And more than once, the Mars machinery has sent back an image that stirred up a promising eureka moment: Finding evidence for life on that remote world.
A case in point, during a recent run of Spirit in the Columbia Hills, the robot used its arm-mounted devices to poke and probe a select Mars rock. One piece of hardware -- the Rock Abrasion Tool, known better as the RAT -- is on hand to expose fresh martian rock.
The RAT utilizes a single diamond matrix wheel to scrape the rock surface. It does this ever so slightly and progressively to achieve a wanted depth. The abraded surface is actively swept clean by a brush to prepare it for scientific examinations.
Once the rock was worked over, Spirit's Microscopic Imager went in for close-up looks at the results.
And within the images, an odd feature could be seen, seemingly a pattern of something more biological than just rock.
"The first impression I got -- based on the morphology alone -- was how similar it looked to a common terrestrial foliose lichen," said Barry DiGregorio, a research associate for the Cardiff Centre for Astrobiology in the United Kingdom. "On Mars, however, as we all have learned from past experience, looks can be deceiving," he told SPACE.com.
DiGregorio said he was struck by the fact that the entire rock outcrop on which this feature is found looks in places like it has a moss-like texture to it. "In the absence of any spectroscopic data, it's difficult to say for certain what it is. The radial pattern may turn out to be similar to spherical dendritic iron oxides," he added.
Indeed, looks can be deceiving, concurs Stephen Gorevan, payload lead for the RAT on the Mars Exploration Rover project. He's also chairman of Honeybee Robotics...