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Extraterrestrial Life: where??
Do you like
This lady?
Is she beautiful?
Beautiful is relative?
My name: Mounib El Eid
‫منيب العيد‬
Department of Physics
Living organisms at the bottom of the Gulf of Mexico . High pressure and low
temperature cause the gas Methane to become solid (yellow in the Figure). The
pink color are eyeless alien-looking worms .
If life flourish under these extreme conditions, there is good
reason ti believe that it can flourish in other worlds
Stimulation & messages to thhe audience
With the help of Astronomy, we try to understand how we fit into the universe.
Tens of thousands of past human generations have walked this Earth.
Ours is the first generation with technology to study the far reaches of the
universe and to search for life elsewhere and to travel beyond our planet.
It is up to us to decide whether we will use this technology to advance
our species or to destroy it.
Just imagine our descendants joining other civilizations.
Perhaps, in their history lessons, they will learn of our generation—the
generation that history will placed at the turning point and that managed to steer
its way past the dangers of self-destruction and onto the path to the stars
Certainly not systems like in North Korea (or near to us) are meant in this
connection
I never understood why people make war, if they are able to discover the beauty
of love!
One of the most compelling questions in science is:one of the simplest:
Are we alone?
Does life exists beyond the Earth?
Suppose you visit an alien planet. How do you find which object is living and which
inanimate ( ‫?(غير حي‬
This is a question to Astrobiology
The assumption is: if we find living organisms on other worlds, they will be
carbon-based as we are
But why carbon?
Answer: carbon has the most versatile ( versatile : multi-useable). Carbon can form
chemical bonds to create complex molecules like Glucose or Alanine
The statement is:
H
extraterrestrial life is
|
likely based on organic
H—N—C—C—O—H
chemistry
|
H--C--H
|
H
Alanine (amino acid)
Organic molecules are found in interstellar medium like:
ethyl alcohol
CH3 CH 2OH
formaldehyde (formaldeheid) H2 CO
acetaldehyde
CH3 CHO
methylcyanoacetylene
CH3 C3N
carbon monoxide
CO
If life is based on organic molecules, then these molecules must be present on a
planet to make life possible.
Indeed, evidence for this comes form meteorites (‫)النيازك‬, called
carbonaceous chondrides
Also the comets ( ‫ )المذنب‬the
oldest objects in the solar
system contain organic
compounds.
Allende meteorites Fell in Mexico 1969
Meteorites and comets were
more numerous in the early
solar system and were more
likely to collide with a planet
and would have delivered
organic material to the planet. .
Why Silicon unsuitable for making living organisms ‫لماذا سيليكون غير صالح لتكوين الحياة‬
Answer: compound s of silicone either too soft or too hard
Gel: silicon with oxygen
Silicon-carbon-oxygen
like quartz
Miller-Urey Experiment
In 1952, two American chemists prepared in a
closed a primitive atmosphere which was
exposed to electric arc (like lightening) for one
week. They could produce substance rich
in amino acids essential to life.
We learn from this experiment that
 life could have been originated from
chemical processes
 Since the molecules are common, it is
reasonable to conclude that life has
originated in the same way on other planets
“atmosphere” prepared as shown with
water vapor (most common molecule in
the solar system) was subject to electric
arc.
CAUTION !
Scientists have not created life in the a tube. Biologists have to yet figure out how
complex molecules collected themselves into cells and developed systems of
self-reproduction .
But because chemical components of life are easily synthesized under conditions
that simulate the early Earth, it seems reasonable to assume that
life has originated as a result of chemical processes
Another insight: since the molecules that form the compounds are common, it is
reasonable to assume that life has originated in the same way on other planets
Conclusion:
it seems all living organisms have common chemical origin
‫كل الكائنات الحية لها تكوين كيمائي مشترك‬
We also can say:
Chemical evolution preceded biological evolution
‫التطور الكيميأئي سبق التطور البيولوجي‬
Importance of liquid water
Essential for the survival of life . It should not be always pleasant for drinking or
taking a shower.
