Members of the US Congress are asking this question with an eye on the vast budget deficit and the politically sensitive squeeze on the nation's welfare spending. After all, why pay billions gazing into outer space when back on planet Earth there are children who need feeding and old ladies who require medical treatment? It sounds cheap to juxtapose the images, but these are the real choices faced by America's cash-strapped politicians.
It is easy to argue for funding scientific projects that generate commercial returns. The satellites that circle the earth have all kinds of pay-offs. Weather forecasting and monitoring the ozone level and global warming are all far easier thanks to those machines in the sky. The sugar beet industry even claims to save a fortune by using satellite pictures to check when the crop is ripe. And, of course, Rupert Murdoch uses them to send us round-the-clock coverage of some of the world's major sporting events.
Satellites, sugar and soccer aren't much help in justifying Jupiter expeditions. The often quoted proposition that investing in space travel gave us non- stick frying pans as a spin-off is factually incorrect. But it is also crazy economics. The billions of dollars spent on space travel could have been invested far more lucratively elsewhere. American scientists have even suggested that the cost of pouring all that brain power into space was to miss out on the emerging electronic technologies - and to cede the consumer electronics industry to Japan.
Of course, new improved consumer products aren't the only reason for investing in research. The scientific - if not economic - case for Galileo is overwhelming. We have the chance to discover the truth about that great whirling red spot on the planet's surface. And, if we are lucky, we may find some of the secrets of the universe lurking beneath Jupiter's clouds.
Where mysteries of the cosmos are at stake, scientists can draw on a wealth of public enthusiasm and support. After all, just think of all the films that have been made about space exploration. The success of Star Trek across the generations depended on "boldly going where no man has gone before". And the shelves of book shops are lined with accounts of the Big Bang and black holes. We are fascinated by the romance of the pursuit of pure knowledge and the beauty and secrets of the stars.
Not every space project will be worth the effort that goes into it. And the exact budget of the American space agency, Nasa, is a legitimate subject for regular critical debate. But the never-ending quest to discover new worlds and expand our understanding is a vital and worthwhile part of what makes us human. Space exploration must boldly go on.Reuse content