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MAVEN Observes Mars Moon Phobos in the Mid- and Far-Ultraviolet

February 29

The orbit of MAVEN sometimes crosses the orbit of Phobos. This image shows the configuration of the two orbits in early December 2015, when MAVEN's Phobos observations were made. (Courtesy NASA/GSFC)

The orbit of MAVEN sometimes crosses the orbit of Phobos. This image shows the configuration of the two orbits in early December 2015, when MAVEN’s Phobos observations were made. (Courtesy CU/LASP and NASA)

NASA scientists are closer to solving the mystery of how Mars’ moon Phobos formed.

In late November and early December 2015, the MAVEN mission made a series of close approaches to the Martian moon Phobos, collecting data from within 186 miles (300 kilometers) of the moon.

Among the data returned were spectral images of Phobos in the ultraviolet. The images will allow MAVEN scientists to better assess the composition of this enigmatic object, whose origin is unknown.

MAVEN’s Phobos observations were made possible because of the special nature of the spacecraft’s orbit, which crosses a large range of altitudes, including those at which Phobos orbits Mars. Periodically, close approaches between the spacecraft and moon occur, representing an opportunity to gather data from close range. Getting so close might seem risky, but there is no real chance of a Phobos impact. Mission planners monitor MAVEN’s orbit carefully, and would execute spacecraft maneuvers if MAVEN came too close to the moon.

Comparing MAVEN’s images and spectra of the surface of Phobos to similar data from asteroids and meteorites will help planetary scientists understand the moon’s origin—whether it is a captured asteroid or was formed in orbit around Mars. The MAVEN data, when fully analyzed, will also help scientists look for organic molecules on the surface. Evidence for such molecules has been reported by previous measurements from the ultraviolet spectrograph on the Mars Express spacecraft.

Phobos as observed by MAVEN's Imaging Ultraviolet Spectrograph. Orange shows mid-ultraviolet (MUV) sunlight reflected from the surface of Phobos, exposing the moon's irregular shape and many craters. Blue shows far ultraviolet light detected at 121.6 nm, which is scattered off of hydrogen gas in the extended upper atmosphere of Mars. Phobos, observed here at a range of 300km, blocks this light, eclipsing the ultraviolet sky. On the dayside of Phobos, some bright blue pixels indicate that the moon is reflecting far-UV light, which will allow for the first time a measurement of Phobos' reflectivity at this wavelength, adding to an extremely limited database of measured far-UV reflectivity of small bodies in the solar system. (Courtesy CU/LASP and NASA)

Phobos as observed by MAVEN’s Imaging Ultraviolet Spectrograph. Orange shows mid-ultraviolet (MUV) sunlight reflected from the surface of Phobos, exposing the moon’s irregular shape and many craters. Blue shows far ultraviolet light detected at 121.6 nm, which is scattered off of hydrogen gas in the extended upper atmosphere of Mars. Phobos, observed here at a range of 300km, blocks this light, eclipsing the ultraviolet sky. On the dayside of Phobos, some bright blue pixels indicate that the moon is reflecting far-UV light, which will allow for the first time a measurement of Phobos’ reflectivity at this wavelength, adding to an extremely limited database of measured far-UV reflectivity of small bodies in the solar system. (Courtesy CU/LASP and NASA)

The observations were made by the Imaging Ultraviolet Spectrograph instrument aboard MAVEN.

MAVEN’s principal investigator is based at the University of Colorado’s Laboratory for Atmospheric and Space Physics, and NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the MAVEN project. Partner institutions include Lockheed Martin, the University of California at Berkeley, and NASA’s Jet Propulsion Laboratory.

The original NASA feature can be located here: http://www.nasa.gov/feature/goddard/2016/maven-observes-phobos-in-ultraviolet

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