The US space agency Nasa has announced the ultimate smash-and-grab raid: the first attempt to collect a handful of asteroid rock and bring it back to Earth. There are three reasons why astronomers and space buffs should cheer the seven-year, $800m robot mission and one reason why they should sob.

Asteroids and comets are the rubble left over from the making of the solar system: this pristine stardust, unchanged for 4.5bn years, is of immense scientific interest. Asteroids and comets are packed with an astonishing array of organic chemicals, including amino acids, the building blocks of proteins: there is an enduring suspicion that they may have played a role in triggering life on Earth. And the target asteroid, 1999 RQ36, is an enormous lump of rock that crosses the Earth's orbit and could in theory smash into us, with calamitous consequences – it would help to know more about it, in case evasive action is necessary. But the Osiris-Rex mission (the acronym stands for Origins-Spectral Interpretation-Resource Identification-Security-Regolith Explorer) is also a wistful reminder of abandoned dreams.

Four decades ago, the Star Trek and Avatar future seemed not just possible, but almost inevitable. Science had embarked on a course lit by science fiction – the space odyssey would continue. By 2001, the visionaries promised, there would be human settlements on the moon and Mars. And in high orbit around Earth, or balanced at points in space where solar and terrestrial gravity were equal, there would be artificial housing estates, orbiting homes to 10,000 people, and industrial centres: the conversion of captive asteroids into wealth on an astronomical scale.

Space scientists calculated that a nickel-iron asteroid of one cubic kilometre would contain 7bn tons of iron, 1bn tons of nickel and enough cobalt to supply the planet for thousands of years. Carbon-rich asteroids would be sources of water, butane, ethane, methane and other organic chemicals that would keep space colonies in food, fertilisers, building materials and even booze, while the citizens exploited solar energy in its most direct form. Space was the high frontier, and in the euphoria generated by the moon landings, prophets like Arthur C Clarke and Gerard K O'Neill were perceived not as daydreamers but as the new realists.

In the next 40 years, commercial investment in space grew exponentially, but only to make fortunes on Earth. There have been 10 missions to fly by, photograph and even touch these maverick lumps of celestial debris. But Osiris-Rex will be the first to pick up a whole pocketful of stardust, and bring it back for assay. A small step, but it keeps an old dream alive.