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-Investigations-

Measurements• 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 PlanetExploring 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

Goal 3: Venus and EarthUnderstanding 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 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?)

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