NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI

Ahuna Mons, a mountain on Ceres.

(Photo courtesy of NASA/JPL)

Artist’s concept depicting the Dawn spacecraft thrusting with its ion propulsion system as it travels from Vesta (lower right) to Ceres (upper left).

Scientists studying the dwarf planet Ceres have found that its 13,000-foot volcano arose not from the magma processes that typify inner solar system worlds, but from the action of salty, muddy ice, according a paper published in Science on Friday.

The issue featured six papers that gave the first major look at Ceres data, which was gathered by NASA’s Dawn spacecraft.

“This is the first cryovolcanic dome of this shape and size that we’ve seen in the solar system,” said David Williams, a planetary geologist with Arizona State University who contributed to the paper.

“This is why we send spacecraft out there, because it shows us something totally new and unexpected for a body like this.”

The volcano, dubbed Ahuna Mons, was built by ice-driven processes akin to those found in the outer solar system, powering the geysers of Neptune’s largest moon, Triton, for example, or smoothing the icy surface of Saturn’s Enceladus.

“You have water, mixed with some form of antifreeze — it could be salts, it could be ammonia, it could be methane — and that causes it, in very, very cold temperatures, to behave the way silicate lavas do on Earth,” said Williams.

Because Ceres, the most massive object in the asteroid belt, lies closer to the sun than these worlds, some of the ingredients that drive its cryovolcanism, such as ammonia, should not be occur there naturally. Consequently, some scientists think that the dwarf planet either formed closer to the solar system’s fringes, or later experienced comet impacts that delivered the necessary materials.  

Despite earlier rumors that NASA would send Dawn to a third asteroid, Dawn will continue to image Ceres from a higher orbit. Researchers hope to witness an uptick in the volcano’s activity as the dwarf planet makes its closest approach to the sun in April 2018.