Google's Lunar X Prize requires teams to put a robot on the moon, have it travel at least 500 meters across the lunar surface, and send high-definition photos back to Earth. There are 17 teams competing for the $30 million jackpot.

The Lunatrex team's approach involves having a rocket build up speed while orbiting the Earth, before finally shooting off towards the Moon. The slow approach means you'd have weeks, not minutes, to make course corrections. Lunatrex is using an electric engine that shoots out a stream of charged particles to accelerate slowly, which has already worked well in probes like Deep Space 1 and the Dawn probe.

Lunatrex's lunar robot designs are also unconventional: one is an earthworm-shaped bot that would use piezoelectric "muscles" to scoot across the lunar surface. Another isocahedron-shaped robot would have 12 legs that could move in any direction — and the legs could double as transceiver antennae. Lunatrex is a consortium of aerospace companies, plus the University of Dayton, OH.

It's exciting to see somebody putting money and thought into coming up with innovative methods of traveling into space, some of which will hopefully benefit space exploration for decades to come. At the same time, it's a little worrisome to see Google's millions going into a contest to encourage entrepreneurs to litter our orbit with even more masses of space junk from the various failed attempts to snag the prize. Future space probes will have to have extra-dextrous steering mechanisms to avoid the debris of today's whiz-bang lunar vehicles. [Space.com]

Here you can see an even more haunting photo, of a family in Texas who discovered a smoking chunk of the space shuttle Columbia in their front yard.

Here's a farmer in Queensland, Australia, who found this unidentified hunk of metal on his property last year. Though nobody is quiet sure where the junk came from, it's possible that it's from a rocket used to launch a communications satellite.

No one is really sure where this rock of metal alloy came from either, though it most certainly is not from nature. It crashed into a New Jersey home in 2007.

As space junk crashing to Earth becomes more and more common, I can't help but wonder who will be liable for damages it causes. If a chunk of a satellite or rocket crushes your car or injures you, who is responsible? The creator of the space vehicle? The launch facility? Somebody has to pay those damages.

See more amazing images of space junk that's fallen to Earth, or remains precariously wobbling through orbit, in the UK Guardian.

All photos via Reuters except mystery blob of New Jersey via Mike Derer/AP

It isn't possible to repair satellites in high orbit by remote control, because the radio lag is too great. With the damaged satellite hurtling through space, the operator couldn't react quickly enough to accomplish anything. The Autonomous Space Servicing Vehicle (ASSV - yes, they actually use this acronym) gets around this by sending robots up to do the tricky job of collecting the satellite. They load it into a repair bay. There, the static satellite can be successfully fixed via telerobotics.

That last bit is actually a little disappointing, because I was initially picturing hundreds of satellites steadily orbiting Earth, doing their jobs as a sturdy team of robots keeps them fully functional centuries after humanity has breathed its last gasp. What lonely radio signals would they continue to bounce back and forth as they keep watch over the empty world beneath them?

But in truth, humans will be needed to keep things running. While it's not as poetic, it could save telecom companies and world governments enormous amounts of money. Image by: NASA.

New robotic repair system will fix ailing satellites. [Queen's University]