Episode 478: Life in Ice Podcast By cover art

Episode 478: Life in Ice

Episode 478: Life in Ice

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Is there life on Europa? We take a look at Greenland and Antarctica to find out more about life on Jupiter’s icy moon. Further reading: Life on Venus claim faces strongest challenge yet Stanford researchers’ explanation for formation of abundant features on Europa bodes well for search for extraterrestrial life Show transcript: Welcome to Strange Animals Podcast. I’m your host, Kate Shaw. Today we’re going to learn about the potential of life on Europa, a moon of Jupiter! To do that we’ll need to look at some extreme life on Earth too. Back in September 2020, we talked about potential signs of life in the atmosphere of Venus, which excited me a whole lot. As a follow-up to that episode, further studies suggest that signs of phosphine detected in Venus’s atmosphere, which might be produced by life, may actually just be sulfur dioxide (not a sign of life). But while it’s not looking likely that phosphine is actually found in Venus’s atmosphere, so far no studies can completely rule it out. So, maybe. Venus isn’t the only part of our solar system where life might exist outside of Earth, though. Astronomers have been speculating about Europa for a long time. The planet Jupiter is a gas giant that has at least 80 moons, but Europa is the one that’s closest to the planet. It’s only a little bit smaller than our own moon. Europa has an atmosphere, mostly made up of oxygen but so thin that if you could magically appear on the moon, you wouldn’t be able to breathe. Also, you would freeze to death almost immediately. It’s a dense moon, so astronomers think it’s probably mostly made up of silicate rock, which is what Earth is mostly made up of, along with Mars, Venus, Mercury, and a lot of moons. If you’ve ever looked at our moon through a telescope or binoculars, you know it has lots of impact craters on its surface caused by asteroid strikes in the past. Europa doesn’t have very many craters—in fact, its surface is incredibly smooth except for what look like cracks all over it. It’s mostly pale in color, but the cracks are reddish-orange or brown. The cause of the cracks has been a mystery ever since astronomers got the first good look at Europa. Many astronomers think these cracks are where warm material from below the surface erupted through the crust, sort of like what happens where lava oozes up on Earth and forms oceanic ridges. But on Europa, the material breaking through the crust isn’t lava, it’s ice—but ice that isn’t as cold as the surface ice. You know you’re on a cold, cold moon when ice that’s close to freezing instead of way below freezing can act like lava. The surface of Europa is about 110 kelvin at the equator and even colder at the poles. That’s -260 F or -160 C. The exciting thing is that researchers are pretty sure the surface of Europa is icy but that the crust lies over a deep saltwater ocean that covers the entire moon. Yes, an ocean! As Europa orbits Jupiter, the planet’s gravity pulls at the moon, while the smaller gravity fields of the other nearest moons also pull on Europa in other directions. This push and pull causes tides that help warm the ocean and keep it from freezing solid. The brown coloration in the moon’s cracks may be due to mineral salts from the water that get leached up through the cracks after warm ice breaks through, assuming that’s what is actually happening to cause the cracks. Astronomers even have images of Europa taken by space probes that show what look like water plumes erupting through the surface and shooting up an estimated 120 miles high, or 200 km. But new studies suggest that the water plumes might not be from the ocean. They might be from pockets of water that form within the crust itself, which grow larger until they burst out through the crust. This is even more exciting when it comes to potential life on the moon, because it suggests that the crust isn’t just a big block of ice. It’s a dynamic system that might harbor life instead of all potential life on Europa being restricted to the ocean. But to learn more about Europa, we have to come back to Earth and examine the island of Greenland. Most of Greenland is covered with a permanent ice sheet like the ones found in Antarctica, but it’s a lot easier to study than Antarctica. One feature seen in the ice sheet is something called a double ridge, shaped sort of like a capital letter M. It’s caused when the ice fractures around pressurized water that forms inside the ice sheet and refreezes. This is caused when water from streams and lakes on the surface finds its way into the ice. The double ridge can look like a crack. New pictures of the cracks on Europa’s surface look just like Greenland’s double ridges, but much bigger. My explanation of all this is extremely clumsy, because this is a really complex mechanism. Researchers only figured it out because some of the team had been studying Greenland’s double ridges for a completely ...
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