

Proof of life on Mars 'to come this year' - prat
http://www.scientificamerican.com/article.cfm?id=proof-of-martians-to-come-this-year-2010-01

======
thaumaturgy
I assume that the investigating scientists familiar with the project have
reasons to conclude that the bacterial fossils definitely originated from
Mars, given that:

> _The stones are known to be from Mars because gases trapped inside them
> match those in rocks examined by probes on the red planet. They were blasted
> out of its surface by asteroid impacts and then drifted around the solar
> system for millions of years before falling to earth._

I would tend to more conservatively conclude, "some meteorites resembling
Martian rock have been found to contain fossil evidence of bacteria."

i.e., it is also possible that the rock was contaminated while in space, or
that it didn't even originate from Mars, but from conditions which simulated
Mars.

I'd love to hear definitive proof of life, or former life, on Mars.

~~~
pjkundert
Isn't it unlikely that Mars would _not_ have bacteria, given the tons of
earth-sourced meteorites that have bombarded it?

~~~
jerf
In my opinion, if we discover some life on Mars, but biochemical analysis says
that it is compatible with Earth life (uses DNA, same chirality on the
molecules, clear analogs with Earth life in the design, probably could even
find an ancestor), we have to stick with the theory that Mars did not
originate life. If Mars did independently originate life, it should be clearly
obvious.

"Mars is able to natively host small amounts of Earth-derived life" is still
interesting and still says some things about the prospect of life in the
universe, but I don't think that would really add much to what we already
know, the way a truly independent branch of life would.

Good cases have been made that RNA and DNA may be the only suitable bases for
life, which would imply that finding those wouldn't be absolute proof, but
there's enough other stuff in Earth's base DNA catalog that should be
different that sequencing should immediately reveal a different origin. (Not
to mention the different starting conditions should result in other choices
for basic functioning.)

(It is not necessary that RNA/DNA be the only choices for life; it simply
means that if the arguments are even partially true it tweaks the probability
that truly foreign life might still be RNA/DNA based up. But above that level
I'd expect significant differences; "ontogeny recapitulates phylogeny" may be
false at the macro level, but billion-year-old decisions of life are still
written into our DNA at deep levels. Truly independent life should have made
at least some different decisions.)

~~~
thaumaturgy
> _If Mars did independently originate life, it should be clearly obvious._

Why?

~~~
jerf
For the reason I talked about in my third paragraph, for starters?

~~~
thaumaturgy
Well, thanks for that, but I did read your entire comment and it was an honest
question. Your third paragraph, for starters, includes a lot of "should" and
handwaving.

In what ways were the starting conditions different?

Earth underwent radical changes in its environment in its early history. Did
those changes -- from a methane to an oxygen-rich atmosphere for example --
result in radically different RNA or DNA sequences for the bacteria from each
epoch?

Why should different starting conditions result in different forms of basic
DNA anyway? Wouldn't the basic problems of evolutionary viability be the same?

There is indeed lots of stuff in Earth's base DNA catalog -- including some
terrestrial critters that would do just fine on Mars, which would suggest that
they could have independently evolved there. Tardigrades are one such popular
example.

Your very last sentence is, "Truly independent life should have made at least
some different decisions", but there's that word again: _should_. So, again:
why?

On a completely different side note: this is part of the reason that anti-
intellectualism is so rampant in America today. Those that have the
combination of both ignorance and intellectual curiosity too often get met
with sarcasm and indifference by people who then complain that nobody takes
their opinion seriously.

So thanks for that.

~~~
jerf
"Did those changes -- from a methane to an oxygen-rich atmosphere for example
-- result in radically different RNA or DNA sequences for the bacteria from
each epoch?"

It certainly left an imprint. I can't google up a concrete reference, but
there are genes in our genome that come from the era when there was a lot more
methane in the general environment meant to essentially put the organism in
hibernation when they temporarily encounter a certain type of high-methane
environment.

How "radically different" it is depends critically on your definition of
"radically different". It is certainly _detectably_ different, which is more
to my point. Sequencing a Martian lifeform without those markers would stand
out and provide very strong evidence that they don't come from a heritage that
had that in its past. (I have no idea how widespread those genes are, so I
don't know how much Earth life that would eliminate as possible ancestors.)

"Why should different starting conditions result in different forms of basic
DNA anyway? Wouldn't the basic problems of evolutionary viability be the
same?"

Genes code for chemistry. Different starting chemistry implies different
solutions for problems encountered early in life's existence. Not to mention
there are multiple solutions to problems, and the odds of life choosing the
same initial solutions are just negligible.

You can see this if you play with evolutionary programming, and look at the
resulting programs. You can see it in conventional genetic programming, too,
if the problem has many unrelated but equally appropriate solutions. In fact,
you can see it in that music link we had a couple days ago. Any given
evolutionary run tends to create a population that congregates in a relatively
small part of the space, regardless of how many other viable paths there are.
Evolution's ability to escape local optima is greatly oversold in the popular
press.

"So, again: why?"

Because the probability is so long against it. Why would two 100-fair-coin-
flip series ever be the same? It's theoretically possible, but you'll never
see it.

