After a voyage of five years, Nasa’s Jupiter probe has slid into polar orbit with perfect accuracy. It is not the first spacefarer to show an interest in Jupiter — Galileo stayed with the planet from 1995 to 2003. But while Galileo sent a probe down to Jupiter’s atmosphere, Juno will barnstorm the planet, braving magnetic and gravitational fields which could fry its instruments. But now, they should be able to see through the cloud-wrack which muffles Jupiter and, for the first time, look into the heart of a gas giant. The mission is aptly named — in Roman mythology, only Jupiter’s wife Juno saw the god as he really was.
Juno is a triumph of Nasa’s New Frontiers programme, which is focused on planetary science. It will swing into action in August, when it approaches closest to the cloud-tops, and will settle into a comfortable rhythm months later, when it enters a stable 14-day orbit, which will last until it drops into the atmosphere and burns up in February 2018. In this time, it will study the very phenomena which will finally slay it — the powerful magnetic and gravitational forces in play, and particularly the magnetosphere at the poles. But it will also attempt to gather data about the surface, which may have a rocky core, and the atmosphere, whose turbulence makes an Earthside hurricane look like a light breeze.
Juno has nine eyes and ears pointed at Jupiter. Will it shed light on Jupiter’s most intriguing feature, which fascinates both scientists and schoolchildren — the Great Red Spot, an anticyclone twice the size of the Earth which is at least as old as the first telescope? Space exploration is the greatest adventure of our era, but every discovery it makes does tend to take the edge off the universe’s myths and mysteries.