The McMurdo Dry Valleys form the largest relatively ice-free area on the Antarctic continent. The perennially ice-covered lakes, ephemeral streams and extensive areas of exposed soil are subject to low temperatures, limited precipitation and salt accumulation. The dry valleys thus represent a region where life approaches its environmental limits. This unique ecosystem has been studied for several decades as an analog to environments on other planets, particularly Mars. For the first time, the detailed terrestrial research of the dry valleys is brought together here, presented from an astrobiological perspective. Chapters include a discussion on the history of research in the valleys, a geological background of the valleys, setting them up as analogs for Mars, followed by chapters on the various sub-environments in the valleys such as lakes, glaciers and soils. Includes concluding chapters on biodiversity and other analog environments on Earth.
Author(s): Peter T. Doran, W. Berry Lyons, Diane M. McKnight
Edition: 1
Year: 2010
Language: English
Pages: 320
Tags: Биологические дисциплины;Астробиология;
Half-title......Page 3
Series-title......Page 5
Title......Page 7
Copyright......Page 8
Contents......Page 9
Contributors......Page 11
1 Introduction......Page 15
An early chronology of the dry valleys as a Mars analog......Page 16
Summary of chapters in this book......Page 18
References......Page 22
Abstract......Page 23
Introduction......Page 24
Physical setting and current climate conditions......Page 26
Active-layer cryoturbation......Page 27
MDV microclimate zones......Page 28
The importance of salts and brines......Page 31
Current conditions and physical setting......Page 32
Salts and brines in the martian environment......Page 38
Summary of environmental conditions on Mars......Page 39
Geomorphic analyses of equilibrium landforms on Earth and Mars......Page 40
Coastal thaw zone (CTZ)......Page 41
Inland mixed zone (IMZ)......Page 42
Stable upland zone (SUZ)......Page 44
Synthesis......Page 46
Mars gullies and slope asymmetry......Page 47
Inland mixed zone......Page 49
Synthesis......Page 52
Mars contraction-crack polygons......Page 53
Solifluction lobes, gelifluction lobes, and debris-covered glaciers......Page 55
Stable upland zone......Page 56
Mars viscous-flow features......Page 58
Inland mixed zone......Page 60
Stable upland zone......Page 61
Mars microscale topography......Page 63
Geomorphic evidence for recent climate change in the McMurdo Dry Valleys......Page 66
Geomorphic evidence for recent climate change on Mars......Page 68
Climate change in the earlier history of Mars......Page 73
Antarctica as an astrobiological analog for Mars......Page 74
Summary and conclusions......Page 76
References......Page 77
Introduction......Page 92
Climatic and atmospheric conditions......Page 93
Hydrology......Page 96
Soils and geomorphology......Page 98
Geochemical legacies of aqueous environments in the McMurdo Dry Valleys......Page 102
Contemporary influences of water on surface geochemistry......Page 104
Legacy effects of paleolakes on surface soil geochemistry......Page 111
Considerations for future investigations of Mars......Page 115
References......Page 116
Introduction......Page 124
The Ross Desert......Page 125
The rock substratum and biogenous weathering......Page 126
The Chroococcidiopsis community......Page 130
The lichen-dominated community......Page 131
The Hemichloris community......Page 133
The Hormathonema-Gloeocapsa community......Page 134
Light......Page 136
Moisture......Page 137
Adaptations......Page 138
Temperature......Page 139
Moisture......Page 140
Turnover time and productivity......Page 141
Amino acid racemization and pseudoracemization......Page 142
Implications for possible life on Mars......Page 143
References......Page 144
Introduction......Page 153
Fluvial processes in the Dry Valleys......Page 155
Fluvial history of Mars......Page 159
Stream ecosystems in the Dry Valleys......Page 164
References......Page 169
Introduction......Page 174
Paleolakes on Mars......Page 175
The McMurdo Dry Valleys ice-covered lakes and ponds......Page 177
History/evolution of the Taylor Valley lakes......Page 178
Consequences of lake level fluctuations......Page 180
Lake Fryxell......Page 182
Lake Hoare......Page 184
Lake Bonney......Page 186
Lake Vanda......Page 187
Lake Vida......Page 188
Dry valley ponds......Page 189
Description of dry valley microbial mats......Page 190
Microbial mats growing under perennial ice cover......Page 191
Microbial mats in shallow water environments......Page 192
Permanent lake ice covers......Page 193
Description of Blood Falls......Page 194
Description of Don Juan Pond......Page 197
References......Page 199
Dry Valley glaciers......Page 209
Climate......Page 210
Physical characteristics......Page 211
Hydrology......Page 216
Cryoconite holes and cryolakes biogeochemical reactors......Page 218
Summary of prerequisites for microbial life in Dry Valley glaciers......Page 224
Analogs with Mars......Page 225
Conclusions......Page 230
References......Page 231
The McMurdo Dry Valley ecosystem......Page 235
The McMurdo Dry Valley food web......Page 238
Streams......Page 239
Lakes......Page 241
Soils......Page 246
Cryoconites......Page 248
Ecological factors promoting diversity in the MDV......Page 249
Spatial heterogeneity......Page 254
Competition and predation......Page 257
Temporal variability and disturbance......Page 259
Conclusions......Page 260
References......Page 261
Introduction......Page 272
Declining lake habitats......Page 273
High-altitude lakes environment......Page 275
Investigation......Page 276
Evolution of habitat and life......Page 278
The Ro Tinto system......Page 282
Mars analogy......Page 283
The MARTE project......Page 284
Springs on Earth and Mars......Page 287
Haughton Crater and Devon Island......Page 292
The Haughton-Mars Project......Page 293
Haughton Crater and Mars......Page 294
Devon Island and Mars......Page 296
Aridity and desert analogs......Page 297
Robotic exploration of habitats and life......Page 300
Terrain morphology and appearance......Page 301
Planetary rover prototypes......Page 302
Desert Trek......Page 305
Biogeologic mapping......Page 306
Acknowledgments......Page 309
Index......Page 320
