Save Phobos!

Mars has two "moons", both I think recaptured debris from an impact on Mars itself. The inner one is Phobos at semimajor 9376 km. That's 6000 km over Mars' surface. Too close: it's set to smash into said surface in a few dozen million years.

Add to this, that our people (well, Asian people) are seriously thinking of landing on Phobos for various reasons. Apparently the delta-V to Phobos is better than the delta-V to land on Mars proper. There's also the notion that incoming craft could land on Phobos first, scoop up its regolith (sand), and use that to brake en route to a Mars landing. And then there's Hop David's tether.

Mark me as unsure about any of this. 9376 / 6000 km is too close.

Mamerostationary orbit (I'm trying to keep at least to Italic; "Areostationary" mixes in Greek) runs at 20428 km semimajor, that is over the centre; 17032 km over the surface. This is well above Phobos; and below (smaller) Deimos at 23463 km semimajor but not by much. Currently Martian speculators don't want to orbit anything at mamerostationary altitude. Partly because Phobos and, to a lesser extent, Deimos exert tidal effects on it. Also because there are - like over Earth - only two decently stable longitudes to park the thing. (NB. they get 13634 km altitude which is wrong.)

Both moons are lost causes if left be. Mars is set to fling Deimos elsewhere, eventually. I've considered mining Deimos, 15 km long by 11 km diameter, into a "Rama" O'Neill station; but UPDATE 6/26/22 now I think on't that's difficult to square with a tether. (Magnets?)

Let's propose to boost Phobos to a mamerostationary altitude. Pretty sure an Orion or two could do that.

Phobos by contrast with runaway Deimos is actively dangerous to its planet. It's also over seven times the mass so that much less practical for geoforming. I submit there remains use for Phobos - just not where it's at. A mamerostationary or near-enough Phobos, especially as a standalone, would be a wonderful spot for a permanent station and we'd not worry (as much) about it crashing if we added too much weight to it. Park Phobos at 15 W. It won't be going anywhere; we'll not be worried about even millions of years, more like end-of-the-Sun timescale.

Something that massive at 15 W means its anticthon, at 165 E, is now Phobos' L3. That's fine too. Librate a small robo-station around that. That should be stable-enough, more stable than it is now anyway. MPL2 becomes a prime spot to receive visitors.

The bigger Phobos gets - in its new orbit - the better for its Lagrangians. Phobos is now 1.0659 × 10¹⁶ kg. For best Lagrangian results, the Martian anchor satellite (relocated Phobos, here) can get up to Mars/24.96 which is 2.56 × 10²² kg - compare Triton at 2.14. Smaller volume because I'm going for more density; therefore, surface gravity maybe 1 ms^-2. Big Phobos won't hurt Mars; it's not like Mars has tides.

ORION 12/17: From 9376 to 20428 km over Mars entails Hohmann transfer. Phobos-to-Deimos is 800 m/s so, let's stick that for the high bound. Dual Orion - or the Princeton deuterium drive - can do a lot with 800 m/s, certainly many kilotonnes. But not ten billion (10¹⁰) kilotonnes. I suggest mining Phobos for those resources' own sake, having the side-effect of lowering its mass some.

MERGER 12/22: How about using two Amors to boost this?