Nachbar, M, Duft, D, Mangan, TP et al. (3 more authors) (2016) Laboratory measurements of heterogeneous CO2 ice nucleation on nanoparticles under conditions relevant to the Martian mesosphere. Journal of Geophysical Research: Planets, 121 (5). pp. 753-769. ISSN 2169-9097
Abstract
Clouds of CO2 ice particles have been observed in the Martian mesosphere. These clouds are believed to be formed through heterogeneous nucleation of CO2 on nanometer-sized meteoric smoke particles (MSPs) or upward propagated Martian dust particles (MDPs). Large uncertainties still exist in parameterizing the microphysical formation process of these clouds as key physicochemical parameters are not well known. We present measurements on the nucleation and growth of CO2 ice on sub-4 nm radius iron oxide and silica particles representing MSPs at conditions close to the mesosphere of Mars. For both particle materials we determine the desorption energy of CO2 to be ΔFdes = (18.5 ± 0.2) kJ mol−1 corresponding to ΔFdes = (0.192 ± 0.002) eV and obtain m = 0.78 ± 0.02 for the contact parameter that governs heterogeneous nucleation by analyzing the measurements using classical heterogeneous nucleation theory. We did not find any temperature dependence for the contact parameter in the temperature range examined (64 K to 73 K). By applying these values for MSPs in the Martian mesosphere, we derive characteristic temperatures for the onset of CO2 ice nucleation, which are 8–18 K below the CO2 frost point temperature, depending on particle size. This is in line with the occurrence of highly supersaturated conditions extending to 20 K below frost point temperature without the observation of clouds. Moreover, the sticking coefficient of CO2 on solid CO2 was determined to be near unity. We further argue that the same parameters can be applied to CO2 nucleation on upward propagated MDPs.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2016. American Geophysical Union. This is an author produced version of a paper published in Journal of Geophysical Research: Planets. Uploaded with permission from the publisher. |
Keywords: | CO2 clouds; Mars; mesosphere; nucleation; meteoric smoke particles; Martian dust |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemistry (Leeds) > Physical Chemistry (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 19 Apr 2016 11:00 |
Last Modified: | 13 May 2019 15:49 |
Published Version: | http://dx.doi.org/10.1002/2015JE004978 |
Status: | Published |
Publisher: | American Geophysical Union (AGU) |
Identification Number: | 10.1002/2015JE004978 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:98601 |