The rock, known as NWA 16788, will be sold by Sotheby’s New York this Wednesday as part of its natural history sale.

According to the auction house, the meteorite was blasted from the Martian surface by an asteroid strike before travelling 225 million kilometres to Earth. It was discovered by a meteorite hunter in the Sahara desert in Niger in November 2023. At nearly 15 inches long, the reddish-brown rock is 70% larger than the next biggest Martian fragment and accounts for almost 7% of all known Martian material on our planet, AP News reports.

“This Martian meteorite is the largest piece of Mars we have ever found by a long shot,” said Cassandra Hatton, a vice chairman at Sotheby’s.

Of the 77,000 officially recognised meteorites on Earth, only 400 are confirmed to be from Mars. A sample of this piece was sent to a specialised lab, which confirmed its origin by comparing its distinct chemical composition to data from the 1976 Viking Mars lander. Scientists identified it as an “olivine-microgabbroic shergottite”, a type of rock formed from slowly cooled Martian magma. Its glassy surface was likely created by the intense heat of entering Earth’s atmosphere.

The sale, part of Sotheby’s “Geek Week 2025”, also features a juvenile Ceratosaurus skeleton. Discovered in Wyoming in 1996, the near-complete fossil is almost 11 feet long and dates back 150 million years. It is estimated to sell for $4 million to $6 million.