2. Life is everywhere, but it is not having any proper one-sentence definition. Actually
life is a characteristic feature of an individual. We can say that it is the existence of an
individual human being or animal. Some of the properties of life are given below:
•Order Living organisms partition resources and nutrients within their systems. This is
an energy-requiring process which must be maintained for life to continue.
•Reproduction Organisms reproduce their own kind. Life only comes from life.
•Growth and Development Heritable characters direct the pattern of growth and
development, producing an organism that is characteristic of its species.
•Energy Utilization Organisms take in energy and transform it to do work. Almost all of
life's functions require energy.
•Homeostasis Regulatory mechanisms maintain an organism's internal environment within
tolerable limits, even though the external environment may fluctuate. This process is
known as homeostasis.
•Evolutionary Adaptation Live evolves as a result of the interaction between organisms
and their environment. As the environment is rarely stable, life must adapt to survive
in these new living conditions.
3. Naturalistic theories concerning life’s origin began to take shape in 1953. Watson and
Crick unravelled the structure of DNA, and Stanley Miller performed an experiment
showing that amino acids can be produced in a spark chamber.
The early pioneers in this field realized that a complete living organism, could not
spontaneously appear in a spark chamber or in any other environment governed by
purely naturalistic laws.
The pioneers needed the first form of life to be simpler than anything that is present
on earth today.
It is generally agreed that all life today evolved by common descent from a single
primitive life form. We do not know how this early form came about, but scientists
think it was a natural process which took place perhaps 3,900 million years ago.
This is in accord with a philosophy called naturalism: only natural causes are
admitted.
We do not know whether metabolism or genetics comes earlier. The
main hypothesis which supports genetics first is RNA world hypothesis, and the one
which supports metabolism first is Protein world hypothesis.
4. • 19th Century Ideas
– life created supernaturally
• cannot be proven scientifically
– continually being formed by spontaneous generation of nonliving
matter
• untenable by numerous experiments
• 20th Century
– life generated spontaneously and evolved through different steps.
6. THEORIES GIVEN BY
SCIENTISTS TO EXPLAIN
CHEMICAL EVOLUTION OF
LIFE ON EARTH
PANSPERMIA
Perhaps life did not begin on Earth at all, but was brought
here from elsewhere in space, a notion known
as panspermia. For instance, rocks regularly get blasted off
Mars by cosmic impacts, and a number of Martian
meteorites have been found on Earth that some researchers
have controversially suggested brought microbes over here,
potentially making us all Martians originally. Other scientists
have even suggested that life might have hitchhiked on
comets from other star systems. However, even if this
concept were true, the question of how life began on Earth
would then only change to how life began elsewhere in
space.
7. Simple Beginnings
Instead of developing from complex molecules such as
RNA, life might have begun with smaller molecules
interacting with each other in cycles of reactions.
These might have been contained in simple capsules
akin to cell membranes, and over time more complex
molecules that performed these reactions better than
the smaller ones could have evolved, scenarios dubbed
"metabolism-first" models, as opposed to the "gene-
first" model of the "RNA world" hypothesis.
RNA World
DNA needs proteins in order to form, and proteins
require DNA to form, so how could these have formed
without each other? The answer may be RNA, which
can store information like DNA, serve as an enzyme
like proteins, and help create both DNA and proteins.
Later DNA and proteins succeeded this "RNA world,"
because they are more efficient. RNA still exists and
performs several functions in organisms, including
acting as an on-off switch for some genes. The
question still remains how RNA got here in the first
place.
8. Chilly Start
Ice might have covered the oceans 3 billion years
ago, as the sun was about a third less luminous
than it is now. This layer of ice, possibly hundreds
of feet thick, might have protected fragile organic
compounds in the water below from ultraviolet
light and destruction from cosmic impacts. The
cold might have also helped these molecules to
survive longer, allowing key reactions to happen.
Deep-Sea Vents
The deep-sea vent theory suggests that life may
have begun at submarine hydrothermal vents,
spewing key hydrogen-rich molecules. Their rocky
nooks could then have concentrated these
molecules together and provided mineral catalysts
for critical reactions. Even now, these vents, rich in
chemical and thermal energy, sustain vibrant
ecosystems.
