Mars, as far as we can tell, has very little water compared to Earth, even back when it appears to have had liquid water on the surface. It's a bit further out, so we'd expect it to have more water compared to the rest of the inner planets. It seems to be consistent with occasional deliveries of water from collisions with comets. In comparison, Earth has vastly more water.
I don't know if there are any astrobiologists or chemists,
but this brings to mind one of my favorite pet theories regarding abiogenesis, one that I've been thinking of more and more since the new horizons mission.
When we did the flyby of Pluto, I was drop jawed when we saw how dynamic the surface was. I sincerely expected a rockier, more oxidized, surface with no clear evidence of a geological cycle. Obviously what we saw was far more complex, and it brought the idea that a geology of volatile ices would be possible on these more marginal bodies (like Pluto).
The question I have is regarding what kinds of chemistry are possible on icy bodies like Pluto. If there is a complex geology, this indicates to me that things are going from liquid to solid (nitrogen ice, oxygen ice, etc..), so are some kinds of chemical bonds (specifically, organic ones) can form if a body like Pluto is has a dynamic geology?
Is it possible that the organic precursors for life are constantly accumulating on icy bodies like Pluto, and while obviously, live can't form on Pluto, could an impact discharge a massive quantity of precursor chemistry onto a planet more hospitable?
Its an interesting aside that pretty much imminently after the earths surface solidified and cooled after the impact even, life began.
Sure, but my point here isn't about presence, but quantity. We've known that radiation can cause the creation of bio-molecules and precursor molecules for a very long time. But there almost no way that process can generate a significant enough quantity of these molecules to really seed planets. Largely its about concentration gradients, which is why I personal have found arguments about life forming via early oceans unconvincing. A couple asteroids (or even hundreds) worth of bio-molecules spread out over an ocean, is still basically nothing. You have to have enough material concentrated in a small enough space; you need a thermodynamic process that postpones equilibrium; then you need a gradient to drive the formation of more and more complicated molecules.
Like, Pluto type objects are far and away more common then earthlike objects. If there is a process that can accumulate bio-molecules in mass on these types of bodies, that's pretty game changing.
You've probably read 'The Vital Question'? [0] I thoroughly enjoyed it and the theory presented that life originated on alkaline marine vents where there were natural energy gradients that could be exploited.
> Its an interesting aside that pretty much imminently after the earths surface solidified and cooled after the impact even, life began.
So when I read this, it makes me want to read more about how these conditions could have been set up. Can you point me towards a good read(s) on this pre-life stage of Earth?
No I've not read that. My background is in botany and I took coursework in evolutionary biology and evolutionary theory.
Its much more technical than the book you referenced, but I highly recommend:
However, a quick browse of the TOC and first pages suggests it wasn't quite what I was angling for with my question to you. I had in mind a discussion on the conditions required for abiogenesis, rather than subsequent evolution.
That doesn't bode well for the idea of habitable planets in other solar systems. If this kind of collision is relatively rare, most rocky exo-planets will have much less water than Earth has.
Reminds me of Asimov's storyline in the Foundation series about the rarity of the planet that humans come from (and the reason no complex lifeforms existed anywhere else), although his premise was a large amount of radioactivity on earth, IIRC.
We just don't know enough about life or planet formation to know how this bodes.
On its surface, everything that makes the formation of the Earth appear rarer would suggest life, in general, is rarer but honestly we don't know. We don't even know if there's life on Europa even though there would appear to be all the conditions present to make life as it lives at the bottom of our oceans.
We don't even know if water is a reasonable prerequisite for life. We don't know if life has to be carbon-based. Sulfur also presents a reasonable alternative. Would we even recognize other life if was right in front of us if it relied on completely different mechanisms? Maybe even our idea of time is too short lived or long lived to even recognize other complex systems as alive.
We shouldn't extrapolate too much from a single data point.
To me it seems that the early estimations of the numbers of inhabited planets from the Drake equations seem like hubris.
Aren't we moving from the "we live in a Star Trek type galaxy, teaming with life" to "well, maybe we are alone in the whole Galaxy but not the Universe" to "Actually, the more we learn about how life on Earth came to be, the more it looks like we are alone in the whole UNIVERSE -- because it seems like every day we find more free terms to the Drake equation".
