Understanding martian gullies

1. DISCUSSION • Simulations in flume show three distinct sections of the gully • Some gully parameters show a stronger relationship than others to the changing flow rate and/or changing slope • Gully response to flow rate changes are visually more obvious than slope changes • Many of the high, isolated points on graphs can be attributed to high sand saturation during run • Most noticeable in the apron, saturation has a relationship with measurements and shape of gully sections 4 mm Channel Apron Alcove Saturation Widths Lengths Depths Understanding martian gullies Howe, K. L.1,2, Coleman, K. S. A.2,3, Dixon, J.C 2,3 1 Department of Geological Sciences, State University of New York at Geneseo, Geneseo, NY 14454; 2Arkansas Center for Space and Planetary Sciences, University of Arkansas, Fayetteville, AR 72701; 3Department of Geosciences, University of Arkansas, Fayetteville, AR 72701 INTRODUCTION RESULTS • Malin and Edgett (2000) identified martian features that resemble earth gullies • Questions as to the formation of martian gullies exist since gullies are often located in areas with surface temperatures below water’s freezing point • Objective of this study: simulate gully formation with morphologies similarto those observed on Mars and use the results to identify potential fluid and formation characteristics Alcove Volume Dimensions vs. Flow Rate Alcove Length Alcove Width 4 mm 4 mm Alcove Depth Alcove Measurements (mm) Flow Rate (ml/s) at 10°Slope Alcove Volume Dimensions vs. Slope Alcove Volume Dimensions vs. Slope METHODOLOGY • Simulations run in 1x1.5 meter flume (Figure 1) • Water flows from overhead bucket, through flow meter into tubing sunk below the sand surface and emerges at the break in slope Alcove Measurements (mm) Slope (degrees) Figure 4: Differences in shape of gully sections are apparent with different saturations. Both pictures at slope 20°and flow 705 ml/s. High saturation on left; lower saturation on right. Figure 3: Graphs show that length, width and depth of the gully alcoves are affected by changes in flow rate (top) and changes in slope (bottom) Figure 1: The flume allows for the process of gully formation to be studied CONCLUSIONS • Gully formation simulated in the flume can be used to study martian gullies • Both slope and flow rate have noticeable effects on alcove, channel and apron measurements • Parameter most impacted by changing slope and flow rate was the total gully volume • Least effected parameters are the depths, especially at base of the channels • Aprons of saturated runs tend to be thinner and more triangular shaped than the thicker, lobate aprons of less saturated runs • The alcove, channel and apron measurements (length, width, depth) are taken and sand saturation is measured (Figure 2) • Parameters are recorded and graphed (Figure 3) for 4 different flows (445, 705, 965, 1260 ml/s) at 3 different slopes (10°, 20°, 30°) ACKNOWLEDGEMENTS REFERENCES FUTURE RESEARCH Malin, M. C. and Edgett, K. S., 2000, Evidence for recent ground water seepage and surface runoff on Mars: Science, v. 288, no. 5475, p. 2330-2336. Arkansas Center for Space and Planetary Sciences for funding Walter Graupner for technical assistance • Detailed morphometric analysis of gullies will be conducted using GIS and similar resources Figure 2: Measurement of gully parameters allows for analysis of gully morphology