TY - JOUR
T1 - Investigating gully flow emplacement mechanisms using apex slopes
AU - Kolb, Kelly Jean
AU - McEwen, Alfred S.
AU - Pelletier, Jon D.
N1 - Funding Information:
We are indebted to the groups and individuals who made the Digital Elevation Models (DEMs) used in this work: the USGS Astrogeology group (Centauri), Oded Aharonson’s group at Caltech (Hale), and at HiROC: Chris Okubo (Gasa and Kaiser), and Sarah Mattson (Newton). K.J.K. and A.S.M. would like to acknowledge support from the MRO/HiRISE Grant (JPL Subcontract #1272218) and a NASA MDAP Grant # NNX08AL08G . We would also like to thank two anonymous reviewers for their constructive reviews, which greatly improved our manuscript.
PY - 2010/7
Y1 - 2010/7
N2 - The origin of the martian gullies has been much debated since their discovery by the Mars Orbiter Camera (MOC, Malin, M.C., Edgett, K.S. [2000]. Science 288, 2330-2335). Several previous studies have looked at slope gradients in and around gullies, but none have used Digital Elevation Models (DEMs) from the High Resolution Imaging Science Experiment (HiRISE, McEwen, A.S., and 14 colleagues [2007]. J. Geophys. Res. 112 (E05), E0505S02), which has a pixel scale down to 25. cm/pixel. We use five 1. m/post HiRISE DEMs to measure gully apex slopes, the local channel gradient at the upslope extent of the gully debris apron, which marks a shift from erosion to deposition. The apex slope provides information about whether a flow was likely a typical dry granular flow (begins depositing on slopes ~21°) or fluidized by some extra mechanism (depositing on shallower slopes). We find that 72% of the 75 gully fans studied were likely emplaced by fluidized flows. Relatively old gullies appear more likely to have hosted fluidized flows than relatively fresh gullies. This suggests a time and location dependent fluidizing agent, possibly liquid water produced in a different climate as previously proposed. Our results do not provide evidence for water-rich flows in gullies today.
AB - The origin of the martian gullies has been much debated since their discovery by the Mars Orbiter Camera (MOC, Malin, M.C., Edgett, K.S. [2000]. Science 288, 2330-2335). Several previous studies have looked at slope gradients in and around gullies, but none have used Digital Elevation Models (DEMs) from the High Resolution Imaging Science Experiment (HiRISE, McEwen, A.S., and 14 colleagues [2007]. J. Geophys. Res. 112 (E05), E0505S02), which has a pixel scale down to 25. cm/pixel. We use five 1. m/post HiRISE DEMs to measure gully apex slopes, the local channel gradient at the upslope extent of the gully debris apron, which marks a shift from erosion to deposition. The apex slope provides information about whether a flow was likely a typical dry granular flow (begins depositing on slopes ~21°) or fluidized by some extra mechanism (depositing on shallower slopes). We find that 72% of the 75 gully fans studied were likely emplaced by fluidized flows. Relatively old gullies appear more likely to have hosted fluidized flows than relatively fresh gullies. This suggests a time and location dependent fluidizing agent, possibly liquid water produced in a different climate as previously proposed. Our results do not provide evidence for water-rich flows in gullies today.
KW - Geological processes
KW - Mars, Climate
KW - Mars, Surface
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U2 - 10.1016/j.icarus.2010.01.007
DO - 10.1016/j.icarus.2010.01.007
M3 - Article
AN - SCOPUS:77953537992
SN - 0019-1035
VL - 208
SP - 132
EP - 142
JO - Icarus
JF - Icarus
IS - 1
ER -