Cosmos test 2

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Mdickson
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51219
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Cosmos test 2
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2010-11-22 19:54:17
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Cosmos test
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Notes for second midterm in NSCI 314
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  1. When did life begin?
    • -
    • Stromatolies say 3.5 but more controversial evidence
    • using microfossils and isotopes have evidence of at least 3.85 billion years
    • ago
  2. Stromatolites
    • -
    • Rocks that are characterized by a distinctive, layered
    • structure

    • -
    • Living stromatolites – contain layers of sediments
    • intermixed with different types of microbes
  3. Microfossils
    • microscopic fossil, hard to find because rocks
    • become rare with age, so they tend to get destroyed
  4. Isotopic evidence
    • -
    • isotopic analysis of ancient rocks on earth

    • o Living
    • organizism can change the ratios of isotopes
  5. What did early life look like?
    • -
    • resembled modern extermophiles living in hot water near
    • deep-sea vents or in hot springs
  6. Where did life begin?
    • -
    • Deep-sea vents or hot
    • springs

    • -
    • They would have protected from impact that might
    • vaporize surface hot springs
  7. How did life begin?
    • -
    • Organic molecule were found in ocean locations where
    • clay and other minerals were common

    • -
    • Clay helped catalyze the building of RNA strands that
    • became enclose in lipid pre-cells.

    • -
    • Some RNA strands were able to self-replicate allowing
    • natural selection
  8. Could life have migrated to earth?
    • -
    • originating from Venus or Mars could survive the
    • journey

    • -
    • highly unlikely from longer migrations
  9. What major events have marked involuntary history?
    • -
    • life diversified rapidly after its origin, but remained
    • microscopic for more than 2 billion year.

    • -
    • Oxygen-producing photosynthesis – released the oxygen
    • now in our atmosphere

    • -
    • Multicellular animals diversified in the Cambrian
    • explosion, starting about 545 million year ago
  10. Why was the rise of oxygen so important to evolution?
    • -
    • Aerobic processes = more efficient cellular energy
    • production than anaerobic processes

    • o Lead
    • to much greater evolutionary diversification

    • -
    • Rise of oxygen began before 2.35 billion years ago

    • o Did
    • not reach levels like present until after the Cambrian explosion
  11. Where do we expect to find building blocks of life?
    • -
    • Almost any world

    • o But
    • small numbers of worlds contain more complex organic molecules

    • -
    • The fact that they are present in asteroids and comets
    • suggest that we’ll find them many places
  12. Where can we expect to find energy for life?
    • -
    • Sunlight

    • o Weakens
    • with distances from sun & unlikely to be sufficient at large distances

    • -
    • Chemical energy

    • o Probably
    • available in more places, likely on any world with a substantial atmosphere or
    • liquid medium that can mix and support chemical reactions
  13. Does life need liquid water?
    • -
    • yes

    • -
    • 3 Advantages

    • o A
    • wider & higher range of temps in which it is liquid

    • o Fact
    • that ice floats

    • o The
    • type of chemical bonding made possible by charge separation within water
    • molecules

    • -
    • Cannot rule out other liquids: Liquid ammonia, methane
    • or ethane
  14. What are the environmental requirements for habitability?
    • -
    • main requirement when looking for habitable worlds:
    • possibility of liquid water

    • -
    • Life requires:

    • o Molecules
    • from which to build living cells

    • o A
    • source of energy for metabolism

    • o Liquid
    • medium for transporting chemicals
  15. Does life seem plausible on the moon or Mercury?
    • -
    • No, since neither has liquid water or any other liquid
    • medium for life
  16. Could life exist on Venus or Mars?
    • -
    • Not on Venus, it is too hot for liquid water to exist
    • on or under the surface

    • -
    • Might be in Venus’s atmosphere, where clouds contain
    • droplets of water.

    • -
    • Mars had habitable conations in the past and might
    • still have it underground
  17. Could there be life in the atmosphere of the Jovian planets?
    • -
    • Jovian plants = have depths at which liquid water can
    • exist in their atmosphere

    • -
    • Strong vertical winds makes life seem unlikely
  18. Could there be life on the jovian moons or other small
    bodies of the solar system?
    • -
    • A few large moons may contain liquid water, so maybe

    • -
    • Smaller moons don’t have any liquid

    • -
    • There may have been liquid water in the distant past
  19. How did we get the idea there could be life on Mars?
    • -
    • Superficial similarities between mars and earth led to
    • speculation
  20. Who was Percival Lowell?
    • -
    • Thought he saw canal built by an advanced society, but
    • the canals do not really exist
  21. What is Mars like today?
    • -
    • Cold and dry

    • -
    • Atmospheric pressure so low that water is unstable.

