You see, while Opportunity continues to function nominally after nearly six years on planet, its companion Spirit, on the opposite side of the planet, is really showing signs of age.

As we all know, Spirit has been stuck in deep Martian sand for some time now. That hasn't changed. What has changed is the rover's memory. It's going. NASA scientists are calling the issue "amnesia," and it isn't the first time this phenomenon has affected the rover.

Basically, what happens during an amnesia event is the rover fails to record any observations—scientific or otherwise—in its flash memory during power down time at night. Worse still, the cause is unknown. My uneducated guess is a Martian is playing with a magnet. Update: Fine. Magnets don't affect flash. I get it. It's now a ray gun.

The events are a nuisance for now, but could become crippling if they start happening more often. It's troubling, yes, but we must remind ourselves these rovers were built for 90-day missions. Spirit is currently going on five years, nine months. Even so, get well soon. [MSNBC]

Designed by Dan Roe as a "kinetic art" project, the Trilobot seems perfectly content to just kinda roll around, climbing over some obstacles and bouncing off the rest. For how simple it is, though, it's surprisingly nimble: it can wiggle through some pretty gnarly rock gardens with its swiveling legs. And as far as things with wheels go, it's kind of adorable. [Engadget]

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To celebrate the anniversary, NASA assembled a short video that profiles several of the JPL engineers who've pretty much dedicated their lives to operating and maintaining the rovers, as well as some pics of the rovers themselves in action.

And while the rovers have experienced their share of mishaps and sun-blocking dust storms over the past five years, even the worst of times have provided amazing opportunities for discovery.

Case in point: Ashley Stroupe, rover driver for NASA's JPL, said that a malfunctioning, dragging right front wheel on Spirit actually led to the discovery of silica and sulfur just below the Martian surface. Those minerals that had to be put there by water, she said, which meant the wheel-dragging incident was actually a "major scientific discovery."

So congratulations again to the two venerable rovers that are still plugging away on Mars after five years of service. Here's to five more? I only ask because, after the Mars Science Laboratory delay to 2011, it looks like its going to be a while before NASA can get them some company. [BBC]

Says NASA, via its Jet Propulsion Laboratory web page:

If Mars had an on-line Web site for ads, one of them might say something like this: "Wanted: Gentle space-age dust removal system to clean solar cells without leaving grit behind. Please direct inquiries to NASA."

NASA's Spirit rover has accumulated a lot of dust during four years of exploring Mars, especially following last year's dust storms. Only about one-third of incoming sunlight is able to penetrate dust on the rover's solar panels to be converted to electricity. As a result, Spirit is experiencing the lowest energy levels to date and accumulating a backlog of data waiting to be transmitted to Earth. The only available cleaning agent would be a timely gust of Martian wind!