Is Hydrolox superior to methalox for large lunar-based craft?

[InterestedEngineer]

Mine impactors for carbon and there is a lot of carbon on the moon.

If they have the infrastructure required to mine buried carbonate impactors on the moon, it implies they've already solved the reusable-lander problem you are trying to solve by mining buried carbonate impactors.

It's the Catch-22 with a lot of higher-end ISRU proposals. They typically aren't viable until they aren't necessary.

Can one find such with remote detection from a lunar orbiter?

Possibly for metallics, but I doubt you could detect buried carbonate impactors. (Other than optically: "Crater, crater, crater...")

I know people working on terahertz radar.  combine that with ground penetrating radar or neutron spectroscopy and you might be able to remote detect carbon concentrations on the Moon.

[redneck]

As someone mentioned recently, nitrogen might be a more serious shortage than carbon. Does anyone have an idea of if it can be sourced from the moon?