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  • This is such an awesome experience

  • To get up close and personal with the curiosity rover

  • I mean, this isn't the exact one that's on Mars, obviously

  • but it's basically identical

  • VOICEOVER: I'm here at the Jet Propulsion Lab in Pasadena, California

  • I don't know how we got in here, Bill. It's amazing.

  • VOICEOVER: This is the NASA center that's famous for building things like the Mars rover,

  • space probes, and rescuing Matt Damon from the red planet

  • DEREK: You guys must get pretty sick of answering questions about The Martian

  • KEN: Yes.

  • VOICEOVER: This is project scientist Ken Farley

  • I spoke with him about life on Mars.

  • He's one of many scientists working on the first NASA mission in 40 years

  • designed specifically to look for life on another planet.

  • It's called, Mars 2020.

  • DEREK: If there were life on Mars, wouldn't we have found it by now?

  • KEN: No. We would not have found it by now.

  • DEREK: But we've been looking! There's been a number of missions like

  • the Viking landers and like Curiosity, for example

  • DEREK: Part of the problem is, we're not even sure what we're looking for.

  • Life on Mars may have been completely different from life on Earth

  • Recent missions, like the Curiosity and Exploration rovers, look for and found evidence of water,

  • a key ingredient for life.

  • SARAH: Follow the water, where was the water and when was the water

  • and then looking for habitability, looking for places that could have supported life.

  • Now we know enough about Mars to look for ancient life

  • instead of anything on the surface of Mars today.

  • DEREK: There's no life on the surface of Mars today?

  • SARAH: Most likely, if there is life on Mars today, it would be underground, underneath the ice caps,

  • in places that are very very hard to investigate with the sort of rovers and landers that we've sent so far

  • DEREK: So we're talking, like, moles, groundhogs [LAUGHTER]

  • SARAH: Well, microscopic, bacterial moles. No, not actual moles!

  • We're looking for, we call them biosignatures.

  • It's a pattern or a substance in the rocks that can only have been formed by life.

  • VOICEOVER: To find those biosignatures, the 2020 rover is gonna need cutting edge technologies,

  • developed here at JPL.

  • But for definitive proof of life, they'll need drill samples.

  • KEN: We need to take a core, that's about the size of a piece of chalk.

  • We have to collect 37 tubes like this that will ultimately be laid on the surface of Mars

  • for possible return in the future.

  • VOICEOVER: Mars 2020 is different from past missions

  • because now NASA will need to bring those samples back to Earth to test them for evidence of life.

  • KEN: If they are brought back to Earth, we will be able to use all sorts of different kinds of techniques,

  • many of which have not yet even been invented

  • because nobody has been posed with this question.

  • VOICEOVER: So, in order to find life, we'll have to return those samples from Mars,

  • something that's never been done before,

  • then test those samples with techniques that haven't even been invented yet.

  • So I had to ask:

  • DEREK: How good do you think your chances are, of finding life?

  • KEN: Hmmm

  • I'd say they're poorer than even just because I remain skeptical

  • Regardless, we will learn about what the early history of the Solar System is like.

  • And that's the same environment, the same Solar System, that earth was in when life was evolving.

  • If you want to understand the origin of life, on Earth 'cause that's the only place we know life exists,

  • the rocks that recorded that are all gone.

  • DEREK: So in a way, looking at Mars is like looking at a version of Earth frozen in time

  • right about when life would've sprung?

  • KEN: That's, I think, the most exciting way to look at it.

  • It's just unbelievable. The stuff that is happening here is just so far beyond anything else.

  • What are you doing today?

  • Are you sitting in your cubicle, are you working on your computer?

  • Ok, these guys are working on a freaking machine, in outer space, on Mars that is trying to discover life.

  • This is cool.

  • That was one of my field pieces from the Netflix show "Bill Nye Saves the World".

  • on which I am a correspondent.

  • If you haven't seen it, you should check it out.

  • But, obviously, because that show is for a broader audience, I don't get to go into the kinda crazy detail

  • that I sometimes do on this channel.

  • For example, this image is the first ever beamed back from the Martian surface.

  • It was taken by the Soviet lander, Mars 3 on December 2, 1971.

