Titan's topography, strange.... |
Titan's topography, strange.... |
Apr 12 2009, 12:44 PM
Post
#1
|
|
Senior Member Group: Moderator Posts: 2785 Joined: 10-November 06 From: Pasadena, CA Member No.: 1345 |
Recent article in Science by Zebker et al.:
Zebker et al. Science in press, "Size and Shape of Saturn's Moon Titan". doi: 10.1126/science.1168905 (published online April 2, 2009) Link to abstract (pay-for article): http://www.sciencemag.org/cgi/content/abstract/1168905 Article on spaceref discusses this paper: http://www.spaceref.com/news/viewpr.html?pid=27912 Figure 3 from the Science article is a global elevation map relative to barycenter. Key points of article:
"Xanadu seems to be systematically lower than other parts of the equatorial belt, and not uplifted like most mountainous areas on Earth." (quote from Fig. 3 caption in article) -Mike -------------------- Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
|
|
|
Apr 12 2009, 08:24 PM
Post
#2
|
|
Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
Thanks for starting off a discussion on this. One fairly safe conclusion would seem to be that for Titan a triaxial ellipsoid is a very poor fit to an equipotential. The latter must be very bumpy compared with what we're used to. But as you say there are problems everywhere with this (which likely means that it will be a very productive observation in the long run). Are Xanadu's mountains dense, or light and porous? We have observational evidence for the latter, yet here it is suggested that they are denser than surrounding terrain and thus capable of making their own basin to sit in.
A general observation (not necessarily helpful): topsy-turvy topography is less difficult to explain away if ALL the surface materials (except the liquids) are of very low density, i.e. fluffy or aerated. |
|
|
Apr 15 2009, 03:39 AM
Post
#3
|
|
Member Group: Members Posts: 613 Joined: 23-February 07 From: Occasionally in Columbia, MD Member No.: 1764 |
Thanks for starting off a discussion on this. One fairly safe conclusion would seem to be that for Titan a triaxial ellipsoid is a very poor fit to an equipotential. ... A general observation (not necessarily helpful): topsy-turvy topography is less difficult to explain away if ALL the surface materials (except the liquids) are of very low density, i.e. fluffy or aerated. For your first remark, we'll need to wait to see what the published gravity field is. If the 3rd order terms are, in fact low (at one time the retrievals suggested they might not be), then in fact a triaxial ellipsoid IS a good fit to the EQUIPOTENTIAL. Maybe (since you are referring to the shape measured from radar) you mean that a triaxial ellipsoid isnt a good fit to the figure ? As far as liquids draining downhill goes, there does seem to be a consistency between lakes at high latitudes, and the hint of a tendency (with incomplete sampling) in my fluvial paper for rivers to flow poleward, and the difference between the topographic shape and reasonable geopotentials. The low-latitude longitudinal contrasts (viz, low Xanadu vs the dunes) is harder to explain, as is the orientation of the dunes themselves. I sometimes wonder about albedo-driven wind (i.e. sea-breeze type circulations - with effectively katabatic flow away from high albedo regions). The Zebker et al (you can call me al !) paper about the shape - like the Lorenz et al spin paper last year - is I think just going to be the start of a long and complicated story. |
|
|
Lo-Fi Version | Time is now: 26th September 2024 - 06:31 AM |
RULES AND GUIDELINES Please read the Forum Rules and Guidelines before posting. IMAGE COPYRIGHT |
OPINIONS AND MODERATION Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators. |
SUPPORT THE FORUM Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member. |