What is it about?

Using lunar laser ranging and GRAIL gravity data we have estimated the polar flattening and the core radius of the Moon. We discover that a region of intersection is obtained between the observed core flattening with the theoretical (hydrostatic core within the non-hydrostatic lithosphere) model. This, in turn, brings down the uncertainty of the polar flattening and radii of the lunar core by a factor of 3 than before.

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Why is it important?

An improvement in the accuracy of lunar core size determination has direct implications for limiting the Earth-Moon formation scenarios, understanding systematic biases in the fundamental tests performed using lunar laser ranging data and in determining the free core nutation of the Moon. The work also contributes to the development of a more realistic lunar orbit and orientation model (also called lunar ephemeris).


It was an absolute delight to discover that those two curves (observed and theoretical) intersect. The timing of this article was a coincidence to the 50 years of Apollo, thanks to which the LLR data continues to be collected by various stations. I hope that this article ignites interest in new researchers to exploit the LLR data for more science returns in the years to come.

Vishnu Viswanathan

Read the Original

This page is a summary of: Observational Constraint on the Radius and Oblateness of the Lunar Core‐Mantle Boundary, Geophysical Research Letters, July 2019, American Geophysical Union (AGU),
DOI: 10.1029/2019gl082677.
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