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 60oC) 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.


MECA Instrument Box
Figure 1.  Packaged within the MECA box were the; microscope sample stage mounted on a translation table; four wet chemistry cells; microscopy assembly including dual-magnification optics, visible camera, and AFM; and electronics.


MECA WCL Sensor Array Cell Construction
Figure 2.  Details of the WCL construction. The WCL is housed in an anodized aluminum enclosure, an inner beaker of cast epoxy serves as reaction vessel and platform for the electrochemical sensors that populate all four walls.  The sensors are fitted into machined holes such that the sensing surfaces face into the beaker and connection wires face out . 


Robotic Chemical Analysis Laboratory (RCAL)
Figure 3. The Robatic Chemical Analysis Laboratory.
 

References

Please Note: The published materials available below are strictly for personal use and in
accordance with the applicable copyright laws.

[1]  "The Mars Environmental Compatibility Assessment (MECA) Wet Chemistry Experiment on the Mars '01 Lander", S. M. Grannan, M. Frant, M. H. Hecht, S.P. Kounaves, K. Manatt, T. P. Meloy, W. T. Pike, W. Schubert, S. West, X. Wen, in Workshop on Mars 2001: Integrated Science in Preparation for Sample Return and Human Exploration (Eds: J. Marshal, C. Weitz), LPI Contribution 991, Lunar and Planetary Institute, Houston, 1999, pp 41-42. Full Text PDF

[2]  "Electrochemistry on Mars", S.J. West, M.S. Frant, X. Wen, R. Geis, J. Herdan, T. Gillette, M. H. Hecht, W. Schubert, S. Grannan, S.P. Kounaves, American Laboratory, 1999, 20, 48-54 Abstract - Full Text PDF

[3]  "Atomic Force Microscope for Planetary Applications" T.Akiyama et al., Sensors & Actuators, 2001, A 91, 321-331 Full Text PDF

[4] ."The MSP'01 Mars Environmental Compatibility Assessment (MECA) Wet Chemistry Lab (WCL): A sensor array for chemical analysis of the Martian soil", S. P. Kounaves, S. R. Lukow, B. P. Comeau, M. H. Hecht, S. M. Grannan-Feldman, K. Manatt, S. J. West, X. Wen, M. Frant, and T. Gillette, J. Geophys. Res., 2003, 108(E7), 5077-89 Abstract - Full Text PDF

[5]. "Analysis of Simulated Martian Regolith Using an Array of Ion Selective Electrodes", S. R. Lukow and S.P. Kounaves, Electroanalysis, 2005, 17, 1441-49. Abstract - Full Text PDF 



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Last Updated: 06/06/2006