Air tests from planets upset astronomy theories

WASHINGTON – The first “sniffs of air” of two huge far-away planets reveal that they seem to be missing water, a surprising finding amid weather unlike that of any planets in our solar system with blast-furnace-like gusts and supersonic winds.

The absence of water from the atmosphere of both these Jupiter-sized gaseous bodies upsets one of the most basic assumptions of astronomy.

One of the researchers, Harvard University astronomy professor David Charbonneau, called the planets “very different beasts … unlike any other planets in the solar system.”

So far, scientists have found 213 planets outside our solar system – they are called exoplanets. But only eight or nine are in the right orbit and location for the type of study reported by three teams using NASA’s Spitzer Space Telescope.

The closest of the two planets studied, HD 189733b, is 360 trillion miles from Earth in the constellation Vulpecula. The other planet, HD 209458b, is about 900 trillion miles away in the constellation Pegasus and it has a strange cloud of fine silicate particles.

The two suns the planets orbit closely have hydrogen and oxygen, the stable building blocks of water. The planets’ atmospheres – examined for the first time using light spectra to determine the air’s chemical composition – are supposed to be made up of the same thing, good old H2O.

“We had expected this tremendous signature of water … and it wasn’t there,” said Carl Grillmair of the California Institute of Technology and Spitzer Science Center. He and Charbonneau studied the closer of the two planets, and their work is being published online in the Astrophysical Journal Letters.

Charbonneau said these surprising “sniffs of air from an alien world” tell astronomers not to be so Earth-centric in thinking about other planets. “We’re limited by our imagination in thinking about the different avenues that these atmospheres take place in,” he said.