Rocks are phenomenal time keepers. Their composition, shape, and age can make an otherwise barren environment reveal its secrets.

On Mars, rocks are front and center in the ongoing quest to uncover the planet's history and find evidence of past life. Unfortunately, we haven’t been able to send men to Mars yet; men with their built-in geology kits: eyes, hammer-wielding hands, and clever brains. 

Instead, we send geology-capable surrogates in the form of rovers like Spirit and Opportunity. And in the case of these two rovers, their geologic instruments are also a tribute to the victims of the September 11 attacks on the World Trade Center.

Smashing a rock with a rover's arm is a little dicey and potentially very problematic. So the MER team behind Spirit and Opportunity (both of which landed on Mars in 2004) came up with an easier and safer way to see inside a rock: scrape away its weathered surface. Then individual instruments -- spectrometers to determine composition, magnets to collect magnetic dust particles, and a microscopic imager for high resolution photos -- could do the science. The tool for this first step, scraping into the rocks, was the rock abrasion tool or RAT.

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[Image: NASA]