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  • [♪ INTRO]

  • Last week, NASA did a thing that, for us in the science communication world, is always

  • a little bit of a mixed bag.

  • They were like, “We've got some really big Mars news,” and then the entire world

  • goes crazy and there's like, “There's life on M...!”

  • And then you're like, “No, they probably would do this a different way if there was

  • life on Mars,” but we'll listen, and it will be exciting, but probably not in precisely

  • the way you're thinking.

  • And it was cool!

  • But let's get this out of the way in the beginning: The Curiosity rover did not find

  • evidence of past or present life on Mars.

  • And when the headlines said 'Organic Matter on Mars', for non-science speakers that

  • can be confusing, and they're like, “So, like, organic matter like a little bit of,

  • like, snot?

  • Like, what is this on Mars?”

  • No, it's carbon compounds.

  • If there was life on Mars, you would find out about it in a really big way, I promise.

  • And we'd be here.

  • But, Curiosity did find even more evidence to indicate the planet could've been habitable

  • billions of years ago.

  • The results came in two papers published last Friday in the journal Science.

  • And while they don't prove anything about life on the Red Planet, they do show some

  • of the strides Curiosity is making in understanding Mars' history.

  • Since it landed on Mars in 2012, Curiosity has been hanging out in Gale Crater, which

  • planetary scientists are pretty sure is an ancient lake bed.

  • Among its duties, the rover has been drilling into rocks and sniffing the atmosphere to

  • detect organic molecules.

  • These are carbon-containing compounds that, on Earth, are often produced by life.

  • So finding them on Mars might suggest life once existed there, too, although they can

  • also be made by non-biological processes.

  • A key one is methane.

  • We've known that there's methane in Mars's atmosphere for a while.

  • But now, Curiosity has shown that the amount, at least in the vicinity of Gale Crater, varies

  • seasonally.

  • In the northern hemisphere, it peaks in summer months and drops near the winter.

  • The paper's authors suspect the variations come from methane being stored deep underground,

  • and from temperature changes on Mars's surface that allow it to flow upward.

  • For example, the gas could get trapped underground in icy crystals called clathrates, which melt

  • come summer to free the gas.

  • At the moment, it's impossible to know if this methane comes from biological or non-biological

  • sources.

  • But we do know it's getting replenished somehow.

  • The molecules only survive for a few hundred years before sunlight breaks them down, so

  • something has to be making more methane.

  • Even if there is no life producing it, though, this is still very cool news.

  • For one, Earth's atmosphere doesn't have a seasonal variation of many molecules, so

  • Mars gets to be kind of special that way.

  • Also, if the variation does come from geologic processes, it would mean that Mars's interior

  • isn't as dead as we thought.

  • There would likely have to be some kind of heat source down there to drive those methane-producing

  • reactions.

  • So it's probably not aliens, but it's probably some very cool geology.

  • And that's the result of one of the papers.

  • The other involved organic molecules more complex than methane.

  • A few years ago, Curiosity ran tests that suggested larger organics existed on Mars's

  • surface, but the data was contaminated by other chemicals.

  • Now, we have some clearer results.

  • Curiosity found these new compounds by drilling into 3.5 billion-year-old rocks called mudstone.

  • Mudstone is a sedimentary rock that forms from silt accumulating at the bottom of a

  • lake.

  • Unlike other rocks on Mars, it's likely a better place to store organic compounds.

  • Now, this could be because of a few reasons, including, like, protective interactions with

  • other molecules.

  • After Curiosity powderized and extracted the samples, its tool suite, called SAM, heated

  • them to more than 500°C.

  • That was more than enough to get them to release their organics.

  • Then, SAM could analyze exactly what molecules came out.

  • Some of the compounds identified included thiophenes, benzene, toluene, and small carbon

  • chains.

  • But they likely started off as something else.

  • See, Curiosity collected its samples from less than 5 centimeters below the ground.

  • Anything that close to the surface is affected by radiation from space, which, along with

  • other chemicals in the dirt, breaks down organic matter over time.

  • So most likely, the compounds Curiosity found are really pieces of larger organic molecules,

  • although we don't know what they started out as.

  • If it were capable of drilling farther down, where radiation isn't a problem, maybe the

  • rover could have found some of the original organics.

  • But the fact that some bits and pieces survived long enough to be detected reveals that Gale

  • Crater might have once held all the necessary chemical building blocks for life.

  • Whether or not life actually existed, though, that's still up in the air.

  • Just like the methane, there's no way to know where these organic molecules came from.

  • Many of them are found elsewhere in the solar system, like in interplanetary dust and on

  • meteoroids.

  • So it could be that Curiosity happened to find the remnants of a meteorite impact, not

  • of life.

  • At a minimum, the study shows that traces of Martian organics, whether they come from

  • tiny Martians or just chemistry, can survive for billions of years, to some degree.

  • Luckily for us, we have a lot of future missions planned that can help us dig into that matter.

  • Or, rather, drill into it.

  • NASA's InSight lander, which launched back in May, will land on Mars in late November.

  • While it won't be able to determine chemical compositions, it will be able to drill down

  • farther than ever before: 5 meters, to lower a heat probe.

  • So it might be able to help us figure out some of that seasonal methane puzzle.

  • Also, the ESA's ExoMars Rover is slated to launch in 2020, and while it will only

  • be able to drill down 2 meters, it'll have the tools to extract rocks and analyze what

  • they're made of.

  • So hopefully, the fact that it will be able to go, like, 40 times deeper than Curiosity

  • means we'll be able to find more intact organic molecules.

  • Finally, NASA's 2020 Rover won't be doing any deep drilling, but it will have technology

  • to hunt for and understand any Martian organics it comes across on or near the surface.

  • So hang on you tiny, probably dead Martians!

  • If you ever existed, we're coming for you!

  • Thanks for watching this episode of SciShow Space!

  • If you'd like to keep following the latest discoveries in astronomy and planetary science,

  • we make a news episode like this every Friday!

  • To make sure you never miss one, you can go to youtube.com/scishowspace to subscribe.

  • [♪ OUTRO]

[♪ INTRO]

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