Dwarf planet Ceres has possible underground oceanic and volcanic activity | NOVA

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Ceres, the largest asteroid in our solar system, now has another bragging rights. According to new research, Ceres has water seeping to its surface, suggesting the presence of an ancient underground ocean.The new findings, documented in seven studies published Monday in the journals Nature Astronomy, Nature Communications and Nature Geoscience, suggest that, although it is cold and salty (and without an atmosphere), Ceres is geologically active.

Also known as the dwarf planet, Ceres dwells in the asteroid belt sandwiched between Mars and Jupiter. At about 588 miles in diameter, it’s about a third of the width of our moon. NASA’s Dawn Orbiter studied Ceres extensively from March 2015 to November 2018, within 22 miles of the asteroid in its final weeks before running out of fuel. In Dawn’s last year orbit, he collected high-resolution images of Ceres, which a team of Italian researchers has now analyzed.

The images show the brackish liquid seeping over the surface of Ceres, “as well as the mounds and hills that formed when the ice melted and refrozen after an asteroid impact about 20 million years ago. Michael Greshko reports for National Geographic. The researchers found the liquid came from an underground saltwater reservoir 40 km below the Occator crater in Ceres. The reservoir can be hundreds of kilometers wide.

The Occator is a 57-mile-wide impact crater, about 20 million years old, and dotted with bright spots of salt. This week’s results suggest that these salt deposits formed when cold underground brine seeped onto the crater’s surface 1.2 million years ago.

“The mountains and bulging hills also support the idea that Ceres undergoes some kind of icy cryovolcanism, with brackish mud or slush acting like molten lava on Earth,” writes Greshko. “In an area of ​​the bottom of Occator Crater, Dawn spotted clues that brines had leaked out of ice volcanoes over the past few decades, if not more recently.”And the data from Dawn shows that the dehydrated salts still have some water in them,” Neel V. Patel reports for MIT Technology Review. “This suggests that any geological activity encouraging these deposits could still occur, which would mean Ceres is still an active world.”

A mosaic image of the Occator de Ceres crater using false colors (in red) to highlight recently exposed salt water pushed from a reservoir deep beneath the dwarf planet’s crust. Image Credit: NASA, JPL-Caltech, UCLA, MPS, DLR and IDA

However, not all scientists are convinced that Ceres is home to an underground ocean. Jim Zimbelman, a geologist at the Smithsonian Institution who was not involved in the latest studies, told Scientific American he remained “quite skeptical.” The water on the surface of the dwarf planet does not imply the presence of an underground ocean, but perhaps of a smaller reservoir, some skeptics believe. Mikhail Zolotov of Arizona State University, who was consulted for one of the seven studies but was not directly involved in the work, “dismisses the conclusion that Ceres is harboring a brine tank as ‘wishful thinking’ Scott Hershberger reports for Scientific American. In an article published in January, Zolotov expressed that the presence of water in the form of ice is not necessary to explain the density of Ceres and that the shape and composition of the body could be explained by organic matter, chondrites. (stony and non-metallic meteorites), and high surface porosity.

But many scientists agree that the possibility of a brine coating on Ceres is compelling, and that the Dawn mission, which provided the discovery, was revolutionary. Dawn was the first probe to orbit two objects beyond the immediate vicinity of Earth, having visited the asteroid Vesta before Ceres. With NASA’s New Horizons spacecraft, which flew near Pluto in 2015, and space rock Arrokoth on New Year’s Day 2019, Dawn has “shown that little icy bodies are much more active than previously thought” , writes Greshko, “stretching the way scientists imagine the geology of dozens of alien worlds. “

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