PRESTON, U.K.--Many people would get a charge out of standing on the moon, but a little extra electric charge could endanger the astronauts who visit it in the second half of the next decade. During this period, the moon will pass through part of Earth's magnetosphere, causing static electricity to build up on the lunar surface, a space scientist reported here today at Royal Astronomical Society's National Astronomy Meeting. The resulting charge could short-circuit electronics and affect the behavior of lunar dust particles, which are fine enough to enter living quarters and even spacesuits.
The moon may look serene as it hangs in the night sky, but its surface is a hostile and dangerous place. Temperatures in the darkened portions of the moon plunge to -170 degrees Celsius, whereas those in the light climb as high as 100 degrees. And the moon has no atmosphere to shield it, so its surface is continually pelted with radiation from space. But static electricity may also severely hamper future missions to the moon, says space scientist Mike Hapgood of the Rutherford Appleton Laboratory in Chilton, U.K.
Electrical charging is one of the less well known natural hazards of spaceflight, Hapgood says. The lunar surface charges up roughly every 18 years because of changes in the orientation of the moon's orbit. For a number of years during each peak, the orbit intersects the so-called plasma sheet--a thin region in Earth's magnetosphere that contains many electrically charged particles from the sun. These particles crash into each other and charge the lunar surface, as has been witnessed by NASA's Lunar Prospector spacecraft in 1998, during the last maximum. A geometric analysis of the moon's orbital changes shows that electrostatic charging of the lunar surface was low during the Apollo era, but it will be high in the second half of the next decade, when various space agencies are planning to send robots and people to the moon, Hapgood reports. That could be a real hazard to sensitive electronics, but also to astronauts because electrostatically charged dust particles would tend to stick more easily to any surface, so they're harder to get rid of.
Chief scientist Bernard Foing of the European Space Agency says the hazard must be taken seriously. "It would be useful to develop precursor monitors that could measure the electrostatic properties of moon dust," he says. Rolf de Groot of the SRON Netherlands Institute for Space Research in Utrecht believes the problem is manageable, though, at least for crewless missions. "Of course, we'll have to make sure lunar surface charging doesn't pose a health threat to astronauts," he says, "so designers of moonsuits will have to take note."
Meanwhile, Hapgood has teamed up with his Rutherford Appleton Laboratory colleague Ruth Bamford in fighting another spaceflight hazard: radiation. During a long stay on the moon or a flight to Mars, energetic particles from the sun or from outer space may cause radiation sickness, skin cancer, and even death. Bamford told the meeting her team is now designing a high-tech Star Trek-like deflector shield that works like a miniature version of Earth's protective magnetosphere.