... Sedimentary Mars . ... The total mass within giant galaxy cluster CL0025+1654, about 4.5 billion light-years away, produces a cosmic gravitational lens -- bending light as predicted by Einstein's theory of gravity and forming detectable images of even more distant background galaxies. ... Stephan's Quintet is a picturesque but clearly troubled grouping of galaxies about 300 million light-years away toward the high-flying constellation Pegasus. ... Our Moon's appearance changes nightly. ...