Astronomy 251 Life on Other Worlds Mondays 4-6, MP102 Prof. Ray Jayawardhana MP 1408416 946 7291...

Astronomy 251

Life on Other Worlds

Mondays 4-6, MP102

Prof. Ray Jayawardhana

MP 1408 416 946 7291 rayjay@astro.utoronto.ca

Office hours: Tuesdays 11-12 or by appt.

Course website and syllabus: http://www.astro.utoronto.ca/~rayjay/ast251

Astronomy 251

Life on Other Worlds

TAs:

Parandis Khavari khavari@astro A-GTim Rothwell rothwell@cita H-NMarija Stankovic stankovic@astro P-Z

Course Textbook

Goldsmith & Owen

The Search for Life in the Universe

Latest news…

Planetary debris disks aroundyoung Sun-like stars

Latest news…

Cassini at Saturn(NASA/ESA joint mission)

layers of haze in Titan’s upper atmosphere

Titan close-up: “Xanadu” and clouds

Latest news…

Cassini at Saturn

Huygens probe released December 25 Will arrive at Titan January 14, and (hopefully!) descend through its thick, smoggy atmosphere

Latest news…

Mars Express (ESA) continues mapping the red planet

Olympus Mons

and a stereo view of its caldera

Evidence of lava flows within the past two million years…

Could some volcanoes be dormant rather than dead?

Latest news…

Receding glaciers in Alaska

Comparison with photos taken as far back as 1883

Of a thousand glaciers in Alaska, only 15 are still growing; rest are stagnant or melting dramatically

Likely culprit: general warming by at least 1.5o C in the 20th century

Toboggan glacier:

in 1909 and 2000

Latest news…

Microbes deep under the ocean floor

New evidence of microbe communities as much as 0.5 km below the ocean floor (core samples taken off Peru in the Pacific Ocean)

These microbes seem to rely ultimately on oxygen and organic matter produced by photosynthesis

Speculation on Extraterrestrial Life

In religion…

Vedda culture (indigenous to Sri Lanka)After death, souls migrate to the Sun, the Moon, and the stars.

Church of Latter-Day Saints (Mormon Church) Souls move to the celestial kingdom; the worthy create new worlds.

Speculation on Extraterrestrial Life

Early scientific speculation…

Greek philosophersBoth Materialists and Idealists held that life extended beyond Earth.

c. 600 BCE Thales of Miletus (first Greek philosopher?) The Earth and stars are made of the same material.

c. 450 BCE AnaxagorasThe Moon is inhabited.

Speculation on Extraterrestrial Life

Epicurian school introduces panspermia: “ubiquitous life”

c. 400 BCE Metrodorus of Chios (atomist; student of Epicurus) “It is unnatural in a large field to have only one shaft of wheat and in the infinite universe only one living world.”

c. 50 BCE Titus Lucretius Carus "Nothing in the universe is unique and alone, and therefore in other regions there must be other Earths inhabited by different tribes of men and breeds of beasts."

Speculation on Extraterrestrial Life

c. 1590 Giordano Bruno (Italian monk)

“Innumerable suns exist; innumerable earths revolve around these suns in a manner similar to the way the seven planets revolve around our sun…”

in De l'Infinito , Universo e Mondi

Burned at stake for his heretical beliefs on February 17, 1600 in Rome

Speculation on Extraterrestrial Life

1750-1830: speculations by writers (de Bergerac, Voltaire, Lomonosov), philosophers (de Fontenelle, Kant), & scientists (Laplace, Herschel, Huygens, Gauss) on panspermia. Herschel: Thinks Sun is inhabited (also held by Newton!)

1820: Karl Gauss suggests planting trees in a right triangle, demonstrating the Pythagorean Theorem to Martians.

1840: Joseph von Littrow suggests kerosene-filled trenches instead.

1853: A caution on habitability: William Whewellouter planets – “water, gases, and vapour” inner planets – “hot water” on surfaces due to proximity to Sun

Speculation on Extraterrestrial Life

c. 1870: Cammille Flammarion writes On the Plurality of Habitable Worlds.

1896: Konstantin Tsiolkovskiy (early rocket scientist)extraterrestrials may be at different stages of development.

1899: Nikola Tesla sends out burst of radio noise, listens for a reply.

LowellEdison

Tesla

Marconi

Speculation on Extraterrestrial Life

c. 1900: Svante Arrhenius (Swedish chemist): Suggests that spores travel among worlds, seeding life.

Speculation on Extraterrestrial Life

1869: Secchi (Italian Astronomer) sees “canali” on Mars.

1877: Schiaparelli describes seasonal variation in “canali”

1900: Percival Lowell suggests “canals” are large-scale engineering structures and extrapolates an entire culture.

Speculation on Extraterrestrial Life

1922 G. Marconi listens for radio signals from a boat in a remote oceanic location.

1960s - now: Fred Hoyle (deceased), N.C. Wickramsinghe argue life – including infectious diseases viruses – fall on Earth from space.

