Juno On Its Way

NASA successfully launched its Juno spacecraft yesterday. In five years, if all goes well, Juno will reach Jupiter and insert itself into an elliptical polar orbit around the giant planet.

Juno is scheduled to spend one Earth year orbiting Jupiter and studying its internal structure, including its magnetic and gravitational fields. At the end of its mission, the probe will be deliberately crashed into the planet to preclude any possibility of it ever crashing into one of Jupiter's moons that might harbor life.

The decision to crash into the planet is curious. Surely there is an orbit it could be put in that would keep the probe away from the moons, and which would allow it to be retrieved at some point in the future. That would have historical and, presumably, scientific value. Beyond that, life somewhere in Jupiter's vast and complex atmosphere is not completely out of the question. So, mission planners are making the judgment that life on one of the moons is more likely than life in Jupiter's atmosphere. Whether we know enough yet about life, or the moons, or Jupiter itself is another matter.