Transcript Power Point Presentation

Astronomy 305/Frontiers in Astronomy
Class web site:
http://glast.sonoma.edu/~lynnc/courses/a305
Office: Darwin 329A and NASA E/PO
(707) 664-2655
Best way to reach me:
[email protected]
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Prof. Lynn Cominsky
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Astrobiology Questions (3 weeks)
Is there life elsewhere in our Solar
system? (Group 5)
 Are Earth-like planets common? (Group
6)
 Are we alone? (Group 7)
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Is there life elsewhere in the solar
system? What is life? Activity #1
In groups of 3-4 students, develop a common
set of characteristics that can identify life
 Write these characteristics down on your
worksheets
 Test your definition by asking 5-10 questions
– one group thinks of something that is alive
or not, and a second group asks them
questions about the characteristics to see if
they can correctly determine the answer
 NOTE: you cannot ask “Is it alive?”
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Group 5
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What is Life?
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Some good criteria:
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Has heritable traits that can be transferred
Able to have a population that evolves and adapts to
the external environment
Uses energy to maintain an internal state
Some pretty good criteria:
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Has a complex internal structure (icicles?)
Has cell membranes or walls that create an internal
environment (viruses?)
Able to extract energy from the environment (fire?)
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What is Life?
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Some not-so-good criteria:
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Moves independently (plants?)
Takes in nutrients (fire?)
Gives off energy (fire?)
Produces waste products (fire, icicles?)
Also on Earth, all life:
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Has Carbon-based chemistry
Requires liquid water
LIVING MATTER EVADES THE DECAY TO
EQUILIBRIUM
- Erwin Schrodinger (famous physicist)
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What is life? Activity #2
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Examine the three jars – you can smell and
touch the contents, but do not taste them
Now add hot water to cover the contents
Record your observations on the worksheet
Use your list of characteristics to determine if
there is anything alive in jars 1, 2 or 3
How can you distinguish between a living and
non-living chemical change?
Refine your definition of life based on these
activities and write it on your worksheet
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Schrodinger on What is Life?:
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What is the characteristic feature of life?
When is a piece of matter said to be alive?
When it goes on 'doing something', moving,
exchanging material with its environment,
and so forth, and that for a much longer
period than we would expect an inanimate
piece of matter to 'keep going' under
similar circumstances. When a system that
is not alive is isolated or placed in a
uniform environment, all motion usually
comes to a standstill very soon as a result
of various kinds of friction;
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Schrodinger on What is Life? (cont’d)
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differences of electric or chemical
potential are equalized, substances which
tend to form a chemical compound do so,
temperature becomes uniform by heat
conduction. After that the whole system
fades away into a dead, inert lump of
matter. A permanent state is reached, in
which no observable events occur. The
physicist calls this the state of
thermodynamical equilibrium, or of
'maximum entropy'.
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Solar System
diameter ~5.9 x 109 km
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Solar System
Relative sizes and order of planets
Sun Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto
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Solar System
Planet
Distance
(103 km)
Mercury
Orbital Period Diameter
(days)
( km)
Mass
Moons
(kg)
57910
87.97
4,880
3.30e23
0
Venus
108200
224.70
12,104
4.869e24
0
Earth
149600
365.26
12,756
5.9736e24
1
Mars
227940
686.98
6,794
6.4219e23
2
Jupiter
778330
4332.71
142,984
1.900e27
61
Saturn
1429400
10759.50
120,536
5.68e26
31
Uranus
2870990
30685
51,118
8.683e25
21
Neptune 4504300
60190
49,532
1.0247e26
11
Pluto
90800
2274
1.27e22
1
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Solar System habitability factors
• Liquid water (geothermal or atmospheric cycles)
• Nutrients (chemicals, vitamins, minerals, fertilizers)
• Energy source (light, food, carbohydrates, fats, sugars)
• Temperature range (–15o C
to +115o C on Earth)
• Protection (look what
happened to the dinosaurs!)
