Humanity must rise above the Earth, to the top of the atmosphere and

beyond, for only then will we fully understand the world in which we live-

Socrates (500 B.C).

Introduction

Earth is a small component in the solar system which itself is a small spec in the Milky

Way galaxy. There are 100 billion galaxies in the universe. But Earth distinguishes itself by

being the only known abode of life in the known part of the universe.

Fig.-1: Our Solar System is a small part of the Milky Way galaxy (here in an edge-on view) and

situated in the spiral arm at two- third of the radial distance from the centre, closer to edge

Life on earth would appear to be a fortuitous coincidence of circumstances: right distance

from the Sun, allowing tolerable temperature yet adequate energy and sun light to run weather

cycle, and water in all the 3 forms. We know that water is a great solvent and hence facilitates

chemical reactions. The water cycle ensured washing down of the atmospheric carbon dioxide

sinking it as carbonate. Earth has rotational and revolution periods that seem to suit us, and

strong enough gravity to hold on to the atmosphere. Oxygen was essential for survival and it

facilitated formation of the ozone layer to filter out ultraviolet radiation. It also provided the air

blanket preventing loss of water by evaporation along with protection from asteroid- impacts.

Oceans provided a region safe from harmful radiations like ultraviolet and magnetic field of

Earth saved from energetic cosmic rays. Earth also has a range of elements essential for life, be

it carbon, nitrogen, hydrogen, oxygen, phosphorus or many others.

It will appear amusing but we survive because of Green House effect. But for the Green

House conditions (howsoever rued due to the much feared Global Warming at present), survival

on earth would have been impossible due to chill condition during the night time. It’s the

atmospheric blanket that makes Earth hospitable during the night time by trapping the escaping

heat. Change in climatic conditions is a serious concern at present. A small increase in

temperature makes headlines. El Nino and La Nina cause damage not only in the South

American continent but influence the weather in many other places. In the process of material

progress, we are deforesting and severely modifying the environment. The ice core records from

the polar area evidence the increase in carbon dioxide level by about 50% over a century, largely

due to industrial activities including fossil fuel burning.

All the anthropogenic influences on Earth are superposed on the astronomical and major

geological changes. All the astronomical and anthropogenic influences don't necessarily always

work oppositely or in the same direction hence may not always cancel. The anthropogenic

disturbances may be small compared to the natural factors but they influence us and are the only

one that we can control.

Earth: A Planetary Perspective

As UNESCO's 'Year of Planet Earth' in 2008 passes into 'Year of Astronomy' in 2009,

we ought to take a look at Earth from a planetary perspective too. Our knowledge about Earth

has been greatly enriched by what we learnt from planetary expeditions. View from a distance

provides a better perspective. With the enhancing knowledge- base for planets, we are beginning

to understand Earth better. This is because many geological processes are common on all planets.

As a result, the dividing line between the Earth and Planetary sciences is also gradually blurring.

The birth of Moon is an event related to Earth's early past when a Mars- sized body hit Earth.

When a sedimentary deposit is seen on Mars, such as in the Endurance Crater, one ought to

understand it by comparing with terrestrial sedimentary processes. Any landforms on a planet

are understood in terms of processes observed and explained by geologists on Earth be it sand

dunes on Mars, lava on Moon, or mountains like Olympus Mons and Gula Mons (volcano) on

Mars and Venus respectively.

Not many know that age of the earth was not determined in isolation from planetary

knowledge. The process is model based and complex. But in simple terms, the lead- lead age is

calculated on the basis of the change in the lead isotopic ratios as the rate of change is known.

But what was the initial ratio, that is ratio of lead isotopes, about 4.5 billion years ago when the

earth formed? The initial ratio was found from ratio measured in the mineral phase troilite (iron

sulphide) found in a meteorite Canyon Diablo which was nearly pure iron- nickel. The lead in

this phase troilite represented ancient lead which was free from any contamination. As troilite

contained no uranium or thorium, no lead was contributed from their radioactive decay. By

plotting lead 207/ lead 204 versus lead 206/ lead 204, Patterson had shown that the meteoritic

material and modern terrestrial sediments have followed the same pattern. The age of Earth has

been thus presumed to be he same as of meteorites and hence both had identical initial lead

isotopic ratios.

