TITAN
New Views From Cassini
Public Talk @ University of Maryland Observatory
February 20th 2007
Dr Conor A Nixon
University of Maryland Astronomy Department & NASA Goddard Space Flight Center
The Giant Moon
• Titan
was the sixth moon ever
to be discovered, in 1655 by
Dutch astronomer Christian
Huygens.
• Named due to its massive size, Titan was
originally thought to be the solar system’s
largest moon.
• Through a large telescope, Titan appears
as a fuzzy pale orange ball. Even Voyager
1 saw little detail - our best image prior to
Cassini!
Earth vs Titan Atmospheres
Why Titan?
• Titan is the only moon in the solar system
with a substantial atmosphere.
• Titan may resemble the Earth’s atmosphere
from long ago, in the deep freeze, with
prebiotic chemistry.
• Titan is (was) the largest un-mapped piece of
real estate in the solar system.
Astrobiology on Titan?
The
Cassini
Mission
Ready to go…
• Cassini on display before
launch, fall 1997
• Cassini at launch pad, on
rocket, awaiting fairing.
Blast-off!
• Cassini-Huygens was launched at 4:43 a.m. EDT on October 15th 1997
from Cape Canaveral Air Force Station
Cassini takes the scenic
route to Saturn…
Going Into Orbit!
A Grand Design
• Having
finally reached
Saturn orbit,
Cassini is now
2/3 way
through its
prime 4-year
mission (39 of
76 orbits),
including 45
close Titan
encounters.
Cassini’s Eyes
• Cassini can see more than just visible light…
• ULTRAVIOLET rays shorter than visible light.
• INFRARED waves longer than visible light.
• MICROWAVE and RADIO waves (including RADAR).
Peeling the Onion Titan’s Hazes and Clouds
From a
distance…
• Cassini’s first Titan
fly-by on July 2nd
2004 was quite
distant, but already
showed amazing
new details of the
‘veiled world’.
• This UV filter
image has been
falsely colored to
show detail.
Purple
haze
• This false
color UV
night-side
image from
December
2004 shows
the many
haze layers
as revealed
by scattered
sunlight.
Obscured
by clouds
• This colorcomposite image
from the Cassini
VIMS instrument
shows clouds
spreading out
along the 40°S
latitude circle.
• Taken in July
2006 at a distance
of 160,000 km.
A polar vortex
• This
is an infrared color composite
from VIMS from Feb 1 2007, showing a
giant cloud system over the North Pole.
Seeing the
Surface
Full Moon
• Cassini’s cameras
were designed to see
the surface using
selected colors of
infrared light which can
penetrate the haze.
• This is a composite
image: Red and green
show methane: north
hemisphere is redder.
• Blue shows UV: high
atmosphere and
detached hazes.
Bright Highlands, Dark Plains
Radar
Mapping
•Here is the same
RADAR image twice,
but the top one has
been falsely colored to
aid interpretation: pink
shows ‘rougher’
terrain, green is
‘smoother’.
• Size: 300x150 km.
• Notice the river deltalike ‘fans’.
‘Cat-scratches’
• Other RADAR swathes showed dramatically different
terrain.
• These linear markings have been dubbed ‘catscratches’, and appear to be wind-blown dunes (the wind
blows mainly from West to East, or left to right).
A river runs through it…
• Cassini’s RADAR has also shown meandering rivers cutting across
the bright ‘continent’ Xanadu on Titan’s leading hemisphere.
Impacts
and
Volcanoes
‘Circus Maximus’
• RADAR also confirmed that a ring-like feature seen
by Cassini’s cameras was a huge, 440 km impact basin now called Menrva.
Titan Cryovolcano?
• Cassini VIMS saw this evidence of a possible
volcano, with two outflowing ‘arms’.
Xanadu Smile
• The VIMS instrument saw this bright spot coinciding with the
Xanadu ‘smile’. This could be an impact crater or volcano.
A violent past…
• This image was
created from two flybys in October 2006.
• The circular feature is
probably the remnant
of a long-ago giant
impact.
• This may also have
caused the folded
mountains to the SE
and the dark rift to the
NW.
Lakes
Land O
lakes?
• This image of the
south pole shows
white clouds and an
intriguing dark
feature with a sharp
boundary.
• This could be a lake
of hydrocarbons, or
just a depression
filled with solid
condensed smog.
Liquid lakes
on Titan
• This image was made by
Cassini’s RADAR, so the
colors are not real.
• Regions tinted in blue
show a low radar
reflection, and must be
smooth and/or absorbing
of radio waves.
• Tan areas are ‘brighter’
in radar reflection, and are
probably rougher.
Titan’s ‘Kissing Lakes’
Up close and personal Huygens Lands on Titan
Destination Titan!
• Huygens
entered
Titan’s
atmosphere at
5:13 am ET on
January 14th
2004.
• The entry angle
was 65 degrees,
with Huygens
moving at 6 km/s.
Mission Timeline
River to the shore?
• This composite of
three images shows
what looks like a
branching river
draining to a
shoreline.
• Rainfall on Titan
would presumably
be liquid methane.
Titan ‘boulders’
• Huygens bumped
rather than splashed on
Titan’s surface.
• This image shows the
ground near the
spacecraft.
• The ‘boulders’ are
probably water ice.
• The below-center
‘boulder’ is actually just
a pebble, 6 in across.
What have we learned?
• Titan
has a methanological cycle which parallels the
Earth’s hydrological cycle: evaporation, clouds, rain,
lakes, rivers.
• Titan is replenishing its methane from somewhere:
most likely via volcanic eruptions from inside.
• Titan is less covered in liquids than we thought:
instead, we see dune fields near the equator of solid
organic residue.
THE END…
… FOR NOW!