• Light (or other source of
heat or energy)
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Mercury
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Highly eccentric orbit (used to test GR)
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Rotates 3 times in every 2 years
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Great temperature variations on surface
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-183oC (dark side) – 252oC (sun side)
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Very thin atmosphere
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Low magnetic field
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No water
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Many craters
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Venus
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Brightest object in sky
(except Sun and Moon)
1 day on Venus =
243 days on Earth
Greenhouse effect raises
surface temperature to 464oC
(hotter than Mercury)
Thick carbon dioxide
atmosphere with sulfuric acid
clouds
No surface water, few craters
Lava flows from volcanoes
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Magellan Radar image
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Earth
71% of the surface is covered with liquid water
 Atmosphere of 77% nitrogen, 21% oxygen
 Greenhouse effect from small amount of carbon
dioxide raises the surface temperature to 14oC
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Active surface due to
plate tectonics 
earthquakes and volcanoes
 Mantle and crust mostly
silicon compounds
 Few craters
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Earth’s Moon (Luna)
Lunar Prospector mission
discovered ice at both poles
 No atmosphere
 -153oC to 107oC
 Receives same amount of
sunlight as Earth, has same
chemical makeup
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Mars
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Being explored by Global Surveyor and 2001
Mars Odyssey
Average temperature –63oC
Varied terrain, mountains, canyons and craters
Erosion indicates water used to be present
Similar to Earth chemically
No active volcanoes
Very thin CO2 atmosphere
Little oxygen
Iron and sulfur core
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Mars
Panoramic
view from
Pathfinder
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Permanent
CO2 ice caps
with some
water ice
Weak sunlight
Large dust
storms
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Life on Mars?
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“Face on Mars”
Mars Global
Surveyor Image
April 2001
1976 Viking View
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Life on Mars? Martian Meteorite
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Found in Antarctica in 1984 but origin is Mars
Left Mars 16 million years ago, arrived in Antarctica
13,000 years ago
Evidence of water infiltration while on Mars
Carbonite mineral globules contain shapes that could
be dead, fossilized bacteria and their byproducts
Meteorite
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Carbonate Globules
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Fossilized Shapes
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Meteorites
Most meteorites are chunks of asteroids,
the Moon or Mars; some are from comets
 >50 billion meteorites have traveled
between Earth and Mars since the birth of
the solar system
 Panspermia = Life comes from space
 Some think meteorites could have carried
life from Mars to Earth or vice versa
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meteor
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Jupiter
Giant gas planet: 75% hydrogen, 25% helium
 Four largest moons known since 1610
(Galileo): Io, Europa Ganymede and Callisto
 Spacecraft exploration since 1973, Galileo is
still in orbit around Jupiter
 Liquid metallic hydrogen mantle
 Possible hot, rocky core
 High velocity winds
driven by internal heat
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Jupiter
Great Red Spot is lightning storm, with higher
pressure
 Temperature from –200oC at cloud tops to
thousands of degrees in interior
 Huge magnetic field
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Jupiter’s Moon: Io
Prometheus erupting
• Youngest surface in Solar System
• Many active volcanoes, sulfur
• Temperature –150oC to 1250oC
• No known water
• Sulfur crust
• No atmosphere
Prometheus
volcano
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Jupiter’s Moon: Europa
• Thin outer layer of water ice (1-10 km thick)
• Possible liquid water ocean underneath the surface
•No atmosphere
• Volcanic activity under ocean?
•Sulfur dust from Io’s eruptions on surface
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Jupiter’s Moon: Ganymede
• Rock and water ice on surface
• No atmosphere
• Average noon temperature –121oC on equator
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Jupiter’s Moon: Callisto
• Ice-rock mix throughout
• Possible salt water underneath the surface
•No atmosphere
•Average temperature –108oC on equator
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Saturn
Giant gas planet: 75% hydrogen, 25% helium
 Oblate, flattened appearance, with bright rings
 Three spacecraft visits since 1979, Cassini is on its
way, will arrive in 2004
 Least dense planet, density is less than water
 Hot rocky core, liquid hydrogen
 Bands less visible than
Jupiter; also has spots
 Very thin rings
 Rings mostly water ice
 Strong magnetic field
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Saturn’s moon Titan
Average surface temperature –179oC
 Water icebergs in an ocean of methane?
