Solar System: Inner PlanetsSolar System: Inner Planets

Stephen Kane

Why Studying the Solar Why Studying the Solar System Terrestrial Planets is System Terrestrial Planets is Absolutely Critical for the Absolutely Critical for the

Future of Exoplanet Future of Exoplanet Characterization and Characterization and

Understanding HabitabilityUnderstanding Habitability

Stephen Kane

Exoplanetary Science = Planetary Science

Exoplanetary Science ≠ Planetary ScienceIt is Stellar Astrophysics!

Exoplanetary Science ≠ Planetary ScienceIt is Stellar Astrophysics!

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Exoplanetary Science ≠ Planetary ScienceIt is Stellar Astrophysics!

Typical image of Solar System terrestrial planet

Very best image of a terrestrial exoplanet

Typical image of Solar System terrestrial planet

Very best image of a terrestrial exoplanet

The overlap is where planetary science translates into exoplanet observables!

NASA’s future exploration of Venus should strive to achieve three non-prioritized Goals:I. Understand Venus’ early evolution and potential habitability to constrain the evolution of Venus-sized (exo)planets,II. Understand atmospheric composition and dynamics on Venus, andIII. Understand the geologic history preserved on the surface of Venus and the present-day couplings between the surface and atmosphere.

Chair: Darby Dyar

Deputy Chair: Noam Izenberg

1. Terrestrial exoplanets are extremely common, and will form the basis for atmospheric measurements.

Why Studying Solar System Planets is NecessaryWhy Studying Solar System Planets is Necessary

1. Terrestrial exoplanets are extremely common, and will form the basis for atmospheric measurements.

2. Solar system science is continually advancing, with frequent, and often significant, revisions to prevailing models of atmospheres, surfaces, and interiors.

Why Studying Solar System Planets is NecessaryWhy Studying Solar System Planets is Necessary

1. Terrestrial exoplanets are extremely common, and will form the basis for atmospheric measurements.

2. Solar system science is continually advancing, with frequent, and often significant, revisions to prevailing models of atmospheres, surfaces, and interiors.

3. We will never have in-situ data for an exoplanet. Surface conditions will always be inferred from models based on solar system data.

Why Studying Solar System Planets is NecessaryWhy Studying Solar System Planets is Necessary

Mercury: Outstanding QuestionsMercury: Outstanding Questions● Did Mercury form with its large core, or did a giant impact strip away silicate layers?

● What are the geochemical characteristics of Mercury’s crust, including the relative abundances of carbon and volatile elements?

● How does the current surface structure/geology inform us of the interior cooling rate and potential contraction of the crust?

● When did volcanic activity at the surface end? Did Mercury previously have an atmosphere and what was the time scale for its loss?

● Insofaras the Mercury and lunar surfaces preserve the early solar system impact history, what does this imply for the evolution of Venus, Earth, and Mars?

Venus: Outstanding QuestionsVenus: Outstanding Questions● What is the interior structure and composition of Venus? How much does it differ from the Earth and the Sun?

● What has been the history of tectonics, volatile cycling, and volcanic resurfacing (Ivanov & Head 2011)? Was the delivery of volatiles to the atmosphere gradual, episodic, or catastrophic? When did Venus enter its present stagnant-lid regime? Does any subduction occur today (Smrekar et al. 2018)?

● What is the detailed composition and atmospheric chemistry that exists within the Venusian middle and deep atmosphere and how does it interact with the surface?

● Where did the water go? Was hydrogen loss and abiotic oxygen production prevalent, or did surface hydration dominate?

● Did Venus have a habitable period (Way et al. 2016)? That is, did Venus ever cool after formation (Hamano et al. 2013)? If Venus had a habitable period, how long did it last?

Earth: Outstanding QuestionsEarth: Outstanding Questions● How long did the magma surface period last during the Hadean eon?

● When did life originate and evolve On Earth? How has petrology and degassing at the ocean floor modified interior contributions to the atmosphere?

● How important was the moon-forming collision for the structure of the Earth’s mantle and the subsequent evolution of life on Earth?

● What is the role of volatiles (liquid water) in continental plate subduction and the carbon cycle, and can this cycle be maintained without volatiles?

● How has the composition of the Earth’s atmosphere changed with time due to the influence of biology (biosignatures)?

Mars: Outstanding QuestionsMars: Outstanding Questions● What is the current state of the internal structure and activity? How does the present internal state relate to surface geology and potential dynamo?

● What caused the major transition from Early Mars to Middle Mars?

● Where are the major aqueous locations and how does that relate to the local geology?

● How does the Martian atmosphere interact with the solar wind and what is the history of atmospheric loss and climate change?

● What is the lower size limit for sustained planetary habitability?

The Pathway ForwardThe Pathway Forward

The Pathway ForwardThe Pathway Forward

1. Uncertainties in solar system models translate directly into catastrophic uncertainties for exoplanets. Many questions remain for the solar system terrestrial planets, the answers of which will directly benefit exoplanets.

2. Addressing these questions requires a variety of mission concepts, including orbiters, gliders, balloons, and landers. In-situ analyses of the geology and composition-temperature-pressure profile of atmospheres are critical.

3. The solar system science questions have strong overlap with the data/model needs of future exoplanet missions, and such overlap areas should be prioritized.