Nasa’s Juno mission is spending its first week in orbit around Jupiter. This giant planet is more than 11 times the diameter of Earth.
Having travelled for more than 1.7bn miles through the solar system, Juno was captured by Jupiter’s gravity at 03:18 GMT on 5 July after an engine burn that lasted 35 minutes.
It is now in a highly elliptical orbit around the giant planet, taking 53.5 days to complete a circuit. It will stay in this “capture orbit” until October, when another engine firing will reduce the size to a 14-day orbit.
This will signal the start of the science phase. Juno carries nine science instruments and will investigate how the giant planet formed 4.6bn years ago. It will do this by skimming the cloud tops every orbit to measure the distribution of matter inside the planet. Different formation scenarios predict different distributions.
There are 32 science orbits that the spacecraft will complete during the course of the next 18 months. Then the mission will come to a scheduled end in 2018.
To comply with Nasa’s planetary protection guidelines, the spacecraft will be guided into Jupiter’s atmosphere. It will enter and burn up on 20 February 2018. This is to safeguard against leaving it in orbit where it could collide with one of Jupiter’s moons Europa, Ganymede or Callisto.
These moons are thought to possess liquid water beneath their surfaces, and so have the potential (however unlikely) to host life. Thus, they must not be contaminated with anything from Earth.