Terrestrial organisms have been found in boiling water or ice cold. But it must be
liquid which means the temperature cannot be too high or too low. In addition to
have water on a planet’s surface, a thick atmosphere must exist.
The atmospheric pressure prevents the evaporation of the water.
Our Earth has these conditions- we are lucky !!
However, there is now evidence that the satellite Europa of Jupiter has an ocean
beneath its icy surface
Conclusion:
We have to look for planets with atmospheres if we search for extraterrestrial life
Interesting Data
Age
(Million of years)
2-4
life
Homo Sapiens appear
58
mammals
63
End of Dinosaurs
239
Dinosaurs appear
460
First fishes
4600
Earth formation
4.6 billion years
Another Amazing Table
Imagine the entire life of Earth to be 46 years (rather than 4.6 billion years).
35 years ago
life originated when Earth was about 10 years old (no record before)
6 years ago
life in oceans
4 years ago
life ashore
1 year ago
4 months ago
Dinosaurs appeared
Dinosaurs died
4 hours ago
1 hour ago
homo sapiens
agricultures was invented
3 minutes ago modern science
Couple of hours
between these
two
How did life arise on Earth?
History of life is based o the theory of evolution proposed by Charles Darwin
Evolution means changing with time . But how do species undergo change
Darwin theory says:
Evolution proceeds through a process of natural selection.
This means: nature select the advantageous track for survival. This is why the
process is called “natural”.
Some 150 years of research has supported this view of Darwin
The strongest support comes from the discovery of the DNA.
The DNA is the genetic material of all life.
Living organisms reproduce by copying DNA
What is a DNA ? See next
The DNA (deoxyribonucleic)
DNA consists of two long spiral-like
strands, or double helix . There are 4
chemical bases labeled by letter:
A, T, G ,C
T attaches to A
C attaches to G
Fig. 18.5
Cosmic
perspective
A=Alanine)
Evolution
occurs because passing of
genetic information from one generation
to another is not always perfect. Any
change in DNA is called mutation ( ‫)تغير‬
Mutation and Evolution
characterize life
‫الحياة تتميز باالتغير والتطور‬
T to A
C to G
DNA molecule. Hereditary (‫)وراثي‬
information is contained in the teeth linking
the strands. The teeth are the DNA bases.
The bases are linked as mentioned above:
T attaches to A
C attaches to G
The colors have no meaning
What is life
In all the previous discussion we did not define what life is.
Here are some characterizes
Order
reproduction
Evolution
Growth
Response to environment
Life is a process that can reproduce and evolve through selection
Biologists regard evolutionary adaptation is the only property that explains
diversity of life at least on Earth
However: computer scientists can create “artificial life” on computer. Is this to be
considered alive? With our definition: yes -- a problem indeed
Necessities of Life
What does Erath life need to survive?
 We need abundant oxygen in the atmosphere
 We need temperature in a narrow range a variety of food sources
Summary: life needs
Nutrients ( ‫)مواد مغذية‬
Energy
( ‫) طاقة‬
Liquid water ( ‫)مياه سأئلة‬
Liquid water seems to be the main problem in other worlds
Are habitable planets likely
This question is related to another one: how many stars could have planets
with life.
First requirement
for a star to have life-bearing worlds is that it
 To be old that life could have arisen.
 Stars of large masses live shorter.
Stars of low mass (less than the Sun) are too dim to support life.
You see how important thye theory of stellar evolution is.
Second requirement
stars have to allow planets with stable orbits
Third requirement:
size of the star’s habitable zone
the region in which a terrestrial planet could have a surface temperature that
allowed liquid water to exist
habitable planets
Solid surface
Enough
gravity to
retain
atmosphere
Comfortable
distance from
the star
Stable orbit,
nearly
circular ,
because
highly
elliptical orbit
has strong
temperature
variation
Venus
Earth
(1/10 ) M Sun
½ M Sun
Habitable zones around the Sun.
