Life on Earth and on other worlds

1
Life on Earth and on other worlds

• Prehistory physical conditions for the Universe
  to be life-friendly
• Life on Earth
• Chances for extraterrestrial life
• Search for other civilizations are we alone in
  the Universe?

2
Do we live in a special universe??

• Change of physical constants by a very small
  amount would
• render impossible the life in the universe as
  we know it
• Adding or subtracting just one spatial dimension
  would make
• the formation of planets and atoms impossible
• Life as we know it needs a universe which is
  large enough, flat,
• homogeneous, and isotropic

3
(No Transcript)
4
Anthropic Principle We observe the universe to
be as it is because only in such a universe could
observers like ourselves exist. That is,
selection effects would say that it is only in
universes where the conditions are right for life
(thus pre-selecting certain universe) is it
possible for the questions of specialness to be
posed.
This is a solution, but can we do better?
5
Do we need a supernatural force?
How, and whether is it possible to cognize a real
world?
Newton, Galileo, Kant, and many others Faith
and scientific reasoning should not interfere
6
When any form of belief (religious, ideological
etc. ) tries to solve scientific problems, the
progress is stopped, and only bad thing
happen From inquisition (Giordano Bruno,
Galileo) to prosecution of genetics, ban on
theory of evolution, quantum mechanics, etc.
Beliefs and rational thinking are two
complementary parts of human personality, but
they should not replace one another
7
History of science teaches us that there is
nothing special in the place we live

• Our local country is nothing special (ancient
  travelers)
• Planet Earth is nothing special (Copernicus)
• Milky Way galaxy is nothing special (Hubble)
• Our part of the Universe is nothing special
• Self-reproducing Universe
• Eternal Big Bang and ensemble of universes

Linde, Vilenkin
8
Landscape of the multiverse
Planck scale
Planck Length
Planck Mass
Planck density 1094 g/cm3
9
Life on Earth
Organization. All living things are organized
and structured at the molecular, cellular,
tissue, organ, system, and individual level.
Organization also exists at levels beyond the
individual, such as populations, communities, and
ecosystems. Maintenance/Metabolism. To overcome
entropy (the tendency of a system to become more
disorganized and less complex), living things use
energy to maintain homeostasis (i.e., maintain
their sameness a constant, structured internal
environment). Metabolism is a collective term to
describe the chemical and physical reactions that
result in life. Growth. Living things grow. The
size and shape of an individual are determined by
its genetic makeup and by the environment.
Response to Stimuli. Living things react to
information that comes from outside or inside
themselves. Reproduction. Individuals reproduce
themselves. Life also reproduces itself at the
subcellular and cellular levels. In some
instances, genetic information is altered. These
mutations and genetic recombinations give rise to
variations in a species. Variation. Living
things are varied because of mutation and genetic
recombinations. Variations may affect an
individual's appearance or chemical makeup and
many genetic variations are passed from one
generation to the next. Adaptation. Living
things adapt to changes in their environment.
10
Physical basis of life on Earth the carbon atom!
Carbon can form long, complex, stable chains of
atoms
Another shared property is that the proteins
found in present-day organisms are fashioned from
one set of 20 standard amino acids. These
proteins include enzymes (biological catalysts)
that are essential to development, survival and
reproduction.
11
Key property information storage and duplication
Replication agent nucleic acids RNA and DNA
The genetic code specifies the amino acid
sequences of all the proteins each organism
needs. More precisely, the instructions take the
form of specific sequences of nucleotides, the
building blocks of nucleic acids. These
nucleotides consist of a sugar (deoxyribose in
DNA, and ribose in RNA), a phosphate group and
one of four different nitrogen-containing bases.
In DNA, the bases are adenine (A), guanine (G),
cytosine (C) and thymine (T). In RNA, uracil (U)
substitutes for thymine. The bases constitute the
alphabet, and triplets of bases form the words.
12
Information Storage and Duplication
All information guiding all processes of life are
stored in long spiral molecules of DNA
(Deoxyribonucleic Acid)
Basic building blocks are four Amino acids
Adenine, Cytosine, Guanine, and Thymine
Information is encoded in the order in which
those amino acids are integrated in the DNA
molecule.
13
Processes of Life in the Cell
Information stored in the DNA in the nucleus is
copied over to RNA (ribonucleic acid) strands,
which acts as a messenger to govern the chemical
processes in the cell.
14
Duplication and Division
In the course of cell division, the DNA strands
in the nucleus (chromosomes) are duplicated by
splitting the double-helix strand up and
replacing the open bonds with the corresponding
amino acids
Process must be sufficiently accurate, but also
capable of occasional minor mistakes to allow for
evolution.
15
When the earth formed some 4.6 billion years ago,
it was a lifeless, inhospitable place. A billion
years later it was teeming with organisms
resembling blue-green algae. How did they get
there? How, in short, did life begin?
16
The Origin of Life on Earth

• Life develops into more complex forms through
  gradual evolution, spanning many thousands of
  generations.

