By observing different stars, we have learnt a lot about their lives- how they are formed, how they evolve and how they decay. Our Sun is typical of many stars in the Milky Way galaxy and other galaxies in the universe. We now believe that it formed approximately 4.6 billion years ago from a nebula, and most large objects in our solar system also formed from this nebula while others have been captured by Sun's gravitational pull when they came near the Sun's neighbourhood, extending to perhaps ~ 80 times the average distance between the Earth and the Sun. Many theories about the origin of the planets have been proposed and discarded or modified over the years as we learn about the planet formation processes, particularly from more detailed observations of the planets, particularly their atmospheric composition and interior structure from space missions.

Debates over the origin and early development of our solar system have reached an impasse. By far the largest of the planets, Jupiter holds answers to critical questions that will dramatically enhance present theories about the formation of the solar system. The primary scientific goal of the Juno mission is to significantly improve our understanding of Jupiter's formation, evolution and structure.

From its innovative elliptical orbit, the Juno spacecraft will investigate Jupiter's interior structure, deep atmosphere and magnetosphere. Juno instruments will measure the abundance of oxygen on the planet and monitor localized variations in concentrations of water and ammonia caused by meteorological factors. Juno will also investigate the convection that drives general circulation patterns in Jupiter's atmosphere. Juno builds on data from previous Jupiter missions by determining the higher harmonics of the planet's gravity field and the polar region of the magnetosphere. Taking advantage of its unique polar orbit, Juno will also explore the auroral zones and their magnetic coupling to the Jovian plasma environment and the planet's satellites.

The Juno spacecraft's suite of seven science instruments will:

Origins

Determine the ratio of oxygen to hydrogen, giving an idea of the abundance of water on Jupiter.

Obtain a better estimate of Jupiter's core mass, which will help distinguish among prevailing theories linking the gas giant's formation to the solar system.

Interior

Precisely map Jupiter's gravitational and magnetic fields to assess the distribution of mass in Jupiter's interior, including properties of the planet's structure and dynamics.

Atmosphere

Map the variation in atmospheric composition, temperature structure, cloud opacity and dynamics to depths far greater than 100 bars at all latitudes (In 1995, the Galileo probe reached only ~ 22 bars at a single location).

Magnetosphere

Characterize and explore the three dimensional structure of Jupiter's polar magnetosphere and its auroras.

The Juno mission will provide answers to science questions that are central to all of NASA's Science Themes: Earth-Sun System, Solar System, and the Universe. Achieving the Juno objectives will significantly advance our knowledge about Jupiter's true nature as well as our understanding of planets similar to Jupiter that orbit distant stars in other solar systems. The origins of life itself may have critical ties to the special conditions under which solar systems such as our own were born and evolved. Using data from this mission to Jupiter, scientists will come closer to understanding these conditions and their connections to the origins of the human race.

Beyond the project's science value, a camera called JunoCam will show us the regions of Jupiter as our instruments explore them and will be used by student participants in the Education and Public Outreach program to take the first color images of Jupiter's polar regions from the Juno spacecraft.