Lecture 4.09: Mars -- Methane!!

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The Science of the Solar System

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Caltech

The Science of the Solar System

309 оценки

Learn about the science behind the current exploration of the solar system in this free class. Use principles from physics, chemistry, biology, and geology to understand the latest from Mars, comprehend the outer solar system, ponder planets outside our solar system, and search for habitability in our neighborhood and beyond. This course is generally taught at an advanced level assuming a prior knowledge of undergraduate math and physics, but the majority of the concepts and lectures can be understood without these prerequisites. The quizzes and final exam are designed to make you think critically about the material you have learned rather than to simply make you memorize facts. The class is expected to be challenging but rewarding.

Из урока

Unit 4: Life in the solar system (week 1)

Lecture 4.01: Introduction to life 10:50

Lecture 4.02: Photosynthesis 8:34

Lecture 4.03: Water 9:54

Lecture 4.04: Alternative energy sources 11:15

Lecture 4.05: History of life on Earth8:36

Lecture 4.06: Mars -- The Viking experiement 9:12

Lecture 4.07: Mars -- Microbial hitchhikers 8:58

Lecture 4.08: Mars -- Methane?16:09

Lecture 4.09: Mars -- Methane!!5:19

Lecture 4.10: Mars -- a habitable environment18:46

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Mike Brown
Professor
Planetary Astronomy

Remember how in the last lecture I said that the Mars Curiosity Rover was going to

continue to make observations of methane and

that it had this cool way of concentrating the air even more so

it could get a really precise measurement of how much methane was there?

Well, they did it.

Let's see what they got.

Here are the data.

Here are those first observations they took.

It's by day.

Sol means month and day.

100 days into the mission they made these measurements.

Here it is in parts per billion and remember we said that the answer was.

We had given it as an upper limit of about 1 part per billion so

you can see they made measurements.

With uncertainties that were about this large.

And the three measurements together, they interpreted not as a detection, but

as a upper limit of about one part per million.

The new data, the enriched data, here they are,

labeled EN on here for enriched, are fantastic.

Look at that.

These are clear detections of methane,

clear detections of methane at about that one part per billion.

That was around the upper limit, and here's a non enhanced one, similar again.

But it was about the upper limit turns out that that's about the right answer.

One part per billion.

Okay. I feel a little bit better.

Remember I told you I was worried because if it was much lower than one

part per billion,

it was hard to even imagine that there was any sort of biological activity on there.

But again, one part per million,

perfectly easily explainable by some sort of geochemical process,

rocks interacting with water, many different ways to make methane.

There's also, of course,

meteorites coming in from above that land on the ground that will have.

Organic materials in them.

They can decompose from things like methane.

So one part per billion is comfortably normal and

it seems like that's the end of the story.

Wait, but that's not the end of the story.

Because between these two sets of measurements there were two other sets

of measurements that I neglected to show you.

They look like this.

Okay, what the heck is going on?

Midway between these measurements, there were a set of measurements where it was

kind of normal again, one odd one enhanced and then suddenly over a period of,

as you can see, this 30, 40 days there is a huge amount of methane

detected by the curiosity rover, and then it plummets again.

Okay, this becomes very difficult to understand.

Although, now The Curiosity Rover is seeing variable methane emission.

The telescopic data had seen variable methane emission, and

some of the other spacecraft data had seen variable methane emission.

If it weren't for the fact that it's very difficult to understand how methane can

vary like this, remember the lifetime of methane is very long in the atmosphere.

So if you have methane right now suddenly dropping down the zero

is very difficult to understand.

I would say with our current understanding of things,

it is impossible to understand because of the difficulty of understanding how

this is possible this is something that people remain skeptical of.

I think that skepticism is healthy.

I’ve heard people on the curiosity team, Irritated that finally, when

they get the observations, we should all believe them because there's are so good.

I think everybody on every team thought the same thing,

that we should believe them.

I will say, though, that with three or

four separate measurements showing the same thing,

not just detections of methane, but sort of agreeing on the level and time scales

of variability It's starting to seem like maybe there's something really going on.

What's going on?

Well, whatever's going on,

it's something that has to be able to consume methane at a very fast rate.

The presence of methane, even growing methane, is not necessarily that hard.

The consumption methane so fast is not something that we currently understand.

I think what's going to happen,

my prediction here is that now that people are more likely to take this seriously.

Which I think they are.

I think I am too.

I think that somebody will come up with some clever explanation for

how you can have methane vary at these sorts of time scales.

And when an explanation works well.

When somebody comes up with an explanation that works, and is physically and

chemically possible.

I think you might start to see people beginning to believe that this is what's

going on in through here.

I sounded really hopeful right there, didn't I.

Well that was a couple of years ago.

This is a 2017 update and the update is there's no update.

Well, curiosity has made a few more measurements.

There's always that very low level where is a little bit of methane,

but not the big puffs that come and go.

Nobody else has seen big puffs that come and go.

Are they real?

Well, we still don't know.

Nobody has come up with a good idea for how they could possibly be real.

But that's also no reason not to believe the data earlier from curiosity.

So right now, we're left with a mystery.

And one that I'm sad to say, the only solution is to stay tuned.

See what happens next.

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