbing its vital rays. The Earth has the bulk of its continents in the northern hemisphere. Water stores the heat and then transfers it around the globe.
The above list contains factors required for complex life, but life is not guaranteed to arise even if all factors are met. The fact that a large, stabilizing moon is required and ours just happens to provide us with a huge natural setting in which we can & have conducted a multitude of scientific experiments that have increased our knowledge base and confirmed scientific predictions, is just the tip of the iceberg when it comes to evidence to support their finding that habitability = measure-ability. Think about it. In the accepted age view of the solar system & Earth, with the Moon’s recession rate coupled with the Sun’s expansion rate, these perfect solar eclipses, along with the scientific discoveries that accompany them, will soon be gone (10 million years). The best place for viewing eclipses, is also the only place in the solar system with perfect solar eclipses, is also the only place with conscious observers and we, intelligent observers, just happened to arrive when the scenario was best for scientific discovery.
Earthquakes, even though very destructive, are a necessary byproduct of the required plate tectonic recycling. They also offer us a way to measure the density of the material between designated points via the sound waves produced by plate movement. Volcanoes offer a way to vent the internal pressure. Without vents the internal pressure would build uncontrolled, until the planet exploded. Plate tectonics also means that there is an active core. An active core like the Earth’s creates a protective electro-magnetic field. The size of the field is important- too small and the solar winds blow it away; too large and life is a no-no. Volcanoes are part of the mineral recycling process. Volcanic ash also covers the ground, not only providing rich soil for future generations but also in some cases creating a time vault that enables scientists to get an excellent view of the past. To support plate tectonics a crust that is thick enough to support oceans and continents is required, but it can’t be so thick that it doesn’t have subducting plates to recycle vital minerals.
The laws that govern nature are independent of the constants that control them. IOW fudge with the constants and even though the outcome is changed, the law still remains true. And that change will, in all likely-hood, prevent the conditions required for complex life.
Did we win the “cosmic lottery”? Or is intentional design, design with the purpose of having said design be understandable and ensuring beings exist that can grow to understand it, the better explanation?
See also:
The Privileged Planet
52 Comments:
At 12:22 AM,
Zachriel said…
Well, with a hundred billion tickets (stars in the Milky Way), it's not so hard to win the lottery. Your list of coincidences just aren't that extraordinary. In any case, it would be hard to turn that into a valid scientific hypothesis, meaning a tentative and falsifiable assertion that would have empirical consequences. I mean what would the puddle think?
Douglas Adams: A puddle wakes up one morning and thinks to itself, 'This is an interesting world I find myself in, an interesting hole I find myself in, fits me rather neatly, doesn't it? In fact it fits me staggeringly well, must have been made to have me in it!'
At 7:40 AM,
Joe G said…
When puddles can "wake up and think" you may have a point. However all you are doing now is showing how desperate your anti-ID position is. Thanks again.
Zach:
Well, with a hundred billion tickets (stars in the Milky Way), it's not so hard to win the lottery.
Actually it is- because of the number of factors required. After the factors required are considered the number of stars is dwarfed by the fraction made up by the factors.
Conservative figures puts the calculation @ 100,000,000,000 (stars) x 1/1,000,000,000,000,000,000,000(factors)
Zach:
Your list of coincidences just aren't that extraordinary.
Science demonstrates they are extraordinary.
ZAch:
In any case, it would be hard to turn that into a valid scientific hypothesis, meaning a tentative and falsifiable assertion that would have empirical consequences.
It has been turned into valid science- it makes predictions, predictions that can be tested, confirmed or falsified.
Oh yeah and it is all based on peer-reviewed scientific research.
At 8:56 AM,
Joe G said…
Breaking it down:
100,000,000,000 stars
x fraction of of stars that are early G dwarfs and at least a few billion years old
x fraction of remaining stars in the GHZ
x fraction of remaining stars near the corotation circle and with low eccentricity galactic orbits
x fraction of remaining stars outside spiral arms
x fraction of remaining stars with at least one terrestrial planet in the CHZ
and then we get to planets. and not just any planet will do. It has to be the correct size. It has to have surface water. It has to have a very hot liquid iron core. The core has to be spinning. The planet must be rotating. Its axis of rotation must be stable (presence of a large moon will do this) The planet's crust must be thin enough to allow for plate tectonics. Then there is the atmosphere.
Oh just so you know- these factors were derived by scientists working for NASA assigned to find out what it takes to have life. And if they are right we now know where to look - the best possibilities. Also as I said "Rare Earth" came to closely the same conclusions- that Earth and our solar system are rare. The authors of that book are not IDists.
At 10:28 AM,
Zachriel said…
joe g: "Conservative figures puts the calculation @ 100,000,000,000 (stars) x 1/1,000,000,000,000,000,000,000(factors)"
As if you could make such a calculation.
Gee. I just dealt a hand of bridge. You should see the layout of the cards. What are the odds? (About one in 10^68.)
joe g: "Oh just so you know- these factors were derived by scientists working for NASA assigned to find out what it takes to have life."
What is really odd is how you keep citing those who disagree with you.
NASA: We don't know whether or not there is other intelligent life in the universe. There is no reason there shouldn't be. We know by our own existence that the universe is conducive to life.
At 10:55 AM,
Zachriel said…
joe g: "Also as I said "Rare Earth" came to closely the same conclusions"
Ward and Brownlee assert that life is common, but ETI (extra terrestrial intelligence) is rare. Ward and Brownlee's hypothesis is not that the Earth is unique. In fact, they believe that ETI is probable, but believe it to be rare enough as to leave humans essentially isolated by space and time. Not all scientists accept their conclusions, but there is just not enough data to reach any firm conclusions.
At 11:02 AM,
Zachriel said…
Peter Ward, author of 'Rare Earth': "Maybe we have between ten and a hundred within our one hundred thousand light year wide galaxy, we’d [be] lucky. And once they're spaced out, once we have so few, the possibility of talking to them is low."
At 11:22 AM,
Joe G said…
joe g: "Conservative figures puts the calculation @ 100,000,000,000 (stars) x 1/1,000,000,000,000,000,000,000(factors)"
Zach:
As if you could make such a calculation.
It's been made by the scientists doing the research.
joe g: "Oh just so you know- these factors were derived by scientists working for NASA assigned to find out what it takes to have life."
Zach:
What is really odd is how you keep citing those who disagree with you.
I go with the data.
Zach:
NASA: We don't know whether or not there is other intelligent life in the universe. There is no reason there shouldn't be. We know by our own existence that the universe is conducive to life.
You miss the point. Obviously you have issues with reading and reading comprehension.
In an ID scenario we would expect more complex and intelligent life. However in a "sheer dumb luck" scenario (the anti-ID position) getting ALL of the factors in one place and time makes life a lot less likely, if not impossible.
And again the scientific research that is behind the factors and the calculations were made by scientists doing the research for the NASA program.
At 11:25 AM,
Joe G said…
This is too funny:
Peter Ward, author of 'Rare Earth': "Maybe we have between ten and a hundred within our one hundred thousand light year wide galaxy, we’d [be] lucky. And once they're spaced out, once we have so few, the possibility of talking to them is low."
Yeah that's scientific- "Maybe we have..."
Yeah Pete, maybe we don't. By the looks of the data, we don't.
At 11:28 AM,
Joe G said…
And this is funny:
Zach:
joe g: "Also as I said "Rare Earth" came to closely the same conclusions"
Ward and Brownlee assert that life is common, but ETI (extra terrestrial intelligence) is rare.
They can assertall they want. They don't have any data to support their assertion.
Zach:
Ward and Brownlee's hypothesis is not that the Earth is unique.
It doesn't have to be unique to be rare.
Zach:
In fact, they believe that ETI is probable, but believe it to be rare enough as to leave humans essentially isolated by space and time. Not all scientists accept their conclusions, but there is just not enough data to reach any firm conclusions.
Reality demonstrates we have plenty of data to make an informed scientific inference.
You should read the book instead of arguing from ignorance.
At 1:45 PM,
Zachriel said…
joe g: "Yeah that's scientific- 'Maybe we have...'"
It's your own cited authority.
However, as the probabilities are based on very limited knowledge and a wide range of plausible values, a "Maybe" is appropriate.
joe g: "They don't have any data to support their assertion."
It's your own cited authority.
However, they are working with the limited available data and attempting a reasonable extrapolation.
joe g: "It doesn't have to be unique to be rare."
Quite true. But if there are hundreds of such winners in each of the billions of galaxies, then the supposed luck is merely due to the limited perspective of the observer.
joe g: "Reality demonstrates we have plenty of data to make an informed scientific inference."
You just said, "They don't have any data to support their assertion."
Your cited authority calls it hypothesis based on very limited information. For instance, they support SETI, and they surely support continued scientific investigation.
At 8:49 AM,
Joe G said…
joe g: "Yeah that's scientific- 'Maybe we have...'"
Zach:
It's your own cited authority.
However, as the probabilities are based on very limited knowledge and a wide range of plausible values, a "Maybe" is appropriate.
It doesn't matter who you claim it is, "maybe" is not scientific and is not based on any real data.
joe g: "They don't have any data to support their assertion."
Zach:
It's your own cited authority.
When they start talking out of their arse, as opposed to following the data, they aren't anyone's authority.
Zach:
However, they are working with the limited available data and attempting a reasonable extrapolation.
But there isn't ANY data that would demonstrate microbial life is common in the universe.
joe g: "It doesn't have to be unique to be rare."
Zach:
Quite true. But if there are hundreds of such winners in each of the billions of galaxies, then the supposed luck is merely due to the limited perspective of the observer.
If pigs had wings could they fly?
joe g: "Reality demonstrates we have plenty of data to make an informed scientific inference."
Zach:
You just said, "They don't have any data to support their assertion."
That was pertaining to Ward & Brownlee and their assertion that microbial life is common. "TPP" came after "Rare Earth" and as such had more scientific data to work with.
Ya see Gonzalez was part of a NASA research team. And it was the data collected by that team that went into the book.
It still remains- ALL of the factors mentioned in my OP have to be in the same place at the sametime just to sustain life. The factors do NOT gauratee life will arise.
Heck just look at our solar system. There isn't another habitable planet or moon in it. And the extra-solar planets discovered thus far just show more of that.
