Deciphering the Luna Crater in India

In the Kutch district of northwestern India, a vast desert, where salt is harvested in colorful rectangular ponds, stretches to the Arabian Sea. In an adjacent grassland, a less conspicuous circular feature has attracted attention in recent decades. Scientists in India had suspected, but not confirmed, that an object from space had left this mark on the landscape. Now a geochemical analysis of the structure has revealed that it contains the characteristic features of a meteorite impact.

Impact craters on our planet are a relative rarity; fewer than 200 structures from around the world have been confirmed in the Earth Impact Database. The number of craters is so modest in part because many of the meteorites that survive the journey through Earth’s atmosphere eventually end up in water. Meteorites that fall on land can have evidence of their impact erased by forces such as wind, water and plate tectonics.

The footprint of the newly studied Luna impact crater – named for its proximity to a village of the same name – is visible in this image, acquired by the OLI (Operational Land Imager) on the Landsat 8 satellite on February 24, 2024. It measures approximately 1 .8 kilometers (1.1 miles) wide and the outer rim rises about 6 meters (20 feet) above the crater floor.

The Luna Building is located in the Indian state of Gujarat, in a grassland called the Banni Plains. The Great Rann of Kutch, a vast white salt desert, lies just to the north. Parts of these low-lying areas are underwater for much of the year, and Luna Crater often contains water. Researchers took advantage of a dry period in May 2022 to collect samples from throughout the structure.

In the rocks and sediments, scientists have discovered several minerals that are unusual in Earth’s natural environment. These rare minerals are formed under the extremely high temperatures and pressures created when a meteorite hits the ground. The researchers also measured abnormally high concentrations of the rare element iridium, consistent with findings at other impact craters.

Based on radiocarbon dating of plant remains in the mud at the site, the team determined that the impact occurred about 6,900 years ago. The crater is located near the remains of an ancient Harappan settlement, but it is uncertain whether the impact predated the arrival of humans.

Impact craters appear throughout our solar system and can provide scientists with insight into atmospheric processes and the subsurface composition of planets and moons beyond our own. For example, a 2021 impact on Mars exposed a layer of water ice, which was imaged by the High-Resolution Imaging Science Experiment (HiRISE camera) aboard NASA’s Mars Reconnaissance Orbiter. This was the closest to the Martian equator where buried water ice had ever been found – an important discovery for potential human missions.

Scientists also used data from NASA’s Cassini mission to look at the evolution of impact craters on Titan, Saturn’s largest moon. Among other insights, they discovered the different ways weather shapes Titan’s surface depending on latitude.

Image from NASA Earth Observatory by Michala Garrison, using Landsat data from the US Geological Survey. Story by Lindsey Doermann.