Not all missions are successful, and such was the case for last weekend's $1.5 million Sample Return Robot Challenge, backed by NASA and presented at Worcester Polytechnic Institute in Massachusetts. The robo-showdown was supposed to pit autonomous rovers against each other in a race to roll around a course, collect samples and return them back to base, using the sorts of technologies that would be available to interplanetary robots. That means no GPS, no compass, no Internet.

Eleven teams registered for the competition, and six showed up in Worcester — but none of the teams could collect a sample during an official run. "Hopefully, all the teams will continue to improve their robotic systems and return to participate in future NASA Centennial Challenges," NASA Chief Technologist Mason Peck said in a press-release postmortem.

Other challenges:

• Moon-dirt diggers win $750,000
• Electric plane wins $1.35 million
• Space elevator team wins $900,000
• Rocketeers win $1.65 million
• Engineer wins top prize in space glove contest
• NASA offers $5 million for new feats

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.