Kevin B. Stevenson, Michael R. Line, Jacob L. Bean, Jean Michel Désert, Jonathan J. Fortney, Adam P. Showman, Tiffany Kataria, Laura Kreidberg, Y. Katherina Feng

Research output: Contribution to journalArticlepeer-review

135 Scopus citations


Previous measurements of heat redistribution efficiency (the ability to transport energy from a planet's highly irradiated dayside to its eternally dark nightside) show considerable variation between exoplanets. Theoretical models predict a positive correlation between heat redistribution efficiency and temperature for tidally locked planets; however, recent Hubble Space Telescope (HST) WASP-43b spectroscopic phase curve results are inconsistent with current predictions. Using the Spitzer Space Telescope, we obtained a total of three phase curve observations of WASP-43b (P = 0.813 days) at 3.6 and 4.5 μm. The first 3.6 μm visit exhibits spurious nightside emission that requires invoking unphysical conditions in our cloud-free atmospheric retrievals. The two other visits exhibit strong day-night contrasts that are consistent with the HST data. To reconcile the departure from theoretical predictions, WASP-43b would need to have a high-altitude, nightside cloud/haze layer blocking its thermal emission. Clouds/hazes could be produced within the planet's cool, nearly retrograde mid-latitude flows before dispersing across its nightside at high altitudes. Since mid-latitude flows only materialize in fast-rotating ( day) planets, this may explain an observed trend connecting measured day-night contrast with planet rotation rate that matches all current Spitzer phase curve results. Combining independent planetary emission measurements from multiple phases, we obtain a precise dayside hemisphere H2O abundance ( at 1σ confidence) and, assuming chemical equilibrium and a scaled solar abundance pattern, we derive a corresponding metallicity estimate that is consistent with being solar (0.4-1.7). Using the retrieved global CO+CO2 abundance under the same assumptions, we estimate a comparable metallicity of 0.3-1.7 solar. This is the first time that precise abundance and metallicity constraints have been determined from multiple molecular tracers for a transiting exoplanet.

Original languageEnglish (US)
Article number68
JournalAstronomical Journal
Issue number2
StatePublished - Feb 2017


  • planetary systems
  • stars: individual (WASP-43)
  • techniques: photometric

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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