He also says the water that was once on Mars would have been safe enough to drink.

“We have found a habitable environment that is so benign and supportive of life that probably if this water was around and you had been on the planet, you would have been able to drink it.”

It is important not to overstate the discovery. As the Associated Press noted, “despite the excitement over achieving one of the mission’s main goals, it has yet to find complex organic molecules considered the chemical building blocks of life.”

The six-wheeled, nuclear-powered Curiosity has been exploring within a deep, 150-kilometer-wide area called Gale Crater. Now, it will move to a place called Mount Sharp.

The project is expected to last two years and cost $2.5 billion. Curiosity is not designed to look for microbes that may be alive on Mars today or inspect remains of life forms that no longer exist.

Curiosity is the first Mars rover, but not the only one. The American space agency says it plans to send another rover, called Opportunity, to the red planet in 2020. Opportunity would be part of NASA’s plan to explore the Martian surface and atmosphere. The agency hopes to send humans to Mars in about 20 years.

NASA has announced plans for other projects between now and 2020. They include an orbiter to study the Martian atmosphere and a probe that would take a first look at what lies under the planet’s surface.