Researchers at Ahmedabad’s Physical Research Laboratory have identified a hidden impact basin on the Moon, possibly older than the South Pole-Aitken basin. They used archived data from Chandrayaan-1’s Moon Mineralogy Mapper (M3), an imaging spectrometer.

The basin, called Australe, lies around the Mare Australe area. A circular spread of orthopyroxene and low-calcium, magnesium-rich basalts gave it away. The team also found 248 small basalt ponds.

The rim had almost vanished after billions of years of erosion, sedimentation and volcanic activity. The researchers used forensic mineralogical techniques to detect it, according to the reports. The study was published in The Planetary Science Journal.

Scientists estimate the Moon has about 300 impact basins, of which only 74 have been catalogued so far. The South Pole-Aitken basin is the Moon’s oldest and largest known impact crater.

Why it matters: the finding rewrites the timeline of the Moon’s early history and could guide exactly where future missions should land.