Share The twin Viking spacecraft landed on Mars in 1976. They were cleaned to a level required to explore habitable regions. NASA NASA planetary protection officer suggests loosening limits on exploring Mars for life By Paul VoosenFeb. 22, 2018 , 5:25 PM Is there life on the surface of Mars? The clock is ticking on scientists’ window to solve that long-standing question before astronauts—and the microbes that live on them—contaminate the planet. Today, at a meeting in Washington, D.C., of NASA’s planetary science advisory committee, the agency’s new planetary protection officer raised the possibility of opening up a few of...