THE EFFECTS OF SNOWLINES ON C/O IN PLANETARY ATMOSPHERES

Journal Article · Sat Dec 10 04:00:00 EST 2011 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/743/1/L16· OSTI ID:22047301

Oeberg, Karin I; Murray-Clay, Ruth ^[1]

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1. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

The C/O ratio is predicted to regulate the atmospheric chemistry in hot Jupiters. Recent observations suggest that some exoplanets, e.g., Wasp 12-b, have atmospheric C/O ratios substantially different from the solar value of 0.54. In this Letter, we present a mechanism that can produce such atmospheric deviations from the stellar C/O ratio. In protoplanetary disks, different snowlines of oxygen- and carbon-rich ices, especially water and carbon monoxide, will result in systematic variations in the C/O ratio both in the gas and in the condensed phases. In particular, between the H{sub 2}O and CO snowlines most oxygen is present in icy grains-the building blocks of planetary cores in the core accretion model-while most carbon remains in the gas phase. This region is coincidental with the giant-planet-forming zone for a range of observed protoplanetary disks. Based on standard core accretion models of planet formation, gas giants that sweep up most of their atmospheres from disk gas outside of the water snowline will have a C/O {approx} 1, while atmospheres significantly contaminated by evaporating planetesimals will have a stellar or substellar C/O when formed at the same disk radius. The overall metallicity will also depend on the atmosphere formation mechanism, and exoplanetary atmospheric compositions may therefore provide constraints on where and how a specific planet formed.

• OSTI ID: 22047301
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 743; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
79 ASTRONOMY AND ASTROPHYSICS
ASTROPHYSICS
ATMOSPHERIC CHEMISTRY
CARBON
CARBON MONOXIDE
ICE
JUPITER PLANET
OXYGEN
PLANET-SYSTEM ACCRETION
PLANETARY ATMOSPHERES
PROTOPLANETS
SATELLITE ATMOSPHERES
VARIATIONS
WATER
ZONES