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Astronomy 251 Life on Other Worlds Mondays 4-6, MP102 Prof. Ray Jayawardhana MP 1408 416 946 7291 [email protected] 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:

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Astronomy 251

Life on Other Worlds

Mondays 4-6, MP102

Prof. Ray Jayawardhana

MP 1408 416 946 7291

[email protected]

Office hours: Tuesdays 11-12 or by appt.

Course website and syllabus:

http://www.astro.utoronto.ca/~rayjay/ast251


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Astronomy 251

Life on Other Worlds

TAs:

Parandis Khavari [email protected] A-G

Tim Rothwell [email protected] H-N

Marija Stankovic [email protected] P-Z


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Course Textbook

Goldsmith & Owen

The Search for Life in the Universe


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Latest news…

Planetary debris disks around

young Sun-like stars


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Latest news…

Cassini at Saturn

(NASA/ESA joint mission)

Titan close-up: “Xanadu” and clouds

layers of haze in Titan’s upper atmosphere


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Latest news…

Cassini at Saturn

Huygens probe released December 25

Will arrive at Titan January 14, and (hopefully!) descend through its thick, smoggy atmosphere


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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?


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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


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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


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Speculation on Extraterrestrial Life

In religion…

Veddaculture (indigenous to Sri Lanka)

After death, souls migrate to the Sun, the Moon, and the stars.

ChurchofLatter-DaySaints (Mormon Church)

Souls move to the celestial kingdom; the worthy create new worlds.


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Speculation on Extraterrestrial Life

Early scientific speculation…

Greek philosophers

Both 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 Anaxagoras

The Moon is inhabited.


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Speculation on Extraterrestrial Life

Epicurian school introducespanspermia: “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 BCETitus 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."


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Speculation on Extraterrestrial Life

c. 1590Giordano 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…”

inDe l'Infinito , Universo e Mondi

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


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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 byNewton!)

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

1840:Joseph von Littrowsuggests kerosene-filled trenches instead.

1853: A caution on habitability: William Whewell

outer planets – “water, gases, and vapour”

inner planets – “hot water” on surfaces due to proximity to Sun


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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 Teslasends out burst of radio noise, listens for a reply.

Tesla

Marconi

Lowell

Edison


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Speculation on Extraterrestrial Life

c. 1900: Svante Arrhenius (Swedish chemist):

Suggests that spores travel among worlds, seeding life.


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Speculation on Extraterrestrial Life

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

1877: Schiaparellidescribes seasonal variation in “canali”

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


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Speculation on Extraterrestrial Life

1922G. 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


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Big Questions

Class poll...


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Big Questions

  • How did life begin and evolve here on Earth?

  • Does life exist elsewhere in the Universe?

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


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Big Questions

  • Understand how life arose here

  • Determine the principles governing the organization of matter into living systems

  • Explore how life evolves on the molecular, organism, and ecosystem levels

  • Determine how the biosphere co-evolves with the Earth

  • Establish limits for life in environments that provide analogues for conditions on other planets

  • Determine what makes a planet habitable and how common these worlds are

  • Determine how to recognize the signature of life on another planet

  • Determine if there ever was or even is life elsewhere in the Solar System – especially on Mars, Europa, or Titan


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Big Questions

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?

What is life?

How did it come about?

How does life affect its

environment?

How does complex life

evolve?

...or intelligence?

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?


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Astrobiology & Bioastronomy

Geology

Geophysics

Biology

Astronomy

Prebiotic Chemistry

Alternate Biochemistry

Formation of Life

Evolution & Adaptation

Limits of Life

Habitability

Cosmology

Galaxy Evolution

Star Formation

Interstellar Medium

Astrochemistry

Stellar Evolution

Planet Formation

Planetary Dynamics

Earth/Moon System

Impact History

External Hazards

Search for Extraterrestrials

Creation of Crust

Origins of Oceans

Oxygen Atmosphere

Geothermal Heat

Plate Tectonics

CO2 – Silicate Cycle


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Course Overview

Origin of the Universe, Stars, and Planets

Introduction to our Galaxy

Stellar 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 System

Habitable environments and life in the Galaxy

Interstellar communication

Interstellar travel

Colonization of the Milky Way?


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Grading

15% Participation

25% Midterm Exam

30% Research Paper

30% Final Exam


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Research Paper

Topic suggestions available on website

Jan 31: statement of intents due

1 week later: projects should be approved

Feb 28: paper outline due

Mar 14: paper itself due


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Who's out there?

Drake's Equation

(1961 Green Bank meeting)

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

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


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Who's out there?

Drake's Equation

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

Number of stars in the Galaxy: 1011

Lifetime of Galaxy: 1010 years

1011 stars/1010 years

~ 10 stars/year

Star birth

rate…


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Who's out there?

Drake's Equation

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

Fraction of Sun-like stars

1961 view: fs ~ 1/10


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Who's out there?

Drake's Equation

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

Fraction of stars with planets

D.Durda

1961 view: fp ~ 1/2

Principle of Mediocrity


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Who's out there?

Drake's Equation

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

Number of Earth-like planets per extra-solar system

1961 view: ne ~ 1

Again, Principle of Mediocrity


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Who's out there?

Who's out there?

Drake's Equation

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

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


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Who's out there?

Drake's Equation

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

Fraction of biospheres that develop an intelligent species

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

fi ~ 1


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Who's out there?

Drake's Equation

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

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


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Who's out there?

Drake's Equation

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

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

1961 view: fc ~ 1/5


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Who's out there?

Drake's Equation

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

Typical lifetime of technological civilizations…


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Who's out there?

Drake's Equation

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

Typical lifetime of technological civilizations…


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Who's out there?

Drake's Equation

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



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L ~ 109 yr


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To those everywhere who seek

to make a large number….

-Walter Sullivan

dedication in We are Not Alone (1970)




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