Transcript Document

Dark Life and DUSEL
• Dark Life – what is it and why is it
important?
• Why DUSEL?
Deep Subsurface (> 1 km)
• Biomass – extremely low - diminishes with
depth to < 103 cells/ml
• Biodiversity diminishes with depth
• Respiratory rates – extremely low – nM/yr
• Space is limited (on Earth 1 – 5% at this
depth)
• Heterogeneity is the rule – oases among
vast deserts
• Fluid flow rates - ~ 1 mm/yr
Cells/ml or Cells/g
0
101
Depth (m)
1000
2000
3000
4000
102
103
104
105
106
107
108
Deep Subsurface (> 1 km)
• Biomass – extremely low - diminishes with
depth to < 103 cells/ml
• Biodiversity diminishes with depth
• Respiratory rates – extremely low – nM/yr
• Fluid flow rates - ~ 1 mm/yr
• Space is limited (on Earth 1 – 5% at this
depth)
• Heterogeneity is the rule – oases among
vast deserts
>100
Pore Throat Radius, microns
75
Size
PORE THROAT SIZE HISTOGRAMClassifications:
25
macro
7.5
2.5
0.75
meso
0.25
micro
0.075
0.025
0.0075
<0.0025
0.0
A.
B.
Mercury Saturation, fraction (frequency)
D.
C.
Dark Life
• nM/yr => ng C/L-yr => 103-4 cells/L-yr
• For 106 cells/L => 100 – 1000 year
lifetimes
• Dosage rate – ~10 Grays/L-year
• nM/yr = mM/Myr. => 100 mg minerals/L –
yr = 100 ml minerals/L-yr = 1% porosity fill
Still in the dark about dark life
• What is the upper temperature limit ?
• Can subsurface life subsist completely without
photosynthetically generated organic
compounds?
• Can life originate in the subsurface?
• How can life evolve in the subsurface given the
glacially slow metabolic rates and withering
irradiation?
• Just how quickly does life migrate through
impermeable formations?
• Why should we care if these creatures hardly do
anything?
Why is it important?
• Methane and recent volcanism (< 2 myr.)
have been discovered on Mars.
• By 2011 rovers will be scraping the
surface for organic signatures of ancient
life.
• By 2015 - 2018 the drilling into Martian
subsurface habitats may provide the first
evidence of exobiology.
• Sample return may bring the first
"martians" back to Earth.
• Unless some significant discovery by telescopic
observations, JIMO to Europa may be out of
reach because of its cost. As for Titan,
everything depends upon Huygens probe.
• Experimentation with self-replicating vesicles
and RNA replicase has brought us closer to
understanding the origin of terrestrial life. (e.g.
Szostak's lab)
• By 2015, life may have been "created" in the lab
and from this we may learn whether life can be
created in the subsurface of a planet.
• Dark life may dominate life in the universe
and may be the means by which life is
transported between solar systems.
Nothing good lasts forever
• By 2015, terrestrial planet finder will be
launched.
• Capable of spectrometric analyses of
atmospheric gases, detecting oceans and
possibly vegetation for stellar systems within 10
parsecs.
• By 2020, attention and resources could (and
should) be directed to these Terra Novae.
• 10-15 year lifetime for major discoveries in Dark
Life with increasingly difficult justification beyond
that.
Why DUSEL?
• NSF supports ODP for high profile investigations
into marine subsurface life (e.g. Ridge). NSF
also supports science investigations associated
with ICDP.
• Coring from surface and operating mines
provide access to 100's kg of rock per year and
in some cases formation fluid.
• Environments accessed include everything from
permafrost, salt beds to high temperature fault
zones and plenty of extremophiles.
• Piggyback operations on extensive existing well
fields provide infrastructure for field experiments.
• DOE supports subsurface experiments directly
relevant to environmental management.
Why DUSEL?
• Deep subsurface life processes are slow – any
experiment designed to examine these
processes require a high spatial sampling
density and long sampling time span.
• Petroleum companies and mines don't care
about subsurface life (unless it affects their
bottom line).
• Boreholes with 1 meter spacing cannot be drilled
at 2 km depth from the surface.
• Some geophysical characterization techniques
(e.g. GPR) are limited to shallow boreholes,
purging and sterility for km long boreholes is
problematic, etc. etc.
Bio-geophysics
• Core and instrument active
fault zone at 3.7 kmbls. in
S. African mine
• Mining induced 3-4 M event
within 2 years
• Monitor gaseous, aqueous
and biological temporal
response.
Monitoring
Instrumentation
Deployment
Stage 3 - Long-Term SAFOD
Monitoring:
• 2005-2007 prototype
• 2007 long-term deployment
• Formaldehyde added to
borehole fluid to prevent
microbial corrosion of metal
tubing and instrumentation
• CMC used in drilling fluid
remains in borehole
Stage 3: Long-Term Monitoring
After coring is completed, plug
3 out of 4 core holes with
cement, leaving 1 open for fluid
pressure monitoring.
Deploy retrievable seismic,
pore pressure, deformation and
temperature monitoring array
inside pipe via pipe or coiled
tubing.
DUSEL Experiments
• Experiment must be unique and virtually impossible for
perform by surface coring.
• The quality, quantity and meaningfulness of the
anticipated data must be higher than can be obtained by
surface mesoscale facilities or deep well fields.
• Multi-user, multi-experiment facilities with multi-year plan
would be most appealing. User base and
experiments/year and thus annual maintenance costs
needs definition. Then DUSEL can provide long term
access to dedicated rock volume for that experiment.
• For truly "dark life" experiments, pristine environments
with "old" groundwater and with strict adherence to
aseptic procedures and connection to NASA Mars
exploration are all prerequisites.
• Connections with low background-counting facility (for
use of radiotracers) needs clarification.