The First Cosmic Object Earth by mikesanye

VIEWS: 1 PAGES: 15

									          Recap the Black Holes

   Describe the conditions for a stellar black hole to
    be formed
   Describe the tidal effects and time dilation near a
    black hole
   Describe the X-ray observations of a black hole
   Describe Hawking’s proposal on white holes
   Is there any experimental support for this idea ?
   Discuss the galactic black holes
        Extra-terrestrial Life

   Introduction
   Origin of Life on Earth
   Characteristics of Life
   Biological Evolution
   Extremophiles
   Life in our Solar System
             Introduction

   Astrobiology: interdisciplinary research
    field on exobiology, the study of planets in
    the solar system and beyond, space flights,
    origins of life.
   Exobiology: the study of organisms that
    originate outside Earth. It also encompasses
    SETI.
      Origin of Life on Earth (I)

   Chemical Evolution - the process that manufactured
    molecules and compounds of increasing complexity.
   Supernovas produced heavy atoms, which were
    combined to form molecules and compounds, which
    were subsequently condensed into asteroids, planets
    and new stars.
   Recent astrophysical experiments demonstrated the
    fact that asteroids can contain complex aromatic
    molecules, which could lead to life under certain
    physical conditions (the Miller-Urey experiment)
Origin of Life on Earth (II)
                      Chemosynthesis
                      1st phase:
                      hydrocarbon chains
                      formation from
                      ammonia, water and
                      hydrogen (the Miller
                      - Urey experiment).
                      These complex
                      molecules were
                      formed in the air and
                      accumulated in the
                      oceans.
     Origin of Life on Earth (III)
   2nd phase: simple organic molecules under heat bond
    to create macromolecules peptides proteins, fat
    molecules, complex sugars)
   3rd phase: macromolecules are organized into cells
    which resemble living things (coacervates).
   4th phase: nucleic acids control the reproductive and
    internal activities of coacervates.
   5th phase: natural selection of the cells which can use
    energy most efficiently and reproduce more rapidly.
   6th phase: self-sufficient autotrophic bacteria
          Characteristics of Life

   Composed of cells; 1-cell amoeba
    But viruses do not contain cells and have
    all the other characteristics of life)
 Require energy for metabolism and
 locomotion – ATP molecules
 Sexual or asexual reproduction
 Inherit traits from parents (heredity)
 Respond to stimuli in their environment (light, heat etc)
 Maintain a state of internal balance (homeostasis)

 Adapt to their environment and evolve
            Biological Evolution
   While chemosynthetic theory explains the development of
    life, biological evolution explains the origin of millions
    of life forms.
   Evolution is the progressive change of genes in a population.
    The mechanism that weeds out the positive changes from
    negative changes is natural selection, a concept
    developed by Charles Darwin. This mechanism will ensure
    the survival of the fittest.
   Evolution is slow, gradual change without a clear direction
    (not towards something better, or from simple to complex).
   Contrary to popular belief, humans are not on top of the
    evolutionary ladder; we are just another branch on the bush
    of life. Extra-terrestrial life can be very different.
                       Extremophiles
   Extremophiles are organisms which can live in
    extreme conditions:
       in caves miles underground,
       in sulphuric acid,
       in the hot water heated by submarine volcanoes
        (tube worms)
        in the cold of the Antarctic.
   Humans are limited by the need for oxygen,
    the boiling and the freezing points of water and the low
    tolerance for extreme acidity or alkalinity. But life has evolved
    to fill every possible niche on Earth and this might give an idea
    about ET.
                   The Habitable Zone




As the mass of the star increases the habitable zone moves further from the star.
         Life in the Solar System
   A habitable zone is the region around a star
    where liquid water could exist at the surface.
    Today only Earth has liquid water at the surface.
   The size of the planet and the existence of
    tectonic activities are also important. Too small
    planets do not hold onto an atmosphere, while
    too large planets will pull it to the surface.
   Life could exist outside the habitable zone but we
    expect that it is very different from the life on
    Earth.
                  Life on Mars (I)
   Mars had some tectonic activity long time ago (we can
    still see the volcanoes). The CO2 released by its
    volcanoes heated the atmosphere and allowed for
    water to exist on the surface.
   Images from Mars show riverbeds as evidence that it
    had water in the past.
   Because of a very low density of the atmosphere
    Mars cannot retain heat and today it has an average
    temperature of –60 degrees and no liquid water at the
    surface.
   The Pathfinder mission to Mars initiated the
    examination of soil around riverbeds.
                         Life on Mars (II)

Meteorites were found as coming
from Mars with signs of life
In 1996 NASA announced that a small
meteorite (ALH84001) discovered in Antarctica
contains globules of carbonates, formed by the
decompo-sition of bacteria on Mars. Other
scientists formulated other theories about the
creation of these carbonates (they used the fact
that the size of these bacteria was too small) and
the debate is still open.




Panspermia is a theory which
supports the idea that life is spread
through meteorites.
               Life on Venus
   Like Mars, Venus has an atmosphere of CO2, but
    unlike Mars its atmosphere is extremely dense.
   Being closer to the Sun, Venus has higher
    temperatures, which not only evaporates water but
    also causes volcanoes activity. This leads to CO2 and
    the greenhouse effect which further increases the
    surface temperature (average 482 degrees !).
   On Earth we have biogeochemical cycles (carbon and
    nytrogen) which stop the greenhouse effect from
    happening (but industrialization threatens this
    equilibrium)
        Life on Europa and Titan
   There is strong indirect evidence that Europa
    (one of the moons around Jupiter) has an ocean
    under a thick crust of ice. We know that deep
    sea volcanic vents can generate tube worms. But
    Europa ocean has little sources of energy.
   Titan (one of Saturn’s moons) has liquid
    methane and ethane, solid ice, and smog
    particles raining from space. Life there would be
    very different from life on Earth.

								
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