An "unbelievably rare" piece of Mars - the largest ever found on Earth - has sold for $4.3m (£3.2m) at a New York auction on Wednesday.

The meteorite known as NWA 16788 weighs 54lb (24.5kg) and is nearly 15in (38.1cm) long, according to Sotheby's.

It was discovered in a remote region of Niger in November 2023 and is 70% larger than the next biggest piece of Mars that has been recovered, the auction house said.

Meteorites are the remains of rock left after an asteroid or comet passes through Earth's atmosphere.

Sotheby's auction house described the meteorite, a reddish brown rock, as "unbelievably rare". Only about 400 Martian meteorites have ever been found on Earth.

"This is the largest piece of Mars on planet Earth. The odds of this getting from there to here are astronomically small," Cassandra Hatton, vice-chairman of science and natural history at Sotheby's, said in a video posted online.

"Remember that approximately 70% of Earth's surface is covered in water. So we're incredibly lucky that this landed on dry land instead of the middle of the ocean where we could actually find it."

It remains unclear where the meteorite will end up as information about the sale will remain private.

Additional taxes and fees brought the total price of the rock up to about $5.3m, Sotheby's said.

At the Wednesday auction, which featured more than 100 items, a Ceratosaurus skeleton from the late Jurassic period sold for $26m and the skull of a Pachycephalosaurus sold for $1.4m.