29 Jun 2016

There was water on the dwarf planet, Ceres. This statement was made by a team of astrophysicists, led by a team of researchers coordinated by INAF (Italy's National Institute of Astrophysics) researcher Maria Cristina De Sanctis. Thanks to observations made by the Italian spectrometer, VIR, which is on board NASA's Dawn mission and was provided by the Italian Space Agency (ASI) under the scientific guidance of theNational Institute of Astrophysics, researchers have found, in the brightest area of Ceres, situated inside the Occator crater, the highest concentration of carbonates ever recorded in any environment other than that of the Earth.

It is precisely the type and abundance of these minerals that suggests the presence of liquid water beneath the surface of Ceres in recent geological eras. “This is the first time that we have seen such a large quantity of this mineral in other areas of the Solar System”, says Maria Cristina De Sanctis, principal investigator of VIR and main author of the article describing the discovery, which was published in the latest issue of the magazine Nature.

Occator is a young crater from a geological point of view, which was formed approximately 80 million years ago. With a width of92 kilometres and a central depression of 10 kilometres in diameter, the crater has a wide peak right in its central area that is covered with highly reflective material and has concentric and radial fractures on top and around it.

The team of researchers has discovered that the most abundant mineral present in this very shiny area is sodium carbonate, a salt that is typically found on Earth in hydrothermal environments. This material must have leaked from inside Ceres, as it cannot have been deposited by the impact of an asteroid. Therefore, the ascent of this material from the deepest layers of the celestial body suggests that the temperatures inside Ceres are higher than what has been thought until now. It could conceivably have been the impact with an asteroid, which formed the Occator crater, that facilitated the display of carbonate on the surface observed today, but researchers believe that processes going on inside Ceres itself played a role in this emergence.

The results of the investigation suggest that water may have been present in liquid state under the surface of Ceres in recent geological eras. The salts could be what remains of an ancient ocean, or of water deposits that had come to the surface and then solidified millions of years ago.

In a previous work, also presented in Nature, the same team discovered that the surface of Ceres features clays containing ammonia. Since ammonia is a rather abundant substance in the Outer Solar System, this result suggests that Ceres might have been formed in the vicinity of Neptune’s orbit and that it subsequently migrated towards the internal areas of our planetary system. Another scenario suggests that the celestial body was formed in the area in which it is found today, but with material coming from the Outer Solar System.

“We must emphasize the importance of the role of the Italian Space Agency”, says Raffaele Mugnuolo, programme manager for participation in the Dawn mission, “in guaranteeing Italian participation in the mission through an agreement with NASA and DLR, and subsequently for the creation of the VIR-MS instrument and for full support of the Italian scientific team that, in the right conditions, is able to achieve excellent outcomes like this one.”