Beyond Earth

An astronaut in low earth orbit 150 miles up—on the space shuttle, say, or in the International Space Station—will intercept the occasional cosmic ray: “You'll see flashes of light, of color, even with your eyes closed,” said James Pawelczyk. An assistant professor of physiology and kinesiology at Penn State, Pawelczyk is a former NASA astronaut who flew as payload specialist aboard the shuttle Columbia in 1998, logging 16 days and 6.4 million miles in space. He gave the fourth lecture in the 2003 Frontiers of Science series, entitling his talk “What Price a Martian? Human Limits to Exploring the Red Planet,” and discussing whether current technology can overcome the problems faced by space-hungry primates that evolved on and remain adapted to Earth.

dust storm on Mars
NASA/JPL/MSSS

This dust storm on Mars in August 2000 was photographed by the Mars Global Surveyor Orbiter from an altitude of 230 miles. Dust storms alter the Martian climate and would represent a hazard to earthlings venturing onto the red planet.

When galactic cosmic rays hit skull or bone, the collision “creates secondary ions,” Pawelczyk explained, “some with very high energy.” The ions can rip through cellular DNA, causing “phenomenal damage.” While DNA has the capacity to repair itself, some mutations persist and become incorporated into an individual's genome. As we build up such damage, and as we go about replicating our bodies' basic units—“We pretty much turn over all the cells in our body in one year”—the likelihood of developing cancerous tumors increases.

“We don't understand space radiation very well,” Pawelczyk admitted. “We could be off by an order of magnitude either way” in our estimation of how much radiation an astronaut might absorb during an extended stay in space. Since a voyage to Mars and back might take three years, astronauts could be exposed to massive amounts of radiation as they travel in a craft lacking a planet's magnetic field to filter out rays. Space vehicle design can limit exposure somewhat—one possibility is to barricade astronauts' living quarters behind water-storage tanks—but cannot eliminate it. Then there are solar flares, unpredictable events in which the sun releases great pulses of radiation potentially fatal to astronauts. Pawelczyk suggested, as a first step in studying long-term effects of radiation, placing animal surrogates on the International Space Station.

He listed “human challenges to a Mars expedition,” areas that need to be addressed before we blast off for the red planet. The three “severe challenges” are radiation effects, bone loss, and the harsh Martian environment. Other difficulties include muscle loss and problems with cardiovascular, neurological, immunological, and psychological health. “Three [space] missions have been terminated prematurely,” Pawelczyk noted, “all in the Russian program, for psychological reasons.” He paused and summarized: “How are we going to keep people from killing themselves when they're cooped up in a can for a three-year period?”

It may be pleasurable to float around upside-down while sipping your Tang, but the zero-gravity environment of space has serious consequences for the skeleton. Pawelczyk noted that of the 430 people who have flown into space so far, only six have stayed there longer than eight months, all of them Russians aboard the Mir space station. Those cosmonauts showed severe bone loss, particularly from the lower spinal region down through the legs and ankles, on the order of 1.5 percent for every month spent in space—about 15 times the rate of a post-menopausal woman suffering from osteoporosis. Projected over 30 months, a space traveler could conceivably lose 45 percent of his or her bone mass and “end up with the bone density of a 100-year-old,” Pawelczyk said.

Engineers have proposed rotating space-craft that would create their own partial gravity field, but you can only spin a person so fast before nausea kicks in. A better solution, according to Pawelczyk, may be pharmacological: drugs that slow the reabsorption of bone, some of which are now undergoing clinical trials. At present, International Space Station crew members are experimenting with a “lower extremity monitoring suit” that measures forces on the feet and joint angles, as well as muscular activity during typical daily life in space.

According to Pawelczyk, some scientists suggest that a strict exercise regimen can prevent physical deterioration. Here, simple logistics may be an insurmountable barrier. Sixty minutes of exercise a day, over a two-year space mission, requires carrying along an extra metric ton (approximately 2,200 pounds) of food, a ton and a half of water, and three and a half tons of oxygen per astronaut. Can we afford to tote such quantities of supplies on board a spacecraft? Probably not, at the current rate of $10,000 per pound to place materials in orbit.

Pawelczyk cited the 18th-century American explorers Meriwether Lewis and William Clark: “They didn't try to take everything with them.” We would need to do the same on Mars by attempting, as much as possible, to “live off the land.” Ice, if it is found in quantity, could be melted for drinking water; from the water, oxygen could conceivably be recovered.

It would be a struggle just to stay alive, let alone remain active enough to exploit any resources found on Mars. The average temperature on Earth is 18 degrees C.—in the 50s F. On Mars, it's -90 F. The atmosphere here at home contains 78 percent nitrogen, 21 percent oxygen, and, despite the vaunted greenhouse effect, only five thousandths of a percent carbon dioxide: on Mars, look for 95 percent CO2. The air would be, Pawelczyk noted, “a rich source of carbon. If we have carbon, hydrogen, and oxygen, we can make methane—a pretty reasonable rocket fuel,” useful for returning astronauts to Earth.

But before they decamped from the red planet, space pioneers might have to contend with dust storms “on a planetary scale,” said Pawelczyk, involving “up to 70 percent of the surface of Mars at some times of the year,” with winds to 200 miles per hour. Dust devils, like little tornadoes, go stalking across the rocky soil. “So you're going to need a good habitat,” Pawelczyk said, probably a semi-rigid, gas-inflated structure that will include radiation shielding.

Critical to humans ever making landfall on Mars is a much-improved understanding of the planet's radiation levels—“We're still fairly fuzzy about the radiation environment on the Martian surface”—and the possible presence of microbes. Pawelczyk cited a NASA mission currently proposed for 2007, Mars Scout, in which a lander would release a robot to secure a soil sample that the craft would then carry back to earth. An analysis of the sample might better reveal the chemistry of Mars and any potential biological activity.

As Mars imaging gets better, mission planners will be able to pinpoint sites on the planet where astronauts could land and live. We're not there yet. Pawelczyk showed a picture of an undulating landscape on Mars, interrupted by a highlighted zone marked with an X next to a dimple that depicted “a steep crater about 70 feet deep.” He identified the X as the probable landing site of the Mars Polar Lander, a NASA probe that attempted a landing in 1999, after which communication with the craft was abruptly lost. The defunct lander, suggested Pawelczyk, “is probably sitting in a heap at the bottom of that crater.”

Pawelczyk said it was possible that humans would go to Mars “in our lifetimes,” although currently, especially in the wake of the loss of the shuttle Columbia, “we don't have the political will” to do it. He suggested that budgeting “several billion dollars per year” could ultimately see NASA through to a manned Mars mission. He noted that NASA's current total budget of around $15 billion amounts to only three-quarters of one percent of national spending.

The former astronaut characterized NASA as “conservative, pragmatic,” and likely to thoroughly “check out technologies on the Moon before sending a crude mission to Mars.” He also cited the International Space Station as an excellent laboratory in which to test a Mars habitat and catalog the various human miseries that can accumulate in space. “Once the Russians lost the race to the Moon, they made a conscious decision to set up space stations” —and now they have a 30-year history of development in this field. Pawelczyk advocated finishing the International Space Station and sending scientists aloft to continue working, and experimenting, with the Russians there.

Last Updated May 01, 2003