The pictures are in!  The flyby maneuvers of Phobos performed by Mars Express were successful, returning lots of data and some beautiful, clear pictures of the moon.  While details of the radiometric study of Phobos’ density will be coming out later, ESA has already released the pictures showing the proposed landing site for Russia’s Phobos Grunt lander in 2012.  It’s a nice, clear area with a relatively level surface, perfect for a lander.  With this final detail, the Russian mission is set.  Originally scheduled for launch in 2009, the Phobos Grunt mission went through delays and schedule changes, as many space projects do, but now appears to be set for launch next year.  The probe will travel for 11 months, arriving at Phobos in 2012.  When it completes its mission, it will be the longest sample-return mission ever undertaken.

Phobos Grunt is a comprehensive mission to study both Phobos and Mars itself.  It will be conducting studies of Mars, Phobos, and their spatial environment (radiation, plasma, space dust, etc.).  While the return of Phobos surface material will be the tour-de-force, and undoubtedly will be the thing for which the mission is remembered, this is really a larger project regarding Mars and its entire area of space.

The probe will also be carrying a culture of Terrestrial bacteria as a biology experiment.  When the mission successfully returns its samples to Earth, the bacteria will be studied to determine the effects of the long space voyage.

The power for the operation of the probe will be supplied by two rectangular solar panels.  These will be folded down like the eaves of a roof during the voyage to Mars, then deployed in a standard “paddle-wheel” configuration during use.  Between these two panels will be a doughnut-shaped propellant tank, and in the hole of the doughnut will be the rocket that will be used for the return voyage.  This assembly will be connected by eight narrow struts to the ring-shaped landing gear underneath.  Before it is deployed, this entire unit will sit atop a completely separate propulsion system, which will be used for the pre-deployment maneuvers.

Phobos Grunt will go up in the same launcher with Yinghuo-1, China’s first mission to Mars, which will investigate one of the great mysteries of Mars: where did all the water go?  It is now abundantly clear that Mars had much more surface water in its youth than it does today.  The process that deprived Mars of its surface water is still only poorly understood.  Recent findings indicate that some of this water is now locked up in frozen subsurface deposits (see our articles on the Phoenix and Odyssey spacecraft) but exactly how it ended up there, leaving the planet’s seas and river systems dry, is something that will bear much further study.

The origin of Phobos is open to question.  It seems to share surface characteristics with some types of asteroids, which would indicate that it was captured from the nearby asteroid belt.  That scenario is perfectly believable, except for one detail: Phobos orbits Mars in a nearly circular path, exactly on Mars’ equatorial plane.  Now, if this were a random asteroid that had been captured, you would expect its orbit to be random; it probably would not be a perfect circle, and it probably would not be exactly on Mars’ equator.  That kind of symmetry is what we would expect from a body that had been formed along with Mars, in the original planet-forming period of the solar system.  In that case, Mars and its moons could have formed out of one big, spinning glob of dust and gas, and therefore would spin in the same plane.

So with Phobos (and its sister moon, Deimos, too) we see a body that looks like an asteroid, but orbits like something that formed along with Mars.  If it’s an asteroid- or a rubble pile composed of several chunks of asteroidal rock- then it’s hard to explain the orbit.  If it formed along with Mars in the distant birth of the solar system, then it’s hard to explain its surface characteristics.  This is the great enigma that is emerging about the two moons of Mars, and all research regarding them will be aimed at clearing up the question.  We haven’t even looked at Deimos in-depth yet, but when we do, all of the questions that are now being asked about Phobos will also be asked about it.  Where did these moons come from?  Exactly what are they?  In the years to come, we will be trying to find out, and Phobos Grunt will be an attempt to get closer to an answer.

There is also another mystery about Phobos: it just looks funny.  There are long, straight grooves running for many kilometers across its surface, as if it had been sandblasted.  That may be literally what happened: asteroid impacts on Mars in the distant past may have thrown up huge amounts of ejecta, reaching so high that it scored the moon’s surface.  Such asteroid collisions may have happened repeatedly throughout Mars’ early history, and provide us with still another possible origin for the Martian moons: they could be formed out of material thrown up from Mars by early collisions, then scored again and again by the ejecta from later collisions.

Alternatively, it is theorized that these grooves may be long, straight fissures in the underlying rock, into which surface dust has settled.  Phobos Grunt will be taking a closer look at these formations to determine which theory is correct.

Upon arrival in Mars orbit, Phobos Grunt will first study Mars’ magnetosphere and atmosphere, and release the Chinese Yinghuo-1 into Mars orbit.  When these operations are completed, the landing on Phobos will be attempted.  This operation is a bit challenging, simply because of the small size of the target.  Phobos is a rugged little rock about 20 or 30 km. wide (depends on which way you measure it; Phobos isn’t even close to a sphere) and simply hitting it will require some sharpshooting.  Landings on small objects are always a time of uncertainty and anxiety for the crew back on Earth; there are so many things that could go wrong.  If you’re a little off-target, you’ve missed the moon altogether, and if you hit it a bit too hard, you’ve smashed your multi-million-dollar probe.  Assuming that Phobos Grunt can get past this nail-biter, it will arrive on the surface of Phobos and collect its samples.  While the object of the mission is to return the samples to Earth for further study, the probe will be able to do some preliminary work on the spot.

Phobos Grunt will be carrying three instruments contributed by France’s Centre Nationale d’Etudes Spatiale.  One of these is a microscope that can see in visible and infrared wavelengths, which will be used to spot interesting places to collect soil samples.  An identical instrument was used with great success on the Rosetta mission (see article at this site).  The other French instruments are a gas-phase chromatograph and a laser spectrometer, which will be used to determine soil composition.   While the samples returned by Phobos Grunt will undoubtedly be studied for years to come, the preliminary examination by these instruments will give us some idea of what we have, without having to wait for the samples to arrive.

Simply getting the samples is only part of the job; they will then have to be returned to Earth.  The long voyage back will be the easy part.  The real anxiety starts when the ground crew starts to think about reentry.  Getting delicate samples to the ground intact has proven a problem in the past.  For instance, in the return of the samples from the Stardust comet mission (see our article), the sample capsule was damaged during the impact, nearly compromising the samples.  Disaster was narrowly avoided that time, but it’s a safe bet that the Phobos Grunt crew will be thinking about it when they try to bring their probe down.

Hopefully, everything will come out all right, and the Russians will have the world’s first samples of Phobos.  As part of their agreement with France, Roscosmos is sharing the samples with CNES.  Within days or weeks at the most, scientists all over the world will finally be able to learn something about this strange little body.

Even if the sample return is unsuccessful, this mission will give us some data about Mars and its largest satellite that will prove valuable for future researchers.  It’s a neat mission, and the spacecraft is a classy device that will probably be copied for other sample-return missions in the future.

As developments happen, you can read about them here.