Normally the Thermal Emission Imaging System (THEMIS) camera onboard the Odyssey orbiter is pointing towards the surface of Mars. Recently researchers developed a manuver to turn the orbiter around around so that a series of scans could be made of the Martian moon Phobos and they did just that on 29 September 2017.
The top image is a visible light image, actually part of a 19 image series that were put together into an animation. You can see the animation here (opens in a new tab) and the apparent motion you see is not from the motion of Phobos, rather it’s from the progression of the camera’s pointing during the 18-second span of the observation.
In bottom image the left edge of the small moon was in darkness, and the right edge in morning sunlight. Phobos has an oblong shape with average diameter of about 14 miles (22 kilometers). The distance to Phobos from Odyssey during the observation was about 3,424 miles (5,511 kilometers).
These and possibly future observations will allow researchers to analyze the surface-temperature information from this observation and possible future THEMIS observations to learn how quickly the surface warms after sunup or cools after sundown. That could provide information about surface materials, because larger rocks heat or cool more slowly than smaller particles do. The thermal information in this image is from merging observations made in four thermal-infrared wavelength bands, centered from 11.04 microns to 14.88 microns.
Phobos has an oblong shape with average diameter of about 14 miles (22 kilometers). Odyssey orbits Mars at an altitude of about 250 miles (400 kilometers), much closer to the planet than to Phobos, which orbits about 3,700 miles (6,000 kilometers) above the surface of Mars. The distance to Phobos from Odyssey during this observation was about 3,424 miles (5,511 kilometers).
THEMIS was developed by and is operated by a team based at Arizona State University, Tempe. NASA’s Jet Propulsion Laboratory, Pasadena, California, manages the Mars Odyssey mission for NASA’s Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, built the orbiter and partners in its operation. JPL is a division of Caltech in Pasadena.
Image Credit: NASA/JPL-Caltech/ASU