• Life began in the sea as single-celled
  creatures.

• Those as well as early multi-celled creatures
  had no hard parts to leave fossils.

Earliest, microscopic fossils date back 4
billion years.
17
Two advances of the 19th century
In one advance Louis Pasteur discredited the
concept of spontaneous generation. He offered
proof that even bacteria and other microorganisms
arise from parents resembling themselves. He
thereby highlighted an intriguing question How
did the first generation of each species come
into existence? The second advance, the theory
of natural selection, suggested an answer.
According to this proposal, set forth by Charles
Darwin and Alfred Russel Wallace, some of the
differences between individuals in a population
are heritable. When the environment changes,
individuals bearing traits that provide the best
adaptation to the new environment meet with the
greatest reproductive success. Consequently, the
next generation contains an increased percentage
of well-adapted individuals displaying the
helpful characteristics. In other words,
environmental pressures select adaptive traits
for perpetuation. Repeated generation after
generation, natural selection could thus lead to
the evolution of complex organisms from simple
ones. The theory therefore implied that all
current life-forms could have evolved from a
single, simple progenitor - an organism now
referred to as life's last common ancestor.
18
Prehistory
Previous stars supplied heavy elements
Our Solar System has been formed with the Sun
sufficiently long-lived star
One of the planets, the Earth, formed at a
distance from the sun where conditions were
favorable and the necessary chemical ingredients
were available (note illustration's infalling
comet and dust) for the origin of life.
19
The prebiotic earth first billion years
Vigorous chemical activity is represented by the
heavy clouds, which were fed by volcanoes and
penetrated both by lightning discharges and solar
radiation. The ocean received organic matter from
the land and the atmosphere, as well as from
infalling meteorites and comets. Here, substances
such as water, carbon dioxide, methane, and
hydrogen cyanide formed key molecules such as
sugars, amino acids, and nucleotides. Such
molecules are the building blocks of proteins and
nucleic acids, compounds ubiquitous to all living
organisms. A critical early triumph was the
development of self-replicating RNA molecule,
which directed biological processes and preserved
life's "operation instructions" for future
generations.
20
The Miller Experiment
Miller Experiment in 1952 Simulating conditions
on Earth when life began 4 billion years ago
Experiment produced some of the fundamental
building blocks of life amino acids, fatty
acids, and urea.
Water (oceans), primitive atmosphere gases
(hydrogen, ammonia, methane), and energy from
electric discharges (lightning).
21
The Origins of Life on Earth (3)

• Miller experiment shows that basic building
  blocks of life form naturally.
• Amino acids and other organic compounds
  naturally tend to link up to form more complex
  structures.

• Early oceans on Earth were probably filled with
  a rich mixture of organic compounds the
  Primordial Soup
• Chemical evolution leads to the formation and
  survival of the most stable of the more complex
  compounds.

22
Extraterrestrial Origin of Life on Earth

• Alternative theory Most primitive living
  entities transported to Earth in meteorites or
  comets.

• Some meteorites do show traces of amino acids.

• Theory of extraterrestrial origin of life is
  currently untestable.

