Interesting Orbits Throughout the Solar System

[JoeStrout]

OK, next up: Mars.

Mars is 227 million km from the Sun, or about 1.5 AU.  So, solar power there (588.6 W/m^2) is only 43% of what we get near Earth.

But it's a somewhat more interesting system than Venus or Mercury because, of course, it has two moons.  However, both of these are quite small — much too small for a colony to orbit.  However, there are quasi-synchronous orbits around Mars which stay within a few km of Phobos, and I suspect (though have not found) that there are similar orbits for Deimos.  Those orbits would be interesting because of the ready supply of materials that Phobos and Deimos could provide.

 
It's not known exactly what these moons are made of; both are quite porous, similar to C-type asteroids, and it is speculated that Phobos may contain significant amounts of water.

So, from innermost to outermost, interesting orbits around Mars would be:

• Low Mars Orbit
• Phobos Quasi-Synchronous Orbit
• Mars Synchronous Orbit
• Deimos Quasi-Synchronous Orbit
  

Note that I didn't include a "high Mars orbit" — I don't at the moment see any advantage in orbiting at some arbitrary distance that's far from Mars, but without easy access to Deimos.  (But jump in if I've overlooked something!)

As for the Mars system in general, it's got no magnetic field, so full shielding would be needed (possibly even more than in cislunar space, since we're further from the Sun).  And Mars itself is a bit of a thorny source of materials, since its atmosphere is, as they say, "too thin to be useful, but too thick to ignore."

But on the other hand, it's clear that Mars will be a huge tourist destination, and it's in an important location halfway to the asteroid belt and outer planets.  For both reasons, a port city in orbit around it is sure to see plenty of economic activity — especially if (as seems likely) it turns out that you can't safely raise children in 1/3 G.