At 11:07 AM,
Zachriel said…
joe g: "It doesn't matter who you claim it is"
Are you trying self-parody? It's your cite!
joe g: "But there isn't ANY data that would demonstrate microbial life is common in the universe."
The existence of extraterrestrial life is still an open question, however, there is substantial evidence that it may be common based on the Principle of Mediocrity. We can support the application of this principle with some basic observations.
* Life exists on at least one planet.
* Life is based on carbon and liquid water.
* Carbon and water are common in the visible universe.
* Organic compounds readily form under a variety of conditions.
* The Sun is a star.
* There are hundreds of billions of stars.
* There are planets around some stars.
* Some planets likely have liquid water.
You cited NASA, again. NASA: We don't know whether or not there is other intelligent life in the universe. There is no reason there shouldn't be. We know by our own existence that the universe is conducive to life.
At 5:30 PM,
Richard H said…
Joe - probabilities work both ways.....
If you argue that the chance of life appearing on earth is less likely than design then you have to also accept that the designer is more likely to be natural than supernatural.
On the specific subject of the probability of life being designed versus evolved let takes a simple analogy.....
Everyone on the planet gets given 20 numbers for a one-off lottery and 1 lucky person wins the jackpot. A number of years later someone wonders if the lottery might have been fixed (designed for this person to win) and they start looking into it. They calculate the probabilities of that person winning the lottery and concludes the odds are so small that that person must have won by design.
You must see the error in this assumption. People win the lottery every week, even though the probabilities of them winning are small. It doesn't matter how small the probabilities are - the point is it is possible.
To claim that this view is a desperate anti-ID position says more about your understanding of probabilities and you are doing the anti-ID people a huge favour with such a blog.
For the record I believe it is highly possible that life on earth has been designed, but I find it highly improbable that the design was by a supernatural being. However, I also believe it is possible that we have infact evolved on this planet. Probabilities, no matter how small the odds do not make something impossible.
Do you believe that it is impossible for life to have started on earth naturally or just unlikely? If impossible then the discussion is over as you clearly have a view based on something other than probabilities. If unlikely, then you have to accept that evolution is possible.
At 6:08 PM,
Raevmo said…
Actually, the jury is still out on other (primitive) live in the solar system. For example, there is some evidence that there might be life on Mars (which used to warmer because the sun used to be hotter), and there might be life on some of the moons of the giant planets.
Within a few decades we'll probably know for sure.
In general, without going into a detailed rebuttal, I would say your list of necessary conditions is too restrictive because it focusses on life as WE know it.
At 8:57 AM,
Joe G said…
Lol!
joe g: "But there isn't ANY data that would demonstrate microbial life is common in the universe."
Zach:
The existence of extraterrestrial life is still an open question, however, there is substantial evidence that it may be common based on the Principle of Mediocrity. We can support the application of this principle with some basic observations.
Umm, you should read "The Privileged Planet". It thoroughly refutes the principle of mediocrity.
Zach:
* Life exists on at least one planet.
Yes it does. But HOW it came to exist on this planet is still an open question. And scienbce tells us only life begets life.
Zach:
* Life is based on carbon and liquid water.
LoL! Life is based on more than that. True without carbon or water we wouldn't have life...
Zach:
* The Sun is a star.
Our Sun is a special type of star. Only 4% of the stars in our galaxy are like our Sun. Oh yeah- the scientific data demonstrates any habitable planet has to have a Sun like ours.
ZAch:
* There are hundreds of billions of stars.
Again try following along:
Breaking it down:
100,000,000,000 stars
x fraction of of stars that are early G dwarfs and at least a few billion years old
x fraction of remaining stars in the GHZ
x fraction of remaining stars near the corotation circle and with low eccentricity galactic orbits
x fraction of remaining stars outside spiral arms
x fraction of remaining stars with at least one terrestrial planet in the CHZ
Zach:
* There are planets around some stars.
All the planets we know of have either the wrong orbit or are gas giants not conducive for life.
ZAch:
* Some planets likely have liquid water.
Life is more than "just add water" and life is more than organic compounds.
BTW I already responded to your NASA quote-mine.
But here it is again:
You miss the point. Obviously you have issues with reading and reading comprehension.
In an ID scenario we would expect more complex and intelligent life. However in a "sheer dumb luck" scenario (the anti-ID position) getting ALL of the factors in one place and time makes life a lot less likely, if not impossible.
And again the scientific research that is behind the factors and the calculations were made by scientists doing the research for the NASA program.
At 9:10 AM,
Joe G said…
Richard H:
If you argue that the chance of life appearing on earth is less likely than design then you have to also accept that the designer is more likely to be natural than supernatural.
That is irrelevant. The debate is NOT super natural vs. natural. The debate is intelligent, directed (goal oriented) processes vs. unintelligent, blind/ undirected (non-goal oriented) processes. The reason is, as I have stated in many of my posts, is that it ALL comes down to something non or super natural because the origin of nature could NOT have come about via natural proceses because natural processes only exist IN nature.
Also the probabilities were calculated by SCIENTISTS! Scientists doing the research. So it appears you argument is with them.
Did you read the book or watch the video? Your lottery analogy is taken care of...
Richard H:
For the record I believe it is highly possible that life on earth has been designed, but I find it highly improbable that the design was by a supernatural being.
ID doesn't say anything about the supernatural.
Richard H:
However, I also believe it is possible that we have infact evolved on this planet.
Evolved from what? The only scientific data we have pertaining to life is that only life begets life.
Richard H:
Probabilities, no matter how small the odds do not make something impossible.
Extraordinary claims (like those trying to buck the odds) require extraordinary data (evidence).
Richard H:
Do you believe that it is impossible for life to have started on earth naturally or just unlikely?
Bogus question as both intelligence and design are natural. However I do accept that science will determine that life could never have arisen via unintelligent, blind/ undirected (non-goal oriented) processes.
Anything may be possible Richard. And that is where the data comes in.
At 9:27 AM,
Joe G said…
Raevmo:
In general, without going into a detailed rebuttal, I would say your list of necessary conditions is too restrictive because it focusses on life as WE know it.
The scientific research demonstrates that all life will be "as we know it". Perhaps with minor variations but we have a very wide range of life to look at on this planet. The laws of nature that apply here also apply everywhere in the universe.
Again all the data was compiled by scientists doing scientific research. So I don't know if you guys have an issue with science or what?
At 10:31 AM,
Richard H said…
Joe, thank you for your response.
I wish you well on your journey to find evidence of Intelligent Design.
At 10:31 AM,
Joe G said…
To re-iterate:
100,000,000,000 stars
x fraction of of stars that are early G dwarfs and at least a few billion years old
x fraction of remaining stars in the GHZ
x fraction of remaining stars near the corotation circle and with low eccentricity galactic orbits
x fraction of remaining stars outside spiral arms
x fraction of remaining stars with at least one terrestrial planet in the CHZ
and then we get to planets:
* Not just any planet will do.
* It has to be the correct size.
* It has to have surface water.
* It has to have a very hot liquid iron core.
* The core has to be spinning.
* The planet must be rotating.
* Its axis of rotation must be stable (presence of a large moon will do this)
* The planet's crust must be thin enough to allow for plate tectonics.
* Then there is the atmosphere.
Oh just so you know- these factors were derived by scientists working for NASA assigned to find out what it takes to have life. And if they are right we now know where to look - the best possibilities. Also as I said "Rare Earth" came to closely the same conclusions- that Earth and our solar system are rare. The authors of that book are not IDists.
(btw as ANYONE can see I cite "Rare Earth" not for the "maybe's" it contains pertaining to microbial life, rather I cite it for also demonstrating the Earth and solar system are indeed rare.)
The large moon is an interesting issue. The anti-ID consensus has the Earth-Moon system forming via a giant impact. But without a large moon science tells us the Earth's axis of rotation wouldn't be stable. Earth would wobble too much for a stable environment. Some say that impact also started our rotation period.
You guys should really read the book or at least watch the video in order to get an idea of the scientific data behind it.
At 5:01 PM,
Zachriel said…
joe g: "It thoroughly refutes the principle of mediocrity."
You can't "refute" it, only its particular application.
joe g: "Breaking it down:"
You forgot to include the breakdown. That would seem to be important when making a mathematical argument.
joe g: "And again the scientific research that is behind the factors and the calculations were made by scientists doing the research for the NASA program."
And for some odd reason, the people you rely on for the data and calculations do not accept your conclusions.
joe g: "The only scientific data we have pertaining to life is that only life begets life."
That is incorrect. It is known that the Earth was once barren, then became populated with primitive microorganisms. We also know that certain molecules are self-replicating. Though there is no complete theory of abiogenesis, all known life is based in carbon chemistry.
At 6:24 PM,
Zachriel said…
joe g: "Also as I said "Rare Earth" came to closely the same conclusions- that Earth and our solar system are rare. The authors of that book are not IDists."
From the author of your cite concerning intelligent life:
Peter Ward: "Maybe we have between ten and a hundred within our one hundred thousand light year wide galaxy, we’d [be] lucky. And once they're spaced out, once we have so few, the possibility of talking to them is low."
joe g: "(btw as ANYONE can see I cite "Rare Earth" not for the "maybe's" it contains pertaining to microbial life, rather I cite it for also demonstrating the Earth and solar system are indeed rare.) "
And I quoted the author concerning his informed opinion on *intelligent life*. The Earth is not 'rare', but an 'instance'. The evidence indicates that the processes on Earth that led to life are not unique in the universe.
At 6:56 PM,
Raevmo said…
Joe said:
"The scientific research demonstrates that all life will be "as we know it". Perhaps with minor variations but we have a very wide range of life to look at on this planet. The laws of nature that apply here also apply everywhere in the universe.
Again all the data was compiled by scientists doing scientific research. So I don't know if you guys have an issue with science or what?"
How could it be demonstrated that only "life as we know it" (or a minor variation thereof) is possible? The imagination of the human mind is constrained by human experience. You criticize the scientific methods of evolutionary biologists when their conclusions do not fit your preconceived notions, but when scientists make outragious claims that you happened to like, then you are suddenly a lot less critical. There is a lot of crappy science out there (such as the science you so happily quote in your post). It takes critical analysis to weed out the rubbish.
At 9:30 AM,
Joe G said…
joe g: "It thoroughly refutes the principle of mediocrity."
Zach:
You can't "refute" it, only its particular application.
Its particular application has been refuted.
joe g: "And again the scientific research that is behind the factors and the calculations were made by scientists doing the research for the NASA program."
