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Journey to the origin of the Solar System

Stellar predictions: Dr Andrew Prentice.
Photo: Greg Ford

A Monash University mathematician, regarded as one of the world's foremost experts on the formation of the Solar System, has surprised many in the interplanetary space exploration world with the remarkable accuracy of his predictions, as recent NASA missions have borne out. KAREN STICHTENOTH reports.

Planetary mathematician Dr Andrew Prentice has found widespread acclaim following the success of his many key predictions about the physical and chemical structure of the Solar System.

These predictions are linked to his Modern Laplacian theory of how the Solar System was formed some 4.5 billion years ago. The controversial theory, first presented by Dr Prentice in 1976, is based on a hypothesis advanced by French mathematician Pierre de Laplace in 1796.

Dr Prentice's Laplacian theory proposes that when the Sun first formed, it was a huge swirling cloud of gas and dust. When this cloud contracted inwards to form the present Sun, it cast off a concentric family of orbiting gas rings. The planets later condensed from these rings, starting with Neptune and finishing with Mercury. For the Sun to shed gas rings, Dr Prentice introduced a new physical concept of 'supersonic turbulence'. It is this phenomenon that causes the primitive Sun to shed individual gas rings, one at the orbit of each planet.

A reader in mathematics at Monash University's School of Mathematical Sciences, Dr Prentice is also a high-profile member of Monash's Centre for Stellar and Planetary Astrophysics, which provides a focus for research within the Australian astronomical community.

His academic career has paralleled NASA's program of unmanned interplanetary space exploration. After completing a doctorate in theoretical astrophysics at Oxford University, he commenced as a lecturer at Monash in March 1972 -- the same month that NASA launched its first unmanned space probe, Pioneer 10, to the outer planets.

By 1989, NASA's Voyager 2 spacecraft had confirmed the existence of a previously unknown family of moons in orbit about Neptune, whose location and number had been accurately predicted by Dr Prentice.

As the only Australian scientist involved with NASA's recent Galileo mission to Jupiter, Dr Prentice made headlines again when many of his mathematical predictions about that planet were confirmed.

The 14-year mission ended in September 2003, but not before Jupiter's outermost Galilean satellite, Callisto, was confirmed as a cold, magnetically inert body of rock and ice, and the smallest Galilean moon, Europa, was found to have a 150-kilometre deep mantle of ice, both of which Dr Prentice had predicted. The sulphur content of Jupiter's atmosphere was also found to have exactly matched Dr Prentice's prediction.

The mission also proved Dr Prentice's 25-year old theory that Jupiter's fifth largest moon, Amalthea, discovered in 1892, was actually a 'captured' asteroid and not a native satellite or moon of Jupiter. "The real test of my work over the next few years, however, will be the Saturnian system," he says.

"According to my theory, this complex system should prove to be a miniature planetary system that was created in the same way as the Galilean moons were formed from Jupiter and the planets were spawned from the Sun."

Dr Prentice is currently at NASA's Jet Propulsion Laboratory in Pasadena, California, where he is fine-tuning his predictions for Saturn and its mysterious family of icy moons, prior to the arrival of the Cassini-Huygens spacecraft on 1 July.

A highlight of this new spacecraft mission will be the arrival of the Huygens probe at Saturn's largest moon, Titan, on 14 January 2005. This probe is to descend through Titan's cloudy atmosphere to the unknown surface below. In 1980, Dr Prentice predicted that Titan was not a native moon of Saturn but instead had been captured soon after Saturn had formed. He has also made a prediction for the chemical structure and density of Saturn's outermost moon, Phoebe. This prediction will be tested on 11 June this year, just before Cassini arrives at Saturn.

"It would be nice, after all this time, if the Cassini-Huygens mission confirms many of the predictions of my theory for Saturn," he says. "In the long run, the only real test of any theory is its ability to make successful predictions."

Dr Prentice's retirement in 2008 will coincide with the end of the Saturn project, but he expects to remain busy for much longer through his involvement with NASA's future explorations to Mercury and Mars.

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For further information, contact Dr Andrew Prentice at andrew.prentice@sci.monash.edu.au. For more information, visit the Monash Centre for Stellar and Planetary Astrophysics website.