Introduction: The Earth today, and the alien worlds around it
1. Before Earth
o Formation of the solar system: temperature and compositional gradients in the cloud
o Planetary rings as analogs to our protoplanetary disk
· Lords of the rings, moons and waves
o Views of extrasolar disks and what they tell us of our roots
· Seeing our past through Hubble and Spitzer
o The “snow line” and structure of the early Sun’s nebular cloud
o Our solar system’s habitable zone
· Habitable zones around other stars
o Our place in the Milky Way galaxy
· The galactic habitable zone
2. Earth=Mercury: Earth as a molten world
o Terrestrial planets begin as molten balls of rock
§ Accretion and differentiation
§ Earth formation: cold or hot?
§ The importance of layers
o Mercury’s beginnings: raining rock and metal
§ The sky is falling: metallic vs stony asteroids, cometary ices
o How Mercury and the Earth differ, solar influences
o Shared heritage, the echoes of planet Mercury within the rocks of Earth
· [news inset: newly discovered mineral inside a diamond hints at the nature of Earth’s deepest mantle]
3. Earth=Venus: Our planet as a Dante-esque oven
o Ocean vs desert, and where the balance lies
o Oceans condense from atmosphere
o Earth before rust: land and sea without free oxygen
· [news inset: Earth’s evil twin: why did Venus end up so different from Earth? Asteroid impacts may be the culprit]
o New dawn for Venus: upcoming missions and what they may soon tell us
4. Earth and the Asteroid belt: the impact of an uneasy relationship during the great solar system cleanup
o Are the asteroids a failed planet?
o What the asteroids added to the Earth’s mix
§ Specific minerals, water, gases
o Birth of the Moon.
§ Theia impact
o [inset: Large low-shear velocity provinces: evidence for Theia remnants?]
o The Moon’s importance for tides, axial stabilization, etc
o The Earth/Jupiter relationship, a natural force-field
· [news inset: missions to the asteroids: can we move the rocks?]
· [news inset: what we’ve learned from Ryugu and Itokawa samples]
5. Earth=Titan
o Titan as a chemical proxy for the early Earth (nitrogen and methane, a winning combination?)
§ Titan’s methane as starting point for complex organics
§ Titan as a snapshot of Earth’s prebiotic chemistry
· Photochemistry leads to building blocks of life
· Earth evidence wiped out, but Titan’s is frozen for us to explore
o The great mystery: first life
§ Was the atmosphere of pre-biotic Earth reduced or oxidized?
§ Hydrogen cyanide and the “cyanosulfidic” pathway to life
§ Panspermia and its problems; cosmic dust and precursors to amino acids
§ Carbonaceous chondrites, comets, and how they relate to life
o Earth as a nursery
§ Chemistry and energy in the beginnings of life
§ Life under pressure: synthesis of organic matter from inorganic molecules near submarine hydrothermal vents and geothermal pools
o Earth’s oxygenating event and how biology sculpts a planetary environment
o Titan as a primordial Earth analog
§ Many parallels with ancient Earth
· Reduced atmosphere; early Titan warmer and richer in oxygen, similar to Earth
· Primary chemical composition and vertical profile of the atmosphere
· Physical and chemical combinations (including thymine and cytosine production at Titan)
· Energy sources (sunlight, Saturn radiation, possible cryovolcanism)
· Atmospheric greenhouse effects
§ Life’s building blocks?
· Cell membranes from acrylonitrile
· Photochemically produced organic chemistry, amino acids and tholins (Miller- Urey and follow-on experiments)
· Three places for water on Titan
· Carbon-based life without accessible water
· Ammonia instead of water: N chemistry and pseudo biochemistry
· Where is the methane coming from?
§ Is life in the universe inevitable? Dinosaurs to protozoans, a rich menagerie
§ Future Titan: a new birthplace?
· [news inset: changes in Earth’s spin may have led to oxygen buildup]
6. Earth=Mars: the “Snowball” or “Slushball” Earth
o The past lives of Earth and Mars
§ Water, water everywhere, but not a drop to breathe: oxygen-poor watery environments of early Mars and Earth
§ Continent configuration: how landmass arrangement affects climate (did Mars have plate tectonics?)
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