Moonshots

Last month, NASA’s Mars Odyssey orbiter captured a new thermal image of Phobos, the larger of Mars’ two moons. Each color in the full-moon image represents a temperature range detected by Odyssey’s Thermal Emission Imaging System (THEMIS) camera. Each observation is done from a slightly different angle or time of day, providing new kinds of data.

The new, full-moon view is better for studying material composition, whereas earlier half-moon views are better for looking at surface textures. With the half-moon views, scientists could see how rough or smooth the surface is and how it’s layered. With the new full-moon views, scientists can gather data on what minerals are in it, including metals.

These three views of the Martian moon Phobos were taken by NASA’s Mars Odyssey orbiter using its THEMIS camera. Each color represents a different temperature range. The upper image was taken in a full-moon phase, which is better for studying material composition. The two views below were taken while Phobos was in a half-moon phase, which is better for studying surface textures. Image credit: NASA / JPL-Caltech / ASU / SSI.

Iron and nickel are two such metals. Depending on how abundant the metals are, and how they’re mixed with other minerals, researchers might be able to determine whether Phobos is a captured asteroid or a pile of Mars fragments blasted into space by a giant impact long ago.

Human exploration of Phobos has been discussed in the space community as a distant, future possibility, and a Japanese sample-return mission to the tiny moon is scheduled for launch in the 2020s. These and future observations could help future missions identify hazards and find safe areas to land of the surface.

Put a Ring on It

Mar’s largest moon, Phobos, has an inward-moving orbit that is sending it on a path toward Mars’ gravitational grasp. This could cause the moon to break apart and disintegrate into a planetary ring some 20 million to 40 million years from now, according to a study published Monday in the journal Nature Geoscience.

Researchers used a combination of simulations and models to analyze how Phobos’ orbit may evolve. They took a close look at the physical stresses Mars exerts on Phobos as the moon’s orbit causes it to gradually veer inward.

Phobos is a delicate moon with lots of pores and rubble on its surface which could contribute to it eventually crumbling to pieces under the red planet’s powerful gravitational pull. These fragmented pieces would then orbit Mars, forming a planetary ring.

Saturn’s rings are thought to have formed in a similar way, and some scientists speculate that Neptune’s moon Triton might be falling apart causing it to reach the same doomed fate.

The destruction of a planet’s moon or another passing object, such as an asteroid or comet, is one of the most common ways in which planetary ring systems form.