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Big bang
Nuclear fusion in stars
Evidence for life
Supernova nucleosynthesis
Exotrasolar planets
Planetary formation
Current Solar System
Finding the Evidence for life
in the Solar System
Are We Alone in the Universe?
• Is the Earth isolated from the other system?
• Is human being unique in the vast universe?
• Is the birth of the life on the Earth miracle?
Are there Exoplanets in the universe?
Are there Earth-like planets in the universe?
?
Is there intelligent extraterrestrial life (E.T.)?
Is there extraterrestrial life?
?
Extreme Life on Earth
• In addition to the more familiar life, life on Earth is often found in
surprising and extreme environments.
• Dark Life
Bacteria that thrive beneath the Earth or deep inside polar ice
• Hot Life
Microbes surviving in boiling water in geyser pools (e.g., Grand
Prismatic Spring in Yellowstone National Park)
Deep ocean life near very hot thermal vents
• In other words, life can be pretty tough, so it might thrive in a
broad range of conditions.
Life Elsewhere in the Solar System?
Could life exist in our Solar System? So far we haven't found it.
• Mars
Evidence it had liquid water and maybe a heavier atmosphere in the distant past.
Life might have briefly arisen there, and might survive underground
• Europa
A model is that it has a liquid ocean under its ice that is warmed by tides
The outer shell of ice protects it from UV radiation and cold
• Enceladus (Icy Moon of Saturn)
Warm water geysers seen by the Cassini spacecraft, suggest reservoirs of warm
liquid water below the ice (heated by tides), as well as signs of organics. Like
Europa, shielded by the outer ice layer.
• Titan
Titan has a thick methane atmosphere, and liquid methane chemistry. Maybe
too cold for water-based life, but methane-based life???
Enceladus
Habitable Zone
• What would happen if we moved the Earth closer to the Sun?
– Temperature would increase due to the greater solar heating.
– At a distance of 0.84-0.95 AU, extra solar heating is enough to trigger a
Runaway Greenhouse Effect.
– Earth would become like Venus today.
• What would happen if we moved the Earth away from the Sun?
– Temperature would decrease because of the reduced solar heating.
– At a distance of 1.4-1.5 AU, water would begin to freeze out (depends
somewhat on how well the greenhouse effect can keep the Earth warm).
– Get a frozen "Snowball Earth".
• The Habitable Zone is a region where water can be liquid at
normal atmospheric pressure.
– The inner boundary : runaway greenhouse effect
– The outer boundary : CO2 condensation (at 1atm 195 K)
Surface temperature
Surface pressure
Atmosphere
735K
9.3 MPa
CO2 96.5%
N2 3.5%
SO2 0.015%
180-330K (average 287K)
100 kPa
N2
78%
O2
21%
H2O
about 1%
180-270 K
0.4-0.9 kPa
CO2
95.3%
N2
2.7 %
Alignment of iron filings sprinkled on paper placed above a bar magnet
Planet's size
• What happens if the size of Earth becomes larger or smaller?
• Make the Earth too small
– Too small to retain a warm atmosphere
– Interior would cool rapidly, and it would lose its magnetic field, making
the atmosphere vulnerable to loss to the solar wind.
• An example of a "too small" planet is Mars (0.1 Earth mass).
Mars is almost within the Sun's habitable zone, but it is too
small, and is a frozen desert world with a very thin atmosphere,
solidified interior, and virtually no magnetic field.
magnetosphere
Mars surface
The solar wind is a stream of charged particles ejected from the upper atmosphere of the
Sun. It mostly consists of electrons and protons.
At speed of ~400 km/s, a few particles per cm3
• Make the Earth too big
– It can now retain H and He in its atmosphere, and so can build a very
heavy atmosphere.
– Leads to an atmosphere that is too hot and too high pressure for liquid
water.
– Abundant Hydrogen shifts the basic chemistry from oxidizing
chemistry to reducing chemistry (reduction rather than oxidation)
• This implies that there is also a mass limit within which a
planet in the Habitable Zone is hospitable to life. A rough
estimate is within the range of 0.2-10 Earth Masses.
• To be hospitable to life, a planet cannot be too hot or too cold,
or too big or too small.
People said basic requirements/conditions for life are:
Source of Energy
Favorable Environments (especially low UV)
Complex Chemistry (liquid water and carbon)
Criteria for Habitable Planets
Distance from its parent star (Habitable Zone)
Size of the Planet
NASA's Kepler Mission Confirms Its First Planet
in Habitable Zone of Sun-like Star
2.4 times the radius of Earth
NASA press release on Dec 05, 2011
Basic Requirements for Life
Energy
Warmth to allow liquid water to exist
The energy is essential for fuel chemical reactions
(metabolism, 신진대사)
Protection from harmful UV radiation
UV light can damage or break complex molecules
Protection is afforded by the O3 layer, underwater, or
underground
Complex Chemistry
Elements heavier than Hydrogen & Helium
Carbon as building blocks for complex organic molecules
consider the extraterrestrial organics and water
Runaway Greenhouse Effect
• A process in which a positive feedback between surface
temperature and atmospheric opacity increases the strength of
the greenhouse effect on a planet until its oceans boil away.
• believed to have happened in the early history of Venus
Taxonomic Types of Asteroid

Asteroids are categorized based on spectra (blue or red) and
albedo, which may be related to the asteroid’s surface
composition.

