When theCassini-Huygens probe landedon the surface of Saturn's largest moon, Titan,last year, it found no evidence of the ethaneocean long thought to cover the satellite's surface.
Instead,scientists observed dune structures that could be dust-like combinations ofethane and smog particles, according to a new study in the current issue of Nature.
Titan'sdense atmosphere is composed mostly of nitrogen with a small amount of methane.This methane is broken up by the Sun's ultraviolet light to produce a dense orange-brownsmog that hides the satellite's surface.
Scientiststhought that ethane, one of the products of these reactions with the Sun, wasabundant enough to have condensed and rained down to form a kilometer-deepocean across the entire surface of the satellite.
Butobservations of the surface suggest that it is instead covered by dunes, whichDonald Hunten of the University of Arizona thinks could be made of acombination of ethane and smog particles.
Titan'sethane can't condense into liquid rain because "the smog particles grab theethane before it has a chance to form drops," Hunten said.
Theresulting particles deposit on the moon's surface and pile up to form dunesthat might be as deep as several kilometers, Hunten says. The particles wouldbe more like dust than sand though, so Hunten has dubbed them "smust" (acombination of "smog" and "dust").
Huntenbased his proposal for this mechanism on the observed behavior of ethane in Jupiter's atmosphere, where at certainlevels, it condenses onto smog particles.
"Basically,I used Jupiter as the laboratory to show that the ethane is sticking to theparticles," Hunten told Space.com.
"I thinkthere's a very deep deposit of them on the ground [of Titan], but we can'tconfirm that with observations," he added.
To confirmHunten's theory, laboratory experiments would have to be conducted to show thatethane does indeed condense onto the smog particles.
- Cassini Scans Titan for Subsurface Ocean, Methane Ice
- SPACE.com Special Report: Cassini-Huygens at Saturn and Titan
- Researcher Touts Saturn's Titan As New Exploration Goal
- Images: Imagining Saturn and Titan