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.

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.

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.