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We have new insights into the bizarre nature of lava planets, and the icy moon Europa may yet reveal some of her salty secrets.

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Sources:
http://dx.doi.org/10.1093/mnras/staa2487
https://www.eurekalert.org/pub_releases/2020-11/mu-swr110220.php
https://exoplanets.nasa.gov/exoplanet-catalog/6154/k2-141-b/
https://www.nature.com/articles/s41550-020-01248-1
https://press.nature.com/laboratory-predictions-for-the-night-side-surface-ice-glow-of-eu/18511110

Images:
https://svs.gsfc.nasa.gov/13496
https://www.eso.org/public/images/eso0933a/
https://www.eurekalert.org/multimedia/pub/247654.php?from=482590
https://exoplanets.nasa.gov/resources/1002/kepler-beauty-shot/
https://svs.gsfc.nasa.gov/13758
https://svs.gsfc.nasa.gov/13163
https://www.jpl.nasa.gov/missions/europa-clipper/
[♪ INTRO].

The search for planets around other stars has mostly focused on Earth-like worlds with the potential to host life. But putting aside that holy grail, there’s a whole trove of planets that probably aren’t great places to live but are totally fascinating in their own right.

Like lava planets. These worlds orbit so close to their stars that all or much of their surface is consumed in an ocean of molten rock. They’re completely unlike anything we are familiar with, but thanks to a paper published last week in the.

Monthly Notices of the Royal Astronomical Society, we have a better idea what one of those planets might be like. And it is bizarre. The paper focused on an object called K2-141b, which was discovered in 2018 by NASA’s Kepler Space Telescope.

It has a mass around five times greater than Earth and orbits a star around 200 light-years away. And it’s got all the hallmarks of a planet: a solid surface, deep oceans, a thin atmosphere, even rain. There’s just one catch: All that stuff I just talked about is rock.

It’s got a rocky surface, oceans of lava, an atmosphere of vaporized rock, and to top it all off, it rains molten rock. Now, on this planet, one complete orbit takes just eight hours. And since it’s so close to its star, scientists can’t actually photograph it directly.

But one research team was able to feed the little data we have into a computer simulation to explore what the planet might be like. They already knew that at such a distance, the planet is almost certainly tidally locked, meaning the same side of the planet always faces the star. And through the simulations, they found that the side facing the star would be around 3,000 degrees Celsius, while the night side would be 200 below zero. 3,000 degrees is hot enough to not just melt rock but simply vaporize it, creating the ingredients for a thin atmosphere.

Kepler can’t tell us what the planet’s made of, but the team explored several possibilities, including sodium, silicon monoxide, and silicon dioxide, which are all common in rocky planets. Each resulted in a world with slightly different characteristics, but the same broad strokes:. First, as rock is vaporized into gas on the hot side, it rushes to encircle the planet, reaching wind speeds of more than 5,000 kilometers per hour.

And when the hot gas reaches the frozen temperature of the night side, it suddenly cools and begins to rain out. That lava rain forms a vast ocean of liquid rock up to 100 kilometers deep. The lava then slowly flows back toward the day side, where it reheats and vaporizes again.

So it’s basically like Earth’s water cycle. Like, if an afternoon shower were actually a sizzling inferno of molten rock. What’s especially exciting about this is that we might actually be able to find out if these predictions are true.

Since it’s just 200 light-years from Earth, this planet should be well within the range of NASA’s upcoming. James Webb Space Telescope. So when it launches next year, it’ll be able to search the planet’s atmosphere for the vaporized rock the study suggests we should see.

Meanwhile, we can just be glad we get to explore it from a safe distance. We also learned something new this week about a glowing world much closer to home. Except this time, it is not a lava world; it is Jupiter’s icy moon Europa.

Planetary scientists think that there is an ocean of liquid water hiding beneath Europa’s frozen surface. It’s likely that heat from deep within the moon keeps the water liquid, but a healthy dose of salt also probably helps act like an antifreeze. For now, though, it’s still a mystery how much salt there is and what kind of salt.

But in a paper published this week in Nature Astronomy, a team of scientists proposed a way to find out. Their idea rests on a strange property of ice that physicists have known about for decades:. Hit it with a bunch of radiation and ice can actually start to glow.

But that glow can vary depending on what’s in the ice. The team conducted laboratory experiments in which they formed ice out of water mixed with various possible salts. Then, they exposed the ice to a stream of electrically charged particles similar to the intense radiation around Jupiter.

The interaction between the charged particles and the ice created a greenish glow called electron-stimulated luminescence. Basically it glowed in the dark. But what was especially interesting about this was that scientists were able to see how the amount of glow changed according to what was in the ice.

Compared to ice without any salt, the presence of sodium carbonate or sodium chloride significantly dimmed the glow. Meanwhile, the salt epsomite caused the glow to more than double in brightness. And, since there’s a decent chance that the surface ice and the under-ice ocean have the same kinds of salts mixed in, the amount of glow could provide a critical clue to the ocean’s composition.

Just like with the lava planet, the most exciting part here is that these experiments might soon be able to be tested. NASA plans to launch the Europa Clipper mission around the middle of the decade, and it’ll make a series of close flybys of the moon’s surface. Its camera should be sensitive enough to detect any green glow coming off the ice, which could help scientists not just figure out what salts are present, if any, but also map them.

It’s not every day that astronomers have the luxury of making predictions that can be tested in years instead of decades. At the same time, having good estimates to go on will help make these upcoming missions even more productive and efficient. So it’s looking like a win-win for astronomy this week!

Thanks for watching this episode of SciShow Space News! With the holidays coming up, maybe you’ve been wondering what to get your friends and family this year. And if you’ve got any science fans in your life, we’ve got great ideas for you.

We just released a brand-new set of SciShow Magnetic Words over on DFTBA.com. Our whole team put together these magnets with science-related words, like supernova, and gravity, and extinction. And you can stick them on your refrigerator or any other magnetic surface and rearrange them to create fun science sentences and poetry.

We’ve also got a bunch of other SciShow merch, and you can find it all at DFTBA.com/SciShow. [♪ OUTRO].