Thursday, February 22, 2007

Life on other planets

A headline story in The Daily Telegraph by their Science editor, Roger Highfield, suggests that astronomers analysing the chemical makeup of the atmosphere of extrasolar planets, have found "tentative evidence that suggests the presence of chemicals which play a role in one theory of how life began on Earth." (;?xml=/news/2007/02/21/nalien121.xml).

The infrared spectra from two Jupiter-size planets, HD 209458b and HD 189733b, were analysed, and it is claimed that the spectrum obtained from the former included "an unidentified feature in the spectrum, a much sharper peak at a wavelength of around 7.78 micrometres, which is hard to identify but may correspond to polycyclic aromatic hyrocarbons."

Elsewhere, the findings of this research are described in quite different terms. Essentially, the scientists expected to find evidence of water, methane and carbon dioxide, and failed to detect any of these componds. According to an Associated Press article "The study of one planet found hints of fine silicate-particle clouds. Research on the other planet found no chemical fingerprints for any of the molecules scientists were seeking," ( Regarding the feature at 7.78 microns, the New Scientist account states that "They could not identify this with any known material, but they say they cannot not rule out that it is carbon-based," (

At the end of the Daily Telegraph article Hugh Jones, of the University of Hertfordshire, states that "From the description this is a ropey spectrum which they have explained by fitting ad hoc/uncertain models." Once more, this vindicates my Golden Rule for reading popular science articles in newspapers and magazines: read the final paragraphs first!

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