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NASA Releases Rainbow-Colored Images of Martian Moon Phobos

Scientists say that the brightly colored thermal images, collected by the Mars Odyssey spacecraft, will help them better understand the moon’s origins

Six images of the Martian moon Phobos captured by NASA's Odyssey spacecraft. Three new images were released this month, giving scientists a fuller picture of Phobos' surface as it waxes and wanes. (NASA / JPL-Caltech / ASU / NAU)
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Three newly released images of Mars’ moon Phobos resemble brightly colored candies—and could lead to some sweet discoveries, too.

NASA’s Odyssey spacecraft captured these new images, with rainbow hues indicating temperature variations on the planet, according to a statement from NASA’s Jet Propulsion Laboratory. Using Odyssey’s infrared camera—a device known as is Thermal Emission Imaging System (THEMIS)—scientists took three pictures of the small moon in December 2019, and February and March 2020.

The December image captures Phobos at full-moon phase, when a large part of its surface is exposed to the sun and temperatures can rise as high as 81 degrees Fahrenheit. The February image shows Phobos eclipsed by Mars’ shadow entirely, when temperatures plunge to minus 189 degrees Fahrenheit, and the March image captures the moon in its waxing phase.

Scientists paired these new images with three other thermal images of Phobos taken from 2018 to 2019. Taken together, all six images show how Phobos’ temperatures change as it waxes and wanes over time. These are the highest resolution thermal images ever taken of Phobos’ surface, Bruce Dorminey reports for Forbes.

Mars has two moons: Deimos and Phobos. At just 16 miles across, Phobos is bigger than Deimos, but still relatively small compared to Earth’s moon, according to NASA. The moon flies so close to Mars’ surface that it orbits the planet three times a day. Phobos also moves six feet closer to Mars every year, which leads scientists to predict that in 50 million years or more, Phobos will either collide into Mars’ surface or break up into a ring of particles.

By studying the temperature variations on Phobos’ surface, scientists hope to gain clues about its material composition. “We’re seeing that the surface of Phobos is relatively uniform and made up of very fine-grained materials,” Christopher Edwards, the scientist who led analysis of the Phobos images, says in the NASA statement.

As scientists learn more about Phobos’ surface composition, they will be able to settle a long-contested question about the moons’ origin. As Mike Wall reports for Space.com, some scientists believe that Phobos used to be an asteroid that became trapped in Mars’ orbit. Others argue that the moon is a chunk of Mars itself, blasted off in a previous collision.

“These observations are also helping to characterize the composition of Phobos,” Edwards continues. “Future observations will provide a more complete picture of the temperature extremes on the moon's surface.”

To point Odyssey’s camera at Phobos, scientists had to flip the entire spacecraft upside down. “Taking an image of Phobos requires about six weeks to plan,” Jonathon Hill, a mission planner for THEMIS, says in an Arizona State University statement. “Mars Odyssey has to be flipped around to point away from Mars, take the image, and then flip back to point at Mars. During this process it is impossible for our antenna to maintain a lock on Earth, so we lose communications until the process is complete.”

In the next leg of its Mars exploration, NASA plans to launch its new rover, Perseverance, on July 20 of this year. The spacecraft will fly for about seven months to traverse the 314 million miles between Earth and Mars, as Smithsonian magazine reports. Once there, the robot will investigate conditions relevant to human survival on Mars and collect key samples of Martian rock to eventually send back to Earth.

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