Venus Exploration Analysis Group: Scientific Goals for Surface Exploration

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Venus Exploration Analysis GroupScientific
Goals for Surface Exploration

• Ellen R. Stofan, S. Mackwell, K. Baines, S.
  Atreya, J. Luhmann, J. Cutts, T. W. Thompson
• 14 November, 2006
• VEP Landing Site Workshop

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VEXAG

• Venus Exploration Analysis Group (VEXAG)
  established by NASA in July 2005 to identify
  scientific priorities and strategy for the
  exploration of Venus.
• Provides NASA with community-based forum to
  provide scientific input and determine technology
  development requirements for planning and
  prioritizing the exploration of Venus over the
  next several decades.
• Open to all interested scientists,
• VEXAG will report its findings and provide input
  to NASA, but will not make recommendations

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Process

• Chaired by Sushil Atreya (U. Michigan) and Janet
  Luhmann (U. California Berkeley)
• 2 focus groups atmosphere (lead Kevin Baines,
  JPL) and surface and interior (lead Steve
  Mackwell, LPI)
• Website (www.lpi.usra.edu/vexag/)
• 1st and 2nd meetings 11/05 and 5/06, Pasadena CA
• 3rd meeting January 11-12, Washington DC (open to
  all)

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Aim

• VEXAG will produce MEPAG-like document that will
  be a livingdocument
• Will outline Goals- Objectives-Investigations-Meas
  urements
• Draft early 2007
• Within each Goal, Objectives will be prioritized
  based on science and sequence.
• Within each Objectives, series of Investigations
  collectively needed to achieve each objective.
• Investigations may be addressed by single or
  multiple measurements/missions/instruments.
• Significant technology development may be
  required for performing Investigations.

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Goals

• Origin and Early Evolution of Venus How did
  Venus originate and evolve, including the
  lifetime and conditions of habitable environments
  in solar systems?
• Venus as a terrestrial planet What are the
  processes that have and still shape the planet?
• What does Venus tell us about the fate of Earths
  environment?

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Goal 1 Origin and Early evolution of Venus

• Early periods with possible sustained surface
  oceans and climate more amenable to development
  and evolution of life not excluded based on
  present knowledge of Venus.
• Sample surface investigations
• Determine atmospheric composition to seek
  chemical and isotopic signatures of earlier
  epochs of Venus history, and clues to Venus
  origin, formation and evolution through time.
• Measure noble gases and isotopic composition with
  a precision sufficient to enable understanding of
  Venus origin, especially measurements of krypton,
  argon and xenon
• Measure to high precision H/D, nitrogen (14N and
  15N), oxygen, sulfur and carbon isotopes
• Analyze trapped gases in rocks for evidence of
  relict atmosphere
• Analyze stable isotopes for major and trace
  elements

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Goal 1 ctd.

• Quantify the history of volatiles in the
  interior, surface and atmosphere of Venus,
  including degassing and atmospheric escape, to
  understand the planets geologic and atmospheric
  evolution.
• Determine rock mineralogy and composition in
  multiple environments to constrain crustal and
  interior evolution.
• Measure stable isotopes in minerals
• Assess signature of crustal magnetization to
  constrain history of magnetic field
• Determine rock ages to constrain geologic
  history.
• Measure noble gas isotopic ratios (e.g., isotopic
  abundances of radiogenic argon generated by
  radioactive decay of potassium in the planets
  interior) to constrain interior and atmosphere
  evolution.

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Goal 1 ctd.

• Map rock mineralogy and elemental composition on
  a planetary scale to search for evidence of an
  earlier, cooler and wetter Venus.
• Measure in situ mineralogy in multiple
  environments
• Measure n situ bulk chemistry of rocks in
  multiple environments
• Determine surface elemental abundances and
  mineralogy over broad areas
• Assess petrology and petrography of surface rocks
• Determine ages of and stratigraphic context of
  analyzed rocks

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Goal 1 ctd.

