The Best Targets for Future Exploration; The Future of Space Exploration; Scientific American Presents; by Staff Editors; 12 Page(s)

Like an ill-tempered king, the sun is prone to violent outbursts. Shifts in the sun's intense magnetic fields send monstrous streams of charged particles hurtling through space. This solar wind buffets the planets and sparks the aurora borealis in Earth's Northern Hemisphere. Occasional surges in the solar wind can also silence communications satellites and cause power blackouts on Earth. In the next decade, space agencies in the U.S., Europe and Asia expect to launch a small fleet of spacecraft to study the sun and its fierce flare-ups. One of those probes will even venture into the corona, the sun's fiery outer atmosphere.

Recent solar missions have paved the way. For the past three years, the Solar and Heliospheric Observatory (SOHO) has provided breathtaking images of the sun and its corona. And the Ulysses probe has measured the solar wind and the sun's magnetic field while moving in a distant orbit that allows it to view the sun's north and south poles. These missions suggest that the fastest solar winds, flowing at up to 800 kilometers (500 miles) per second, may arise all over the sun's surface and not just from its poles, as astronomers had previously thought. But scientists still don't understand the physical processes that produce the solar wind, and they cannot predict the occurrence of the solar storms that wreak such havoc on Earth.