A star ½ the mass of the Sun and 1/10
the mass of the Sun have much smaller
habitable zones and closer to the star
If we could make similar spectral
analyses we might have
indication for life
Mars
Infrared spectra of Venus, Earth and
Mars showing absorption features
that point to the presence of carbon
dioxide (CO2) , Ozone (O3) and
sulfuric acid (H2 SO4) in their
atmospheres. While CO2 present in
all spectra , only our planet has
Ozone as a consequence of
photosynthesis
Finding Earth-like planets Infrared telescope called Darwin (to be launched 2018
by the ESA=European Space Agency)
Spectrum ( ‫ ) الطيف الضوئي‬of a simulated planet . On the left is simulation
of what the terrestrial planet finder infrared telescope Kepler might see. The
spot in the middle is Sunlike star and the small dots are planets orbiting the
star. On the right, the absorption lines indicate H2O, CO2 and O3. Presence
of life will change the relative amounts of each molecule
7. Spectroscopy reveals composition of planets and moons
This is real art !!
If a planet has an atmosphere, then sunlight reflected from the planet
must have passed through its atmosphere.
Some of the wavelengths will have been absorbed depending on the
composition of the atmosphere.
Interesting is the largest satellite of Saturn:
Titan (‫(الجبار‬
The spectrum of visible sunlight
reflected from Titan is shown in the
Figure .
The absorption lines are shown by
the dips in the curve.
But not all of these lines are produced in
the atmosphere of Titan
The reason is that the sunlight has passed
through the Sun’s hydrogen-rich
atmosphere before it was reflected by
from the Titan atmosphere. This is seen at
the wavelength 656 nm
The light after being reflected from Titan,
enters the Earth’s atmosphere before
reaching the telescope. where the oxygen
absorption line is formed .
Only the two lines at 620 nm and 730
nm are caused by absorptions in the
Titan atmosphere. This is due to the
presence of methane CH4 .
Titan is is a curious place indeed ,
because CH4 is a natural gas on
Earth.
In addition, the UV spectra from Titan
reveals existence of N2 molecules
and the infrared spectra show that
Carbon and Hydrogen are present.
Titan has complex atmosphere indeed.
May be life will develop there one
day.
8. Extrasolar Planets
It is very difficult to make direct observations of planets orbiting other stars,
because planets are small and dim compared with stars at visible wavelengths.
The Sun is 109 times brighter than Jupiter and 1010 times brighter than the Earth.
Therefore, no hope to observe planets
directly orbiting stars
Well, we may use indirect methods
Large planets, like Jupiter: their gravitationally
pull on their central star causing the star to
move in a small orbit about the center of mass
Planets orbiting other stars are called
extrasolar planets
Or Exoplanets
Astronomers carefully measure the
motion of a star with a planet
orbiting it by looking at the
starlight.
Such a star has starlight that is
alternately red shifted and blue
shifted.
To date, more than 100 extrasolar
planets have been discovered
using this method of looking for
Doppler shifts.
Planet transit
http://www.astroevents.no/lifesearch.html.
Analyzing g Extrasolar Planets with the transit method
The transit method looks for the rare situation
in which the planet comes between us and the
parent star.
Amount of
dimming of
the star’s light
by the planet,
tells us about
the diameter
of the planet
With infrared telescope, it is possible to detect a slight dimming (deeming) when the
planet goes behind the star .The infrared radiation of the planet due to its surface
temperature is blocked , and this tells about its surface temperature
During transit,
the star’s light
passes through
the planet’s
atmosphere.
Certain
wavelengths
are absorbed
there. We get
information
about the
composition of
the planet’s
atmosphere.
Example:
The planet orbiting the star HD 209458 is 153 light years away from the Sun.
