Cosmos test 2
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Cosmos test 2
Notes for second midterm in NSCI 314
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
Rocks that are characterized by a distinctive, layered
Living stromatolites – contain layers of sediments
intermixed with different types of microbes
microscopic fossil, hard to find because rocks
become rare with age, so they tend to get destroyed
isotopic analysis of ancient rocks on earth
organizism can change the ratios of isotopes
What did early life look like?
resembled modern extermophiles living in hot water near
deep-sea vents or in hot springs
Where did life begin?
Deep-sea vents or hot
They would have protected from impact that might
vaporize surface hot springs
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
Could life have migrated to earth?
originating from Venus or Mars could survive the
highly unlikely from longer migrations
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
Why was the rise of oxygen so important to evolution?
Aerobic processes = more efficient cellular energy
production than anaerobic processes
to much greater evolutionary diversification
Rise of oxygen began before 2.35 billion years ago
not reach levels like present until after the Cambrian explosion
Where do we expect to find building blocks of life?
Almost any world
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
Where can we expect to find energy for life?
with distances from sun & unlikely to be sufficient at large distances
available in more places, likely on any world with a substantial atmosphere or
liquid medium that can mix and support chemical reactions
Does life need liquid water?
wider & higher range of temps in which it is liquid
that ice floats
type of chemical bonding made possible by charge separation within water
Cannot rule out other liquids
: Liquid ammonia, methane
What are the environmental requirements for habitability?
main requirement when looking for habitable worlds:
possibility of liquid water
from which to build living cells
source of energy for metabolism
medium for transporting chemicals
Does life seem plausible on the moon or Mercury?
No, since neither has liquid water or any other liquid
medium for life
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
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
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
How did we get the idea there could be life on Mars?
Superficial similarities between mars and earth led to
Who was Percival Lowell?
Thought he saw canal built by an advanced society, but
the canals do not really exist
What is Mars like today?
Cold and dry
Atmospheric pressure so low that water is unstable.
Weather is driven largely by seasonal changes
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
What evidence do we have there use to be water on the
surface of mars?
Orbiting images of eroded craters, dry river channels
evidence found in chemical analysis of Martian rocks
Periods of rain fall ended at least 2-3 billion years
Still has water ice underground
Why/How was Mars warmer and wetter in the past?
Atmosphere was once much thicker with a much stronger
know if this really made Mars warmer or wetter
Why did Mars change?
Loss of atmospheric gas, which weakened the greenhouse
Some blasted away with impact others stripped away from
Water was lost because ultraviolet light could break
apart water molecules
Is Mars Habitable today?
May have habitable regions today
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
Is there evidence for life in Martian meteorites?
4 types of evidence from ALH84001
carbonate grains have a layered structure; which on earth this type of layering
generally occurs only as a result of biological activity
grains contained PAHs
saw crystals of the mineral magnetite within the iron-rich layers of the
carbonate grains; resemble the ones produced by earth bacteria
rod-shaped structures that look much like recently discovered “nanobacteria” on
But each also has a potential non biological
explanation, so they don’t have a definitive answer
General characteristics of Jovian Moons
Range greatly in size
Tend to have ice mixed in with their rocks
Nearly all are in Synchronous rotations
1 side continually turned toward their host planet
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
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
Could Europa have life?
it has liquid water and elements necessary for life, an
energy source for life is very limited compared to earth
Could other moons of Jupiter have life?
Ganymed (largest moon in SS) is much like Europa, like
an icy crust
change in its magnetic field suggest it has salty oceans under ground
Callisto (Farthest out of the Galilean moons, no tidal
measurements suggest a possible hidden ocean
Could conceivably offer conditions but low energy
Characteristics of Titan
Has an atmosphere even thicker than earth
largely composed of nitrogen, argon, ethane and methane
Could Titan have life?
Huygens probe showed that fluid hydrocarbons on the
cold temps would greatly slow chemical reactions
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