NASA’s moon orbiter is sending back shots of lunar curiosities that look even curiouser when you see them through 3-D glasses.

One of the most curious sights is the natural bridge you're looking at right here, near King Crater on the moon's far side. The two-dimensional view may look like nothing more than two black spots at the left edge of the frame — but through red-blue specs, it's clear that a wedge of sunlight is shining down to the bottom of the chasm below.

The bridge is about 20 meters (65 feet) across and roughly 8 meters (25 feet) wide. Based on interpretations of the slanting shadows, the depth of the chasm ranges from 6 to 12 meters (20 to 40 feet).

This is just one of several natural bridges spotted by NASA's Lunar Reconnaissance Orbiter during its survey of the moon. The team in charge of the Lunar Reconnaissance Orbiter Camera says in its image advisory that such features are formed when material from  the surface falls into an empty lava tube beneath. The case of King Crater is even more unusual in that the bridge is not formed out of volcanic basalt, but rather out of rock that was melted by an ancient impact.

Paul Spudis, a senior staff scientist at the Lunar and Planetary Institute, discusses the bridge's origins on his "Once and Future Moon" blog and notes that the formation is transitory, just as natural bridges on Earth are.

"Eventually, both surface grinding and shaking during impacts will cause the collapse of this feature," Spudis writes. "However, this won't happen anytime soon, so you have several tens of millions of years to see it."

We can see it on our computers in 3-D thanks to Nathanial Burton-Bradford, a British astronomy enthusiast who has created red-blue pictures of several lunar bridges as well as other sights, including a space shuttle launch. If you don't yet possess 3-D glasses, consult this NASA guide to purchasing spectacles or making your own. Party stores typically sell the specs as well, and I'll occasionally send out a batch myself. (Right now I'm fresh out ... but watch this space in case I get a new supply.)

David Imbaratto / Stellar Exploration for Planetary Society

Boulders on an otherwise smooth floor are seen on the Mare Tranquillitatis pit crater on the moon's surface in an image from NASA's Lunar Reconnaissance Orbiter. The pit opening is about 100 meters wide, leading to a cavity more than 100 meters deep.

The bridges of the moon merely highlight the fact that extraterrestrial geology can get pretty bizarre: We've already talked about the moon's deep, hollow pits — which could provide a haven for future settlers. Last week, the LROC team released stunningly sharp images of several pits, which were formed through a process similar to the one that created the natural bridges. In each case, surface material has collapsed to reveal a preserved lava tube below. The depths of these pits range from 34 meters (110 feet) to more than 100 meters (330 feet).

Red-Blue Planet ... and more
When you turn to Mars, the 3-D views can get even more bizarre. The website for the Mars Reconnaissance Orbiter's high-resolution camera offers more than 1,600 3-D images, including creepy craters, snaky valleys and fields of cratered cones. The European Space Agency's Mars Express, meanwhile, has sent back 3-D views of the "Face on Mars" and other Cydonian sights.

For a 2-D version of that crazy Martian cone field, check out the latest installment of Month in Space Pictures, a slideshow that features the past month's coolest imagery relating to outer space. Follow the links below for bigger versions of each picture featured in our September roundup, suitable for printing out or putting on your computer desktop:

• Martian sea of sand, as seen by Mars Reconnaissance Orbiter
• Dance of the galaxies, presented by the European Southern Observatory
• Crazy cones on Mars, from MRO (and mentioned above)
• Creating Curiosity, documented by JPL as well as the big picture from AP
• Igor the Terrible, seen from the International Space Station
• Dodging a bullet, from NASA's Solar Dynamics Observatory and from EPA
• Bull's-eye on the moon, from NASA's Lunar Reconnaissance Orbiter
• Two flashes from Jupiter, passed along by the Jet Propulsion Laboratory
• Spiral in space, spotted by the Hubble Space Telescope
• Bootprint on Mars, from Mars Express (and highlighted here last month)
• NASA's six-legged robot, from the Desert RATS team and Getty Images
• Practicing for Mars, also from the Desert RATS
• Ice sculptures in space, from the Hubble Space Telescope
• New York at night, sent down via Twitpic by NASA's Doug Wheelock
• Shooting a laser at the sky, from the European Southern Observatory
• Thar she blows, a view of a rocket motor test from NASA and ATK
• The road ahead, from JPL's Mars rover team
• Saturn and its children, from the Cassini imaging team
• Moon and Earthglow, from the International Space Station
• Twilight of the shuttle, captured by Reuters at Kennedy Space Center

... And hot off the press:

• Conjoined moons: Two of Saturn's moons, Dione and Rhea, appear to get it on in a Cassini image.
• Dark cocoons of starbirth: NASA's Spitzer Space Telescope captures a beautiful view of "coreshine."

Those last two pictures are sure to get some consideration for October's "Month in Space" roundup, so stay tuned. 

Join the Cosmic Log corps by signing up as my Facebook friend or hooking up on http://twitter.com/b0yle. And if you really want to be friendly, ask me about "The Case for Pluto."