The Earth can't be studied insulated from our planetary knowledge. We have very

limited observation for interior of the earth and certain phases of earth's history remain dark.

When rocks brought back by Apollo-11 were dated, almost all samples turned out to be at least

3.8 billion year old. In contrast, on Earth, we don't see very old rocks, nor many craters as seen

on Moon and Mercury. The absence of early records on Earth can be attributed to its weathering

forces and heavy bombardment during its early phase. The study of craters on Moon and

mercury revealed that cratering was far more intense in the early stage of Solar System. Thus,

the earth and planetary studies have been complementary. Moon soil is a rich repository of solar

wind and solar flare gases which is not the case with Earth as it is protected by an atmospheric

shield. However, loss of early atmosphere of Earth is due to heavy irradiation by solar particles.

The climate in any part of the Earth is a strong function of the radiation reaching that

part. Climate can also vary if solar luminosity changes. It will also change with change in the

angle of Earth's rotation axis. In fact, Earth's axis changes its inclination between 21.5 and 24.5

degrees with a 41 thousand year cycle. Even the shape of Earth's orbit around the Sun is not

fixed. The eccentricity of the ellipse changes between 0.00843 and 0.0608 with a about one lac

year cycle. Not only this, there is a 21 thousand year cycle in the precession of the equinoxes

that is change in the direction of its axis. Such changes are not exclusive to Earth alone. Mars

has also undergone climate changes due to its axial tilt variation frequently.

The varying conditions on various planets can yield information about the various stages

of earth's evolution as well. On the other hand, processes which are well understood on earth can

help us in understanding the processes on other planets. When Europa, a satellite of Jupiter, was

found to have no craters, it immediately dawned that some kind of plate motion was at work that

flattened the earlier craters. It also indicated a fluid interior on which plates could slide as in the

case of Earth.

Thus, there are definite similarities but, even with the reasons being obscure but Earth

enjoys the unique distinction of being a living planet. Today it faces threats- some real and some

perceived. The bad part is that we can't always distinguish with confidence between the two.

Occasionally, the distinction or at least the remedial actions are governed by commercial

interests. The contradicting observations don't help in clearing the uncertainty, be it satellite

observations in favor of cooling along with recession of many glaciers indicating warming.

Some also choose to ignore the fact that some glaciers have registered a fall in rate of recession.

The present time on Earth is not an exceptional situation when temperature is high. It was lower

than this only once in the history of Earth. Sea level was always higher than at present except

once in the 4.5 billion year history of Earth! But we didn't exist at that time. That is the crux of

the matter. A high carbon dioxide conditions for millions of years during the Carbonaceous

period didn't kill a man (there was none), but a year of draught or floods or sudden change in

atmospheric composition now will kill many. What appears as a spike on the temperature versus

time graph, or may not even show on a large time scale, is enough to cause devastatation as it

may exceed human life time scales. So even a minor change in the present climatic conditions

raises alarm, and justifiably. Vanishing rails in some island or bleaching of corals at a remote

coast may not appear serious per se, but they are symptoms to merit serious attention. The

predicted two degree temperature rise over a century may not look menacing at first glance, but

the repercussions can be serious. In view of such constraints for origin and survival of life, life

couldn't have originated just anywhere. It requires favorable conditions. Emergence of life was a

highly improbable incidence, an incidence against serious odds but the chances are higher if the

conditions are favorable.

Possibility of Life on Other Solar System Bodies

While thinking in terms of life, one naturally wishes to look at the conditions on other

nearby places in the solar system. Sustenance of life demands certain basic requisites. Let's

have a look at our neighbors.

