Scientists are particularly fascinated by Jupiter's moon Europa and its ice shell because they think the ocean hidden beneath that ice may be one of the most likely places to find extra-terrestrial life in our solar system. So imagine their surprise when scientists studying the distant moon saw something that looked awfully similar to our home planet's past: All that ice is moving, just as it did here on Earth about 580 million years ago, during a period known as "Snowball Earth."
That's according to a new paper published in the journal Nature Astronomy, which builds a model for what could be happening at the moon. The scientists behind the paper are working within the context of what we know about Europa—things like how much sunlight reaches its surface—with what we still need to figure out—things like how much heat is produced inside the planet as its core is tugged and squished by Jupiter's huge gravity.
But they were particularly intrigued to look at all that ice and see what it might be doing. Just like here on Earth, Europa is warmer at its equator than it is at the poles. That means that scientists think the ice is thicker at the poles—on the scale of potentially about a mile thicker.
Compare that to circumstances about 580 million years ago here on Earth, when giant ice sheets more than half a mile thick covered the surface, leading scientists to nickname the period "Snowball Earth." During that time, geologists believe ice flowed from Earth's poles southward, toward the equator, driven by the sheer weight of ice piled up at the poles.
And now, the team behind the new paper believes that a similar phenomenon is taking place on Europa. They modeled what would happen based on two layers of ice, an upper, thin, brittle layer resting on top of a softer ice that can move more freely. In general, those models suggest ice is flowing toward the poles, although if that softer bottom ice lets material rise and fall, it could cancel out that pattern.
Scientists are hoping to have even more data to use to crack Europa's secrets within the next decade, after the launch of a mission called Europa Clipper, which is due to orbit the moon 45 times, skimming as close as 16 miles above its surface. It's already planning to measure how thick the moon's ice is.