Basically, what my point boils down to is that a Martian life form won't fit
into the phylogenetic tree of life. See
<http://www.talkorigins.org/faqs/comdesc/phylo.html> , which doesn't relate
the tree directly to the topic at hand IIRC, but you should see how it relates
with some thought. Something that does fit into the phylogenetic tree very
probably came from Earth.

"Those that have the combination of both ignorance and intellectual curiosity
too often get met with sarcasm and indifference by people who then complain
that nobody takes their opinion seriously."

I call foul. You grunted a one word question to a pull quote, a "why" that I
answered two paragraphs later. If I had had no answer, I would have
understood. _This_ post of yours is not unreasonable, asking for specific
further elaboration, but just "why?" didn't cut it. (You prompted me to
remember the phylogenetic tree page, which puts my point on much firmer
footing, which I appreciate.)

Also, since I can smell the "But you can't prove any of that" coming, I would
say, prove for me that life _will_ exactly evolve the same way on Mars that it
would on Earth. Actually, I explicitly won't hold you to that, because we're
_all_ speculating and handwaving. Even a biochemist of fifty years practice is
just speculating and handwaving. Until we start building artificial life forms
and start really exploring the space of "valid life forms" neither you nor I
nor anybody have the actual data in hand. (We're just barely at the threshold
of artificial life and by no means have we even begun exploring the space of
possible life.) However, if you go back to my original post, I actually make a
judgment call on _probabilities_ , so it's not like that's news to me that it
won't be proof.

~~~
thaumaturgy
Thanks for the explanation and link. I wasn't familiar with the term
"phylogenetics" -- although it's not too far removed from concepts in high
school biology.

> _Also, since I can smell the "But you can't prove any of that" coming..._

Not from me. I just wanted more information, not an argument.

------
Eliezer
If anyone actually believes that, I'd like to bet with them about it.

~~~
amichail
At the very least, this would result in quite a lot more spacecraft going to
Mars.

This could also have a rather negative effect on religion.

~~~
byrneseyeview
_This could also have a rather negative effect on religion._

I only ever hear non-religious people say that. Very few religious people will
say "If you proved that, my faith would be shaken."

~~~
DanielBMarkham
It's a cultural myth. Western religions have dealt with "outsiders" and
"aliens" for hundreds of years and have done just fine with it. New life
forms, intelligent or not, will not change much of anything.

In fact, for a religion to have been successful over the millenia implies a
high degree of adaptability. Otherwise we wouldn't have just gotten through
celebrating Saturnalia, I mean, er, Christmas.

~~~
amichail
The most recent things that have hurt religion are the web and 9/11. This will
be the third.

We are talking about the greatest discovery that could be made. It is one that
will make billions rethink their role in the universe. It will make them
wonder about evolution, whether their God guided it and if so to what degree.

~~~
byrneseyeview
In the time since you made that comment, someone gave birth, and _that_ made
them rethink their role in the universe. Vague discoveries of space bacteria
won't do it.

~~~
cglee
Why are you so certain of this? I grew up dominated by Christianity. It wasn't
until 14 that I saw a UFO magazine insinuate that humans came from Mars. True
or not didn't matter - what I remember from reading that was that my faith was
shaken to the core. That day, I learned to never base your worldview on
something so tenuous that a new discovery could topple it. That experience
sent me on a journey to solidify my understanding of the world, and in the
process, has made me less of a 'hardcore' Christian.

~~~
Eliezer
> I learned to never base your worldview on something so tenuous that a new
> discovery could topple it.

What? I'd just call that "learning from evidence". I believe plenty of things
that a new discovery could topple and there's nothing wrong with that, so long
as the new discovery hasn't already happened. You can't update on evidence
that could arrive but hasn't arrived.

~~~
cglee
I'm talking about basing your worldview, not what you currently believe.
Worldviews are things people attach significant identities to, and internalize
to form the foundations for the rest of their beliefs.

If there's nothing you can think of that can topple you, then kudos, you may
have reached enlightenment.

------
asmithmd1
The discovery of distinct plumes of methane that peak in Martian spring and
Summer are to me strong evidence that something biological is going on:

<http://www.nasa.gov/mission_pages/mars/news/marsmethane.html>

The more seasons we see this pattern happen the less likely it is some
volcanic/geological source.

------
wrs
The current issue of SciAm has an article saying "nanobacteria" (as
"fossilized" in Mars meteorites) are just crystal formations that look a lot
like tiny bacteria. The authors demonstrated growth of "nanobacteria" in
solution.

Tiny online excerpt: [http://www.scientificamerican.com/article.cfm?id=the-
rise-an...](http://www.scientificamerican.com/article.cfm?id=the-rise-and-
fall-of-nanobacteria)

------
motters
I remain skeptical about anything found on earth, since life is so pervasive
here. Even if the meteorites do contain fossils it might be possible that
their chemical composition just happens by mere coincidence to be similar to
that of Mars. I'd be much more persuaded if a rover on the planet was to find
fossils, or if a sample return mission was found to contain fossils.

------
herdrick
Unlikely. The photos we have already are _almost_ good enough to definitively
say if those formations are biological, right? What are the chances that some
given biologically formed nodules would be right at that size threshold?

Besides, I've talked to geologists who say those rocks look perfectly non-
organic to them.

