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Juno mission graphic

Phase: Operating

Launch Date: August 05, 2011

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Program(s):New Frontiers

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The primary scientific goal of the Juno mission is to significantly improve our understanding of the formation, evolution and structure of Jupiter. Concealed beneath a dense cover of clouds, Jupiter, the archetypical "Giant Planet," safeguards secrets to the fundamental processes underlying the early formation of our solar system. Present theories of the origin and early evolution of our solar system are currently at an impasse. Juno will provide answers to critical science questions about Jupiter, as well as key information that will dramatically enhance present theories about the early formation of our own solar system.

Juno - View from Cassini of Jupiter's North Poles

Juno is carrying a color camera to give the public its first detailed look at Jupiter’s poles. This distant image was captured by NASA’s Cassini spacecraft, which visited the giant planet in 2000 on its way to Saturn.
Credit: NASA/JPL/University of Arizona

In 2016, the spinning, solar-powered Juno spacecraft will reach Jupiter and enter into a highly elliptical polar orbit that skims only 5000 kilometers above the planet's atmosphere. Building on the results of previous missions, Juno will provide new information to help us determine how, when and where this giant planet formed. Answering these questions for Jupiter is essential for an understanding of the origin of the solar system itself because Jupiter contains more mass than all the other planets combined. Juno will seek these answers with instruments that can sense the hidden world beneath Jupiter's colorful clouds while other experiments investigate the external effects that world produces.

Jupiter has no solid surface. Instead its hydrogen and helium dominated atmosphere grows steadily denser with depth. Ultimately, but we don't know exactly where, the atmosphere must become a fluid in which hydrogen acts like an electrically conducting metal. Still deeper there may be a core of heavy elements and somewhere, somehow, an intense magnetic field is generated. The invisible external tendrils of that field guide charged particles that crash into the polar ionospheres, producing the most intense auroras (the northern and southern "lights") in the solar system. Juno will study these and other characteristics that make Jupiter one of the most fascinating planets in the solar system.

To answer our fundamental questions about origins we especially need to know Jupiter's internal structure and global water abundance. Juno will map the internal structure by studying its influence on the planet's gravitational field with unprecedented accuracy. The water abundance will be determined by microwave radiometers that will detect thermal radiation from deep atmospheric layers, a completely new approach. Water ice brought most of the heavy elements to Jupiter. Knowing the water abundance will tell us the original form of that ice and hence help define the conditions and processes in the original cloud of dust and gas that led to the origin of Jupiter. Those same conditions and processes were forming other planets too. Because this enormous planet contains most of the water in the solar system we can expect this investigation to help us understand the origin of the life-giving water on Earth.

The launch of the Juno mission in August 2011 began a five-year journey to Jupiter, to investigate the remaining unanswered questions beneath the surface of the mysterious gas giant.