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[♪ INTRO]
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Sometimes you hear stories in the news about how we found
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frozen or maybe even liquid water on Mars.
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And those stories are always fun to get excited about because, if Mars is anything like Earth,
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there might be alien microbes in that water.
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But you may have also noticed that we've never actually sampled any of the water.
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And it's not because of some global conspiracy to keep the public
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from finding out about aliens.
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The real reason we haven't studied water on Mars is because almost nothing we've
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sent there is sterile enough to do it.
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Nearly every spacecraft we've sent to the Red Planet has carried thousands of microbes
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with it, which could infect any water we tried to analyze.
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We haven't contaminated the entire planet or anything.
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But to really search for life on Mars, our sterilization skills are
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still gonna have to get a whole lot better.
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Ever since we started going to the moon, scientists have been taking precautions to avoid forward
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contamination, or infecting the rest of the solar system with microbes from Earth.
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To sterilize a spacecraft, engineers use variations of the methods you might think of, from wiping
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parts with alcohol to baking it with extreme heat.
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So, we do try and keep things squeaky clean, but it's not easy.
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For one thing, sterilizing a spacecraft takes a lot of time and money.
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But no matter how much we spend, it's almost impossible to get rid of
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all microbes, since our world is full of them.
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To make this process more cost-effective and efficient,
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NASA has created different tiers of sterilization.
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So based on where you want to explore, this policy allows some
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spacecraft to have more microbes than others.
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For example, if you want to send a probe into the Sun, where there is definitely no life,
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your mission can harbor as many microbes as you want.
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But if you want to go to Mars, the standards are a lot more strict,
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because there could be life there.
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But there's still some wiggle room.
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Like, if you want to go to the planet just to study some cool, totally dead rocks, your
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spacecraft can have up to 30,000 microbes on it.
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And that might sound like a lot, but for comparison,
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your computer mouse probably has more than twice that.
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And a spacecraft is a lot larger than your mouse.
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Allowing up to 30,000 microbes still keeps Mars safe, because research suggests that
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none of those microbes will survive long enough to establish a colony.
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They'd likely be killed off by radiation from the Sun first.
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It also means companies don't need to spend millions of dollars to make a perfectly sterile
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spacecraft, which is a nice bonus.
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This is the category that our rovers, like our sweet little Curiosity, fall into.
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So, really, it's not a surprise that Curiosity couldn't go splashing around in puddles,
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because no matter how much water we find on Mars, that's just not how it was designed.
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Instead, Curiosity was built to figure out whether or not there could have been life
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on Mars using rock and soil samples.
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It wasn't testing to see if there was life in those rocks, just if they suggested
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that there could have been the right conditions for it.
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So as long as we don't let Curiosity near any liquid or frozen water,
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a few microbes are totally okay.
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If we did want to sample water on Mars, or check out any other regions with a high probability
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of life, we'd have to make a much cleaner spacecraft.
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It could only have 30 microbes on the entire thing, three zero, which seems basically impossible.
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But there are some ways to do it.
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One method is to use what's called a dry-heat cycle, or baking, where you expose the spacecraft
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to temperatures around 125 degrees Celsius for 30 hours or so.
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That's enough to kill some of the most stubborn microbes.
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That's what we did for the Viking landers in the 1970s, back when we thought there was
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a chance all of Mars could be habitable.
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But it's a really expensive process, and a lot of materials can't handle those temperatures,
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which is why NASA doesn't bake everything.
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So scientists are also coming up with some other options, like using hydrogen peroxide
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or even gamma rays, a form of high-energy radiation, to kill stray microbes.
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Ideally, these methods would kill the microbes without damaging any sensitive parts of the
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spacecraft or its instruments, which can be a hard balance to find.
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Many of these processes are still very much in development,
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and there are a lot of pieces we have to figure out.
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But we have some time.
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Right now, there aren't any planned missions that are expected to be this clean.
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Even NASA's next rover, called Mars 2020,
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will have the same sterilization levels as Curiosity.
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But like it's predecessor, it's not allowed to go anywhere near water, so it'll be okay.
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The same is true for the InSight lander, which will go to the Red Planet later this year.
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It won't have any instruments designed to search for life,
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so it'll have those same requirements.
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Right now, sampling water on Mars just isn't our main focus.
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There are a lot of other ways we can learn about Mars' history, like with the rock
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and soil samples Curiosity is taking.
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But as we learn more about Mars, we might eventually want to
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start taking those water samples.
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And if we do, we'll hopefully have the right technology to check them out,
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without killing any aliens in the process.
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Thanks for watching this episode of SciShow Space,
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and especially thanks to our patrons on Patreon who make it all possible!
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If you'd like to help us keep making episodes like this, you can go to patreon.com/scishow.
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[♪ OUTRO]
