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.

Earth's Martian material goes up for auction at a prestigious auction house this week. The estimate? $2-4 million in Earth money.