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Permafrost Stability in dry Environments: Antarctica & Mars

Explore permafrost stability in dry regions of Antarctica and Mars, discussing temperature, moisture, ice-cemented permafrost, and implications for ancient ice presence. Comparisons drawn between the Antarctic Dry Valleys and Mars, emphasizing environmental conditions and challenges faced by climate modelers.

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Permafrost Stability in dry Environments: Antarctica & Mars

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  1. Permafrost Stability in dry Environments: Antarctica & Mars 16 Nov 2004 Madison Wisconsin Chris McKay NASA Ames Research Center cmckay@mail.arc.nasa.gov

  2. The Dry Valleys • Largest ice-free region in Antarctica • Temperatures: -20oC average +10oC maximum • 1-2 cm equivalent H2O as snow • Pressure well above triple point of H2O

  3. Lake Vanda and the Onyx River in the Antarctic dry valleys

  4. Linnaeous Terrace, Antarctica Beacon Sandstone Rocks 1500 m elevation Tair < 0oC

  5. Algae and lichens living is a rock “greenhouse” • Temperatures 15oC warmer than the air • Moisture from snowmelt held in pore spaces • Shielded from UV 1 cm

  6. Dry and ice-cemented permafrost at Linnaeous Terrace Temp = -23.3 oC RH = 62% Frost Point= -26 ±1.0oC Air 0 x -18.7oC Active zone 12 cm x -21.1oC Dry permafrost x -21.6oC 25 cm Ice-rich permafrost x -22.3oC

  7. Net Vapor Flux from Ice-cemented Permafrost F = [D/] dn/dz D = 2x10-5 m2 s-1, diffusion coefficient  = 0.41, porosity  = 1.5 - 2.0, tortuosity n = water vapor density z = depth

  8. Net Vapor Flux from Ice-cemented Permafrost F = 0.4 to 0.6 mm/yr = 400 to 600 m/Myr Very old (over 1 Myr) ice-cemented ground Has lost hundreds of meters by ablation Is sealed under very compact soils Is recharged by episodic snowmelt

  9. Mars has extensive dry and ice-rich permafrost

  10. Mars is cold now and it was cold then • Evidence of very low erosion, post Noachian: < 10-9 m/yr, compare to dry valleys 10-6 m/yr • Sporadic distribution of valley features • Unweathered basaltic surface minerals • Climate modelers have difficulty getting mean surface temperatures above 0oC. • No massive surface carbonates detectable by remote sensing.

  11. Odyssey GRS has found near surface water ice polewards of 60o latitude in both hemispheres.

  12. Where is ancient ice? X From:Smith & McKay, PSS 2004; data from Acuna et al, 1999; Barlow, 1997

  13. Limits on long term dormancy • kT: Thermal decay: ~e-E/kTracemization of amino acidsdegradation of organic material • eV: Radiation:background radiation U,Th, K ~0.2rad/yrlethal dose: 2 Mrad for most bugs; 10 Myr 20 Mrad for Deinococcus radiodurans; 100 Myr

  14. Depths below about 1000 m do not feel the obliquity warming ( 1Myr period) Damping depth vs. period

  15. this slide intentionally not left blank

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