What is the chemical composition of the dust and soil (regolith) on Mars? What is the geochemical history of Mars?  How can we detect biogenic signatures of past or present life?  What can we learn about earth's environment by studying other planets? Does the surface material pose any hazard to future human explorers? How does one make valid chemical measurements in such an environment?

Chemical analyses of the surface and/or subsurface material in remote hostile extraterrestrial environments such as Mars or Europa, presents a truly daunting and unique analytical challenge.  To undertake such missions, with the slightest hope of obtaining meaningful analytical data, requires instrumentation that can withstand rigors far beyond those encountered on Earth.  In addition to mass, volume, and power constraints, such analytical instruments must be able to withstand extreme temperature fluctuations (-140 to 60^oC) and anticipate any unexpected chemical or physical conditions such an alien environment might present.
 

The MECA Wet Chemistry Lab - Precursor of RCAL The Microscopy, Electrochemistry, & Conductivity Analyzer (MECA) [1-4] is a set of instruments that was designed to provide answers to many of the above questions. The MECA instrument package was developed at NASA's Jet Propulsion Laboratory in collaboration with Thermo Electron Corporation (Beverly, MA), Starsys Research (Boulder, CO), and the Kounaves Group at Tufts University. MECA was flight qualified for what would have been the Mars 2001 Odyssey Lander, but cancelled after the crash of the Mars 1999 Polar Lander. In May 2002 it was proposed as part of the Phoenix Mars Lander, which in August of 2003 was selected by NASA to fly as the 2007 Mars Scout Mission. The MECA instrument package (Figures 1 & 2) includs optical (OM) and atomic force (AFM) microscopes [3] , a thermal and electrical conductivity probe (TECP), and a Wet Chemistry Laboratory (WCL) [1,2,4]. The MECA-WCL contains an array of sensors which allow for determination of a wide variety of inorganic ions and electrochemical parameters, including, Br-, Ca2+, Cl-, HCO3- , I-, K+, Li+, Mg2+, Na+, NH4+, NO3-, SO42-, pH, redox potential, conductivity, temperature, and gas pressure .

RCAL Deployment on Future Rover Missions

The RCAL is being proposed as a geochemical analysis instrument for a future rover mission such as the 2011 Mars Science Laboratory (MSL). It expands on the MECA concept by providing twenty individual sealed sample chambers mounted on a rotating carousel. (Figure 3) The soil, after delivery by an external mechanism such as a robotic arm or sub-surface drill, is loaded into a dual soil hopper.  Multiple small samples can then be taken from the hopper and delivered to the test chambers.  After the chamber is punctured, one of a set of four electrodes mounted over the carousel can be inserted into the selected chamber.  The RCAL will enable a variety of bench-top wet chemistry analyses of the Martian regolith, assessing its interaction with water and various reagents, and ultimately providing unique scientific information about the geochemical and biological history of Mars. 

The research, development, and integration, of the sampling system/sensor arrays, its incorporation on the deck of the 2009 MSL, and their use to analyze the surface material in a remote hostile environment, poses a unique set of scientific and analytical challenges.

Stay tuned for more details.