Phobos and Deimos


Mars has two small moons. Phobos, which is about 11.5 km across, was imaged on 26 March, 2019, as in moved across the face of the Sun from Curiosity rover’s post of view. Deimos, which is only about 2.3 km across, was 17 March. Phobos doesn’t completely cover the Sun, so Curiosity saw what could be considered an annular eclipse. Deimos is so small compared to the disk of the Sun, astronomers would say it transited the Sun.

Image Credits: NASA

Bonus GIF—This series of images shows the shadow of Phobos as it sweeps over Curiosity and darkens the sunlight near sunset on 25 March.

THEMIS, Deimos, and Phobos


These images of Phobos and Deimos, the moons of Mars, were taken by the Mars Odyssey orbiter’s THEMIS (Thermal Emission Imaging System) camera using visible-wavelength light. The apparent motion of the moon caused by the camera’s point-of-aimaim being moved during the 17-second span of the observation.

The distance to Phobos from Odyssey during the observation was about 5,600 km. The Deimos was almost 20,000 km away.

Image Credit: NASA

Phobos in UV


phobos-in-uvThis is the Martian moon Phobos as observed by the MAVEN spacecraft’s Imaging Ultraviolet Spectrograph. Orange shows mid-ultraviolet (MUV) sunlight reflected from the surface of Phobos. Blue shows far ultraviolet light which is scattered off of hydrogen gas in the extended upper atmosphere of Mars. Phobos blocks the background far UV light, eclipsing the ultraviolet sky. Comparing MAVEN’s images and spectra of the surface of Phobos to similar data from asteroids and meteorites may provide clues to the moon’s origin–whether it is a captured asteroid or was formed in orbit around Mars. The MAVEN data will also help scientists look for organic molecules on the surface of Phobos. Evidence for such molecules has been reported by previous measurements from the ultraviolet spectrograph on the Mars Express spacecraft.

Image Credits: CU/LASP and NASA