Wednesday, June 13, 2012

First atmospheric helium detections by LRO LAMP UV spectrograph

Depicted here are atmospheric emission spectra (black) obtained by LAMP on two dates in late 2011, in units of Rayleighs per angstrom. Each panel’s black line is the spectrum obtained by LAMP when its spectrograph slit was placed 83 deg from the nadir, just above the lunar limb. The red line in each panel is the background spectrum obtained close in time by observing the same patch of sky when it is at the zenith, where any contribution from the lunar atmosphere is minimized. The blue line in each panel is the difference spectrum obtained by subtracting the background from the limb spectrum, revealing native lunar atmospheric emission from He I at 584 Å. 1-sigma error bars are depicted on each curve every 4th spectral point, for reference.
Stern, et al

The LAMP far ultraviolet spectrograph aboard the NASA Lunar Reconnaissance Orbiter (LRO) has been used to search for helium, the lightest noble gas in the tenuous lunar atmosphere. We report here the first detection of lunar atmospheric He by remote sensing, and point to future observations that can address questions about its source, and to a search for native lunar atmospheric argon.

*Southwest Research Institute, Johns Hopkins University, Central Arizona College

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