Originally, they classified only three type of asteroids:
C-type: Carbonaceous (~70% of known asteroids, dark)
S-type: Silicaceous (~20% of known asteroids, bright)
M-type: Metallic

In addition, there are minor groups such as
D-type
 Similar to comet nuclei
V-type
 (4) Vesta-like objects
….
and so on.
Meteorite Classification
Primitive Meteorites Chondrites
Differentiated Meteorites
85%
Carbonaceous
Chondrites
3%
Ordinary
Chondrites
80%
HED 6%
Meteorites
15%
Others
2%
Achondrites
SNC1%
Meteorite
Stony-Iron
Meteorite
2%
Lunar-meteorites
Iron
meteorite
4%
Others
2%
Courtesy of S. Hasegawa (ISAS)
http://www.yamato.nipr.ac.jp
Yamato-82162 (carbonaceous chondrite )
http://www.yamato.nipr.ac.jp
Yamato-790528 (Ordinary chondrite)
http://www.saharamet.com/
Dar al Gani 863 (polymict Eucrite)
http://www.hori.co.jp
Tagish Lake (CI)
(http://www.lpl.arizona.edu/
Baghdad (Iron)
Meteorites
• Meteorites are solid objects originating in outer space that survives
impact with the Earth's surface.
• One of famous: Allende
• Fell in Mexico in 1969
• Huge fireball and shower of stones
• About 2000 kg of rock collected
• Sometimes angle of infall can be reconstructed from camera
recordings. Orbit of meteorite can then be reconstructed.
• Meteorites easily find on ice fields on polar caps(Antarctica)
Meteorites
• Some meteorites originate from Mars or Moon
• Most meteorites were originally part of ~100 km sized
planetesimals (`parent bodies’) that have fragmented.
• Some are from differentiated parent bodies: heat has melted the
material: iron sunk to center: iron meteorites, basaltic meteorites.
• Most are from undifferentiated parent bodies: original build-up
particles:
– Chondrules (mm size spherules)
– Matrix (`cement’ between chondrules: <10 mm particles)
– Calcium-Aluminium-rich Inclusions (CAIs, cm size, rare)
Chondrites
Chondrules+Matrix
Temperature of the proto-planetary disk
Origin and Evolution of Life on Earth
• Materials in Earth should experience high temperature.
• A accretion models for the formation of the Earth and the
single-impact theory of the origin of the Earth-Moon system
predict a volatile-depleted young Earth.
• It is suggested the accumulation of the
organic inventory of the Earth was
likely a mix of exogenic (외인성)
organics with those endogenically (내
인 성 ) synthesized in the early
atmosphere or, perhaps, in other
terrestrial (or deep-sea).
It is likely that the Cretaceous(백악기)-Tertiary (제3기) (K/T)
extinction was caused by an impact of large meteorite (Alvarez et
al., 1980) or a comet (Davis et al., 1984).
Extraterrestrial nonproteinic amino acids were found near the K/T
65 million year old boundary, which may be of ultimate cometary
origin (Zhao and Bada, 1989; Zahnle and Grinspoon, 1990).
Tertiary (제3기)
Cretaceous (백악기)
A Wyoming rock with an intermediate claystone layer that contains 1000 times
more iridium than the upper and lower layers.
Zhao & Bada, Nature 339, 463 - 465 (1989)
Murchison meteorite
•
•
•
•
One of the most studied meteorites due to its large mass (>100 kg)
Collected in 1969
Classified into carbonaceous chondrite
This meteorite experienced extensive alteration by water-rich fluids
on its parent body
• Over 100 amino acids (some of the basic components of life) have
been identified in the meteorite, such as glycine, alanine and
glutamic acid as well as unusual ones on the Earth
• In amino acids there are two optical isomers (이성체),
called L or D amino acids.
• They are mirror images of each other. L-amino acids
represent all of the amino acids found in proteins.
• L-enantiomeric (거울상) excesses have been found in
Murchison.
Miller–Urey experiment
as an endogenous origin
• The Miller–Urey experiment was an experiment that
simulated hypothetical conditions on the early Earth, and
tested for the occurrence of chemical evolution.
• Specifically, the experiment tested a hypothesis that
conditions on the primitive Earth favored chemical reactions
that synthesized organic compounds from inorganic
precursors.
• The experiment used H2O, CH4, NH3,
and H2.
• The chemicals were all sealed inside
glass tubes and flasks connected in a loop.
• There were two flask, one with half-full
of liquid water and another containing a
pair of electrodes.
• The liquid water was heated to induce
evaporation , sparks were fired between
the electrodes to simulate lightning
through the atmosphere.
• At the end of one week of continuous operation, Miller and
Urey observed that as much as 10–15% of the carbon was
now in the form of organic compounds. Two percent of the
carbon had formed amino acids that are used to make
proteins in living cells, with glycine as the most abundant.
Sugars, liquids, and some of the building blocks for nucleic
acids were also formed.
• Both left-handed (L) and right-handed (D) optical isomers
were created in a racemic mixture (note that in nature, L
amino acids dominate).
More than 65 Myr ago
However, dinosaurs suddenly
became extinct probably because …
The estimated impactor's size ~ 10km in diameter
Tunguska event in 1908
The explosion occurred in Siberia. It knocked over an 80 million trees.
It is believed to have been caused by the air burst of a large meteoroid or
comet fragment at an altitude of 5–10 kilometres above the Earth's surface.
meteorites
meteor
Near Earth Asteroid Survey
Kitt Peak Natl. Observatory
LINEAR, New Mexico
LSST
• D>1km 90% done before 2008
• D>0.14km will be surveyed by
2020