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Dwarf planet close to Earth appears to be geologically active

The team concluded that the scattered reservoirs must be remnants of a much larger ocean that may have once completely covered Ceres. Anyone who has ever driven on a road that has been sprinkled with salt in winter knows that the dissolved salt ensures that the water remains liquid even below freezing. In the case of Ceres, the temperature of the brine knit is an estimated 30 degrees Celsius below zero. Keeping the brine in liquid form at that temperature requires a lot of salt and possibly a mixture of muddy or clayey minerals.

The brine is “absolutely unsuitable for diving, but more like a big swamp,” says a planetologist Julie Castillo-Rogez of the JPL, member of the Dawnteam and one of the co-authors of the new study. Whatever it was that drilled into the surface of Ceres long ago and created the crater Occator there, it likely triggered ice volcanism on the dwarf planet. Unlike ordinary volcanoes on Earth, the ice volcanoes on Ceres were created by the dwarf planet’s crust freezing and expanding, compressing underground reservoirs of brine and pushing the gunk to the surface under pressure. The Occator impact crater breached the crust of Ceres, causing deep cracks, through which brine water from deep reservoirs made its way to the surface. Once the knit had flowed out, the water evaporated and formed the clear salt deposits that have now been observed.

In fact, some observations seem to indicate that the cryovolcanic activity on Ceres is still ongoing. In one of the seven studies, by a team led by Maria Cristina De Sanctis, planetologist at Istituto nazionale di astrophisica (INAF) in Italy, provides evidence for the possibility that the bright spots in Occator consist partly of hydrated sodium chloride. According to the researchers, the water in this ‘kitchen salt’ must have evaporated on the surface within a hundred years of its emergence. But because the substance is still hydrated, the ice volcanoes on Ceres could still work at a very slow pace. “It is very likely that this volcano is still active, in the sense that small amounts of water are still rising from it,” says planetologist Andreas Nathues from the Max-Planck-Institut für Sonnensystemforschung in Göttingen, one of the co-authors of the new study.

Ice worlds of the solar system

Dawnand from NASA-probe New Horizons, which flew past Pluto in 2015, have shown that small, icy celestial bodies are much more active than previously believed, in a way that is often beyond the imagination of scientists. The bright salt spots on Ceres make it clear once again that “every dwarf planet has something special and unique,” ​​said McKinnon, one of the researchers at New Horizons-mission. “The geology of these icy worlds will have similarities but will be different each time.”

A team led by Castillo-Rogez this week submitted a proposal to NASA to send a probe to Ceres that could send samples from the dwarf planet back to Earth. Such a mission could take place at the earliest in 2031, as it takes years to approve, design and build a spacecraft. During the mission, a 100 gram sample of material would be taken from Occator’s bottom and sent back to Earth.

That sounds like a very small amount to work with, but it would be the most pristine and primitive material we have ever been able to study, Raymond says. “By being able to investigate in detail which materials these celestial bodies consist of, we will learn a great deal.”

This article was originally published in English on NationalGeographic.com

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