DART Mission Reveals Asteroid Dimorphos Contains No Water

Careful scrutiny of the debris from the impact of NASA's DART mission into Dimorphos has not found any evidence for water-ice on the asteroid, nor the residue of thruster fuel from the spacecraft, new results from the European Southern Observatory (ESO) show. Space.com reports: However, the data from the MUSE (Multi-Unit Spectroscopic Explorer) instrument on ESO's Very Large Telescope in Chile does indicate differences in the size of particles in the debris, and show how the polarization of the light from the asteroid changed. These could both reveal details about the nature of the ejecta excavated by the impact, the recoil from which gave Dimorphos the biggest push. 'Before the impact, we were not really sure what to expect,' said Cyrielle Opitom of the University of Edinburgh in an interview with Space.com.

Opitom led a team who used MUSE to go in search of any water on Dimorphos. They observed the Didymos-Dimorphos system on 11 occasions, from just before the impact to about a month afterwards. MUSE is able to split the light from the double-asteroid into a spectrum, or rainbow, of colors, to look for emission at specific wavelengths that corresponds to specific molecules. In particular, Opitom's team searched the ejecta for water molecules and for oxygen that could have come from the break-up of water molecules by the impact. However, no evidence of water was detected. Dimorphos, at least, seems to be a dry asteroid.

There was also no evidence in the ejecta of traces of the hydrazine fuel that was on board DART, nor the xenon from its ion engine, although given their small quantities the non-detection is not a surprise. However, MUSE's observations were able to track the evolution of the cloud of ejecta (debris) thrown up by the impact, and in particular they helped determine the size distribution of the dust particles initially in the ejecta cloud and later in the tail streaming away from the asteroid. The research was published in the journal Astronomy & Astrophysics.

Read more of this story at Slashdot.