Could There Be Life On Titan? 122
Adam Korbitz writes "Astrobiology Magazine reports on new research indicating extremophile microbes may be able to live on Titan, the sixth and largest moon of Saturn — in spite of the fact that the moon is largely ice and covered with lakes of liquid methane. Titan joins Mars, Venus, Europa and Enceladus as a potential home to extremophile life in our solar system."
Joins? (Score:5, Interesting)
Titan has been a prime candidate for life for as long as I can remember. Since they figured out that it had an atmosphere, it probably had lakes of some kinde and pretro.. possibility for life.
What about the subsurface ocean? (Score:5, Interesting)
Re:Joins? (Score:5, Interesting)
Considering the vast variety of conditions where life exists on earth I would consider it likely that there is life elsewhere too.
And with life - it may be completely different from the life we know about, but if there is life it is single-cell organisms that we should expect.
Even here on earth we have bacteria that actually thrives in environments that would kill most other forms of life. All the way from extremely acid environment that easily would tear through human flesh to high temperatures well above the boiling point and radiation so hard that it cracks the DNA in the cells - which the bacteria resolves by joining it together again with processes still unknown. And freezing bacteria will just suspend them or make them behave in slow motion.
In any atmosphere where there is complex molecules - especially amino acids - there is a potential for life remotely similar to us on a cellular level. But of course - there may be life in completely different forms with completely different timespans, maybe so long that we wouldn't recognize it as life.
On Titan, water ice is a rock (Score:5, Interesting)
Titan is a very different place from Earth. Water ice is a rock (surface temperatures never come close to the melting point) and, critically, temperature / entropy gradients are much smaller than on Earth. (It's not just cold, the flow of energy is slow.) So, if there is life, i would anticipate not something like terrestrial extremophiles, but an entirely new form of life, which doesn't use water as a medium and which would be very slow from our viewpoint. I asbolutely think that such life could evolve, if it is possible at all, but who knows if it is possible. Going there would be one way to find out, but that will neither be easy, simple, cheap or quick.
I think that the article is misleading in one respect - a body of liquid water might survive for a while (in the same way that a pool of lava - molten rock - can survive for decades or longer on the Earth, and presumably on Mars), but, just like the pool of lava, it would be quickly encased in a layer of frozen water ice. You might have water at the surface, but you would not have water on the surface for any length of time (think polar ice caps in the middle of winter, and you are still way too warm). It is hard to see how extremophiles could evolve in those circumstances, and it is very hard to see how biological material from the Earth or Mars, blasted out by meteor impacts, could reach Titan intact.
What about Venus and Mercury? (Score:2, Interesting)
No... there couldn't. solar radiation was probably important for creating life as we know it, providing that critical energy input to build the first organic molecules. Titan is tooooo far away to get much radiation. Life could evolve there, but if it were a random event it would be MUCH slower than here on earth because it is so much colder over there. So we might have to wait a few more billion years.
And so by that rationale, we should be looking for remnants or indications of life on venus and mercury... or at least some interesting new molecular compounds.
Re:Don't worry. (Score:5, Interesting)
ah, yes, I suspect if you wanted to burn it the suspected water/ammonia mix found in the ice could be a source of oxygen if needed, I also suspect methane would work really well in a fuel cell designed for it.
http://www.nature.com/nature/journal/v400/n6745/abs/400649a0.html [nature.com]
when I said fuel, I didn't say burn.
Re:Joins? (Score:3, Interesting)
Not really, no. Aside from having the necessary ingredients, we don't know how abiogenesis happened, or even that it happened here on Earth. The first microbes might've formed or partially formed in comets that later impacted the Earth and "came to life" down here, or maybe it happened entirely in warm little puddles and tidepools. Regardless, the conditions in which it did happen, or even CAN happen are largely unknown. There very well may be a big difference between what life can adapt to over time versus come about in the first place. There may be extremophiles on Earth that could survive on Mars or Titan right now, but that doesn't mean proto-microbes could have arisen from scratch in those same environments. The Earth extremophiles had the advantage of a wide variety of habitats to evolve from and "move in" to their extreme habitats gradually.
Re:Joins? (Score:4, Interesting)
What many scientists look for in remote planets is chemical imbalance, from an energetic point of view. Chemical imbalance may not be the only result of the existence of life, or even a guaranteed result, it is very reasonable to look for that as both core aspects of life would cause such a chemical imbalance.
A typical aspect of life (at least life as we know it, and what we commonly consider "living") is a mechanism that is doing something with energy: usually storing energy using chemical reactions. As a result there is a lot of matter on earth that is not in a very low energy level, e.g. oil and coal. The ultimate source of this energy could be light (most lifeforms on earth use this energy source - directly or indirectly), but other sources are also possible, think of sulfur-reducing bacteria near hot wells, using sulfur and maybe also heat as energy source. The sulfur getting in that high-energy form thanks to the heat in the core of the earth reducing the sulfur to it's elemental form, later oxidations by the bacteria release energy.
A second typical aspect of life is self-replication. This is a necessity of survival: even if an individual would not age, there are always accidents and diseases that will put an end to an individual. So self-replication is also a requirement. And I suspect that most, if not all self-replication reactions take energy, for the simple reason that self-replication means a decrease in entropy in the matter used to create this copy. Again energy is stored: releasing the molecules and restoring the entropy will result in the release of energy as well.
So for non-life to become life, I'd say a system should be able to replicate itself, and to collect energy from it's surroundings. That I think is the most basic requirement for what one could call "life".
Re:Not necessarily (Score:2, Interesting)
Precisely. So there's little to no chance of finding anything on the *surface* of Titan, which is the only place we have a remote capability to look.
We would need deep sea autonomous vehicles or autonomous digging machines, none of which are within NASA's budget (because we've never built them successfully here on Earth). We've never looked near Earth's core for life either.
It's too cold where we're looking, and we don't have the capabilities to look deeper into the crust.
Moreover, we only ever look for "Earth-like" life elsewhere (read: carbon-based, organic), and have no capacity or machinery to discover or identify non-carbon-based life (silicon, or iron-based), whether it be on the surface or below.
It's a heavily flawed search, which is why it amazes me that we give them money to do it.
Re:Joins? (Score:4, Interesting)
Some of the "building blocks" that may be in comets could even be remnants of life that surrounded sol's parent star that went supernova and gave us all of the elements in the periodic table above iron. Although it's hard to believe any actual life surviving those conditions for those periods of time, it can't be proven to be impossible. Who knows?
If we're talking about extremophiles (Score:2, Interesting)
Re:What about Venus and Mercury? (Score:3, Interesting)
Re:Joins? (Score:4, Interesting)
Abiogensis is fascinating. I hope to live one day to see life created from scratch. Right now, the best we have is interesting speculation.
One workable hypothesis for the natural origin of life is the RNA World Hypothesis [wikipedia.org]. Another is the Iron-Sulfer World Theory [wikipedia.org].
Re:Joins? (Score:3, Interesting)
To expand a little, a better sign of life is an atmosphere that's not statically stable. Our own oxy-nitrogen mix wouldn't stay the way it is without life; there are too many processes that would take the oxygen out. The only thing keeping it in the balance it is is the fact that plants are generating more oxygen at the same rate it's used up, both by animals and by inorganic routes. Any species capable of analyzing our atmosphere could tell that the Earth supports life, even if it weren't life as they know it.