Even at the time of the, the Viking
biology results, and the, the inconclusive Viking biology results.
People suggested that perhaps a better approach, rather than picking up some
soil and looking for microbial activity in a small amount of soil.
Perhaps a better approach would be to look in the entire Martian
atmosphere and see if you could see the effects of biological processes.
As we've learned you can certainly see that in the case of the earth.
And in the early earth you would have seen the same thing.
It was in many ways quite exciting then when it 2003 three
separate groups announced that they had
discovered methane in the atmosphere of Mars.
Methane in abundances which were hard to explain by just normal processes.
At least in the first paper that came up there
was a suggestion that biology was the most likely explanation.
Here's that first paper.
And while it doesn't quite say evidence for
life period, it certainly says evidence for life?
With the implication being that perhaps they think the answer is yes.
And then, they come down pretty clearly on the side
that maybe this is a good explanation for what's going on.
This is a pretty dramatic conclusion and
in a pretty traumatic conclusion like this.
It's important to look carefully at the data and come
to your own conclusions about what you think is going on.
So I remember when this paper came out very quickly flipping through
the actual printed copy, which is mostly what I looked at back then.
Flipping through the printed copy and coming to the first figure
which showed their data in which there was supposed to be methane.
Let me walk you through how this works.
First, the idea is exactly the same idea that
we used back when we were looking at Mars before.
And trying to determine whether or not Mars had water in the atmosphere.
Remember what happened?
We put the Sun here and the Earth here like usual.
And if Mars was here or Mars was here, which meant
that the Earth was moving towards Mars or away from Mars.
It was enough of a Doppler shift in the absorption lines of water
that, that lines could be Doppler shifted
out of the terrestrial water absorption lines.
And we could potentially see them.
Remember how we saw those from the early paper [UNKNOWN].
To detect methane you have to do the same thing.
There's sufficient methane in the Earth's atmosphere that you're going to
have a hard time seeing it in the atmosphere of Mars.
Unless you can shift those lines.
Okay, so these observations were made either here or here,
we'll be able to tell by looking where it is.
And I'm going to show you first the data which
show you most clearly the water in the Martian atmosphere.
Okay, so this is units of wave number, usually we
saw things in wave length, which I usually call lambda.
Wave number is simply 1 over the wave length.
And for calibration purposes this regions is right around 3.3 microns.
So this is an infrared.
Remember those early observations from high-spin rad we're at around 0.8 microns.
This is what you could do with photographic plates back in the 60s.
In the, by the 2000s, we had nice infrared
detectors, and could take these, these beautiful infrared spectra.
And what do you see?
Well, here is terrestrial water absorption.
Terrestrial, terrestrial, terrestrial.
And every time you see a terrestrial water absorption, you
see a little blip to the side that looks like that.
You don't see much there, but you see it there, you see it there, you see it there.
That is Martian water a very clear detection of water on Mars.
In this region spectrum, you also have terrestrial methane.
And what you should expect is that there be
a little blip shifted by precisely the same amount.
And well, a little blip would be hard to see here, how about here?
Yeah, a little hard to see here.
But in this region of the spectrum, this is a region where
there is so much absorption from
terrestrial methane that there is no light.
This is this scale actually literally goes down to 0.
No light gets through here because methane is absorbing so much.
Right here at the very edge, though, there is a little bit of
a line and there should be similar line due to Martian methane right there.
The strongest methane line in this region, as you can see
because it's so deep here, compared to these very weak lines here.
So this would be the strongest Martian line in this region too.
Let's go look really carefully at this region and see what we see.
Okay, here we have it.
We actually just have this region cut off right
about here and going up to right about here.
Blowing it up in gory detail and this
is the exact spot where Mars methane should be.
This very thin line that you see from here going
up to here is what terrestrial methane should look like.
It should be very flat in through here.
And so if you subtract this expected signal, the flat signal
from this kind of wavy signal, you get something that looks like this.
And multiplied by a factor of 2 just so you can see it better.
And you see, yes indeed, right there, as you
can even already see in the raw data, right there.
Precisely where Mars methane is expected, you see the deepest dip of any.
That is the detection of methane on Mars.
Now, I remember looking at this and I look at
it again and I think that is an easily disputable claim.
Look at this, this is, yes this
is the deepest absorption right there negative point.
But these wavy patterns go up here.
There should be no reason for 'em to go up so you can just
use that up and down to sort of mentally calibrate how accurate this technique is.
If it goes up, we know that that's an inaccuracy
so it goes down might also be part of the inaccuracy.
Here it goes down not quite as much but almost as much.
Again, helping your brain calibrate the inaccuracies there.
This should be 0.
Look at these, these go up and it goes down below 0.
You can't really go below 0.
All of this stuff is the error, the error level of what's going on,
and the error level, I'm telling you, looks awfully similar to the actual data.
They don't show you the data extending through here,
but it should be a straight line through here.
And you would see these downs and ups and
downs and ups are not dissimilar to this one.
I look at this and I think, I am not
even convinced you have detected methane, much less evidence for life.
But, as I said before this was not the only detection.
There were two other groups that detected methane independently.
And you would think that this would be an argument that maybe it must be real.
I think this is actually an argument of jumping on the wagon.
I think that people heard that the other groups were going to
announce the existence of methane and they sort of had these sort of dubious spectra.
This specter that looked like this and wanted
to jump in and say the same thing first.
I don't know who said it first and who didn't say it first.
But I think this is the case of, of
really is the bandwagon effect rather than three independent verification.
And I really think that there is not very compelling
evidence that there is any detection of methane from this data.
It took a couple of years, but eventually there were data that I
have to say, looked more compelling, at least from a pure data sense.
And let me show you those.
Okay, and this is complicated looking so let me, let me walk you through it.
This is, again, a spectrum.
The telescope on the earth looking at
Mars, looking for absorption in the martian atmosphere.
And now instead of looking at the whole of
Mars, like that original data that I showed you did.
They are taking a small slit, putting it across the face of
Mars like this, and independently looking at every location along that slit.
That's what you're seeing here.
Each of these little bitty lines that you see here is
an independent spectrum at every location along the surface of Mars.
You see, again, wave number down here, inverse centimeters so 1 over lambda.
Again, this is around 3,000 wave numbers, so that's about 3.3 microns.
It's not exactly the same wavelength region
as the previous one, but more or less.
And you see here a model of what the terrestrial atmosphere should be doing.
Here's a big absorption due to methane in the Earth's atmosphere.
Water in the Earth's atmosphere.
Water again.
Water, water, and methane again.
And so what we're looking for are absorption features
shifted by a little bit compared to the terrestrial.
This time because Mars is on the opposite side of
the Earth and the shifts are going in this direction.
And let's look at the water first, because we know that there's
water there and we should be, clearly be able to see it.
And sure enough, here is the terrestrial line, here is the Martian line.
Now, these are not the raw data.
If I blew up the raw data right here, it would look like, something like this.
And here's the terrestrial line and here's the Martian line.
And they took their model of the terrestrial
line and subtracted it from the raw data.
[SOUND] And have the residuals right here.
But anyway, you see the Mars water line.
And you see it's stronger at the North Pole
than it is down here at the South Pole.
This is a consequence of the season.
Something that's been known for a long time.
Here's water again.
Little bitty line here, because there's a little bitty line here.
Big strong line here, big strong line in through here.
