First Images from the Mars Reconnaisance Orbiter (MRO)

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First Images from the Mars Reconnaisance Orbiter
(MRO)
Reached Mars on March 10 Now turning elliptical
orbit into a more circular orbit. First test
images. Craters (fresh/old?) Gullies Dunes Begin
s collecting data in November. 720 million
mission.
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ESA Venus Express Went into Orbit
260 million mission.
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25th Anniversary of the First Shuttle Launch

• Reflection in the news media over the Crew
• Exploration Vehicle.
• lack of funds to accomplish
• costs over 1/5 of NASAs budget
• requires significant transformation in NASA

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Lecture 32. Titan and its Atmosphere.
reading Chapter 8
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Titan
Earth 12,700 km Mars 6,800 km Ganymede5262
km Moon 3476 km
Largest Moon of Saturn - 5150 km. Discovered by
Christiaan Huygens in 1655. Voyager 1 flyby in
1980. In 2004, Cassini orbiter made close
observations. Jan 2005, Huygens probe landed on
the surface. Composition 50 water ice and 50
rock Similar composition as Ganymede
Callisto. Density of water 1.0
g/cm3 Titan/Callisto 1.9 g/cm3 Earth 5.5
g/cm3 May have a rocky core and a mantle of
ice. Rotates every 16 days, is in synchronous
rotation. Voyager found southern hemisphere to
be brighter, are seasonal differences in
brightness.
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Titans Atmosphere
Unique that it has a dense atmosphere of 1.6 bars
and is mostly N2. 77-85 N2, 12-17 argon, 3-6
methane, 0.2 H2 Trace amounts of organic
compounds ethane, propane, hydrogen cyanide,
CO2, CO, acetylene Organic compounds when
methane undergoes photochemical reactions from
the faint sunlight. Produces a thick smog, hazy
atmosphere. Haze layer is 300 km above the
surface. There are distinct layers in the
haze. Titans orbit is sometimes outside of
Saturns magnetosphere. Solar wind particles may
ionize the atmosphere and cause some of the
photochemical reactions in the atmosphere. Thick
atmosphere obscures the surface in visible light.
false-color Voyager 1 image of haze layers
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Voyager Observations

• Atmosphere structure and dynamics determined by 2
  instruments
• radio occultation
• How radio waves are scattered and bent as they
  pass through
• the atmosphere determine the T and density of the
  atmosphere
• infrared spectroscopy
• Different compounds absorb heat energy at
  different
• wavelengths and vibrate. Measure how heat energy
• from sunlight is absorbed (produces peaks and
  valleys in the spectrum).
• Each compound has particular
• fingerprint.

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Voyager Observations, cont.
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Voyager Observations, cont.
large number of hydrocarbons and N-containing
compounds
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Titans Surface
Surface temperature -179C Cold enough that
methane (CH4) could be liquid. Cold enough that
ethane (CH3CH3) could also be liquid. Thought
there could be seas of liquid methane and
ethane. .
Freezing T Boiling T H2O 0C 100C NH3 -78C -3
3C CH4 -182C -164C CH3CH3 -183C -89C at
-179C, CH4 is solid/liquid/gas? at -179C,
CH3CH3 is solid/liquid/gas?
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Titans Surface
So, if it is cold enough to liquify methane and
ethane, why is there lots of methane in the
atmosphere?? Could be places where it is
slightly warmer than -164C where liquid methane
can turn into gas, once in the atmosphere cooling
would produce clouds and then methane rain.
If there are regions where the surface is
lt-183C (cools 4C) you could have frozen
mountains of methane and ethane ice! Why is
Titan so cold?? at 9.6AU, sunlight is 100x weaker
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Titans Surface
Hubble Space Telescope images Peered through the
clouds using infrared light. Observed dark and
light regions on the surface. Couldnt really
figure out what they were due to. Methane/ethane
Seas? Bright volcanic regions?
If Titan does have liquid seas, they should
experience tides just like the Earth as it
revolves around Saturn!
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Clouds
Scattered clouds. Composed of methane, ethane, or
simple organic compounds. More complex organic
compounds create the orange color. Clouds change
hourly, presumably deposit methane rain onto the
surface.
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Tholins
Polymer formed from uv irradiation of CH4 or
CH3CH3. Abundant on icy bodies in the solar
system. Coined by Carl Sagan to describe
unknown organic substances obtained in
Miller-Urey-type experiments using gas mixtures
found in Titans atmosphere. Produce a thick
orange goo. When dissolved, they produce amino
acids with both handedness. Polymers of C, H,
and N. Over 75 different compounds in it. PAH
family benzene (1 ring), 2-4 rings cyclic
compounds with C and N includes bases found in
nucleic acids
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How are Tholins Produced?
UV light causes reactions to occur high in the
atmosphere (photochemical reactions) Solid
particles - Tholins - likely rain down to
the surface. Speculation could be km-deep
deposits of tholins on the surface.
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Titan as a Model for Early Earth
Methane-rich, N2-rich atmosphere, lack of
oxygen. An early methane greenhouse helps solve
Earths Faint Young Sun Problem. Photochemical
reactions producing organic compounds. Some think
there could have been similar hazes on early
Earth. Hydrogen cyanide in the atmosphere - is a
prebiotic compound in the abiotic synthesis of
amino acids. Titan is soooo cold - chemical
reactions proceed very sloooowly. So fewer number
of organic compounds are produced. At -179C a
chemical reaction will be 1042 times slower than
at room temperature!
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Life on Titan?
Do you have the 5 thing needed to have life?
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Properties of Water that are Important for Life
It is the universal solvent because it can
dissolve the most substances than any other
liquid. Electrical charge differential helps it
dissolve ions, like sodium chloride. Water
molecules are attracted to each other - creates
surface tension Water forms drops, capillary
action allows water to be sucked up plant roots
and blood vessels Water is a polar compound. Ions
are needed for life!
Water can also dissolve uncharged
organic compounds, like sugars. It is found in
all three states solid, liquid, gas on the Earth
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Methane and Ethane Liquids
Are hydrocarbons - so have a greasy nature. Are
non-polar compounds so they -dont dissolve
ions. -dont have much surface tension.
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Lecture 33. Cassini-Huygens Mission.
reading Chapter 8