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.
