Surface Sampling and Science (SSS) – what is it?

From its inception, the Mars Science Laboratory (MSL), or Curiosity as it is more commonly known, was to be a mobile analytical lab to explore the past and present habitability of Mars. The planetary science community wanted a mission that could better answer whether or not Mars, either currently or in its past, could support organic life. To do this, Curiosity needed to get to the subsurface of the planet.

Why go below the surface?

One of the things we have learned from the last 40-plus years of Mars exploration is that the exposed surface of Mars is incredibly inhospitable to organic matter. Two main things contribute to the breakdown of organic matter that is exposed at the surface. Lacking much atmosphere or a global magnetic field, Mars suffers intense solar ultraviolet radiation and is unprotected from cosmic radiation. Also, its soil and airborne dust contain oxidizing compounds that quickly break apart larger molecules. To maximize the chance of finding protected organic matter, it would be best to dig tens of centimeters, or more, below the planet’s surface.

However, the sampling acquisition system architecture for Curiosity was constrained to be a relatively compact shallow subsurface sampling capability that could be carried by a rover. There were a number of factors that we tried to balance to maximize the overall chance of mission success. Successfully drilling bore holes in a distant planet is not a trivial engineering endeavor. The science community also wanted the ability to sample a variety of terrain types and features and to get to the best candidate targets. We also wanted to be able to take advantage of Mother Nature’s deep drilling operations -- impact craters -- just as Opportunity has at Meridiani Planum. Our system balances these desires for mobility and subsurface access with the technical risks and a responsible caution about sampling methods never before attempted on another planet, millions of miles away.

Many resources exist on the Web and in the in the literature (journal and conference papers) describing the specific elements of the MSL SSS system (Google is a wonderful thing, but the MSL pre-landing press kit is a good place to start). There are three major subsystems that make up the Curiosity SSS system:

The Sample Acquisition, Processing and Handling subsystem (SA-SPaH)

The Sample Analysis at Mars (SAM) Instrument

The Chemistry and Mineralogy (CheMin) Instrument

The Sample Acquisition, Processing and Handling subsystem (SA-SPaH)

The SA-SPaH subsystem is comprised of the following: three motorized inlet covers for the instruments; a robotic arm having three turret-mounted tools; and some body-mounted, non-mechanized hardware.

The robotic arm mass is approximately 70 kilograms, and carries a 30-kilogram turret at its end. The arm has five degrees of freedom (two each in "shoulder" and "wrist", and one at the "elbow") The three turret-mounted tools are a drill; the sample processing hardware; and a dust removal tool. The sample processing hardware includes an integrated regolith scoop. This sample processing hardware’s full name is the Collection and Handling for In situ Martian Rock Analysis tool, or CHIMRA—acronym engineering at its best. (It's pronounced like Chimera, the multi-headed beast of Greek mythology.)