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Martian moon in spotlight


G. Neukum / FU Berlin / DLR / ESA
  Use red-blue glasses to get a
3-D view of Phobos, and click on the image for a larger version.

Fresh imagery from Europe's Mars Express orbiter shows the Martian moon Phobos in sharp, 3-D detail. This isn't the first time Phobos has gotten its close-up, but interest in the irregular moon is rising - in part because it's increasingly seen as a steppingstone for Mars-bound astronauts.

Last month, NASA shifted its focus from sending humans back to the moon to a "flexible path" that includes the moons of Mars as potential destinations. The idea is that low-gravity locales such as Phobos (and Mars' other moon, Deimos) should be easier to get to because they're more accommodating for landing and ascent.

Phobos - a pockmarked, potato-shaped lump that measures only 17 miles (27 kilometers) in its widest dimension - could well serve as the prime staging ground for telerobotic operations on the Martian surface, or for eventual human landings on Mars.

But first, scientists want to figure out what Phobos is made of.

That's the aim of a $72 million Russian-Chinese mission known as Phobos-Grunt ("Phobos-Soil" in Russian). The current plan calls for the probe to be launched from Russia's Baikonur Cosmodrome in Kazakhstan in 2011, aiming for a soft landing on Phobos. The lander would dig up samples of rock and soil, load them into a return capsule and send them back to Earth. Meanwhile, a Chinese-built microsatellite would go into Martian orbit.

The newly released pictures from Mars Express, acquired on March 7, focus on the area where Phobos-Grunt is expected to land  - and they provide some good news for the sometimes-troubled mission.

"We got very good images of the proposed landing sites for Phobos-Grunt … better than anything before," Gerhard Neukum, a professor at the Freie Universität Berlin and principal investigator for Mars Express' high-resolution camera, told me today. "It's difficult to see [the area] under sunlit conditions. We tried to make the timing in such a way that we would get the best positions possible."

These pictures were taken from a distance of 80 miles (130 kilometers), yielding a resolution of 14 feet (4.4 meters) per pixel. Previous views of Phobos have achieved a higher resolution, but the Phobos-Grunt sites were seen edge-on or in shadow. The new images were designed to verify that mission planners made the right choice for their landing site.

"If it showed a very rough terrain, they might change it. … Fortunately, the area they chose originally is not too bad. It's relatively smooth," Neukum said. "It's not as dangerous as other areas where they could land. We don't see any big impact close by, so there shouldn't be any big blocks."

G. Neukum / FU Berlin / DLR / ESA
Mars Express' view of the moon Phobos provides a good look at the proposed
landing sites for the Phobos-Grunt probe, shown as red dots in the inset photo.

Phobos poses plenty of mysteries: Is it an asteroid that was gravitationally captured by Mars, as its shape and composition suggest? Or did it come into existence along with the Red Planet, as its orbit suggests? Is it actually a big piece of Mars that was struck off by a meteor impact? Does ice lie beneath its surface? Could material blasted away from Mars settle onto Phobos' surface, and might some of that material contain evidence of life?

One of the experiments hitchhiking on Phobos-Grunt is designed to find out whether organisms could survive the trip from Mars to Earth - testing a hypothesis for life's interplanetary spread known as "panspermia."

Yet another proposed mission to Phobos, called PRIME, would take a close look at feature that seems to be a monolith rising up from the moon's surface. "When people find out about that, they're going to say, 'Who put that there? Who put that there?'" Apollo moonwalker Buzz Aldrin observed in a widely distributed video clip. "Well, the universe put it there. If you choose, God put it there."

Mars Express isn't done with Phobos yet: Neukum said scientists are still analyzing the data from a March 3 flyby that was aimed at mapping the moon's gravitational field and internal structure. Still more flybys are planned in the weeks and months ahead, including a series that should bring the orbiter within 37 miles (60 kilometers) of Phobos' surface.

Neukum is looking forward to those improved views of Mars' mysterious moon. "We are not disappointed, but we could have done better," he told me. "There will be more opportunities."

More on Mars' moons:

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