Galileo’s Probe Sends a Weather Report from Jupiter

A nalyzing data from the Galileo spacecraft, which has been orbiting Jupiter since 7 December 1995, is not a job for those who require instant gratification. Delayed for three years after the Challenger disaster, the spacecraft then spent six years in its 3‐billion‐kilometer journey to the Solar System’s largest planet. Moreover, because Galileo’s high‐gain antenna never fully unfurled, the spacecraft must instead transmit data using its low‐gain antenna—at the glacially slow rate of a few tens of bits per second. When one knows as little about a system as we do about Jupiter, however, a trickle of data can unleash a flood of new results. The most recent results, based on in situ measurements of Jupiter’s atmosphere and innermost magnetosphere by Galileo’s probe, have raised questions about the giant planet’s composition, even as they have resolved some fundamental questions about the driving force of the zonal, or east‐west, winds that give rise to the planet’s banded appearance. Because of Jupiter’s large size, and because it is thought to have a near‐protosolar composition, these results may have important implications not just for our understanding of Jupiter and similar planets, but also for our ideas on the formation and evolution of the Solar System.