Nearly 200 scientists from 20 countries are in Hong Kong this week to try to answer one of the biggest questions of all time: How did life on Earth begin? They are taking part in a symposium organised by the International Astronomical Union (IAU) on the subject 'Organic Matter in Space - Quest for Life's Origins' at the University of Hong Kong. The five-day event began yesterday afternoon with a briefing hosted by IAU president Catherine Cesarsky, Nasa senior adviser for research and analysis Yvonne Pendleton, Nasa Ames Research Centre scientist Scott Sandford and HKU dean of science Sun Kwok. Professor Kwok said symposium debate would fall into three categories: the nature of organic compounds in stars; the observation of organic compounds in the solar system, including comets, asteroids, meteors and planetary dust; and laboratory studies. Dr Sandford said the age-old question of the origins of life had taken on a new scientific momentum following the mission of the Stardust spacecraft, launched in 1999, which had successfully captured complex organic material from comets. He said the debate on life's origins had intensified due to the complex nature of the material. 'It turns out that comet dust is not all the same,' he said. 'It's not generic, like oatmeal or something.' The evidence pointed to the universe being a much more volatile place than was generally thought. 'It's much more like a Saturday night than a Monday morning,' he said. Dr Cesarsky said it was a major success for Hong Kong to host an IAU symposium on such an important subject. 'We receive proposals and select the best from a scientific point of view. 'The competition is quite stiff. Everybody wants to have an IAU symposium. It's a sign of a high level of science.' Professor Kwok said the event was important for Hong Kong and HKU. 'This is a very high-profile event and a very competitive process. It's like bidding for the Olympics. It's a great honour that we were able to win this and that the president herself came here to open the meeting,' he said. The IAU - the official international body for astronomy - was the organisation that controversially stripped Pluto of its planetary status at its general meeting in Prague in 2006. Its next general meeting will be held in Rio de Janeiro next year, and the 2012 one will be in Beijing.