Some several millions of years from now, Phobos is expected to spiral in towards Mars’ equator, probably disintegrating under tidal stress to form a dark ring around the ocher planet. But for the near term, spirals with one end on Phobos or Deimos will be of freight outward to the Moon and LEO, and of freight and hope-filled settlers inward to a sandy Martian destiny.

Compared to Earth’s Moon, of course, Phobos ( 12.4×14.3×17.4 miles ) and Deimos ( 6×7.4×10 miles ) are small “potatoes.” Yet this works out to a surface area of 1800 square miles for Phobos and 500 square miles for Deimos. [Compare with Rhode Island at 1212 square miles.] It has long been theorized that these moonlets are captured asteroids and indeed their reflectance spectra resemble that of carbonaceous chondrites, one of the major asteroid/ meteorite classes. This is what leads us to expect that they are rich in hydrogen, carbon, and nitrogen in one form or another as well as silicates and other oxides. The upcoming* Soviet PHOBOS mission ( see CLIPS page 4 ) will hopefully confirm this and set the stage for some very serious planning.

* [Unfortunately, this mission ended in failure.]

While it requires less energy for a round trip from LEO to the PhD twins than from LEO to the Moon, it is discreditingly ridiculous to suggest that LEO stations and depots get their liquid oxygen from the Martian moons rather than from the Moon. The Moon is handy all the time via a two or three day trip. The Martian moons are available only every twenty-five or so months and only via journeys from 6 months to two years long. Liquid hydrogen is quite another matter as the Moon cannot provide it ( barring rich polar deposits** ) and will need it even more than LEO. Hydrogen, methane, and ammonia can be processed on Deimos or Phobos and shipped to the Moon for perhaps a third of the cost of transporting them up the steep well from Earth — that is, discounting initial capital investment.

** [Lunar Prospector did discover ice reserves on the Moon at both poles in 1998. But this is a limited resource that, in our opinion, should be reserved for recyclable uses in food production, biosphere maintenance, and industry for lunar settlements, and not blasted out the nozzle of rockets in a squandering one-time use. – PK]

Now often one reads that the real action will be in “Earth-crossing” and “Earth-approaching” asteroids and / or / extinguished comets. The energy cost of round trips to these bodies will be even less than to PhD because one will not be infringing on even the shoulder of a planet-sized gravity well. But this expectation conveniently ( naively ? ) overlooks one of the paradoxes of celestial mechanics: the more neighborly are the orbits of two bodies ( e.g. Earth and asteroid 1982B ) the less frequent are the synodic launch windows between them. With such bodies we are talking about opportunities decades apart, not just every 25-26 months! That is not to say that unique one-shot opportunities shouldn’t be seized. But for regular trade in volatiles, Phobos and Deimos have it all sewed up.

If LEO ( low Earth orbit )-based commercial interest haven’t already developed volatile processing on these “hurtling moons of Barsoom”, any newborn Lunar settlement will be sure to do so as a matter of its own survival. An initial highly automated small crewed / tended station on Phobos / Deimos would be coupled with an advance Mars’ pre-exploration base that would continue Martian studies from orbit and via teleoperated rovers, planes, balloons, and dirigibles. As ( and if ) permanent habitation of this precociously legendary planet begins, the PhD outposts will grow into major transportation / logistics nodes adding some home-grown wares to the heavy equipment being transhipped to Mars from the Moon. Logical items: plastics and pharmaceuticals, both hydrocarbon rich, to be shipped both to the Moon and down to the rustic settlements on the frigid deserts below.

But how could humans live on Phobos or Deimos, except in rotating tours of duty, with their physiology-wise negligible gravities? One possibility: a maglev train of habitat-cars on a steeply ( 89+ degrees ) banked track within the lip of 3 mile wide Stickney crater on Phobos circling about every 114 seconds ( 307 mph ) would simulate the 0.38g of Mars itself.