Phobos could be loaded with iron, magnesium, and other metals of sorts. Because of the mineralogy of the moon, could it become a useful target for future plans similar to asteroid mining?
Phobos and Deimos to be visited and their samples collected in 2031, which could help determine possible mining opportunities in case they are comet remnants, as some ice can be seen in the picture below.
Phobos is not a particularly useful object for mining, at least short term (decades). The location and low escape velocity of Phobos also means care would be required that any attempt to mine it did not produce a debris ring/Kessler event in low Mars orbit.
It is fairly deep inside Mars' gravity well, so shipping metals to Earth or other locations is fuel intensive (at least 1 kilometer/second DV). Shipping from Moon to LEO is lower energy and much faster, and for other locations asteroids would seem easier to access. Shipping to mars surface is not hard, but since Phobos seems chemically similar to Mars mining the same material in situ is probably easier. It may be a way for Martin bases to access materials otherwise trapped deep beneath the surface, noting lack of volcanic activity or plate tectonics bringing deep material up but not enough is currently known about Mars, Phobos or hypothetical Martian bases to currently say*.
What would be useful in low mars orbit would be fuel and oxidizer, both for descent to mars and return to Earth, but it appears to be short on hydrogen compounds, and most viable rocket chemistries want large amounts of that. Water in particular would be useful but it appears warm enough that bulk ice will not exist.
In a much more distant future where humans on Mars might be looking to expand further out it would be a useful materials source for building space stations and orbital infrastructure, possibly including anchoring a space elevator.
In the shorter term it is most likely not particularly useful, though answer may change should a lander survive to get in samples.
*Diamonds and associated high temperature/pressure crystals are probably very rare in accessible Martian locations, and might be present on Phobos if it is actually an ejected chunk of proto Mars, but in absence of artificial forces Lab grown crystals will probably be meeting any Martian needs.