Isn't the whole "we really don't know yet" argument hubris?
Isn't it true that you cannot prove the lack of existence of something?
Compared to 50 years ago, where do we stand with the question "Are we alone in the universe?"
What is 50 years of data telling us, should we be more optimistic or pessimistic?
Or is it just saying "we really don't know yet" -- because that's where I believe the real hubris lies -- not accepting the most likely scenario the data we have points to.
+1. Also, we don't have many data points to suggest that this is relatively rare that objects from outer solar systems tend to move in later. May be that is quite common, we don't really know - we don't have enough data.
And even if we assume it is rare, how rare exactly? The numbers are so uncertain that we can say nothing yet.
Genuinely curious about sulfur-based life, what indications do we have that it could actually form the base for life instead of carbon?
I mean I know very little about biochemistry but I do know life on earth has some INCREDIBLY complex biochemistry based on carbon.
Also what's the point of sulfur-based life, isn't carbon omnipresent in the universe?
Why wouldn't liquid water be an absolute must for life?
Wouldn't any kind of complex life need a solvent that would allow the complex biochemistry to take place?
What would the alternatives to water then be?
It simply isn't true that we're completely ignorant on these questions. We know an awful lot about the chemistry of all the known elements and it's pretty clear water and Carbon are by far the best candidates for supporting complex, rich chemistries across a wide range of environmental conditions.
It's not that alternative life chemistries are necessarily impossible, but equally it's plausible that they might well be non-viable above a very primitive level at best. They would have many orders of magnitude fewer options available to them for biochemical resources, pathways and molecular geometries to take advantage of. Chemically speaking, not all elements are created equal.
Take Sulphur for example. It's far more reactive than carbon, so chemically unstable in many more environmental conditions. It generally only forms linear chains, rather than the complex branching structures of carbon. It also bonds with far fewer other elements in ways that are likely to be chemically useful. If you have carbon available, Sulphur is a very poor substitute. It's high reactivity might make it a passable alternative to Oxygen though.
To address your point, I would say we are extremely ignorant about what the solution space of life looks like. Hydrothermal vents are a very recent discovery. Before this discovery, it was unexpected that such complex and large organisms could exist without light from the sun. As a planet, Earth is teeming with life. Everywhere you look on Earth, you can find it. Even though we have a good understanding of chemistry, we have little clue as to what's important to form complex and self-propagating systems.
As the sibling comment points out, we really just don't know what else is out there and how common or rare the earth situation is.
I think the way one reacts to something like this is an interesting Rorschach test, though.
I had the same gut reaction you do: this probably means that life-bearing planets are even rarer than I already thought. But I think that because it confirms my personal bias - that we don't see evidence of other life in the galaxy because it isn't there.
Other replies to your comment call this hubris and remind you that you're extrapolating - which is true. But in my experience with people who jump that direction, it's because their bias (and/or hope) is that we can't be alone and that we just haven't found other life yet.
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[ 2.5 ms ] story [ 92.7 ms ] threadhttps://en.wikipedia.org/wiki/Theia_(planet)
When we did the flyby of Pluto, I was drop jawed when we saw how dynamic the surface was. I sincerely expected a rockier, more oxidized, surface with no clear evidence of a geological cycle. Obviously what we saw was far more complex, and it brought the idea that a geology of volatile ices would be possible on these more marginal bodies (like Pluto).
The question I have is regarding what kinds of chemistry are possible on icy bodies like Pluto. If there is a complex geology, this indicates to me that things are going from liquid to solid (nitrogen ice, oxygen ice, etc..), so are some kinds of chemical bonds (specifically, organic ones) can form if a body like Pluto is has a dynamic geology?
Is it possible that the organic precursors for life are constantly accumulating on icy bodies like Pluto, and while obviously, live can't form on Pluto, could an impact discharge a massive quantity of precursor chemistry onto a planet more hospitable?
Its an interesting aside that pretty much imminently after the earths surface solidified and cooled after the impact even, life began.
Asteroids on Earth have been found carrying organic compounds: https://www.smithsonianmag.com/science-nature/the-building-b...
Like, Pluto type objects are far and away more common then earthlike objects. If there is a process that can accumulate bio-molecules in mass on these types of bodies, that's pretty game changing.