The planet has amass of 0.69 that of Jupiter, but its diameter is 1.32 times larger than
that of Jupiter.
The planet orbit is 0.047 AU from the star and is very hot : surface temperature of
1130 K.
Search for Earth-sized Planets
Very difficult to find. such planets. Attempts to proceed in this direction are the
following
1. NASA and ESA (European Space Agency) launched in 2009 the KEPLER 1-m
telescope to search for transits of Earth-like planets
Gaia
2. ESA project called
will be launched in 2013. It will survey 109 stars or
about 1% of the stars in the Galaxy. The expectation is to find 10,000 to 50,000
Jupiter-sized planets.
The question still open: is our solar system an exception or rather common?
The Fermi Paradox
Life in the universe , p. 455
He says: neither we nor our planet should be special.. Or othe civilization
may exist capable of space travel
Is there a civilization who has colonized the galaxy already?
The paradox is that we face two contradictory ideas:
We rare not special
We should be surrounded by evidence of these civilizations, but we have no
idea yet how to find them.
This is interesting: if they are somewhere, then then, the should have arisen long
before we came to the scene.
We know the universe is about 14 billion years old, but the Earth is “only” about 4.5
billion years old. So we have an interval of 9.5 billion years before the formation of
the solar system.
Now, since stars were formed early on in the universe and elements Carbon
and beyond are formed in stars , it is likely to have Earth-like planets within
few billion years of the universe’s birth.
It is reasonable to say that Earth-like planets started to be formed about 5 billion
years before our own planet was born, about the age of the galaxy.
So, 5 billion years ahead . If intelligent life needed 5 billion years like ours, then they
have appeared 5 billion years ahead of us.
But what can we say about the number of these civilizations?
Let us play LOTTO:
One in one million stars would have a planet Earth-like and with intelligent life.
In the Galaxy, we have1011 stars , or we would have 100,000 civilizations in the
Galaxy by now.
This is astonishing, especially if we say that these civilizations have arisen at
random times during 5 billion years, then on the average a civilization arises every
5x109 /100000=50,000 years
Think about this estimation:
1. Even with 1 civilization for 1 million stars, we have 100,000 civilizations that
arose before we came on the galactic scene
2. We re then then youngest civilization, and the next youngest civilization has
arisen 50,000 years ago and the third 100,000 etc….
3. Even if we take 1 civilization in 100 million stars, we still have 1000
civilizations that would have arisen over the past 5 billion years and the
average would be one per 5 million years.
Now, you have a feeling why Fermi asked:
where is everybody?
Well, if we would meet with them, they will laugh at our technological achievements.
Certainly there will not have 6 hours and more cut in electricity as we are enjoying in
the high-tech country “ the Cedar Land” , Halleluiah
Instead of trying to resolve the Fermi paradox, let us reflect on its implications.
1. We are alone (Lasamah Allah) .
Then our civilization is a remarkable
achievement. At least we were the first civilization to know that the universe
exists We are self-aware then, and that gives us a philosophical sense of life, If
so, then the destruction of our civilization with all scientific knowledge would put
an end to an achievement that took 14 billion years to come out., and this would
be tragic indeed.
The message to the “unique species”: put all wars behind us, protect our
environments and respect each other
2. Civilizations are common, but no one has colonized the Ga
This has terrifying implication : the are ahead of us and did not succeed to make
space travel . What hope do we have then?
Message here: hopefully this answer is wrong
3. Most intriguing: we are newcomer on the galactic scene
Why they are leaving us alone or we are not yet able to find them. In this
respect we are like a baby growing and have to learn how to walk.
The message We have the ability to destroy our own civilization. If we do so,
then our fate is sealed. But if we survive, long enough then we may develop
technologies that can take us to the stars
I am back to the stimulating words at beginning of this lecture.