Table-1: Physical Characteristics of Earth and Neighbors

Name Approximate

Distance from

the Sun (AU)

Radius

(kms)

Mass

(In

Earth

Mass)

Mean

Density

(gms/ cc)

Remark

Mercury 0.39 2439 0.056 5.4

Dense, cratered

Venus 0.72 6050 0.81 5.25 Acidic gaseous

atmosphere,

silicate rocks

Earth 1 6378 1 5.5 Nitrogen-rich

atmosphere,

silicate rocks

Mars 1.52 3394 0.11 3.97

Tenuous CO2

atmosphere

Jupiter 5.2 71,880 318 1.33

97% H, He

Saturn 9.55 60,400 95 0.68

70% H, He

Uranus 19.2 23,540 15 1.6

Icy, rocky

Neptune 30 24,600 17 1.6

Icy, rocky

Moon 0.0026 1,738 0.012 3.3 Earth's only

satellite

1 AU is equal to Sun- Earth distance i.e. 14.96 crore kms

Mass of Earth is 6 x 1027

gms

--------------------------------------------------------------------------------------------------------------

Moon: Moon has been an object of curiosity for long. Partly because of its apparent size in the

night sky, its surface features and its brightness, more folklore and myths are associated with

Moon than any other celestial object. Even with the naked eye, one can see the dark Maria

(plural is Mare) and the light Highland area on Moon. Interestingly, we always see the same side

of Moon from Earth. The reason is that Moon keeps turning as it revolves around the Earth and

the two time- periods, of rotation and revolution, happen to match. The craters on Moon

distinguish it from Earth and other planets (except Mercury which also has a highly cratered

surface). The survival of craters speaks for its geological inactivity. But it did have volcanism

in the past as evidenced from dark Mare. The Mare represent the lava – filled craters. The 3476

km- sized dry body Moon is the nearest celestial body to Earth. The many excursions have been

negative as far as evidence of life is concerned.

Origin of Moon is related to an event is Earth's early history. A body, an asteroid the size

of Mars, hit Earth about 4.5 Billion years ago. It forced some crustal part of Earth to separate

away which later recondensed as Moon. The overall similarity in oxygen isotopic composition

between Earth and Moon, and the lighter density of Moon matching the Earth's crust support the

theory and rule out the capture and twin theories. Earth and Moon are also different in Earth

having a fluid mantle which keeps its plates in motion and possibly is responsible for its

magnetic field. Moon has no magnetic field though its remnant magnetic filed is revealed in

some minerals.

Fig.-2: Moon, Our Nearest Celestial Body

The serious study of Moon began with launching of Luna 2 by erstwhile USSR in 1959.

Man has left its footprint only on Moon among all the extra terrestrial bodies. Being the nearest

celestial object to us, it has invited more spaceships than any other body. India sent its own

Chandrayaan in 2008 which is still orbiting it. In general Moon has more rocks with old age

than Earth. Due to erosion, and other atmospheric and geological processes, Earth has lost most

of its old features. Moon, in contrast, has an atmosphere which is hardly 1 percent of the

terrestrial atmosphere, and has no water cycle or plate tectonics. However, atmosphere also

protects Earth from the impacting asteroids and other bodies which constantly impinge on Moon

surface churning the surface rocks to add to the surface rubble- the regolith. The Clementine and

Lunar prospector missions established that Moon may have water ice in deep craters especially

near the South pole where sun light doesn't reach. Lack of atmosphere also means no Green

House effect. The result is temperatures close to minus 50 degree Celsius in the night despite

very high temperature in the day time.

After exclusion of Pluto from the fraternity of planets, one is left with 7 planets and

Earth. In the order of increasing distance from the Sun they are: Mercury, Venus, Earth, Mars,

Jupiter, Saturn, Uranus and Neptune. There is also an asteroidal belt between the orbits of Mars

and Jupiter.