23
Early evolution of life
Most of life's history involved the biochemical
evolution of single-celled microorganisms. We
find individual fossilized microbes in rocks 3.5
billion years old, yet we can conclusively
identify multicelled fossils only in rocks
younger than 1 billion years. The oldest
microbial communities often constructed layered
mound-shaped deposits called stromatolites, whose
structures suggest that those organisms sought
light and were therefore photosynthetic. These
early stromatolites grew along ancient seacoasts
and endured harsh sunlight as well as episodic
wetting and drying by tides. Thus it appears
that, even as early as 3.5 billion years ago,
microorganisms had become remarkably durable and
sophisticated!
24
Advanced life last 500 million years
Trilobites among the first complex organisms
25
The Origin of Life on Earth (2)
1/2 billion years ago, in the Cambrian Period,
the diversity and complexity of life on Earth
dramatically increased ?Cambrian Explosion
Best-known fossils from the Cambrian period
Trilobites.
All known fossils from the Cambrian period are
from sea creatures.
No traces of life on land until 400 million
years ago.
26
Geologic Time
In geologic terms, higher life forms, in
particular mammals and humans, have evolved only
very recently.
Humans have existed for only 3 million years.
27
Three Questions About the Evolution of Life
1) Could life originate on another world if
conditions were suitable?
Miller experiment etc. indicate probably yes.
2) Will life always evolve toward intelligence?
If intelligence favors one species over another
probably yes.
3) How common are suitable conditions for the
beginning of life?
? Investigate conditions on other planets and
statistics of stars in our Milky way
28
Habitable planet should have
a stable temperature regime and a liquid to
mix the essential building block elements
together (carbon, hydrogen, nitrogen, oxygen,
phosphorus, sulfur, and transition metals like
iron, chromium, and nickel). The planet should
have a solid surface to concentrate the building
block elements together in the liquid on top. The
more concentrated the solution of water and
molecules is, the more likely the molecules will
react with each other. If the molecules were
fixed in a solid, they would not be able to get
close to each other and react with each other. If
the molecules were in a gaseous state, they would
be too far apart from each other to react
efficiently. Though the reactions could
conceivably take place, they would be rare! The
planet should also have enough gravity to keep an
atmosphere.
29
Life in Our Solar System
Other planets or their moons are unlikely to have
ever provided suitable conditions for life.
Most promising candidate Mars.
Claimed traces of microscopic fossils may well be
regular mineral formations in the rock.
Meteorite ALH84001,0 probably originated on Mars.
Possibly some evidence of past life on Mars, but
questionable.
30
Jupiters Family of Moons
Over two dozen moons known now new ones are
still being discovered.
Four largest moons already discovered by Galileo
The Galilean moons
Io
Europa
Ganymede
Callisto
Interesting and diverse individual geologies.
31
Europa heated internally, therefore the surface
is soft No vertical surface features can
survive! Surface is smooth as a skating rink
Fig. 18-10a, p.389
32
The Interior of Europa
Europa is too small to retain its internal heat ?
Heating mostly from tidal interaction with
Jupiter.
Core not molten ? No magnetic field.
Europa has a liquid water ocean 15 km below the
icy surface.
33
Titan

• About the size of Jupiters moon Ganymede.
• Rocky core, but also large amount of ice.
• Thick atmosphere, hiding the surface from direct
  view.

34
Titans Atmosphere
Because of the thick, hazy atmosphere, surface
features are only visible in infrared images.
Many of the organic compounds in Titans
atmosphere may have been precursors of life on
Earth.
Surface pressure 50 greater than air pressure
on Earth
Surface temperature 94 K (-290 oF)
? methane and ethane are liquid!
Methane is gradually converted to ethane in the
Atmosphere
? Methane must be constantly replenished,
probably through breakdown of ammonia (NH3).
35
(No Transcript)
36
How Many Of Them Are Out There?

• 200 billion stars in the Milky Way
• Planetary systems are common
• However not all stars and all planets are
  suitable for life!

37
Amount of hydrogen fuel
Lifetime
Rate of energy loss
Lifetime T M/L 1/Mp-1 1/M2.5 p 3.5
T 3x108 years
M 4M?
38
Good stars should live long 0.5 to 1.4 solar
masses Binary stars are probably excluded Only
metal-rich Population I stars contain heavy
elements
39
G and K stars are most suitable
40
Requirements for Life in Other Planetary Systems

• Planetary systems are probably common.

• Stable orbit around the star ? consider only
  single stars.

• Time for evolution ? consider only F5 or less
  massive stars.

