NASA announced new details yesterday about its plans for a Moon base that included a pair of small, pressurized rovers with a range of nearly 600 miles.

The space agency plans to return astronauts to the Moon around 2020. Agency officials first described proposals last December for a polar lunar base powered by near constant sunlight on solar panels.

Earlier proposals to carry small habitation modules to the Moon in stages might be supplanted by a proposal that would heave a single large module to the Moon on an unmanned cargo ship, Doug Cooke, the NASA official leading the lunar study group, said.

The new rover would not be much larger than the buggies the Apollo astronauts drove, but would be pressurized so that astronauts could drive in shirt sleeves and be protected from radiation  probably by a layer of water in the rover’s body, said Geoff Yoder, an official working on the lunar plans. To explore on foot, astronauts would put on spacesuits and leave the vehicle, Mr. Yoder said. The cost? “More than a Ferrari,” he joked.