Tinetti et al have a paper in Nature, July 12th, claiming infrared spectroscopic detection of water on an extrasolar planet.
Paper is there Water vapour in the atmosphere of a transiting extrasolar planet (pdf)
(here is Nature link)
Detection is by comparing broadband IRAC mid-infrared data from Spitzer with detailed atmospheric models.
Object is transiting hot Jovian HD189733b – Jupiter mass planet in 2 day orbit around a K dwarf about 60 lightyears away.
Claims is the absorption seen in mid-IR is only consistent with water vapour at about 0.05% in the upper atmosphere – they also note they get a slightly different radius in the IR than in the optical during transits – possibly due to high altitude clouds (transparent to IR but opaque in optical).
Claim robust detection of molecular species through spectroscopy.
Looks pretty good, I’m sure some people will work hard to see if there are alternative explanations.
There have been previous contested claims of water detection, this one pushes things further a bit, two separate issues: one is proof of concept that we can in fact do chemistry through absorption spectroscopy of extrasolar planets, rest is just engineering; and, there is water out there, as there should be.
Good solid science, pushing what is doable with current instruments that we should remember were not designed to do this science, it is serendipitous that this sort of data can be squeezed out of them since they were spec’d to do different but related science.