JMLAB

Therer will be a seminar on the origin of the moon

June 5, 13:30-

CPS Seminar room Location

Everbody is welcome

Shun-Ichiro Karato (Yale Univ.)

Composition and Origin of the Moon

I will discuss two issues on the composition and origin of the Moon. (1) Recent geochemical studies suggested that the lunar mantle may contain some water. However, the water content in the deep lunar mantle is poorly constrained by these geochemical studies on the surface rocks, and the reasons for a substantial amount of water, if there is, were unknown. (2) The Moon has remarkably similar isotopic compositions of refractory elements (e.g., Ti) to Earth, but the major element chemistry is substantially different. These chemical features challenge a commonly accepted giant impact model of origin of the Moon because most of these models predict that the lunar composition is similar to that of the impactor rather than the proto-Earth.

I will address these questions based largely on the results of mineral physics studies in my lab. I conclude that the lunar mantle is cooler than Earth’s mantle but contains much the same water content as in Earth’s asthenosphere. Most of these chemical characteristics of the Moon can be explained by the physics and chemistry of lunar formation if the important differences in properties between liquids and solids are considered.

Two issues on the lunar composition will be discussed that have important implications for the origin of the Moon based largely on the results of mineral physics studies in my lab: (1) Water content of the lunar mantle and (2) models o explain the lunar composition. I will show that lunar mantle has as much as water as Earth’s upper mantle. In addition to the similar water content, the lunar rocks show very similar isotopic compositions but substantially higher FeO content. I will provide a physical model to explain these chemical characteristics of the Moon within the framework of a giant impact model.