> Its an interesting aside that pretty much imminently after the earths surface solidified and cooled after the impact even, life began.
So when I read this, it makes me want to read more about how these conditions could have been set up. Can you point me towards a good read(s) on this pre-life stage of Earth?
[0] https://www.goodreads.com/book/show/26530386-the-vital-quest...
https://www.amazon.com/Not-Design-Retiring-Darwins-Watchmake...
Warning: this book is very much oriented towards a technical discussion in evolutionary biology. Its not really built for entertainment.
However, a quick browse of the TOC and first pages suggests it wasn't quite what I was angling for with my question to you. I had in mind a discussion on the conditions required for abiogenesis, rather than subsequent evolution.
Thanks.
Reminds me of Asimov's storyline in the Foundation series about the rarity of the planet that humans come from (and the reason no complex lifeforms existed anywhere else), although his premise was a large amount of radioactivity on earth, IIRC.
On its surface, everything that makes the formation of the Earth appear rarer would suggest life, in general, is rarer but honestly we don't know. We don't even know if there's life on Europa even though there would appear to be all the conditions present to make life as it lives at the bottom of our oceans.
We don't even know if water is a reasonable prerequisite for life. We don't know if life has to be carbon-based. Sulfur also presents a reasonable alternative. Would we even recognize other life if was right in front of us if it relied on completely different mechanisms? Maybe even our idea of time is too short lived or long lived to even recognize other complex systems as alive.
We shouldn't extrapolate too much from a single data point.
To me it seems that the early estimations of the numbers of inhabited planets from the Drake equations seem like hubris.
Aren't we moving from the "we live in a Star Trek type galaxy, teaming with life" to "well, maybe we are alone in the whole Galaxy but not the Universe" to "Actually, the more we learn about how life on Earth came to be, the more it looks like we are alone in the whole UNIVERSE -- because it seems like every day we find more free terms to the Drake equation".
Isn't the whole "we really don't know yet" argument hubris?
Isn't it true that you cannot prove the lack of existence of something?
Compared to 50 years ago, where do we stand with the question "Are we alone in the universe?"
What is 50 years of data telling us, should we be more optimistic or pessimistic?
Or is it just saying "we really don't know yet" -- because that's where I believe the real hubris lies -- not accepting the most likely scenario the data we have points to.
And even if we assume it is rare, how rare exactly? The numbers are so uncertain that we can say nothing yet.
I mean I know very little about biochemistry but I do know life on earth has some INCREDIBLY complex biochemistry based on carbon.
Also what's the point of sulfur-based life, isn't carbon omnipresent in the universe?
Why wouldn't liquid water be an absolute must for life? Wouldn't any kind of complex life need a solvent that would allow the complex biochemistry to take place? What would the alternatives to water then be?
It's not that alternative life chemistries are necessarily impossible, but equally it's plausible that they might well be non-viable above a very primitive level at best. They would have many orders of magnitude fewer options available to them for biochemical resources, pathways and molecular geometries to take advantage of. Chemically speaking, not all elements are created equal.
Take Sulphur for example. It's far more reactive than carbon, so chemically unstable in many more environmental conditions. It generally only forms linear chains, rather than the complex branching structures of carbon. It also bonds with far fewer other elements in ways that are likely to be chemically useful. If you have carbon available, Sulphur is a very poor substitute. It's high reactivity might make it a passable alternative to Oxygen though.
To address your point, I would say we are extremely ignorant about what the solution space of life looks like. Hydrothermal vents are a very recent discovery. Before this discovery, it was unexpected that such complex and large organisms could exist without light from the sun. As a planet, Earth is teeming with life. Everywhere you look on Earth, you can find it. Even though we have a good understanding of chemistry, we have little clue as to what's important to form complex and self-propagating systems.
I think the way one reacts to something like this is an interesting Rorschach test, though.
I had the same gut reaction you do: this probably means that life-bearing planets are even rarer than I already thought. But I think that because it confirms my personal bias - that we don't see evidence of other life in the galaxy because it isn't there.
Other replies to your comment call this hubris and remind you that you're extrapolating - which is true. But in my experience with people who jump that direction, it's because their bias (and/or hope) is that we can't be alone and that we just haven't found other life yet.
I just think that's interesting.
[1]http://dx.doi.org/10.1038/s41550-019-0779-y