There is no edge to the atmosphere, and therefor I expect there would be a gradual reduction of concentrations of bacteria as we ascend into space. Logically anaerobic bacteria should be able to obtain its energy from the sun and nutrients from whatever scarce but available organic floating materials. Cosmic rays and high energy particles could damage DNA, but there might be someway life could protect itself against them. Could it be that bacteria is evolving/ has already evolved at the edge of the atmosphere to live in space?
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$\begingroup$ This is more a world building question, where I suspect it has already been answered. $\endgroup$– James KJan 27, 2019 at 8:25
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3 Answers
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Currently there is no life that we know of that evolved in, or can survive for prolonged time in a vacuum.
To say 'Life in space is possible because there is anaerobic life' is a completely wrong point, that ignores the effects of vacuum on life.
Sure, there are extremophiles that can survive for a limited time in space (see also this list) when going into hibernation modes. However all life as we know it needs liquids and/or gases to survive. Those would evaporate once the cell/water bear would become active again. Activity is necessary to sustain and multiply life, so no, nothing that we know of can stay active and alive in space.
Cosmic rays and high energy particles could damage DNA, but there might be someway life could protect itself against them
Until life comes up with such mechanisms, we just don't know. The problems with liquids and gases evaporating would need some tougher solutions even.
Bacteria are also pretty heavy 'particles' and therefore cannot float anywhere near the 'edge of space'. There are reports of bacteria in the stratosphere, but that requires already strong upwinds to put them there.
answered Jan 27, 2019 at 12:58
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$\begingroup$ You should point out that "anaerobic" means "living without free oxygen," not without air. $\endgroup$ Jan 28, 2019 at 19:05
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$\begingroup$ @CarlWitthoft: Yes, you're right, but you've already done that now ;) $\endgroup$ Jan 28, 2019 at 20:56
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Some bacteria already have evolved to survive in space. They merged with other bacteria (to form eukaryotic cells), formed large structured colonies (or "organisms") with developed "brains" which were able to design and build rockets and space stations. It took rather more than a billion years of evolution to go from a bacteria to space dwelling humans.
Space is very hostile environment, bacteria exposed directly to space will eventually die. They could remain viable for some time, but in the absence of liquid water, growth is not possible. It is conceivable that bacterial spores could survive for an extended period, if embedded in rock.
We cannot answer this question, as nothing that we know of has evolved in a vacuum.
Survive? Yes. Thrive? No.
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$\begingroup$ Thanks James. I fully take your point that bacteria has already evolved in space, and I appreciate the enormous challenge for bacteria to thrive without a liquid solvent. However I am, like you, optimistic about its ability to survive in the form of spores or the like, and then drift towards other planets or even other solar systems. I just wonder if such process is already occurring at the top layers of our planet, perhaps seeding the atmospheres of other planets such as Venus which has good conditions for life in its upper atmosphere, or perhaps some of Jupiter's moons. $\endgroup$– Matt DeeJan 27, 2019 at 10:22
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1$\begingroup$ Quite clearly bacteria have not evolved in space. Other than trying to be clever and making a semantic point, this answer could highlight that we cannot answer this question, as nothing that we know of has evolved in a vacuum. $\endgroup$ Jan 27, 2019 at 12:41
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$\begingroup$ And yet tardigrades can withstand hard vacuum, so even your humorous point is wrong. $\endgroup$ Jan 28, 2019 at 19:05
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$\begingroup$ Tardigrades can survive, in a dormant form. They cannot thrive. They cannot reproduce, find food, move, or do most of the things that "living" usually means. Only one species can live in space. And it evolved from bacteria. $\endgroup$– James KJan 28, 2019 at 20:33
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Given that we've found bacteria thriving inside "solid" rock a couple km straight down, living on local sulfur and heat, there's no overriding reason that something couldn't evolve on some rock (planet) of sufficient size to hold some heat in, but without any need for an atmosphere.
If you were specifically asking about free-floating life that survives entirely on solar irradiance, then no, but more because of a complete lack of various elements (let alone long organic chains) in most of space. Veering off into world-building, imagine my intra-rock bacteria slowly growing to the surface, forming a protective layer of dead relatives which absorbs irradiance but seals against vaccuum, and sometime later a volcanic eruption launches the entire magillah into the vacuum (and the protective layer manages to envelope the entire colony). Highly improbable. You'll need The Heart Of Gold here.
answered Jan 28, 2019 at 19:07