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Friday, August 3, 2007

Martian Dust: Evidence for Water and Life?

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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July 9, 2003: Something is happening on Mars and it's so big you can see it through an ordinary backyard telescope.
On July 1st a bright dust cloud spilled out of Hellas Basin, a giant impact crater on Mars' southern hemisphere. The cloud quickly spread and by the Fourth of July was 1100 miles wide--about one-fourth the diameter of Mars itself.

Above: These pictures of Mars spanning July 2nd through 6th were captured by Donald Parker of Coral Gables, FL, using a 16-inch telescope. The stubby black arrows indicate the growing cloud. More images: July 1st, 2nd, 3rd, 4th, 6th.
"The cloud can be seen now through a telescope as small as 6 inches," says Donald Parker, executive director of the Association of Lunar and Planetary Observers (ALPO). "Its core is quite bright."

Sign up for EXPRESS SCIENCE NEWS delivery Parker has been tracking the cloud through his own 16-inch telescope. "A red filter helps," he notes. "Even a piece of red or orange gelatin held between the eye and ocular will improve the visibility of the dust."
Two years ago, a similar cloud from Hellas Basin grew until it circled the entire planet. Features on Mars long familiar to amateur astronomers--the dark volcanic terrain of Syrtis Major, for example--were hidden for months. "The planet looked like an orange billiard ball," recalls Parker.
Will it happen again?
"No one knows," says astronomer James Bell of Cornell University who studied the dust storm of 2001 using the Hubble telescope. "We don't yet understand the mechanism that causes regional clouds to self-assemble into giant dust storms."
Mars Global Surveyor and Mars Odyssey, two NASA spacecraft circling Mars, have seen many "regional storms" like the cloud near Hellas Basin now. They persist for a few days or weeks, then dissipate. Rarely do they become a planet-wide event.
"Only 10 global or planet-encircling dust storms have been reported since 1877," notes Parker.
Left: An orange billiard ball: a world-wide dust storm on Mars in 2001 blurred the planet's normally sharp features. [more]
All dust storms on Mars, no matter what size, are powered by sunshine. Solar heating warms the martian atmosphere and causes the air to move, lifting dust off the ground.
Because the martian atmosphere is thin--about 1% as dense as Earth's at sea level--only the smallest dust grains hang in the air. "Airborne dust on Mars is about as fine as cigarette smoke," says Bell. These fine grains reflect 20% to 25% of the sunlight that hits them; that's why the clouds look bright. (For comparison, the reflectivity of typical martian terrain is 10% to 15%.)
Sunlight on Mars is about to become unusually intense. The planet goes around the sun in a 9%-elliptical orbit with one end 40 million km closer to the sun than the other. Mars reaches perihelion--its closest approach to the sun--on August 30th. During the weeks around perihelion, sunlight striking Mars will be 20% more intense than the annual average.
"This means the season for dust storms is just beginning," says Bell.
Above: Mars lies in the constellation Aquarius, which is best seen this month during the hours before local sunrise. Northern-hemisphere sky watchers should look south; southern-hemisphere sky watchers should look northeast to find the bright red planet.
A total of four spacecraft from NASA, the European Space Agency and Japan are en route to Mars now. They include three landers and two orbiters. Will dust storms cause problems for those missions?
Probably not. NASA spacecraft have encountered Mars dust before. The Viking landers of 1976, for instance, weathered two big dust storms without being damaged. As far as researchers were concerned, it was a good opportunity to study such storms from the inside--something Mars colonists may do again one day for themselves. Viking data will give them a head start.
Five years earlier, in 1971, the Mariner 9 spacecraft reached Mars during the biggest dust storm ever recorded. The planet was completely obscured; not even the polar caps were visible. Mission controllers simply waited a few weeks for the storm to subside. Then they carried on with Mariner 9's mission: to photograph the entire surface of the planet. It was a complete success.
As 2003 unfolds, Earth and Mars are drawing together for their closest approach in some 60,000 years on August 27th. Already in July Mars is a pleasing sight. Step outside before dawn anytime this month. Mars will be there in the southern sky, a remarkably bright red star. (If you live in the southern hemisphere, look northeast instead.)
Right: John Nemy and Carol Legate took this recent picture of bright Mars and a meteor above their campsite on Blackcomb Mountain, Whistler, British Columbia.
Even a small telescope will reveal the planet's orange disk and its icy south polar cap. And if "seeing is good" you might catch a glimpse of some dust clouds. Swirling, surging, merging with others ... building the next global dust storm? "They're fun to watch," says Parker. Now is a great time to see for yourself.

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