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Experiments On Sublimating Carbon Dioxide Ice And Implications For Contemporary Surface Processes On Mars.

ABSTRACT: Carbon dioxide is Mars' primary atmospheric constituent and is an active driver of Martian surface evolution. CO₂ ice sublimation mechanisms have been proposed for a host of features that form in the contemporary Martian climate. However, there has been very little experimental work or quantitative modelling to test the validity of these hypotheses. Here we present the results of the first laboratory experiments undertaken to investigate if the interaction between sublimating CO₂ ice blocks and a warm, porous, mobile regolith can generate features similar in morphology to those forming on Martian dunes today. We find that CO₂ sublimation can mobilise grains to form (i) pits and (ii) furrows. We have documented new detached pits at the termini of linear gullies on Martian dunes. Based on their geomorphic similarity to the features observed in our laboratory experiments, and on scaling arguments, we propose a new hypothesis that detached pits are formed by the impact of granular jets generated by sublimating CO₂. We also study the erosion patterns formed underneath a sublimating block of CO₂ ice and demonstrate that these resemble furrow patterns on Mars, suggesting similar formation mechanisms.

SUBMITTER: Mc Keown LE

PROVIDER: S-EPMC5660181 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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Experiments On Sublimating Carbon Dioxide Ice And Implications For Contemporary Surface Processes On Mars.

Mc Keown L E LE Bourke M C MC McElwaine J N JN

Scientific reports 20171027 1

Carbon dioxide is Mars' primary atmospheric constituent and is an active driver of Martian surface evolution. CO<sub>2</sub> ice sublimation mechanisms have been proposed for a host of features that form in the contemporary Martian climate. However, there has been very little experimental work or quantitative modelling to test the validity of these hypotheses. Here we present the results of the first laboratory experiments undertaken to investigate if the interaction between sublimating CO<sub>2 ...[more]

PMID: 29079829

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Project description:BackgroundUncontrolled wildfires in Australian temperate Eucalyptus forests produce significant smoke emissions, particularly carbon dioxide (CO2) and particulates. Emissions from fires in these ecosystems, however, have received less research attention than the fires in North American conifer forests or frequently burned Australian tropical savannas. Here, we use the 2013 Forcett-Dunalley fire that caused the first recorded pyrocumulonimbus event in Tasmania, to understand CO2 and particulate matter (PM2.5) emissions from a severe Eucalyptus forest fire. We investigate the spatial patterns of the two emissions using a fine scale mapping of vegetation and fire severity (50 m resolution), and utilising available emission factors suitable for Australian vegetation types. We compare the results with coarse-scale (28 km resolution) emissions estimates from Global Fire Emissions Database (GFED) to determine the reliability of the global model in emissions estimation.ResultsThe fine scale inventory yielded total CO2 emission of 1.125 ± 0.232 Tg and PM2.5 emission of 0.022 ± 0.006 Tg, representing a loss of 56 t CO2 ha-1 and 1 t PM2.5 ha-1. The CO2 emissions were comparable to GFED estimates, but GFED PM2.5 estimates were lower by a factor of three. This study highlights the reliability of GFED for CO2 but not PM2.5 for estimating emissions from Eucalyptus forest fires. Our fine scale and GFED estimates showed that the Forcett-Dunalley fire produced 30% of 2013 fire carbon emissions in Tasmania, and 26-36% of mean annual fire emissions for the State, representing a significant single source of emissions.ConclusionsOur analyses highlight the need for improved PM2.5 emission factors specific to Australian vegetation, and better characterisation of fuel loads, particularly coarse fuel loads, to quantify wildfire particulate and greenhouse gas emissions more accurately. Current Australian carbon accountancy approach of excluding large wildfires from final GHG accounts likely exaggerates Tasmania's claim to carbon neutrality; we therefore recommend that planned and unplanned emissions are included in the final national and state greenhouse gas accounting to international conventions. Advancing these issues is important given the trajectory of more frequent large fires driven by anthropogenic climate change.

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Experiments On Sublimating Carbon Dioxide Ice And Implications For Contemporary Surface Processes On Mars.

Publications

Experiments On Sublimating Carbon Dioxide Ice And Implications For Contemporary Surface Processes On Mars.

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