Mathematics – Logic
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufm.p51b0354h&link_type=abstract
American Geophysical Union, Fall Meeting 2002, abstract #P51B-0354
Mathematics
Logic
5415 Erosion And Weathering, 5462 Polar Regions, 6225 Mars
Scientific paper
Outburst flood channels from the Hesperian and Amazonian Epochs of Mars have conventionally been interpreted as evidence for catastrophic release of groundwater and surface floods akin to jokulhlaups. The Channeled Scablands of Washington state, USA are a type example of this mechanism. However, on Mars there are problems with storage of the large volumes of water in the subsurface, and little evidence for surface impoundments. To explain the volume of erosion requires multiple floods from each source area, which leads to problems of recharge on a cryogenic planet. An alternative model for the floods has been developed in the last few years that explains the outbursts as the violent escape of pressurized liquid CO2, rather than liquid water. The CO2 is trapped underground beneath frozen icy regolith (permafrost) up to 1 km thick, which provides an effective topseal. When the outburst begins, explosive degassing generates a debris cloud akin to a volcanic pyroclastic flow, but at cryogenic temperature. The cloud flows downhill as a density flow, and could potentially erode the observed channels on Mars. Other terrestrial analogues include submarine density flows, which display considerable morphological similarities to Martian channels. There remain some significant problems with CO2-based flow models. To date, no numerical flow model has been offered to support the intuitive conceptual model, and the degree of erosion vs deposition does not match expectation from small-scale flows on Earth. Progress on a numerical flow model will be discussed briefly, as well as scaling relationships that may explain the degree of erosion seen in the channels of Mars. Acknowledging these shortcomings, we nonetheless suggest that the implications of a cold, dry, CO2-based flow model are so significant that the model deserves more attention from the geophysical and planetary science communities. If the model is sustainable, then the implications for the volatile history and thermal evolution of Mars surface and atmosphere are significant and the exobiological outcomes are profound. We also see evidence for CO2-based flows on modern Mars, where I present evidence that flows occur during the springtime thaw of dry ice groundcover. MOC images show "before" and "after" images of flow events in Sisyphi Cavi (70 degrees south, and within the seasonal CO2 polecap). Thin channelised flows occur while surface temperatures are still <200 K, implying that water cannot be responsible, even with eutectic brines. Instead, I suggest that the transition of dry ice to the gas phase acts a lubricant allowing energetic downslope motion of small debris flows. Other channels on sand dunes in Russell Crater are modelled as plough-marks from the collapse of CO2 ice cornices and the sliding and tumbling of ice blocks ~10m across.
No associations
LandOfFree
CO2-based Flows on Ancient and Modern Mars. does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with CO2-based Flows on Ancient and Modern Mars., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and CO2-based Flows on Ancient and Modern Mars. will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1892129