The Rock Abrasion Tool (RAT) is a grinding and brushing installation on NASA’s twin Mars Exploration Rovers, Spirit (MER-A) and Opportunity (MER-B), which landed on Mars in January 2004. It was designed, developed and continues to be operated by Honeybee Robotics LTD, a developer of specialized robots, automated technologies and related systems. The RAT was first used by Spirit on its 34th sol (6 Feb 2004). It was held up to the rock Adirondack, whereby it scraped to a depth of 2.85 mm over the course of 3 hours. Since then it has been used on numerous Martian rocks by both MER rovers.