For the next bold step to robotically explore the solar system, NASA has chosen a heavily instrumented probe to orbit Jupiter's poles over an ambitious mission to return samples from the Moon's mysterious south pole.

The Juno mission, as it is known, will launch by mid-2010 to begin its journey to Jupiter to conduct in-depth studies of the gas giant's extensive magnetic field, thick atmosphere, and the potential of a dense rocky core. Juno will help scientists build upon earlier findings from NASA's Galileo probe to determine how giant planets form and operate.

"We are excited at the prospect of the new scientific understanding and discoveries by Juno in our continuing exploration of the outer reaches of our solar system during the next decade," said Dr. Ghassem Asrar, NASA's deputy associate administrator for the agency's Science Mission Directorate.

Juno's science payload of seven instruments will be managed by principal investigator Dr. Scott Bolton of the Southwest Research Institute of San Antonio. Lockheed Martin Space Systems in Denver will be the prime contractor, while NASA's Jet Propulsion Laboratory in Pasadena, California, will host mission operations and project management officials.

"We're enormously pleased to be working with the Southwest Research Institute and the Jet Propulsion Laboratory to move this mission forward from the drawing board to the outer solar system," said Jim Crocker, Lockheed Martin Space Systems' vice president of Civil Space.

For the first time, instruments will peer down through Jupiter's opaque cloud tops to not only confirm the existence of a rocky center, but also to measure the planet's internal convection at exceedingly high atmospheric pressures deep below the visible surface. Juno also aims to detect the amount of water, ammonia, and methane in Jupiter.

Scientists also plan to learn more about the temperatures and wind velocities at different levels in the Jovian atmosphere, and to further characterize the planet's huge magnetosphere that traps harsh radiation that could pose dangers to future spacecraft.

Powered by solar energy, Juno is planned to orbit Jupiter for a prime mission of one year on a trajectory to avoid much of the harsh radiation that surrounds the Jovian system. This issue often plagued NASA's Galileo probe, which orbited Jupiter from 1995 until 2003.

But first, however, Juno must undergo preliminary design followed by a review before being formally approved for the development of mission hardware and systems.

The preliminary design review will ensure there are no significant outstanding technical, cost, or schedule risks before pouring money into the expensive construction of the spacecraft and mission operations.

Under constraints set by NASA, Juno must be launched by the end of June 2010, and costs must be kept below a maximum of $700 million including launch services.

Juno was one of seven proposals first submitted to NASA in February 2004 after the agency issued an Announcement of Opportunity for the next New Frontiers mission in 2003. Officials then down-selected to two mission concepts, including Juno and a mission called "Moonrise."

Moonrise would have sent a pair of identical landers to the Aitken basin region near the south pole on the far side of the Moon. The two craft were to have scooped up to five pounds of surface material for return to Earth to analyze its composition and compare that data to other samples brought back during the Apollo landings.

Soils located on in the Aitken basin are believed to be unspoiled remnants of the early lunar mantle and crust and could tell scientists more about the history of the Earth-Moon system.

Moonrise and Juno each received about $1 million in funds to complete seven-month feasibility studies that were due in March. Juno was then selected after a careful two-month review.

"This was a very tough decision given the exciting and innovative nature of the two missions," Asrar said.

Juno is the second mission chosen under NASA's newly-created New Frontiers program, which aims to mount medium-class missions to study prioritized objectives as deemed by the Space Studies Board of the National Research Council.

The board releases the Decadal Solar System Exploration Survey, which outlines a strategy for the next generation of robotic probes to travel to destinations throughout the solar system. The most recent publication included the Juno and Moonrise missions, in addition to a Venus orbiter with a possible lander and a comet surface sample return mission.

The New Frontiers program will be kicked off next January when NASA plans to launch its first member -- the New Horizons probe -- to embark on a 9-year journey to the far reaches of the solar system. The mission will make a fly-by of Pluto and its moon Charon, returning the first detailed images of the distant system. New Horizons will then possibly target multiple Kuiper Belt Objects -- shady primitive iceballs that are likely the source of short-period comets.