Four billion years ago, Mars may have looked completely different. Water could have flowed across the planet's surface. There might have been life. To support these conditions, the planet's atmosphere must have been very different.
A NASA mission to investigate that atmosphere – and why it changed – is about to enter orbit around the Red Planet. Led by scientists at the University of Colorado Boulder, the mission, called MAVEN (short for Mars Atmosphere and Volatile EvolutioN), consists of a satellite that will orbit the planet.
NASA is hoping to soon venture out farther into space than ever before. But these long journeys mean astronauts could face greater risks to their physical and mental health than the space agency currently allows.
Now, an independent group of experts convened by the Institute of Medicine, the health arm of the National Academy of Sciences, has weighed in on how NASA should make decisions about the kinds of risks that are acceptable for missions that venture outside low Earth orbit or extend beyond 30 days.