Science & Technology

Bright Streaks on This Underdog Moon of Saturn May Mean It's Habitable

If you're searching for life in the universe, there's honestly no better place to start than our own solar system. Our neighborhood is filled with icy moons with potential for life: Europa, Io, and Ganymede around Jupiter and Titan and Enceladus around Saturn are some of the most famous spots in our solar neighborhood that have hope for habitability. But this even applies to moons you may not have heard of. It turns out that Dione — a moon of Saturn — also may be a habitable world. Scientists recently discovered straight bright stripes on Dione, whose origins give us even more hope for life.

Related Video: Cassini's Most Stunning Images of Saturn

Water Worlds

At first glance, Dione doesn't look very friendly for life. It's a tiny moon, just 700 miles (1,120 kilometers) in diameter; that's the equivalent of only a quarter the width of the United States. Plus, its surface is heavily cratered, just like our own moon.

Peek under the covers, though, and Dione starts to look more promising. In 2016, a study in Geophysical Research Letters suggested that Dione may have a large underground ocean, just like its Saturn moon siblings Titan and Enceladus. The Cassini spacecraft picked up gravity data that is best explained by water some 60 miles (100 kilometers) below the surface.

It's not a slam-dunk for life, but water is important. Life as we know it requires water to survive. But there are still open questions, such as whether that water is completely sealed inside of Dione or whether it's open to outside material in some way. If stuff outside the water can come inside, that bolsters the case for life since that would provide a source of energy.

Stripes from Saturn — or Beyond

And that's where these new stripes provide hope. Scientists say the bright lines likely come from "the draping of surface materials," according to a Planetary Science Institute press release. Those surface materials could come from the rings of Saturn, comets passing by, or the nearby moons Helene and Polydeuces.

"We think that the material forming Dione's linear virgae is not native to Dione, so this could mean that whatever the source of the material is, it could be contributing some important chemistry to the Dione system that might make it more habitable," Emily Martin, a research fellow at the Smithsonian Air and Space Museum in Washington and lead author on the research, said in a separate museum statement.

These bright features are called linear virgae. (A virga, the singular form of virgae, is classified as a stripe or streak of color.) Martin said her team plans to continue doing modeling work on the virgae, and will also explore if other worlds in the solar system have these weird features. At the very least, the virgae do show that some neat activity is going on at Saturn, she added.

What's even more exciting is that water worlds appear to be everywhere in our solar system. Other prominent examples include Jupiter's moon Europa, the dwarf planet Pluto (for reasons scientists still are trying to understand) and even — in the ancient past — Mars. So as we wing spacecraft across the solar system, there's one thing to add to their crowded agenda: search for something living.

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Learn about another exciting moon of Saturn in "Titan Unveiled: Saturn's Mysterious Moon Explored" by Ralph Lorenz and Jacqueline Mitton. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Elizabeth Howell October 26, 2018

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