I'm almost completely certain that there is alien life somewhere out there in this vast universe. The question is, can we find it or is the hay stack too big for us to find the needle? And even if we could find a life-bearing planet, could we even observe or interact with it? Because of how long it takes for light to reach us, any life bearing planet we discover could already be desolate by the time we see it.
Everything we know about life just from our own one example here on Earth is that once it gets started, it gets into
everything. Think about some of the extreme environments that even within the last twenty five years or so, biologists would have all but ruled out as habitats -- and yet they host microorganisms. Where we used to have a very specific list for life: You are not allowed to view links.
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Login, liquid water, temperatures within a particular range, solar/tidal/geothermal energy sources. Now it's beginning to look like a solvent (not necessarily water) and an energy source could be all it takes to build an environment.
So I'm bullish on (very simple) life within our own solar system. I'm optimistic for the depths of Hellas Basin, where Martian atmospheric pressures
just allow for the presence of liquid water. I'm also optimistic about the remains of the Martian Oceanus Borealis (if it proves to have existed; there are tantalizing clues but nothing definitive), and Martian permafrost, and the Martian polar caps. Got to go where the water is, at least on Mars.
But Mars is kind of low-hanging fruit, life-wise. Enough material has transferred between the Earth and Mars over geologic time that it would not be surprising to find Martian life is DNA based either because it was contaminated by Earth life... or that Earth life started on Mars and found a more stable and suitable environment here.
So the
really interesting places are Ganymede and Europa at Jupiter, and Enceladus at Saturn, because any life there would almost have had to independently start there. While it's relatively easy to get impact ejecta from Earth to Mars, it's all but impossible to get it much further out, or get it from there to here. I know I had an article on that, but I can't find it and I will keep up the search until I do.
Target Number One
must be Enceladus. It's effectively isolated from interplanetary contamination from Earth (and Mars), and thanks to Cassini's flythrough of the Enceladan geysers, we're confident there should be active You are not allowed to view links.
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know those are viable habitats. Europa is close enough to Jupiter that it is expected to have them too, as a result of tidal flexing, but Enceladus so far as I know is the only extraterrestrial place we have direct evidence to indicate them.