A reason to go to Mars

"Combs, Mike"> I still say that an orbital habitat built next-door to
a well-selected NEO would have all of the chemical elements available
to it as are available on the surface of Mars.

True. But its much easier and cheaper to set up a colony on Mars than
to build one from scratch. Mars allows us to cheaply test many
colonization concepts that will be needed in order to build permanent
habitats in solar orbit.

>
> "Combs, Mike"As could any Near-Earth Asteroid (NEA), with a
round-trip delta-V far less than for any object orbiting Mars.

The cost of delt-V would be insignificant if we're using the free
energy from the sun via light sails.

"Combs, Mike" Orbiting Mars, I have no doubt. But for any platform in
cislunar space, the moons of Mars would be uncompetitive sources of
raw material. They orbit inside the gravity well of Mars (Phobos,
very deeply inside). This means the gravity of Mars adds a
significant levy to the charge of transporting material. Especially
if we're only talking about radiation shielding, the moon is the most
economical source of raw materials.

Again, the cost of transporting material from the tiny gravitational
wells of the moons of Mars would be insignificant since once they were
easily transported off they surface they could be cheaply transported
almost anywhere in the solar system via light sails. So materials
from the deep gravity well of the Earth's moon would never be
competitive with material from the tiny gravitational wells of the
Martian moons.

Marcel F. Williams