by Paul Jay, CBC News online

In the spirit of DARPA's Grand Challenge robot road race, NASA sponsored a contest on Saturday inviting teams to build a machine capable of digging mock moon dirt.

And like the first year of the road race, none of the four teams were up to the mammoth task.

It's hard to blame the engineers. The 2007 Regolith Excavation Challenge asked teams to build autonomous robots capable of digging 150 kilograms of regolith from a giant sandbox in half an hour. As the Associated Press reports, an excavator built by Technology Ranch of Pismo Beach did the best, collecting just 65 kg in half an hour, while the other three machines broke down while digging.

As no one claimed the $250,000 US prize, the top honour in next year's competition will be worth $750,000.

History suggests someone will finish the competition next year. While none of the competitors won DARPA's off-road robot race in 2004, four teams finished on time and five teams completed the course in 2005.