title: Clouds in the atmosphere of the super-Earth exoplanet GJ 1214b.
abstract: Recent surveys have revealed that planets intermediate in size between Earth and Neptune ('super-Earths') are among the most common planets in the Galaxy. Atmospheric studies are the next step towards developing a comprehensive understanding of this new class of object. Much effort has been focused on using transmission spectroscopy to characterize the atmosphere of the super-Earth archetype GJ 1214b (refs 7 - 17), but previous observations did not have sufficient precision to distinguish between two interpretations for the atmosphere. The planet's atmosphere could be dominated by relatively heavy molecules, such as water (for example, a 100 per cent water vapour composition), or it could contain high-altitude clouds that obscure its lower layers. Here we report a measurement of the transmission spectrum of GJ 1214b at near-infrared wavelengths that definitively resolves this ambiguity. The data, obtained with the Hubble Space Telescope, are sufficiently precise to detect absorption features from a high mean-molecular-mass atmosphere. The observed spectrum, however, is featureless. We rule out cloud-free atmospheric models with compositions dominated by water, methane, carbon monoxide, nitrogen or carbon dioxide at greater than 5σ confidence. The planet's atmosphere must contain clouds to be consistent with the data.
authors.affiliation: Department of Astronomy and Astrophysics, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Laura
authors.initials: L
authors.lastname: Kreidberg
authors.affiliation: Department of Astronomy and Astrophysics, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Jacob L
authors.initials: JL
authors.lastname: Bean
authors.affiliation: 1] CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, Colorado 80309, USA [2] Department of Astronomy, California Institute of Technology, Pasadena, California 91101, USA.
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Désert
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Björn
authors.initials: B
authors.lastname: Benneke
authors.affiliation: Department of Astronomy, University of Maryland, College Park, Maryland 20742, USA.
authors.forename: Drake
authors.initials: D
authors.lastname: Deming
authors.affiliation: Department of Astronomy and Astrophysics, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Kevin B
authors.initials: KB
authors.lastname: Stevenson
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Sara
authors.initials: S
authors.lastname: Seager
authors.affiliation: 1] Department of Astronomy, Harvard University, Cambridge, Massachusetts 02138, USA [2] MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Zachory
authors.initials: Z
authors.lastname: Berta-Thompson
authors.affiliation: Department of Astronomy and Astrophysics, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Andreas
authors.initials: A
authors.lastname: Seifahrt
authors.affiliation: Centre de Recherche Astrophysique de Lyon, 69364 Lyon, France.
authors.forename: Derek
authors.initials: D
authors.lastname: Homeier