UltraDeep Drilling and Exploration

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Ultra-Deep Drilling and Exploration Working
Group Ultra-Deep (Geo-)Biological Observatory
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Deep BiosphereS1 Major Research Questions

• How deeply does life extend into the Earth?
• What fuels the deep biosphere?
• How does the interplay between biology and
  geology shape the subsurface?
• What are subsurface genomes telling us?
• Did life on the earth's surface come from
  underground?
• Is there life as we don't know it?

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0 m 7.5C
Ultra-Deep Biological Observatory
Geothermal gradient 22.3 C/km
2440 m 62C
4880 m 116C 16,000
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0 m 7.5C
Ultra-Deep Biological Observatory
Geothermal gradient 22.3 C/km
2440 m 62C
4880 m 116C 16,000
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Why Homestake?

• Science-based
• Homestake has a gradual geothermal gradient
  contrasting with most environments (e.g.,
  Yellowstone, Kamchatka, spreading centers)
  previously investigated for thermophiles
• Biogeochemistry in four dimensions!
• Practical aspects
• Starting from 8000 level (already warm) minimizes
  cost and risk of equipment failure associated
  with coring from ground surface
• Coring proximal to considerable technical
  capabilities in subsurface labs. Examples
• generation of large quantities of ultra pure
  water that will be used for the Cerenkov counter
  but from which we can obtain drilling fluids,
• Nearby earth system and physics research with
  ancillary technologies such as real time
  monitoring of drilling fluid tracers, low
  background radioactive decay counting systems,
  fiber optic temperature and deformation sensors

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Objectives

• Understand factors controlling the distribution
  of life as a function of depth and temperature.
• Observe the changes in microbial diversity,
  microbial activity and nutrients along this
  gradient.

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Hypotheses

• 1. Temperature is the primary factor controlling
  the depth limit of the biosphere.
• 2. Chemoautotrophy increases relative to
  heterotrophy with depth.
• 3. Diversity declines, but phylogenetic novelty
  increases with depth.
• 4. Transfer of genetic elements is limited by low
  cell abundance and low nutrient concentrations.
• 5. Population sizes and/or the low rates of
  genetic recombination impose more rapid rates of
  protein evolution, resulting from inability to
  purge mildly deleterious mutations, as predicted
  by Neutral Theory and empirical data from surface
  ecosystems.
• 6. Energy and/or nutrient limitation select for
  high-affinity uptake strategies coupled with
  motility and chemotaxis or long-term quiescence,
  maintenance, and passive dispersion strategies.
• Associated hypotheses in geology, hydrology, rock
  mechanics, etc.?

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Description of Initial Suite of Experiments

• Test technologies that will be used in the
  ultradeep boreholes at shallow drilling projects.
  The technologies include down hole detection
  methods for life (GOLD).
• Use technologies to characterize the microbial
  contamination results from mining in the drilling
  projects occurring at the shallower levels.
• Staged drilling program beginning with a pilot
  hole to characterize potential targets down to
  16,000

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Additional Hypotheses for Deep Drilling

• Geology
• Proterozoic rock units at Homestake comprise the
  southernmost exposure of the Trans-Hudson orogen
  and are sandwiched between the Trans-Hudson and
  the Superior-Wyoming province. Consequently,
  understanding the stratigraphically lower rocks
  will have a major impact on the paleogeograhic
  reconstruction for the Proterozoic and possibly
  the Archean.

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Geo hypotheses

• Stratigraphically and structurally lower Rock
  units (below Yates) are predicted to be Archean
  crustal and will be encountered at 4000 meters
  drilled depth in a 60 angle borehole from the
  8,000 ft. level
• Alternative to this hypothesis include 1) the
  rocks beneath the Yates Formation are back arc
  basin basalts, gabbro, and possibly ultramafic
  rocks, 2) a major thrust fault will be
  encountered at the base of the Yates that
  juxtaposes the Yates with younger proterozoic
  rocks with depth, and 3) deep boreholes could
  encounter a large Tertiary rhyolite stock..
• n.b. Testing this hypothesis requires
  geochemistry and geochronology data from
  recovered core samples.

