At the same time, the European Space Agency is building another part of the spacecraft: a "service module" that will provide thrust as well as holding oxygen and water for astronauts on deep space missions.
A new space launch system is also being built which will be more powerful and more sophisticated than the Saturn V rockets which boosted the Apollo moon missions 40 years ago.
Two versions of this rocket are planned: one capable of carrying a 77-ton payload and a larger version that can carry 144 tons.
One scenario has the now-ageing International Space Station being used as a "staging platform" for deep space missions, so it must be kept in good working order; fortunately, US funding was this week confirmed to keep the ISS operational until at least 2024.
Of course, money for space exploration is cyclical, generally dependent on who is in power, but with all components now being built or tested Nasa's Mars programme appears to be locked in " or as definite as the vagaries of politics allow.
The case for continued backing is partly aided by the fact private companies are now joining the space race, notably the Mars One programme which aims to send several "lucky" people on a one-way trip to Mars by 2022.
Although the odds are against this venture succeeding, doubtless governments are quietly mortified at the idea a commercial outfit might beat them to the prize, thus helping guarantee their own commitment.
Whether Mars, with its freezing temperatures, thin atmosphere, and no magnetic field will prove to be at all hospitable for human habitation is moot.
But in the journey to explore the solar system, it's a useful and publicly-alluring way-station.
The real prizes are further out. There is immense wealth in the asteroid belt, in the Jovian and Saturnian systems, and ultimately in the Kuiper Belt beyond Neptune, where perhaps 100,000 ore-rich bodies wait to be harvested by anyone able to meet that challenge.
Potentially, the resources available to be mined among the outer planets could meet the demands of Earth's population for hundreds if not thousands of years; ample reason to expect big business will, in the reasonably near future as our own resources become scarce, start to look outward with serious intent.
Of course in order for technology to save us by making space liveable and economically beneficial, we first have to maintain civilisation on Earth. Right now it's a line call whether Planet B is to be, or not.
And for a fascinating look at how the solar system actually travels through space, see www.djsadhu.com/the-helical-model-vortex-solar-system-animation/
Bruce Bisset is a freelance writer and poet.
