Gale Crater's History BookGale Crater forms a large natural repository for much of Martian geologic history. This ancient impact scar has a diameter of about 154 kilometers (96 miles) and lies close to where the cratered highlands drop off onto the northern lowlands in Elysium. Based on its size and state of preservation, scientists estimate Gale formed over 3 billion years ago.
What draws scientific interest the most is a big mound of layered debris filling about a third of the crater's floor. Wrapping around the crater's central peak-visible at lower right in the image-the mound stands about 5.5 kilometers (3.4 miles) higher than the northern crater floor and about 4.5 kilometers (2.8 miles) above the southern floor. The mound's highest parts even rise somewhat higher than Gale's southern rim.
Image Credit: NASA/JPL-Caltech/University of Arizona/HI-RISE