9. Community Clay
The first molecules of life might have met on clay, according to an
idea elaborated by organic chemist Alexander Graham Cairns-Smith
at the University of Glasgow in Scotland. These surfaces might not
only have concentrated these organic compounds together, but also
helped organize them into patterns much like our genes do now.
The main role of DNA is to store information on how other molecules
should be arranged. Genetic sequences in DNA are essentially
instructions on how amino acids should be arranged in proteins.
Cairns-Smith suggests that mineral crystals in clay could have
arranged organic molecules into organized patterns. After a while,
organic molecules took over this job and organized themselves.
Electric Spark
Electric sparks can generate amino acids and sugars from an
atmosphere loaded with water, methane, ammonia and hydrogen,
as was shown in the famous Miller-Urey experiment reported in
1953, suggesting that lightning might have helped create the key
building blocks of life on Earth in its early days. Although research
since then has revealed the early atmosphere of Earth was actually
hydrogen-poor, scientists have suggested that volcanic clouds in the
early atmosphere might have held methane, ammonia and
hydrogen and been filled with lightning as well.
10. The Milky Way is the galaxy that contains
our Solar System. Its name "milky" is derived from
its appearance as a dim glowing band arching across
the night sky in which the naked eye cannot
distinguish individual stars.
The term "Milky Way" is a translation of the
Classical Latin via lactea, from the Greek γαλαξίας
κύκλος (pr. galaxías kýklos, "milky circle"). From the
Earth, the Milky Way appears like a band because its
disk-shaped structure is viewed from within the
Galaxy.
Galileo Galilei first resolved the band of light into
individual stars with his telescope in 1610. In the
past, astronomers thought that all of the stars in
the universe were contained inside of the Milky Way.
Following the 1920 Great Debate between the
astronomers Harlow Shapley and Heber Curtis,
observations by Edwin Hubble definitively showed
that the Milky Way is just one of many galaxies.
THE MILKY WAY
11. S.NO. PLANET’S /
SATELLITE NAME
ELEMENTS FOUND ON THE PLANET
1. MOON calcium (Ca), Aluminium (Al),Titanium (Ti),
Silicon (Si),Oxygen (O)
2. MERCURY 70% metallic and 30% silicate material
3. VENUS hydrogen chloride (Hcl), hydrogen fluoride (HF),
carbon monoxide, water vapour, molecular oxygen,
sulphuric acid (H2SO4), hydrogen sulphide (H2S).
4. EARTH Iron, Oxygen, Silicon, Magnesium, Sulphur, Nickel,
Calcium, Aluminium
5. MARS Silicon, Oxygen, Metals, Iron, Nickel, Magnesium,
Aluminum, Calcium, and Potassium
6. JUPITER Hydrogen, Helium, Methane, Water vapour, Ammonia,
Silicon, Carbon, Ethane, Hydrogen
sulphide, Neon, Oxygen, Phosphine, and Sulphur
7. SATURN Molecular hydrogen, Helium,
Ammonia, Acetylene, Ethane, Propane, Phosphine and Me
thane
8. URANUS Helium, Methane (CH4),
Ethane (C2H6), Acetylene (C2H2),Methyl
acetylene (CH3C2H), and Diacetylene (C2HC2H).
Water vapour, Carbon monoxide and Carbon dioxide
9. NEPTUNE Hydrogen, Helium, Methane
12. The Moon is the
only natural satellite of
the Earth and the fifth
largest moon in the Solar
System.
It is the largest natural
satellite of a planet in the
Solar System relative to
the size of its primary,
having 27% the diameter
and 60% the density of
Earth, resulting
in 1⁄81 its mass.
Among satellites with
known densities, the Moon
is the second densest,
after Io, a satellite of
Jupiter.
MOON
13. Mercury is the smallest and closest to the Sun of the
eight planets in the Solar System, with an orbital period of
about 88 Earth days.
Mercury is one of four terrestrial planets in the Solar
System, and is a rocky body like the Earth. It is the
smallest planet in the Solar System, with
an equatorial radius of 2,439.7 km.
Mercury is even smaller—albeit more massive—than
the largest natural satellites in the Solar
System, Ganymede and Titan.
