Steven PrinsenDan Cipera

Mat RemillardMark Johnson

What Is Life? The Search Within Our Solar System Searching Beyond the Solar System Probability of Life

Broad definition• “The period between birth and death”• “The sum of all activities of a plant or an

animal” “Activities”

• Respiration• Reproduction• Nutrition• Excretion• Locomotion• Growth• Reaction to stimuli

Quartz Lifelike

Growth Nutrition Reproduce?

Not Lifelike Movement Excretions External Stimuli www.howstuffworks.com/quartz-watch.htm

• Fire– Lifelike

• Respiration• Growth• Movement• Reproduction• Eats• Excretes• Reacts to stimuli

– Not Lifelike• Evolving• Adaption to change

www.funsci.com/fun3_en/fire/fire.htm

Life Growth Reproduce Adapt Evolve

http://www.hickerphoto.com/rain-forest-streams-9157-pictures.htm

• 95% of Life– Hydrogen, Oxygen, Carbon, Nitrogen

• Last 5%– Calcium, Phosphorus, Chlorine, Sulfur,

Potassium, Sodium, Magnesium, Iodine, Iron, and trace elements

• Most abundant universal elements– Hydrogen, Oxygen, Carbon, Nitrogen– Helium, Neon

• Most abundant earth elements– Silicon, Iron, Magnesium, Oxygen

The Search For Life In The Universe, Goldsmith and Owen

• Carbon– Complex molecules– Nitrogen and Oxygen

• Monomers– Small molecules– Compose polymers– Amino Acids, sugars, fatty acids, nucleotides

• Polymers– More complex molecules– Proteins

Laevorotatory (L) vs Dextrorotatory (D) Non living material is 50/50 L configuration

Amino Acids D configuration

Sugars, DNA, RNA Increases efficiency

Amino Acids 20 used 100 per protein 20100 possible combinations

Astrobiology, November 10, 2008.

Meteorites L-amino acids 16% excess

Astrobiology, November 10, 2008.

Nucleotides Four types

A, T, G, C Specify Amino Acids 16 combinations

Sets of Three 64 combinations Redundancies Prevents mistakes

http://yihongs-research.blogspot.com/2008/09/new-generation-business-demands-new-dna.html

• Molecular level– DNA Mutation

• Gamma Rays• Cosmic Rays• Mutagens

– Changes reproductive efficiency• Energy

– From the Sun– Photosynthesis

Sunlight Steady energy

Key to survival 3.5 billion years

Photosynthesis Ensures a chance to survive

http://photo.net/photodb/photo?photo_id=3666216

Formed by accretion Hydrogen Reducing

Methane Ammonia Water Vapor

Resembles Jupiter and Saturn Left quickly Volatile elements joined earth last

H, C, N, O Life elements Comets

http://www.williamsclass.com/EighthScienceWork/Atmosphere/EarthsAtmosphere.htm

Hydrogen bound to Oxygen UV breaks up

Photodissociation Made new compounds

Chem Reactions with crust Mildly Reducing

CO CO2

N2

H2O H, H2

Mars, Venus

Astrobiology, Monica Grady

Water doesn’t imply life May be able to detect atmosphere data

Transiting planets Nonequilibrium reaction byproducts

Free Oxygen Photosynthesis

Terrestrial SimilaritiesM ≈ 1 Earth MassIron Core -> Magnetic FieldOrbit and Rotation

The 4 Most Vital Elements for LifeCarbon, Hydrogen, Oxygen, Nitrogen

Liquid Water!

Europa Galileo Missions Slightly smaller than our

moon Silicate Rock – Iron Core Atmosphere of Oxygen Smooth, icy surface Oceans Underneath?

Extremophiles?

Titan Cassini-Huygens

Mission 50% Larger than our moon Surface of water ice and

organic compounds Thick Atmosphere of Nitrogen Liquid Hydrocarbon Lakes

(Ethane and Methane)

But... -290 F (-179C)

Mariner ProbesNo Plate TectonicsNo Global Magnetic FieldAtmospheric Pressure roughly 1% of Earth'sNo liquid water on surface

… No multicellular organisms

Viking Landers Search for bacteria-like

organisms Soil showed C02

production when interacted with water

No organic molecules detected

Phoenix Lander (May 25 2008)

Water-ice in Martian subsurfaceSmall concentrations of salts

Mars Reconnaissance Orbiter (November 20,

2008) Vast glaciers of iceEvidence of a previously

“wet” Mars

Planned Missions Mars Science

Laboratory (2009) Maven (2013)

Other Proposals Mars Sample Return Astrobiology Field Lab Deep-Drill Lander

Idea is to Identify “Earth-like” planets- rocky worlds similar to our own

Very difficult- most exoplanets we’ve found thus far are gas giants the size of Jupiter

Planet’s gravity affects it’s parent star- causes slight variations in star’s radial velocity

These variations are detectable by measuring Doppler shifts (i.e. a spectrograph measuring Doppler shifts in spectral lines from a star)

Current instruments can detect ~1 m/sec shift; problem is, Earth-size planets induce ~0.1 m/sec shift

Also, can only tell mass- not diameter/ composition/ atmosphere/ etc.

