Transcript pres

Venus Exploration Analysis Group:
Scientific 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
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
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)
Aim
• VEXAG will produce MEPAG-like document that
will be a ‘living’document
• Will outline Goals- Objectives-InvestigationsMeasurements
• 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.
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 Earth’s
environment?
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
Goal 1 ctd.
• Quantify the history of volatiles in the interior, surface and
atmosphere of Venus, including degassing and atmospheric
escape, to understand the planet’s 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 planet’s interior) to constrain interior and atmosphere
evolution.
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
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
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
Goal 2:Venus 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-surfaceatmosphere 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
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
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
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
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
Decadal Survey/Strategic Roadmap
NAS Decadal Survey- Venus lander (New Frontiers)
plus future sample return
• Strategic Roadmap for Solar System ExplorationNew 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?)
Where to go?
• From VEXAG to my
opinion!
• Tessera, despite
difficulties has to be
top target
– Possibility for older,
silicic crust
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)
Conclusions
• Participate in VEXAG process
(www.lpi.usra.edu/vexag/)
• 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