Zach:
And for some odd reason, the people you rely on for the data and calculations do not accept your conclusions.
Spoken like someone arguing from ignorance. TRy reading "The Privileged Planet" and then try to post the same response. You couldn't do it without lying- but I know you wouldn't let that stop you.
joe g: "The only scientific data we have pertaining to life is that only life begets life."
Zach:
That is incorrect.
Reality demonstrates I am very correct. IOW there isn't ANY data that demonstrates that non-living matter can give rise to life. Zero- bnon- nada.
ZAch:
It is known that the Earth was once barren, then became populated with primitive microorganisms.
LoL! HOW, Zach- HOW did the Earth become populated with anything? Think man!
ZAch:
We also know that certain molecules are self-replicating.
The stuff of life is much more than merely "self-replicating".
Leslie Orgel tells us, “Living organisms are distinguished by their specified complexity. Crystals… fail to qualify as living because they lack complexity; mixtures of random polymers fail to qualify because they lack specificity.”
Zach:
Though there is no complete theory of abiogenesis, all known life is based in carbon chemistry.
Without information carbon chemistry would never give rise to life.
At 9:41 AM,
Joe G said…
Raevmo asks:
How could it be demonstrated that only "life as we know it" (or a minor variation thereof) is possible?
As I said the SAME laws that apply here apply every where in the universe.
Again it appears that your issue is with the scientists who did the research.
Raevmo:
You criticize the scientific methods of evolutionary biologists when their conclusions do not fit your preconceived notions,
That is false. I do not challenge any "conclusions" based on a sound application of scientific methodology.
Raevmo:
but when scientists make outragious claims that you happened to like, then you are suddenly a lot less critical.
What you call an "outrageous claim" is really a scientific prediction which can be either confirmed or falsified with further research and data.
Raevmo:
There is a lot of crappy science out there (such as the science you so happily quote in your post).
The science I quote in my post is backed by the scientific data. The crap evolutionism spews is backed by philosophical nonsense.
Raevmo:
It takes critical analysis to weed out the rubbish.
And thanks to critical analysis I am no longer an evolutionist.
Unified physics theory explains animals' running, flying and swimming
"Our finding that animal locomotion adheres to constructal theory tells us that -- even though you couldn't predict exactly what animals would look like if you started evolution over on earth, or it happened on another planet -- with a given gravity and density of their tissues, the same basic patterns of their design would evolve again," Marden said.
At 9:43 AM,
Joe G said…
Richard H:
Joe, thank you for your response.
You're welcome
Richard H:
I wish you well on your journey to find evidence of Intelligent Design.
Thank you. However that evidence has been found and presented.
At 12:37 PM,
Joe G said…
joe g: "Also as I said "Rare Earth" came to closely the same conclusions- that Earth and our solar system are rare. The authors of that book are not IDists."
Zach:
From the author of your cite concerning intelligent life:
Peter Ward: "Maybe we have between ten and a hundred within our one hundred thousand light year wide galaxy, we’d [be] lucky. And once they're spaced out, once we have so few, the possibility of talking to them is low."
And again "Maybe..." is NOT based on scientific data.
The scientific data we do have demonstrates our solar system is atypical.
joe g: "(btw as ANYONE can see I cite "Rare Earth" not for the "maybe's" it contains pertaining to microbial life, rather I cite it for also demonstrating the Earth and solar system are indeed rare.) "
Zach:
And I quoted the author concerning his informed opinion on *intelligent life*.
Perhaps you should do some research instead of quote mining.
Zach:
The Earth is not 'rare', but an 'instance'.
That goes against the title of the book as well as its contents.
Zach:
The evidence indicates that the processes on Earth that led to life are not unique in the universe.
What EVIDENCE? We don't know what processes on Earth that led to life! We do know what it takes to sustain complex life. And the data demonstrates getting all the factors required, just to sustain complex life, together in one place and at the same time, would be an extraordinary event. As such, your scenario of "sheer dumb luck" just doesn't cut it.
BTW with the scientific data we do have we can assign very reasonable numbers to all the factors.
At 1:48 PM,
Zachriel said…
joe g: "Spoken like someone arguing from ignorance.""
It is always possible to find someone with a contrary view. Gonzalez is a minority view. In addition, he is an astronomer, not a biologist. The consensus scientific opinion and the consensus opinion of all major scientific institutions is that intelligent design is not science.
When an appeal is made to authority — as you have done, then the authority should be representing the consensus view of his profession and the expertise in the relevant field of study. The proper response to an appeal to authority is the evidence. I have not found Gonzalez's arguments scientifically persuasive. They are based in puddle-logic.
joe g: "We don't know what processes on Earth that led to life!"
That's largely correct. It won't stop your from drawing absolute conclusions though.
joe g: "BTW with the scientific data we do have we can assign very reasonable numbers to all the factors."
But instead of numbers, you waved your hands.
At 9:35 AM,
Joe G said…
joe g: "Spoken like someone arguing from ignorance.""
Zach:
It is always possible to find someone with a contrary view. Gonzalez is a minority view. In addition, he is an astronomer, not a biologist.
Umm Gonzalez is an astrobiologist. And most inferences start off as a minority view.
Zach:
The consensus scientific opinion and the consensus opinion of all major scientific institutions is that intelligent design is not science.
I would bet that consensus doesn't understand the first thing about ID. From what I have read that the "consensus" has written it is obvious that they are clueless when it comes to ID.
Zach:
When an appeal is made to authority — as you have done,
I am appealing to the DATA.
Zach:
The proper response to an appeal to authority is the evidence. I have not found Gonzalez's arguments scientifically persuasive.
You haven't even read the book! You haven't even demonstrated you grasp the data!
joe g: "We don't know what processes on Earth that led to life!"
Zach:
That's largely correct. It won't stop your from drawing absolute conclusions though.
I draw an inference Zach. An inference based on the scientific data we do have.
joe g: "BTW with the scientific data we do have we can assign very reasonable numbers to all the factors."
Zach:
But instead of numbers, you waved your hands.
I gave the numbers-
Conservative figures puts the calculation @ 100,000,000,000 (stars) x 1/1,000,000,000,000,000,000,000(factors)
That was from assigning a very conservative 1/10 to each factor. WE know that is conservative from the scientific data.
It appears all Zach can do is to argue from ignorance and personal incredulity- IOW he just can't believe the data.
At 11:15 AM,
Zachriel said…
joe g: "That was from assigning a very conservative 1/10 to each factor."
Claims that the planet must be the "correct size" or be in a certain part of the galaxy, or have a magnetic core, or have plate tectonics, may not be valid assumptions.
Many of those characteristics may be linked, hence your "calculation" may be faulty. And giving each characteristics the exact same percentage shows a lack of actual data.
It's called handwaving. It might be interesting, but it hardly constitues a firm scientific inference.
At 7:01 PM,
Raevmo said…
Joe,
Scientists usually put some estimate of the degree of uncertainty on their estimates. Like estimate = mean +/- standard error. That gives one an idea about the accuracy of the estimate. How does that compute with your product of many factors? It seems to me that the 95% confidence interval is between 0 and infinity.
At 9:40 AM,
Joe G said…
joe g: "That was from assigning a very conservative 1/10 to each factor."
Zach:
Claims that the planet must be the "correct size" or be in a certain part of the galaxy, or have a magnetic core, or have plate tectonics, may not be valid assumptions.
By what data? If a planet is too small the solar winds WILL strip away its magnetic field (if it had one). Without plate tectonics the planet will require another way to recycle its materials, especially its CO2.
G. Gonzalez, D. Brownlee, and P.D. Ward, “The Galactic Habitable Zone: Galactic Chemical Evolution”, Icarus 152 (2001):185-200)
Zach read the freakin' book. Your continued argument from ignorance is more than annoying.
At 9:51 AM,
Joe G said…
BTW Zach,
Most of the factors are much less than 10%- according to the book. I just gave it 10% for ease of calculation- IOW just so you could see what you are up against.
The factor for a large moon, for example, is estimated at 0.001%. Given the current consensus of how our Earth-Moon system formed that is more than generous.
However you guys could falsify the premise by demonstrating these factors are not required. But you have to stop your flailing and actually do some research.
It would be interesting to observe a planet with an active core that didn't have plate tectonics. It would be even more interesting to see a terrestrial planet without an active core but with a strong protective magnetic field.
At 10:06 AM,
Zachriel said…
joe g: "The factor for a large moon, for example, is estimated at 0.001%."
But there is no reason to suppose that a large moon is required. It is a supposition based upon the unique history of Earth. The same with the majority of the other so-called essential conditions.
joe g: "However you guys could falsify the premise by demonstrating these factors are not required."
Strawman. An assertion is claimed to be scientific, but the presumed falsification is to be provided by others and to be found someplace that is inaccessible.
"The Privileged Planet" is a typical argument from ignorance dressed up in the language of science. Puddle-logic.
At 10:38 AM,
Joe G said…
Galactic Habitable Zone
From the first link:
Known as the Galactic Habitable Zone, it is an area of space whose boundaries are set by its calm and safe environment, and access to the chemical materials necessary for building terrestrial planets similar to the Earth.
"Our Milky Way galaxy is home to hundreds of billions of stars, but until recently, astronomers could only guess as to how many are hospitable for the development of complex life. What we have done for the first time is to quantify carefully where complex life is likely to exist," Lineweaver said.
"Even if a star can build and sustain an Earth-like planet, there are numerous cosmic threats to life. They include impacts from comets and asteroids, devastating bursts of energy from supernovae, close encounters with passing stars, and outbursts from the super-massive black hole at the core of the Galaxy," he said.
At 10:46 AM,
Joe G said…
And another interseting article:
The locked migration of giant protoplanets
At 10:52 AM,
Joe G said…
joe g: "The factor for a large moon, for example, is estimated at 0.001%."
Zach:
But there is no reason to suppose that a large moon is required.
Not only is that the scientific consensus- that a large moon is required- I provided the peer-reviewed article that tells us why!
J. Laskar et al., “Stabilization of the Earth’s Obliquity by the Moon,” Nature 361 (1993): 615-17
Leave it to Zach to totally ignore the scientific data.
joe g: "However you guys could falsify the premise by demonstrating these factors are not required."
Zach:
Strawman.
Why is it a strawman? Just because you can't do it? LoL!
