Martian Dust: Evidence for Water and Life?

Martian Dust: Evidence for Water and Life?
What Phoenix is looking for: Geological evidence of ancient conditions that could have created life, or contemporary conditions that could harbor life.
(Image: © J. Marshall/SETI Institute.)

A Phoenix has reappeared at the SETI Institute, this time in the form of NASA's next Mars lander, which has the involvement of Dr. John Marshall in the science team. NASA's Phoenix Mission is headed to Mars to look forwater, and carbon compounds that could signify life on Mars. Likeits namesake mythological bird, NASA's Phoenix Mission rises from remnants ofits predecessors. It will use many components of a spacecraft originally builtfor a 2001 Mars lander mission, which was kept in careful storage after thatmission was cancelled.

This is the second "Phoenix" at the SETI Institute; the firstwas ProjectPhoenix which arose after the demise of NASA's High Resolution MicrowaveSurvey (HRMS) in 1992. HRMS had been designed to conduct a broad survey and atargeted star search for evidence of sentient life (aka, signals fromtechnological civilizations) in the Milky Way Galaxy. The SETI Institute pickedup the pieces from HRMS, and with private philanthropy, funded a decade oftargeted star SETI research using major radio telescopes world-wide under thebanner of Project Phoenix.

Today, NASA's PhoenixMission is seeking evidence for microbial life on the nearby planet Mars,SETI Institute is involved in this search, as well.

Dr. John Marshall is a researchscientist at the Carl Sagan Center (CSC) of the SETI Institute with aparticular interest; he studies dust. Don't think of him as the "dustman,"rather, he's a geologist who works at the microscopic scale. He studies dust tounderstand how water and wind have altered the surface of the tiny bits of rockto learn about the geological history of materials here on Earth, and soon, onMars. Marshall is a co-investigator on NASA'sPhoenix Mars Mission, which is first scheduled to launch August 3. Phoenix is a "Scout" mission led by PI Peter Smith at the University of Arizona. Like other CSC scientists, Marshall frequently collaborates with scientists andengineers at universities and NASA centers to conduct research onboard NASAspace missions.

The Phoenix lander will set down in icy soils near the permanent north polar ice cap of Marsand explore the history of the water in the ice while monitoring polar climate. Phoenix is NASA's first exploration of a potential modern habitat on Mars (insearch of carbon-bearing compounds) since the 1970s when NASA's two Vikingmissions landed on Mars. The science payload for Phoenix includes instrumentsbuilt for the 2001 lander and improved versions of others flown on the lost MarsPolar Lander in 1999. In particular, Dr. Marshall will be analyzing theimages from the microscope that is part of MECA,the Microscopy, Electrochemistry and Conductivity Analyzer which will look atdust in surface samples.

Dr.Marshall received his training as a geologist at University College London in England, but has spent his professional career in the United States. Marshall's specialty issedimentology, and specifically the study of clastic particles ? these are thesand and dust grains that comprise volcanic eruptions, duststorms, sand dunes, river sediments, beach sand, and so forth. These aregrains of dust the size of particles of flour?a few microns in diameter?to thesand grains that you find at the seaside. For three decades, Marshall has investigatedthe material from two perspectives ?their appearance under the microscope, andtheir electrostatic behavior. With the Phoenix Mission, he's taking hismicroscope to Mars, seeking evidence of water and life near the polar ice cap.

What can welearn from dust? If you ask Marshall, the answer is "plenty." Tinygrains of dust and sand record their history as microscopic textures on theirsurfaces. The effect of water in creating these surface textures can be detected.The Phoenix mission will provide the first microscope images from Mars ? soilparticles will be scooped up by a robotic arm, and examined to determine ifliquid water has played a role in the physical and chemical evolution ofmaterials at the landing site. Elucidating the role of liquid water on Marsusing microscopic clues can provide valuable information about ancient climateson Mars, and the potential for life to have evolved there. Dr. Marshall is thelead scientist for geological interpretation of the size, shape, and texturalcharacteristics of soil particles examined by the Phoenix mission microscope.

Marshall works on planetary protection aswell: when we send a spacecraft to Mars, how can we keep fromforward-contaminating the site with materials that actually originate fromEarth? The Phoenix Mission will be looking for evidence of water and life onMars, and Marshall and the other scientists on the team do not wish to discoverEarth-derived materials instead of Martian materials. Later this year, Marshalland Dr. Rocco Mancinelli, a CSC microbiologist, will run a simulation at NASA Ames Research Center of the Phoenix landing using a one-half scale model from University of Michigan to test how materials might be abraded from the Phoenix spacecraftduring landing and deposited on nearby Martian soils. If carbon-compounds arediscovered on Mars, the team wants to be sure that they are Martian.

Among hisvaried projects, he's also studied dust devils on Earth and Mars, and thesignificant problems caused by dust clinging (actually sticking) to theastronaut's space suits. During the Apollo days, moon walkers became coatedwith lunar dust that clung tenaciously to their suits, boots and helmets,penetrated the space suit joints, and was tracked back into the landers. Inpreparing for the return to the Moon, and human travel to Mars, this remains asignificant challenge: how can astronauts and equipment be protected from theclinging and penetrating dust? It's a work in progress.

Recently, Iasked Marshall about his career as a research scientist and how he'd taken thispathway that is now leading to Mars. He said, "While space is a greatplace to extend my research on the nature of particles and their interactions,I'm fundamentally motivated to understand the basic nature of particulatematerials. I'm a scientist, and when all is said and done, I'd like to be distinguishedas the guy who did fundamental work on clastics, here on Earth and elsewhere,including Mars. My scientific discoveries are most important to me. Rather thanbeing thought of as a Mars scientist who did something with samples of Martiansoil, I'd like to be respected for my research into particulate materials. Forme, space is simply a good place to do excellent science, and that's whatmotivates me."

With morethan three decades of specialized research, Marshall looks forward to readingthe stories written in Martian dust in the near future when the microscopicimages are transmitted to Earth from the Phoenix lander. With Marshall, we'llall learn more about water on Mars, and perhaps about life on that small redworld.



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