Martian Dust: Evidence for Water and Life?

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 for water, and carbon compounds that could signify life on Mars. Like its namesake mythological bird, NASA's Phoenix Mission rises from remnants of its predecessors. It will use many components of a spacecraft originally built for a 2001 Mars lander mission, which was kept in careful storage after that mission was cancelled.

This is the second "Phoenix" at the SETI Institute; the first was Project Phoenix which arose after the demise of NASA's High Resolution Microwave Survey (HRMS) in 1992. HRMS had been designed to conduct a broad survey and a targeted star search for evidence of sentient life (aka, signals from technological civilizations) in the Milky Way Galaxy. The SETI Institute picked up the pieces from HRMS, and with private philanthropy, funded a decade of targeted star SETI research using major radio telescopes world-wide under the banner of Project Phoenix.

Today, NASA's Phoenix Mission 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 research scientist at the Carl Sagan Center (CSC) of the SETI Institute with a particular 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 to understand how water and wind have altered the surface of the tiny bits of rock to learn about the geological history of materials here on Earth, and soon, on Mars. Marshall is a co-investigator on NASA's Phoenix 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 and engineers at universities and NASA centers to conduct research onboard NASA space missions.

The Phoenix lander will set down in icy soils near the permanent north polar ice cap of Mars and 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 (in search of carbon-bearing compounds) since the 1970s when NASA's two Viking missions landed on Mars. The science payload for Phoenix includes instruments built for the 2001 lander and improved versions of others flown on the lost Mars Polar Lander in 1999. In particular, Dr. Marshall will be analyzing the images from the microscope that is part of MECA, the Microscopy, Electrochemistry and Conductivity Analyzer which will look at dust 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 is sedimentology, and specifically the study of clastic particles ? these are the sand and dust grains that comprise volcanic eruptions, dust storms, sand dunes, river sediments, beach sand, and so forth. These are grains of dust the size of particles of flour?a few microns in diameter?to the sand grains that you find at the seaside. For three decades, Marshall has investigated the material from two perspectives ?their appearance under the microscope, and their electrostatic behavior. With the Phoenix Mission, he's taking his microscope to Mars, seeking evidence of water and life near the polar ice cap.

What can we learn from dust? If you ask Marshall, the answer is "plenty." Tiny grains of dust and sand record their history as microscopic textures on their surfaces. The effect of water in creating these surface textures can be detected. The Phoenix mission will provide the first microscope images from Mars ? soil particles will be scooped up by a robotic arm, and examined to determine if liquid water has played a role in the physical and chemical evolution of materials at the landing site. Elucidating the role of liquid water on Mars using microscopic clues can provide valuable information about ancient climates on Mars, and the potential for life to have evolved there. Dr. Marshall is the lead scientist for geological interpretation of the size, shape, and textural characteristics of soil particles examined by the Phoenix mission microscope.

Marshall works on planetary protection as well: when we send a spacecraft to Mars, how can we keep from forward-contaminating the site with materials that actually originate from Earth? The Phoenix Mission will be looking for evidence of water and life on Mars, and Marshall and the other scientists on the team do not wish to discover Earth-derived materials instead of Martian materials. Later this year, Marshall and 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 spacecraft during landing and deposited on nearby Martian soils. If carbon-compounds are discovered on Mars, the team wants to be sure that they are Martian.

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

Recently, I asked Marshall about his career as a research scientist and how he'd taken this pathway that is now leading to Mars. He said, "While space is a great place to extend my research on the nature of particles and their interactions, I'm fundamentally motivated to understand the basic nature of particulate materials. I'm a scientist, and when all is said and done, I'd like to be distinguished as the guy who did fundamental work on clastics, here on Earth and elsewhere, including Mars. My scientific discoveries are most important to me. Rather than being thought of as a Mars scientist who did something with samples of Martian soil, I'd like to be respected for my research into particulate materials. For me, space is simply a good place to do excellent science, and that's what motivates me."

With more than three decades of specialized research, Marshall looks forward to reading the stories written in Martian dust in the near future when the microscopic images are transmitted to Earth from the Phoenix lander. With Marshall, we'll all learn more about water on Mars, and perhaps about life on that small red world.

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