Science Seminars

10/23/2014 Seminar – The early evolution of the Moon: Looking beneath the surface with GRAIL gravity data

Speaker: Jeff Andrews-Hanna (Colorado School of Mines)
Date: Sunday, Oct 23, 2022
Time: 4:00 pm
Location: SPSC W120

Seminar Abstract:

The geological record of the earliest history of the Moon is poorly preserved as a result of the heavy impact bombardment of the surface prior to 3.7 Ga.  However, the signatures of early lunar evolution are preserved in the subsurface.  Recent data from NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission is providing a view of the lunar subsurface at unprecedented resolution.  Linear gravity anomalies reveal a population of ancient igneous intrusions that likely formed during an early period of thermal expansion of the Moon, providing an important constraint on lunar formation.  Later intrusive activity was dominated by the formation of circular or arcuate dikes within the ring structures surrounding the major impact basins.  In the absence of ring dikes, the gravitational signatures of tectonic offsets across the rings reveal the nature of the basin ring tectonics.  The largest magmatic-tectonic structure revealed by GRAIL is a quasi-rectangular set of linear density anomalies ~2500 km in diameter, encompassing the Procellarum region on the lunar nearside.  The gravitational signatures of the Procellarum border structures are consistent with volcanically flooded rift valleys, formed by extension driven by the gradual cooling and contraction of the Procellarum KREEP terrain.  These and other observations from GRAIL are shedding new light on the early history of Earth’s nearest neighbor.