Fig.-3: Mercury with the characteristic cratered surface

Mercury: The pock- marked surface of Mercury tells about its difficult past. Slightly larger

than moon in size (4878 kms) and albedo, but denser than Moon, it has day- time temperature

about 450 degree C and night time of about –180 degree C. It completes one revolution in 88

days at about 50 kms per second, fastest among planets and takes 58.6 earth days for a rotation.

Fig.-3: Venus shrouded in mystery

Venus: The brightest object in the night sky after Moon and the star Sirius is Venus. At first

glance, if Earth had a twin, it would be Venus. It has a diameter of 12100 kms quite close to the

12756 kms of Earth and an average density of 5.25 gms /cc compared to 5.5 for Earth. One may

wonder, therefore, on lack of any evidence of life on it. But there are obvious reasons. About

10.8 crore kms from Sun and 4 crore kms from us, it’s wrapped in clouds of carbon dioxide,

acidic fumes, ammonia and like. The dense atmosphere leads to very high atmospheric pressure.

Being there is like being at a depth of almost a kilometer inside the ocean. A day on Venus is

longer than its year. That is saying that its rotation on its axis takes longer than a revolution

around the Sun. Earth takes about 24 hours for a rotation and 365 days for a revolution. In terms

of Earth- days, Venus has an year of only 225 Earth days but a day of 243 Earth- days. Not only

this, compared to Earth and most other planets, Venus rotates in the opposite direction. This

means Sun would appear to rise in the West and set in the east! Venus had micro plate-tectonics

in the past and volcanism too.

Closeness to Sun led to run-away Greenhouse effect on Venus. What this means is that

closeness to Sun caused more heating. This naturally led to more evaporation. Now, water

vapor being a Green House gas (capacity to absorb heat), it lead to further warming, again

leading to more evaporation. Today, the atmosphere is devoid of any moisture. The result of

these processes is a surface temperature of about 467 degree Celsius! This is higher than the

temperature at the surface of mercury which is much closer to the Sun. Obviously, we can't

imagine life at this temperature. The high surface temperature also implies no liquid water or ice,

a prime requirement for life as we now it and consequently, no rivers, lakes or oceans. There are

mountains on Venus, some caused by volcanic activity like Gula Mons. Its atmosphere has a

layer of carbon dioxide with sulfuric acid fumes overlying and clouds above them. It's these

clouds that cause very high refection of Sun light and causing the unusual brightness.

Mars: Mars has provided a good breeding ground for science fiction since long (remember 'The

War of the Worlds' by HG Wells?). The channels' presence on Mars as observed and reported by

Italian astronomer Giovanno Schiaparelli, fuelled hopes of there being living beings on Mars. It's

believed that he only meant 'canali' (channels) which was mistaken to be 'canals'.

Fig.- 4: 'The Hour glass' etched on Mars surface by a glacier

In fact, we understand the planetary processes also in terms of geological processes

known to us. The figure of hour glass, seen in the region called Promethei Terra at the eastern

rim of the Hellas Basin on Mars, was a mystery for 25 years till high resolution photographs

showed it to be a ‘Block’ glacier. From the nearby mountains, scree (ice and rocks) flowed into a

full impact crater about nine kilometers in size. Because of a slope, ice moved further to the

larger, 17-kilometer wide crater.

The 3 km- sized 'human head' on Mars photographed by Viking-1 in 1976 was another

intriguing feature. One had to wait for 25 years when photographs during a NASA mission in

2001 clearly showed that it was a common (mesa) structure on Mars. It was sheer lighting

conditions that gave it an appearance of head!

Fig.- 5: The 3 km- sized 'human head' seen

on Mars that remained a mystery for 25 years

For long, people had nurtured high expectation of seeing life on Mars. To their

disappointment, no living beings greeted the two rovers, Spirit and Opportunity, on Martian

surface in 2004. The earlier claim of bacteria-like features in an Allan Hill meteorite ALH

84001 recovered from Antarctica in 1984 were proved inconclusive and was dismissed more as

an artifact of processing. The presence of polycyclic aromatic hydrocarbon compounds was also

attributed to contamination. That closed the chapter for the time being.

