Journal article
A stringent upper limit of 20 pptv for methane on Mars and constraints on its dispersion outside Gale crater
- Abstract:
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Context. Reports on the detection of methane in the Martian atmosphere have motivated numerous studies aiming to confirm or explain its presence on a planet where it might imply a biogenic or more likely a geophysical origin.
Aims. Our intent is to complement and improve on the previously reported detection attempts by the Atmospheric Chemistry Suite (ACS) on board the ExoMars Trace Gas Orbiter (TGO). This latter study reported the results of a campaign that was a few months in length, and was significantly hindered by a dusty period that impaired detection performances.
Methods. We unveil 640 solar occultation measurements gathering 1.44 Martian years worth of data produced by the ACS.
Results. No methane was detected. Probing the clear northern summer season allowed us to reach 1σ upper limits of around 10 pptv (20 pptv at 2σ), with an annual mean of the smallest upper limits of 20 pptv. Upper limits are controlled by the amount of dust in the atmosphere, which impairs detection performance around the equator and during the southern spring and summer seasons. Observations performed near Gale crater yielded 1σ upper limits of up to four times less than the background values measured by the Curiosity rover during the corresponding seasons.
Conclusions. Reconciliation of the absence of methane in the TGO spectra with the positive detections by Curiosity is even more difficult in light of this annual survey performed by ACS. Stronger constraints are placed on the physical and chemical mechanism capable of explaining why the mean of the best overall upper limits of ACS is ten times below the smallest methane abundances measured by Curiosity.
- Publication status:
- Published
- Peer review status:
- Peer reviewed
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(Preview, Version of record, 10.5MB, Terms of use)
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- Publisher copy:
- 10.1051/0004-6361/202140389
Authors
- Publisher:
- EDP Sciences
- Journal:
- Astronomy and Astrophysics More from this journal
- Volume:
- 650
- Article number:
- A140
- Publication date:
- 2021-07-20
- Acceptance date:
- 2021-04-23
- DOI:
- EISSN:
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1432-0746
- ISSN:
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0004-6361
- Language:
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English
- Keywords:
- Pubs id:
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1188250
- Local pid:
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pubs:1188250
- Deposit date:
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2021-08-04
Terms of use
- Copyright holder:
- Montmessin et al.
- Copyright date:
- 2021
- Rights statement:
- © F. Montmessin et al. 2021. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
- Licence:
- CC Attribution (CC BY)
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