Mars Odyssey Orbiter Takes Moon Phobos’ Temperature

These six views of the Martian moon Phobos were captured by NASA’s Odyssey orbiter as of March 2020. The orbiter’s infrared camera, the Thermal Emission Imaging System (THEMIS), is used to measure temperature variations that provide insight into the physical properties and composition of the moon. (Credit: NASA/JPL-Caltech/ASU/NAU)

(News from NASA’s Jet Propulsion Laboratory)

Three new views of the Martian moon Phobos have been captured by NASA’s Mars Odyssey orbiter. Taken this past winter and this spring, they capture the moon as it drifts into and out of Mars’ shadow. Combined with three previous images, these observations represent waxing, waning and full views of Phobos and show how the moon warms and cools.

Combination Figure2
Annotated version of the THEMIS data showing dates acquired. (Credit: NASA/JPL-Caltech/ASU/NAU)

The orbiter’s infrared camera, the Thermal Emission Imaging System (THEMIS), has been used to measure temperature variations across the surface of Phobos that provide insight into the composition and physical properties of the moon.

On Feb. 25, 2020, Phobos was observed during a lunar eclipse, where Mars’ shadow completely blocked sunlight from reaching the moon’s surface. This provided some of the coldest temperatures measured on Phobos to date: The coldest measured was about –189 degrees Fahrenheit (–123ºC). (THEMIS IR data overlain on a computer-generated visible image of Phobos). Credit: NASA/JPL-Caltech/ASU/NAU
Animation of images captured from the surface of Mars by NASA’s Curiosity rover showing Phobos rising out of the shadow of Mars on June 18, 2017.

Further study could help settle a debate over whether Phobos, which is about 16 miles (25 kilometers) across, is a captured asteroid or an ancient chunk of Mars that was blasted off the surface by an impact.

The Odyssey team plans to observe crescent phases in coming months, providing a comprehensive view of how Phobos’ surface warms and cools as it rotates.

Read the full press release here.

Mars Express images of Phobos (Credit: ESA)

Odyssey has been orbiting Mars since 2001. It takes thousands of images of the Martian surface each month, many of which help scientists select landing sites for future missions. Learn more about Mars Odyssey here.