Entrapment of CO in CO2 ice

Abstract

Planet atmosphere and hydrosphere compositions are fundamentally set by accretion of volatiles, and therefore by the division of volatiles between gas and solids in planet-forming disks. For hyper-volatiles such as CO, this division is regulated by a combination of binding energies, and by the ability of other ice components to entrap. Water ice is known for its ability to trap CO and other volatile species. In this study we explore whether another common interstellar and cometary ice component, CO2, is able to trap CO as well. We measure entrapment of CO molecules in CO2 ice through temperature programmed desorption (TPD) experiments on CO2:CO ice mixtures. We find that CO2 ice traps CO with a typical efficiency of 40-60% of the initially deposited CO molecules for a range of ice thicknesses between 7 and 50ML, and ice mixture ratios between 1:1 and 9:1. The entrapment efficiency increases with ice thickness and CO dilution. We also run analogous H2O:CO experiments and find that under comparable experimental conditions CO2 ice entraps CO more efficiently than H2O ice up to the onset of CO2 desorption at ~70K. We speculate that this may be due to different ice restructuring dynamics in H2O and CO2 ices around the CO desorption temperature. Importantly, the ability of CO2 to entrap CO may change the expected division between gas and solids for CO and other hyper-volatiles exterior to the CO2 snowline during planet formation.

arXiv comment11 pages, 11 figures, accepted for publication in ApJ

References in corpus (23)

• Observations of the Icy Universe
• The effects of snowlines on C/O in planetary atmospheres
• Complex Chemistry in Star-Forming Regions: An Expanded Gas-Grain Warm-up Chemical Model
• The Spitzer ice legacy: Ice evolution from cores to protostars
• Accretion Disks Around Young Objects. II. Tests of Well-Mixed Models with Ism Dust
• An Old Disk That Can Still Form a Planetary System
• The c2d Spitzer spectroscopic survey of ices around low-mass young stellar objects II: CO2
• The chemical history of molecules in circumstellar disks. I. Ices
• The Radial Distribution of H2 and CO in TW Hya as Revealed by Resolved ALMA Observations of CO Isotopologues
• Lupus disks with faint CO isotopologues: low gas/dust or large carbon depletion?
• The Coupled Physical Structure of Gas and Dust in the IM Lup Protoplanetary Disk
• An ALMA Survey of CO isotopologue emission from Protoplanetary Disks in Chamaeleon I
• Laboratory H2O:CO2 ice desorption data: entrapment dependencies and its parameterization with an extended three-phase model
• Unlocking CO Depletion in Protoplanetary Disks I. The Warm Molecular Layer
• CO and N${}_2$ desorption energies from water ice
• Composition of Early Planetary Atmospheres I: Connecting Disk Astrochemistry to the Formation of Planetary Atmospheres
• The Role of Ice Compositions for Snowlines and the C/N/O Ratios in Active Disks
• Molecular Oxygen in Oort Cloud Comet 1P/Halley
• A protosolar nebula origin for the ices agglomerated by Comet 67P/Churyumov-Gerasimenko
• The dual origin of the nitrogen deficiency in comets: selective volatile trapping in the nebula and postaccretion radiogenic heating
• CO diffusion and desorption kinetics in CO${}_2$ ices
• A $\sim$32-70 K formation temperature range for the ice grains agglomerated by comet 67P/Churyumov-Gerasimenko
• Characterization of thin film CO${}_2$ ice through the infrared ${\nu }_1+{\nu }_3$ combination mode

Cited by in corpus (10)

• Jupiter's composition suggests its core assembled exterior to the N2 snowline
• Thermophysical evolution of planetesimals in the Primordial Disk
• Are there any pristine comets? Constraints from pebble structure
• Locked In Ice: how Pebble Drift and Volatile Entrapment can Significantly Impact Carbon and Oxygen Ratios in Evolving Protoplanetary Discs
• Evaporative cooling of icy interstellar grains II. Key parameters
• H2S ice sublimation dynamics: experimentally constrained binding energies, entrapment efficiencies, and snowlines
• Collisional heating of icy planetesimals. I. Catastrophic collisions
• Methyl Isocyanate Formation from Oxygen Insertion in Methyl Cyanide Ices
• A fast machine learning tool to predict the composition of astronomical ices from infrared absorption spectra
• HCN snowlines in protoplanetary disks: constraints from ice desorption experiments