Some space experts have said that any manned Mars mission using existing rockets probably would need to have a capsule dock with some type of booster in orbit.

WSJ: First Space Tourist to Outline Trip to Mars

No manned Mars mission is currently planned, of course.

ECONOMIST: Planetary pretenders

Currently, Nasa has small-scale studies but no plans for a manned mission to Mars.

BBC: Manned flight to Mars in 2014?

The scheme has also attracted interest as a possible long-term power source for a manned mission to Mars.

ECONOMIST: Nuclear power

At the same time we are trying to solve climate change, police the world and send a manned mission to Mars.

FORBES: Should We Starve the Beast?

We have the technology and ability to exploit the resources found on the moon and in the asteroid belt as well as sending a manned mission to Mars to set up a permanent base.

FORBES: Who Says America Is Falling Behind In The Space Race?

Many sceptics will undoubtedly question why any country would choose to invest in future space exploration, including a manned mission to Mars, while there are so many unsolved problems on our planet, from HIV to malaria to poverty.

BBC: Viewpoint: Should we send humans to Mars?

In 2010, when Mr Obama outlined his ideas, he spoke, somewhat vaguely, of a manned trip to a near-Earth asteroid, to be followed at some unspecified date in the 2030s by the ultimate space-cadet dream a manned mission to Mars.

ECONOMIST: The space shuttle

With respect to a manned, one-way mission to Mars, I suspect such questions will fall on deaf ears.

WSJ: Mars One and the Scientific Embrace of Suffering

And, for those space-cadets who still dream of a manned mission to the planet, there is also the Mars radiation environment experiment.

ECONOMIST: Mars Odyssey