Ever since the invention of the telescope 400 years ago, astronomers have been
studying Jupiter. Who could resist? It's such a big, bright target in the night
sky. Just one problem: It's tough to "get to the bottom" of a planet that's
For four long centuries the gas giant's vast interior has remained hidden from
view. NASA's Juno probe, scheduled to launch on August 5th, could change all
that. The goal of the mission is to answer the question, What lies inside
"Our knowledge of Jupiter is truly skin deep," says Scott Bolton of the
SouthWest Research Institute in San Antonio, TX. Bolton is Juno's principal
investigator. "Even the Galileo probe, which dived into the clouds in 1995,
penetrated no more than about 0.2% of Jupiter's radius."
There are many basic things researchers would like to know, like how far down
does the Great Red Spot go? And what is the exotic material that lies at
Juno will improve the situation without actually diving into the clouds. Bolton
explains how: "Swooping as low as 5000 km above the cloudtops, Juno will spend a
full year orbiting nearer to Jupiter than any previous spacecraft. The probe's
flight path will cover all latitudes and longitudes, allowing us to fully map
Jupiter's gravitational field and figure out how the interior is structured."
Jupiter's interior is a place of great interest. The planet is made primarily of
hydrogen gas. Deep inside Jupiter, however, high temperatures and crushing
pressures transform the gas into an exotic form of matter known as liquid
metallic hydrogen. It is what it sounds like: a liquid form of hydrogen akin to
the slippery mercury in an old-fashioned thermometer. Jupiter's powerful
magnetic field almost certainly springs from dynamo action inside this vast
realm of electrically conducting fluid.
"Juno's magnetometers will precisely map Jupiter's magnetic field," says Bolton.
"This will tell us a great deal about Jupiter's inner magnetic dynamo - what
it's made of and how it works."
Juno will also probe Jupiter's atmosphere using a set of microwave radiometers.
"Our sensors can measure the temperature and water content at depths where the
pressure is 50 times greater than what the Galileo probe experienced," says
Researchers will use that information to understand the deep structure of the
atmosphere and unravel some of the mysteries of Jupiter's monster storms.
Finally, Juno will get a grand view of the most powerful Northern Lights in the
"Juno's polar orbit is ideal for studying Jupiter's auroras," explains Bolton.
"Unlike Earth, which lights up in response to solar activity, Jupiter makes its
own auroras. They are really strong, and we don't fully understand how they are
Juno's sensors might solve the mystery - a beautiful bonus.
For updates about the Juno mission and more information about cloudy planets
everywhere, please stay tuned to science.nasa.gov