Photo: Crossing paths on Mars

Without a guide, that dot would be easy to miss amidst the cracks, shadows and rocks scattered around the Martian surface. And even if you do spot it from this elevated vantage point, that unusually dark speck on the southeast rim of the Santa Maria Crater could be anything--a rock, a shadow, a photographic artifact left by the aggressive colorization process applied to the photo. But it's not a rock, or a digital glitch. It's a piece of man-made machinery.

That speck is none other than the Opportunity rover, which has been hobbling around the Martian surface since 2004. (For scale, that crater is about 90 meters wide.) For a few months now, the Opportunity has been surveying this site, analyzing nearby soil and returning stunning images like this one:

For a full-size version, click here.

But what about the other craft, the one behind the lens? That's the Mars Reconnaissance Orbiter, which celebrates its fifth year in orbit today, on March 10th. During the last half-decade, the orbiter has returned 131 terabits of data to Earth, mostly in the form of over 70,000 images like the one above. In more familiar terms, that's somewhere around 17,000 gigabytes.

Meetings like this are hardly unprecedented, given that the satellite completes another full Martian orbit every one and a half Earth days. But it's worth considering this brief encounter, which took place far, far beyond where any human has visited, as it strikes a resonant chord of wonder at a time when NASA's future--in particular, the continuation of interplanetary missions like the ones that led up to this stunning photograph--is, to put it lightly, highly uncertain.

Source images courtesy of NASA; photo composite by SmartPlanet; hat tip to MSNBC.

This post was originally published on Smartplanet.com