Phobos is the larger of Mars’s two moons and very dark like Phoebe. For years investigators puzzled over the parallel grooves on Phobos until they realized they were formed by rubble which blasted into orbit during impacts and then spiraled back down over millennia and skittered to a halt ...
Impact craters and basins are found throughout the solar system. Some are quite large, such asHellasonMars, which is 8 km (5 miles) deep and about 7,000 km (4,350 miles) across, including the broad elevated ring surrounding the depression. ...