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Language: en
And as much as I'd love to tell you that
we scientists come up with like silver
bullet answers like the bullseye on a
target, that's not how we search for
life.
>> Let's let's let's so so for example, we
talk about early life on Earth, there
are these zirkon crystals where they
look at carbon isotope ratios. Totally.
So let's talk about signs of life. So
when when I talk about what's different
about Earth's life is that it's based in
sunlight. What I'm getting at there
without saying it is that most of the
oceans are under miles of ice, miles of
rock or a super thick atmosphere,
whereas we have this little tiny thin
atmosphere. Right. Completely.
>> So if I wanted to look for signs of
life, you can do it both remotely and
you can do it, you know, from a
distance, right? And you can do it by
sending a probe there. Yeah.
>> Right. And aside from finding things
critters crawling around or skeletons.
>> Sure. What are the different ways that
you could potentially tease out that
there is microbial life? Because I'm
guessing that that is the standard if if
life exists nine times out of 10 just
like on Earth. If you visit Earth
throughout it history, most of the time
you're only going to find microbes.
>> Yeah.
>> Right.
>> How do you go about what are what are
the different indicators that you could
possib that you guys have thought of so
far?
>> Yeah. So, a bunch of scientists like
myself, um, we study, uh, life on Earth
through kind of, I'm going to call them
different lenses. So, some of my
colleagues think a lot about DNA and
genomics. And of course, if you find a
molecule like DNA
>> and if you can be sure you didn't drag
it to Mars with you,
>> it's pretty cool, right? So, that's
because that's like information in a
molecule.
>> So, so finding a a a molecule, a life
molecule.
>> Yeah. that is unquestionably a life
molecule.
>> Yeah. And let me give you a kind of
little bit more there. Some of my
colleagues are asking like how small
does a mo can a small a molecule be
before you're sure it's not life or
another way of putting it is like if I
find let me take acetic acid which is
vinegar.
>> Yeah.
>> If I find vinegar molecules on Mars
doesn't mean anything
>> because we like you got all these like
little organics floating around in
space. But what if you find um 10 things
strung together? Can that happen without
life? What if it's 20 or 100?
>> So, what I'm getting at here is there's
something about the complexity
>> that can give us a hint as to whether or
not this was produced by a living thing.
You know, your your DNA is like millions
of little bases strung together. That's
cool. That's a lot of complexity
complex.
>> So, if we found something that's a
million bases long, like come on. Like,
that's pretty clear.
>> So, that's one lens. People like myself,
we think a lot about energetics as you
kind of gathered from me talking, right?
>> One way I define life is like it's got
to keep itself at disequilibrium from
the environment. And if I had those Star
Trek triquarters, I could walk around
and poke at things and be like, "Oh,
look, that's the right mix of different
elements all wrapped up in a little
bubble that it may have been at some
alive at some point." Right.
>> But this the challenge with that, what
makes it hard is if I kill you, and I
don't mean to be creepy here, but like
if I Well, let me back up cuz that's a
bad thing to do on your show [laughter]
in 2025.
>> I know.
Can we edit that out? No. So, if if
something dies and we bury it, right,
>> it goes to equilibrium over time and we
can no longer tell it's there. Yeah.
Right. So you take let's just I mean if
you take a piece of cheese and bury it
in your backyard and over a century you
go back like you can't tell that a piece
of cheese was there. Those chemicals
diffuse they get washed away and all
that stuff. You see where I'm going with
this? So it's when we go and look for
life on Mars and if it's you know up two
billion years old. We're not going to
find an intact cell with all those
elements in there. So my disequilibrium
model is tough.
>> Yeah.
>> So and so is looking for DNA. So the way
we approach this is we take all of these
five or six or 10 different ways and we
try to overlap them. If I got a little
bit of evidence that leans in the right
direction and someone else has a little
bit, you can imagine starting to say,
"Okay, this is more consistent. We got
five, six, seven, 10 lines.
>> It becomes more than a coincidence when
you have it. That's it." Cuz right now
we got two minerals.
>> Yeah. Yeah.
>> That's where we're at.
>> Two minerals. [laughter]
>> It's a good sign.
That's not your millions of uh
>> things strung together. Oh my goodness.
So,
>> what would conclusive life look like
then at the microbial level?
>> Um,
>> you know, if we were going to Enceladus
and flying through the plumes
>> and we took samples, right? What What
would it
>> I mean it that might be a weird question
because there's a point where you
actually have living critters. That's
clearly conclusive, right? But
non-living. Well, let's let's uh let me
uh so what I'm going to say is uh is is
a is a bit halfbaked again, but check
this out. Like if you look at Earth, you
have all this oxygen gas in the
atmosphere.
>> And just like you alluded to earlier,
oxygen is an element, you know, as in O
the element O like that's all over the
place,
>> right?
