Search for Earth 2.0 Criteria

• Hunt for Earth 2.0 ongoing - examined Red Dwarf systems, super Earths, alien exomoons
• No place like home found yet
• Required criteria checklist:
  • Sun-like star
  • Orbit at correct temperature
  • Solid surface
  • Atmosphere retention capability
• Planet may appear Earth-like externally but differ internally

Plate Tectonics and Climate Regulation

• Earth's unique feature: active plate tectonics
• Climate depends on material cycles (CO2, water molecules)
• Molecules move between molten interior and surface through:
  • Active plate tectonics
  • Volcanic eruptions
• Cycles regulate atmospheric temperature and composition
• Geologic activity enables carbon cycle sustainability
• Makes planet habitable and sustainable

Mountain Ranges as Tectonic Indicators

• Vast mountain ranges indicate planet is "alive" with active processes
• Created when tectonic plates collide
• Detection method for exoplanets (light years away):
  • Mountain ranges cause slight size variations during planet rotation
  • Different silhouettes cast depending on rotation
  • Tiny light changes indicate healthy exoplanet
• Limitation: only works when planet transits in front of star

Stellar Composition Analysis

• Planets and stars form simultaneously from same giant material cloud
• Star composition measurement provides planetary composition estimates
• Method: split starlight into wavelengths to identify chemical elements
• Planets around star have similar chemical composition
• Composition crucial for habitability determination

Rocky Planet Composition and Geology

• Basic ingredients: oxygen, silicon, aluminum
• Ingredient balance changes create different planet types
• Composition provides clues about plate tectonics presence
• Research findings:
  • Excess silicon and sodium create different rock types than Earth
  • Results in rigid planets where plate tectonics stall
  • CO2 buildup causes devastating consequences

Consequences of Inactive Geology

• Without active geology: Venusian atmosphere development
• Runaway greenhouse effect progression:
  • Increasing temperatures
  • Gases baked out of rocks
  • No precipitation mechanism
  • Unsuitable for life
• Worst case: planet becomes pressure cooker
• Compositional changes affect tectonic system
• Heat buildup leads to catastrophic crustal overturn
• Results: collapsed solid crust, lava oceans, boiling greenhouse atmosphere
• Violent end to potential habitability

Atmospheric Requirements

• Invisible shield protecting from space dangers
• Provides warmth and life-giving water
• Earth 2.0 requirements:
  • Same mass and size as Earth
  • Sun-like star orbit at similar distance
  • Similar atmosphere
  • Liquid surface water
• Atmosphere functions:
  • Temperature swing protection
  • Small asteroid impact protection
  • Radiation shielding (space and stellar)
  • Literal shield around planet

Solar System Atmospheric Comparison

• Sun's habitable zone includes: Venus, Earth, Mars
• Mars: thin atmosphere, too cold
• Venus: thick atmosphere, too hot
• Earth: "just right" conditions
• Only Earth has suitable atmospheric conditions

Exoplanet Atmosphere Detection Methods

• Previously: mostly guesswork about exoplanet atmospheres
• Current approach: direct detection for Earth-like planets
• Extreme difficulty requires:
  • Incredibly precise technology
  • Precise measurements
  • Managing stellar glare
• Detection technique:
  • Watch planet transit in front of star
  • Small light fraction shines around planet edge through atmosphere
  • Molecules (water, hydrogen, CO2) absorb specific light wavelengths
  • Analysis reveals atmospheric properties: presence, temperature, composition
• Goal: determine surface habitability indicators

Current Status

• No exoplanets found yet with livable atmospheres
• Situation about to change with advancing technology