Facelifts can sag. Botox is temporary. But modern science has a new way to return youth to weathered faces: the rock abrasion tool (RAT). If your dermatologist hasn’t heard of it, ask your local Mars scientist. Billions of years of exposure to the sun, atmosphere and extremely fine Martian dust has given Mars rocks a weathered “rind,” or exterior layer. The RAT, part of the science-instrument package carried by the two Mars rovers, Spirit and Opportunity, uses a diamond-tipped robotic grinding tool to scrape away this weathered exterior, revealing a fresh surface.