According to a report issued by Purdue University, quoted by SpaceRef, a mission to Phobos, one of the moons of Mars, may provide evidence of microbial life on Mars for far less trouble and expense than a sample return mission to the Martian surface.
Phobos, a moon of Mars
According to NASA, Phobos is the larger and innermost moon of Mars. It is an irregularly shaped object 27 by 22 by 18 kilometers in diameter. It orbits Mars three times per day. It may be a captured asteroid, though some scientists dispute this. It is comprised of carbonaceous chondrite material similar to certain asteroids. It has been bombarded so frequently by meteor impacts that its surface has been reduced to powder. Phobos is spiraling down toward Mars so that in 50 million years it will either impact the Red Planet's surface or will break apart and form a ring, somewhat like Saturn's.
Phobos as an abode of Martian life
The Purdue scientists, some of whom were involved in the recent failed Russian Phobos-Grunt mission, suggests that Phobos may contain some microbial life from the Martian surface, according to SpaceRef. It is calculated that millions of years of asteroid impacts on Mars will have thrown up a great deal of material, some of which would be deposited on Phobos. Some of that material may contain Martian microbes that could survive, at least for a time, on Phobos.
A sample return mission to Phobos rather than to Mars
A sample return mission to Phobos, such as the recent failed Phobos-Grunt, might return Martian samples, including possible life, at a fraction of the cost of mounting a similar mission to the Martian surface. The European Space Agency has described a complex and expensive architecture for a Mars surface sample return mission, involving five separate space craft, and costing billions of dollars and taking place in the 2020s. However, due to cutbacks in NASA's planetary exploration program, such a mission is now very doubtful.
How a Phobos sample return would work
According to NASA, the Phobos-Grunt mission consisted of a lander and a return stage. The lander contained a number of instruments that would have studied the Phobos surface. The probe had a robot arm that would have scooped out a sample of Phobos soil and store it in the return stage. The return stage would have taken off and returned to Earth while the lander remained, studying Phobos. Phobos-Grunt was launched in 2011, but failed to boost into a trajectory to head for Mars. According to the Russian Space Web, the total cost of Phobos-Grunt would have been about 2.4 billion rubles, or about $163 million.
According to SpaceRef, a sample return mission for Phobos would take a 300-gram sample of Martian soil of which a small percentage would have originated on Mars. If microbial life is detected, the problems of quarantining such a sample will be a serious matter before proceeding with such a mission. On the other hand, a Phobos sample return mission could be attractive to NASA so long as its budget is constrained.
Mark R. Whittington is the author of Children of Apollo and The Last Moonwalker. He has written on space subjects for a variety of periodicals, including The Houston Chronicle, The Washington Post, USA Today, the L.A. Times, and The Weekly Standard.