There may or may not have been life on Mars but Mars was always not as hostile to life

as today. The climate on Mars has also been changing as also on Earth in response to the change

in inclination of its rotational axis. Compared to Earth, these changes have been more extreme

on Mars leading to frequent Ice Ages. There are sand- dune –like structures seen even today

indicative of winds in the past and now- dry channels of water flow in the past. Water in the past

is also evidenced in the layered sediment as seen in the Endurance crater by the rover

Opportunity. In addition, ice has been observed near the polar area.

While grey hematite found on Mars could also be formed without water, the presence of

mineral goethite is special as it can form only if there is water. Using Mossbauer spectrometer,

its presence was established in a rock called 'Clovis' in the 'Columbia Hills' of Mars. Goethite

contains water in the form of hydroxyl ion as a part of its structure. This means that climate

variations must have been much stronger. Mars differs from Earth in another respect. Martian

tectonics is different. It appears to be vertical. On Mars hot lava pushes upwards through the

crust to the surface. Mars Exploration Rover Spirit's Mössbauer spectrometer, showed the

presence of an iron-bearing mineral called goethite.

Any evidence even suggesting possibility of life anywhere other than Earth is meager.

Methane is generally associated with life- processes. Mars Express detected 10.5 PPB Methane

on Mars. But methane can only survive for a few hundred years on Mars. So the observed

methane was not ancient! But to use it as evidence of life, one has to establish that it was

biogenic. It may be volcanic, seeped from fissures, brought by comets etc. Benzene has been

detected in the protoplanetary nebula of CRL 618, a post red giant (a few benzene molecules/

cc). Three UV- resistant bacteria have been found in the outer space based on a balloon

experiment by Prof. JV Narlikar and colleagues. It is suggested that these could have come from

cometary tail or Martian meteorite. But none of these is yet an unequivocal proof for existence

of any extra- terrestrial life.

Jupiter: Jupiter, recognized by a huge Red Spot, is the biggest planet in the solar system. It is

97% hydrogen and helium. Almost 72 thousand kilometers in size, it generates more heat than it

receives from the Sun, a mystery not explained yet. Obviously the atmospheric pressure is

intolerable and is not conducive to life.

Saturn and its Satellite Titan: The next planet Saturn is spectacular on account of its many

rings. It's more like a compressed gas body dominated by hydrogen and helium. Its biggest

satellite Titan was an object of interest as in the year 2005 Cassini spacecraft dropped Huygen's

Probe in its atmosphere to record winds, rains (of methane), lightening and other phenomena.

But the hydrogen-, helium- rich atmosphere of Saturn has little hope to offer for life. Its cold

conditions are also discouraging.

Uranus and Neptune: The outer planets Uranus and Neptune also are too far away from the

Sun to have a reasonable temperature for life to sustain. Jupiter and Saturn are gaseous giants

while Uranus and Neptune are icy, rocky planets. Apart from its peculiarity of having its

rotation axis in the plane of revolution pointing to the Sun (making it roll), Uranus has energetic

winds (150 to about 550 kms per hour) in the mid latitudes. The planets is 83% hydrogen, 15%

helium, 2% methane with small amounts of acetylene and other hydrocarbons. Neptune is

slightly bigger than Uranus and has even faster winds (about 650 kms/ hour).

The description above fairly clearly rules out life on these planets at present. Geologically

the planets are nearly dead. This means no plate tectonics, no volcanism, and no mountain –

building. major changes occur because of impacts as evidenced in craters and communition of

surface material if no atmosphere. But it's not that life should only be expected on planets. The

problem of low temperature may be solvable by considering tidal heating such as by Jupiter on

Europa. The gravitational attraction may cause friction- generated heat in Europa. The microbes

may even derive energy from minerals. In our solar system itself, some satellites are bigger than

Mercury and may have geological activity. For instance Jovian satellite Europa has plate

tectonics. At 5150 kms, Titan, the biggest satellite of Saturn, is also interesting on account of a

rich cocktail of organic compounds in its atmosphere and frequent lightning. Titan is very cold

(- 180 degree C) and so can have methane in all the 3 states as it's close to the triple point of

methane.