At 1:45 PM,
Zachriel said…
Zachriel: But there is no reason to suppose that a large moon is required.
joe g: "Not only is that the scientific consensus- that a large moon is required- I provided the peer-reviewed article that tells us why!"
The article explains that a large moon reduces certain chaotic tendencies in axial obliquity. That doesn't mean that life couldn't evolve otherwise, or that other factors can also create suitable conditions, or that this is just a matter of self-selection (puddle-logic).
In fact, the planetary system is inherently chaotic over the long run.
At 4:59 PM,
Raevmo said…
Update on scientific evidence, from Williams & Kasting (1997), Icarus 129:
"We conclude that a significant fraction of extrasolar Earth-like planets may still be habitable, even if they are subject to large obliquity fluctuations."
So it would appear that the factor for a large moon is orders of magnitude larger than 0.001%.
At 7:00 PM,
Joe G said…
Raevmo:
Update on scientific evidence, from Williams & Kasting (1997), Icarus 129:
"We conclude that a significant fraction of extrasolar Earth-like planets may still be habitable, even if they are subject to large obliquity fluctuations."
That depends. Are they talking about an already existing and advanced technological civilization going to one of those planets and inhabiting it- making parts of it habitable because of their technology? Or are they talking about indigenous organisms? And then what level of organisms?
Ya see the factors discussed in my OP are for Complex life- air breathing metazoans and apply to indigenous organisms.
Raevmo:
So it would appear that the factor for a large moon is orders of magnitude larger than 0.001%.
Very doubtful. Our Moon is also responsible for the tides (although tides of a sort would still exist without one), as well as climate control:
C. Wunsch, "Moon, Tides and Climate", Nature 405 (2000): 744
See also
D.M. Miller and D. Pollard, "Earth-Moon Interactions: Implications for Terrestrial Climate and Life" Origin of the Earth and Moon, R.M. Canup and K. Brighter eds. (Tuscon: Univ. of Arizona Press, 2000), 513-525
Also we mustn't forget that the consensus who sez the Earth-Moon system formed via collision tell us it is that collision that gave us the rotation period we have. No collision no or little rotation. Which would be even more problematic for life.
And without that collision the Earth's crust would be too thick to support plate tectonic recycling.
At 7:35 PM,
Joe G said…
joe g: "Not only is that the scientific consensus- that a large moon is required- I provided the peer-reviewed article that tells us why!"
Zach:
The article explains that a large moon reduces certain chaotic tendencies in axial obliquity. That doesn't mean that life couldn't evolve otherwise, or that other factors can also create suitable conditions, or that this is just a matter of self-selection (puddle-logic).
First the alleged "puddle-logic" is no such thing- as already explained. That you keep using it just demonstrates your lack of grasp on reality.
Secondly see my response to Raevmo:
Our Moon is also responsible for the tides (although tides of a sort would still exist without one), as well as climate control:
C. Wunsch, "Moon, Tides and Climate", Nature 405 (2000): 744
See also
D.M. Miller and D. Pollard, "Earth-Moon Interactions: Implications for Terrestrial Climate and Life" Origin of the Earth and Moon, R.M. Canup and K. Brighter eds. (Tuscon: Univ. of Arizona Press, 2000), 513-525
Also we mustn't forget that the consensus who sez the Earth-Moon system formed via collision tell us it is that collision that gave us the rotation period we have. No collision no or little rotation. Which would be even more problematic for life.
And without that collision the Earth's crust would be too thick to support plate tectonic recycling.
Bottom-line No Large Moon, No Life- for all the reasons listed.
You guys really should brush up on astronomy and astrophysics.
At 8:11 PM,
Zachriel said…
joe g: "Bottom-line No Large Moon, No Life- for all the reasons listed."
You haven't listed any reasons. All you have is a lack of imagination and vague numerology substituting for evidence.
joe g: "Again all the data was compiled by scientists doing scientific research. So I don't know if you guys have an issue with science or what?"
And the majority of scientists reject your assertions.
joe g: "Oh just so you know- these factors were derived by scientists working for NASA assigned to find out what it takes to have life."
NASA: We don't know whether or not there is other intelligent life in the universe. There is no reason there shouldn't be. We know by our own existence that the universe is conducive to life.
At 8:22 PM,
Raevmo said…
I took your advise Joe, and brushed up a bit on the recent scientific literature. Here's from Gaidos et al. (2005), Astrobiology 5, pp 100-126:
"The recent work reviewed
here suggests that: (1) Earth-size planets will commonly form in the HZ of solar-type stars, (2) many of these planets will experience active geologic re-surfacing at some point during their history, (3) a large fraction of them will have an initial water inventory equal to or larger than the
Earth, and (4) the abundance of carbon and nitrogen may vary markedly among these planets.
What is not understood is how synergisms between these factors affect habitability. Simulating
the dynamics and evolution of a habitable planet is a daunting task (Meadows et al., 2001), and significant progress may have to wait until we have more than one example of a habitable planet."
On the one hand it suggests that suitable planets may not be that rare. On the other hand, it also cautions that there is still a great deal of uncertainty.
In other words, Joe, the "calculations" you present should be consumed with a large dose of salt. Be a sport and admit it.
At 9:18 PM,
Joe G said…
joe g: "Bottom-line No Large Moon, No Life- for all the reasons listed."
Zach:
You haven't listed any reasons.
I listed several. That you can't understand them is not my problem.
Zach:
All you have is a lack of imagination and vague numerology substituting for evidence.
Imagination is not a substitute for scientific data. And it appears all you have is an imagination with one focus.
joe g: "Again all the data was compiled by scientists doing scientific research. So I don't know if you guys have an issue with science or what?"
Zach:
And the majority of scientists reject your assertions.
What assertions?
joe g: "Oh just so you know- these factors were derived by scientists working for NASA assigned to find out what it takes to have life."
Zach the broken record:
NASA: We don't know whether or not there is other intelligent life in the universe. There is no reason there shouldn't be. We know by our own existence that the universe is conducive to life.
You miss the point. Obviously you have issues with reading and reading comprehension.
In an ID scenario we would expect more complex and intelligent life. However in a "sheer dumb luck" scenario (the anti-ID position) getting ALL of the factors in one place and time makes life a lot less likely, if not impossible.
And again the scientific research that is behind the factors and the calculations were made by scientists doing the research for the NASA program.
IOW the NASA quote-mine is meaningless and just another example of your desparation.
Bottom-line- No Moon- No proto-Earth/ other large body collision- no rotation period. One side always facing the Sun- very hot-> no surface water-> other side frozen
No Moon- No tides that would mix the elements and transport nutrients.
No Moon- No life- unless seeded by an adavanced civilization.
At 9:58 PM,
Joe G said…
Thanks Raevmo. Could you cite the "recent reviewed here"- I am not shelling out $29 for that paper.
The paper I cited demonstrates that migrating gas giants would wipe out any terrestrial planets in their way into their sun.
Also under the design paradigm habitable planets may not be that rare. However given the "sheer dumb luck" scenario we would expect us to be it- at least in this galaxy, given all the relevant scientific data.
At 10:44 PM,
Zachriel said…
Raevmo: "On the one hand it suggests that suitable planets may not be that rare. On the other hand, it also cautions that there is still a great deal of uncertainty."
Excellent point. Gaido et. al. point out in their "review of terrestrial planet habitability", that "Such evidence provides us with an important, if nominal, calibration point for our search for other habitable worlds."
At 8:44 AM,
Raevmo said…
Here are the references in that Astrobiology paper:
Amelin, Y., Lee, D.C., Halliday, A.N., and Pidgeon, R.T.
(1999) Nature of the Earth’s earliest crust from hafnium
isotopes in single detrital zircons. Nature 399, 252–255.
Amelin, Y., Krot, A.N., Hutcheon, E.D., and Ulyanov,
A.A. (2002) Lead isotopic ages of chondrules and calcium-
aluminum-rich inclusions. Science 297, 1678–1683.
Anderson, O.L. and Isaak, D.G. (2002) Another look at the
core density of Earth’s outer core. Phys. Earth Planet. Interiors
131, 19–27.
Armitage, P.J. (2003) A reduced efficiency of terrestrial
planet formation following giant planet migration. Astrophys.
J. 582, L47–L50.
Arpigny, C., Jehin, E., Manfroid, J., Hutsemekers, D.,
Schulz, R., Stuwe, J.A., Zucconi, J.M., and Ilyin, I. (2003)
Anomalous nitrogen isotope ratio in comets. Science
301, 1522–1524.
Asimow, P.D. and Langmuir, C.H. (2003) The importance
of water to oceanic mantle melting regimes. Nature 421,
815–820.
Atobe, K., Ida, S., and Ito, T. (2004) Obliquity variations
of planets in habitable zones. Icarus 168, 223–236.
Balsiger, H., Altwegg, K., and Geiss, J. (1995) D/H and
O-18/O-16 ratio in the hydronium ion and in neutral
water from in situ ion measurements in comet Halley.
J. Geophys. Res. 100, 5827–5834.
Barbieri, M. and Marzari, F. (2002) Formation of terrestrial
planets in close binary systems: The case of Alpha
Centauri A. Astron. Astrophys. 396, 219–224.
Beichman, C.A., Coulter, D.R., Lindensmith, C., and Lawson,
P.R. (2002) Selected mission architectures for the
Terrestrial Planet Finder (TPF): Large, medium, and
small. Proc. SPIE 4835, 115–121.
Benest, D. (1988) Planetary orbits in the elliptic restricted
problem. I—The Alpha Centauri system. Astron. Astrophys.
206, 143–146.
Benest, D. (1989) Planetary orbits in the elliptic restricted
problem. II—The Sirius system. Astron. Astrophys. 223,
361–364.
Benest, D. (1996) Planetary orbits in the elliptic restricted
problem. III. The _ Coronae Borealis system. Astron. Astrophys.
314, 983–988.
Benest, D. (1998) Planetary orbits in the elliptic restricted
problem. IV. The ADS 12033 system. Astron. Astrophys.
332, 1147–1153.
Benest, D. (2003) Planetary orbits in the elliptic restricted
problem. V. The ADS 11060 system. Astron. Astrophys.
400, 1103–1111.
Boato, G. (1954) The isotopic composition of hydrogen
and carbon in the carbonaceous chondrites. Geochim.
Cosmochim. Acta 6, 209–220.
