Thanks to measurements by the D-CIXS X-ray spectrometer, ESA’s SMART-1 spacecraft has made the first ever unambiguous remote-sensing detection of calcium on the Moon:
http://www.esa.int/SPECIALS/SMART-1/SEM4711DU8E_0.html

I would have to dig into Apollo 15 and 16 command/service module x-ray spectrometer published papers and abstracts to see if their claim is true. It could well be, if only because of higher spectral resolution than the Apollo instruments provided.

But I still have a sour taste in my mouth after the big ESA trumpeting of the discovery of low latitude ice-rafts south of Elysium two months ago, with a total lack of recognition or credit that that had already been the conclusion of other groups based on Mars Surveyor and/or Odyssey data 2 years earlier.

I am not sure about Apollo orbital data, but I know all three Luna sample returns and Apollo 16 samples had some calcium, even if Luna 16 and 20 returned samples slightly depleted of it.

http://adsabs.harvard.edu/cgi-bin/nph-bib_...42a8584b1826314
http://adsabs.harvard.edu/cgi-bin/nph-data...42a8584b1826784
http://adsabs.harvard.edu/cgi-bin/nph-data...42a8584b1828221


Clementine also studied Calcium ratios.

http://adsabs.harvard.edu/cgi-bin/nph-bib_...42a8584b1830046

Calcium is a major rock forming element, present in feldspars and pyroxene's, major minerals in the basalt lavas and anorthosite igneous rocks of the moon.

I did a quick search on the Apollo x-ray spectrometer using Google and only found references to Aluminum, Silicon and Magnesium relative abundance mapping, so if calcium was detected, it was not with enough signal/noise ratio to be mappable.

A complete Moon-wide XRS map of magnesium is considered one of the most important short-term goals remaing for lunar science, given that element's particular importance in understanding lunar formation processes.

What seems odd to me about any excitement over finding calcium on the Moon is that plagioclase is a mineral made up of silica, aluminum and calcium (and other trace elements). And the Moon's crust was formed from an ocean of plagioclase, creating the anorthositic gabbro that forms most of the current surface.

That right there would argue for there being a considerable amount of calcium on the Moon, and for people to have known this for quite a while.

The only reason I can think of for calcium to be an as-yet undetected major lunar element would be if the plagioclase on the Moon is somehow different from terrestrial plagioclase. And we have a fair amount of plag in the lunar samples -- has there been some calcium anomaly detected in the lunar samples?

-the other Doug

This might be a case of it being known to exist, but not directly measured before from orbit.

Not that I know anything about this.

Phil

I believe that is the case -- from my admitttedly rather fuzzy memory of the data from the Apollo 15 and 16 XRS orbital surveys, Ca was not listed as one of the elements detected (and indeed was not intended to be).

Forget gold - there's oxygen in them thair Moon rocks!

http://science.nasa.gov/headlines/y2006/05....htm?list161084