Memnonia Quadrangle - Craters

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. Since the collision that produces a crater is like a powerful explosion, rocks from deep underground are tossed unto the surface. Hence, craters can show us what lies deep under the surface. At times, bright rays surround craters because the impact has gone down to a bright layer of rocks, then thrown out the bright rocks on the darker surface. An image below from Mars Global Surveyor shows this.

• Bright rays caused by impact throwing out a bright lower layer. Some bright layers contain hydrated minerals. Picture taken with Mars Global Surveyor, under the MOC Public Targeting Program.

• Close-up of Columbus Crater, as seen by HiRISE.

• Nicholson Crater Central Mound, as seen by HiRISE. Click on image to see dark slope streak being diverted by an obstacle.

• Bernard Crater Floor, as seen by HiRISE. Large cracks are visible on floor.

• Dejnev Crater Floor, as seen by HiRISE. Scale bar is 500 meters long. Click on image to see large pits.

• Erosion of crater deposit in Lucus Planum, as seen by HiRISE under HiWish program.

• Close-up of layers in a pit on crater floor, as seen by HiRISE under HiWish program.

• Close up of crater floor showing yardangs and dark slope streaks,as seen by HiRISE under HiWish program.