American researchers, in collaboration with IRAP, discover large quantities of water ice at the poles of Mercury. Scientists of the MESSENGER mission, in orbit around Mercury since March 2011, just highlight the large amount of water ice deep inside the craters which are always in the shade. They publish this discovery in the journal Science this week.
At the surface of the planet closest to the Sun, it is either very hot, either very cold : every bit of its surface is heated to around 400°C as it passes in front of the sun and drops to about -170°C on the night face (a day lasts ~ 58 terrestrial days on Mercury). Scientists have long thought that a few privileged places could escape this vicious cycle, the bottom of impact craters that never see the sun because they are very close to the poles. Their temperature should never exceed -180°C.
A key element of this discovery is the neutron spectrometer led by D. Lawrence, Applied Physics Laboraory, Maryland. Sylvestre Maurice, an IRAP researcher, has actively participated in the analysis and the interpretation of the data coming from this instrument, which highlights the presence, in these ‘dark’ craters, of likely pure water ice under a layer of dry dust of about 10 cm width . This water comes from the impact of several comets on Mercury over the past billion years.
Note that this is the same kind of instrument, and part of the same team (D. Lawrence, W. Feldman, S. Maurice), which in the past has highlighted the presence of water ice at the poles of the Moon (1998) and on the surface of Mars (2004).
- Sylvestre Maurice, IRAP (CNRS/Université Paul Sabatier-Toulouse III)
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