Water Vapor and Clouds on the Habitable-zone Sub-Neptune Exoplanet K2-18b

  title={Water Vapor and Clouds on the Habitable-zone Sub-Neptune Exoplanet K2-18b},
  author={Bj{\"o}rn Benneke and Ian Wong and Caroline Piaulet and Heather A. Knutson and Joshua D. Lothringer and Caroline V. Morley and Ian J. M. Crossfield and Peter Gao and Thomas P. Greene and Courtney D. Dressing and Diana Dragomir and Andrew W. Howard and Peter R. McCullough and Eliza M.-R. Kempton and Jonathan J. Fortney and Jonathan D. Fraine},
  journal={The Astrophysical Journal Letters},
Results from the Kepler mission indicate that the occurrence rate of small planets (<3 R⊕) in the habitable zone of nearby low-mass stars may be as high as 80%. Despite this abundance, probing the conditions and atmospheric properties on any habitable-zone planet is extremely difficult and has remained elusive to date. Here, we report the detection of water vapor and the likely presence of liquid and icy water clouds in the atmosphere of the 2.6 R⊕ habitable-zone planet K2-18b. The simultaneous… 

Can Carbon Fractionation Provide Evidence for Aerial Biospheres in the Atmospheres of Temperate Sub-Neptunes?

The search for signs of life on other worlds has largely focused on terrestrial planets. Recent work, however, argues that life could exist in the atmospheres of temperate sub-Neptunes. Here we

On the Effect of Stellar Activity on Low-resolution Transit Spectroscopy and the use of High Resolution as Mitigation

We present models designed to quantify the effects of stellar activity on exoplanet transit spectroscopy and atmospheric characterization at low (R = 100) and high (R = 100,000) spectral resolution.

Stellar Surface Inhomogeneities as a Potential Source of the Atmospheric Signal Detected in the K2-18b Transmission Spectrum

Transmission spectroscopy of transiting exoplanets is a proven technique that can yield information on the composition and structure of a planet’s atmosphere. However, transmission spectra may be

On the Temperature Profiles and Emission Spectra of Mini-Neptune Atmospheres

Atmospheric observations of mini-Neptunes orbiting M dwarfs are beginning to provide constraints on their chemical and thermal properties, while also providing clues about their interiors and

Consistently Simulating a Wide Range of Atmospheric Scenarios for K2-18b with a Flexible Radiative Transfer Module

The atmospheres of small, potentially rocky exoplanets are expected to cover a diverse range in composition and mass. Studying such objects therefore requires flexible and wide-ranging modeling

Mineral snowflakes on exoplanets and brown dwarfs

Exoplanet atmosphere characterisation has become an important tool in understanding exoplanet formation, evolution. However, clouds remain a key challenge for characterisation: upcoming space

Irradiated Ocean Planets Bridge Super-Earth and Sub-Neptune Populations

Small planets (∼1–3.9 ) constitute more than half of the inventory of the 4000-plus exoplanets discovered so far. Smaller planets are sufficiently dense to be rocky, but those with radii larger than

A Transmission Spectrum of the Sub-Earth Planet L98-59 b in 1.1–1.7 μm

With the increasing number of planets discovered by the Transit Exoplanet Survey Satellite, the atmospheric characterization of small exoplanets is accelerating. L98-59 is an M-dwarf hosting a

Detectability of biosignatures on LHS 1140 b

<p>Rocky extrasolar planets orbiting M dwarfs are prime targets in the search for habitable surface conditions and biosignatures with near-future telescopes like the James Webb Space Telescope (JWST)

Hubble WFC3 Spectroscopy of the Habitable-zone Super-Earth LHS 1140 b

Atmospheric characterization of temperate, rocky planets is the holy grail of exoplanet studies. These worlds are at the limits of our capabilities with current instrumentation in transmission



Water vapour in the atmosphere of the habitable-zone eight-Earth-mass planet K2-18 b

In the past decade, observations from space and the ground have found water to be the most abundant molecular species, after hydrogen, in the atmospheres of hot, gaseous extrasolar planets1–5. Being

A sub-Neptune exoplanet with a low-metallicity methane-depleted atmosphere and Mie-scattering clouds

With no analogues in the Solar System, the discovery of thousands of exoplanets with masses and radii intermediate between Earth and Neptune was one of the big surprises of exoplanet science. These


We use models of coupled thermal evolution and photo-evaporative mass loss to understand the formation and evolution of the Kepler-36 system. We show that the large contrast in mean planetary density

The California-Kepler Survey. VII. Precise Planet Radii Leveraging Gaia DR2 Reveal the Stellar Mass Dependence of the Planet Radius Gap

The distribution of planet sizes encodes details of planet formation and evolution. We present the most precise planet size distribution to date based on Gaia parallaxes, Kepler photometry, and

Confirmation of the radial velocity super-Earth K2-18c with HARPS and CARMENES

In an earlier campaign to characterize the mass of the transiting temperate super-Earth K2-18b with HARPS, a second, non-transiting planet was posited to exist in the system at ~9 days. Further

Handbook of Exoplanets

This state-of-the-art reference work includes over 15 sections dealing with all aspects of exoplanets and exobiology research, including historic aspects, the Solar System as a template, objects at

The CARMENES Search for Exoplanets around M Dwarfs: A Low-mass Planet in the Temperate Zone of the Nearby K2-18

K2-18 is a nearby M2.5 dwarf, located at 34 pc and hosting a transiting planet that was first discovered by the K2 mission and later confirmed with Spitzer Space Telescope observations. With a radius

The Transit Light Source Effect: False Spectral Features and Incorrect Densities for M-dwarf Transiting Planets

Transmission spectra are differential measurements that utilize stellar illumination to probe transiting exoplanet atmospheres. Any spectral difference between the illuminating light source and the

An HST/STIS Optical Transmission Spectrum of Warm Neptune GJ 436b

GJ 436b is a prime target for understanding warm Neptune exoplanet atmospheres and a target for multiple James Webb Space Telescope (JWST) Guaranteed Time Observation programs. Here, we report the

Ensemble samplers with affine invariance

A family of Markov chain Monte Carlo methods whose performance is unaffected by affine tranformations of space is proposed, and computational tests show that the affine invariant methods can be significantly faster than standard MCMC methods on highly skewed distributions.