First, possibly the Caloris Basin in Mercury. Sound strange? Think : By the TEDF theory mercury should be almost 100% refractories as it formed in the hot plasma nearest the sun during the T Tauri formation phase. That means a high %age of it should be GOLD. Since the Caloris impact excavated the surface to a great depth...and AU79 is the only stable isotope.
A few other points : Mecury(and Venus as well)has almost no spin. This comes from the natural prograde spinning vortex of a condensing planet in the dust lane(CCW)being counteracted by the solar magnetic B dot field(CW)which decreases by the inverse cube of radial distance. That B dot field was vital to the sun’s existence as a more or less sphere(to begin fusion on the main sequence). Thus the “robbing” of M and V’s planetary spin as the orbital radius was increased.
Thus the B dot field pushes infalling gas/dust BACK OUT, transferring its spin angular momentum into the orbital momentum of the planets. Thus the sun has less than 1/5000th the SAM of the entire solar system. This of course comes from the original Mother Molecular Birth Cloud : inner edge orbits the center of the galaxy faster than the outer edge.
Thus the MMBC has a vast amount of SAM that has to be shed as the cloud shrinks gravitationally(ice skater’s faster spin as she draws her leg/arms inward). Otherwise the proto-sun would remain a flattened lenticular disc, the inner core whizzing around at the speed of light(perhaps a torus of hot plasma like an accrteion disc).
Since most stars are single, SOMETHING must be in orbit around them, taking up all that initial MMBC SAM. Thus the universe is LOUSY with planetary systems, thus another look at the Drake Equation is warranted.
Back to Mercury. The surface should be at least mildly radioactive from 4.5B years worth of solar/cosmic radiation, bring your lead lined space suits along with your drilling equipment(and sun umbrella too for fixed installations).
Thus you’re a GOLD MINER like california 150 years ago, but the purpose here, for the USA, is to pay off our mountain of debt, mostly to the chinese, with GOLD. All empires in history began with GOLD, yes(roman, spanish, english, american...)? Hey, it’s not that I have any LUST for gold(the love of money is the root of all evil), it’s just that we could re-invigorate the american economy by paying off the mountain of debt we’ve run up with a mountain of mercurian GOLD. Did you know that all the GOLD in the world would make only a cube 50 feet on a side?
Mars? Forget it, antarctica’s antarctica, you’d freeze your bippy PRONTO there, as well as explode and become a freeze dried mummy. No, I’d check out the Kuiper belt as well as the outer moons(charon, triton, miranda, etc)for the H2O/N2 richest one, then put it in close orbit around venus(like our own moon, thus making a 2nd “earth” in the solar system. You’d shoot chunks of it at the venusian terminator, increasing its retrograde spin whilst adding vital life-giving H and N to its atmosphere.
This would be much like the wet terran aboriginal ring system that was perturbed out of orbit by our captured moon, coating the(venusian/volcanic)earth with a layer of wet gravel that became our future oceans/lightweight continents(lunar regolith and continental isotope ratios are identical in the REFRACTORY elements).
Thus, many millenia from now we would be playing a joke on a future venusian Galileo : why do all the other planets in the solar system spin the WRONG WAY? No wonder then we’re so special, we spin WESTWARD.
I have it on good authority that the Athenian Empire began with SILVER!
"Thar's gold in them thar ... pits?"
Didn't the quest for gold bankrupt the Spanish? Ordinary rocks on the Lunar surface are "worth more" in (electrical) potential energy than gold on Mercury.
Still, Mercury seems a good source for heavy metals in general, and they will certainly be useful. Good choice.
"I’d check out the Kuiper belt as well as the outer moons(charon, triton, miranda, etc)for the H2O/N2 richest one, then put it in close orbit around venus(like our own moon, thus making a 2nd “earth” in the solar system. You’d shoot chunks of it at the venusian terminator, increasing its retrograde spin whilst adding vital life-giving H and N to its atmosphere."
Venus can be made habitable a lot more quickly than that. Just don't go all the way down to the surface.
The atmosphere of Venus is so thick that a spot can be chosen to float a "balloon city", actually more of a bathysphere, where the temperature and pressure are comfortably Earth-normal. Because the gravity would be Earth normal too, it would make a great getaway spot for honeymooners and tourists. Picture a humongous "love-bubble" rather than love boat and you've got the picture.
In addition to scientific research and carbon fiber and nanotube production, workers on Venusian city bubbles could dredge the surface for building materials, (or for gold), or operate mining robots down below.