A piece in yesterday’s online edition of The Times, much longer than the piece in the print edition:
It is a scientific discovery that will delight young schoolchildren and adults who have not lost their playground humour: Uranus is smelly.
Researchers at Oxford University have discovered that the ice giant is wreathed in clouds of hydrogen sulphide, the chemical that gives gone-off eggs their characteristic pungency, beneath a dusting of methane. It is, in other words, not all that dissimilar to the air in a Texan pork ‘n’ beans restaurant on a Saturday night.
Although Uranus was first recognised as a planet in 1781, by the German-British astronomer William Herschel, the contents of its atmosphere are still largely obscure.
The only space probe to have been anywhere near the seventh planet from the Sun was Voyager 2, which swooped past in 1986.
Earth-based telescopes struggle to penetrate much beyond 200 miles into its atmosphere, which is mostly made up of hydrogen and helium, the two lightest and simplest elements in the periodic table.
The thin outermost layer of cloud contains methane, which is thought to give the planet its pale aquamarine hue.
Beneath it, at relatively gentle pressures between 1.2 and 3 bar — very approximately the range of pressures found between sea level and a depth of 20m or so below the surface — is another cloud whose chemistry is more controversial.
Up to now, many planetary scientists have argued that it is predominantly made up of ammonia, a compound of nitrogen and hydrogen, much like its counterparts on Jupiter and Saturn.
However, observations led by Patrick Irwin, professor of planetary physics at Oxford, show “conclusively” that it is in fact primarily made up of hydrogen sulphide, most of which is probably locked up in ices.
The findings, published in the journal Nature Astronomy, come from an analysis of the near-infrared microwaves detected by a spectrometer instrument at the Gemini-North telescope in Hawaii.
However much sniggering it may prompt at the back of the class, the research makes a serious point about the genesis of the solar system.
Writing in the same journal, Imke de Pater, professor of astronomy at the University of California, Berkeley, said it had revealed an instructive difference between Uranus and the two gas giants.
The planets formed from a vast, swirling disk of dust and gas around the Sun some 4.5 billion years ago. The fact that the outer Uranian atmosphere seems to be comparatively rich in sulphur rather than nitrogen suggests that the planet may have been born under conditions that were quite different to those in the neighbourhood of Saturn and Jupiter.
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