An Exogenic Origin for the Volatiles Sampled by the LCROSS Impact

Returning humans to the Moon presents an unprecedented opportunity to determine the origin of volatiles stored in the permanently shaded regions (PSRs), which trace the history of lunar volcanic activity, solar wind surface chemistry, and volatile delivery to the Earth and Moon through impacts of comets, asteroids, and micrometeoroids. So far, the source of the volatiles sampled by the Lunar Crater Observation and Sensing Satellite (LCROSS) plume (1, 2) has remained undetermined. We show here that the source could not be volcanic outgassing and the composition is best explained by cometary impacts. Ruling out a volcanic source means that volatiles in the top 1–3 meters of the Cabeus PSR regolith may be younger than the latest volcanic outgassing event (~ 1 billion years ago; Gya) (3).

Lunar Crater Models

This article traces the story of three amateur astronomers who created relief models to help them depict the changing illumination of certain lunar craters, examples of which can be found in UK museum collections today. English chemist Henry Blunt (1806–1853) adopted the emerging technology of electrotyping to reproduce and distribute his plaster model of the Eratosthenes crater to a wider audience. Scottish industrial engineer James Nasmyth (1808–1890) used a combination of drawing, modelling and photography to support his thesis on the volcanic origin of lunar craters in his popular book The Moon Considered … (1874). Spanish sculptor Dionis Renart (1878–1946) produced a series of plaster models for the Exposición General De Estudios Lunares (1912) that eventually came to Greenwich via the British selenographer Hugh Percy Wilkins (1896–1960). These three case studies provide us with valuable insights into the rationale behind the production, use and distribution of lunar crater models within amateur and popular astronomy.