On what planet was a large rectangular outcrop that is composed mainly of sandstone first observed by an English astronomer born 1618?
Horrocks Block Horrocks Block ( ) is a large rectangular outcrop that is composed mainly of sandstone, lying on the north side of Venus Glacier, 2 nmi southwest of the Keystone Cliffs, on the east side of Alexander Island, Antarctica. It was mapped by the Directorate of Overseas Surveys from satellite imagery supplied by the U.S. National Aeronautics and Space Administration in cooperation with the U.S. Geological Survey, and was named by the UK Antarctic Place-Names Committee from association with Venus Glacier after Jeremiah Horrocks, the British astronomer who predicted and first observed a transit of Venus, in 1639.
Gullies on Mars Martian gullies are small, incised networks of narrow channels and their associated downslope sediment deposits, found on the planet of Mars. They are named for their resemblance to terrestrial gullies. First discovered on images from Mars Global Surveyor, they occur on steep slopes, especially on the walls of craters. Usually, each gully has a dendritic "alcove" at its head, a fan-shaped "apron" at its base, and a single thread of incised "channel" linking the two, giving the whole gully an hourglass shape. They are estimated to be relatively young because they have few, if any craters. A subclass of gullies is also found cut into the faces of sand dunes, that are themselves considered to be quite young. Linear dune gullies are now considered recurrent seasonnal afeatures.