> It is a potentially hazardous object that is listed on the Sentry Risk Table with the second-highest cumulative rating on the Palermo Technical Impact Hazard Scale.
Bennu will be very close to Earth in around 150 years and there is a very tiny chance it might hit us, but part of me wishes we had the means to capture it in Earth orbit as a lower moon.
If it's below geostationary orbit, tidal forces will eventually bring it down. This is happening with Mars' moons for example, which are probably (naturally) captured asteroids. You would be committing the far future inhabitants of Earth to the impact, if they didn't have the means to boost the orbit.
I'm just speculating but maybe we could build a space station inside, using the shell as a natural radiation shield (apparently most asteroids contain material which can at least be made to be used that way).
There is also of course the immense flex factor for any organization that manages to pull off creating a new moon.
"Analysis of the gravitational and thermal effects has given a bulk density of ρ = 1190±13 kg/m3, which is only slightly denser than water. Therefore, the predicted macroporosity is 40±10%, suggesting the interior has a rubble pile structure."
Translation: if exterior is like interior, and interior is like suggested above, then this asteroid isn't a rock, but a whole lot of stones that just fly close together thanks to gravity. Gravity isn't a particularly strong force, so there may not be much to attach to, and if we'd start drilling, we'd probably just turn it into a slowly expanding pile of stones.
All you need for radiation shielding is enough mass that isn't itself dangerously radioactive that stays where you want it.
If you're trying to make a mass-efficient radiation shield, the choice of elements matters (lighter elements are better than heavy; polyethylene is one of the better ones because it incorporates a lot of hydrogen), but if you have a big enough asteroid, just start digging...
In space all mass is valuable. At least if your planning a expansionary timeline in orbit. Flying stuff up from the gravity well is expensive. Using in situ materials, especially if your not in a big hurry to fly them there, should be cheaper once the technology is developed.
It can also be worthwhile to capture asteroids into Earth orbit just to study them scientifically. It's way easier logistically to support human researchers when they are only a couple days' trip from home rather than a 6 month trip.
So who knows, maybe it's a piece of Mars, ejected a long time ago? Either way, worth looking into; we've studied so few space rocks that the marginal benefit of the first few we could capture will be huge.
https://en.wikipedia.org/wiki/101955_Bennu