With a diameter of 950 kilometers, Ceres is the smallest dwarf planet in our solar system. It lies in the asteroid belt between the orbits of Mars and Jupiter. In 2007, NASA launched the Dawn spacecraft to explore this celestial object. The probe’s observations, made between 2015 and 2018, revealed that Ceres was more than just a piece of rock.
Ceres is believed to be home to an underground ocean, which may even cover the entire planet. The discovery will undoubtedly motivate future missions to study it in greater detail and assess its potential for habitability, even detecting traces of extraterrestrial life…
A very heterogeneous planetary crust
The Dawn probe stayed in orbit around Ceres for three years. From the beginning of the observations, in 2015, the apparatus has revealed mysterious points of light, faculae, in the Occator crater of the dwarf planet; this impact crater is 20 million years old. However, experts later realized that these bright spots were due to the presence of sodium carbonate (a common sodium salt, sold as “soda crystals”).
On Earth, sodium carbonate is found in alkaline lakes and on the ocean floor around hydrothermal vents (the “chimneys” from which the Earth’s internal gases escape). These underwater vents are home to an entire ecosystem of chemosynthetic bacteria, which use chemical reactions to generate energy.
However, the origin of the sodium carbonate discovered on Ceres had yet to be clarified. It could have come from underground ice, which would have melted during the Occator impact, only to refreeze later. Or a layer of deep brine may have seeped to the surface at the time of impact, suggesting that Ceres’ interior was warmer than experts thought. The experts wondered, therefore, whether or not this brine was still present on the dwarf planet.
Several studies that have just been published in Nature now lift the veil on this mystery. Scientists now have proof that there is indeed a mass of brackish water beneath the surface of Ceres. The latest data collected by Dawn led to this conclusion: when the probe ran out of fuel, it began to drop and ended up less than 35 kilometres from the surface. This resulted in images of the exceptional resolution, ten times higher than during the mission.
The probe focused in particular on the Occator crater. In particular, it was able to record gravity variations in and around the crater, which, combined with thermal modeling, revealed variations in density characteristic of the presence of an underground brine reservoir under the crater. Thus, the researchers believe that the fractures and heat generated by the impact are at the origin of the salt deposits observed today. “We are finding that pre-existing tectonic cracks can provide pathways for deep brines to migrate into the crust, expanding the impact-affected regions and creating a heterogeneous composition,” they explain in their study.
Source: TrustMyScience