    • -
    • Weather is driven largely by seasonal changes
  22. What are the main geological features?
    • -
    • Densely cratered and must be very old

    • -
    • Other regions with fewer craters must be much younger

    • -
    • Giant volcanoes on certain regions

    • -
    • Evidence of past tectonics, which probably created
    • Valles Marineris
  23. What evidence do we have there use to be water on the
    surface of mars?
    • -
    • Orbiting images of eroded craters, dry river channels

    • o Supporting
    • evidence found in chemical analysis of Martian rocks

    • -
    • Periods of rain fall ended at least 2-3 billion years
    • ago

    • -
    • Still has water ice underground
  24. Why/How was Mars warmer and wetter in the past?
    • -
    • Atmosphere was once much thicker with a much stronger
    • greenhouse affect

    • o Don’t
    • know if this really made Mars warmer or wetter
  25. Why did Mars change?
    • -
    • Loss of atmospheric gas, which weakened the greenhouse
    • affect

    • -
    • Some blasted away with impact others stripped away from
    • solar wind

    • Water was lost because ultraviolet light could break
    • apart water molecules
  26. Is Mars Habitable today?
    • -
    • May have habitable regions today
  27. Is there evidence of life on Mars?
    • -
    • Viking experiments produced results some scientist
    • think may be evidence of life, but non biological explanations seem more likely

    • -
    • No definitive evidence
  28. Is there evidence for life in Martian meteorites?
    • -
    • 4 types of evidence from ALH84001

    • o The
    • carbonate grains have a layered structure; which on earth this type of layering
    • generally occurs only as a result of biological activity

    • o Carbonate
    • grains contained PAHs

    • o They
    • saw crystals of the mineral magnetite within the iron-rich layers of the
    • carbonate grains; resemble the ones produced by earth bacteria

    • o Saw
    • rod-shaped structures that look much like recently discovered “nanobacteria” on
    • earth

    • -
    • But each also has a potential non biological
    • explanation, so they don’t have a definitive answer
  29. General characteristics of Jovian Moons
    • -
    • Range greatly in size

    • -
    • Tend to have ice mixed in with their rocks

    • -
    • Nearly all are in Synchronous rotations

    • o Keeping
    • 1 side continually turned toward their host planet
  30. What makes some of the Galiean Moons warm enough inside to
    possibly harbor life?
    • -
    • Some moons retain internal heat as a result of tidal heating, along with radioactivity


    • -
    • A few moons have liquid water, minimum requirements for
    • life
  31. Does Europa have an ocean?
    • -
    • Surface show numerous features, including relative lack
    • of impact craters, suggesting that liquid or slush from below has gathered up

    • -
    • It has a magnetic field that assumes it has a salty
    • ocean

    • -
    • Most likely
  32. Could Europa have life?
    • -
    • it has liquid water and elements necessary for life, an
    • energy source for life is very limited compared to earth
  33. Could other moons of Jupiter have life?
    • -
    • Ganymed (largest moon in SS) is much like Europa, like
    • an icy crust

    • o A
    • change in its magnetic field suggest it has salty oceans under ground

    • -
    • Callisto (Farthest out of the Galilean moons, no tidal
    • heating

    • o Magnetic
    • measurements suggest a possible hidden ocean

    • -
    • Could conceivably offer conditions but low energy
    • source
  34. Characteristics of Titan
    • -
    • Has an atmosphere even thicker than earth

    • o But
    • largely composed of nitrogen, argon, ethane and methane
  35. Could Titan have life?
    • -
    • Huygens probe showed that fluid hydrocarbons on the
    • landscape

    • o Bitter
    • cold temps would greatly slow chemical reactions

    • o This
    • would make metabolism difficult decreasing the chances for life

    • -
    • It is possible that pockets of liquid water and
    • subsurface oceans of cold ammonia/water mixture

    Some energy source fore life might be available

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