This fits some assumptions about the makeup of Mars, but it's helpful to have positive, quantitative proof, scientists say. Curiosity scooped up some sand from its current hangout at Rocknest, in the Glenelg region of Gale Crater, and sifted it through a sieve. Only particles smaller than the width of a human hair make it through the sieve and into Curiosity's belly, where the powerful Chemistry and Mineralogy instrument resides. CheMin uses X-ray diffraction, which is a standard geologic technique for identifying rocks. It was no small feat to bring this technology to Mars--scientists had to shrink a room-sized setup into something smaller than a standard microwave oven.