Life in the Universe

Conditions may be right for primitive life to exist on Mars (or existed in the past) and Europa. Possibly some complex molecules on Titan.

Elsewhere in the Solar System:

Is There Life Elsewhere in the Universe?

Water flow on Mars inlast few years?

To address question of whether other intelligent life exists in the Milky Way, Frank Drake formulated the Drake Equation.

Life Elsewhere in the Milky Way:

The equation is usually written:

N = R* • fp • ne • fl • fi • fc • L

Where,

N = The number of civilizations in The Milky Way Galaxy whose electromagnetic emissions are detectable.R* =The rate of formation of stars suitable for the development of intelligent life.fp = The fraction of those stars with planetary systems.ne = The number of planets, per solar system, with an environment suitable for life.fl = The fraction of suitable planets on which life actually appears.fi = The fraction of life bearing planets on which intelligent life emerges.fc = The fraction of civilizations that develop a technology that releases detectable signs of their existence into space.L = The length of time such civilizations release detectable signals into space.

The Drake Equation

number of technological, intelligent civilizations in the Milky Way

rate at which new stars are formed= x

fraction of stars having planetary systems

x

average number of habitable planets within those planetary systems

xfraction of those habitable planets on which life arises

xfraction of those life-bearing planets on which intelligence evolves

fraction of those planets with intelligent life that develop technological society

average lifetime of a technological civilization

xx

Each term is less certain than the preceding one! Only in last ten years have we addressed the second term.

Allen Telescope Array – radio SETI

Optical SETI [Harvard U.]

SETI League(Amateur Radio Astronomers)

Extrasolar PlanetsMore than 300 discovered.

Main technique: detect Doppler Shift due to wobble of star caused by unseen planet. Biased – easier to detect heavier (Jupiter-class) planets.

Second technique: detect eclipse (transit) of planet – Kepler mission.

Third technique: detect wobble in star's position in sky due to unseen planet (astrometric method).

Fourth technique: direct imaging of planet.

Fifth technique: microlensingFuture missions hope to detectTerrestrial planets

http://planetquest.jpl.nasa.gov/science/finding_planets.cfm

Astrometric method

Candidates detected by

radial velocity or astrometry 397 planetary systems 471 planets 47 multiple planet systems Transiting planets 105 planetary systems 107 planets 7 multiple planet systems

microlensing 10 planetary systems 11 planets 1 multiple planet systems

imaging 11 planetary systems 14 planets 1 multiple planet systems

506 exoplanets detected as of 6 Dec 2010

http://exoplanet.eu

9

Terrestrial Planet Finder (TPF) Mission

Image courtesy NASA/JPL

• TPF Science goals– Survey stars within ~ 30 pc for planets within “habitable zone”

• Looking for “Earth analogues”– Characterize any detected planets

• Orbit & Spectrum

• Past, current, future TPF studies– Two main designs possible– Preliminary concept studies underway for several years– Followed eventually by “Life Finder” and “Planet Imager”

Detecting Terrestrial Planets Directly is HARDBrightness differences make this a very tough problem

0.1 1 10 100 1 1031 10

14

1 1013

1 1012

1 1011

1 1010

1 109

1 108

1 107

1 106

1 105

1 104

1 103

0.01

0.1

1

10

10058.21

4.411 1014

SunSpec

ER10pcQ

Exozody

ERtotal

1 1030.303 wavelen

star

planet(reflection)

Zodiacal dust(reflection + emission)

planet+dusttotal

(log

sca

le)

wavelength [microns]

100m

Non-redundant Linear Array (NRLA) [Hypertelescope]

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Roddier-Guyon Synthesis ImagerEarth-Sun system at 10pc

2.7h exposure time, 5 to 15 m

Exoplanets Seen Through an Advanced Space Telescopes

Kepler Mission – Extrasolar planet transits from space

http://kepler.nasa.gov/

• 700 candidate planets found0.077 to 2.1 Jupiter masses (note, Earth = 0.003 Jupiter masses)

• 8 confirmed new planets

Kepler Mission – Extrasolar planet transits from space

Is There Life Elsewhere in the Universe?

- Elements to build cells (C, H, O most important)

- Energy source to make chemical reactions happen to fuelmetabolism

- Liquid medium – water allows organic (C-based) molecules to dissolve and be carried into cells for metabolic reactions

Requirements for Life:

These conditions occurred on Earth, but it's not clear whether life was then inevitable. Also, how unique are they?

Urey-Miller Experiment (1953)

Solution of water, methane, CO2, ammonia, with electrical discharge

=> amino acids formed (building blocks of proteins, which control metabolism

Alternative theory:

Organic molecules, maybe even amino acids and nucleotide bases came from comets and meteoroids (a lot of Earth's water may have come from comets)

Later experiments produced nucleotide bases (building blocks of DNA)

Yet to make cell or DNA through such experiments (although some cell-like objects created from mixing amino acids and heat). Not clear how robust life is and whether it required a fortunate set of accidents.