The Chandra observations (right) of the bright portion of the Moon detected X-rays from oxygen, magnesium, aluminum and silicon atoms. The X-rays are produced by fluorescence when solar X-rays bombard the Moon's surface. Chandra's observations have also solved a decade-long mystery about X-rays detected by ROSAT that were thought to be coming from the dark portion of the Moon. It turns out that these X-rays only appear to come from the Moon. Chandra shows that the X-rays from the dark moon can be explained by radiation from Earth's geocorona (extended outer atmosphere) through which orbiting spacecraft move.
Optical: Robert Gendler; X-ray: NASA/CXC/SAO/J.Drake et al.
CHANDRA X-ray Observatory CXC Operated for NASA by SAO, url=<a rel="nofollow" class="external free" href="http://chandra.harvard.edu/photo/2003/moon/index.html">http://chandra.harvard.edu/photo/2003/moon/index.html</a>