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Searches for Extraterrestrial Life
Jayant V. Narlikar
Inter - University Centre for Astronomy and
Astrophysics
How big is the Cosmos?
The cosmic hierarchy has:
The Earth
How big is the Cosmos?
The cosmic hierarchy has:
The Earth
The Solar System
How big is the Cosmos?
The cosmic hierarchy has:
The Earth
The Solar System
The Galaxy
How big is the Cosmos?
The cosmic hierarchy has:
The Earth
The Solar System
The Galaxy
Local group of Galaxies
How big is the Cosmos?
The cosmic hierarchy has:
The Earth
The Solar System
The Galaxy
Local group of Galaxies
Cluster of galaxies
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
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!
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…
Millimetre wave astronomy has revealed the existence of
molecules in space.
Molecules in Space
This is a partial list to give flavour only!
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.
Drake's equation:
N= R * fs * fp * ne * fl * f i* fc * L
Drake's equation:
N= R*fs*fp*ne*fl*fi*fc*L
R = Average rate of star formation (stars/year)
Drake's equation:
N= R*fs*fp*ne*fl*fi*fc*L
R = Average rate of star formation (stars/year)
fs = Fraction of stars that are ‘good’ suns
Drake's equation:
N= R*fs*fp*ne*fl*fi*fc*L
R = Average rate of star formation (stars/year)
fs = Fraction of stars that are ‘good’ suns
fp = Fraction of good stars with planetary systems
Drake's equation:
N= R*fs*fp*ne*fl*fi*fc*L
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
Drake's equation:
N= R*fs*fp*ne*fl*fi*fc*L
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
Drake's equation:
N= R*fs*fp*ne*fl*fi*fc*L
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
Drake's equation:
N= R*fs*fp*ne*fl*fi*fc*L
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
Drake's equation:
N= R*fs*fp*ne*fl*fi*fc*L
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)
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
The Extra-Terrestrial Intelligences;
How can we search for them?
By sending space-ships?
The Extra-Terrestrial Intelligences;
How can we search for them?
By sending space-ships?
By sending unmanned probes with Information about us?
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 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…
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!
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.
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.
Cometary debris like meteor showers can also serve to bring
the micro-organisms to the upper parts of the atmosphere.
From these heights they will gradually descend. In steady
state their distribution with height can be determined.
Can we establish that such
a population exists?
ISRO-Cryosampler Experiment
TIFR-Balloon Facility used for flying a balloon
to a height of 41 km.
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.
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.
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.
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.
Serendipitous Discovery of Culture
Milton Wainwright from Sheffield obtained cultures from a
medium in the form of Potato Dextrose Agar (PDA).
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.
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 …