Beyond Mars: Exploring the Realm of the Giants

Tuesday 19th August, 2014

Our speaker was Dr Leigh Fletcher from the University of Oxford who came to talk to us about "Exploring the Realm of the Giants". He currently works for the European Space Agency (ESA) as a Study Support Scientist working on the "JUICE" mission to Jupiter and its moons; the acronym is short for Jupiter Icy Moons Explorer.

Dr Fletcher is also a Royal Society Research Fellow and so is funded by the Royal Society and he explained this meant he had a light teaching schedule leaving him free to concentrate on pure research. He started off as a meteorologist but his academic studies have led him into the climatology and weather of the outer giant planets of our Solar System.

He began his talk by saying that the giant planets (Jupiter, Saturn, Uranus and Neptune) allow scientists like himself to study fluid dynamics on a large scale. For, all these outer planets lack an accessible solid surface but consist of mainly gases around an inner core buried deep within their atmospheres. Each is comparable to a miniature solar system and some of the moons may be suitable for extraterrestrial life.

Most of the knowledge about the giant planets has come from NASA's Voyager spacecraft but they only flew briefly past the planets. It is only by gathering data over time from an orbital spacecraft such as the Galileo or Cassini missions that scientists can solve certain mysteries. For example, it is still not understood why Jupiter's Great Red Spot is red. This giant storm has been swirling south of Jupiter's equator for at least 400 years and takes about six Earth days to rotate. You can fit about three Earth diameters across it from east to west but recently this dimension has been changing. At the beginning of 2004 it had shrunk in width to half that seen a century beforehand and if this continues by 2040 it would become a circular storm.

Other puzzles that Dr Fletcher would like to solve is why Uranus and Neptune have jetstreams flowing westwards whereas Jupiter's jetstream flows to the east. Also Neptune lies farthest from the Sun and yet it has the most active weather system with the fastest winds in the Solar System raging at 2,100 kph.

There are a number of upcoming missions that may help to answer some of these questions such as NASA's Juno spacecraft arriving at Jupiter in 2016. It will be the first craft to map Jupiter's poles and will also study Jupiter's magnetic and gravitational fields as well as determining the size of the planet's core. Interestingly, NASA will be relying on a worldwide network of amateur astronomers to take contemporary images of Jupiter as their spacecraft will be flying so close to the planet that it will not get an overall picture of its disc and the larger features it will be mapping.

The mission that Dr Fletcher is working will be arriving at Jupiter much later than Juno, in 2030. However it is planned to orbit for about three and a half years, which is roughly three times the mission lifetime of Juno. It will also perform in depth studies of the moons Europa and Ganymede.