MILWAUKEE – On a clear August day in 2011, NASA launched a cube perched atop an Atlas V rocket that unfurled into a probe the size of a basketball court, complete with three whirling solar arrays.
That probe, named Juno in honor of the Roman god Jupiter’s wife, embarked on the first mission to map the mysterious inner workings of the largest planet in our solar system. The extraordinary five-year journey involved a push through the inner solar system, a slingshot around the sun, a flyby of Earth and ultimately a capture by Jupiter’s gravity.
When Juno fires its main engines July 4, the journey will end as it slips into orbit above Jupiter. But the mission to explore what lies beneath the swirling clouds of gas will have just begun.
Excitement about the mission has been building in the scientific community – NASA’s website already has a countdown – and is just now spreading to the general public. The Independence Day firing is critical; a reverse thrust generated during the burn will essentially slam on the brakes so that the probe can skim over Jupiter and into a stable orbit. NASA expects to receive confirmation of the start of Juno’s engine burn at 11:18 p.m. EDT and should know whether it worked by 11:53 p.m.
With its enormous magnetic field, Jupiter creates one of the brightest auroras ever observed despite being composed mostly of ammonia, hydrogen and helium. In some respects, Jupiter and its dozens of circling moons functions as almost a miniature solar system. Some astronomers even consider Jupiter a failed star.
Juno will be the first spacecraft to complete its orbits over Jupiter’s poles. Here it will escape the brunt of the planet’s intense radiation and provide the first data from the uncharted regions from which the magnetic field emanates.
“Juno will go where no spacecraft has gone before – deep into the harshest radiation environment in the solar system outside the sun,” Rick Nybakken, Juno Project Manager from NASA’s Jet Propulsion Laboratory, explained during a recent news conference.
In an effort to prolong Juno’s survival, NASA housed the probe’s sensitive equipment in a 1½-inch-thick titanium vault that cuts the radiation exposure by 800-fold.
Scott Bolton, Juno’s principal investigator, described the incredible efforts to ensure mission success. “Jupiter is the most extreme planet we have, and we are going right next to it. It’s got to do the extreme.”
Incredibly high pressures and temperatures within Jupiter make the elements inside do some physically weird things. Specifically, scientists think the brutal conditions inside Jupiter force hydrogen into a fluid state, called “metallic hydrogen,” which is capable of conducting electricity.
By studying the charged particles and gravitational pull in the upper atmosphere, NASA will be able to determine whether metallic hydrogen is responsible for Jupiter’s powerful magnetic field. It should also reveal how deep the planet’s characteristic orange and white bands extend and if a solid core might be hidden at the center.
Moreover, scientists expect data from Juno to answer key questions about planetary formation and the origins of our solar system. Because Jupiter has a large mass, it has absorbed countless impacts from asteroids and comets unscathed and has retained the most intact material since the birth of the sun.
Each orbit will take 11 days, with Juno tracking different paths across Jupiter with its instruments and camera, JunoCam. Because Jupiter will also be rotating on its own axis, the entire planet will be surveyed inside and out by the end of the 37 planned orbits.