Bockelée-Morvan, D., Gautier, D., Lis, D.C., Young, K.,
Keene, J., Phillips, T., Owen, T., Crovisier, J., Goldsmith,
P.F., Bergin, E.A., Despois, D., and Wootten, A. (1998)
Deuterated water in comet C/1996 B2 (Hyakutake) and
its implications for the origin of comets. Icarus 133,
147–162.
Borucki, W.J., Koch, D.G., Lissauer, J.J., Basri, G.B., Caldwell,
J.F., Cochran, W.D., Dunham, E.W., Geary, J.C.,
Latham, D.W., Gilliland, R.L., Caldwell, D.A., Jenkins,
J.M., and Kondo, Y. (2003) The Kepler mission: A widefield-
of-view photometer designed to determine the
frequency of Earth-size planets around solar-like stars.
Proc. SPIE 4854, 129–140.
Boss, A. (1997) Giant planet formation by gravitational instability.
Science 276, 1836–1839.
Bounama, C. (2001) The fate of Earth’s ocean. Hydrol. Earth
System Sci. 5, 569–575.
Bowring, S.A. and Williams, I.S. (1999) Priscoan (4.00–4.03
Ga) orthogneisses from northwestern Canada. Contrib.
Mineral. Petrol. 134, 3–16.
Brasier, M.D., Green, O.R., Jephcoat, A.P., Kleppe, A.K.,
Van Kranendonk, M.J., Lindsay, J.F., Steele, A., and
Grassineau, N.V. (2002) Questioning the evidence for
Earth’s oldest fossils. Nature 416, 76–81.
Brocks, J.J., Logan, G.A., Buick, R., and Summons, R.E.
(1999) Archean molecular fossils and the early rise of
eukaryotes. Science 285, 1033–1036.
Brocks, J.J., Buick, R., Summons, R.E., and Logan, G.A. (2003)
A reconstruction of Archean biological diversity based on
molecular fossils from the 2.78 to 2.45 billion-year-old
Mount Bruce Supergroup, Hamersley Basin, Western
Australia. Geochim. Cosmochim. Acta 67, 4321–4335.
Brown, R.A., Burrows, C.J., Casertano, S., Clampin, M.,
Ebbets, D.C., Ford, E.B., Jucks, K.W., Kasdin, N.J., Kilston,
S., Kuchner, M.J., Seager, S., Sozzetti, A., Spergel,
D.N., Traub, W.A., Trauger, J.T., and Turner, E.L. (2003)
The 4-m space telescope for investigating extrasolar
Earth-like planets in starlight: TPF is HST2. Proc. SPIE
4854, 95–107.
Budyko, M.I. (1969) The effect of solar radiation variations
on the climate of the Earth. Tellus 21, 611–619.
Caldeira, K. and Kasting J.F. (1992) The life span of the
biosphere revisited. Nature 360, 721–723.
Caroff, L.I. and Des Marais, D.J., eds. (2000) Pale Blue Dot
2 Workshop: Habitable and Inhabited Worlds Beyond Our
Own Solar System, Vol. CP-2000-209595, NASA Ames
Research Center, Moffett Field, CA.
Chambers, J.E. (1999) A hybrid symplectic integrator that
permits close encounters between massive bodies.
Month. Not. R. Astron. Soc. 304, 793–799.
Charnley, S.B. and Rodgers, S.D. (2002) The end of interstellar
chemistry as the origin of nitrogen in comets and
meteorites. Astrophys. J. 569, L133–L137.
Chen, G.Q. and Ahrens, T.J. (1997) Erosion of terrestrial
planet atmospheres by surface motion after a large impact.
Phys. Earth Planet. Interiors 100, 21–26.
Chyba, C.F. (1987) The cometary contribution to the ocean
of primitive Earth. Nature 330, 632–635.
Cincotta, P.M. and Simo, C. (2000) Simple tools to study
global dynamics in non-axisymmetric galactic potentials—
I. Astron. Astrophys. Suppl. 147, 205–228.
Coakley, B.J. and Cochran, J.R. (1998) Gravity evidence of
very thin crust at the Gakkel Ridge. Earth Planet. Sci.
Lett. 162, 81–95.
Coltice, N., Simon, L., and Lécuyer, C. (2004) Carbon isotope
cycle and mantle structure. Geophys. Res. Lett. 31,
L05603.
Cuntz, M. (2002) Orbital stability of terrestrial planets inside
the habitable zones of extrasolar planetary systems.
Astrophys. J. 572, 1024–1030.
Cyr, K.E., Sears, W.D., and Lunine, J.I. (1998) Distribution
and evolution of water ice in the solar nebula: Implications
for solar system body formation. Icarus 135,
537–548.
Cyr, K.E., Sharp, C.M., and Lunine, J.I. (1999) Effects of
the redistribution of water in the solar nebula on nebular
chemistry. J. Geophys. Res. 104, 19003–19014.
Dauphas, N. (2003) The dual origin of the terrestrial atmosphere.
Icarus 165, 326–339.
Dauphas, N., Robert, F., and Marty, B. (2000) The late
asteroidal and cometary bombardment of Earth as
recorded in water deuterium to protium ratio. Icarus
148, 508–512.
David, E.-M., Quintana, E.V., Fatuzzo, M., and Adams,
F.C. (2003) Dynamical stability of Earth-like planetary
orbits in binary systems. Publ. Astron. Soc. Pac. 115,
825–836.
Delsemme, A.H. (1999) The deuterium enrichment observed
in recent comets is consistent with the cometary
origin of seawater. Planet. Space Sci. 47, 125–131.
Des Marais, D.J., Harwit, M., Jucks, K., Kasting, J.F., Lunine,
J.I., Lin, D., Seager, S., Schneider, J., Traub, W.,
and Woolf, N. (2002) Biosignatures and Planetary Properties
to Be Investigated by the TPF Mission, JPL Publication
01-008, Jet Propulsion Laboratory, Pasadena, CA.
Deutsch, A. and Stoffler, D. (1987) Rb-Sr-analyses of
Apollo 16 melt rocks and a new age estimate for the
Imbrium basin—lunar basin chronology and the early
heavy bombardment of the moon. Geochim. Cosmochim.
Acta 51, 1951–1964.
Dick, H.J.B., Lin, J., and Schouten, H. (2003) An ultraslowspreading
class of ocean ridge. Nature 426, 405–412.
Dick, S.J. (1982) Plurality of Worlds: The Origins of the Extraterrestrial
Life Debate from Democritus to Kant, Cambridge
University Press, Cambridge, UK.
Dole, S.H. (1970) Habitable Planets for Man, American Elsevier
Publishing Co., New York.
Doolittle, R.F., Deng, D.-F., Tsang, S., Cho, G., and Little,
E. (1996) Determining divergence times of the major
kingdoms of living organisms with a protein clock. Science
271, 470–477.
Doyle, L.R., ed. (1996) Circumstellar Habitable Zones—Proceedings
of the First International Conference, Travis House
Publications, Menlo Park, CA.
Duncan, M.J., Levison, H.F., and Lee, M.H. (1998) A multiple
time step symplectic algorithm for integrating
close encounters. Astron. J. 116, 2067–2077.
Dutkiewicz, A., Rasmussen, B., and Buick, R. (1998) Oil
preserved in fluid inclusions in Archean sandstones.
Nature 395, 885–888.
Dvorak, R. and Süli, Á. (2002) On the stability of the terrestrial
planets as models for extrasolar planetary systems.
Celest. Mech. Dynam. Astron. 83, 77–95.
Dvorak, R., Pilat-Lohinger, E., Funk, B., and Freistetter, F.
(2003a) Planets in habitable zones: A study of the binary
Gamma Cephei. Astron. Astrophys. 398, L1–L4.
Dvorak, R., Pilat-Lohinger, E., Funk, B., and Freistetter, F.
(2003b) A study of the stable regions in the planetary
system HD 74156—can it host earthlike planets in habitable
zones? Astron. Astrophys. 410, L13–L16.
Eberhardt, P., Reber, M., Krankowsky, D., and Hodges,
R.R. (1995) The D/H and 18O/16O ratios in water from
comet P/Halley. Astron. Astrophys. 302, 301–316.
Edwards, M.H., Kurras, G.J., Tolstoy, M., Bohnenstiehl,
D.R., Coakley, B.J., and Cochran, J.R. (2001) Evidence
of recent volcanic activity on the ultraslow-spreading
Gakkel ridge. Nature 409, 808–812.
Ehrenfreund, P. and Charnley, S.B. (2000) Organic molecules
in the interstellar medium, comets and meteorites:
A voyage from dark clouds to the early Earth. Annu.
Rev. Earth Planet. Sci. 38, 427–483.
Fiquet, G., Guyot, F., Kunz, M., Matas, J., Andrault, D.,
and Hanfland, M. (2002) Structural refinements of magnesite
at very high pressure. Am. Mineral. 87, 1261–1265.
Fischer, D.A., Marcy, G.W., Butler, R.P., Laughlin, G., and
Vogt, S.S. (2002) A second planet orbiting 47 Ursae Majoris.
Astrophys. J. 564, 1028–1034.
Foster, A. and Nimmo, F. (1996) Comparisons between
the rift systems of East Africa, Earth and Beta Regio,
Venus. Earth Planet. Sci. Lett. 143, 183–195.
Franck, S. and Bounama, C. (1995) Rheology and volatile
exchange in the framework of planetary evolution. Adv.
Space Res. 15, 79–86.
Franck, S. and Bounama, C. (1997) Continental growth
and volatile exchange during Earth’s evolution. Phys.
Earth Planet. Interiors 100, 189–196.
Franck, S., Kassacki, K., and Bounama, C. (1999) Modeling
the global carbon cycle for the past and future
evolution of the Earth system. Chem. Geol. 159,
305–317.
Franck, S., Block, A., von Bloh, W., Bounama, C.,
Schellnhuber, H.-J., and Svirezhev, Y. (2000) Habitable
zone for Earth-like planets in the solar system. Planet.
Space Sci. 48, 1099–1105.
Franck, S., von Bloh, W., Bounama, C., Steffen, M., Schönberner,
D., and Schellnhuber, H.-J. (2001) Limits of photosynthesis
in extrasolar planetary systems for Earthlike
planets. Adv. Space Res. 28, 695–700.
Fridlund, C.V.M. and Gondoin, P. (2003) Darwin mission.
Proc. SPIE 4852, 394–404.
