Origins Unsure: ‘Cranium Hill’ Rock – NASA Science

Written by Margaret Deahn, Ph.D. Pupil at Purdue College

Final week, NASA’s Mars 2020 rover continued its journey down decrease ‘Witch Hazel Hill’ on the Jezero crater rim. The rover stopped alongside a boundary seen from orbit dividing mild and darkish rock outcrop (also referred to as a contact) at a web site the crew has referred to as ‘Port Anson’. Along with this contact, the rover has encountered quite a lot of neat rocks that will have originated from elsewhere and transported to their present location, also referred to as float.

Pictured above is an statement named ‘Cranium Hill’ taken by the rover’s Mastcam-Z instrument. This float rock uniquely contrasts the encircling light-toned outcrop with its darkish tone and angular floor, and it options a number of pits within the rock. When you look intently, you may even spot spherules inside the surrounding regolith! See Alex Jones’ current weblog publish for extra info on these neat options: The pits on Cranium Hill could have shaped through the erosion of clasts from the rock or scouring by wind. We’ve discovered a number of of those dark-toned floats within the Port Anson area, and the crew is working to raised perceive the place these rocks got here from and the way they acquired right here.

Cranium Hill’s darkish colour is harking back to meteorites present in Gale crater by the Curiosity rover: Chemical composition is a crucial consider figuring out a meteorite, and Gale’s meteorites include important quantities of iron and nickel. Nonetheless, current evaluation of SuperCam knowledge from close by related rocks suggests a composition inconsistent with a meteorite origin. 

Alternatively, ‘Cranium Hill’ may very well be an igneous rock eroded from a close-by outcrop or ejected from an impression crater. On Earth and Mars, iron and magnesium are a few of the foremost contributors to igneous rocks, which kind from the cooling of magma or lava. These rocks can embrace dark-colored minerals corresponding to olivine, pyroxene, amphibole, and biotite. Fortunately for us, the rover has devices that may measure the chemical composition of rocks on Mars. Understanding the composition of those darker-toned floats will assist the crew to interpret the origin of this distinctive rock!