Obama aims to send humans to Mars by 2030

The US President also says he's getting scientists, engineers and students together this week to dream up ways to build on the progress and "find the next frontiers".

"We have set a clear goal vital to the next chapter of America's story in space: sending humans to Mars by the 2030s and returning them safely to Earth, with the ultimate ambition to one day remain there for an extended time," Obama wrote in an essay posted by CNN.

"I'm excited to announce that we are working with our commercial partners to build new habitats that can sustain and transport astronauts on long-duration missions in deep space," he added. 

A second element of Obama's plan involves encouraging commercial companies to use the International Space Station, which circles the planet in low-Earth orbit, about 250 miles (400 kilometers) high.

A recently installed docking adaptor will allow more companies to park their spaceships at the orbiting outpost, a global collaboration that includes the United States, Russia, Europe, Japan and Canada.

Once the ISS's mission ends in 2020, it could be used as a base to help set up other commercial space stations, said NASA administrator Charles Bolden.

The US space agency asked companies for input and "the private sector responded enthusiastically, and those responses indicated a strong desire by US companies to attach a commercial module to the ISS that could meet the needs of NASA as well as those of private entrepreneurs," said Bolden.  

Dr Scott Pace from George Washington University is one of the experts that think this goal is might not be achievable by the 2030s.

"It's possible to imagine putting astronauts in orbit around Mars and visiting Martian moons but technical challenges and the monetary challenge are daunting," he said.