Group of lunar meteorites throw light on origin of basalts on Moon: ISRO

A team of scientists from Ahmedabad-based Physical Research Laboratory (PRL), the United States and Japan has found a unique group of ancient lunar basaltic meteorites, suggesting a new scenario for the origin of lunar basalts, according to ISRO.

PRL, which is a unit of the Department of Space, carries out fundamental research in select areas of physics, space and atmospheric sciences, astronomy, astrophysics and solar physics, and planetary and geo-Sciences.

The Indian Space Research Organisation (ISRO) issued a statement on Thursday saying the Moon's dark regions that are visible to the naked eye, known as the 'mare', are remnants of a violent history of the Solar System. There are no records, though, of these frenzied events on Earth.

The Moon, having changed very little over billions of years, provides us a window to ponder over the past. The large mare regions on the near side of the Moon, that can be seen from Earth, mainly consists of basalts comprising volcanic rocks, it said.

These regions hold the key to how the Moon cooled and evolved besides providing information on what were the sources of heat that melted and crystallised the material to the present day rocks, the Bengaluru-headquartered national space agency said.

The Apollo, Luna, and Chang'E-5 missions have brought to Earth an extensive collection of mare basalts. Apollo mare basalts date back to the age of 3.83.3 Ga (Ga is one billion years) and were collected from a region that is highly rich in potassium, rare earth elements, and phosphorous known as Procellarum KREEP Terrane (PKT), it was noted. KREEP is the acronym for a place that has deposits of potassium (chemical symbol - K), rare earth elements (REE) and phosphorus (chemical symbol - P)

These are rich in radioactive elements that provide the heat to melt rocks resulting in KREEP-rich basalts. The team of scientists from PRL, USA and Japan have found a unique group of ancient lunar basaltic meteorites with very low abundance of KREEP, according to ISRO.

"This suggests that these meteorites must have come from a region different from PKT. The samples studied in this work are: Lunar meteorite Asuka-881757 found in 1988 at Antarctica, collected by National Institute of Polar Research, Japan; Lunar meteorite Kalahari 009 found in 1999 at Kalahari Desert in South Africa; and samples collected by Russian Luna-24 mission," it said.

ISRO stated the calculations show that these basalts must be a result of low-pressure melting in the Moon, similar to those in other terrestrial bodies, such as Earth and Mars. Further, they also reveal that these basalts originated from a cool, shallow, and compositionally distinct part of the lunar interior.

"This finding suggests that the Moon's interior melted in the form of basalt magmatism from as early as 4.33.9 Ga globally to a more localised scenario in the PKT region later (3.83.0 Ga). Fundamentally these new results challenge currently proposed scenarios for the generation of basalts and propose an additional new regime that might be more common on the Moon globally," the space agency added.