Robotic Exploration

Let's say scientists on Earth have chosen a rock and gotten the rover near enough to it to reach it with the rover's arm. This Cornell News article (December 19, 2003) describes what happens next:

Billions of years of exposure to the Sun, atmosphere and extremely fine Martian dust has given Mars rocks a weathered "rind," or exterior layer. The RAT, part of the science-instrument package carried by the two Mars rovers, Spirit and Opportunity, uses a diamond-tipped robotic grinding tool to scrape away this weathered exterior, revealing a fresh surface.

Access to the pristine rock interior is critical to understanding the history of the geology of Mars and to answering what Bartlett describes as the "big questions" to be solved by the rovers: Did water -- or even an environment suitable for life -- once exist on the red planet?

Photo courtesy NASA

These big questions might be answered by a very small machine: The RAT weighs only 1.5 pounds (0.68 kg) and uses less power (only 30 watts) than most light bulbs. It is about the size of a soda can.

The RAT occupies the turret, or "hand," of the rover's robotic arm, along with other science instruments for rock analysis, a microscopic imager, and Mössbauer and alpha-particle X-ray spectrometers. The agile arm, which has shoulder, elbow and wrist joints just like a human arm, presses the RAT up against a rock's surface.

In just two hours, the RAT's grinding wheel can shave off a disc about twice the diameter and thickness of a nickel from a hard rock surface. Two brushes sweep the resulting dust away from the hole to provide a clean surface for an up-close view.

Once the fresh surface is exposed, the imager and the spectrometers take over, peering through the abraded opening to perform a detailed analysis of the rock's interior. In order for scientists to learn about the processes that might have weathered the rock, the rover also records temperature and current readings from the RAT's three motors while they grind away the exterior layer.