title: A soft solid surface on Titan as revealed by the Huygens Surface Science Package.
abstract: The surface of Saturn's largest satellite--Titan--is largely obscured by an optically thick atmospheric haze, and so its nature has been the subject of considerable speculation and discussion. The Huygens probe entered Titan's atmosphere on 14 January 2005 and descended to the surface using a parachute system. Here we report measurements made just above and on the surface of Titan by the Huygens Surface Science Package. Acoustic sounding over the last 90 m above the surface reveals a relatively smooth, but not completely flat, surface surrounding the landing site. Penetrometry and accelerometry measurements during the probe impact event reveal that the surface was neither hard (like solid ice) nor very compressible (like a blanket of fluffy aerosol); rather, the Huygens probe landed on a relatively soft solid surface whose properties are analogous to wet clay, lightly packed snow and wet or dry sand. The probe settled gradually by a few millimetres after landing.
authors.affiliation: The Open University, Walton Hall, Milton Keynes MK7 6AA, UK. J.C.Zarnecki@open.ac.uk
authors.forename: John C
authors.initials: JC
authors.lastname: Zarnecki
authors.forename: Mark R
authors.initials: MR
authors.lastname: Leese
authors.forename: Brijen
authors.initials: B
authors.lastname: Hathi
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Ball
authors.forename: Axel
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authors.lastname: Hagermann
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authors.lastname: Towner
authors.forename: Ralph D
authors.initials: RD
authors.lastname: Lorenz
authors.forename: J Anthony M
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authors.lastname: McDonnell
authors.forename: Simon F
authors.initials: SF
authors.lastname: Green
authors.forename: Manish R
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authors.forename: Timothy J
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authors.lastname: Ringrose
authors.forename: Philip D
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authors.lastname: Rosenberg
authors.forename: Karl R
authors.initials: KR
authors.lastname: Atkinson
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authors.initials: MD
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authors.lastname: Banaszkiewicz
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authors.forename: Francesca
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authors.lastname: Ferri
authors.forename: Marcello
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authors.lastname: Fulchignoni
authors.forename: Nadeem A L
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authors.lastname: Ghafoor
authors.forename: Günter
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authors.lastname: Kargl
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authors.lastname: Svedhem
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authors.lastname: Delderfield
authors.forename: Manuel
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authors.lastname: Grande
authors.forename: David J
authors.initials: DJ
authors.lastname: Parker
authors.forename: Peter G
authors.initials: PG
authors.lastname: Challenor
authors.forename: John E
authors.initials: JE
authors.lastname: Geake