Taking a Close Look at the Soil on Mars

Abstract

A s NASA and the space research community embark on a far reaching plan to survey Mars from orbit and explore its surface we face the challenge of needing to rapidly expand our scientific understanding of the red planet with severely limited resources. Driven by NASA's goal of working 'faster, better, and cheaper', roday's planetary missions, while greater in number, are carried out by smaller spacecraft developed with shorter lead times and with budgets a fraction of the size of those available to earlier space probe missions. The Mars Pathfinder and Mars Global Surveyor missions, both of which launched in late 1996, were accomplished in a third the time and for a tenth of the cost of the Viking missions twenty years before. At each two-year launch opportunity NASA is planning to send two spacecraft to Mars culminating in a sample return mission in 2005 or 2007. Re-inventing analytical instrumentation to accompany these smaller spacecraft to the harsh environment of the Martian surface presents numerous challenges. The Mars Environmental Compatibility Assessment (MECA), currently under development at the Jet Propulsion Laboratory, is an instrument suite designed to study the Martian soil and dust. The challenges associated with the task and the path that the M ECA team has proposed to meet them are the subject of this article. In preparation for human exploration of Mars NASA will send experiments on the 2001 and 2003 Mars Surveyor lander to gather information which will be of use in assessing potential hazards to astronauts and their equipment on Mars. Dust is an element that is ubiquitous in the Martian environment and one with which astronauts will surely need to contend over the course of a one year stay on the planet. MECA was competitively selected in January to provide future mission planners with additional information about the Mars dust and soil and potential hazards associated with it. The experiment payload was required to fit inside a 15x15x45 ern box mounted and in its entirety could not weigh more than 8 Kg. Average power supplied to an instrument set would be no more than a few watts and no provision for heat ing or thermal insulation was specified. Temperatures in the thin Martian atmosph ere, (Patrn = 7 torr, 95% of which is carbon dioxide), range from above freezing during the day to as low as 100 oC at night. The experiment would rely on the lander for a fraction of the 20 watts available to all the instruments on board as well as for data storage and a communication link. It would also have use of a lander mounted robotic arm fitted with a camera for soil sampling and acquiring images. The MECA instrument suite is primarily designed to assess any hazardous character of the Mars soil but it will also yield a substantial amount of scientific data on the make-up of the Martian regolith. A microscopic inspection will determine the shape , texture, color, and size distribution of soil particles. MECA will determine the adhesion potential (electrostatic , magnetic , physiochemical , mechanical) of dust to a variety of materials under ambient conditions. It will directly measure the ability of part icles to abrade and scratch materials such Robotic arm scoop and camera