Mar. 23, 2016
Water found on the surface of Ceres by the VIR ASI/INAF interferometer carried on NASA's Dawn probe.
For the first time ever, NASA's Dawn team have found water on the surface of dwarf planet Ceres, inside the Oxo crater. The observations by the Italian VIR spectrometer, provided by the Italian Space Agency (ASI) under INAF's scientific lead, were fundamental for the discovery. The news was announced a few hours ago during a press conference at the 47th edition of the Lunar and Planetary Science Conference held at The Woodlands, Texas. Maria Cristina De Sanctis, form INAF-IAPS and principal investigator for VIR, confirmed that “VIR has observed the presence of water inside Oxo, a recently formed crater with a diameter of approximately 9 km located in the northern hemisphere of Ceres. This discovery confirms the importance of Ceres in the formation of the solar system”.
The new, highly detailed images of the surface of Ceres presented by the Dawn team show the planet's geological complexity, with some areas such as the Haulani crater showing a profoundly different composition to their surroundings. VIR data from investigations on Haulani are also essential, allowing scientists to measure the wavelength of sunlight reflected by Ceres' surface in the interval between visible light and infrared, in order to understand the type and composition of the materials. In Haulani, which is a crater with an irregular shape and clear streaks of shiny material, the spectrometer found large quantities of minerals that were completely different from those found in the surrounding areas of the surface, mostly composed of a mixture of materials containing carbonates and phyllosilicates in variable proportions.
Ms De Sanctis added that: “The false colour images of Haulani show that the material excavated from an impact is different to that on the surface of Ceres. This difference in the materials could mean either that there is a mixed layer under the surface of Ceres, or that the impact changed the localised properties of the minerals.”
The Occator crater, which is 92 km across and 4 km deep, has also been photographed in detail by Dawn. The latest images presented, taken from an altitude of just 385 km, show a dome in a smooth walled depression, located in the central, bright part of the crater. The dome has numerous, criss-crossing fractures running across the top and sides. Further fractures stand out clearly around the dome and across smaller, bright parts of the crater.
“Before Dawn started low-altitude observations last year, the Occator crater appeared to be a single, large, bright spot. Now, with the latest images, we can see complex structures that open new mysteries for us to investigate”, commented Ralf Jaumann,planetologist and co-investigator of the Dawn mission at the German Aerospace Centre (DLR) in Berlin. “The complex geometry of the areas inside the crater suggests recent geological activity, although we need to complete a detailed geological map of the crater in order to test out our hypotheses of its formation”, he added.
Barbara Negri, Universe Observation director at the Italian Space Agency, commented that “VIR is an infrared and visible light spectrometer, a type of instrument in which Italy has internationally-renowned scientific and industrial leadership. This type of instrument has been successfully used on other missions exploring the solar system, including CASSINI, ROSETTA and VENUS EXPRESS, providing fundamental data for studying the celestial bodies observed and understanding their origin”.
The team also completed an improved, colour map of the surface of Ceres, highlighting the range of materials and their relation with the dwarf planet's morphology, identifying larger stores of hydrogen around the planet's poles thanks to initial data from the Gamma Ray and Neutron Detector (GRaND) instrument. As hydrogen is the main component of water, this information strengthens the case for the presence of water ice close to the surface in Ceres' polar regions.