  • After becoming the first man-made object to make a soft landing on Mars

  • that lander transmitted data back to earth for just 14.5 seconds before going quiet.

  • And no one really knows what happened to it

  • but it might have had something to do with the huge dust storm that was taking place at the time.

  • Now, this is the first clear image sent back from the Martian surface.

  • It was taken by the Viking One Lander on July 20th 1976.

  • And one of the stated aims for that mission, was to try to find evidence of existing life on the Martian surface.

  • And there was this experiment called the labeled release experiment

  • where a scoop of Martian soil was taken

  • and then a dilute solution of nutrients was added into that soil

  • but, in those nutrients was the radioactive atom

  • Carbon-14, the idea was if you tried

  • to detect the gases around the soil

  • if you detect some radioactive Carbon Dioxide

  • you know that the nutrients were

  • broken down by something in the soil

  • presumably something that's living.

  • what was remarkable about this experiment was

  • that it got a positive result, there were a few other experiments trying to detect life in other ways

  • and they failed to get a detection, but this one detected radioactive Carbon Dioxide

  • and what's even more impressive was the Viking 2 Lander

  • which tried the same experiments

  • after the Viking 1 Lander, it also got

  • the same positive result, so things were

  • looking promising, but then about a week

  • later they tried to rerun the experiment

  • add a little bit more nutrients to the

  • soil and see if you could get more CO₂, but they couldn't

  • there was no additional COreleased, so based on these negative results and the negative

  • results of the other experiments.

  • Most scientists have concluded that there is no surviving life on the surface of Mars, today.

  • so how is the COproduced in the first place?

  • Well, chemists suspect that very highly oxidizing chemicals, things like perchlorates, exist in the Martian

  • soil and would have reacted with the nutrients producing the COto start with.

  • But, once those chemicals are used up, well there's nothing for those

  • nutrients to react with, and so we get no

  • COthe next time, the nutrients are introduced.

  • this story highlights just how difficult searching for life is using only remote instruments.

  • And that's why, for Mars 2020 they're going to

  • create some rock samples that should be

  • returned to earth, if only they can get

  • the budget for another mission that will go back and pick them up.

  • But the rover they're sending in 2020, will also have some new tools on board

  • that will allow them to look at rocks in

  • finer detail than ever before.

  • One tool called PIXL, will use x-ray spectrometry to try to

  • detect chemical elements with a spatial resolution that

  • goes down to the size of a grain of salt.

  • Now what they be looking for, are layered structures similar to stromatolite found here on earth.

  • those are mineral deposits which get built up by billions and billions of-

  • tiny organisms. - So you are not really looking for fossils or tiny little you know, microbial evidence.

  • We are looking for the structures that they would have produced, layered structures.

  • that's how we know about the oldest life on Earth, and so it's logical to think

  • that's how we might find out about this old life on Mars.

  • And the job of finding evidence of past or current life on Mars

  • is made even more difficult by Planetary Protection,

  • that's the principle whereby we should not introduce any life from

  • Earth to these places where we're studying like Mars.

  • and that's completely understandable, because I mean the worst discovery of life we could make on Mars

  • would be life that we introduced there

  • by our spacecraft...

  • I mean certain organisms are really hardy,

  • even in the vacuum of space and even when bombarded by radiation.

  • But, due to this constraint, spacecraft must be strenuously

  • sterilized and also, they're restricted from landing near sites where we think

  • there may be liquid water.

  • I'm really looking forward to the results of the Mars 2020 mission.

  • and hopefully a later mission, where we actually go back and collect the samples that were placed there.

  • But one thing that really struck me from my interview with Kim Farley was

  • when he said that Mars is really like a

  • time capsule of the rocks that Earth had

  • when life evolved here.

  • That's, a way I'd never really thought about it before,

  • but of course because of plate tectonics and

  • all the weathering that would have taken place on earth,

  • we don't have the rock record from when life was first evolving on

  • this planet, and that makes Mars

  • a really good place to look, not only for new forms of life, but also for an

  • understanding of how life on Earth, may have begun.

This is such an awesome experience

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下一個火星任務。火星2020 (The Next Mission to Mars: Mars 2020)

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    Ntiana 發佈於 2021 年 01 月 14 日
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