CORDIS OpenAire Sygma Bielefeld Academic Search Engine (BASE) Pure Utrecht University HAL-INSU Crossref Microsoft Academic Graph Europe PubMed Central ARUdA UnpayWall Utrecht University Repository Durham Research Online PubMed Central European Union Open Data Portal http://dro.dur.ac.uk/28802/1/28802.pdf http://dro.dur.ac.uk/28802/2/28802.pdf https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2018JE005899 https://doi.org/10.1029/2018JE005899 Journal of Geophysical Research: Planets Open Access 2020-03-09 2019-08-01 2020-03-23 2019-12-12 2019-12-02 2020-12-31 2021-01-07 <p> &amp;lt;p&amp;gt;Understanding the initial and flow conditions of contemporary flows in Martian gullies, generally believed to be triggered and fluidized by CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; sublimation, is crucial for deciphering climate conditions needed to trigger and sustain them. We employ the RAMMS (RApid Mass Movement Simulation) debris flow and avalanche model to back-calculate initial and flow conditions of recent flows in three gullies in Hale crater. We infer minimum release depths of 1.0&amp;amp;#8211;1.5 m and initial release volumes of 100&amp;amp;#8211;200 m&amp;lt;sup&amp;gt;3&amp;lt;/sup&amp;gt;. Entrainment leads to final flow volumes that are 2.5&amp;amp;#8211;5.5 times larger than initially released, and entrainment is found necessary to match the observed flow deposits. Simulated mean cross-channel flow velocities decrease from 3&amp;amp;#8211;4 m s&amp;lt;sup&amp;gt;-1&amp;lt;/sup&amp;gt; to ~1 m s&amp;lt;sup&amp;gt;-1&amp;lt;/sup&amp;gt; from release area to flow terminus, while flow depths generally decrease from 0.5&amp;amp;#8211;1 m to 0.1&amp;amp;#8211;0.2 m. The mean cross-channel erosion depth and deposition thicknesses are _0.1&amp;amp;#8211;0.3 m. Back-calculated dry-Coulomb friction ranges from 0.1 to 0.25 and viscous turbulent friction between 100&amp;amp;#8211;200 m s&amp;lt;sup&amp;gt;-2&amp;lt;/sup&amp;gt;, which are values similar to those of granular debris flows on Earth. These results suggest that recent flows in gullies are fluidized to a similar degree as are granular debris flows on Earth. Using a novel model for mass-flow fluidization by CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; sublimation we are able to show that under Martian atmospheric conditions very small volumetric fractions of CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; of ~1% within mass flows may indeed yield sufficiently large gas fluxes to cause fluidization and enhance flow mobility.&amp;lt;/p&amp;gt; </p> Atmospheric Science 550 [SDU.STU.GM] Sciences of the Universe [physics]/Earth Sciences/Geomorphology 0211 other engineering and technologies Soil Science Mars Hale crater 02 engineering and technology Aquatic Science carbon dioxide; gullies; Hale crater; Mars; modeling; RAMMS 551 Oceanography 01 natural sciences [SDU.STU.PL]Sciences of the Universe [physics]/Earth Sciences/Planetology Geochemistry and Petrology Earth and Planetary Sciences (miscellaneous) SDG 13 - Climate Action Research Articles Water Science and Technology Earth-Surface Processes 0105 earth and related environmental sciences Ecology Palaeontology carbon dioxide Forestry modeling RAMMS Geophysics Space and Planetary Science 13. Climate action [SDU.STU.PL] Sciences of the Universe [physics]/Earth Sciences/Planetology gullies Susan J. Conway, Jim McElwaine, Jim McElwaine, F. Salese, T. de Haas, T. de Haas, Peter Grindrod, Maarten G. Kleinhans, Brian W. McArdell, 2019-08-01 journalpaper <p> &amp;lt;p&amp;gt;Understanding the initial and flow conditions of contemporary flows in Martian gullies, generally believed to be triggered and fluidized by CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; sublimation, is crucial for deciphering climate conditions needed to trigger and sustain them. We employ the RAMMS (RApid Mass Movement Simulation) debris flow and avalanche model to back-calculate initial and flow conditions of recent flows in three gullies in Hale crater. We infer minimum release depths of 1.0&amp;amp;#8211;1.5 m and initial release volumes of 100&amp;amp;#8211;200 m&amp;lt;sup&amp;gt;3&amp;lt;/sup&amp;gt;. Entrainment leads to final flow volumes that are 2.5&amp;amp;#8211;5.5 times larger than initially released, and entrainment is found necessary to match the observed flow deposits. Simulated mean cross-channel flow velocities decrease from 3&amp;amp;#8211;4 m s&amp;lt;sup&amp;gt;-1&amp;lt;/sup&amp;gt; to ~1 m s&amp;lt;sup&amp;gt;-1&amp;lt;/sup&amp;gt; from release area to flow terminus, while flow depths generally decrease from 0.5&amp;amp;#8211;1 m to 0.1&amp;amp;#8211;0.2 m. The mean cross-channel erosion depth and deposition thicknesses are _0.1&amp;amp;#8211;0.3 m. Back-calculated dry-Coulomb friction ranges from 0.1 to 0.25 and viscous turbulent friction between 100&amp;amp;#8211;200 m s&amp;lt;sup&amp;gt;-2&amp;lt;/sup&amp;gt;, which are values similar to those of granular debris flows on Earth. These results suggest that recent flows in gullies are fluidized to a similar degree as are granular debris flows on Earth. Using a novel model for mass-flow fluidization by CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; sublimation we are able to show that under Martian atmospheric conditions very small volumetric fractions of CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; of ~1% within mass flows may indeed yield sufficiently large gas fluxes to cause fluidization and enhance flow mobility.&amp;lt;/p&amp;gt; </p> Initiation and Flow Conditions of Contemporary Flows in Martian Gullies 10.1029/2018JE005899