WASHINGTON -- Setting foot on Mars by the 2030s is human destiny and a US priority, and every dollar available must be spent on bridging gaps in knowledge on how to get there, NASA's chief said Monday.

Addressing a conference of space experts at George Washington University, NASA administrator Charles Bolden said that despite hard economic times the United States is committed to breaking new boundaries in space exploration.

"A human mission to Mars is today the ultimate destination in our solar system for humanity, and it is a priority for NASA. Our entire exploration program is aligned to support this goal," Bolden said.

President Barack Obama has proposed a $17.7 billion dollar budget for NASA in 2014, and he supports a "vibrant and coordinated strategy for Mars exploration," Bolden said.

Among the first steps to sending astronauts to Mars are NASA's plans to capture and relocate an asteroid by 2025, a process that should inform future efforts to send humans into deep space, the former astronaut said.

Also, US astronaut Scott Kelly and Russian cosmonaut Mikhail Kornienko have volunteered to spend one year at the International Space Station beginning in 2015 to allow doctors to assess how long-duration zero gravity exposure affects bone density, muscle mass and vision.

Currently, a rotating cast of global astronauts each spend a maximum of six months aboard the orbiting outpost.

But despite increasing interest in landing on Mars, and a newly diverse space race that involves many more countries than old Cold War foes the United States and Russia, there is plenty that experts do not know about how to reach Mars.

For instance, there is no existing space vehicle to carry people on the seven-month or longer journey there, not to mention no plan for returning people to Earth.

Medical experts are unsure what the physical ramifications would be for people who attempt to travel in high-radiation environments for such extended periods.

And just how people would survive, breathe, eat and drink on the dry, red planet are significant obstacles that have yet to be overcome.