2003…BBC

Big Questions

Class poll...

Big Questions

1. How did life begin and evolve here on Earth?

2. Does life exist elsewhere in the Universe?

3. What is life’s future, on Earth and beyond?

Big Questions

1. Understand how life arose here2. Determine the principles governing the organization of

matter into living systems3. Explore how life evolves on the molecular, organism, and

ecosystem levels4. Determine how the biosphere co-evolves with the Earth5. Establish limits for life in environments that provide

analogues for conditions on other planets6. Determine what makes a planet habitable and how common

these worlds are7. Determine how to recognize the signature of life on another

planet8. Determine if there ever was or even is life elsewhere in the

Solar System – especially on Mars, Europa, or Titan

Big Questions What is life? How did it come about? How does life affect its environment? How does complex life evolve? ...or intelligence?

How many stars & planets?How far apart?What makes a place hospitable to life?What do we learn about other worlds from our own history?

Did life begin on Earth or did it come from elsewhere?Did life start here only once? How long will it last? How many intelligent civilizations are within earshot? ...or within reach? Is the Galaxy colonized? Where is everybody?

Astrobiology & Bioastronomy

AstronomyGeology Geophysics

CosmologyGalaxy EvolutionStar FormationInterstellar MediumAstrochemistry Stellar EvolutionPlanet FormationPlanetary DynamicsEarth/Moon SystemImpact HistoryExternal HazardsSearch for Extraterrestrials

Biology Prebiotic ChemistryAlternate BiochemistryFormation of LifeEvolution & AdaptationLimits of Life Habitability

Creation of CrustOrigins of OceansOxygen AtmosphereGeothermal HeatPlate TectonicsCO

2 – Silicate Cycle

Course Overview

Origin of the Universe, Stars, and PlanetsIntroduction to our GalaxyStellar Evolution and Creation of the Elements

Formation and early evolution of Earth Geological evolution of Earth Beginnings of life on Earth

Life in extreme environments Habitable environments in the Solar SystemHabitable environments and life in the Galaxy

Interstellar communicationInterstellar travel Colonization of the Milky Way?

Grading

25% Midterm Exam

15% Participation

30% Research Paper

30% Final Exam

Research Paper

Jan 31: statement of intents due1 week later: projects should be approved

Topic suggestions available on website

Feb 28: paper outline due

Mar 14: paper itself due

Drake's Equation(1961 Green Bank meeting)

An estimate of the number of inhabited, communicating planets in the Galaxy

Who's out there?

N = R * fs * fp * ne * fl * fi * fc * L

Drake's Equation

Who's out there?

Number of stars in the Galaxy: 1011

Lifetime of Galaxy: 1010 years

Star birth rate…

1011 stars/1010 years

~ 10 stars/year

N = R * fs * fp * ne * fl * fi * fc * L

Drake's Equation

Who's out there?

Fraction of Sun-like stars

1961 view: fs ~ 1/10

N = R * fs * fp * ne * fl * fi * fc * L

Drake's Equation

Who's out there?

Fraction of stars with planets

1961 view: fp ~ 1/2

Principle of Mediocrity

D.Durda

N = R * fs * fp * ne * fl * fi * fc * L

Drake's Equation

Who's out there?

Number of Earth-like planets per extra-solar system

1961 view: ne ~ 1

Again, Principle of Mediocrity

N = R * fs * fp * ne * fl * fi * fc * L

Drake's Equation

Who's out there?

Fraction of Earth-like planets on which life arises

1961 view: fl ~ 1

Yet again, Principle of Mediocrity… plus a look at our own past

Who's out there?

N = R * fs * fp * ne * fl * fi * fc * L

Drake's Equation

Who's out there?

Fraction of biospheres that develop an intelligent species

1961 view: Some intelligence is a good survival trait. So perhaps

fi ~ 1

N = R * fs * fp * ne * fl * fi * fc * L

Drake's Equation

Who's out there?

Fraction of intelligent species that develop technological civilizations and want to communicate

N = R * fs * fp * ne * fl * fi * fc * L

Drake's Equation

Who's out there?

Fraction of intelligent species that develop technological civilizations and want to communicate

1961 view: fc ~ 1/5

N = R * fs * fp * ne * fl * fi * fc * L

Drake's Equation

Who's out there?

Typical lifetime of technological civilizations…

N = R * fs * fp * ne * fl * fi * fc * L

Drake's Equation

Who's out there?

Typical lifetime of technological civilizations…

L = ?L > 50 yr L < 1010 yr

N = R * fs * fp * ne * fl * fi * fc * L

Drake's Equation

Who's out there?

N = R * fs * fp * ne * fl * fi * fc * L

N ~ 10/year * 1/10 * 1/2 * 1 * 1 * 1 * 1/5 * L years

N ~ L/10

L ~ 50 yr

L ~ 109 yr

To those everywhere who seek to make a large number….

-Walter Sullivan dedication in We are Not Alone (1970)

L

Preview of Lecture 2

Any questions?