Unique from landing on Mars itself what could we learn from Phobos that we couldn't learn from our own moon or from landing on Mars? Seeing as Phobos orbits Mars faster than the planet itself rotates, could there be any benefit from attaching a static probe to it's surface? Why have no
rovers probes been planned for landed expeditions on the most studied planetary orbital body in our solar system? Is it the immense dust layer? The complexity of orbital maneuvers within the range of Mars? Or simply because we haven't even scratched the surface of Mars, why try for one of it's moons?
I only ask because PADME and other articles lack details on what we stand to gain.
In addition to this, I've read that Phobos may be hollow in up to a third of its volume. This is the closest body that supports this "hollow asteroid" theory. Is studying a hollow moon of any scientific consequence? This is false as pointed out (citation needed).