Sending astronauts to Mars will present a host of health risks, from radiation showers to sheer boredom. One of the biggest threats is the extra-fine dust that coats the planet. And the problem is, researchers have never had any sample of the powdery grit to study, so they don't know exactly how it behaves or what its health effects might be.
Two enormous dust storms raging on Mars now serve to remind scientists of the threats facing future Martian explorers.
Among the concerns: Astronauts could get a real charge out of simply walking around.
When a manned mission arrives at Mars, a goal President George W. Bush set for NASA, dust could coat equipment like electrostatic spray paint, short out electronics in a spacesuit, or even zap a craft and prevent astronauts from coming home. Meantime, inhaling the tiny particles will have potential health consequences that are unknown today.
A shocking problem?
"The surface dust on Mars is probably 50 times finer than on Earth," said John Wilson, a planetary scientist at the National Oceanic & Atmospheric Administration in Princeton, New Jersey. Because the ultra-fine dust exists in an extremely thin and dry atmosphere, Wilson and other scientists think it poses some unique problems.
"If you walk through, pick up or simply touch the dust, it would gather charge and stick to you. We've already seen this on the rovers' wheels," said Geoffrey Landis, a physicist with the NASA Glenn Research Center in Cleveland, Ohio. "Things get even more interesting when winds come by and separate the charge."
Landis explained an astronaut would be a walking electric field and attract even more dust to the spacesuit. The theoretical phenomenon is known as the triboelectric effect and is similar to the current generated while walking across a carpet floor during the winter, when the air is extremely dry and can't soak up static charge well.
"As you walk, you scrape off electrons in the carpet and into your body. When you reach for the door's handle, those electrons jump and create an arc," he said. Such a zap of electricity during a Mars surface mission could damage sensitive electronics in a spacesuit or aboard a landing vehicle unless precautions were taken, he explained.
"Very finely pointed needles can help leak off built-up charge to the atmosphere, which is what is on both of the Mars Exploration Rovers," Landis said. "For a human explorer, though, this is a materials science problem. Suits will have to be designed out of poorly conducting material so charge doesn't build up easily."
After a scientific foray across the Martian landscape, astronauts will then have to worry about contaminating their precious habitat with dust.
Russell Kerschmann, a pathologist at the NASA Ames Research Center in California who is studying the effects of mineral dust on human health for future lunar missions, thinks Martian dust could be dangerous due to its fineness and unknown chemical makeup.
"If dust particles are too big, they won't make it deep inside the lungs" where most lung-based diseases and disorders originate, Kerschmann said. Still, in gravity only 38 percent of the Earth's, the dust may hang around in living spaces longer and penetrate more deeply into astronauts' lungs if particles are small enough.
Kerschmann noted that an upside to Martian dust is that billions of years of wind erosion have most likely polished the dust grains to a minimally toxic level.
"The more weathered a dust grain is, the more spherical its shape is and the less toxic it is," he said. Kerschmann thinks moon dust is at the other end of the spectrum: Its dust particles are jagged, glassy shards created by meteorite impacts and haven't been weathered a bit, since there is no lunar wind.
"There's some evidence people are allergic to moon dust. Astronauts and ground crews who came into contact with it complained of nasal congestion and irritation," Kerschmann said.
As for the ultimate threat of Martian dust to humans, Kerschmann was confident in the fidelity of a mission to Mars. Even if the dust is chemically toxic, he thinks engineers will be clever enough to work around it.
"It should not be a show stopper as far as a future manned mission is concerned," he said.
Once astronauts weather their Martian sinus infections and gather a trove of information about the red planet, they'll need to return home safely. David Beaty, chief scientist for NASA's Mars Program, said this step may be the most dangerous to a manned mission's success, as dust storms on Mars can engulf the planet in just a few weeks' time and last for months.
"There's been a lot of discussion about whether it would be possible to launch from the surface in the middle of a storm, but our scientists just aren't sure about its effects," Beaty said.
Yet at less than 1 percent the density of Earth's atmosphere, Beaty thinks Mars' thin atmosphere shouldn't have a major effect.
"Martian wind speeds are about 10 to 15 meters per second (33 to 50 mph), but there's not a lot of mass moving," he said. If dust storms did prevent departure, however, Beaty said being stuck in a Mars habitat for months would be a real problem.
"It could also compress a sensitive window for departure back to Earth," he said.
Beaty and other Mars scientists firmly believe returning intact samples of Martian grit will be essential to a future manned mission's success.
"We haven't done as much research on Martian dust as we'd like, and it's because we don't have a sample," Beaty said. He said the rovers and other spacecraft have returned invaluable information, but more is needed.
"Could Martian dust cause corrosion? Short our electronics? These are open questions," Beaty said. "We don't know what it's made out of, and we need to know in order to optimize the safety, performance and cost of a manned mission to Mars."
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- Gallery: Visualizations of Mars