Transcript Scale of Terrain on Mars

Mirach
(Beta Andromedae)
 ~ 200 light-years distant
 red giant star
 cooler than the Sun
 much larger than Sun
therefore, intrinsically
much brighter than the Sun.
faint, fuzzy galaxy lies
along same line of sight,
but much more distant
diffraction spikes visible
diffraction spikes: optical aberration caused by light diffracting
around the support vanes of the secondary mirror.
Primary
mirror
Secondary
mirror
Homework #7
Due next Monday, 10:00 pm
Exam #2: Thursday, Nov. 4
Review Session Tuesday evening
Room & time to be announced
The “Cambrian Explosion”
Began: ~ 545 million Yr ago
Duration: ~ 40 million years
 Explosion of life forms
 Animal branch of the tree of life came into being
 All known body plans made appearance in fossil
record in a time span of 40 million years
Colonization of Land
Life flourished where liquid water existed
Life on land was more complicated
 Had to develop means of collecting solar energy above
ground and nutrients below
Life in shallow ponds or edges of lakes
 Water evaporates
 Natural selection favored that which could withstand
periods of drought
 DNA evidence suggests that plants evolved from an
algae
 It took only 75 million Yrs for animals to follow plants
out of water
Mass Extinctions
Mass Extinctions
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Possible Causes
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Impacts
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Impact sites found for K-T boundary
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Suspected for Permian extinction 245 mill yr ago
Active volcanism
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Climate change
External influence for copying errors
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Increase in solar particles or radiation hitting surface
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Local supernova
Primate Evolution
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Monkeys, apes, lemurs and humans have
common ancestor that lived in trees
Tree life
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Limber arms for swinging between branches
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Eyes in front of head for depth perception
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Offspring would be born more helpless than other
animals
Emergence of Humans
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Did NOT evolve from gorillas or monkeys
Share a common ancestor that lived just a few
million years ago
98% of human genome is identical to genome of
the chimpanzee
2% difference in genome separates the success of
humans verses chimps
–
Also indicates evolution of intelligence is complex
Emergence of Humans
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After hominids diverged from chimps and gorillas,
evolution has followed a complex path
Numerous hominids species existed, some during the
same time period
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All humans are the same species
First skull fossils that are identical to modern human
skulls dates to 100,000 yr old
Our ancestors shared the Earth with Neanderthals
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Went extinct 35,000 years ago
Cultural and Technological Evolution
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Humans have not undergone biological evolution in
40,000 years
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Dramatic cultural changes
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Mutation rates are slow
Transmission of knowledge between generations
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Spoken to written word, thousands of years
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agriculture
Technological evolution
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Result of coupling between science and technology
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About 100 years between industrial revolution to landing on
the Moon and generating weapons of mass destruction
Life in the Solar System?
Essentials for life
Chemicals / Nutrients
Energy
Liquid solvent
• Chemical components of cells:
– Oxygen
– Carbon
– Nitrogen
– Hydrogen
These elements make up 96% of the mass of
living organisms on Earth.
Where can we expect to find the necessary
ingredients/chemicals for life?
• These elements are abundant in the Universe,
except in older star systems
• As long as condensation and accretion occur
during a star system’s formation, we can expect
these elements to be present
• Organic molecules (building blocks for amino
acids) have been found in asteroids and comets
What are the energy requirements for life?
• Sunlight (photosynthesis)
• Consuming organic molecules (ex. eating plants)
• Chemical reactions with inorganic compounds of
iron, sulfur, or hydrogen
Sunlight?
Light most intense near
the sun (or another
star)
Light intensity falls off
with distance from the
Sun/star, going as
1/(distance)2
Inefficient far from a
star
Where can we expect to find energy for life?
• Chemical Energy
requires a means for
chemicals to mix &
interact
• Atmospheres and/or
bodies of liquids can
provide this means
What to use as a
solvent?
Liquids exist only in specific temperature and pressure
ranges. On the surface of a planet or moon, temperature
alone is insufficient for the presence of liquids.
• On Earth, all life requires water:
 Water dissolves organic molecules so they can be used
for chemical reactions in cells
 Water transports chemicals into and out of cells
 Water is directly involved in many metabolic reactions
within cells
 On
Earth, the only other common liquid is
molten rock (too hot)!
Alternative Liquids for Life
(under 1 atmosphere pressure)
Substance
Freezing
Temperature
Boiling
Temperature
Width of Liquid
Range
Water (H2O)
0C
100 C
100 C
Ammonia (NH3)
-78 C
-33 C
45 C
Methane (CH4)
-182 C
-164 C
18 C
Ethane (C2H6)
-183 C
-89 C
94 C
Water remains liquid over broader and higher
range of temperatures
The higher temperature range for liquid water
allows faster rates of chemical reactions

On colder worlds (e.g.,
Titan), other liquids
may be more common,
such as
 Ammonia NH3
 Methane CH4
 Ethane
C2H6
Chemical reactions are
highly temperature
sensitive, so on colder
worlds with other
liquids, reaction rates
may be too slow for
life.
ethane/methane
lakes on Titan
•
Advantages of water:
1. Water remains liquid over the widest range of
temperatures
2. Water is liquid at a higher temperature than the others.
High temp makes chemical reactions easier.
