Tuesday, 18 March 2014 - LPSC 2014

Lindy Elkins-Tanton
Contractions or Expansion of the Moon's Crust During Magma Ocean Freezing?

"The lack of contraction features on the Moon has been used to argue that the lunar magma ocean had limited depth, or else contraction during freezing would have resulted in thrust faults and scarps, as on Mercury. We show, however, that this interpretation is incorrect for several reasons. First, production of low-density plagioclase during lunar magma ocean crystallization may lead to expansion rather than contraction. Second, a hot floating crust undergoing contraction will develop viscous folding before it develops faulting, but the time-scale for folding is so short and happens so rapidly during contraction that even these resulting features are unlikely to survive relaxation or resurfacing. Recent GRAIL gravity measurements suggest that dikes were emplaced in the lower crust, requiring expansion. Our models are consistent with that measurement and interpretation, but we demonstrate that the existence of expansion does not constrain the depth of the lunar magma ocean."


Paul Byrne
Deep-Seated Contractional Tectonics in Mare Crisium, The Moon

"The lack of contraction features on the Moon has been used to argue that the lunar magma ocean had limited depth, or else contraction during freezing would have resulted in thrust faults and scarps, as on Mercury. We show, however, that this interpretation is incorrect for several reasons. First, production of low-density plagioclase during lunar magma ocean crystallization may lead to expansion rather than contraction. Second, a hot floating crust undergoing contraction will develop viscous folding before it develops faulting, but the time-scale for folding is so short and happens so rapidly during contraction that even these resulting features are unlikely to survive relaxation or resurfacing. Recent GRAIL gravity measurements suggest that dikes were emplaced in the lower crust, requiring expansion. Our models are consistent with that measurement and interpretation, but we demonstrate that the existence of expansion does not constrain the depth of the lunar magma ocean."


Jemma Davidson
Presolar Materials and Nitrogen Isotope Anomalies in the Unique Carbonaceous Chondrite Miller Range 07687

"Presolar grains are particularly abundant in pristine extraterrestrial materials such as interplanetary dust particles and in the matrices of the most primitive chondrites. They are sensitive indicators of nebular and parent-body processes. With the exception of nanodiamonds, whose origins are ambiguous, presolar silicates are the most abundant type of presolar grain and have been reported in high abundance in a number of primitive chondrites, including the CO3s Allan Hills (ALHA) 77307 and Dominion Range (DOM) 08006. Here we report the results of a NanoSIMS ion imaging study of the Antarctic carbonaceous chondrite Miller Range (MIL) 07687, which was originally classified as a CO3 but may be ungrouped. High presolar grain abundances (both O- and C-anomalous) indicate that this chondrite is of very low petrographic type, in agreement with petrographic observations."


Lindy Elkins-Tanton
Journey to a Metal World: Concept for a Discovery Mission to Psyche

"We propose to visit the exposed iron core of a protoplanet by sending a mission to Psyche, by far the largest exposed iron metal body in the asteroid belt. At Psyche we will explore, for the first time ever, a world made not of rock or ice, but of iron.

This mission would be a journey back in time to one of the earliest periods of planetary accretion, when the first bodies were not only differentiating, but were being pulverized, shredded, and accreted by collisions. It is also an exploration, by proxy, of the interiors of terrestrial planets and satellites today: we cannot visit a metallic core any other way.

For all of these reasons, coupled with the relative accessibility to low-cost rendezvous and orbit, Psyche is a superb target for a Discovery-class mission that would characterize its geology, shape, elemental composition, magnetic field, and mass distribution." 


Day 1    Day 2    Day 3    Day 4    Photos