The largest piece of Mars ever found on Earth was sold for just over $5 million at an auction of rare geological and archaeological objects in New York on Wednesday. The 54-pound (25-kilogram) rock named NWA 16788 was discovered in the Sahara Desert in Niger by a meteorite hunter in November 2023, after having been blown off the surface of Mars by a massive asteroid strike and traveling 140 million miles (225 million kilometers) to Earth, according to Sotheby's. The estimated sale price before the auction was $2 million to $4 million. The identity of the buyer was not immediately disclosed. The final bid was $4.3 million. Adding various fees and costs, the official bid price was about $5.3 million. Two advance bids of $1.9 million and $2 million were submitted. The live bidding went slower than for many other objects that were sold, with the auctioneer trying to coax more offers and decreasing the $200,000 to $300,000 bid intervals to $100,000 after the proposals hit $4 million. The red, brown and gray meteorite is about 70% larger than the next largest piece of Mars found on Earth and represents nearly 7% of all the Martian material currently on this planet, Sotheby’s says. It measures nearly 15 inches by 11 inches by 6 inches (375 millimeters by 279 millimeters by 152 millimeters). It was also a rare find. There are only 400 Martian meteorites out of the more than 77,000 officially recognized meteorites found on Earth, the auction house says. “This Martian meteorite is the largest piece of Mars we have ever found by a long shot,” Cassandra Hatton, vice chairman for science and natural history at Sotheby’s, said in an interview before the auction. “So it’s more than double the size of what we previously thought was the largest piece of Mars.” It’s not clear exactly when the meteorite was blasted off the surface of Mars, but testing showed it probably happened in recent years, Sotheby's says. Hatton said a specialized lab examined a small piece of the red planet remnant and confirmed it was from Mars. It was compared with the distinct chemical composition of Martian meteorites discovered during the Viking space probe that landed on Mars in 1976, she said. The examination found that it is an “olivine-microgabbroic shergottite,” a type of Martian rock formed from the slow cooling of Martian magma. It has a course-grained texture and contains the minerals pyroxene and olivine, Sotheby’s says. It also has a glassy surface, likely due to the high heat that burned it when it fell through Earth’s atmosphere, Hatton said. “So that was their first clue that this wasn’t just some big rock on the ground,” she said. The meteorite previously was on exhibit at the Italian Space Agency in Rome. Sotheby’s did not disclose the owner. Wednesday’s auction was part of Sotheby’s Geek Week 2025 and featured 122 items, including other meteorites, fossils and gem-quality minerals.