NASA’s Mars Science Laboratory Curiosity rover has taken the first high-resolution images of the martian moons Phobos and Deimos as they passed in front of the Sun.

The images were taken by the vehicle’s Mast Camera as Curiosity continues on its journey to its first science destination area, dubbed Glenelg. Although images of the two moons have been taken previously from the surface, this is the first time pictures of such high resolution have been obtained. They will allow scientists to assess details of the transit of the moons over Mars and provide new insight into the internal structure of both the planet and its orbiting bodies, says Texas A&M University atmospheric scientist and Curiosity co-investigator Mark Lemmon.

Deimos orbits Mars every 30 hr., and like the Sun, rises in the east and sets in the west. Phobos is much closer to the martian surface and crosses the sky every 8 hr., while rising in the west and setting in the east. “Phobos will eventually break up and fall onto Mars,” Lemmon says.

Curiosity has meanwhile passed the halfway point on its way to Glenelg, having traveled an additional 30 meters in its most recent drive. The rover, which has now journeyed 289 meters from its landing zone, also has parked at a target rock that will be analyzed by the mast-mounted Chemistry and Camera (ChemCam) and the Alpha Particle X-Ray Spectrometer, which identifies chemical elements. This will be the first opportunity for Curiosity to perform “surface contact” science.

The rover also is nearing an area containing lighter material that looks similar to heat-retaining areas spotted from orbit by the Mars Reconnaissance Orbiter. “The material has a relatively higher thermal inertia, which is the ability to retain heat,” says John Grotzinger, project scientist at the California Institute of Technology in Pasadena. “We don’t know why this is. But we’re getting closer to it. We are also getting closer to thin beds of darker rock, which may be inter-bedded with the lighter units.”