TITAN New Views From Cassini Public 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 color- composite 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 , 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 delta- like ‘fans’.

‘Cat-scratches’ Other RADAR swathes showed dramatically different terrain. These linear markings have been dubbed ‘cat- scratches’, 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 fly- bys in October 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 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!