What Lies Beneath

Central peak Jackson crater seen obliquely
Spectacular contrasts of gray scale in the central peak of Jackson crater signal variations in both composition and maturity (degree of freshness of the surface). Image is 3100 meters wide, north is to the right, M1265842750LR [NASA/GSFC/Arizona State University].

What is the composition of the crust from top to bottom? It is relatively easy to measure the surface, but what lies beneath the surface? On the Earth geologists can dig and drill deep into the crust. We do not have that luxury on the Moon, at least not yet! However, we can take advantage of natural drill holes in the crust - impact craters! When impacts occur they dig into the crust and the central peaks expose the deepest material. Jackson crater formed on what was rather uneven terrain: to the east of the crater the elevation is about +6000 meters and to the west about +3000 meters. The bottom of the crater sits at +1000 meters, and the material exposed in the central peak comes from more than 1000 meters deeper still. By studying the rocks exposed in the central peak we can get a glimpse of materials that have come up from five or more kilometers below the surface (>3 miles).

Jackson crater east-to-west oblique (subsampled)
East-to-west view of Jackson crater (71 kilometers diameter). Image was acquired when LRO was at an altitude of 111 kilometers and the Sun was to the west of the crater (LROC was facing somewhat towards the Sun; phase angle 114 degrees). The central peak rises about 1800 meters above the crater floor and the top of the crater rim in the background has more than 4000 meters relief relative to the floor. Image width is about 64 kilometers and north is to the right, M1265842750LR [NASA/GSFC/Arizona State University].

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Published by Mark Robinson on 19 July 2019