Furnes, H., Banerjee, N.R., Muehlenbachs, K., Staudigel,
H., and de Wit, M. (2004) Early life recorded in Archean
pillow lavas. Science 304, 578–581.
Gaidos, E.J. (2000) A cosmochemical determinism in the
formation of Earth-like planets. Icarus 145, 637–640.
Garrels, R.M. and Mackenzie, F.T. (1971) Evolution of Sedimentary
Rocks, W.W. Norton, New York.
Gehman, C.S., Adams, F.C., and Laughlin, G. (1996) The
prospects for Earth-like planets within known extrasolar
planetary systems. Publ. Astron. Soc. Pac. 108, 1018–1023.
Genda, H. and Abe, Y. (2003) Survival of a proto-atmosphere
through the stage of giant impacts: The mechanical
aspects. Icarus 164, 149–162.
Gonzalez, G., Brownlee, D., and Ward, P. (2001) The
Galactic habitable zone: Galactic chemical evolution.
Icarus 152, 185–200.
Gozdziewski, K. (2002) Stability of the 47 UMa planetary
system. Astron. Astrophys. 393, 997–1013.
Grotzinger, J. and Kasting, J.F. (1993) New constraints on
Precambrian ocean composition. J. Geol. 101, 235–243.
Grotzinger, J.P. and Rothman, D.H. (1996) An abiotic
model for stromatolite morphogenesis. Nature 383,
423–425.
Hammouda, T. (2003) High-pressure melting of carbonated
eclogite and experimental constraints on carbon
recycling and storage in the mantle. Earth Planet. Sci.
Lett. 214, 357–368.
Hardie, L.A. (2003) Secular variations in Precambrian seawater
chemistry and the timing of Precambrian aragonite
seas and calcite seas. Geology 31, 785–788.
Hart, M.H. (1979) Habitable zones about main sequence
stars. Icarus 37, 351–357.
Hashizume, K., Chaussidon, M., Marty, B., and Robert, F.
(2000) Solar wind record on the Moon: Deciphering
presolar from planetary nitrogen. Science 290, 1142–
1145.
Hashizume, K., Chaussidon, M., Marty, B., and Terada,
K. (2004) Protosolar carbon isotopic composition: Implications
for the origin of meteoritic organics. Astrophys.
J. 600, 480–484.
He, S. and Morse, J.W. (1993) The carbonic acid system
and calcite solubility in aqueous Na-K-Ca-Mg-Cl-SO4
solutions from 0 to 90°C. Geochim. Cosmochim. Acta 57,
3533–3555.
Hessler, A.M., Lowe, D.R., Jones, R.L., and Bird, D.K.
(2004) A lower limit for atmospheric carbon dioxide
levels 3.2 billion years ago. Nature 428, 736–738.
Hilgren, V.J., Gessmann, C.K., and Li, J. (2000) An experimental
perspective on the light element in Earth’s core.
In Origin of the Earth and Moon, edited by R.M. Canup
and K. Righter, University of Arizona Press, Tucson,
pp. 245–263.
Hirao, N., Kondo, T., Ohtani, E., Takemura, K., and
Kikegawa, T. (2004) Compression of iron hydrite to 80
GPa and hydrogen in the Earth’s inner core. Geophys.
Res. Lett. 31, L06616.
Holloway, J.R. (1998) Graphite-melt equilibria during
mantle melting: Constraints on CO2 in MORB magmas
and the carbon content of the mantle. Chem. Geol. 147,
89–97.
Holman, M.J. and Wiegert, P.A. (1999) Long-term stability
of planets in binary systems. Astron. J. 117, 621–628.
Holzheid, A., Sylvester, P., O’Neill, H.S.C., Rubie, D.C., and
Palme, H. (2000) Evidence for a late chondritic veneer in
the Earth’s mantle from high-pressure partitioning of palladium
and platinum. Nature 406, 396–399.
Huang, S.-S. (1959) Occurence of life in the universe. Am.
Sci. 47, 397–402.
Isshiki, M., Irifune, T., Hirose, K., Ono, S., Ohishi, Y.,
Watanuki, T., Nishibori, E., Takata, M., and Sakata, M.
(2003) Stability of magnesite and its high-pressure form
in the lowermost mantle. Nature 427, 60–63.
Jenkins, G.S. (1996) A sensitivity study of changes in
Earth’s rotation rate with an atmospheric general circulation
model. Global Planet. Change 11, 141–154.
Jewitt, D.C., Matthews, H.E., Owen, T., and Meier, R. (1997)
Measurements of 12C/13C, 14N/15N, and 32S/34S ratios in
Comet Hale-Bopp (C/1995 O1). Science 278, 90–93.
Jokat, W., Ritzmann, O., Schmidt-Aursch, M.C., Drachev,
S., Gauger, S., and Snow, J. (2003) Geophysical evidence
for reduced melt production on the Arctic ultraslow
Gakkel mid-ocean ridge. Nature 423, 962–965.
Jones, B.W. and Sleep, P.N. (2002) The stability of the orbits
of Earth-mass planets in the habitable zone of 47
Ursae Majoris. Astron. Astrophys. 393, 1015–1026.
Joshi, M.M., Haberle, R.M., and Reynolds, R.T. (1997) Simulations
of the atmospheres of synchronously rotating
terrestrial planets orbiting M dwarfs: Conditions for atmospheric
collapse and implications for habitability.
Icarus 129, 450–465.
Kasting, J.F. and Catling, D. (2003) Earth: Evolution of a habitable
planet. Annu. Rev. Astron. Astrophys. 41, 429–463.
Kasting, J.F., Whitmire, D.P., and Reynolds, R.T. (1993)
Habitable zones around main sequence stars. Icarus 101,
108–128.
Kempe, S. and Degens, E.T. (1985) An early soda ocean?
Chem. Geol. 53, 95–108.
Keppler, H., Wiedenbeck, M., and Shcheka, S.S. (2003)
Carbon solubility in olivine and the mode of carbon
storage in the Earth’s mantle. Nature 424, 414–416.
Kimura, K., Lewis, R.S., and Anders, E. (1974) Distribution
of gold and rhenium between nickel-iron and silicate
melts: Implications for the abundance of
siderophile elements on the Earth and Moon. Geochim.
Cosmochim. Acta 38, 683–701.
Kleine, T., Münker, C., Mezger, K., and Palme, H. (2002)
Rapid accretion and early core formation on asteroids
and the terrestrial planets from Hf-W chronometry. Nature
418, 952–955.
Kominami, J. and Ida, S. (2004) Formation of terrestrial
planets in a dissipating gas disk with Jupiter and Saturn.
Icarus 167, 231–243.
Kortenkamp, S.J. and Wetherill, G.W. (2000) Terrestrial
planet and asteroid formation in the presence of giant
planets. I. Relative velocities of planetesimals subject to
Jupiter and Saturn perturbations. Icarus 143, 60–73.
Kress, M.E. and Tielens, A.G.G.M. (2001) The role of
Fischer-Tropsch catalysis in solar nebula chemistry. Meteoritics
Planet. Sci. 36, 75–92.
Kuchner, M.J. (2003) Volatile-rich Earth-mass planets in
the habitable zone. Astrophys. J. 596, L105–L108.
Kuramoto, K. (1997) Accretion, core formation, H and C
evolution of the Earth and Mars. Phys. Earth Planet. Interiors
100, 3–20.
Kuramoto, K. and Matsui, T. (1996) Partitioning of H and
C between the mantle and core during the core formation
of the Earth: Its implications for the atmospheric
evolution and redox state of the mantle. J. Geophys. Res.
101, 14909–14932.
Laskar, J. and Robutel, P. (1993) The chaotic obliquity of
the planets. Nature 361, 608–614.
Laughlin, G., Chambers, J., and Fischer, D. (2002) A dynamical
analysis of the 47 Ursae Majoris planetary system.
Astrophys. J. 579, 455–467.
Lécuyer, C. (1998) The hydrogen isotope composition of
seawater and the global water cycle. Chem. Geol. 145,
249–261.
Lécuyer, C., Simon, L., and Guyot, F. (2000) Comparison
of carbon, nitrogen and water budgets on Venus and
Earth. Earth Planet. Sci. Lett. 181, 33–40.
Lee, D.-C., Halliday, A.N., Leya, I., Wieler, R., and
Wiechert, U. (2002) Cosmogenic tungsten and the origin
and earliest differentiation of the Moon. Earth
Planet. Sci. Lett. 198, 267–274.
Lenardic, A., Nimmo, F., and Moresi, L. (2004) Growth of
the hemispheric dichotomy and the cessation of plate
tectonics on Mars. J. Geophys. Res. 109, 10.1029/
2003JE002172.
Levine, B.M., Shao, M., Beichman, C.A., Mennesson, B.P.,
Morgan, R.M., Orton, G.S., Serabyn, E., Unwin, S.C.,
Velusamy, T., and Woolf, N.J. (2003) Visible light Terrestrial
Planet Finder: Planet detection and spectroscopy
by nulling interferometry with a single aperture
telescope. Proc. SPIE 4852, 221–229.
Levison, H.F. and Agnore, C. (2003) The role of giant
planets in terrestrial planet formation. Astron. J. 125,
2692–2713.
Levison, H.F. and Duncan, M.J. (1994) The long-term dynamical
behavior of short-period comets. Icarus 108,
18–36.
Libourel, G., Marty, B., and Humbert, F. (2003) Nitrogen
solubility in basaltic melt. I—Effect of oxygen fugacity.
Geochim. Cosmochim. Acta 67, 4123–4135.
Lille, C.F., Atkinson, C.B., Casement, L.S., Flannery, M.R.,
Kroening, K.V., Moses, S.L., and Glenn, P.E. (2003) Infrared
coronograph for the Terrestrial Planet Finder
Mission I: Overview and design concept. Proc. SPIE
4860, 84–95.
Lineweaver, C.H. (2001) An estimate of the age distribution
of terrestrial planets in the Universe: Quantifying
metallicity as a selection effect. Icarus 151, 307–313.
Lineweaver, C.H. and Grether, D. (2003) What fraction of
Sun-like stars have planets. Astrophys. J. 598, 1350–1360.
Lissauer, J.J. (1993) Planet formation. Annu. Rev. Astron.
Astrophys. 31, 129.
Lissauer, J.J. (2001) The effect of a planet in the asteroid
belt on the orbital stability of the terrestrial planets.
