The NASA PHOENIX probe landed on Mars on May 25th 2008 in a region close to the northern polar ice cap (68 ° N). On board, among the instruments, there was the atomic force microscope, "FAMARS" (for “First Atomic Microscope On Mars') designed by the team of Professor Nico de Rooij and Dr. Sebastian Gautsch of SAMLAB (IMT / EPFL-Neuchâtel). The data collection stopped, as planned, in November 2008, the approaching extreme cold of the Martian winter no longer allowing the operation of the instruments on board. Following the impulse of John Marshall, Ph.D. in geology from University College London and researcher at the Carl Sagan Center (SCC) of the SETI Institute who specializes in clastic particles (dust produced by nature), one of the objectives of the mission, led by Peter H. Smith, Senior Research Scientist at the University of Arizona, was to study the Martian dust. This dust is so fine (a few microns) that, to be able to examine it, it is necessary to use a microscope with a discrimination power higher than the optical microscope. It was imperative that this dust be examined in situ because the problems it poses, resulting not only from its own chemical and physical characteristics but also from very specific conditions of the Martian environment (drought, gravity, temperature) and the "laboratory "where these conditions can best be met, is the planet Mars itself. The interest of the study is first of all a scientific one and is key to understand Mars. The dust grains are indicators of the current geology of the planet and witness of its past history. We can infer this geological state and this history from the appearance and texture of the grains. The winds of the atmosphere are stirring them since billions of years and water, active on Mars for a few hundred million years, undoubtedly left its imprint. The degree of wear and blunting of the grains should therefore allow improving our estimate of the importance and various forms of erosion it went through. It was also necessary that the study be made quickly (before a possible sample return) because the dust is very present in the atmosphere as a result of winds, low gravity, lightness grains and their strong electrostatic charge (on account of their chemical composition and triboelectric effect due to the extremely dry air), is problematic for the proper functioning of machines (seizure of joints, dusting of the solar panels) and for working and health conditions of men (which should be now considered). In this regard, the very small grain size (fine) would facilitate their penetration deep into the lungs and their infiltration into the spacesuits and habitats. The fines are certainly less sharp than on the Moon because there was and there is always erosion on Mars, but they are potentially very dangerous. Moreover, their electrostatic charge makes them extremely "sticky". The instruments aboard PHOENIX for the study of dust (and more generally of the ground), collectively referred to as "MECA" which stands for "Microscopy, Electrochemistry, and Conductivity Analyzer”, has been developed with the Jet Propulsion Laboratory of NASA (JPL), and include, in addition to FAMARS, an optical microscope, various instruments and chemical reagents for chemistry experiments (such as embarked on the Viking probes but much more precise), and an apparatus for physics experiments (adherence and conductivity of materials). Unlike optical or electronic microscopes, the atomic force microscope does not “see” the matter, but rather feels it. The device uses extremely small sensors (the experts call them "spikes") attached to very flexible cantilevers, to feel the surface of samples and construct a very precise 3D representation (a topographic map). FAMARS was used to study the Martian soil at the nanoscale and was able to observe particles of one micron (1μ). The instrument consists of 8 cantilevers to perform eight experiments (once used, a cantilever has to be discarded). There were two challenges in the design and making of the instrument: (1) the size because in order to maximize the load of instruments that PHOENIX could carry, it was mandatory to push miniaturization as far as possible and (2) automation because distance from Earth would not allow to directly intervene and would not allow messages to be answered in less than half an hour.The last of the MECA instruments, a conductivity and thermal power probe, was attached to the fingers of the robotic arm. It was used to study the behavior of electrostatic dust. Its tips were planted at the ends of the trenches dug to collect the samples. Apart from the weather, the probe measured the thermal properties of the soil, thus providing a better understanding of the interaction between surface and atmosphere. Using the same tips, the instrument measured the electrical conductivity of the soil to find moisture in the soil, likely to appear during the excavation sampling. Besides the progress PHOENIX allowed us to do so in the knowledge of the soil of Mars, we must think for tomorrow, when manned flights begin, to the equipment that will prevent the intrusion of dust. In the habitat, we will first of all need to properly equip the airlock. For the astronauts, we will have to devise the proper masks filters. The joints of suits and vehicles will have to be specially protected and the astronauts will need powerful vacuum cleaners equipped with suitable filters and a compact and efficient dust evacuation system. Vehicles must, as rovers and spacesuits for astronauts, need antennae that dissipate static electricity. Generally antistatic materials should be used in all facilities exposed to the outside. They are still challenges ahead but challenges are what push for progress in the adaptability to Space and a better life on Earth. At our December of 3rd conference 2009 in Neuchâtel, Sebastian Gautsch explained how FAMARS operates and what results it brought us. Pierre Brisson
Gale CraterMars Society Switzerland
Methane Atmosphere Curiosity 1The Martian dust
Geology & Atmosphere
SGM2010 Frozen CO2 Oceanus Borealis Pressures Changes