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The Best Targets for Future Space Exploration In planning missions for space exploration, the National Aeronautics and Space Administration (NASA) must balance technological and scientific considerations with budgetary limitations. From an array of potential missions, NASA selects a handful that it believes are most likely to succeed and generate useful information. This article from Scientific American Presents identifies several planned and proposed NASA missions that the editors of Scientific American in 1999 believed were most promising. The Best Targets for Future Exploration The Sun Upcoming missions will investigate the sun and the powerful solar wind that it hurls toward the planets Like an ill-tempered king, the sun is prone to violent outbursts. Shifts in the suns intense magnetic fields send monstrous streams of charged particles hurtling through space. This solar wind buffets the planets and sparks the aurora borealis in Earths 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 suns 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 suns magnetic field while moving in a distant orbit that allows it to view the suns 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 suns surface and not just from its poles, as astronomers had previously thought. But scientists still dont understand the physical processes that produce the solar wind, and they cannot predict the o