1 / 18

Over Two Decades at Mono Domes: Slow Changes to Potential Analogs to Martian Aeolian Bedforms

Over Two Decades at Mono Domes: Slow Changes to Potential Analogs to Martian Aeolian Bedforms.

fawzi
Download Presentation

Over Two Decades at Mono Domes: Slow Changes to Potential Analogs to Martian Aeolian Bedforms

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Over Two Decades at Mono Domes:Slow Changes to Potential Analogs to Martian Aeolian Bedforms Williams, Steven H., Chair, Education Division, National Air and Space Museum, MRC 305, P.O. Box 37012, Washington, DC 20013-7012, williamss@nasm.si.edu; Zimbelman, James R., Chair, Center for Earth and Planetary Studies, National Air and Space Museum, MRC 315, Box 37012, Washington, DC 20013-7012, jrz@nasm.si.edu; Peterfreund, Alan R., Peterfreund Associates, 30 Boltwood Walk, Amherst, MA 01002; and Greeley, Ronald, Department of Geological Sciences, Arizona State University, Box 871404, Tempe, AZ 85287-1404 NOTE: View this presentation in “Notes Page” mode to see commentary. This is not a transcript of the talk as delivered at GSA 2003 in Seattle, but the Notes comments convey the content and flavor of the remarks as delivered at GSA!

  2. Over Two Decades at Mono Domes: Slow Changes in Potential Analogs to Martian Aeolian Bedforms Steven H. Williams James R. Zimbelman Alan R. Peterfreund Ronald Greeley

  3. Large “Ripples”

  4. Large Ripples on Mars • Hinted At in Viking Images • Common and Widespread • Overlain by Dunes and Debris • Some Atop Dunes

  5. Dunes Override Ripples Floor of Crater Kaiser

  6. Ripples Override Dunes M2000635 excerpt

  7. ?

  8. Previous Work Large (“Granule-” / “Deflation-) Ripples: • Kelso Dunes (California) • Coachella Valley • Rogers Dry Lake @ Edwards AFB • Great Sand Dunes National Monument • Coyote Playa All involve granules or coarser materials

  9. Problem! • Terrestrial Granule Ripples are fragile • Prone to removal • Prone to burial by mobile sand • BUT: On Mars, at least some large ripples appear to be older and more durable than their terrestrial counterparts So – do we have the “best” analogs?

  10. Mars “Ripples” Are Old (?) • Note debris apron overlies ripples • Implies ripples long-lived • Implies they are more durable than typical terrestrial granule ripple

  11. Not All Large Ripples Involve Granules! • What if particles involved are distinguished by density, not by size? • Candidate examples: Pumice • Low density allows larger particles to move and create bedforms • Field Example: Mono Domes, California

  12. May, 1981 Large ripples in pumice/obsidian South Mono Dome, California Minimal changes over ~22+ years June, 2003

  13. Bedform Comparison May, 1981 June, 2003

  14. May, 1981 June, 2003 Bedform Comparison

  15. Ripple Crest Alteration Raked Stomped

  16. Typical Bedform Profile

  17. Sedimentary Characteristics • Bedform Crests(D = 1.2 cm) • Pumice 66 wt % r = 1.8 • Obsidian 11 wt % r = 2.1 • Windward Slope(D = ~5 mm) • Pumice 74 wt % r = 1.6 • Obsidian 11 wt % r = 2.1 • More poorly sorted; skewed to fines • Leeward Slope(D = ~5 mm) • Pumice 26 wt % r = 1.6 • Obsidian 37 wt % r = 2.2

  18. Conclusions • Some terrestrial large ripple bedforms are very long-lived • Larger, but lighter, particles may be more mobile

More Related