Hellas Quadrangle - Other Craters

Other Craters

Impact craters generally have a rim with ejecta around them, in contrast volcanic craters usually do not have a rim or ejecta deposits. As craters get larger (greater than 10 km in diameter) they usually have a central peak. The peak is caused by a rebound of the crater floor following the impact. Sometimes craters will display layers. Craters can show us what lies deep under the surface.

• Pedestal craters form when the ejecta from impacts protect the underlying material from erosion. As a result of this process, craters appear perched above their surroundings.

• Drawing shows a later idea of how some pedestal craters form. In this way of thinking, an impacting projectile goes into an ice-rich layer—but no further. Heat and wind from the impact hardens the surface against erosion. This hardening can be accomplished by the melting of ice which produces a salt/mineral solution thereby cementing the surface.

• Stair-stepping mesas in interior deposit of Spallanzani Crater, as seen by THEMIS

• Penticton Crater gullies, as seen by HiRISE

• Lipik Crater Channels, as seen by THEMIS.