NASA Odyssey Probe Captures Its First Infrared Photo of Phobos

The photo could tell us what Phobos is made of and where it came from.


We've been studying Mars for decades, and there are several satellites in orbit of the Red Planet right now, constantly sending back data from their telescopes and sensors. These satellites have mapped Mars pretty thoroughly, but the planet's two moons, Phobos and Deimos, are less well understood. Recently, NASA's Odyssey satellite took a break from observing the planet below to snap an infrared photo of one of the moons above.

Taking a Phobos photo was not easy for Odyssey. The spacecraft was only ever designed to point down at the planet, so NASA engineers had to design a new orbital maneuver to make it point upward at the moon. Once that was done, though, the team could use the THEMIS infrared camera onboard to take a multicolor shot of Phobos.

This image shows the different temperatures of the different sides of the moon. One side is being heated by the sun, so it's much warmer than the far side. In between, there's a heat gradient that shows how heat from the warm side is diffusing across the surface.

Scientists can learn a lot from an image like this one. Most importantly, scientists can tell what Phobos is made of based on how quickly heat travels across it. Different materials conduct heat more or less efficiently, so this is one important piece of evidence helping to determine Phobos' composition.

And that composition could tell us where Phobos originally came from. There are a lot of ways a moon like Phobos could get into orbit around Mars, and each possibility could have different ramifications for the history of the Martian system and its future.


For instance, many astronomers believe Phobos and Deimos are captured asteroids, but there is the possibility that both are remnants of a single larger moon that formed much like our own, from a giant impact billions of years ago. This theory posits that the original moon was unstable and broke apart into many smaller pieces, which eventually coalesced to form Phobos and Deimos.

One way to test this theory would be to find out what actually makes up Phobos. If it really is a captured asteroid, it should be made of the kinds of things asteroids are made of, while if it's a piece of Mars it should have more in common with Martian rocks. Analyzing this new data from Odyssey could settle the debate once and for all.

And perhaps if NASA has the time, it can figure out a way to get Odyssey to look at Deimos, too. Just for completeness' sake.

Source: NASA via Gizmodo

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