"Aliens" could mean your mythological "little green men"
in their "Flying saucers," but in this context they
could be bacteria.
If we found alien life, even the most basic form of life,
we would have a model of evolution that we could compare
ourselves to.
"Ourselves," meaning life here on earth.
The biggest obstacle, really, is "Common Descent." I mean,
look at the earth. There's a more than passing similarity
between, say, the skeleton of a dinosaur and that of a
human. And that makes sense because of "Common Descent."
That's why we both have a pelvis, and vertebra. We both
have four limbs and, yes, we even have five toes, digits
to be more accurate, though in THIS dinosaur or THAT it
grew into part of a wing, or got really small or even
seems to have evolved away entirely but, we all share
that common descent...
Why is that a problem?
Well. If any shade of "Panspermia" is correct then we
do have "Common Descent."
On the bright side, if any shade of Panspermia is correct
than life in the universe has to be relatively abundant.
Even Red Dwarfs might be hosting an abundance of life,
despite possibly being quite unstable. Very large,
complex, technological life may be a problem, but not
simple life form, perhaps beneath the surface or submerged
in an ocean. Maybe a life that breeds very rapidly and so
can recover very quickly in the face of instability...
Still, if only 20% of the solar systems host life, or
15%... 10%... that's still quite a bit.
Going by NASA and "Confirmed" numbers, with life in only
10% of the solar systems in our galaxy, we're looking at
upwards of 400 life bearing worlds.
Now, if panspermia is correct in any iteration then I
would expect the number of life-bearing worlds to be very
small, and the number of technological civilizations to
be minuscule.
So, I say now, as I've often said before, what we need
more than anything is investigation into panspermia.
Yeah there's been /Some/ work done, but we need some
conclusive work. We're talking conferences, plural, where
brilliant men argue passionately, perhaps throwing
furniture at each other, all over what they believe a
test of panspermia needs to do -- what would be
convincing. And then we've got to do those tests, all of
them, prove it is possible or eliminate it as a
likelihood...
What I'd love to see is about 80 rocks, or very rock like
material, bristling with life, flung out of the
atmosphere towards various destinations... the moon...
Mars... a trip around the solar system before crashing
back to earth... etc.
But to do this we need to know with certainty whether or
not their target destination already hosts life.
We can't crash life onto Mars if there's life there!
So that puts a damper of things...
We can still launch such objects into space, speed them
around the solar system -- some for a year, some for
decades -- and then crash them back here on earth. If
anything is alive inside our rock, it should have no
problems growing.
NOTE: We're need to genetically alter this life. Not
to change how it lives or its ability to survive, but
so it has genetic markers identifying it as our
bacteria and not bacteria in nature crawling inside of
the crashed rock, having a time...
-- https://jtem.tumblr.com/tagged/The%20Book%20of%20JTEM/page/5
Why aliens matter