OH ON THE MOON, REFLECTANCE SPECTROSCOPY, CARLE PIETERS, AND M3

Reflectance spectroscopy as a remote sensing technique began its modern era in the 1960s with the development of electronic detectors that could measure radiation from afar at UV, visual and infrared wavelengths, and with precision and sensitivity to detect solid-state absorptions. Spectrometers were built and used, first on groundbased telescopes, and then carried by spacecraft, to study objects in the Solar System¹. We at M.I.T. were one of the first research groups to utilize this new technology. Carle Pieters was one of the first graduate students to join our new and growing research group. She began by studying the Moon, wrote her dissertation on composition of lunar basalts, using the telescopic data she acquired, and built an impressive career around this field, focused on the Moon. The technique has become widely accepted, with a spectrometer on almost every spacecraft mission to other Solar System objects. The Moon was first the focus of the new Solar System Exploration Program and central to the development of planetary science, but the focus quickly moved to Mars and farther out objects. After decades of focused effort, she managed to create her own team and investigation, and recently, to put a spectrometer (M3) in orbit around the Moon. Spectacular data have resulted, with the expected discoveries, many built on her prior laboratory and theoretical work. As an example of the import of her contribution, I will discuss today one of the M³ discoveries, OH and water in the lunar soil. In summary, M³ discovered absorption features in the lunar reflected solar spectrum in the 3-µm spectral region that are interpreted as indicating OH and perhaps H₂O in the lunar surface particles. The origin and nature of these molecules in what was thought to be a very dry Moon and what the M³ data indicates about them is my subject. Solar wind proton induced hydroxylation is our leading hypothesized process², making this discovery of import to all inner solar system airless bodies.

¹ McCord, T. B. (2010), Recollections of the developments of reflectance spectroscopy …, Proc. of the ASD and IEEE GRS; Art, science and applications of reflectance spectroscopy symposium, Vol. II, Boulder, CO. www.asdi.com.

² McCord, T. B. et al. (2010), Sources and physical processes responsible for OH/H₂O in the lunar …, JGR, submitted.