Search for Extraterrestrial Intelligence (SETI)
This search program has a special aim to find evidence for technologically
advanced life. If this would be successful, life would not be unique on Earth
But what is the probability of finding a signal from
outside?.What are the factors influencing this probability
These factors are summarized in the so called
Drake equation
Fraction of
those
species that
develop
adequate
technology
Lifetime of
technologically
advanced
civilization
N  R* f P ne f l f i f c L
Number of
civilizations
capable of
interstellar
communication
Rate at
which
solar-type
stars form
in the
galaxy
Fraction
of stars
that
have
planets
Number
of planets
per solar
system
suitable
for life:
Earth-like
Fraction
of Earthlike
planets
on which
life
arises
Fraction of
those life
forms that
evolve into
intelligent
species
How to estimate these numbers?
First two factors: R*, f P
Estimate of R* should exclude stars of masses greater than 1.5 solar
masses,.
Reason: these stars live only about 3x109 years not long enough to let live
like ours develop. Stars less than one solar mass are so dim so that planets
should be very close. They will then behave like our Moon in synchronous
rotation showing one face to the star, the other face in frigid darkness.
Conclusion: we need solar-like stars and the estimation of the Astronomer is:
R*  1 / year
And most likely, most solar-like stars have planets, so
f P =1
Remaining terms are very uncertain
Let us play the cosmic game:
If our solar system is typical, then
But, let us be conservative and take
ne  1
1
ne 
10
One in 10 sola-like stars has
habitable planet
Then:
fl  1
Meaning that the development of life is a certainty. Well this is a question to
Astrobioligists
We might also assume that evolution might lead the development of intelligent
life, which makes
fi  1
(matter of debate !)
Having the intelligent beings, it is reasonable to assume that they wiil try to
communicate. In other words, we put
fc  1
Last variable: L
Most uncertain of all.
Looking at our example, we see a planet whose atmosphere and oceans
are systematically polluted by creatures that posses nuclear weapons.
If we were typical (L’samahallah), we might take L=100 years
Putting all together;
N  R* f P ne f l f i f c L
1
1
N 
 1
1 11 100  10
year
10
Amazing: out of 100 billions of stars in the Galaxy, there are 10
civilizations of advanced technology
Well: keep watching the sky
Radio Search for other civilizations
“Water Hole”
Bounded by 21 cm
wavelength (H),
and 18 cm (OH)
Universe 9th, p. 757
Oasis for Alien
communication
Background noise level of the sky at various radio and microwave
frequencies. The so called water hole is a range of radio frequencies 103
to 104 MHz where little noise exists. This is a window of interstellar
communactions
Noisy Earth
Periodic blasts of
radiation could be
registered as fare as
70 light years
Daily activities of our technological civilization. FM and TV transmitter
broadcast their energy parallel to the Earth’s surface. AM signals \are
trapped below the ionosphere
Aliens would register North America and Western Europe signals
Starship design: future imagination
Orion starship
Small hydrogen bomb
detonations that would
propel the spaceship
Min al?
To Alpha centaury in 100
years?
This is an exciting field of research for young physicists and Engineers
This spaceship would
collect interstellar
hydrogen and use it as
fuel
Very difficult, because
hydrogen in interstellar
space is rare
You can find aliens: join SETI
www.seti.org
You can participate on the search
Another webpage:
www.lifeinuniverse.org
Planet transit
http://www.astroevents.no/lifesearch.html.
Finally, some nice words
‫كالم جميل‬
The scientists does not study nature because it is useful;
he/she studies it because he delights in it, and he/she delights
in it because it is beautiful. If nature were not beautiful, it would
not be worth knowing, and if nature were not worth knowing,
life would not be worth living.
Guess who said that:
Henry Poincare
‫العالم اليدرس الطبيعة ألنها مفيدة بل ألنه يجد متعة بجمالها‬
‫لو كانت الطبيعة غير جميلة ليس من متعة في معرفتها‬
‫وأن لم نكن نتوق لمعرفة الطبيعة فما هو معنى الحياة‬
My translation
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