Ceres Is Home to an Ice Volcano Half the Size of Everest

As NASA's Dawn spacecraft was making its final approach to the dwarf planet Ceres in February 2015, its cameras picked up a large pyramid-shaped formation, visible even from a distance of 29,000 miles (46,000 kilometers).

The mysterious feature turned out to be a salt-sloped, reflective mountain about half the size of Mount Everest, which has since been named Ahuna Mons. The fact that this mountain is completely singular on Ceres, with no other features resembling it, has led to widespread speculation concerning its origins and dynamics (complete with the requisite alien conspiracy theories, of course).

Now, new research published Friday in the journal Science suggests that Ahuna Mons is likely a inactive cryovolcano that, once upon a time, spewed out icy gushes of salt and brine in place of lava flows.

The authors, led by Ottaviano Ruesch of NASA's Goddard Space Flight Center, backed up the claim with comparisons to similar volcanic structures observed on Earth and Mars, as well as analysis of rocky trails of detritus on the mountain's slopes, which are presumed to have been deposited by past eruptions.

"Ahuna Mons is evidence of an unusual type of volcanism, involving salty water and mud, at work on Ceres," said Ruesch in a statement. "Geologic activity was discussed and debated among scientists: Now we finally have observations testifying to its occurrence."

The existence of the mountain is an important clue for interpreting Ceres's past. Ruesch and his colleagues estimate that Ahuna Mons is a youngster, geologically speaking, which actually means it is under one billion years old. This means that Ceres's interior temperature has fluctuated within the same time period, which is the kind of behavior scientists would expect from bonafide planets and moons, rather than objects in the asteroid belt.

"A young volcano on Ceres is surprising because Ceres is a small world, with a diameter about the width of Texas, and small bodies like this should quickly lose the heat from their formation," Ruesch said. "Ahuna Mons is telling us that Ceres still had enough heat to produce a relatively recent cryovolcano."

Of course, studies like these are always fascinating on their own merits, but this one is also notable for the extra premium level of nerdiness achieved by the NASA's press release announcing it.

"Like the 'Lonely Mountain' Erebor in JRR Tolkien's mythology, Ahuna Mons on Ceres was once occupied by a dragon, but one that 'breathed' ice, not fire," the release reads.

Can you imagine how much restraint it takes to not go with a headline like "NASA Says Ceres Was Once Occupied By an Ice-Breathing Dragon" with that kind of set up? Keep the fantastical analogues coming, NASA, we embrace your literary leanings.

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