New York: Sotheby’s will auction the largest known piece of Mars ever found on Earth, a 54-pound (25-kilogram) Martian meteorite called NWA 16788, in New York on Wednesday as part of its Geek Week 2025 natural history auction.

Estimated to fetch between $2 million and $4 million, the meteorite is believed to have been blasted off Mars by a massive asteroid impact and landed in the Sahara Desert, where it was discovered by a meteorite hunter in Niger in November 2023.

Measuring nearly 15 x 11 x 6 inches, the red, brown and grey rock is around 70% larger than the second-biggest Martian meteorite ever found and represents nearly 7% of all Martian material discovered on Earth. It has been verified by comparing its chemical fingerprint to that collected by NASA’s Viking probe on Mars in 1976.

“This Martian meteorite is the largest piece of Mars we have ever found by a long shot,” said Cassandra Hatton, vice chairman for science and natural history at Sotheby’s. “It’s more than double the size of what we previously thought was the largest.”

The rock’s surface displays glassy traces of the intense heat from its fiery entry through Earth’s atmosphere. Classified as an olivine-microgabbroic shergottite, it is a rare form of Martian magma containing pyroxene and olivine crystals.

The sale will also include 121 other natural history items, such as a juvenile Ceratosaurus nasicornis skeleton, which stands over 6 feet tall and nearly 11 feet long.

With just 400 confirmed Martian meteorites among the more than 77,000 officially recognised meteorites on Earth, the NWA 16788 is expected to attract interest from collectors, museums, and space science institutions around the world.