Jayant V. Narlikar

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Searches for Extraterrestrial Life
Jayant V. Narlikar Inter - University Centre for
Astronomy and Astrophysics
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How big is the Cosmos?
The cosmic hierarchy has
The Earth
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How big is the Cosmos?
The cosmic hierarchy has
The Earth
The Solar System
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How big is the Cosmos?
The cosmic hierarchy has
The Earth
The Solar System
The Galaxy
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How big is the Cosmos?
The cosmic hierarchy has
The Earth
The Solar System
The Galaxy
Local group of Galaxies
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How big is the Cosmos?
The cosmic hierarchy has
The Earth
The Solar System
The Galaxy
Local group of Galaxies
Cluster of galaxies
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How big is the Cosmos?
The cosmic hierarchy has
The Earth
The Solar System
The Galaxy
Local group of Galaxies
Cluster of galaxies
Supercluster of galaxies
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Question
There may be around 10 21 stars in the observable
universe Is the Sun alone in hosting life on one
of its planets?
Life as we know it
DNA ? Cells ? ...evolution to more complex forms
Do the basic building blocks exist in space?
Yes!
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Question
There may be around 10 21 stars in the observable
universe Is the Sun alone in hosting life on one
of its planets?
Life as we know it
DNA ? Cells ? ...evolution to more complex forms
Do the basic building blocks exist in space?
Yes!
In giant molecular clouds
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Millimetre wave astronomy has revealed the
existence of molecules in space.
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Molecules in Space This is a partial list to give
flavour only!
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Thus, circumstantial evidence exists to support
the idea of life beyond the Earth
Can we estimate the number of extra-terrestrial
supercivilizations in the Galaxy?
Frank Drake suggested an equation to determine
the answer to this question.
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Drake's equation
N R fs fp ne fl f i
fc L
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Drake's equation
N RfsfpneflfifcL
R Average rate of star formation (stars/year)
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Drake's equation
N RfsfpneflfifcL
R Average rate of star formation (stars/year)
fs Fraction of stars that are good suns
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Drake's equation
N RfsfpneflfifcL
R Average rate of star formation (stars/year)
fs Fraction of stars that are good suns
fp Fraction of good stars with planetary
systems
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Drake's equation
N RfsfpneflfifcL
R Average rate of star formation (stars/year)
fs Fraction of stars that are good suns
fp Fraction of good stars with planetary
systems
ne Number planets per stars within ecoshell
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Drake's equation
N RfsfpneflfifcL
R Average rate of star formation (stars/year)
fs Fraction of stars that are good suns
fp Fraction of good stars with planetary
systems
ne Number planets per stars within ecoshell
fl Fraction of ne on which life develop
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Drake's equation
N RfsfpneflfifcL
R Average rate of star formation (stars/year)
fs Fraction of stars that are good suns
fp Fraction of good stars with planetary
systems
ne Number planets per stars within ecoshell
fl Fraction of ne on which life develop
fi Fraction of living species that develop
intelligence
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Drake's equation
N RfsfpneflfifcL
R Average rate of star formation (stars/year)
fs Fraction of stars that are good suns
fp Fraction of good stars with planetary
systems
ne Number planets per stars within ecoshell
fl Fraction of ne on which life develop
fi Fraction of living species that develop
intelligence
fe Fraction of intelligent species reaching an
electromagnetic communicative phase
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Drake's equation
N RfsfpneflfifcL
R Average rate of star formation (stars/year)
fs Fraction of stars that are good suns
fp Fraction of good stars with planetary
systems
ne Number planets per stars within ecoshell
fl Fraction of ne on which life develop
fi Fraction of living species that develop
intelligence
fe Fraction of intelligent species reaching an
electromagnetic communicative phase
L Lifetime in communicative phase (years)
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The answer depends on estimates for the various
factors made by individuals and varies between 1
and several billions! A middle opinion centres
around a million or so.
N L
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The Extra-Terrestrial Intelligences
How can we search for them?
By sending space-ships?
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The Extra-Terrestrial Intelligences
How can we search for them?
By sending space-ships?
By sending unmanned probes with Information about
us?
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The Extra-Terrestrial Intelligences
How can we search for them?
By sending space-ships?
By sending unmanned probes with Information about
us?
By radio messages?
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The Extra-Terrestrial Intelligences
How can we search for them?
By sending space-ships?
By sending unmanned probes with Information about
us?
By radio messages?
The last method is considered the most practical
for present technology
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The Extra-Terrestrial Intelligences
How can we search for them?
By sending space-ships?
By sending unmanned probes with Information about
us?
By radio messages?
The last method is considered the most practical
for present technology
But it demands patience!
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Hello, I am from Earth speaking. Is anyone out
there ?
8.5 years later
Hello, Greetings from Alpha-Centauri. We read
you loud and clear.
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Search for primitive life-forms
Can cells, bacteria and other micro-organisms be
detected outside the Earth's atmosphere?
Hoyle-Wickramasinghe hypothesis states that
comets can be carriers of micro-organisms in
frozen state which they release on the Earth's
atmosphere if their tails brush it.
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Cometary debris like meteor showers can also
serve to bring the micro-organisms to the upper
parts of the atmosphere.
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From these heights they will gradually descend.
In steady state their distribution with height
can be determined.
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Can we establish that such a population exists?
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ISRO-Cryosampler Experiment
TIFR-Balloon Facility used for flying a balloon
to a height of 41 km.
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ISRO-Cryosampler Experiment
Payload consisted of cryosampler manifold with
fully sterilized steel probes, each with a
capacity of 0.35 litre. Pressure tolerance from
1 micro-bar to 600 bar.
Probes evacuated and cooled to liquid neon
temperature to produce cryopump action with
sterilized valves fitted with opening through
telecommand at specified heights.
Air sucked in at 4 different height windows in
two sets of samples.
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Analysis of the data
Air from each probe passed in a sterile system in
a laminar flow chamber, through two filters
first through 0.45?m and then through 0.22?m
filter.
Probes were stored at 70C temperature before
sample preparation.
8 filters so derived also stored at this
temperature.
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Technique of analysis
0.45?m filter is expected to have trapped
microbial-size particles.
2mm?2mm squares were cut from the filters and
treated with special dyes.
Cationic dyes penetrate the membranes of viable
cells. These give rise to fluorescent spots when
illuminated by UV-light and could be identified
with epifluoroscence microscope, or by a confocal
scanning laser microscope
Anionic dyes penetrate only the non-viable cells.
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Cataionic cyanine dye treated samples showed
fuorescent spots in the form of clumps of size
0.3 1 ?m sized cells over areas measuring 5-15
microns across.
Confocal microscopy provides higher resolution
pictures.
Anionic dyes showed a comparable detection rate
of dead or non-viable cells.
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Serendipitous Discovery of Culture
Milton Wainwright from Sheffield obtained
cultures from a medium in the form of Potato
Dextrose Agar (PDA).
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Serendipitous Discovery of Culture
Taking every possible precaution against
contamination, cultures of the following
microorganisms were grown
(a) The coccus (spherical bacterium, often
growing in clumps) 99.8 similar to the
bacterium Straphylococcus pasteuri, as
determined by 16S RNA analysis.
(b) The bacillus (rod-like), 100 similar
as determined by the above analysis to the
the Bacillus simplex.
(c) A fungus identified as Engyodontium
albus (Limber) d e Hoog.
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These are not common contaminants, nor had they
been used in the lab where these were found. No
such growth was found on control membranes that
were not exposed to stratospheric air.
If these micro-organisms are not from the Earth,
then
Have we detected extraterrestrial life?
Further confirmatory work is in progress
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