Mercury's density is the second highest in the Solar
System at 5.427 g/cm3, only slightly less than Earth's
density of 5.515 g/cm3.
Mercury's density can be used to infer details of its inner
structure. Although Earth's high density results appreciably
from gravitational compression, particularly at the core,
Mercury is much smaller and its inner regions are not as
compressed. Therefore, for it to have such a high density,
its core must be large and rich in iron.
MERCURY
14. Venus is the second planet from the Sun,
orbiting it every 224.7 Earth days.
The planet is named after the Roman goddess of
love and beauty. After the Moon, it is the
brightest natural object in the night sky, reaching
an apparent magnitude of −4.6, bright enough to
cast shadows.
The atmosphere contains a range of interesting
compounds in small quantities, including some based
on hydrogen, such as hydrogen chloride (Hcl)
and hydrogen fluoride (HF).
Hydrogen is in relatively short supply in the
Venusian atmosphere.
A large amount of the planet's hydrogen is
theorised to have been lost to space, with the
remainder being mostly bound up in sulphuric
acid (H2SO4) and hydrogen sulphide (H2S).
VENUS
15. Earth is the third planet from the Sun, and
the densest and fifth-largest of the eight planets in
the Solar System. It is also the largest of the Solar
System's four terrestrial planets. It is sometimes
referred to as the world or the Blue Planet.
Earth formed approximately 4.54 billion years ago,
and life appeared on its surface within its first billion
years.
The mass of the Earth is
approximately 5.98×1024 kg.
The geochemist F. W. Clarke calculated that a little
more than 47% of the Earth's crust consists of
oxygen.
Earth's biosphere then significantly altered the
atmospheric and other basic physical conditions, which
enabled the proliferation of organisms as well as the
formation of the ozone layer, which together
with Earth's magnetic field blocked harmful solar
radiation, and permitted formerly ocean-confined life
to move safely to land.
EARTH
16. Mars is the fourth planet from the Sun and the second smallest planet in the Solar
System. Named after the Roman god of war, it is often described as the "Red Planet"
because the iron oxide prevalent on its surface gives it a reddish appearance.
Mars is a terrestrial planet, which means that its bulk composition, like Earth's,
consists of silicates (minerals containing silicon and oxygen), metals, and other elements
that typically make up rock. The planet's distinctive red colour is due to
the oxidation of iron on its surface.
MARS
17. Methane on Mars - "potential sources
and sinks" (November 2, 2012).
The elemental composition of Mars is
different from Earth′s in several
significant ways.
1. First, Martian meteorite analysis
suggests that the planet's mantle is
about twice as rich in iron as the
Earth's mantle.
2. Second, its core is more rich in
sulphur.
3. Third, the Martian mantle is richer
in potassium and phosphorus than
Earth's, and
4. Fourth, the Martian crust contains
a higher percentage
of volatile elements such as sulphur
and chlorine than the Earth's crust
does. Many of these conclusions are
supported by in situ analyses of
rocks and soils on the Martian
surface.
18. Jupiter is the fifth planet from the Sun and
the largest planet in the Solar System.
It is a gas giant with mass one-thousandth of
that of the Sun but is two and a half times
the mass of all the other planets in the Solar
System combined.
Jupiter is classified as a gas giant along
with Saturn, Uranus and Neptune. Together,
these four planets are sometimes referred to as
the Jovian or outer planets.
Through infrared and ultraviolet measurements,
trace amounts of benzene and
other hydrocarbons have also been found.
Neon in the upper atmosphere only consists
of 20 parts per million by mass, which is about
a tenth as abundant as in the Sun.
JUPITER
19. Saturn is the sixth planet from the Sun and the
second largest planet in the Solar System, after Jupiter.
Named after the Roman god of agriculture, Saturn,
its astronomical symbol (♄) represents the god's sickle.
Saturn is a gas giant with an average radius about nine
times that of Earth.
The total mass of these heavier elements is estimated
to be 19–31 times the mass of the Earth, with a
significant fraction located in Saturn's core region.
The upper clouds are composed of ammonia crystals,
while the lower level clouds appear to consist of
either ammonium hydrosulfide(NH4SH) or water.