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More Geo hypotheses

• Rock mechanics, state of stress in the crust
• Horizontal-to-vertical stress ratio varies as a
  function of depth (directly test by
  hydrofracturing, examining disking/borehole
  breakouts)
• Hydrology/Geochemistry/Microbiology
• ? Rock mass permeability decreases as a function
  of depth except for rare, high-permeability
  fractures that are typically isolated from the
  overall low flux through the rock.
• ? Fluids in fractures below yyyy meters have
  been isolated for XXX millions of years
• ? Microorganisms at depth access microporosity
  only through diffusive mechanisms and this limits
  the rate of metabolism of deep subsurface
  communities

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Drilling/Coring Issues

• Number of holes, Configuration
• Staged approaches in sequential boreholes?
• Diameter(s) -- HQ (4) would be ideal
• Drilling fluids
• Purified water (as for water Cerenkov detector)?
  
• Quantity 10 gpm?
• Recirculating or single pass?
• Tracers
• Temperature effects
• Blow-out prevention
• Corrosion
• Multi-level sampling
• Packers, packer materials, etc.
• Development/testing from shallower depth

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Multidisciplinary Approaches

• Geophysics
• Seismic monitoring
• Cross-borehole tomography
• Thermochronometry
• FEC logging, rock physical properties
• Cross-borehole tomography -- start with existing
  boreholes from 8000L - use to select
  sites/directions for deep boreholes
• Geohydrology - coordinate with Wang/Boutt
  subgroup -- hydraulic tomography
• Geochemistry
• Water samples, core samples
• Down-hole instrumentation for measurement and
  monitoring
• Stable isotopes
• Geochronology
• Biology
• Culture-independent dependent approaches
• Single-cell genomics
• Culture-dependent approaches
• Viruses
• Microbe-mineral interactions

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Downhole instruments

• Fluorescence spectroscopy
• Raman spectroscopy
• Borehole imaging
• Temperature and O2 sensors
• Sidewall coring/water sampling for in situ
  analysis.
• Fiber-optic sensors for Temp., strain

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Modern Microbial Ecology
Environment
Geochemistry
DNA Extraction
Cultivation
Basics -pH -Temp. -Etc.
Advanced -Anions -Cations -XAFS -XANES -Etc.
Media Type
PCR, Clone
BAC, Fosmid
Metagenome, Genome
Cultivars -3 Domains -Aerobic -Anaerobic -Polymic
robial
FISH
Sequence, Phylogeny, Probes
Genetic Identity, Community Function, Molecular
Evolution
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Development Needs

• Cooling for the 8000 level
• Plumbing for Cerenkov detector H2O to 8000L
• Long-term packer, multi-level sampler design
• Robust down-hole instrumentation
• MULE instrumentation specific to Ultra-Deep
  Observatory
• High-pressure coring technology adaptation
• Single cell genomics for water and core samples

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S-4

• Systems design
• Compatibility of technologies
• Sequence of deployment
• Coordination of multidisciplinary aproach
• Sub-WG meetings
• Drilling/coring technology
• Geology/Geochemistry
• To include survey of existing information on
  gt8000 depth
• Geophysics/Geohydrology
• Molecular Biology
• Capstone meeting
• WBS development
• Technology development
• Single cell genomics
• Downhole instruments
• High-pressure coring
• What type of equipment and instrumentation is
  required to extract fluids from the borehole and
  use these fluids? This could be answered by
  visiting ASPO.

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Broader Impacts Education Public Outreach

• Target local Native American STEM students
• Site REU, RETs.
• Portland State and Univ. of Oregon IGERT
• Real time data stream.
• Visitor center displays.