THE XPRIZE foundation, based near Los Angeles, exists to encourage innovations that might be useful but from which conventional financial backers are likely to shy away. Previous XPRIZES have been awarded for feats such as flying a reusable spacecraft to the edge of space, and designing cheap sensors to measure oceanic acidity. Those still on offer would, among other things, reward the mapping of Earth’s sea floor, and a way of extracting water from air using renewable energy for less than two cents a litre.
Another prize that is still up for grabs is for carbon capture and storage, a putative approach to stopping the rise of climate-changing greenhouse gases in the atmosphere. To claim a share of the $15m on offer, winners will have to turn carbon dioxide extracted from power-plant flues into something useful—and do so profitably. On April 9th the ten-strong shortlist of those attempting this feat was announced.