Space Probe Reveals Dwarf Planet Ceres Is an Ocean World

This image of Ceres approximates how the dwarf planet’s colors would appear to the eye. (Credit: NASA)

(CN) — With the help of NASA’s Dawn space probe, scientists have begun to unravel centuries-long mysteries of Ceres, a dwarf planet asteroid located in the asteroid belt between Mars and Jupiter.

Launched in September 2007, the Dawn probe was sent to examine the two largest bodies within the asteroid belt, Vesta and Ceres. Although it was retired from service on Nov. 1, 2018, when it ran out of fuel, a series of seven research papers released this week in the journals Nature Astronomy, Nature Geoscience and Nature Communications reveal what astronomers were able to learn about Ceres, the largest asteroid in the belt.

In January 2014, scientists detected water vapor emissions from Ceres, an unexpected characteristic usually found in comets rather than asteroids. In a paper led by Carol Raymond of the California Institute of Technology, researchers discovered cyrovolcanic activity on Ceres, not only showing evidence of a past geologically active world, but a current brine reservoir.

Another team of astronomers found that the surface of Ceres was crafted by flowing water, suggesting a large amount of subsurface ice as well as a few locations where such ice was exposed to the surface. This kind of exposure could explain how water emissions were detected coming from the dwarf planet asteroid. While researchers discovered evidence of an ocean once existing on Ceres, they were unable to determine if still exists under the surface.

The researchers also discovered hydrated chloride salts in the center of the 20 million-year-old Occator crater. Such salts are known to lose their moisture quickly, leading scientists to believe that they are making their way to the surface from water located underneath the surface.

Writing in an accompanying comment article, Julie Castillo-Rogez, from the California Institute of Technology’s Jet Propulsion Laboratory, said the discovery the salts was a “smoking gun” for ongoing water activity.

“That material is unstable on Ceres’ surface, and hence must have been emplaced very recently,” she said.

The teams of scientists focused much of their studies on the 57-mile diameter crater due to it being the brightest of bright spots on Ceres. As previously assumed by astronomers, the brightness likely comes from the presence of the hydrated chloride salts.

Ceres has often befuddled its observers. When it was discovered by Italian priest Giuseppe Piazzi in 1801, it was classified as a planet. In the 1850s, it was classified as an asteroid after astronomers found several other objects sharing the same orbit. In 2006, when astronomers reclassified what constitutes a planet, Ceres was classified as a dwarf planet, though it is also referred to as an asteroid.

Dawn orbited Ceres from 2015 to 2018, gathering data with two framing cameras, a visible and infrared spectrometer used for thermal imaging and a gamma ray and neutron detector that allowed the spacecraft to measure rock-forming elements on the surface.

Ceres’ size means it has its own gravity, which allowed Dawn to assume orbit about 22 miles above the dwarf planet’s surface.

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