As the Juno spacecraft was nearing its objective on 4 July after a five-year flight, the USA Today online headline was, “Humanity’s First Look at Jupiter and its moons.”
As is so sadly common in the shallow media these days, that headline was wildly inaccurate. There have been many missions to Jupiter before this. Galileo orbited the huge gas giant from 1995 through 2003, for example. Pioneer 10 and 11 flew by in 1973 and 1974, as did Voyagers 1 and 2 in 1979. Ulysses took a look in 1992. New Horizons probed its long “magnetotail” in 2007. We have of course analyzed the behemoth and its moons in some detail with powerful scopes like Hubble and Chandra. So we already have a huge library of Jupiter photos, video, and data.
Juno does own some firsts, however. It’s the fastest thing man has ever sent into space, doing 165,000 mph as it approached, and requiring a 30-minute main engine burn to slow down to orbit velocity. It’s the first to take up a polar 107-day orbit where it will see spectacular auroras in detail, and it’s the first to build a global map of the planet’s gigantic gravitational and magnetic fields. Its trio of 29-foot-long solar arrays that provide electrical power for its nine different instruments are the first to be used in such a way so far from our star, where sunlight is only four percent as bright as on Earth. It’s built to withstand the intense radiation of a magnetosphere thousands of times more powerful than ours for as long as possible—an environment so harsh the visible light camera onboard is expected to fail within only eight orbits, and its radiometer will be fried within 11 orbits. Juno will look for water and liquid metallic hydrogen, and study its fierce winds and the distribution of its mass and its high-energy hydrogen, helium, oxygen, and sulphur.
Fifth planet from the sun at 484 million miles out (we’re 94 million miles out), this one was named after the god Jupiter, king of the Roman pantheon, a notorious seducer of mortal mistresses, who often cloaked himself in clouds to hide his indiscretions from his wife, Juno.
But now Juno will have her way. At the end of her 20-month mission of intense scrutiny, she will dive deep into his raging storms, crushing pressures, and furious temperatures, seeking to detect the true heart of this by far most muscular planet in our solar system, and perhaps even learn how he came to be.