The Evolution of Surface Preparation Tools for in Situ Science on Mars

Surface Preparation, or the act of removing the outside layer of a rock target, has been a scientific enabling engineering function of every Mars Rover from Spirit and Opportunity through the latest Perseverance Mars mission. Rock surfaces exposed to the harsh Martian environment can be covered in dust, and fundamentally changed in chemical composition due to exposure to weather and radiation. Surface preparation tools function to expose fresh layers of rock that are superior in providing an understanding of the processes in which they were formed, mineralogy, elemental chemistry, and exposing signs of organic chemistry. This paper describes the evolution of the robotic hardware and software designed, built, and flown in the series of NASA-led Martian rover missions beginning with the Rock Abrasion Tool (RAT) on the Spirit/Opportunity rovers to the Dust Removal Tool (DRT) on Curiosity to the Corer & Gas Dust Removal Tool (gDRT) on the Perseverance Rover. The hardware design, concept of operation, and capabilities of each design are described herein. The driving requirements that shaped the hardware, and proved challenging to satisfy, are also detailed. Increasingly stringent performance requirements on each mission led to the progression of the hardware and software as well as new novel solutions to overcome performance challenges experienced on previous iterations. On the latest Perseverance Rover, this included a compressed gas system to clear dust tailings in lieu of brushes flown on previous missions, as well as an adaptive software algorithm that adjusts drill spindle speed, percussive energy, and surface pressure based on real-time sensor information to improve target surface smoothness and abrading bit wear characteristics. Selected Mars rock target results from each design iteration are provided. These images of previous Martian rock targets provide the best context to describe improvements in both our abrading capabilities and in our ability to clear tailings and dust from our abraded targets. The successes and shortcomings are discussed in relation to meeting the science community's goals for interrogation of the abraded surface targets.