Dwarf Planet Ceres Is An Ocean World With Sea Water Beneath Its Surface

Ceres as seen by Dawn. NASA / JPL-Caltech / UCLA / MPS / DLR / IDA / Justin Cowart

A new study by an international collaboration of researchers suggests dwarf planet Ceres has salty groundwater beneath its largest crater and possibly across the whole planet.

Ceres is the largest object in the asteroid belt and the only dwarf planet in the inner solar system. Results from NASA's second extended Dawn mission have now described incredible new features of this world and how dynamic it is. 

Before Dawn, it was believed that this 940-kilometer-wide (590 miles) space rock was a primitive object of the solar system, mostly unchanged from its formation. However, the data collected by the NASA spacecraft suggests Ceres was likely geologically active in the recent past, with cryovolcanos forming and erupting over the last 9 million years.

The results are published in seven papers spread between Nature Astronomy, Nature Geoscience, and Nature Communications, most of which focus on the Occator crater that formed 34 million years ago. The crater measures 92 kilometers (57 miles) in diameter and has large bright spots. The spot in the middle of the crater is known as Cerealia Facula and the series of bright spots to the east of the center are called Vinalia Faculae.


Images of Occator Crater, seen in false-color, were pieced together to create this animated view. NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

The latest analysis indicates there are hydrated chloride salts at the center of the bright spot known as Cerealia Facula. These salts lose their water pretty quickly, which suggests they have flowed out of this cryovolcano recently.

This belief is backed by gravity data and close-up observations from Dawn, which strongly indicate there is a major reservoir of brine underneath the Occator crater. This reservoir is believed to be the source of the Cerealia Facula, while a different reservoir is suggested for Vinalia Faculae. The whole system of mounds, hills, and salt-spouting cryovolcanoes is likely the consequence of the impact.

“We see numerous low mounds and pits with bright deposits on the floor of Occator, but they do not resemble the densely packed, large, deep pits found on Martian craters,” one of the papers lead author Dr Paul Schenk, from the Lunar and Planetary Institute, said in a statement. “This difference in morphology is likely related to the more water-rich composition of Ceres’ crust.”

The new data suggest Ceres has a strong thick crust, unlike other ocean worlds like Europa and Enceladus, the icy moons of Jupiter and Saturn, respectively. The dwarf planet's crust is also denser at the equator than it is at its poles.  

It appears Ceres is a lot more complex than we believed just half a decade ago.


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