In this lecture, I'm going to spin you a story, that is so plausible
that it's easy to feel like it, it almost has to be true.
We'll see what the story is and, we can decide
at the end if we think it really is true.
A couple of really interesting things that have happened in the last decade with
regard to life on Mars, life, on
Earth in extreme environments, and, interplanetary conditions.
One, is that as we discussed way back in unit one, there's
good evidence that Mars started out at least four times, maybe they
were intermittent times, maybe it was an extended period of times, but
where it was, warmer, and wetter in some places maybe predominantly subsurface.
But maybe, there was certainly places, not
just maybe, but there's certainly places on the
surface, where there were things that looked like,
habitable environments, not inhabited environments, but habitable environments.
Another thing that we've learned in the last couple of decades that if you go pick
up meteorites in Antarctica, occasionally you'll get these
very special ones that come from the moon.
And we get ones that come from Vesta.
And, we even get ones that come from Mars.
Materials are transferring back and forth between Mars
and the Earth, Earth and Mars, all the time.
How does that happen?
Well, imagine giant impact comes in and smashes Mars.
Ejecta goes up into the sky, and some of it actually
goes up, and escapes Mars orbit and rattles around the inner
solar system for awhile, eventually finds itself on an Earth crossing
path, hits the Earth's atmosphere, lands in Antarctica, we pick it up.
You probably remember, almost 15 years ago now when there was this huge announcement
that a Martian meteorite had been found
with, evidence for microbial life inside of it.
And, in case you haven't gotten the picture, in the intervening 15 years.
Pretty much, nobody believed that that was
actually evidence for, Martian life inside that rock.
But, it sparked the interest in studying those Martian
rocks, just to learn what we could about them.
And one of the, I think, really interesting
things about, that Martian rock that was found, was
that it retained much of the magnetism that
it had, when it left the surface of Mars.
Now, when you take something that has, a
remnant, magnetic field like we know about Mars.
If you take something like that and you heat it up, the magnetic field that that
material have will slowly decay away, as all
of the, magnetic little dipoles inside there, realign randomly.
So the fact that this, this Martian meteorite, still had,
a remnant magnetic field, meant that it never got very hot.
It never got very hot, and it was ejected into space in an impact.
That's a little bit surprising.
I, I would have guessed, many people would
have guessed that, yes, you can eject stuff
into, into space, but it's only going to be
molten and solidifying as it gets into space.
But no, unmelted chunks, in fact, substantially unheated chunks,
of the surface, of the planet get ejected into space.
And when that happens, they can eventually land on a different planet.
That's one more thing we've learned in the last
couple decades, or maybe we knew this all along.
Which is, life is persistent.
Microbial life is persistent.
Anyone who's ever tried to disinfect their kitchen,
and keep it clean, knows that this is true.
You can, spray as much bleach as you want all
over it, but eventually the little buggers will come back.
Last couple lectures, we talked about, life in all sorts of environments.
And, one of the environments that we've
tested, microbes, and is the environment in space.
We have left, microbes exposed in space for years in
conditions that are, the rad, there should be radiation damage.
They, of course, have no nutrients, no oxygen.
Brought them back down, and they were easily revived.
Not all of them.
But if there are, a particular class of radiation resistant bacteria that,
that can survive in space for as long as we've left them there.
We now have enough pieces to put together, the entire puzzle.
What if, early on in the history of the Earth, Earth were hit
by a large, meteor and chunks of the Earth flew off into space.
On those chunks of Earth perhaps, would have been microbes.
Not just perhaps.
If you picked up a chunk of the Earth,
anywhere around here right now, you would definitely have microbes.
Those microbes, some of them, could survive the rigors of space.
And they would land places.
Where would they land?
Well, maybe they'd land on Venus.
What happens?
They're fried to death.
It's too hot.
Where would they land?
Well, maybe they would land in the sun.
That's not so good either, but
occasionally, they would inevitably land on, Mars.
And remember, this is early on.
They would land on Mars when it was warm, and it was wet.
And what would they do?
Well, I have to tell you, if you took a rock, with microbes on
it, and you put it in a warm and wet environment on the Earth.
You'd get a lot of microbes.