 95% nitrogen, 5% methane atmosphere
 Pressure about 1.5 times
Earth’s atmosphere
 No water in atmosphere
 Dim sunlight
 Will be visited by Huygens
probe dropped from Cassini
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Uranus
Gas giant, mostly hydrogen atmosphere
 Looks blue due to methane in atmosphere
 Discovered by Herschel in 1781
 Visited by Voyager 2 in 1986
HST image of
 Uranus’ pole points toward Sun
Uranus and its rings
 Rock and ice, only 15% hydrogen
 No rocky core evident
 Clouds and color changes
 11 known rings
 Extremely tilted magnetic field
 20+ moons, 5 are rather large
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Neptune
Discovered in 1846 after being predicted from
perturbations in Uranus’ orbit
 Visited by Voyager 2 in 1989
 Composition similar to Uranus
HST image of
 Internal heat source
Neptune
 Strong winds and storms
 Great dark spot in 1989,
not seen by HST in 1994
 3 Dark rings seen by Voyager 2
 Tilted magnetic field
 8 known moons, Triton is large
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Pluto
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Smallest planet and furthest from Sun (usually)
Smaller than 7 moons in our solar system
Discovered in 1930 by Clyde Tombaugh
Orbit crosses inside Neptune
No spacecraft observations
Pluto and Charon
Is Pluto really a planet?
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YES: It has a moon named Charon
NO: It resembles asteroids
NO: It has an elliptical orbit
Rock and ice, little atmosphere
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Cratering
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Mercury and the Moon show the
results of bombardment during early
formation of solar system
Moon
Mercury
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Earth’s Surface
Q: Why does the Earth’s surface show
little evidence of cratering?
 Bombardment of Earth was similar to
that of the Moon, Venus, Mars and
Mercury
 A: Earth’s surface is actively reforming
due to volcanic activity, erosion from
water, plate tectonics,etc.
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Volcanic Activity
Io Jupiter’s Moon) shows volcanic
activity
 Venus also has lava flows
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Prometheus
volcano on Io
Magellan Radar
image of Venus
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Erosion and Water
Erosion (most likely due to liquid
water) also seems to have affected
Mars, which also has mountains and
craters
 Moon has frozen water at poles but no
signs of erosion
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Mars
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Where is the Water?
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Europa (Jupiter’s Moon)
thin outer layer of water ice
(1-10 km thick)
 possible liquid water ocean
underneath the surface
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 Callisto
(Jupiter’s Moon)
• Ice-rock mix throughout
• Possible salt water
underneath surface
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Where is the Water?
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Saturn
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Rings are mostly water ice
Will be studied by Cassini
in 2004
Titan (Saturn’s Moon)
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Water icebergs in an ocean
of methane?
No water in atmosphere
Huygens probe will be
dropped from Cassini
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Planetary Missions
MESSENGER (MErcury Surface, Space
ENvironment, GEochemistry and Ranging),
being built for launch April 2004, arrives at
Mercury in 2009
 Venus program – no current plans
 Galileo mission is now over. It flew by Io on
1/17/02, and by Amalthea on 11/05/02. It is
due to plunge into the Jovian atmosphere on
September 21, 2003.
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Mars – 5 spacecraft on their way!
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Pathfinder (1996)
Global Surveyor (1999) then two disasters.
Two NASA landers (Spirit and Opportunity)
are on their way to Mars, due to land on
January 4 & 25, 2004.
Europeans: Mars Express orbiter and Beagle
2 lander – due to arrive 12/26/03
Japanese orbiter (launched in 1998) will
arrive at Mars in January 2004.
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Spirit and Opportunity
Entry movie
Launch movie
Exploration
movie
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Planetary Missions
Europa orbiter – approved then eliminated in
FY03 budget. Officially “under study.”
 Cassini mission to Saturn arrives July 2004.
Will drop an ESA probe (Huygens) onto Titan,
and flyby Titan and three smaller moons.
 Pluto/Kuiper Express – Preliminary designs
under consideration. Possible launch in 2006,
to arrive 2015-2017.
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What makes a world habitable?
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In groups of 3-4, take a set of cards that
summarize the properties of various solar
system bodies
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Consider the following:
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Temperature
Water
Atmosphere
Energy
Nutrients
What does life need?
What kinds of conditions might limit life?
Select your top three candidates for life
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Web Resources
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Nine Planets tour
http://www.seds.org/nineplanets/nineplanets
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Martian Meteorite
http://www.lpi.usra.edu/lpi/meteorites/mars_
meteorite.html
 Solar System missions
http://solarsystem.jpl.nasa.gov/missions/
 Schrodinger: http://dieoff.org/page150.htm
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