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A meteorite that is the largest known piece of Mars on Earth is expected to fetch up to $4 million when it goes up for auction later this month.

Known as NWA 16788, the meteorite weighs 54 pounds (24.5 kilograms), massive compared with most Martian meteorites, which tend to be small fragments, auction house Sotheby’s said in a statement published Tuesday.

Meteorites are what’s left when a comet, asteroid or a meteoroid survives its passage through the earth’s atmosphere.

Discovered in November 2023 in the remote Agadez region of Niger, NWA 16788 is a “monumental specimen” that is around 70% larger than the next biggest piece of Mars ever found on Earth, according to Sotheby’s.