Phobos First!!
This is a
proposition of sorts -- almost a
rallying cry, to which its rhythmic
alliteration lends -- for a goal of
space exploration, one which promotes having a series of missions to establish a
base on the
Martian moon of
Phobos as a precursor to a
mission to Mars. There are quite a few reasons why this makes sense (but objections to the notion as well). So why Phobos first? To begin with, look at the Phobian characteristics.
Firstly, Phobos sits in a stable, predictable, and relatively close
orbit around Mars. Unlike Earth's moon, which comes no closer than 360,000 km from Earth, the farthest distance from Mars reached by Phobos is about 9,500 kilometers. Put in another perspective, man-made satellites which track Earthly locations for
GPS devices are already about
three times as far out from the Earth as Phobos is from Mars.
Secondly, Phobos is a useful size -- just over 22 kilomoters in average diameter, giving it a surface gravity less than a thousandth that of the Earth. A
bicyclist who gets off to a good start off a steep ramp could escape the surface of this moon and return to space therefrom. Phobos is, in other words, gravitationally easy to land on, and easy to push off of (much more so than Earth's own moon). Mars, it must be added, is harder to set down upon than people may imagine. It has much higher gravity than Earth's moon, making a soft landing extremely difficult to pull off; and it has little atmosphere, so that both the winged approaches and parachutes commonly employed on Earth will be of little value. And so, once Phobos is manned, it may very easily be used as a base from which to send vehicles down to Mars, and receive shipments sent up therefrom, and from which to send and receive materials across the the much greater expanse between Earth and Mars.
Another advantage Phobos offers is its
structure and
composition. The surface of this somewhat
potato-shaped space object is heavily
cratered -- perhaps ominously so, insofar as inhabitants may be concerned, but these craters are themselves capable of offering inhabitants some measure of protection from the debris of space. Beneath that sturdily solid surface investigation suggests great veins of
ice are likely extractable as a source of both
oxygen for breathing and oxygen and
hydrogen for fuel. With the deposition of some heavy construction and mining equipment (again, much more easily accomplished on Phobos than on Mars), habitable spaces could be carved throughout the very rock itself.
Some more ambitious (perhaps even outlandish) proposals have been made. One is to use the same kind of technology now being considered for the deflection of threatening
meteorites to move the entire Phobian moon into an orbit more suitable for human usage as a waypoint. The same technology might be employed, it is supposed, to impart upon this small moon a spin sufficient to give the outer band of the
equator of that spin a
centrifugal force equal to the pull of the surface of the Earth. Simply put, some have supposed that the moon could be made to spin so fast that people standing in a tube encircling the planet could stand upside-down relative to the surface -- even as the poles remain essentially motionless. Another, following from the notion of moving the moon into a geosynchronous (or "aresynchronous") orbit, is to use Phobos as the space-side
anchor for a
space elevator linking the moon to the Martian surface directly.
These more ambitious aims have a decided ring of unrealism to them. The idea of spinning Phobos hard enough to create this reverse-gravity effect fails to consider the likelihood that the moon may be shoddily patched together, and could simply fly apart if subjected to that sort of
pressure. And though the space elevator notion would require less miraculous materials than the proposed Earthly space elevator, the capacity to create such a thing suggests technological advances sufficient to make simply landing on Mars a more palatable option.
And then there is the dust. Phobos has been struck by meteorites thousands of times, each instance kicking up dust and debris. But Phobos hasn't the gravity to cause this
debris to come crashing (or even wafting) down to its surface, so that which does not escape Phobian gravity just sort of floats there, above the surface, perhaps delicately balancing on a tall column of dust particles. Recall that with gravity a thousandth that of Earths, dust particles can float about that are a thousand times the mass of those able to simply float over the earth. (Don't get too excited, though; an object a thousand times the mass of a big speck of dust would still be a not-so-great grain of dirt). But whatever operations are to be carried out on Phobos must be done in the unsureness of a thick layer of such dust blanketing the surface.
But setting aside the more minor concerns -- and the wholly rhetorical objection that it seems a waste to aim so close to Mars without setting foot on the planet itself -- Phobos is a highly logical and accomplishable step for mankind's continued footsteps
out toward our destiny, in the stars.
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Not exactly a 'reference' but this CosmoQuest forum thread nicely captures some of the ideas -- and argumentation -- which this proposition raises.