Atacama Life

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Atacama Life

• Chris McKay
• NASA Ames
• cmckay_at_mail.arc.nasa.gov

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A transect from arid to extreme arid
Yungay station, extreme arid 50 times drier than
Death Valley
500 km south of Yungay, arid about as dry as
Death Valley
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Colonized Stones in the Atacama Desert
Warren-Rhodes et al. Micro. Ecol. 2005
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Crestline for the coastal range in the Atacama
Desert
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Rock garden
Altamira

• Vineyard

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Desert ecosystems
Biology wins reducing
Photochemistry wins, oxidizing
Shrubs and insects
Hypolithic algae
Life
Soil Bacteria
Mojave Desert
Mars-like soils
Gobi Desert
Nitrate deposits
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25
1
125
0.2
Moisture mm/yr
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Navarro-Gonzalez et al. Science, 2003
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"Self-organized patchiness and the resource
concentration mechanisms involved have been
reported from various ecosystems, among which
arid ecosystems are the most prominent." Rietker
et al.2005, Self-Organized Patchiness and
Catastrophic Shifts in Ecosystems. Science, 305,
1926-1929.
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• Hypothesis Microbial Patchiness in the Atacama
  Desert is due to oxidant.
• Constant and uniform production of oxidant.
• If biological production of organics exceeds
  oxidant ? habitable zone.
• If biological production of organics is less
  than oxidant ? not habitable zone.
• 4. Organisms in, or falling into, habitable zone
  grow creating positive feedback.

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Bacterial Counts
Moisture
BiologyOxidant
BiologygtOxidant
BiologyltOxidant
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Implications

• Length scale of patchiness should vary with
  moisture.
• Soil organics will be patchy and correlate with
  soil organisms.
• Soil oxidant will be patchy and anti-correlated
  with organisms.