Research: Oxford has its eye on the heavens

Where did the solar system's planets come from? Simon Midgley talks to a professor who is helping to answer the big questions

Oxford University is playing a leading role in helping to explore the nature of our solar system. Its sub-department of atmospheric, oceanic and planetary physics is collaborating with scientists in Nasa, the European Space Agency, France, Russia, Italy, Canada and Finland in a series of experiments aboard various space probes.

The Galileo Orbiter, now orbiting Jupiter, is carrying a spectrometer - an instrument for measuring the atmosphere - designed by scientists in Oxford, France and California. This is streaming data back to earth over a distance of more than 500 million miles for analysis in Oxford and elsewhere.

Jupiter, an enormous ball of gas, is roughly 1,000 times larger than Earth and swathed in colourful clouds. It experiences huge cyclonic and anticyclonic eddies, the equivalent of the lows and highs of our terrestrial weather maps but larger than the whole Earth and lasting hundreds of years.

The moisture on the plant is ammonia, the clouds coloured compounds containing sulphur and phosphorus, and the air mainly hydrogen and helium.

In December, Nasa will be launching the Surveyor 98 mission to Mars with an Oxford-designed pressure modulator infrared radiometer aboard. This instrument measures the temperature and structure of the atmosphere. It will send back data on the planet's climate, measuring the temperature, water vapour, clouds and wind-flow in the atmosphere. Evidence suggests that the atmosphere and climate of Mars was once very like the Earth's but underwent a dramatic change.

Professor Fred Taylor, head of the atmospheric department at Oxford, says: "The mission should tell us a lot about conditions on Mars, including the level of water in the atmosphere - a vital factor in determining the potential for life. The data may also have a bearing on climate change affecting the Earth."

The Mars Surveyor mission has involved rebuilding equipment destroyed when an earlier spacecraft, Mars Observer, was lost on the way to the planet in 1993. Oxford researchers helped to persuade Nasa to re-fly the mission.

In October last year the Cassini-Huygens spacecraft took off for a three- million kilometre, seven-year journey to Saturn. On board is an infrared spectrometer designed by the Oxford team and colleagues from Nasa. It will measure heat radiation from the atmosphere of Saturn and Titan, its largest moon, which is dispersed into its component wavelengths and analysed in terms of gases, ices and clouds, and solid material.

"Since of all the solar system Titan's atmosphere is most like that of the Earth's before life began, the information should also help us understand more about our weather and climate and issues like the greenhouse effect," says Prof Taylor.

Titan is bigger than the Earth's moon and has a higher surface pressure than our planet. Its atmosphere is mostly nitrogen like our own. Oily clouds, hydrogen cyanide and complex hydrocarbons have been identified in its atmosphere.

Prof Taylor's links with the mission began in 1988 following his work on the Galileo Mission to Jupiter. He was invited to join what he describes as "the huge and rigorous competition" to be part of the project.

Having been chosen ahead of a dozen or more competing bids and having secured the pounds 30.5m funding needed, he and his colleagues began designing, building and testing the spectrometer.

Planetary science is not a new subject to Oxford. It is in fact one of the oldest. Until quantum mechanics, relativity and cosmology arrived around 100 years ago, it was a pillar of natural philosophy.

Prof Taylor traces the history of modern planetary science to the early 18th century, when Edmund Halley was Savilian professor of geometry. Halley speculated widely on the nature of Earth's atmosphere, the oceans, planets and minor bodies of the solar system.

Prof Taylor is helping to plan the European Space Agency's Mars Express mission. He is proposing that one of his department's spectrometers should be part of its orbital mission. He is also working with a group of scientists in Finland on a plan to land one or perhaps more meteorological stations on Mars. The department is also collaborating with the Italians on the Rosetta Mission to send a spacecraft into a comet's atmosphere to take measurements. This will be launched in 2003.

Work is continuing at Oxford on building the seventh and largest of a series of earth-observing instruments, which dates back to 1969. It will be launched in 2002 on the spacecraft EOS, the Earth Observing System.

Data from an instrument on the upper atmosphere research satellite is still being analysed by the department. It is trying to understand the chemical and physical processes occurring in the ozone layer. Data from a joint Oxford/Russian instrument that went to Venus some years ago is also still being analysed.

Prof Taylor says one of the problems with this kind of research is that it is quite expensive and as much time is spent managing and financing his 80-strong department as on scientific research. His work is financed by funds from the university, the research councils and overseas research institutes with whom the department collaborates.

"We could not do it as a UK-only enterprise," he said "because we do not have a space programme in the UK other than as part of the European Space Agency. We have traditionally collaborated with the Americans, but we are increasingly collaborating as part of the European programme as it moves more and more into the sort of thing that we do."

For the future, Prof Taylor says that his department will continue to make observations of the Earth's atmosphere. He is interested in finding out what is happening to our climate and to the ozone layer. Can broad weather patterns be predicted for 10 years into the future, he asks. Can we predict the degree of global warming in, for example, 100 years time? He also asks whether physical models of Earth and its atmosphere can be unified so that the same approach is used to explain the observed behaviour of all planets.

Ultimately he is interested in where planets, especially the Earth, came from and how they evolved to be what they are now.