Ceres is not so dry after all. A new study finds the dwarf planet is an ocean world with reservoirs of seawater beneath its surface.
Ceres is the largest of the huge number of objects in the asteroid belt between Mars and Jupiter. It’s the only dwarf planet in the inner solar system locking up one-third of the entire mass in the belt.
The dwarf planet is about 950 kilometers (600 miles) wide. It lies less than three times as far from Earth as the Sun.
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The new results come from NASA’s Dawn spacecraft, which orbited around Ceres from 2015 to 2018. Just before running out of fuel, the probe orbited right above the surface of Ceres, focusing on the Occator crater. The crater is a 20-million-year old feature that emits a strange glow.
Scientists working on the Dawn mission revealed today (Aug. 10) that remnants of an ancient body of briny water are buried beneath the icy crust.
Variations in Ceres’ gravitational field back that up, implying that the underground reservoir of salty water may stretch horizontally beneath the ice for hundreds of kilometers and reach depths of roughly 40 kilometers (25 miles).
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A team of researchers analyzed infrared images relayed from the Dawn probe, captured around 35 kilometers (22 miles) from the asteroid. Thus, they found the presence of the compound hydrohalite. The compound is a material common in sea ice but which until now had never been observed off of Earth.
Maria Cristina De Sanctis, from Rome’s Istituto Nazionale di Astrofisica, said hydrohalite was a clear sign Ceres’ used to have seawater.
“We can now say that Ceres is a sort of ocean world, as are some of Saturn’s and Jupiter’s moons,” she told AFP.
Astronomers believe that the extreme saltiness of the water, which lowers its freezing point, has helped it remain a liquid for so long.
The reservoir could have been deployed by the impact that made the crater in the first place, and helped leave the salt deposits that are now on the planet’s surface and create the strange glow on the Occator crater.
The researchers said the salt deposits looked like they had built up within the last two million years.
This suggests that the brine may still be ascending from the planet’s interior. That’s something De Sanctis said could have profound implications in future studies.
The research was laid out in a series of papers published in Nature.
Another paper suggests that Ceres has only recently stopped undergoing a period of activity from ice volcanoes, which began nine million years ago.