The Origin and possible existence of Life in the

Universe

Do you think there is life even just primitive forms of life on other worlds?

Poll Question:

Do you think there is intelligent life on other worlds?

YES NO UNDECIDED

The Electromagnetic Spectrum

Use a stamp “X” to select the most abundant element in the universe.

neon nitrogen hydrogen oxygen

helium carbon sodium iron

Axis of rotation

Approx. 1 light yearAxis of rotation

Rotation retardscollapse in thisdirection

Slowly spinninginterstellar cloud

Gravity makes cloudshrink. As it shrinks it spinscaster and flattens into adisk with central bulge.

Approx.100 AU

Big Questions in Science

• Where did we come from?

• Are we alone?

Questions about origins:

Other astrobiology questions:

1. How did life on Earth form?

2. Should we expect life on many other worlds?

3. Is life on other worlds like life on Earth?

4. How can we detect life elsewhere?

Poll Question:

What chemical elements were created by the Big

Bang?

The Life Cycle of Stars…

NH3

H2CH4

H2O

Put a stamp on the most abundant element in life on Earth.

neon nitrogen hydrogen oxygen

helium carbon sodium iron

The Most Abundant Chemical Elements in the Universe and in Life

• H• He• O• C• N

In the Universe In Life

• H• • O• C• N

• Life on Earth is carbon-based.• Life on Earth requires liquid water• The amino acids in life are easily

formed.

A few facts about

Life on Earth

Finding Life

• First find planets. One way uses the Doppler Effect.

Another way to find planets is to look for transits.

Kepler

Terrestrial Planet Finder

Signs of Life (not yet possible to detect with current technology)

• Seasonal changes

• Unusual abundances of gases

• Gases produced by life

• Unusual patterns of electromagnetic radiation (e.g., radio or TV broadcasts, the nighttime glow of cities)

Bacterial fossils

3 billion years old on the earth.

Will we find them on Mars or elsewhere?

Records of Life on Earth

Life elsewhere could be similar to any of

These stages, or entirely different.

Current Life Forms

We can study these in detail to get DNA, etc.

Amino Acids: building blocks of life.

Some of these were produced in the lab by Harold Urey out

of primeval gases like methane, ammonia, carbon dioxide--by zapping them with electricity (lightning). (1950s)

Human DNA

Nobody has produced this

artificially or even hopes

to. Too complicated.

50,000 genes.

However, the total makeup

Of a human being requires

More information.

The distance between civilizations in the Milky Way

N=no.

of civilizations.

R=radius of

spherical galaxy

r = average

separation.

4 pi (r/2)2 N

= 4 pi R3/3

implies

r = 2R/N1/3.

The Drake Equation

The Drake Equation• N = N* fp ne fl fi fc fL• N* represents the number of stars in the Milky Way

Galaxy • Question: How many stars are in the Milky Way

Galaxy? • Answer: Current estimates are 100 billion. • fp is the fraction of stars that have planets around them • Question: What percentage of stars have planetary

systems? • Answer: Current estimates range from 20% to 50%. • ne is the number of planets per star that are capable of

sustaining life • Question: For each star that does have a planetary

system, how many planets are capable of sustaining life?

• Answer: Current estimates range from 1 to 5.

The Drake Eqn. continued• N = N* fp ne fl fi fc fL• fl is the fraction of planets in ne where life evolves • Question: On what percentage of the planets that are capable of

sustaining life does life actually evolve? • Answer: Current estimates range from 100% (where life can evolve

it will) down to close to 0%. • fi is the fraction of fl where intelligent life evolves • Question: On the planets where life does evolve, what percentage

evolves intelligent life? • Answer: Estimates range from 100% (intelligence is such a survival

advantage that it will certainly evolve) down to near 0%. • fc is the fraction of fi that communicate • Question: What percentage of intelligent races have the means and

the desire to communicate? • Answer: 10% to 20%

The Drake Eqn. continued• N = N* fp ne fl fi fc fL• fL is fraction of the planet's life during which the

communicating civilizations live • Question: For each civilization that does communicate,

for what fraction of the planet's life does the civilization survive?

• Answer: This is the toughest of the questions. If we take Earth as an example, the expected lifetime of our Sun and the Earth is roughly 10 billion years. So far we've been communicating with radio waves for less than 100 years. How long will our civilization survive? Will we destroy ourselves in a few years like some predict or will we overcome our problems and survive for millennia? If we were destroyed tomorrow the answer to this question would be 1/100,000,000th. If we survive for 10,000 years the answer will be 1/1,000,000th.

• N, the number of communicating civilizations in the galaxy.

SETI—Search for Extraterrestrial Intelligence

Over 30 messages

suspiciously intelligent.

They are using home

computers to scan for

messages.

Mars had ( and has) water.Does it have current life?

Summary

• We have learned an enormous amount about the origins of stars and planets.

• We are just starting to learn about life in the universe.

• These explorations require a team effort involving scientists from many disciplines.

• There is still much more to explore. Students will be able to make discoveries and help us learn even more!

NASA’s Navigator Missions: http://planetquest.jpl.nasa.gov/

Origins Education Forum: http://origins.stsci.edu/

Poll Question:

Do you think there is life even just primitive forms of life on other worlds?

Do you think there is intelligent life on other worlds?

YES NO UNDECIDED