Nuclear power and propulsion technologies such as those being developed under NASA's Project Prometheus will be essential to any future human mission to Mars, according to NASA's associate administrator for space science.

"I would maintain if you really are serious about sending humans to Mars and keeping them there for a while, you ... have to have this technology," NASA's Edward Weiler said June 3 in testimony before the Senate Commerce Committee's subcommittee on science, technology and space. "I just can't conceive of sending humans to Mars and depending on solar panels and fuel cells for power."

With current chemical propulsion systems, NASA can only launch spacecraft to Mars every 22 months, when the red planet's orbit brings it to within 34 million miles of Earth. With chemical propulsion, the trip time for a standard "coasting" trajectory to Mars during one of these opportunities is six to seven months, Weiler said.

After arriving at Mars, a crewed mission would then have to wait 18 months before it could return home, making nuclear power a very attractive resource, according to Weiler.

"If ... they have to stay on the surface for up to a year or 18 months until things align correctly to come back home, you need power on the surface," Weiler said. "And the best way to generate that power reliably would be with a nuclear reactor."