Icarus 154, 449–458.
Lissauer, J.J. (2002) Extrasolar planets. Nature 419,
355–358.
Lissauer, J.J., Dones, L., and Ohtsuki, K. (2000) Origin and
evolution of terrestrial planet rotation. In Origin of the
Earth and Moon, edited by R.M. Canup and K. Righter,
University of Arizona Press, Tucson, pp. 101–112.
Livio, M. (1999) How rare are extraterrestrial civilizations
and when did they emerge? Astrophys. J. 511, 429–431.
Lorenz, R.D., Lunine, J.I., and McKay, C.P. (1997) Titan
under a red giant sun: A new kind of “habitable” moon.
Geophys. Res. Lett. 24, 2905–2908.
Lovejoy, A. (1936) The Great Chain of Being: A Study of the
History of an Idea, Harper, New York.
Lunine, J.I., Chambers, J., Morbidelli, A., and Leshin, L.A.
(2003) The origin of water on Mars. Icarus 165, 1–8.
Makino, J. and Aarseth, S.J. (1992) On a Hermite integrator
with Ahmad-Cohen scheme for gravitational manybody
problems. Proc. Astron. Soc. Jpn. 44, 141–151.
Mandell, A.M. and Sigurdsson, S. (2003) Survival of terrestrial
planets in the presence of giant planet migration.
Astrophys. J. 599, L111–L114.
Marty, B. (1995) Nitrogen content of the mantle inferred
from N2-Ar correlation in oceanic basalts. Nature 377,
326–329.
Matsui, T. and Abe, Y. (1986) Impact-induced atmospheres
and oceans on Earth and Venus. Nature 322,
526–528.
Maurette, M., Duprat, J., Engrand, C., Gounelle, M., Kurat,
G., Matrajt, G., and Toppani, A. (2000) Accretion of
neon, organics, CO2, nitrogen and water from large interplanetary
dust particles on the early Earth. Planet.
Space Sci. 48, 1117–1137.
Mayor, M. and Queloz, D. (1995) A Jupiter-mass companion
to a solar-type star. Nature 378, 355–359.
McGovern, P.J. and Schubert, G. (1989) Thermal evolution
of the Earth: Effects of volatile exchange between
atmosphere and interior. Earth Planet. Sci. Lett. 96,
27–37.
Meadows, V.S., Allen, M., Brown, L., Crisp, D., Fijany, A.,
Storrie-Lombardi, M., Ustinov, E., Velusamy, T.,
Richardson, M., Yung, Y., Huntress, W., DesMarais, D.,
Zahnle, K., Kasting, J., Morrow, C., Sleep, N., Cohen,
M., Nealson, K., Rye, R., and Coleman, M. (2001) The
Virtual Planetary Laboratory: Towards characterizing
extrasolar terrestrial planets [abstract]. Bull. Am. Astron.
Soc. 33, 40.12. Available online at: http://www.
aas.org/publications/baas/v33n3/dps2001/526.htm.
Meier, R., Owen, T.C., Matthews, H.E., Jewitt, D.C., Bockelée-
Morvan, D., Biver, N., Crovisier, J., and Gautier, D.
(1998) A determination of the HDO/H2O ratio in comet
C/1995 O1 (Hale-Bopp). Science 279, 842–844.
Melosh, H.J. and Vickery, A.M. (1989) Impact erosion of the
primordial atmosphere of Mars. Nature 338, 487–489.
Menou, K. and Tabachnik, S. (2003) Dynamical habitability
of known extrasolar planetary systems. Astrophys. J.
583, 473–488.
Michael, P.J., Langmuir, C.H., Dick, H.J.B., Snow, J.E.,
Goldstein, S.L., Graham, D.W., Lehnert, K., Kurras, G.,
Jokat, W., Mühe, R., and Edmonds, H.N. (2003) Magmatic
and amagmatic seafloor generation at the ultraslow-
spreading Gakkel ridge, Arctic Ocean. Nature 423,
956–961.
Miyazaki, A., Hiyagon, H., Sugiura, N., Hirose, K., and
Takahashi, E. (2004) Solubility of nitrogen and noble
gases in silicate melts under various oxygen fugacities:
Implications for the origin and degassing history of nitrogen
and noble gases in the Earth. Geochim. Cosmochim.
Acta 68, 387–401.
Mizuno, H. (1980) Formation of the giant planets. Prog.
Theor. Phys. 64, 544–557.
Mojzsis, S.J., Arrhenius, G., McKeegan, K.D., Harrison,
T.M., Nutman, A.P., and Friend, C.R.L. (1996) Evidence
for life on Earth by 3800 million years ago. Nature 384,
55–59.
Mojzsis, S.J., Harrison, T.M., and Pidgeon, R.T. (2001)
Oxygen-isotope evidence from ancient zircons for liquid
water at the Earth’s surface 4,300 Myr ago. Nature
409, 178–181.
Morbidelli, A., Chambers, J., Lunine, J.I., Petit, J.M.,
Robert, F., Valsecchi, G.B., and Cyr, K.E. (2000) Source
regions and timescales for the delivery of water to the
Earth. Meteoritics Planet. Sci. 35, 1309–1320.
Moresi, L. and Solomatov, V. (1998) Mantle convection
with a brittle lithosphere: Thoughts on the global tectonic
styles of the Earth and Venus. Geophys. J. Int. 133,
669–682.
Morse, J.M. and Mackenzie, F.T. (1998) Hadean ocean carbonate
geochemistry. Aquatic Geochem. 4, 301–319.
Morse, J.W. and He, S. (1993) Influence of T, S and PCO2
on the homogeneous nucleation of calcium carbonate
from seawater. Implications for whiting formation. Marine
Chem. 41, 291–298.
Nakamura, T. and Tajika, E. (2003) Climate changes of
Mars-like planets due to obliquity variations: Implications
for Mars. Geophys. Res. Lett. 30, 1685–1688.
Nakano, H., Kouchi, A., Tachibana, S., and Tsuchiyama,
A. (2003) Evaporation of interstellar organic materials
in the solar nebula. Astrophys. J. 592, 1252–1262.
Newman, W.I., Symbalisty, E.M.D., Ahrens, T.J., and
Jones, E.M. (1999) Impact erosion of planetary atmospheres:
Some surprising results. Icarus 138, 224–240.
Newsom, H.E. (1995) Composition of the Solar System,
planets, meteorites, and major terrestrial reservoirs. In
Global Earth Physics: A Handbook of Physical Constants,
American Geophysical Union, Washington, DC, pp.
159–189.
Nimmo, F. and McKenzie, D. (1998) Volcanism and tectonics
on Venus. Annu. Rev. Earth Planet. Sci. 26, 23–51.
Noble, M., Musielak, Z.E., and Cuntz, M. (2002) Orbital
stability of terrestrial planets inside the habitable zones
of extrasolar planetary systems. Astrophys. J. 572,
1024–1030.
Nutman, A.P., Mojzsis, S.J., and Friend, C.R.L. (1997)
Recognition of _3580 Ma water-lain sediments in West
Greenland and their significant for the early Archean
Earth. Geochim. Cosmochim. Acta 61, 2475–2484.
Oparin, A.I. and Fesenkov, V. (1960) The Universe, Foreign
Languages Publishing House, Moscow.
Owen, T.C. and Bar-Nun, A. (2000) Volatile contributions
from icy planetesimals. In Origin of the Earth and Moon,
edited by R.M. Canup and K. Righter, University of Arizona
Press, Tucson, pp. 459–474.
Owen, T., Mhaffy, P.R., Niemann, H.B., Atreya, S., and
Wong, M. (2001) Protosolar nitrogen. Astrophys. J. 553,
L77–L79.
Pavlov, A.A., Kasting, J.F., Brown, L.L., Rages, K.A., and
Freedman, R. (2000) Greenhouse warming by CH4 in
the atmosphere of early Earth. J. Geophys. Res. 105,
11981–11990.
Pepin, R.O. (1991) On the origin and early evolution of
terrestrial planet atmospheres and meteoritic volatiles.
Icarus 92, 2–79.
Phillips, R.J., Zuber, M.T., Solomon, S.C., Golombek, M.P.,
Jakosky, B.M., Banerdt, W.B., Smith, D.E., Williams,
R.M.E., Hynek, B.M., Aharonson, O., and Hauck, S.E.
(2000) Ancient geodynamics and global scale hydrology
on Mars. Science 291, 2587–2591.
Plank, T. and Langmuir, C.H. (1998) The chemical composition
of the subducting sediment and its consequences
for the crust and mantle. Chem. Geol. 145, 325–394.
Podesek, F.A. and Ozima, M. (2000) The xenon age of the
Earth. In Origin of the Earth and Moon, edited by R.M.
Canup and K. Righter, University of Arizona Press,
Tucson, pp. 63–72.
Pollack, J.B., Hubickyj, O., Bodenheimer, P., Lissauer, J.J.,
Podolak, M., and Greenzweig, Y. (1996) Formation of
the giant planets by concurrent accretion of solids and
gas. Icarus 124, 62–85.
Porcelli, D. and Pepin, R.O. (2000) Rare gas constraints on
early Earth history. In Origin of the Earth and Moon,
edited by R.M. Canup and K. Righter, University of Arizona
Press, Tucson, pp. 435–458.
Prinn, R.G. and Fegley, J. (1989) Solar nebular chemistry:
Origin of planetary, satellite, and cometary volatiles. In
Origin and Evolution of Planetary and Satellite Atmospheres,
edited by S.K. Atreya, J.B. Pollack, and M.S.
Matthews, University of Arizona Press, Tucson, pp.
78–136.
Quintana, E.V., Lissauer, J.J., Chambers, J.E., and Duncan,
M.J. (2002) Terrestrial planet formation in the _ Centauri
system. Astrophys. J. 576, 982–896.
Rampino, M.R. and Caldeira, K. (1994) The Goldilocks problem:
Climatic evolution and long-term habitability of terrestrial
planets. Annu. Rev. Astron. Astrophys. 32, 83–114.
Rasmussen, B. (2000) Filamentous microfossils in a 3,235-
million-year-old volcanogenic massive sulphide deposit.
Nature 405, 676–679.
Raymond, S.N., Quinn, T., and Lunine, J.I. (2004) Making
other Earths: Dynamical simulations of terrestrial
planet formation and water delivery. Icarus 168, 1–17.