The process for beginning of life on Earth is still unknown. In fact, no one knows

whether life originated on Earth at all or was tele- transported from planets of some other star

('Panspermia') as Svante Arrhenius proposed in the 19th century and Chandra Wickramsinghe

agrees. Seeds of life could have also arrived hidden inside some cometary material, or could

have reached Earth enclosed in some carbonaceous meteorites which includes elementary carbon

and also water (indicating low temperature history) indicating it to be possible for living material

to reach intact. Material also reaches Earth from Moon, asteroids and even Mars.

Fig.- 6: Some of the satellite may have active volcanism such as shown by

Jupiter's satellite Io. The ejecta may be rich is organic and other material conducive to life.

Stanley Miller and Nobel Laureate Harold Urey showed at Chicago in 1952 that amino acid

(building blocks of proteins) could be formed by the inorganic process of electric discharge in a

flask filled with gases like methane, ammonia, hydrogen and water vapors. The subsequent story

of building of life- forms. however, still remains unknown.

Signals from Living Civilizations

Appearance of life on Earth may be a very low- probability- event but it happened,

nevertheless. But is it there anywhere else? There is an unusual collaboration already in

progress by name SETI, short form of Search for Extraterrestrial Intelligence. It's a project

supported more by the private societies like Planetary Society than any government. The aim is

to donate computer time to process the radio signals received from space to identify if any of

them is from an intelligent civilization. There is no success so far but people haven't lost hope.

But are there intelligent civilizations elsewhere? No one can say for sure. But if it's there, and it

can communicate with us, it has to be advanced in civilization. Consequently, their way of

communication also has to be intelligent. For instance, some argued that they should be able to

communicate with precise frequency. The signal should be strong enough to be discerned above

the background. The signals need not be as language which may not be known to them. It may

be pictures or numerical expressions conveyed through electromagnetic signals as binary codes,

rhythmic patterns or any such form which conveys intelligence.

In 1960, an astronomer Frank Drake proposed estimating the probability of detecting

intelligent life in some other place. He believed that the following formula represents it pretty

well:

The number detectable of civilizations in the universe N= R * f p n e f l f i f c L

Here

N = The number of civilizations in The Milky Way Galaxy whose radio emissions are detectable.

R* = The rate of formation of stars suitable for the development of intelligent life.

f p = The fraction of those stars with planetary systems.

ne = The number of planets, per solar system, with an environment suitable for life.

fl = The fraction of suitable planets on which life actually appears.

f i = The fraction of life bearing planets on which intelligent life emerges.

f c = The fraction of civilizations that develop a technology that releases detectable signs of their

existence into space.

L = The length of time such civilizations release detectable signals into space.

The number this will yield will be small. But low probability only tells that over a very

long time, favorable event happens too few times. It doesn't predict as to when that will happen.

So people are optimistic that some day, we shall hear the good news.

Is Our Tunnel- Vision the Culprit?

If people were to define life, no single definition would emerge. It can't be defined in

terms of chemical or physical formulae. Life forms are known to have been made up of cells,

built and operated by proteins which are in turn built from 20 amino acids. Miller has shown

that amino acids can be produced by inorganic processes. Defining life is not easy. One may

assign different behavioral characteristics to life like metabolism, variation and heredity. As has

been argued by people, if we say that consumption of energy for sustenance characterizes life,

even fire does that. If we say that it should react and take decision; that is done by the rovers,

Spirit and Opportunity, on Mars. Even reproduction can not be an essential characteristic as

mules don't reproduce.

