After the space shuttle Columbia burned up during re-entry into Earth's atmosphere in 2003, the board that was convened to investigate the disaster looked beyond its technical causes to NASA's organizational malaise. For decades, the board pointed out, the shuttle programme had been trying to do too much with too little money. NASA desperately needed a clearer vision and a better-defined mission for human space flight.

The next year, then-President George W. Bush attempted to supply that vision with a new long-term goal: first send astronauts to build a base on the Moon, then send them to Mars. This idea immediately set off a debate that is still continuing, in which sceptics ask whether there is any point in returning to the Moon nearly half a century after the first landings. Why not go to Mars directly, or visit near-Earth asteroids, or send people to service telescopes in the deep space beyond Earth?

Yet that debate is both counter-productive — a new set of rockets could go to all of these places — and moot, because Bush's vision never attracted the hoped-for budget increases. Indeed, a blue-riband commission reporting to US President Barack Obama this week (see page 153) finds the organizational malaise unchanged: NASA is still doing too much with too little. Without more money, the agency won't be sending people anywhere beyond the International Space Station, which resides in low Earth orbit only 350 kilometres up. And even the ability to do that is in question: Ares I, the US rocket that would return astronauts to the station, is potentially on the chopping block.

NASA critics can rightly point out that the benefits of human space flight are fuzzy, especially when it comes to the science. The returns are occasionally bountiful, as with the astronauts' recent repair of the Hubble Space Telescope. But for the most part they are incidental and hugely expensive.

NASA-funded space scientists might be excused for feeling a bit smug. Their robotic science missions to Mars and elsewhere are orders of magnitude more cost-effective. And their budgets remain relatively protected from the turmoil engulfing the debate on human space flight — as they should be. Indeed, Obama's budget proposals bolster NASA's Earth-observation programme, where some of the most pressing knowledge is to be gained.

Like it or not, however, scientists do have a stake in the human space-flight debate. The rockets and the technology developed to take astronauts beyond Earth orbit could also make it possible to mount much more ambitious robotic missions. And perhaps even more important, the sight of humans travelling beyond Earth has an undeniable power to inspire future generations of space scientists (see Nature 460, 314–315; 2009). This link should not be surprising: both endeavours are animated by the same spirit of exploration.

True, sending astronauts beyond low Earth orbit is never going to be cheap. But adequately funding the 2004 exploration vision would not require money on the scale of the Manhattan Project, or even the Apollo programme. A boost of a few billion dollars a year — perhaps 15% of NASA's $17.6-billion total budget — would allow the agency to pursue a long-term programme of heavy-lift rockets that could go to the Moon, or other deep-space locales.

If Obama is not willing to support such a plan, then he and the American public should stop pretending that they are in favour of human space exploration. Because maintaining the space station is not exploration. It is a commute.