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All life (as we know it) depends on carbon. But most models of Earth's formation can't explain how the crust has enough carbon to support life. So where did it all come from?
A colossal smashup with a Mercury-like protoplanet some 4.4 billion years ago, suggest researchers from Rice University and Woods Hole Oceanographic Institution in a new study published in the journal Nature Geoscience.
Most scientists agree that about 4.5 billion years ago, Earth was covered with hot magma, and as it cooled, most of the heavier metals near the surface sank deep into the planet. Iron alloys bonded with carbon and sulfur, pulling both into the Earth's core, and any remaining carbon would have vaporized into space from the extreme heat, argue the scientists. The only way to keep carbon and sulfur near the surface is to bring some from a planet that formed differently, they say.
A different story reported last week that scientists have identified fossilized stromatolites that date to 3.7 billion years ago, or 700 million years after the worst day ever for the young Earth.
(Score: 2) by tibman on Friday September 09 2016, @02:30PM
It seems to me that if life is that difficult to start then we should probably help spread it.
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(Score: 2) by Immerman on Friday September 09 2016, @03:27PM
I tend to agree. The problem, especially with Mars, is that we don't actually know that yet, and it may have its own ecosystem already. Probably mostly underground, though the few attempts we've made to detect evidence of surface life directly have come back tantalizingly inconclusive. If we introduce potentially invasive organisms though, then we run the risk that native life may be wiped out before we get the chance to study it. Even if there is no native life, an invasive organism that flourished could still destroy a great deal of chemical geological evidence that would offer insight into the formation of Mars.
There's plenty of evidence suggesting that Mars may have been far more hospitable to life in the past, and if life was ever established there then some of it is probably still there. Even if there's nothing but microbial life, it could still be *incredibly* informative to study, especially if it's arose independently there, in which case it would likely be extremely alien - based on different amino acids at the very least, and quite likely with some completely different information-carrying mechanism rather than DNA. Even if it was colonized by earth organisms millions or billions of years ago (or more likely vice-versa, Mars would have cooled and been hospitable to life formation long before Earth), you've got all that time worth of divergent evolution introducing things we've never seen before. Less informative on what truly alien life can look like, but probably far more information with practical applications. Like having a whole new Amazon of strange and exotic biochemistry to draw on for medical and industrial purposes.
So mostly, we would just like to study Mars as it is before infecting it too thoroughly. Though I suppose there's also a slim risk that we introduce some fringe Earth microbe that can't really compete with everything else here, but manages to thrive alone on Mars, building to densities that make it hazardous to future Mars missions - be it an infectious agent that can't be fought off when the initial infection is a million times more numerous than would be encountered on Earth, something that excretes acid that eats away at habitats and machinery, or even something relatively harmless like lacing the environment with potent hallucinogens. Someone tracks the wrong dust back into the habitat, and next thing you know someone's sabotaging the outpost to keep the Martian bogeymen from invading Earth.