A meteorite thought to be the largest piece of Mars on Earth changed hands for a reported $4.3 million at an auction at Sotheby’s in New York on Wednesday. The rock, known as NWA 16788, weighs 24.5 kilograms – a huge weight by the standards of meteorites from Mars, which are usually tiny fragments, Sotheby’s said.

The meteorite was discovered in November 2023 in the remote Agadez region of Niger. In total, it is estimated that only 400 meteorites of Martian origin have been identified on our planet.

Cassandra Hutton, vice president of science and natural history at Sotheby’s, said NWA 16788 is a “discovery of extraordinary significance” and is the most valuable Martian meteorite ever auctioned. “Its immense size, its distinctive red color and its journey through time and space make it a unique find of a generation,” he stressed, adding that the meteorite offers a tangible connection to the Red Planet that has always captured people’s imagination.

Analyses of its internal composition indicate that it probably broke away from the surface of Mars after a powerful asteroid impact that caused part of it to melt into a glassy form. The characteristic shiny crust on its surface formed as it passed through the Earth’s atmosphere.

However, the auctioning of NWA 16788 instead of donating it to scientific institutions has caused controversy. “It would be a shame for it to be lost in some oligarch’s vault. It belongs in a museum, for scientists to study it and for children and families to enjoy,” said Stiv Broussate, professor of palaeontology and evolution at the University of Edinburgh.

On the other hand, scientist Julia Cartworth from the University of Leicester pointed out that the buying and selling of meteorites is a key incentive to discover new specimens, which feeds scientific research.

She noted that a reference sample from this meteorite is kept at the Purple Mountain Observatory in China and estimated that, although the new owner remains anonymous, the scientific community may continue to benefit from its study.

This is not the first time a meteorite from Mars has gone under the hammer. In February 2021, a sample containing atmosphere from the planet was sold by Christie’s for $200,000 – a price much higher than the original estimate of $30,000 to $50,000.