Close Encounters with Jupiter
Wednesday, October 20 2010 @ 05:40 pm EDT
Contributed by: dgrosvold
by Dr. Tony Phillips
Jupiter and Earth just had a close encounter — and it was a good one. In late September 2010, the two worlds were 31 million km (about 19 million miles) closer than at any time in the past 11 years. Soaring high in the midnight sky, Jupiter shone six times brighter than Sirius and looked absolutely dynamite through a backyard telescope.
Planetary scientist Scott Bolton of the Southwest Research Institute isnít satisfied. “Iíd like to get even closer,” he says.
|The Juno mission, arriving at Jupiter in July 2016, will help to solve the mystery of whatís inside the giant planetís core.
Click image for larger view
Bolton will get his wish in July 2016. Thatís when a NASA spacecraft named “Juno” arrives at Jupiter for a truly close-up look at the giant planet. Swooping as low as 5,000 km (about 3,000 miles) above the cloud tops, Juno will spend a full year orbiting nearer to Jupiter than any previous spacecraft.
The goal of the mission is to learn what lies inside the planet.
Astronomers have been studying Jupiter since the invention of the telescope 400 years ago, but in all that time the planetís vast interior has remained hidden from view. Even the Galileo probe, which dived into the clouds in 1995, penetrated no more than about 0.1% of Jupiterís radius.
“Our knowledge of Jupiter is truly skin deep,” says Bolton, Junoís principal investigator. “There are many basic things we just donít know — like how far down does the Great Red Spot go? And does Jupiter have a heavy core?”
Juno will improve the situation without actually diving into the clouds. Bolton explains how. “Juno will spend a full year in close polar orbit around Jupiter, flying over all latitudes and longitudes. We will thus be able to fully map Jupiterís gravitational field and figure out how the interior is structured.”
But thatís not all. Researchers have good reason to believe that much of Jupiterís interior is filled with liquid metallic hydrogen, an exotic metal that could form only in the high-pressure, hydrogen-rich core of a giant planet. Jupiterís powerful magnetic field almost certainly springs from dynamo action inside this vast realm of electrically conducting metal.
“Junoís magnetometers will precisely map Jupiterís magnetic field,” says Bolton. “This map will tell us a great deal about planetís inner magnetic dynamoówhat itís made of and how it works.”
Finally, Juno will probe Jupiterís atmosphere using a set of microwave radiometers. “Our sensors can measure the temperature 50 times deeper than ever before,” says Bolton. Researchers will use that information to figure out how much water is underneath Jupiterís clouds. “Microwave measurements of Jupiterís water content are particularly exciting because they will help discriminate among competing theories of the planetís origin.”
Now thatís a close encounter. Stay tuned for Juno.
Find out more about the Juno mission at http://www.nasa.gov/mission_pages/juno. Play the new Solar System Explorer super game, which includes the Juno Recall mini-game at http://spaceplace.nasa.gov/en/kids/solar-system. Itís not just for kids!
This article was provided courtesy of the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.