THEMIS Looks at Phobos

These animations shows three views of the Martian moon Phobos as viewed by the Mars Odyssey orbiter. The apparent motion is due to movement by Odyssey’s camera, Thermal Emission Imaging System (THEMIS) rather than moon.

Each of the three panels is a series of images taken on different dates (from top to bottom): 29 September, 2017; 15 February, 2018; and 24 April, 2019. Deimos, Mars’ other moon, can also be seen in the second panel. These are visible light images, but THEMIS is mainly used for thermal-infrared scans.

Image Credit: NASA

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