The X Prize Foundation has announced a competition to build an environmentally friendly car. Nature reports that the winning vehicle will have to achieve at least 100 miles per gallon, regardless of the type of fuel it uses. Its carbon emissions have to be no more than 210 grams of carbon per mile. And it has to be cheap enough to expect sales of 10,000 a year.
That'll be a huge improvement on today's US average of about 21 miles per gallon. The prize's challenge lies more in manufacturing and economics than in developing radical new technologies. To achieve 100 miles per gallon can be done with existing technology, but requiring a radical redesign.
The rules are currently in draft form, and are open to public comment for 60 days beginning 2 April. The prize's value has not yet been announced, but will likely be more than $10 million. The previous two X Prizes, for spaceflight and genomics, each had a value of $10 million. --Julia Whitty