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bsima

yay, likelihood that we are martians just went up a few basis points

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It seems very low likelihood that a life-bearing chunk of Mars arrived and seeded life here.

What are the chances that some type of single-cell critter(s) from Mars were robust enough to:

1) Survive the trip here with the extreme cold of space, AND

2) Survive the searing heat of entering earth's atmosphere, AND

3) Survive conditions on earth, when they were adapted to the martian environment

And that's all premised on a meteor strike on Mars ejecting something with enough velocity to not only escape Martian gravity, but then miraculously happen to score a direct hit on earth (a miniscule angular target to hit).

This combination of low probabilities seems to result in an explanation of lower probability than the alternative (life originating on earth) that it's attempting to explain, and of course life originating on an earth-like Mars in same time frame it would have needed to develop here (or maybe also did develop here) doesn't add much more than historical interest.

Curious why there is much less interest in the Pleiades, which is made of all of our same material and is very likely a "fork" of earth formed after the original mass that later became earth and moon colliding with another body in early history.

https://en.wikipedia.org/wiki/Giant-impact_hypothesis

Perhaps, but given how sterile the moon appears to be, it's not obvious why the Pleidas would be any different, even assuming they were created by the same potentially life-seeding impact.

I can see the purely historical interest in knowing how the earth and moon were formed, where our water came from, where terrestial life originated, etc, but it seems (maybe I'm wrong?) that a large part of the interest in extra-terrestial origin of life consideration is from people who don't want to believe that life is all-but-inevitable in the right conditions and therefore presumably did originate here (and very quickly after earth formed - within a few 100M years). However, if creation of life is an extremely rare event, then the likelihood of it having spread from such a rare source to any other compatible planet seems vanishingly small!

Going up a few basis points would be like increasing the odds 1,000,000x.

I'm not opposed to the idea that life began on Mars, and, I don't know, through some mass ejection a chunk of lifelike stuff landed on earth and seeded it. But it seems like a much harder path to take than to just form life on Earth from the start.

Asteroids as originators of life, that impacting both, would be the more likely “root cause” of having life on both planets

Even more interesting would be the discovery that life developed on Mars and on earth. And whether that happened around the same time or at different times.

Well, that was H. Beam Piper's premise in his "Terro Human Future" and "Paratime" stories --- see the wonderful novella "Omnilingual" and see the story "Genesis":

https://www.gutenberg.org/ebooks/18105

Anyone remember the title of the short where they explore an ancient martian city and find a periodic table that serves as a Rosetta stone?

That's "Omnilingual"

See the nicely updated version at:

http://vrici.lojban.org/~cowan/omnilingual.html

Oops, sorry for the spoiler

Or, why aren't Martians from Earth.

As much as I like the idea conceptually for movies. That life on Earth came from Mars still doesn't explain how life started on Mars. It just moves the location, the mechanism is still tbd.

Life arose on Earth really fast after the surface stopped being magma. Since Mars cooled down faster the idea is that it could have spent 100 million of year developing bacteria which were then seeded the Earth as soon as there was liquid water there.

While in general the argument may hold that life evolved too fast, your numbers are off. 100 million years is just about the minimum estimate for the emergence of life on Earth. If Mars has a longer timeline it should be closer to 1 billion years between solidification and emergence of life.

You're right that my numbers are off. I'd bee thinking of the end of the Late Heavy Bombardment 3.8e9 years go, but there's some suggestive evidence there was liquid was on Earth's surface 4.4e9 years ago. And the earliest bacterial fossils are from 3.5e9 years ago, though goodnesss knows how long it took bacteria to make colonies that ended up making fossils to survive to the present day.

All this has happened before, and it will all happen again.

Yeah I never liked the panspermia as a solution to how life started so quickly on Earth because it just kicks the can down the road. But hey it has been speculated that DNA may be almost 10 billion years old https://phys.org/news/2013-04-law-life-began-earth.html. But this is just a thought experiment, I am unsure if we know how long it takes for DNA to double, nor do we know if the rate would be constant over time. For example if proof reading mechanisms evolved later thus slowing down the rate of change. But it's fun to think about. Too bad Google search is so useless I used to be able to go down these Rabbit holes finding all sorts of information but now it's almost impossible, Google just gives superficial AI answers these days

Recall that no one could reconcile billion year ages for the earth with it not having cooled far more - until the discovery of radioactivity.

If we can demonstrate that life moved from Mars to Earth then the most likely explanation for life on Mars is that it also got there from somewhere else.

> Or, why aren't Martians from Earth.

Mars's gravity is much lower, so it's much easier for an impact to accelerate rocks to escape velocity.

I agree with the rest of your comment though.

> yay, likelihood that we are martians just went up a few basis points

I bet there's some non-life explanation, probably having to do with weird chemistry that happens on Mars over long periods, but is not so significant on Earth.

The article says the Earth-chemistry that creates these minerals involves the oxygen in the atmosphere, but it doesn't seem plausible to me that Mars's atmosphere was ever oxygenated. It took billions of years for the Earth's atmosphere to become oxygenated, and it sounds like Mars lost most of its atmosphere fairly quickly.

Someone else brought up that superoxygenator salts form in the upper layers of the soil due to the high UV radiation on the surface. It's possible the oxidation here is due to those superoxygenators but the original manganese is due to the ancient lake. So basically manganese is embedded in the rock while there's a lake, then the lake dries up as the atmosphere disappears. And finally the UV gets strong enough to create oxidizers in the soil which react with the manganese.

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