Posted: 02 December, 2008
The first mission that will place a spacecraft in a highly elliptical polar orbit around Jupiter, Juno will help scientists to understand the giant planet’s formation, evolution and structure.
Jupiter is enshrouded in dense clouds that scientists believe are safeguarding secrets to the fundamental processes and conditions that governed our early Solar System. The giant planet is similar to the Sun in that it is composed mostly of hydrogen and helium, but containing a larger percentage of heavier elements. "Jupiter is the archetype of giant planets in our Solar System and formed very early, capturing most of the material left after the Sun formed," says Scott Bolton, Juno principal investigator from the Southwest Research Institute in San Antonio. "Unlike Earth, Jupiter's giant mass allowed it to hold onto its original composition, providing us with a way of tracing our Solar System's history."
Juno's colour camera will reveal the details of Jupiter's poles. This UV image was taken with Hubble and shows bright emissions similar to the aurora observed at the poles of other planets. Image: NASA/ESA/Hubble Heritage Team/John Clarke (University of Michigan).
The mission will see Juno orbit Jupiter 32 times in one year, skimming 4,800 kilometres above the planet’s cloud tops. A huge technological challenge has been in designing the spacecraft to operate by solar power, despite being five times further from the Sun than the Earth. As a result, Juno is one of the biggest spacecraft ever built, with three 2 x 9 metre solar panels. End to end, the spacecraft and panels cover a circle of diameter 20 metres, and at the end of one solar panel a magnetometer – which will measure the magnitude and direction of the magnetic field around Jupiter – extends a further two metres.
The spacecraft’s camera and suite of science instruments will probe the hidden world beneath Jupiter's colourful clouds. They will investigate the existence of an ice-rock core, the planet’s intense magnetic field, water and ammonia clouds in the deep atmosphere, the dynamics of the atmosphere and the nature of Jupiter's aurora borealis. "In Greek and Roman mythology, Jupiter's wife Juno peered through Jupiter's veil of clouds to watch over her husband's mischief," says Professor Toby Owen, co-investigator at the University of Hawaii. "Our Juno looks through Jupiter's clouds to see what the planet is up to, not seeking signs of misbehavior, but searching for whispers of water, the ultimate essence of life."
By accurately determining the gravity and the magnetic fields of Jupiter, scientists will be able to test theories about the processes that operate within the planet’s interior. Under great pressure in the Jovian interior, hydrogen gas is squeezed into a fluid known as metallic hydrogen, which acts like an electrically conducting metal believed to be the source of the planet's intense magnetic field. Jupiter may also have a solid rocky core, and just last week research was presented suggesting that Jupiter’s core is actually twice the size than older models suggest. (You can read Astronomy Now's report here). Juno will be able to shed light on this and other predictions.
As well as studying the global dynamics of Jupiter's atmosphere, Juno will peer deep inside the giant planet for clues on its formation and evolution that will add pieces to the puzzle of Solar System formation. Image: NASA/ESA.
"Juno gives us a fantastic opportunity to get a picture of the
The spacecraft is scheduled to launch aboard an Atlas rocket from Cape Canaveral in August 2011, reaching Jupiter five years later, shortly after the New Horizons mission reaches the Pluto system. Both Juno and New Horizons are designed under NASA's New Frontiers Program.