Diversity of Habitable planets: anthropic principle, panspermia, and Fermi Paradox
Douglas N.C. Lin Dept of Astronomy & Astrophysics, UC Santa Cruz Kavli Ins tute for Astronomy & Astrophysics, Peking University
Earth-Life Science Ins tute: First Interna onal Symposium Tokyo Ins tute of Technology, Tokyo, Japan. 3.30.2013
19 slides Anthropic Principle Brandon Carter 1983
• Astrophysical and cosmological theorists run the risk of error in the interpreta on of astronomical and cosmological informa on unless due account is taken of the biological restraints under which the informa on was acquired. (Strong Anthropic Principle)
• Biological theorists also run the risk of error in the interpreta on of the evolu onary records unless they take due heed of the astrophysical restraints under which evolu on took place. (Weak Anthropic Principle). 3/19 RV surveys: kinema c diversity
3/19 Gas giants: ubiquity
4/19 Transit surveys: size distribu on
5/19 Structural diversity
Ikoma
6/19 Sequen al assemblage of planets
Paradigm a) natural and robust outcome => planets are common shi s: b) compe ng processes => planetary diversity c) mobility => planetary systems’ probabilis c des nies 7/19 d) changing boundary condi ons => evolving habitable zones Super Earths: some key issues • Did super Earths assemble in situ or form at large a and migrate?
Ida 8/19 Migra on of a Super Earth in protostellar disk around a magne zed T Tauri star. The Super Earth: (a) grows & migrate inward to inner-edge; (b) migrates slightly outwards with the expanding disk inner edge; (c) halts migra ng a er gas is mostly depleted. (Ju et al 2013 in prepara on)
To model P distribu on KIAA undergraduate of Kepler’s new-found student Ju Wenhua planetary candidates. 9/19 now at Princeton U 32/42 New Candidate Catalog Close packing and stability of mul ple systems
Dai
Hirano
Zheng
10/19 Dynamical perturba on by Jupiter-like planets
A gas giant planet disrupted by a sun- like star as a result of planet-planet sca ering or the Kozai effect. Nagasawa
By Shangfei Liu, Graduate Student @ KIAA, PKU 11/19 Many compe ng physical processes Origin of diverse planetary structure
Ogilvie Li
Dai
Liu Zhu Laine Dobbs-Dixon, Wang
12/19 de Colle Poten al life-suppor ng pla orms: a) evolving habitable zones b) common habitable planets
1) Many cradles to start na ve lives 2) Changing boundary condi on as driving force for Darwinian evolu on 3) Many targets for directed panspermia 4) Prospects of sta s cal survey & analysis quan ta ve proofs for genesis models
13/19 Op on 1: In situ origin of life on Earth
1) What makes Earth unique in SS? 2) What me scale is needed ? 3) Changing boundary condi ons as the driving force for evolu on
14/19 Op on 2:Panspermia difficult to verify
Ballis c (interplanetary) panspermia Litho (interstellar) panspermia
15/19 Directed (informa onal) panspermia Few show-stoppers. Possible => probable Liang Search for clustered distribu on and age of habited planets
versus
A systema c survey for bio-signatures on habitable planets. 1) Spa al and temporal distribu on 2) Dependence on stellar and planetary-system proper es 16/19 Fermi’s paradox: WHERE IS ET? Ingredient for Darwinian Evolu on: Meta-stable informa on bases
Survival against obstacles and disasters: Exponen al growth & dissemina on of muta on sexual gene c reproduc on
Adapta on and compe on for resources: Natural selec on, expansionism, ``space filling’’.
Intelligence and self awareness: strategy for survival and prolifera on.
17/19 Fitness peaks & ``poten al’’ valleys
Passive versus ac ve local minima
Local, regional, and global minima 18/19
Advanced civiliza on may be 1 trapped into evolu onary holes 2 reached nonlinear satura on, 3 under self-imposed equilibrium Summary
• Planet forma on is a series of robust, complex, compe ve process. • Mul ple paths of migra on during forma on and evolu on have produced the sta s cal proper es of planetary systems. • Individual planets’ structure and planetary systems’ dynamical architecture are DIVERSE. • Compara ve planetology is needed to understand the mean and dispersion in the boundary condi ons of habitable environments. • Weak anthropic principle provides a scien fic and philosophical basis for an interdisciplinary approach in the search for our roots & des ny. • Characteriza on of exoplanets will greatly expand our horizon with sites of ongoing biological and geological genesis and evolu on. • The discovery and systema c census of bio-signatures on habitable planets will provide historic paradigm-changing evidences to back up extraordinary specula ons. • May ELSI play a prominent and leading role in this exci ng scien fic endeavor and global, profound intellectual pursuit. 19/19