N EW YORK CITY — Tucked away in a building on the corner of 72nd Street and York Avenue in Lenox Hill, an extraterrestrial marvel sits sturdily on a white pedestal. It's the largest Mars rock on planet Earth — and it turns out its 54-pound (25-kilogram), ashy terracotta structure isn't as priceless as you'd expect.

A chunk of the Martian surface that made an unlikely voyage to Earth will be available to the highest bidder at Sotheby's auction in New York.

The red, brown and gray hunk 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.