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Ceres is the largest asteroid in the asteroid belt which lies between Mars and Jupiter. It is also considered a dwarf planet, just like Pluto. In a flurry of new studies, astronomers report strong evidence of a salty ocean below the surface
The Dawn probe entered Ceres’ orbit in March 2015, offering an unprecedented close-up view of a surprisingly dynamic environment. Far from being a cold, dry and dull planetoid, Ceres is extraordinarily active.
Researchers now believe that its rigid crust carries an underground ocean, an ocean that may have once been on the surface.
Landing on Ceres would be very logistically challenging and risk contaminating the planet, so researchers instead use remote sensing from Dawn’s instruments to measure the Ceresian galaxy, estimating its composition and internal structure, as well as its topography. Maps like the one above (right side) help researchers estimate its composition and internal structure.
“Ceres has an abundance of gravitational anomalies associated with exceptional geological features,” says Anton Ermakov, postdoctoral researcher at JPL.
Occator is an impact crater located on Ceres containing the brightest of the bright spots observed by the Dawn spacecraft. Astronomers have found evidence that some of Occator’s rocks are hydrohalite – a type of rock that forms in salt water.
Prior to this, hydrohalite had only been observed on Earth.
Ceres appears to be riddled with water-containing minerals that suggest the dwarf planet once had a global ocean. What became of that ocean? Arguably, it now exists only underground as a “fossil ocean,” recent research from NASA indicates.
Dawn’s team discovered that Ceres’ crust is a mixture of ice, salts and hydrated materials, a type of crust also indicative of a former ocean.
It is not only Ceres’ past that intrigues astronomers, but her present also seems quite interesting. Ceres is still geologically active in several ways and shows signs of cryo-volcanism, most likely related to its groundwater.
Dawn’s team also discovered what appears to be a softer, more easily deformable layer beneath the rigid crust, a potential residual liquid signature.
Ceres does not benefit from the internal heat generated by gravitational interactions with a large planet (as is the case with some satellites of Jupiter and Saturn), however, Ceres appears to be a world rich in water.
Recent evidence shows that the bright areas previously observed on Ceres were formed through hydrothermal activity involving salt, which makes the dwarf planet even more tempting, as it appears to flaunt all the ingredients necessary for life.
It is unclear what this means for potential life on Ceres. Water is essential for life as we know it, and NASA considers Ceres one of the most promising places to host life in our solar system. If there is Ceresian life, it is probably in the form of microbes, similar to bacteria. Even though there is no more life on Ceres, she may still have harbored life in her past ocean. Ceres is truly one of the most interesting places in the solar system.
“We are learning more and more that Ceres is a complex and dynamic world that may have hosted a lot of liquid water in the past and may still have some underground,” said Julie Castillo-Rogez, scientist and co-author of the studies’ Dawn project, with headquarters at NASA’s Jet Propulsion Laboratory, Pasadena, California.
It is remarkable how much the Dawn mission has revealed about Ceres. Once again, we learned that a body that didn’t look that interesting is home to a lot of fascinating information. Our solar system is becoming more interesting every year.
“Dawn achieved a lot more than we hoped for when she embarked on her extraordinary extraterrestrial expedition,” said mission director Marc Rayman of NASA’s Jet Propulsion Laboratory in Southern California. “These exciting new discoveries from the end of his long and productive mission are a wonderful tribute to this extraordinary interplanetary explorer.”
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