Ultraviolet radiation from the Sun causes methane
photolysis in the upper atmosphere, leading to a series of
hydrocarbon chemical reactions with the resulting products
being carried downward by eddies and diffusion. This
photochemical cycle is modulated by Saturn's annual
seasonal cycle.
SATURN
20. Titan (or Saturn VI) is the largest moon of Saturn.
It is the only natural satellite known to have a
dense atmosphere, and the only object other
than Earth for which clear evidence of stable bodies
of surface liquid has been found.
Titan is the sixth ellipsoidal moon from Saturn.
Frequently described as a planet-like moon, Titan
has a diameter roughly 50% larger than
the Moon and is 80% more massive.
Titan is the second-largest moon in the Solar
System, after Jupiter's moon Ganymede, and is
larger by volume than the smallest planet, Mercury,
although only about 41% as massive.
Titan was the first known moon of Saturn,
discovered in 1655 by the Dutch
astronomer Christiaan Huygens, and was the fifth
moon (not including the Moon) to be discovered. It
is primarily composed of water ice and rocky
material.
TITAN (moon of Saturn)
21. Uranus is the seventh planet from the Sun. It has the
third-largest planetary radius and fourth-largest planetary
mass in the Solar System.
Methane possesses prominent absorption bands in
the visible and near-infrared (IR) making
Uranus aquamarine or cyan in colour.
Along with methane, trace amounts of
various hydrocarbons are found in the stratosphere of
Uranus, which are thought to be produced from methane
by photolysis induced by the solar ultraviolet (UV)
radiation.
They include ethane (C2H6), acetylene (C2H2),methyl
acetylene (CH3C2H), and Diacetylene (C2HC2H).
Spectroscopy has also uncovered traces of water
vapour, carbon monoxide and carbon dioxide in the upper
atmosphere, which can only originate from an external
source such as in falling dust and comets.
URANUS
22. Neptune is the eighth and farthest planet from
the Sun in the Solar System. It is the fourth-
largest planet by diameter and the third-largest by
mass.
Neptune is 17 times the mass of Earth and is
slightly more massive than its near-twin Uranus,
which is 15 times the mass of Earth but not as
dense.
Named for the Roman god of the sea,
its astronomical symbol is ♆, a stylised version of
the god Neptune's trident.
Prominent absorption bands of methane occur at
wavelengths above 600 nm, in the red and infrared
portion of the spectrum.
As with Uranus, this absorption of red light by
the atmospheric methane is part of what gives
Neptune its blue hue, although Neptune's vivid azure
differs from Uranus's milder cyan.
NEPTUNE
23. Human spaceflight
NASA has successfully launched over 100 manned flights. Two have ended in failure,
causing the death of the crew, such as, STS-51-L (the Challenger disaster) in 1986,
and STS-107 (the Columbia disaster) in 2003. (Apollo 1 in 1967 lost three crew
members but never launched)
Future missions
Strofio is a unique mass spectrometer that is part of the SERENA instrument
package that will fly on board the European Space Agency’s BepiColombo /Mercury
Planet Orbital spacecraft. Strofio will study the atoms and molecules that compose
Mercury's atmosphere to reveal the composition of the planet's surface. Stefano Livi of
Southwest Research Institute is the Principal Investigator.
Lander Radio-Science on ExoMars, or LaRa, will use NASA's Deep Space Network of
radio telescopes to track part of ESA's ExoMars mission. Scheduled to launch in 2016,
the mission consists of a fixed lander and a rover that will roam Mars collecting soil
samples for detailed analysis. William Folkner of NASA's Jet Propulsion Laboratory is
the Principal Investigator.
Titan Mare Explorer (TiME) would have provided the first direct exploration of an
ocean environment beyond Earth by landing in, and floating on, a large methane-ethane
sea on Saturn's moon Titan.
Comet Hopper (CHopper) would have studied cometary evolution by landing on a
comet multiple times and observing its changes as it interacts with the Sun.
24. For the past four decades, ISRO has launched 70 satellites for various scientific and
technological applications like mobile communications, Direct-to-Home services,
meteorological observations, telemedicine, tele-education, disaster warning, radio
networking, search and rescue operations, remote sensing and scientific studies of the
space.