3. Water is less dense when it freezes (ice floats),
allowing life to survive in the water under the ice
4. Ice insulates the water
underneath, making it
less likely to freeze all
the way, promoting
greater climate stability
5. Water is POLAR. Many
substances can
dissolve in water, but
many do not. Cell
membranes do not
dissolve in water.
Earth-like cells can only
survive in water.
 Water is the most likely candidate liquid for life.
 Searching for liquid water may be the best
approach to searching for life.
 We do not know if other liquids can support life.
Time to begin the search!
Is life possible on Mercury or the
Moon ?
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Small (weak gravity)
Airless
Heavily cratered
No significant tectonic activity
No volcanic gases to form an atmosphere
No liquids likely anywhere
Is Life Possible on Venus?
• Runaway greenhouse effect: too
hot!
• High Pressure
• Life might be possible in upper
clouds (though very acidic)
• Conditions better in early times
when the Sun was not as bright
Is Life Possible On Mars?
Is life possible on Mars?
Once had a thicker and
warmer atmosphere and
liquid water
Liquid water may still
exist underground
Mars: A home to life?
For a good and wide-ranging discussion of Mars, check out
www.spacetoday.org/SolSys/Mars/Mars.html
The Canals of Mars
• In 1877, the Italian astronomer Giovanni
Schiaparelli announced that he saw canali on
Mars.
• Canali means "channels" (a natural waterway)
in Italian, but was promptly mistranslated into
English as "canals" (a constructed waterway)
The most famous
proponent of the Martian
canals was the American
Percival Lowell (18551916), who took up
astronomy after reading
Schiaparelli, and founded
an observatory in
Flagstaff, AZ to study the
canals.
Lowell reported seeing a
great many canals,
intersecting at junctions he
referred to as ‘oases’.
He published 3 famous & well
read books describing the
canals and arguing for life on
Mars.
• Mars (1895)
• Mars and its Canals (1906)
• Mars as the Abode of Life (1908)
The works of Schiaparelli & Lowell formed the basis of the popular
view of life on Mars. This was carried over into the popular literature
(e.g., War of the Worlds by H.G. Wells and many subsequent works.
Unfortunately, Lowell was wrong.
• Very few other astronomers reported seeing these
canals.
• Those that did were inevitably using small telescopes
and/or observing under adverse atmospheric
conditions.
• Mars was is cold and has too little atmophere for
canals to work.
• Long after most astronomers ceased to believe in
canals, popular media continued to speculate about
the canals.
• Much of current knowledge stems from robotic
missions to Mars:
– Viking (1976-78): 2 landers and 2 orbiters
– Mars Pathfinder (1997): lander & rover
– Mars Global Surveyor (1997 - ): orbiter
– Mars Explorer rovers (Jan. 2004 - ):
• Spirit
• Opportunity
– Mars Reconnaissance
Orbiter (Jan. 2007 - ):
orbiter
– Human mission (2025)?
An overview of what we know today…
– Two major terrains
• Southern Hemisphere: Ancient, heavily cratered highlands, ~ 4km
higher than northern hemisphere
• Northern hemisphere: younger, lightly cratered volcanic plains
– Surface Features
• Craters, impact basins, uplifted
regions, volcanoes, mountains,
canyons, polar ice caps, river
beds, flood plains
The Tharsis Bulge is a massive uplifted region the size of North
America, right between the northern plains and southern uplands.
The Tharsis area bulges 10 km above its surroundings and is one
of the least cratered (youngest) terrains on Mars. Surface less
than 1 Byr old.
Three of Mars’
four great
volcanoes are
located here
and the forth,
Olympus
Mons, is offset
on the NW
slope.
What is the cause of the Tharsis bulge?
1.A bulge of the crust due to a mantle plume, and
a build-up of layers of lava.
 We believe that the uplift began about 3 billion years (Gyr)
ago, and continued to 1 Gyr ago, before the formation of the
actual volcanoes.
 On Earth and Venus, compressional forces produce
uplifted terrain, such as Tibet and Lakshmi, with high
mountains.
On Mars however, the highest features are volcanic, not
compressional in origin.
• Volcanoes
Including the tallest volcano in the solar system
– Olympus Mons: 24 km tall, 500 km wide, a 6 km cliff at its base
Scale of Terrain on Mars
The figure below compares Olympus Mons with Everest (fold
mountain) and Mauna Loa (shield volcano) on Earth.
Calculations show that on Earth, and Venus, mountains can only
rise 10-15 km before the rock begins to deform under its own
weight.
Mountains on
Mars can get so
big because the
Martian gravity is
only 40% that of
the Earth.
• Cracks & Canyons
– Valles Marineris: 3000 mi long, 60 mi wide, 4 mi deep
– Origin - not running water but vertical tectonics
• The only ‘canal’of
Lowell’s to exist.