Titan Is Ideal Lab for Oceanography, Meteorology

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Titan Is Ideal Lab for Oceanography, Meteorology
By Lori Stiles
University of Arizona
February 14, 2004

After a 7-year interplanetary voyage, NASA's Cassini spacecraft
will reach Saturn this July and begin what promises to be one of
the most exciting missions in planetary exploration history.

After years of work, scientists have just completed plans for
Cassini's observations of Saturn's largest moon, Titan.

"Of course, no battle plan survives contact with the enemy," said
Ralph Lorenz, an assistant research scientist at the University of
Arizona's Lunar and Planetary Laboratory in Tucson.

The spacecraft will deploy the European Space Agency's Huygens
probe to Titan for a January 2005 landing. Nearly half the size of
Earth, frigid Titan is the only moon in the solar system with a thick
atmosphere. Smog has prevented scientists from getting more
than a tantalizing hint of what may be on the moon's amazing
surface.

"Titan is a completely new world to us, and what we learn early on
will likely make us want to adjust our plans. But we have 44 flybys
of Titan in only four years, so we have to have a basic plan to work
to."

Scientists have long thought that, given the abundant methane in
Titan's atmosphere, there might be liquid hydrocarbons on Titan.
Infrared maps taken by the Hubble Space Telescope and
ground-based telescopes show bright and dark regions on Titan's
surface. The maps indicate the dark regions are literally
pitch-black, suggesting liquid ethane and methane.

Last year, data from the Arecibo telescope showed there are many
regions on Titan that are both fairly radar-dark and very smooth.
One explanation is that these areas are seas of methane and
ethane. These two compounds, present in natural gas on Earth, are
liquid at Titan's frigid surface temperature, 94 degrees Kelvin
(minus 179 degrees Celsius).

Titan will be an outstanding laboratory for oceanography and
meteorology, Lorenz predicts.

"Many important oceanographical processes, like the transport of
heat from low to high latitudes by ocean currents, or the generation
of waves by wind, are known only empirically on Earth," Lorenz said.
"If you want to know how big waves get for a given windspeed, you
just go out and measure both of them, get a lot of datapoints, and
fit a line through them.

"But that's not the same as understanding the underlying physics and
being able to predict how things will be different if circumstances
change. By giving us a whole new set of parameters, Titan will really
open our understanding of how oceans and climates work."

Cassini/Huygens will answer many questions, among them:

Are the winds strong enough to whip up waves that will cut
cliffs in the lakesides? Will they form steep beaches, or will the
strong tides caused by Saturn's gravity be a bigger effect,
forming wide, shallow tidal flats?

How deep are Titan's seas? This question bears on the history
of Titan's atmosphere, which is the only other significant
nitrogen atmosphere in the solar system, apart from the one
you're breathing now.

And do the oceans have the same composition everywhere?
Just as there are salty seas and freshwater lakes on Earth,
some seas on Titan may be more ethane-rich than others.

Lorenz is a member of both the Cassini spacecraft's radar
mapping team and a co-investigator of the Surface Science
Package on the Huygens probe. He is talking today (Saturday,
Feb. 14) at the press conference, "What Will Titan Be Like?"
at the American Association for the Advancement of Science
meeting in Seattle.

Lorenz began working on the Huygens project as an engineer
for the European Space Agency in 1990, then earned his
doctorate from the University of Kent at Canterbury, England,
while building one of the probe's experiments. He joined the
University of Arizona in 1994 where he started work on Cassini's
Radar investigation. He is a co-author of the book, "Lifting
Titan's Veil" published in 2002 by Cambridge University
Press.