• Moderate temperatures ? Life zone around the star

41
The Drake Equation
Factors to consider when calculating the number
of technologically advanced civilizations per
galaxy
Nc N fp nLZ fL fl FS
Most of the factors are highly uncertain.
Possible results range from 1 communicative
civilization within a few dozen light years to us
being the only communicative civilization in the
Milky Way.
42
Other factors global catastrophe mass
extinctions
43
(No Transcript)
44
Mass extinctions once every 100 million
years Asteroid or comet of 10 km size?
45
(No Transcript)
46
150 known impact sites on the earth
Diameters from 50-70 m to 200 km
47
Barringer crater, Arizona 49,000 yr old Iron
meteorite of size 50 m, mass 300,000 ton Impact
velocity 11 km/sec Over 30 tons of fragments found
Fig. 19-12b, p.426
48
The K-T Event and the Cretacious-Tertiary mass
extinction 65 million years ago
Sixty-five million years ago, about 70 percent of
all species then living on Earth disappeared
within a very short period in what is termed the
Cretaceous-Tertiary Mass Extinction---commonly
known as the K-T Event (K is used to denote the
Cretaceous period rather than C to avoid
confusion with other periods such as the
Cambrian). Among the species that disappeared
were the last of the dinosaurs. The cause of this
and other sudden species extinctions has long
been an important and controversial topic. In
1980, physicist Luis Alvarez and coworkers
reported finding a very high concentration of the
element iridium in the sedimentary clay layer
laid down at the time of the K-T extinction. On
Earth, iridium is very rare in the crust because
it was concentrated in Earth's core when it was
largely molten. However, chondritic meteorites
often still have the primordial solar system
abundances of these elements. This led Alvarez et
al to suggest that a chondritic asteroid 10
kilometers in diameter that struck the Earth in
the K-T period would contain enough iridium to
account for the worldwide clay layer iridium
enhancement, and that this meteor impact could
also have triggered dramatic climatic changes
that produced the K-T extinction.
49
K/T boundary clay layer (Italy)
Places where the sediments were found
50
Further evidence Sites near the Brazos River in
Texas show a thick layer of unusual sediment
immediately underneath the iridium layer. This
sediment was formed by a massive tsunami (tidal
wave), caused by the impacting object. Sites in
Beloc, southern Haiti, also show tsunami debris
together with large quantities of ejected
material such as shocked quartz and tektites.
spherules
tectites
Shocked quartz
51
Fig. 19-13b, p.426
52
Gravity anomaly over the Chicxulub crater
53

• World-wide fires
• 1-km-hign tsunamis
• Acid rains and atmospheric pollution
• Darkness and severe winter for many decades

54
Sandia simulation of 1-km asteroid hitting the
Atlantic near New York
15 deg grazing impact
Distant and head-on view at .4 seconds after
impact
Orange above 5000o C
Distant and head-on view at 2.4 seconds after
impact
Distant and head-on view at 8.4 seconds after
impact
55
What is the current statistics?
56
Remains of a failed planet?
2.8 AU from the Sun
57
Earth-crossing asteroids
By estimate, the entire population of
Earth-crossing asteroids includes some 1500
larger than one kilometer and 135,000 larger than
100 meters in diameter.
Toutatis one of the closest. 5 km diameter Next
close flyby 29 Sept. 2004, 4 lunar distances
from Earth
58
Potentially Hazardous Asteroids (PHAs) are those
with an Earth Minimum Orbit Intersection Distance
(MOID) of 0.05 AU or less and an absolute
V-magnitude of 22.0 or higher (indicating that
they are greater than around 100m across). Most
PHAs are detected after they have already passed
the Earth. On August 7 1994, asteroid 1994 XM1
reached a minimum distance of 0.0026 AU (112000
km) from the Earth. This object is estimated to
be about 10 m across. If it had collided with the
Earth, the impact energy would have been
equivalent to about four Hiroshima bombs. The
resulting crater would have been hundreds of
metres across - devastating to a major city. The
closest known forthcoming approach will be on 7
August 2027 when a PHA will pass within 0.0024 AU
(roughly 360,000 km) from the Earth. This is less
than the distance from the Earth to the Moon.
59
The Peekskill meteorite
October 9, 1992 12 kg chondrite meteorite reached
the earth
60
Are we a communicative civilization?

• Not really

61
A message in a bottle cast into the cosmic sea
12-inch gold disk carried by Voyagers I and II
62
Communication with Distant Civilizations

• Direct space travel to other stars not feasible
  due to large distances (long travel times).

• Viable alternative Radio communication.

• Even for radio communication Long answer times
  due to light-travel time.

• Messages can be arranged in blocks of certain
  length that is a product of two prime numbers ?
  Only two ways to arrange them in a rectangle.

63
Arecibo Radio Telescope
In 1974 Arecibo sent a message to the globular
cluster M13 in Hercules (300,000 stars)
64
The Arecibo Message
At dedication of Arecibo Radio Observatory,
blocks of 1679 pulses were emitted, which can be
arranged in only two ways
23 rows of 73or 73 rows of 23.
Resulting 23 x 73 grid contained basic
information about our human society.
65
Distance to M13 is 25,000 ly
66
Search for Extraterrestrial IntelligenceSETI

• Searching for radio signals in the microwave
  range
• Annual cost the cost of a helicopter
• Yet there is no funding from any government