Transcript MYSTERIOUS TITAN - University of Chicago

SATURN’S MYSTERIOUS
MOON TITAN
Why are Saturn and Titan
Important
• Saturn is a miniature Solar System
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Titan is Similar to Young(?) Earth
• Atmosphere
– 1.5xas thick as
earth’s
– Mostly
nitrogen, like
earth
– 6% methane
plus other
hydrocarbons
33 Moons Known around Saturn
But, Titan earns it’s name
• Titan is the largest of Saturn's moons, and is the second
largest moon in the solar system. Titan is a complex world
more similar to Earth, Mars or Venus than it is to outer planets
Cassini Mission Arrived Last
Summer
Saturn Up Close
Rings
Titan Observations- through time
Recent…
Not so long ago…
Long ago…
Recent…
Latest Views from Close
Encounter Yesterday
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Titan
First Shots from Latest Encounter
Titan Lander (Cassini) January 14
Much More Exploration at Saturn
• Four more
years of
study
• 76 orbits of
Saturn
• 45 more
encounters
with Titan
TOST Summary
• 46 Titan flybys
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Scattered throughout the tour but 2006 and 2007 are the heaviest
T0 July 1 2004 (350,000 km) flyby - hours after SOI
TA Oct of 2004 - first RADAR SAR image, Huygens Landing site imaging
TB Dec of 2004 - ORS flyby
Huygens mission Jan 2005
• Mainly ORS observations during the inbound and outbound time wings
– Closest approach varies between RADAR observations of the surface, ORS
observations of the surface, limb, or upper atmosphere, Radio Science occultations
and bi-static observations, or INMS in-situ observations of the atmosphere.
• Pushing the spacecraft
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Over half of the Titan flybys are on thrusters (hydrazine usage is an issue)
Power modes during Radio Science experiments usually unique
Attitude profile during a Titan flyby is ambitious
Always fill both SSRs!
• 4 broad science themes:
– Interior Structure
– Surface Characterization
– Atmospheric Properties
– Magnetospheric Interactions
Atmosphere de Titan
4 Broad Science Themes
• Interior Structure
– Mass was determined by Voyager. We assume Titan has differentiated into core,
mantel and crust, but what are the dimensions of each?
• Gravity Field experiments by Radio Science
– Does Titan have its own internal magnetic field?
• Surface Characterization
– Surfaces of solid bodies in the solar system are altered primarily by three processes:
impact cratering, volcanism, and tectonics. Erosion may also play a role on bodies
with atmospheres.
– Like other moons in the outer solar system, Titan is expected to have a
predominantly water ice crust. Water at the temperatures in the outer solar system
is as solid and strong as rock.
– Liquids on Titan’s surface:
• Hydrocarbons in Titan's atmosphere pass some amount of time as the aerosol haze
obscuring the surface, gradually drifting to the surface.
• Theoretically, they should accumulate on the surface, and, over the life of the solar
system, would produce a global ocean of ethane, acetylene, propane, etc., with an
average depth of up to 1 km. THIS IS AN IRREVERSIBLE PROCESS and the current
quantity of CH4 in Titan's atmosphere, if it isn't re-supplied will be used up in 10 million
years.
• Recent earth-based results suggest that there are local regions of liquids
– RADAR and the orbiter imagers will observe the surface through wavelength
“windows”
4 Broad Science Themes
• Atmospheric Properties
– Titan’s smoggy atmosphere: dominant atmospheric constituent is nitrogen (N2),
Methane (CH4) represents (very) roughly 6%. Surface pressure is 1.5 bars, 50%
greater than that of Earth, in spite of Titan's smaller size, and the opacity of Titan's
atmosphere is caused by photochemical smog
– What is the source of the nitrogen in Titan’s atmosphere?
– How is methane supplied to Titan’s atmosphere?
– The orbiter’s spectrometers will detect chemical species, look for absorption
features in spectra acquired from stellar and solar occultations.
– The orbiter imagers will study circulation by tracking clouds. Temperature profiles
and thermal maps influence Titan’s weather.
– Composition of ions and neutrals very high measured in-situe by INMS
• Magnetospheric Interactions
– Titan orbits Saturn at a distance of ~ 20.25 Saturn radii.
– This puts Titan in the magnetosphere of Saturn most of the time, but occasionally
outside in the solar wind.
– When Titan is in Saturn's magnetosphere it affects the configuration of the
magnetosphere:
– Saturn's magnetic field lines were observed to "drape" around Titan.
– The "plasma" (energetic charged particles) flowing into and around Titan produces
a wake similar to that of a boat speeding through water.
TA - October 26, 2004
• Closest approach is 1200km (altitude) on 2004300T15:30:21 (Spacecraft Event Time, UTC) on
thrusters
• Inbound illumination is lit, closest appoach to Saturn
(periapsis) follows 2 days later
• TA Data received on Earth between 6:30pm and 3:30am
on October 26th. 3445 Mbits Total
• Science Highlights:
– First SAR (Synthetic Aperature RADAR) imaging of Titan’s
surface.
– Sample the upper fringes of Titan’s atmosphere with INMS
– First very close orbiter imaging including Huygens landing
site. Very low phase angle (15-36 degrees)
– Inbound and outbound atmospheric investigations to support
atmospheric modeling of Titan’s atmosphere for Huygens
Mission
SUMMARY
THE EXPLORATION OF TITAN IS AT THE VERY HEART OF
THE CASSINI / HUYGENS PLANETARY MISSION.
TITAN IS THE SOLE FOCUS OF THE HUYGENS PROBE
AND ONE OF THE MAIN TARGETS OF THE CASSINI
ORBITER.
By combining the results from the Cassini mission with Earthbased astronomical observations, laboratory experiments and
computer modeling, scientists hope to answer basic questions
regarding the origin and evolution of Titan's atmosphere, the nature
of the surface, and the structure of its interior.