PARIS, Dec 5 - The plains of solidified lava that give the moon its quirky human-like face as seen from earth were created more than four billion years ago, according to a paper appearing tomorrow in Nature, the British science weekly.
The evidence comes from an unearthly silvery-grey stone that was blasted off the face of the moon, perhaps by an impacting asteroid, and then captured by Earth’s gravity, prompting it to fall to ground in Botswana.
In 1999, the 13.5kg remnant of this roving rock was found by local people near the village of Kuke, in the grasslands of the Kalahari Nature Reserve, who sold it to meteorite hunters.
The lunar heritage of the rock, named Kalahari 009, has been confirmed by a telltale signature of oxygen isotopes and ratio of iron to manganese in two volcanic minerals, olivine and pyroxene.
The nature of these chemicals puts the rock into the category of a mare basalt - a lava that flowed out smoothly onto the lunar surface before solidifying, forming dark plains that early skywatchers mistakenly took for seas, or mare'' in Latin. A new analysis of fragments of phosphate in Kalahari 009 puts the rocks at the whopping old age of 4.35 billion years, give or take 150 million years, the Nature study says. This implies that mare-type volcanism must have occurred at least as early as this date, just after the first stage of lunar crust formation, say the authors, led by Kentaro Terada of Hiroshima University in Japan and Mahesh Anand of Britain's Open University. Mare volcanism overlapped with a later stage of volcanism, evidence of which was found in rocks picked up by the Apollo missions. The man in the moon’’ is comprised of eyes made of the Mare Imbrium and Mare Serenitatis, a nose consisting of Sinus Aestuum, while the Mare Nubium and Mare Cognitum provide its mouth.
These and other mare account for nearly a sixth of the lunar surface, mostly on the side visible from earth.