The Problem With Dust On The Moon And Mars
A coal mine — that’s how astronauts described the interior of Apollo 12’s lunar lander Intrepid when it took off from the moon in 1969.
Moonwalkers Pete Conrad and Alan Bean had spent eight hours out on the lunar surface, tracking in enough dust to cover their faces, suits, and capsule in soot. Once they entered orbit, the floating zero-g dust turned hazardous. “I took my helmet off and almost blinded myself,” Conrad later recalled.
Even after air scrubbers removed most of the material, Command Module pilot Richard Gordon deemed his crewmembers’ suits too dusty to bring into the clean spacecraft. So Conrad and Bean stripped naked, stuffed their suits in a zippered bag, and floated over wearing only their headsets. The fine dust particles proved wily, slipping past the zipper, cycling through filters, and collecting on circuit breakers during the flight back to Earth. While on the moon, that same dust had overheated instruments, clogged the astronauts’ wrist locks, irritated their eyes and lungs, and eaten through several layers of Mylar in their suits.
“You realize they were only there a couple days and many of their systems were near failure,” said Boeing engineer Greg Gentry, who works on life support for the International Space Station. “A big reason was the dust environment.”
Yes, dust. That stuff you wipe off the mirror and sweep from your cabinets. The dust in your house — mostly made of tiny sand particles, plant pollen, and skin flakes — is innocuous, practically inconsequential. But dust on other worlds is not something to be ignored. Lunar dust scratches everything it touches, Martian dust could burn human skin. Both are likely to cause significant health risks to astronauts.
Dust is easy to overlook. But Apollo 17 astronaut Gene Cernan described it as “probably one of our greatest inhibitors to a nominal operation on the moon.” NASA’s Mars Exploration Program Analysis Group listed it as the top concern requiring further study before sending a human crew to the Red Planet. Any future manned mission considering going to these places will need a detailed plan to tackle the myriad problems of dust.
The moon’s cratered appearance is testament to a 4-billion-year-long meteorite assault. With no atmosphere to burn them up, even the tiniest of micrometeorites impact the lunar soil, breaking microscopic shards off the volcanic silica rock that composes the surface. Heat generated during the collision partially melts this debris, which rolls around and sticks to other razor-sharp slivers from previous impacts.
With no weathering and water around, the lunar dust “starts sharp and never really gets dull,” said Grant Anderson, President and CEO of Paragon Space Development, which specializes in life-support systems for space.
These micron-sized spikes get bombarded by ultraviolet rays from the sun, giving each grain an electrostatic charge. The result: a highly abrasive material that gets on everything and stays there. Hatches, seals, valves, bearings — any machinery that moves on the lunar surface will be subjected to dust damage. “Imagine sprinkling broken glass onto a seal,” said Gentry. “And then every time you cycle it, you sprinkle more glass. Sooner or later it’s going to leak.”
After three days on the moon, Apollo 17 astronaut Harrison Schmidt threw away his geologic hammer because the handle had corroded away. A tumble into the dust left scratches on his helmet that created a blinding glare each time he turned toward the sun. Abrasion rendered dials and gauges on the Apollo moon buggies unreadable. Even duct tape — that fix-it-all item beloved of engineers throughout the known universe — became useless in the presence of lunar dust. “Once you got a piece of tape off the roll, the first thing the tape stuck to was dust; and then it didn’t stick to anything else,” Cernan later explained.
Moon dust practically laughed at Apollo astronauts’ attempts to remove it. Brushing could eliminate the larger grains, but the fines wormed their way into everything. This dark dust absorbed sunlight, causing thermal problems for radiators and spacesuits. The moon buggies’ batteries exceeded their operational temperature limits in a matter of days because of dust accumulation.
More troubling are the human biomedical problems associated with moon dust. Apollo astronauts complained of congestion and “lunar hay fever” during their short stays on the moon. This was probably due to the fractured silica particles they breathed in. On Earth, our lungs use cilia to sweep dust up and out of our central airways. But experiments suggest that in the moon’s lower gravity, dust deposits in the periphery of the lungs, where no cilia are present. Over time, this could cause respiratory ailments similar to black lung disease or silicosis, a pneumonia-like condition where a patient slowly loses lung capacity.
The dust on Mars will in some ways be easier than that on the moon. The Red Planet has an atmosphere, which burns up pesky micrometeorites, and weather, which files down sharper dust fragments. But Martian dust will contain its own set of hazards for future explorers.
The wind on Mars keeps dust constantly blowing around the planet. Fine as talcum powder, the dust will likely be impossible to keep out of even the tightest seals and zippers. The fictional habitat seen in the movie The Martian would, in real life, be a much filthier place. Dust would find its way behind panels and clog up filters, blocking solar cells from collecting light unless regularly cleaned.
While not as bad as on the moon, Martian dust is still fairly abrasive stuff. NASA’s Spirit rover lost function of one wheel and then another before getting stuck in a sand pit in 2009. Dust was a significant factor in wearing out the wheel bearings, said chemist James Gaier of NASA’s Glenn Research Center. Curiosity’s wheels have similarly “been chewed up way faster than anybody thought they were going to be,” he said.
Because no mission has ever brought back samples, scientists don’t know exactly what makes up Martian dust. But the Red Planet is red because of iron oxide, and Mars certainly contains other mineral oxides and peroxides, which can cause chemical burns. The Pathfinder rover also found trace amounts of carcinogens like hexavalent chromium in the soil.
Recent robotic missions have revealed that Martian soil is full of perchlorates, reactive salts based on chlorine and oxygen. Perchlorates affect the human thyroid gland, leading to goiters, decreased metabolism, and slowed functioning in many organs. Other more reactive perchlorates may cause headaches, skin burns, loss of consciousness and vomiting. A 2013 paper in the International Journal of Astrobiology recommend that astronauts on Mars follow the same mitigation techniques as miners dealing with uranium, lead, and other heavy metals, spraying their suits down with water when entering a habitat and regularly monitoring their blood.
While concerning, none of the problems with dust on the moon or Mars are insurmountable. Scientists and engineers will need data to understand how to design hardier equipment, better seals, and the right ways to deal with health issues. But if we are serious about sending people to either of these worlds, it makes sense to get a move on.
“These are not problems that will be solved in a year or two,” said Gaier. “It will take a lot of testing. I think that we have to start working on this now.”
This story was originally published on the defunct website now.space on 1/20/2016