• Seek evidence for biologic markers in Venusian
  environments, including sedimentary rock
  structures and/or fossil evidence of biological
  organisms, isotopic anomalies and disequilibrium.
• Characterize sources of chemical disequilibrium
  in the atmosphere
• Measure C, S, N and O isotopes in the atmosphere
• Measure stable isotopes in the atmosphere and
  near the surface
• Determine chemical alteration of surface as a
  function of depth
• Perform in situ analysis of surface units
• Microscopy of rocks including those below the
  surface
• Search for fossils in surface rocks

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Goal 1 ctd.

• Determine the ages of the various rock units on
  the surface, both absolute and relative, in order
  to unravel the past tectonic history of Venus.
• Determine rock ages from multiple sites using
  appropriate dating schemes
• Investigate alternative dating schemes
• Characterize surface exposure ages

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Goal 2Venus as Terrestrial Planet

• Exploring and characterizing processes on and in
  Venus can help us understand dynamical, chemical,
  and geologic processes on alien worlds throughout
  the universe.
• Constrain the resurfacing history of Venus,
  including the current and past rates of volcanic
  activity, including outgassing and
  interior-surface-atmosphere coupling.
• Constrain rate of interior activity and determine
  interior structure
• Measure heat flow and surface temperature to
  constrain thermal structure.
• Determine crustal and interior structure
• Determine absolute ages of surface rock units to
  constrain surface evolution.
• Characterize surface geologic units,
  mineralogically, compositionally and isotopically
• Characterize the geochemical budgets and cycles
  including temporal changes

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Goal 3 Venus and Earth

• Understanding the interior dynamics and
  atmospheric evolution of Venus may provide
  insight into the ultimate fate of Earth
• Search for evidence of past global climate change
  on Venus, including chemical and isotope evidence
  in the atmosphere, as well as rock chemistry and
  characteristics of surface weathering.
• Characetrize the mineralogy of rocks
• Measure trapped gases in rocks from earlier
  epochs
• Assess paleoclimate indicators, stable isotopes
  (O, S, H )
• Search for geomorphological evidence of climate
  change
• Search for evidence of past life, such as fossils

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Goal 3 ctd.

• Search for evidence of past changes in interior
  dynamics and tectonics, including possible
  evolution from plate tectonics to stagnant-lid
  tectonics, which may have resulted in significant
  changes in the global climate pattern.
• Measure chemical and isotopic composition
• Search for paleomagnetic signatures
• Constrain interior structure

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Goal 3 ctd.

• Characterize the Venus Greenhouse effect,
  including its interaction with surface and
  interior, allowing a comparison to atmospheric
  evolution on Earth, Mars, Titan and extra-solar
  planets.
• Obtain temperature profiles
• Characterize surface geochemistry including
  alteration rind depth and composition
• Constrain rate of volcanic outgassing and
  composition

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Summary

• Detailed atmospheric chemistry including
  chemistry lower atmosphere and surface/atmosphere
  interactions
• Surface mineralogy and bulk geochemistry
• Descent imaging
• Biomarkers
• Technological challenges Seismology, surface age

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Decadal Survey/Strategic Roadmap

• NAS Decadal Survey- Venus lander (New Frontiers)
  plus future sample return
• Strategic Roadmap for Solar System Exploration-
  New Frontiers reaffirmed, plus follow-on landed
  mission to highlands of Venus where the
  possibility exists to find more silicic crust
  (emphasis on mobility)
• Focus on surface geochemistry, atmosphere
  analysis
• Technologies for survival in extreme environments
  (seismic mission?)

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Where to go?

• From VEXAG to my opinion!
• Tessera, despite difficulties has to be top
  target
• Possibility for older, silicic crust

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Other options

• Combination of volcanic/stratigraphy sites
• Hotspot flanks (geochemistry mantle) (Atla, Bell)
• young/older plains boundary
• Mixed volcanic field (Sedna/Guinevere)
• Without mobility, all sites have scientific
  limitations (ex. MER)

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Conclusions

• Participate in VEXAG process (www.lpi.usra.edu/vex
  ag/)
• Surface studies critical to all aspects of Venus
  studies- in particular understanding the
  mineralogy of surface rocks, their age, and
  interior structure
• Descent imaging critical on any mission to allow
  ground truth for Magellan data, further
  information on surface age relationships
• Tessera, despite landing difficulties, best
  target