Planetary science: New views of Titan

When the Huygens probe landed on Titan, it provided the first direct measurements from Saturn's giant moon. Seven papers in Nature this week describe a world that resembles a primitive Earth, complete with weather systems and geological activity.

[1] - [7] Planetary science: New views of Titan (AOP)

DOI: 10.1038/nature04349
DOI: 10.1038/nature04122
DOI: 10.1038/nature04314
DOI: 10.1038/nature04060
DOI: 10.1038/nature04126
DOI: 10.1038/nature04211
DOI: 10.1038/nature04347

***These papers will be published electronically on Nature's website on 30
November at 1500 London time / 1000 US Eastern time (which is also when the
embargo lifts) as part of our AOP (ahead of print) programme. Although we
have included them on this release to avoid multiple mailings they will not
appear in print on 1 December, but at a later date.***

When the Huygens probe landed on Titan, it provided the first direct
measurements from the atmosphere and surface of Saturn's giant moon. Seven
papers published online this week by Nature describe a world that resembles
a primitive Earth, complete with weather systems and geological activity.
Guy Israël and colleagues report that the aerosols that make up Titan's
clouds have solid cores made from complex organic molecules containing
carbon and nitrogen. These compounds are made in the photochemical smog of
the moon's methane-rich atmosphere, and are eventually carried to its
surface by rain and atmospheric circulation.

By measuring the abundances of isotopes of argon, nitrogen and carbon atoms
in the atmosphere's gases, Hasso Niemann and colleagues conclude that there
is no reason to suspect that Titan's methane comes from biological activity.
However it is being continually replenished, possibly being freed from a
large carbon store inside the moon by geological activity. They also suggest
that nitrogen in the atmosphere was originally delivered by icy
planetesimals carrying ammonia, which was eventually broken down into
nitrogen, as seems to have happened on Earth.

Francesca Ferri and colleagues unveil precise measurements of the
temperature and pressure of Titan from the top of its atmosphere right down
to the surface, which is a chilly minus 179 degrees Celsius. They find that
the atmosphere is divided into quite distinct layers, and even saw evidence
for lightning.

Michael Bird and colleagues found that on average Titan's winds blow in the
same direction as the moon rotates, and that close to the surface these
winds are very weak, travelling at around walking speed.

Marty Tomasko and colleagues describe the dry riverbed and drainage channels
seen during Huygens' descent, evidence that liquid methane falls as rain or
erupts from cryovolcanoes, periodically flooding the surface. Huygens'
landing site is strewn with what appear to be rocks and pebbles, but not
humid enough with methane vapour to cause ground fogs.

John Zarnecki and colleagues found that the Huygens probe landed on a
relatively smooth surface of icy grains with the consistency of wet clay or
sand, which threw up a plume of methane when the warm probe touched down.
Finally, Olivier Witasse and colleagues provide an overview of the descent
and landing of the probe. "Titan will still have much to tell us, even after
analysis of the rich harvest of the Huygens data," comments Tobias Owen in a
related News and Views article.

CONTACTS
Guy Israel (UMR CNRS, Verrières le Buisson, France) Paper [1]
Tel: +33 1 64 47 4394; E-mail: [email protected]

Hasso Niemann (NASA Goddard Space Flight Center, Greenbelt, MD, USA) Paper [2]
Tel: +1 301 614 6381; E-mail: hasso.b.niemann@nasa

Francesca Ferri (University of Padova, Italy) Paper [3]
Tel: +39 498 276 798; E-mail: [email protected]

Michael Bird (Universitaet Bonn, Germany) Paper [4]
Tel: +49 228 733 651; E-mail: [email protected]

Martin M.G.T. Tomasko (University of Arizona-Tucson, AZ, USA) Paper [5]
Tel: +1 520 621 6969; E-mail: [email protected]

John Zarnecki (The Open University, Milton Keynes, UK) Paper [6]
Tel: +44 1908 659 599; E-mail: [email protected]

Olivier Witasse (ESA, Noordwijk, Netherlands) Paper [7]
Tel: +31 71 565 80 15; E-mail: [email protected]

Tobias Owen (University of Hawaii at Manoa, Honolulu, HI, USA) News and Views author
Tel: +1 808 956 8007/8312/7399; E-mail: [email protected]

Please note: ESA are hosting a press conference on these papers. This will
take place UNDER EMBARGO on Wednesday 30 November.

Contacts for journalists wishing to have any information are:
Mr. Franco Bonacina, Head of ESA Media Relations Office:
Tel: +39 1 5369 7713; E-mail: [email protected]

Mrs. Jocelyne Landeau, Science Missions Communication Coordinator:
Tel: +49 61 51 90 2696; E-mail: [email protected]

Published: 30 Nov 2005

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