January 1999

Missionaries to Mars

Continued from page 2

By James Oberg

On a Wing and Thin Air

while mars enthusiasts may not yet know enough about the martian soil, they already know one important thing about the martian air: It is very thin. And though the martian atmosphere has less than 1 percent of the pressure of Earth's atmosphere at sea level, a few aerospace engineers are drawing up blueprints for small unmanned airplanes capable of flying across vast expanses of the martian terrain. Such a plane's instruments could survey complex geological regions, including many that look too rough for surface rovers.

Larry Lemke, a robotics expert from NASA's Ames Research Center in California, told a plenary session about one winged mission. A 150-kilogram vehicle with a 10-meter wingspan, on the scale of a powered hang glider here on Earth, would be launched from Earth folded inside a probe. After the probe entered the martian atmosphere, it would drop its heat shield and pop open a small stabilizing parachute. The airplane would unfold itself during the descent, and detach from the parachute for its free flight. The winged robot could carry 20 kilograms of instruments, including an infrared pointed spectrometer to map mineral and ice deposits, and a suite of geophysical field instruments to spot traces of the planet's geological history. Lemke's team has already charted a 2,000-kilometer, three-hour course down Mars' Vallis Marineris canyon (which is longer than the United States is wide).

The thin martian air, Lemke insisted, would not be an issue. At the planet's surface, he pointed out, Mars' air pressure is about the same as Earth's at 24,000 meters' elevation. Since NASA's unmanned solar-powered "Pathfinder" aircraft routinely cruises at this altitude on Earth, it provides the proof of concept that a more specialized vehicle could also fly on Mars. "Aerodynamics is not a problem," Lemke told the meeting.

Nor is technology a problem, Lemke said. "The Mars airplane has benefited from a lot of technological advances over the last 20 years from areas with no connection to astronautics. There has been work in radio-controlled aircraft, in lightweight structures, in electric propulsive motors, and in military deployment systems."

The concept is so viable, Lemke believes, that he is calling for a launch in the year 2003, to celebrate the centennial of the Wright brothers' first heavier-than-air flights. "We should mark the 100th anniversary of the first airplane flight on Earth with the first airplane flight on Mars," he said.