New Photos Show Potential Landing Sites on Mars Moon
The ESA spacecraft Mars Express took this new image of the Phobos-Grunt landing area on March 7, 2010. The insert marks the proposed landing region and sites for Phobos-Grunt. See the full story.
Credit: ESA/DLR/FU Berlin (G. Neukum)

New photos of the Mars' moon Phobos reveal the Martian satellite as a strange, potato-shaped moon, and show potential landing zones being considered for a future robotic probe.

The images, taken by Europe's Mars Express spacecraft during a March 7 flyby, reveal the rocky Phobos in stunning detail with a resolution of just 14.5 feet per pixel. The new Phobos photos also show the proposed landing sites for Russia's forthcoming Phobos-Grunt mission, which is designed to bring samples of the Martian moon back to Earth.

The new images follow up on Mars Express' closest-ever flyby of Phobos on March 3. That pass did not yield any pretty pictures, however, as the research experiment ongoing at that time investigated the mass and gravity of the small moon.

The European Space Agency's Mars Express spacecraft orbits the red planet in a highly elliptical, polar orbit that brings it close to Phobos every five months. It is the only spacecraft currently in orbit around Mars whose orbit reaches far enough from the planet to provide a close-up view of Phobos.

Like Earth's moon, Phobos always shows the same side to its host planet, so in order to observe its far side a spacecraft must fly beyond Phobos' orbit and look inward. Mars Express did just that during three flybys on March 7, 10 and 13.

Phobos is the larger of the two moons of Mars. The smaller satellite is called Deimos.

Unclear origin

Scientists still remain puzzled over how Phobos came to be. The Martian moon is not spherical like most moons, and has an irregularly shaped body that measures about 17 miles by 14 miles by 12 miles.

Phobos appears to share many surface characteristics with so-called carbonaceous C-type asteroids, which suggests it might have been captured from this population.

However, it is difficult to explain either the capture mechanism or the subsequent evolution of the orbit into the equatorial plane of Mars.

Another explanation for Phobos suggests that it formed around Mars, and is therefore a remnant from the planetary formation period, ESA officials said.

Fetching some Phobos

In 2011, the Russian Federal Space Agency plans to send the Phobos-Grunt (meaning "Phobos soil") mission to land on the mysterious moon, collect a dirt sample and return it to Earth for analysis.

For operational and landing safety reasons, the proposed landing sites were selected on the far side of Phobos. This region was imaged by the High Resolution Stereo Camera (HRSC) on Mars Express during the July-August 2008 flybys of Phobos.

But new HRSC images showing the vicinity of the landing area under different conditions, such as better illumination from the Sun, remain highly valuable for mission planners.

It is expected that Earth-based ESA stations will take part in controlling Phobos-Grunt, receiving telemetry and making trajectory measurements.

Mars Express will continue to encounter Phobos until the end of March, when the moon will pass out of range. During the remaining flybys, HRSC and other instruments will continue to collect data.