Anyone with the cinema habit knows that outer space is jammed with objects that threaten to collide with the Earth and extinguish human life. But whether it is worth doing anything about the threat is not so simple, as a government report has just analysed.
Near-Earth objects come in all shapes and sizes, from the sort that saw off the dinosaurs all the way down to the fine dust responsible for meteor showers. One problem is a vast population of objects that would not wipe out humankind on impact, but are capable of devastating a city and are too small for practical detection. One hit remote Siberia in the 20th century. There are some near-Earth object orbits that could mean there is little or no notice of even a major impact.
But the Department of Trade and Industry team is right to say that more resources should be devoted to mapping near-Earth objects, not least because their study is of scientific merit as well as having possible survival value. The objects are, after all, leftovers from the earliest days of the solar system.
The recent landing of Nasa's Near probe on the asteroid Eros reminds us that we still have much to learn from such objects. A thorough mapping of their distribution is part of this process. It would also inform a future decision about developing the technology to fight the threat.