7 Nov 2016

Detection of water on asteroid named psyche


A UT professor has helped detect water on Psyche, the largest metallic asteroid in the solar system. The asteroid is the target of a proposed NASA mission.

Joshua Emery, the Lawrence A. Taylor Associate Professor of Planetary Science, co-authored the study with Driss Takir, a US Geological Survey scientist based in Flagstaff, Arizona. Takir, who carried out the telescopic observations of the asteroid, earned his doctorate from the UT Department of Earth and Planetary Sciences and studied under Emery.

The study, published in the Astronomical Journal under the auspices of the US Geological Survey and NASA, provides evidence for water-rich minerals on Psyche.

16 Psyche is one of the ten most-massive asteroids in the asteroid belt. It is over 200 kilometres in diameter and contains a little less than 1% of the mass of the entire asteroid belt. It is thought to be the exposed iron core of a protoplanet. It is the most massive metallic M-type asteroid. Psyche was discovered by the Italian astronomer Annibale de Gasparis on 17 March 1852 from Naples and named after the Greek mythological figure Psyche.

Radar observations indicate that Psyche has a fairly pure iron–nickel composition, consistent with it having the highest radar albedo of any asteroid in the asteroid belt (0.29±0.11). Unlike some other M-type asteroids, Psyche shows no sign of the presence of water or water-bearing minerals on its surface, consistent with its interpretation as a metallic body. Psyche seems to have a surface that is 90% metallic (iron), with small amounts of pyroxene.

Previous observations of Psyche had shown no evidence of water-rich minerals on its surface. However, new observations from the NASA Infrared Telescope Facility in Hawaii show evidence of water or hydroxyl on its surface.

While the source of these molecules on Psyche remains a mystery, scientists propose a few possible mechanisms for its formation. It's possible that water-rich minerals detected on Psyche might have been delivered by carbonaceous asteroids that impacted Psyche in the distant past.

Takir is a member of NASA's OSIRIS-REx mission and the Japanese Aerospace Exploration Agency's Hayabusa2 mission to collect carbonaceous samples from the water-rich asteroids Bennu and Ryugu. Emery also is part of the OSIRIS-REx project, the first US mission to collect a sample of an asteroid and return it to Earth for study.

Emery helped develop the goals and measurement requirements around which the mission has been designed. He leads a science team subgroup, the thermal analysis working group, that will examine measurements of heat emitted by the surface at different times of the day.

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