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Cosmonaut Anton Shkaplerov suspects an extraterrestrial origin for bacteria found on the exterior of the ISS:
A Russian cosmonaut claims to have caught aliens. Cosmonaut Anton Shkaplerov says he found bacteria clinging to the external surface of the International Space Station that didn't come from the surface of Earth.
Shkaplerov told the Russian news agency that cosmonauts collected the bacteria by swabbing the outside of the space station during space walks years ago.
"And now it turns out that somehow these swabs reveal bacteria that were absent during the launch of the ISS module," Shkapkerov told TASS. "That is, they have come from outer space and settled along the external surface. They are being studied so far and it seems that they pose no danger."
A recent study suggests that interplanetary dust can transport microbes to or from Earth:
Astronomers have long believed that asteroid (or comet) impacts were the only natural way to transport life between planets. However, a new study published November 6 in Astrobiology suggests otherwise.
The study, authored by Professor Arjun Berera from the University of Edinburgh's School of Physics and Astronomy, suggests that life on Earth may have begun when fast-moving streams of space dust carried microscopic organisms to our planet. Berera found that these streams of interplanetary dust are not only capable of transporting particles to Earth, but also from it.
Space Dust Collisions as a Planetary Escape Mechanism (DOI: 10.1089/ast.2017.1662) (DX) (arXiv link above)
(Score: 3, Informative) by Immerman on Thursday November 30 2017, @06:49AM
Certainly change (and thus evolution) is inherent in life as we know it, and I've never heard anyone make the claim that it only happens on geologic timescales - it happens in tiny increments with every birth and every death. But evolution just causes change - on its own it's extremely unlikely to cause two unrelated species to have any substantial similarities to each other.
Efficiency matters because that's what drives convergent evolution - sharks and dolphins have extremely similar body shapes because that is a fairly optimal shape for animals that need to travel quickly through the water - physics guides two completely different species to the same basic conclusion because it's an extremely efficient design. Photosynthesis on the other hand is nowhere remotely close to an optimally efficient design, and so if we find alien "plants" that use photosynthesis we'd expect them to use some other mechanism to perform the same basic function - efficiency would not guide a different species to find the same solution.
And efficiency matters because it increases your ability to survive and prosper, which is the driving force behind natural selection. Start with two almost identical seeds planted side by side, the only difference being that one has a mutation that makes it twice as efficient at photosynthesis. That difference means that from the moment they push their first leaf into the sun, the mutant is collecting twice as much energy from the sun as its twin. That means it can grow its leaves faster, absorbing even more sunlight, and grow its roots faster, absorbing more water an nutrients from the soil. And the bigger and faster it grows, the fewer resources are available to its twin. Even if the twin doesn't get starved out entirely, the mutant will be able to afford to produce a lot more seeds, and all the offspring that inherit its mutation will have a similar advantage - after a thousand generations there probably won't be any of the original non-mutant plant left - it will either have been outcompeted into extinction, or have developed new mutations that give it an advantage in some other way, possibly even letting it migrate into an ecosystem where the original mutants can't survive to compete in the first place.