The Weird, Isolated Mountain on Ceres Is a Giant Ice Volcano

For the first time, NASA scientists have found direct evidence of a mysterious form of icy volcanism on a former planet named Ceres, located in the asteroid belt.

In the 1800s, Ceres was a small planet with big dreams. But that all changed later that century when scientists realised that there were huge differences between planets and the newly minted classification of "asteroids".

After five decades of planetdom, Ceres was demoted to a lowly asteroid.

If Ceres was going to be an asteroid, it would be king of the asteroids. It held the honour of being the first asteroid ever discovered, and it reigned supreme in the asteroid belt between Mars and Jupiter, dominating a third of the belt’s mass.

Then, in 2006, Ceres was once again reclassified, this time as a dwarf planet - not quite a planet, but not quite an asteroid, either. Now, Ceres had to share the spotlight with Pluto and the rest of the dwarf planets out there.

And at just 600 miles (964 kilometres) wide, Ceres is one of the smallest dwarf planets in our Solar System.

A few tricks up its sleeve

But that hasn’t kept Ceres from shoving its way to the spotlight. The tiny dwarf planet has continued to baffle scientists with mysterious white spots and disappearing craters.

And it turns out the icy world still has a few more tricks up its sleeve. One of those tricks includes a massive ice volcano called Ahuna Mons that spews boiling salt water.

Published alongside six other studies on Thursday, NASA scientists released a paper in Science that claims that Ahuna Mons is the strongest evidence yet for the existence of these mysterious ice volcanoes. The scientists used data from the Dawn spacecraft they sent to investigate the asteroid belt.

Ahuna Mons is a gigantic pyramid-shaped mountain taking up a huge, isolated chunk of Ceres that has been baffling scientists for years. It’s 13,000 feet (3,962 metres) high and 11 miles (17.7 kilometres) wide at its base - about half the size of Mt. Everest.

And on a planetary body the size of Texas, that kind of structure stands out. Scientists had no idea how such a giant, isolated mountain could have formed on the dwarf planet.

Another interesting fact about Ahuna Mons is its age. While a few hundred million years sounds ancient compared to the young volcanoes on Earth, it’s extremely young compared to volcanoes on the Moon and Mars.

And even weirder than its disproportionate size, its age, and its lonely location is the material that the volcano is made of - ice. Scientists have long suspected that crazy ice volcanoes, called cryovolcanoes, exist on Pluto and Ceres and even Saturn’s moon Titan, but Ahuna Mons has given them their first real evidence of cryovolcanism.

What is cryovolcanism?

Cryovolcanoes are kind of like regular volcanoes except ... different. Instead of spitting out molten rock when they erupt, they spit out a mixture of salt and water. As Ahuna Mons spews out the salty water it freezes, creating an icy dome at the top, which, for the NASA scientists was one of the telltale signs that Ahuna Mons is a cryovolcano.

The scientists used geological maps of the region made from images taken by Dawn as it orbited Ceres, Ottaviano Ruesch, NASA scientist and lead author of the paper, told Business Insider.

They looked at craters and used 3D elevation models look at what processes could form the isolated mountain. Because they were able to exclude formation by tectonic plates and erosion, volcanism seemed like their best choice.

"The only process that forms an isolated mountain is volcanism," Ruesch said.

After studying the 3D models they made of Ahuna Mons, the scientists also compared its structure to that of other volcanoes. They found that the small volcanic dome, as well as the flanks and summit, are all extremely similar to what you’d find on Earth, the Moon, and Mars.

"We’ve seen hints of cryovolcanic activity in the past but weren’t sure at all so this is an important discovery that puts constraints on how Ceres could have evolved," Ruesch said. "This mountain on the surface tells us what’s going on the interior."

According to Ruesch, the volcano could shine a light on a key process in the evolution of Ceres that formed new crystals and minerals such as salt. It was this salt that enabled the formation of fluids on Ceres. That’s because when you add salt to water, it lowers the temperature at which the water freezes, allowing it to stay fluid for longer.

As Dawn continues orbiting around Ceres, scientists will take more images of the mountain to see if there are any changes and make sure there isn’t any life still brewing in the volcano.

This will allow them to add temporal dimensions to their models, taking more pictures over a longer period of time.

"We don’t expect to find any [life] but you never know," Ruesch said. "Nature surprises us every time so we want to make sure the volcano isn’t active."

So Ceres might not be a planet. And it might not be king of the asteroids. But it’s home to a giant volcano made of ice. And that’s pretty cool.

The study was published in the journal  Nature