>> But it's that O2 gas that's kind of an
interesting fingerprint because it's
like microbes did that.
>> Yes.
>> Right. And then there's this there there
are all these different kinds of
isotopes. And just as a reminder to
those listening in, that's like when you
have something like carbon, uh, you got
three different flavors of it, right?
There's like a carbon 12 and a 13 and 14
and that has to do with the number of
these things called neutrons as we know
sort of stuck to it, right?
>> So sometimes living things discriminate
against one or the other and they
actually leave us, we're going to call
it an isotope fingerprint. Yeah.
>> So when I look at methane on Earth to
give you a clear example and I work with
a very large mass spectrometer in my lab
for example, I can tell methane made by
microbes versus methane made by
volcanoes.
>> Oh, really? Because Mars is making
methane. It's methane on Mars. Yeah.
>> Yeah. But in order for us to tell if
that methane came from In order for us
to get closer to figuring out if it's
living things or dead stuff, we need to
look at the isotopes. And that's hard to
do.
>> You can't do that remotely. You got to
need a sample. So I actually I'm not
really sure if NASA has that tool. I was
maybe that's something you and I can
look look up after this. But I don't
know that there are really high
performance isotope analyzers like on
Perseverance. I don't think that's the
case.
>> How do you is it just about by the mass?
It just weighs more.
>> Yeah, it's a mass. So you have to that's
what mass specs are good at. And so
that's the brilliance of sample return.
Like we got to get samples back from
Mars.
>> I would love to see us do this
internationally and really put all of
humanity's uh ingenuity to looking into
what is the evidence in this rock,
right? But that we have to bring them
home. I don't think we can do it on
perseverance.
>> If there was life on Mars, what does
that tell us about Mars?
>> I think broadly speaking, uh it tells us
that there may have been a time in the
past where Mars had uh maybe been in a
position where we had liquid water. And
it's pretty it's looking like there
probably was liquid water on Mars.
and I don't know enough about the core
of Mars, but if there's any heat coming
out from Mars in the past or now,
>> if you have that temperature gradient,
which you mentioned, that's cool,
>> Hakee,
>> cuz now if you got liquid water and you
got some heat,
>> right?
>> It's not like the elemental composition
of Mars is that different than Earth. I
mean, it's not exactly the same, but
>> I wouldn't be surprised. I wouldn't be
surprised if we found microbes. I just
wouldn't be. It seems like we keep
getting teased with these, you know,
there was the Martian meteorite with the
microbes in it. There's the methane on
Mars. There's Oh, there's water. Look at
there's still remember the crater where
you can see the seasonal changes. Then
there's the water under the solar under
the the the polar ice.
>> Yeah.
>> All these little teasers.
>> Yeah. Teasers.
>> Yeah. You know, when are we going to get
the you know, I want a catfish for Mars.
Like when are we going to get to the
real life? waiting a while smoking gun,
[laughter]
>> you know.
>> Yeah. So, there's a So, yeah, it's going
to be a while for that catfish, hike,
but I'll say,
>> look, I think that here's here's a a
question for for frankly all of us, all
like all of humankind. Yeah,
>> we're we we we a lot of us want to know
this answer, right? A lot of people do.
And if we do, we should be asking
ourselves, what is a better way to get
more conclusive evidence? And so I'm a
big fan of this sample return idea
>> because so many of the tools we have on
Earth, we can't put on spacecraft
cheaply or easily or practically, right?
>> But if we can get a sample back,
>> that changes things. And again, this
just is something that I think is in the
heritage of all of humankind. We should
look at this together and figure it out.
To me,
>> if we get and if I could wave a magic
wand, what I would love to do, you're
talking about probes, I'd send out
probes to six best candidate places on
Mars or maybe 10. Let's grab a sample. I
want to look at them and then
>> I'm not going to promise everyone we're
gonna find life or not, but I'll bet you
if we came back with six or 10 samples,
we would have a much better idea if
there was life.
>> And we'd have a much better idea if
there wasn't. We walk away from it.
>> How about this? How about this? Instead
of sending
>> rovers, what about we send a team of
geologists to six sites on Mars?
>> You know, that's three geologists.
>> That's a that's that's that's a So, I
think this is a cool idea. I also part
of me is like can we do this with
robots? This question came up during
Apollo, right? Like do we send people or
do we send robots,
>> right? Because at the time when they
were thinking about sending humans to
the moon,
>> this debate was raging. But I think
Hakee people were like
>> sending people to the moon is more than
just grabbing rocks, isn't it?
>> Yeah.
>> And so sending people to Mars, I get it
right.
>> So if you really just want some samples,
send some robots. But you're talking
about something that I think is bigger.
Yeah.
>> And it's an important question.