The force of life is unmatched. It can thrive in the harshest conditions. Life has been

seen in weird forms inside the oceans. It has been seen to survive the harshest conditions such as

near geothermal vents where water is boiling. Bacteria have been seen at half a kilometer depth,

in the permafrost, in Canadian high Arctic where salty springs were present. If evaporation leads

to salty water somewhere, salt- loving bacteria develop such as in the Mono lake in California.

The biggest handicap may be our pre- conceived notions about forms of life. We tend to search

for life in some familiar forms. But life- forms need not be similar everywhere. Had we not

seen the bacteria under the microscope, we couldn't have imagined life could be like that. Even

vegetation is not to be expected in green everywhere.

Werner Von Braun said, 'It would be height of presumption to think that we are the only

living things in that enormous immensity'. We have to ask ourselves if our tunnel- vision is

preventing us from finding new forms of life. Physical theories disallow velocities higher than

light for real masses. So, at the same time, given the huge dimensions in the universe, how can

one expect any other intelligence to reach us in a life time? It would take one lac year for some

one at a speed of light to even cross our Milky Way galaxy. The nearest stars, other than Sun,

like Proxima Centauri are about 4 light years away. But that doesn't mean that the search

should stop. It's a win- win situation: if we find life elsewhere, it's mission successful. If not, we

establish our uniqueness. So the search must continue: Charaiveti, chareiveti.

Conclusions

Life is a rarity in the universe we know, and hence precious. Human activities and

natural phenomena are threatening Earth today. Indeed, there are people who sincerely believe

that Earth will take care of itself. Earth does have large latitude for adjustment but not infinite.

Natural factors may be difficult to offset with our present capabilities but the minimum we can

do is not disturb the precarious balance of nature. This is the only abode we have. How we

treat Earth will decide the course of our future and Earth- scientists in collaboration with other

experts have an important role to play in this mission.

Acknowledgement: I am thankful to The Society of Earth Scientists for inviting me to deliver

this lecture in its meeting and to Director, BSIP for permission. I express my deep sense of

gratitude to NASA whose photographs have been used in this article.

Suggested Readings:

1. Hays JD, Imbrie John, Shackleton (1976). Variation in the Earth's Orbit: Pacemakers of

the Ice Ages. Science 194, 4270. P. 1121- 1131.

2. Taylor SR (1982). Planetry Science: A Lunar Perspective. Lunar and Planetary Institute,

Houston. PP 481.

3. Francis Peter W (1992). Exploration of the Solar System. In Understanding the Earth.

Eds.: Brown GC, Hawkesworth CJ and Wilson RCL. Cambridge University Press, UK, p.

3- 24.

4. www.nasa.gov.home

5. McKay DS et al. (1996). Search for Past Life on Mars: Possible Relic Biogenic Activity

in Martian Meteorite ALH 84001. Science 273, 924- 930.

6. McCoy Timothy J (1997). A Lively Debate. Nature 386, P. 557- 558.

7. Rees Martin (2003). Is There Life Beyond Earth? New Scientist (12 July), p.24- 27.

About the Author

Dr. Chandra Mohan Nautiyal is Scientist-in- Charge of the Radiocarbon

laboratory at Birbal Sahni Instt. of Palaeobotany, Lucknow (UP) and involved in

Palaeoclimatic research. He is also an active science communicator. During his

doctoral and post-doctoral research at Physical Research Lab., Ahmedabad, he

carried out isotopic studies on meteorites and the lunar material from Apollo and

Luna missions. Apart from over 60 research contributions, Dr. Nautiyal has about

3 dozen popular articles in magazines, newspapers etc. and delivered about 250

popular science lectures. He has been involved in over 100 science programmes

on radio and TV. He is a recipient of INSA medal for Young Scientists, travel

award from Meteoritical Society-USA and first prize from Indian Mass

spectrometry Society in addition to Vigyan Vachaspati from Vigyan Parishad,

Prayag. He has visited/ lectured/ presented papers at a number of institutions in

France, USA, Germany, Switzerland and South Africa.