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Hunting for Molecules on Faraway Planets
02.21.07
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Narrator: Hunting for molecules on faraway planets. I'm Jane Platt with a podcast from JPL -- NASA's Jet Propulsion Laboratory in Pasadena, California. A first from the Spitzer Space Telescope. Its powerful instruments have split apart and analyzed the very faint light from two distant gas planets, way beyond our solar system, to look for molecules. What's the big deal about this?
Swain: Oh, we're studying weather on another world, and this is a stepping stone to eventually studying signs of life on worlds where life could exist, the habitable worlds which we're hoping to discover in the near future.
Narrator: Dr. Mark R. Swain is a JPL research scientist. He and his colleagues form one of three teams with similar discoveries, a couple of them being published in science journals. The discoveries come as a surprise bonus for the Spitzer team.
Swain: We're using Spitzer well beyond the original engineering design. So this is a real testament to the quality of the design that originally went into the spacecraft that it's able to do this at all. This was a complete surprise and well outside the design criteria.
Narrator: They were able to do it, thanks to Spitzer's onboard spectrograph instrument. Dr. Carl Grillmair of the Spitzer Science Center at Caltech heads one of the three science teams.
Grillmair: We take the light, and we spread it into its component colors as finely as we possibly can. So if we took a rainbow, for example, we would spread it across a football field and then look in detail with a magnifying glass at every individual color in that rainbow.
Narrator: Specific patterns within the light indicate the presence of certain chemical molecules. The two planets Spitzer studied – HD 209458b and HD 189733b -- revealed some surprises.
Grillmair: We had definite ideas about what we expected to see based on modeling and theoretical supercomputer work that many people have done. It was believed to be fairly straightforward that these planets would have a lot of water in them, for one thing, very hot water. These planets, these hot Jupiters very, very close in to their parent stars are 2,000 degrees Fahrenheit or so, so it's not a pleasant place to live. And what we found instead and what the other group found for this completely different planet around another star, is that the spectrum is essentially flat. It really doesn’t show any of the features we would have expected from water.
Narrator: So none of the researchers found evidence of water molecules in the planets' atmospheres, although the water could be hidden beneath clouds. The team led by Dr. Jeremy Richardson of NASA's Goddard Space Flight Center in Maryland did find something intriguing in the atmosphere of one planet.
Richardson: We identified at least one molecule in the spectrum. And there was a feature that we saw in the spectrum that is probably due to silicate emission, and silicates are like molecules that have silicate and oxygen and typically some other metal in them. And what that means is that there's likely a cloud that's pretty high in the atmosphere that could be made of these silicate grains, basically dust grains,
Narrator: The scientists hope to use Spitzer to learn more about these alien atmospheres. Mark Swain.
Swain: What is exciting is that by studying the clouds, assuming that’s what this signature that we're seeing means, if that interpretation holds up, we're also going to have to start studying, how did the clouds get there? What sustains them? What are the creation and destruction mechanisms? And by doing that we'll be studying all sorts of processes, convective processes in the planet's atmosphere, transport, how you move heat around from the hot side to the cold side. All those processes are very important on a world that is at a temperature where life could exist. How do you create weather on those worlds? Does that impact the ability of life to survive?
Narrator: Scientists believe life as we know it could not exist on the worlds studied by Spitzer -- huge, hot planets really close to their suns. The task of studying smaller, more Earthlike planets believed to be more likely locations for life-- will fall to future space missions.
Grillmair: I think everything is a little bit unsettled now. The observations are showing us that things are not the way we expected them. And so there'll be a big push to get a lot more data while Spitzer is still alive. I think this will ultimately be one of the most important legacies of the Spitzer Space Telescope, unanticipated as it was before launch. I think it will become extremely important in the future.
Narrator: More info on the Spitzer Space Telescope is online at www.nasa.gov/spitzer and www.spitzer.caltech.edu . Thanks for joining us for this podcast from NASA's Jet Propulsion Laboratory.
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Vue d'artiste

Le télescope spatial Spitzer de la NASA a fait sensation cette semaine lorsqu'il a été annoncé que l'observatoire spatial a, pour la première fois, capté assez de lumière pour détecter des molécules dans les atmosphères d' exoplanètes.

Les planètes sont trop lointaines pour être observées directement avec la technologie actuelle, mais la mesure du spectre de chaque planète lorsqu'elle est visible avec son étoile puis lorsqu'elle est cachée par son étoile permet aux équipes d'astronomes de pouvoir effectuer des mesures à partir du spectre calculé.

Dans un article publié dans l'édition du 22 février de la revue Nature, le dr. Jeremy Richardson du Goddard Space Flight Center de la NASA présente les mesures sur HD 209458 b, une planète chaude de type Jupiter à 153 années-lumière de la Terre, dans la constellation de Pégase. L'équipe de Richardson a dobservé un pic dans le spectre infrarouge et a été en mesure d'affirmer que l'atmosphère de l'exoplanète HD 209458 b se composait apparement de nuages de poussière de silicates. Le dr. Mark Swain du Jet Propulsion Laboratory a conduit une autre étude sur la même exoplanète et est parvenu aux mêmes conclusions.

Une autre équipe, dirigée par le dr. Carl Grillmair du spitzer Science Center de Caltech, a mené une étude similaire sur HD 189733b, distante de 63 années-lumière, dans la constellation Vulpecula. Le dr. Grillmair a commenté les résultats : 

, a ajouté le dr. Richardson. 

Dr. Grillmair :  Le télescope a été lancé en août 2003 avec une durée de vie maximale attendue de 5 ans.

 indique Swain. .

Les études respectives des drs Swain et Grillmair sont en attente de publication dans Astrophysical Journal Letters.