A group of ancient lunar basaltic meteorites discovered

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Key findings-

• They found signs of a fundamental shift in the melting process on the Moon between 3.9 to 3.3 billion years ago.
• The new evidence points to the thermal evolution of the Moon as its interior melted in the form of basalt magmatism. 
• The new findings challenge currently proposed scenarios for the generation of basalts on the surface, which were found in the samples returned to the Earth by Apollo missions.
• A team of scientists have studied samples from lunar meteorite Asuka-881757, which was found in 1988 in Antarctica, lunar meteorite Kalahari 009 found in 1999 at the Kalahari Desert in South Africa, and samples collected by the Russian Luna-24 mission.
• They found the unique group of ancient lunar basaltic meteorites had a very low abundance of KREEP (potassium, rare-earth elements, and phosphorus). 
• This suggests that these meteorites must have come from a region different from the Procellarum KREEP Terrane (PKT) on the Moon and that there could be alternative ways of melting on the Moon.
• The study states that sample return missions have provided the basis for understanding the thermochemical evolution of the Moon. 
• Mare basalt sources are likely to have originated from the partial melting of the lunar magma ocean and then cumulating after solidification from an initially molten state.
• Analysis of the samples demonstrated that these basalts were generated at lower temperatures and shallower depths than typical Apollo mare basalts. 
• The Indian Space Research Organisation said 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.
• This finding suggests that the Moon’s interior melted in the form of basalt magmatism from as early as 4.3–3.9 billion years globally to a more localized scenario in the PKT region later around 3.8–3.0 billion years ago.

• ISRO said that 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 large mare regions on the near side of the Moon, that can be seen from Earth, mainly consists of basalts comprising volcanic rocks.
• 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 Apollo, Luna, and Chang’E-5 missions have brought to Earth an extensive collection of mare basalts. 

Note: Physical Research Laboratory (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.

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