ISRO has established two major space systems, the Indian National Satellite System
(INSAT) series for communication, television broadcasting and meteorological services
which is Geo-Stationary Satellites, and Indian Remote Sensing Satellites (IRS) system
for resources monitoring and management which is Earth Observation Satellites .
Recently India has launched a spacecraft to carry out observation of physical features of
mars and carry out limited study of Martian atmosphere .
Launch Date - Nov 05, 2013
Launch Site - SDSC SHAR Centre, Sriharikota, India
Launch Vehicle - PSLV - C25
Indian Space Research Organization
25. S.no PLANET/
SATELLITE
NAME OF
SPACECRAFT
DEVELOPED
/MANUFAC-
TURED BY
LAUNCHING
DATE
LANDING
DATE
NOTES
1. MOON Luna 2 Soviet Union September
13,
1959
July 20,
1969
Journey
time of
around 36
hours.
2. MERCURY -------- ---- ---- ----
3. VENUS Venera 7
(Venera being the
Russian name for
Venus)
Soviet Union August 17,
1970
December
15, 1970
(Survived
only for 23
minutes)
4. MARS Mariner 4 Jet
Propulsion
Laboratory
28
November
1964
21
December
1967
Success
(21
images
returned)
5. JUPITER Pioneer 10 NASA Ames
Research
Centre
March 3,
1972
December
2, 1972
(closest
approach)
Photography of
Jupiter began
November 6,
1973, at a range
of 25,000,000
km, and a total of
about 500
images were
transmitted
26. S.no PLANET/
SATELLITE
NAME OF
SPACECRAFT
DEVELOPED
/MANUFAC-
TURED BY
LAUNCHING
DATE
LANDING
DATE
NOTES
6. SATURN Voyager 2 European
Space
Agency (ESA)
December
25, 2004
January 14,
2005
(Landed on
Saturn's
moon Titan)
This was
the first
Landing
ever
accomplis
hed in
the outer
Solar
System.
7. URANUS Voyager 2 NASA August 20,
1977
January 24,
1986
(Closest
approach)
Voyager 2
Discovere
d 10
previously
unknown
moons
8. NEPTUNE Voyager 2 NASA August 20,
1977
August 25,
1989
(Closest
approach)
Voyager 2
discovere
d six
moons
orbiting
27. KEPLER
(SPACECRAFT)
Kepler is a space observatory launched by NASA to discover Earth-like
planets orbiting other stars. The spacecraft, named after the Renaissance
astronomer Johannes Kepler, was launched on March 7, 2009.
In April 2012, an independent panel of senior NASA scientists recommended
that the Kepler mission be continued through 2016.
According to the senior review, Kepler observations needed to continue until
at least 2015 to achieve all the stated scientific goals.
On 14 November 2012, NASA announced the completion of Kepler's primary
mission, and the beginning of its extended mission, which may last as long as
four years.
NASA's Kepler space telescope has discovered three exo planets that may be
capable of supporting life, and one of them is perhaps the most Earth-like alien
world spotted to date.
28.
29. That most intriguing one is called Kepler-62f, a rocky world just 1.4 times
bigger than Earth that circles a star smaller and dimmer than the sun.
Kepler-62f's newfound neighbour, Kepler-62e, is just 1.6 times larger than
Earth, making the pair among the smallest exoplanets yet found in their
star's habitable zone — the just-right range of distances where liquid water
can exist on a world's surface.
Kepler-62e and f, which are part of a newly discovered five-planet system,
"look very good as possibilities for looking for life," said Kepler science principal
investigator Bill Borucki, of NASA's Ames Research Centre in Moffett Field,
Calif.
The third potentially habitable planet, called Kepler-69c, is 1.7 times
bigger than Earth and orbits a star similar to our own. It's the smallest
world ever found in the habitable zone of a sun like star, researchers said,
and represents a big step toward discovering the first-ever "alien Earth”.
Researchers announced these newfound planets — all three of which are
"super-Earths," or worlds slightly larger than our own.
The three potentially habitable worlds are part of a larger haul. All told, the
scientists rolled out seven new exoplanets today — five in the Kepler-62
system and two in Kepler-69.
