The Martian Race — Gregory Benford

As NASA bogs down in politics, tycoon John Axelrod mounts a privately funded expedition to the Red Planet. Axelrod's not high-minded--he expects the televised flight to net him billions. But for astronaut-scientists Julie, Viktor, Marc, and Raoul, the mission's not about money. It's about discovery...and surviving for two years on a frigid, alien world that can kill them in countless ways. For a time will come when--in order to live--the explorers must embrace everything that makes them human...and everything that will make them Martian.