Transcript No Slide Title
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 * f
s
* f
p
* n
e
* f
l
* f
i
* f
c
* L
Drake's equation:
N= R*f
s
*f
p
*n
e
*f
l
*f
i
*f
c
*L
R
= Average rate of star formation (stars/year)
Drake's equation:
N= R*f
s
*f
p
*n
e
*f
l
*f
i
*f
c
*L
f s R
= Average rate of star formation (stars/year) = Fraction of stars that are ‘good’
suns
Drake's equation:
N= R*f
s
*f
p
*n
e
*f
l
*f
i
*f
c
*L
f s R
= Average rate of star formation (stars/year) = Fraction of stars that are ‘good’
suns
f p
= Fraction of good stars with planetary systems
Drake's equation:
N= R*f
s
*f
p
*n
e
*f
l
*f
i
*f
c
*L
f s R
= Average rate of star formation (stars/year) = Fraction of stars that are ‘good’
suns
f p
n e = Fraction of good stars with planetary systems = Number planets per stars within ecoshell
Drake's equation:
N= R*f
s
*f
p
*n
e
*f
l
*f
i
*f
c
*L
f s R
= Average rate of star formation (stars/year) = Fraction of stars that are ‘good’
suns
f p
n e = Fraction of good stars with planetary systems = Number planets per stars within ecoshell
f l
= Fraction of n e on which life develop
Drake's equation:
N= R*f
s
*f
p
*n
e
*f
l
*f
i
*f
c
*L
f s R
= Average rate of star formation (stars/year) = Fraction of stars that are ‘good’
suns
f p
n e = Fraction of good stars with planetary systems = Number planets per stars within ecoshell
f l f i
= Fraction of n e on which life develop = Fraction of living species that develop intelligence
Drake's equation:
N= R*f
s
*f
p
*n
e
*f
l
*f
i
*f
c
*L
f s R
= Average rate of star formation (stars/year) = Fraction of stars that are ‘good’
suns
f p
n e = Fraction of good stars with planetary systems = Number planets per stars within ecoshell
f l
= Fraction of n e on which life develop
f i f e
= Fraction of living species that develop intelligence = Fraction of intelligent species reaching an electromagnetic communicative phase
Drake's equation:
N= R*f
s
*f
p
*n
e
*f
l
*f
i
*f
c
*L
f s R
= Average rate of star formation (stars/year) = Fraction of stars that are ‘good’
suns
f p
n e = Fraction of good stars with planetary systems = Number planets per stars within ecoshell
f l
= Fraction of n e on which life develop
f i f e
= Fraction of living species that develop intelligence = 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 …