HARPS 3.6 m telescope

(www.eso.org)

As planet transits in front of sun, dip in luminosity is recorded

Technique can be used to determine diameter and mass, thus giving a density

Orbit must lie in correct plane

Period must be sufficiently short, or telescope must observe star continuously for a longer time

www.space.com

Best way to determine a planet’s chemical make-up (analyzing spectral lines)

Fomalhault b was first exoplanet to be directly imaged visually - HST

Problem: for most stars, luminosity from star far outshines reflection from planet

Also, Earth’s atmosphere both narrows observable frequency ranges and causes blurring/seeing of visible light

Fomalhault b

www.spacetelescope.org

Space-based telescopes (Hubble, Kepler, TPF) negate the atmosphere problem

The light problem is much trickier (for example, at 10 pc, angular separation for 1 A.U. is 100 marcseconds)

To block out the light from the star, a coronagraph is needed

Kepler Space Telescopewww.seti-inst.edu

Possible designs for the Terrestrial Planet Finder

satellites

planetquest.jpl.nasa.gov

Ratio of Sun’s Luminosity to light reflected from Earth

-Lsun= 4e33 erg/sec-1 AU= 1.5e13 cm-Earth’s radius= 6.4e8 cm-Earth’s Albedo= 0.367

Flux from the sun to Earth:

26213

33

2sun erg/sec/cm101.4)104ππ(1.

104

4ππ

LF

“Luminosity” of Earth

sec/106.6)104.1()104.6)(14.3(367.0

))((23628

2

erg

FrL sunEEarth

Ratio

1033

23

107.1

1

104

106.6

Sun

Earth

L

L (About 1 in 20 Billion)

Occulter: part of a coronagraph that physically blocks light from a star

Problems: lower resolution, diffraction effects still obscure planet

New Worlds Mission- use a distant occulter to block star’s light

Geometry of occulter can be modified to “smooth out” diffraction rings

Occulter can also be “apodized”- modified to help offset diffraction effects

New Worlds Mission Concept

www.planetquest.jpl.nasa.gov

Chemical Composition- Water, Oxygen, Ozone, CO2

Can determine through spectral analysis

“Red Edge”- Chlorophyll in plants reflects in infrared

Changes in reflectivity

If a star passes in front of a background star, the gravity of the foreground star causes microlensing

The presence of a planet orbiting the foreground star affects the observable microlensing

This effect can be observed even with planets at Earth’s scale

Correct alignment is very rare, and only observable for a few days/weeks

An equation postulated by Dr. Frank D. Drake in 1961.

The Drake equation in it’s original form:

N*= Total stars in galaxy fs = sun-like stars (fraction)

fp = stars with planets (fraction) fi = planets with life (fraction)

ne = life supportable planets

fc = planets with intelligence (fraction)

fl = life time of communicative civilization (fraction)

Dr. Frank Drake

Galaxy Factors

Solar System Factors

“Earth” Factors

Wild Cards

Galaxy Factors

Type of galaxy Enough heavy elements Not small, irregular or elliptical

Position in galaxy Not positioned in the halo, edge, or center

Solar System Factors Stable planetary mass

Giant planets allow for orbital stability

Jupiter-like neighbor Absorbs comets and asteroids

A Mars Possible life source

Large Moon Stabilizes tilt

Right Mass of star Right amount of ultraviolet released Long enough lifetime

“Earth” Factors

Distance from star Habitat for complex

life Liquid water near

surface No tidal lock

Planetary mass Solid/molten core Enough heat for plate

tectonics Able to support

atmosphere and ocean Tilt

Mild seasons

Oceans’ size Sufficient amount

Atmospheric properties Adequate temperature Right composition and

pressure Carbon amount

Enough for life but not enough for runaway greenhouse effect

Oxygen Evolution Development of

photosynthesis Biological evolution

Complex plants and animals

“Earth” Factors Giant impacts

Few giant impacts No major sterilizing

impacts

Wild Cards Inertial interchange

event Snowball Earth Cambrian explosion

Plate tectonics Land mass creation Biotic diversity Silicate thermostat Magnetic field

An equation suggested by Professor Peter Ward and Professor Donald Brownlee from their book “Rare Earth”:

N*= Total stars in galaxy fc = planets with complex life (fraction)

fp = stars with planets (fraction) fi = planets with life (fraction)fpm = metal-rich planets (fraction) fm= planets with large moon

(fraction)ne = life supportable planets fj = Jupiter-sized planets

(fraction)ng = stars in habitable zone fme = low number of mass destruction events (fraction)fl = life time of complex life (fraction)

Drake Equation with Dr. Drake’s current estimation of intelligent life in our galaxy:

Rare Earth Equation with our estimation of intelligent life in our galaxy:

The Point:

If any of these many variables approach zero, the total will be near zero!

“I'll tell you one thing about the universe, though. The universe is a pretty big place. It's bigger than anything anyone has ever dreamed of before. So if it's just us... seems like an awful waste of space”.

-Ellie Arroway, Contact

“…And pray that there's intelligent life somewhere up in space, -'Cause there's bugger-all down here on Earth”.

-Monty Python and the Meaning of Life

What Is Life? The Search Within Our Solar System Searching Beyond the Solar System Probability of Life

Astrobiology, Monica Grady, The Natural History Museum, London, 2001

 The Search For Life In The Universe, 2nd Edition, Goldsmith and Owen, Addison-Wesley Publishing Company, 1992

A Race To Find Alien Planets, Carlisle, Sky & Telescope, January 2009, p28.

Circular Polarization and the Origin of Biomolecular Homochirality, Bailey, Bioastronomy, 1999

On the Origins of Biological Homochirality, Sandra Pizzarello, Astrobiology, November 10, 2008.

www.nasa.gov Rare Earth, Ward, Brownlee, Springer Science, 2000 Titan: Earth in Deep Freeze, Barnes, Sky & Telescope,

December 2008 Are We Alone, Imaging Extrasolar Earthlike Planets from

Space, Presentation by Prof. N. Jeremy Kasdin David J. Des Marais et al. “The NASA Astrobiology Roadmap.”

9 Oct 2008. 19 Oct 2008