Righter, K. (2003) Metal-silicate partitioning of siderophile
elements and core formation in the early Earth.
Annu. Rev. Earth Planet. Sci. 31, 135–174.
Righter, K. and Drake, M.J. (1997) Metal-silicate equilibrium
in a homogeneously accreting Earth: New results
for Re. Earth Planet. Sci. Lett. 146, 541–553.
Robert, F. (2002) Water and organic matter D/H ratios in
the solar system: A record of an early irradiation of the
nebula? Planet. Space Sci. 50, 1227–1234.
Rye, R. and Holland, H.D. (1998) Paleosols and the evolution
of atmospheric oxygen: A critical review. Am. J.
Sci. 298, 621–672.
Rye, R., Kuo, P.H., and Holland, H.D. (1995) Atmospheric
carbon dioxide concentrations before 2.2 billion years
ago. Nature 378, 603–605.
Saal, A.E., Hauri, E.H., Langmuir, C.H., and Perfit, M.R.
(2002) Vapour undersaturation in primitive mid-oceanridge
basalt and the volatile content of Earth’s upper
mantle. Nature 419, 451–455.
Sandford, S.A., Bernstein, M.P., and Dworkin, J.P. (2001)
Assessment of the interstellar processes leading to deuterium
enrichment in meteoritic organics. Meteoritics
Planet. Sci. 36, 1117–1133.
Sano, Y. and Williams, S.N. (1996) Fluxes of mantle and
subducted carbon along covergent plate boundaries.
Geophys. Res. Lett. 23, 2749–2752.
Sano, Y., Takahata, N., Nishio, Y., and Marty, B. (1998)
Nitrogen recycling in subduction zones. Geophys. Res.
Lett. 25, 2289–2292.
Sano, Y., Takahata, N., Nishio, Y., Fischer, T.P., and
Williams, S.N. (2001) Volcanic flux of nitrogen from the
Earth. Chem. Geol. 171, 263–271.
Schlesinger, W.H. (1997) Biogeochemistry: An Analysis of
Global Change, Academic Press, San Diego.
Schopf, J.W. (1993) Microfossils of the early Archean Apex
chert: New evidence of the antiquity of life. Science 260,
640–646.
Scott, H.P., Williams, Q., and Knittle, E. (2001) Stability
and equation of state of Fe3C to 73 GPa: Implications
for carbon in the Earth’s core. Geophys. Res. Lett. 28,
1875–1878.
Sephton, M.A., Verchovsky, A.B., Bland, P.A., Gilmour,
I., Grady, M.M., and Wright, I.P. (2003) Investigating
the variations in carbon and nitrogen isotopes in carbonaceous
chondrites. Geochim. Cosmochim. Acta 67,
2093–2108.
Simoneit, B. (2004) Prebiotic organic synthesis under hydrothermal
conditions: An overview. Adv. Space Res. 33,
88–94.
Sleep, N.H. (1994) Martian plate tectonics. J. Geophys. Res.
99, 5639–5655.
Sleep, N.H. (2000) Evolution of the mode of convection
within terrestrial planets. J. Geophys. Res. 105, 17563–
17578.
Sleep, N.H. and Zahnle, K.J. (2001) Carbon dioxide recycling
and implications for climate on ancient Earth. J.
Geophys. Res. 106, 1373–1399.
Sleep, N.H., Zahnle, K., and Neuhoff, P.S. (2001) Initiation
of clement surface conditions on the earliest Earth.
Proc. Natl. Acad. Sci. USA 98, 3666–3672.
Spohn, T. (1991) Mantle differentiation and thermal evolution
of Mars, Mercury, and Venus. Icarus 90, 222–236.
Stevenson, D.J. (1988) Rapid formation of Jupiter by diffusive
redistribution of water vapor in the solar nebula.
Icarus 75, 146–155.
Taylor, S.R. (1999) On the difficulties of making Earth-like
planets. Meteoritics Planet. Sci. 34, 317–329.
Terzieva, R. and Herbst, E. (2000) The possibility of nitrogen
isotopic fractionation in interstellar clouds.
Month. Not. R. Astron. Soc. 317, 563–568.
Thèbault, P., Marzari, F., and Scholl, F. (2002) Terrestrial
planet formation in exoplanetary systems with a giant
planet on an external orbit. Astron. Astrophys. 384, 594–602.
Timmes, F.X., Woosley, S.E., and Weaver, T.A. (1996)
Galactic chemical evolution: Hydrogen through zinc.
Astrophys. J. Suppl. Ser. 98, 617–658.
Tingle, T.N. (1998) Accretion and differentiation of carbon
in the early Earth. Chem. Geol. 147, 3–10.
Tolstikhin, I.N. and O’Nions, R.K. (1994) The Earth’s missing
xenon: A combination of early degassing and of rare
gas loss from the atmosphere. Chem. Geol. 115, 1–6.
Touma, J. and Wisdom, J. (1993) The chaotic obliquity of
Mars. Science 259, 237–241.
Trilling, D.E., Lunine, J.I., and Benz, W. (2002) Orbital migration
and the frequency of giant planet formation. Astron.
Astrophys. 394, 241–251.
Turcotte, D.L. and Schubert, G. (1982) Geodynamics: Application
of Continuum Physics to Geological Problems,
John Wiley, New York.
van Zuilen, M.A., Lepland, A., and Arrhenius, G. (2002)
Reassessing the evidence for the earliest traces of life.
Nature 418, 627–630.
Walker, J.C.G. and Brimblecombe, P. (1985) Iron and sulfur
in the pre-biologic ocean. Precambrian Res. 28, 205–222.
Walker, J.C.G., Hays, P.B., and Kasting, J.F. (1981) A negative
feedback mechanism for the long-term stabilization
of Earth’s surface temperature. J. Geophys. Res. 86,
9776–9782.
Wallace, A.R. (1903) Man’s Place in the Universe, McClure,
Phillips and Co., New York.
Weidenschilling, S.J. (2000) Formation of planetesimals
and accretion of the terrestrial planets. Space Sci. Rev.
92, 295–310.
Wetherill, G.W. (1996) The formation and habitability of
extra-solar planets. Icarus 119, 219–238.
Wetherill, G.W. and Stewart, G.R. (1993) Formation of
planetary embryos—effects of fragmentation, low relative
velocity, and independent variation of eccentricity
and inclination. Icarus 106, 190–209.
Whitmire, D.P., Matese, J.J., and Criswell, L. (1998) Habitable
planet formation in binary star systems. Icarus
132, 196–203.
Wilde, S.A., Valley, J.W., Peck, W.H., and Graham, C.M.
(2001) Evidence from detrital zircons for the existence
of continental crust and oceans on the Earth 4.4 Gyr
ago. Nature 409, 175–178.
Williams, D.M. and Kasting, J.F. (1997) Habitable planets
with high obliquities. Icarus 129, 254–267.
Williams, D.M. and Pollard, D. (2002) Earth-like worlds
on eccentric orbits: Excursions beyond the habitable
zone. Int. J. Astrobiol. 1, 61–69.
Williams, D.M. and Pollard, D. (2003) Extraordinary climates
of Earth-like planets: Three-dimensional climate
simulations at extreme obliquity. Int. J. Astrobiol. 2,
1–19.
Williams, D.M., Kasting, J.F., and Wade, R.A. (1997) Habitable
moons around extrasolar giant planets. Nature
385, 234–236.
Wisdom, J. and Holman, M.J. (1991) Symplectic maps for
the N-body problem. Astron. J. 102, 1528–1538.
Wood, B.J. (1993) Carbon in the core. Earth Planet. Sci. Lett.
117, 593–607.
Woolf, N. and Angel, J.R. (1998) Astronomical searches
for Earth-like planets and signs of life. Annu. Rev. Astron.
Astrophys. 36, 507–538.
Yung, Y.L. and DeMore, W.B. (1999) Photochemistry of
Planetary Atmospheres, Oxford University Press, New
York.
Zolotov, M.Y. and Shock, E.L. (2001) Stability of condensed
hydrocarbons in the solar nebula. Icarus 150,
323–337.
At 10:29 AM,
Joe G said…
Zach:
'Excellent point. Gaido et. al. point out in their "review of terrestrial planet habitability", that "Such evidence provides us with an important, if nominal, calibration point for our search for other habitable worlds."
Funny, the authors of "The Privileged Planet" said pretty much the same thing. Which should go without saying because that is what the NASA scientists were doing...
At 10:38 AM,
Joe G said…
Raevmo,
Thank you-
I noticed the "Galactic Habitable Zone" paper was referenced. Also the slide show that accompanies your paper (Gaidos et al.) does not share your sentiments. It calls terrestrial planet formation as theoretical. IOW we don't know.
At 11:44 AM,
Zachriel said…
joe g: "It calls terrestrial planet formation as theoretical. IOW we don't know."
No, joe g. "We don't know" is not the definition of a scientific theory. Germ Theory, Atomic Theory. The Theory of Gravity. Electron Theory.
theory: a plausible or scientifically acceptable general principle or body of principles offered to explain phenomena
At 9:31 AM,
Joe G said…
joe g: "It calls terrestrial planet formation as theoretical. IOW we don't know."
Zach:
No, joe g. "We don't know" is not the definition of a scientific theory.
I know that. I also know that is the position of anti-IDists. Go figure.
At 5:37 AM,
Lamon Hubbs said…
I have a background in engineering and my son has a masters in physics and is working on his phd your conclusions are very sound, the factors you list is by no means complete but demisteates the idea. Some other things. That may née d to be on your list is the mixture of gases I our atmosphere the critical ozone layer, the ability of life to constantly remove the buildup of co2 from the atmosphere so as. To be stored in solid form. Also some of the other scientist think something about our existence is just a little too. Right because here is a new experiment that is being worvked on.
"Ever wonder if the universe is really a simulation? Well, physicists do too. Recently, a group of physicists have devised a way that could conceivably figure out one way or the other whether that is the case. There is a paper describing their work on arXiv. Some other physicists propose that the universe is actually a giant hologram with all the action actually occurring on a two-dimensional boundary
At 12:45 PM,
Joe G said…
Hi Lamon-
Mixture of gases-> don't recall where I read it but there was something about our rotation that mixed the gases, as in if the rotation was much slower the O2 wouldn't be very well mixed and there may be uninhabitable zones due to the lack of O2 in those areas.
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