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SpaceX wants to go to Mars and habitable exoplanets might be closer than we think!

Hosted by: Hank Green
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[Intro plays]

Hank: On Wednesday, April 27th, SpaceX announced that they plan to launch a Mars mission in 2018. Now that makes a lot of sense: May 2018 is the next good time to launch spaceships to Mars, in terms of the way the Red Planet is positioned relative to Earth. But, before then, SpaceX has a lot of work to do, because they haven’t finished developing the rocket that would launch the spaceship -- or the spaceship itself.

Elon Musk founded SpaceX partially because he wanted to colonize Mars, so we’ve known about the company’s plans for a while. But until now, we didn’t know when they were going to launch that first mission. Turns out, it’s very soon. SpaceX plans to get to Mars using its Falcon Heavy rocket, which would propel a Red Dragon capsule.

The Falcon Heavy is basically a bigger, heavier version of the Falcon 9 rockets that SpaceX uses now. So, it’ll be able to carry more stuff, and generate enough thrust to get that stuff to Mars. Except, the Falcon Heavy hasn’t been tested yet, and it won’t be until at least the fall of this year. And even though it’ll be plenty challenging, making sure the Falcon Heavy is ready to launch a spacecraft to Mars is the easy part. Landing the Red Dragon capsule on Mars will be much harder. Essentially, they want to use rockets to slow it to a gentle touchdown from a speed faster than sound -- a technique called supersonic retro-propulsion.

See, Red Dragon is really just a different name for Dragon 2, the capsule SpaceX plans to use to ferry crew members to the International Space Station. And Dragon 2 already needs these rockets for its abort system -- they make the capsule maneuverable enough to find a safe place to land. Which means that Red Dragon will already have its propulsion system built-in. Plus, since Mars’s atmosphere is much thinner than Earth’s, parachutes wouldn’t be able to slow the capsule down to a safe landing speed. So rockets it is.

The idea might sound familiar, because that’s how the Falcon 9 Reusable rockets slow down for their landings here on Earth. But it’ll be hard to test the way supersonic retro-propulsion would work in Mars’s thin atmosphere. SpaceX is researching it though -- for example, they’ve launched Falcon 9 rockets up to parts of Earth’s upper atmosphere that are about as thin as the atmosphere on Mars. That gives them more information on how rockets perform in Mars-like conditions in general -- which they can use while planning Dragon tests and missions.

But still, they have a lot of work to do in the next two years. We don’t have too many details on the upcoming mission -- Musk has said that he plans to reveal more during the International Astronautical Conference at the end of September. But no matter what those plans are, a successful Mars landing would be a huge deal, and the first time a private company has ever landed a spacecraft on another world.

Speaking of other worlds: Earlier this week, an international team of astronomers announced that they’d discovered three new potentially-habitable exoplanets only 40 light-years from Earth! The researchers described the planets -- and how they found them -- in a paper published in the journal Nature. These three planets are probably Earth-like, meaning they’re the right size to be made of rock. They’re also within the so-called Goldilocks Zone -- close enough to their parent star to be warm enough for life, but not so close that life would burn to death.

The two inner planets do receive a lot more radiation than Earth does, so the outermost planet would be the best spot for potential life. But, the parent star is part of what makes this discovery so exciting -- it’s called Trappist-1, and it’s a type of star known as an ultracool dwarf. Trappist-1 is a dim, cool red star that’s barely larger than Jupiter. And even though it’s relatively nearby, you’d have a hard time finding it in the night sky, even with a really powerful amateur telescope.

As stars go, ultracool dwarfs are pretty common. But this is the first time we’ve ever found exoplanets around one of them. And the star’s dimness is a huge advantage when it comes to studying these exoplanets. See, astronomers can study an exoplanet’s atmosphere by monitoring how the atmosphere slightly affects the light from the star before it reaches us. Most stars are so bright that it’s hard to see this tiny effect at all, but Trappist-1 is dim enough for our telescopes to detect it.

So, the astronomers are using the Hubble and Spitzer space telescopes to look for water and methane in the planets’ atmospheres -- both of which could be signs of life. And the team plans to use the James Webb space telescope, once it launches in 2018, to search their atmospheres for ozone. This would be strong evidence -- though not definite proof -- of some kind of biological production of oxygen, which then forms the ozone. For now, all we know is that these planets could potentially support life. But hopefully soon, we’ll have evidence to predict if they do.

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