Fourth International Planetary Dunes Workshop (2015)
8040.pdf
Global Connectivity and Transport within Titan’s Sand Sea Jason W. Barnes, Department of Physics, University of Idaho, Moscow, Idaho, USA (jwbarnes@uidaho.edu)
Meta-Abstract Haiku
height is comparable to that of the atmospheric boundary
layer. Liquid rivers, on the other hand, can stop dunes
Global sand river,
cold by transporting their sediment downstream. I will
dunes like a Möbius strip:
show the rationale behind my suggestions and then exXanadu, the twist.
plore the consequences of this idea for global sediment
sources and sinks. Such an integrated global system also
implies that Titan’s sand seas are geologically old and
that its present atmospheric regime is not of recent construction.
Figure 1: Kuiseb River stopping the dunes, as seen from
the air. Here we show that the longitudinal dunes of the
Namib Sand Sea (visible as red-orange near the horizon
to the south) do not continue past the Kuiseb river despite sand transport in the south-to-north direction. The
dark material is vegetation that lives in the channel bottom even though the river flows only a few tens of days
per year on average. The nearfield desert north of the
riverbed is devoid of sand cover. The Gobabeb Desert
Research Station is visible at the right, near the river.
Abstract
I propose that Titan’s extensive equatorial dune fields
represent a single interconnected sand sea. Individual
sand seas such as Belet and Shangri-La all have connections to their west, from which they import sediment,
and to their east, to which they export sediment. Titan’s
sand may therefore represent an ancient, continuous conveyor belt flowing from west to east. The only break
in the chain is the continent-sized badlands of Xanadu
in the middle of the leading hemisphere. To bypass
Xanadu, dune sands may form fast-moving sub-pixel
barchan chains to the north, eventually arriving in northern Fensal near Menrva. The sharp boundary between
Shangri-La’s dunes and Xanadu at the south end may
be due to fluvial activity. Mountains can detain or divert dunes, but have difficulty stopping them unless their
Fourth International Planetary Dunes Workshop (2015)
8040.pdf
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Figure 2: Global VIMS color mosaic of Titan. We used an empirical atmospheric correction for Titan’s atmospheric
windows at 1.08 µm, 1.28 µm, 1.6 µm, 2 µm, and 2.8 µm, and a single-scattering atmospheric model for 5 µm. The
map uses the best views of each area, but we remove pixels with incidence, emission, or phase angles above 80◦ .
Those removed pixels are grey in the map. The correction works best at longer wavelengths; hence some residual
haze becomes prominent in blue given our color mapping of R=5 µm, G=2 µm, B=1.28 µm. The bright pink areas
represent overcorrections of the 5-µmwindow and are thus artifacts.
30 N
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?
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sand transport
corridors
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transport?
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fluvial
transport?
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area without an obvious source
where does this sand come from?
Figure 3: Notional sand transport map with VIMS R=5 µm, G=2 µm, B=1.3 µm of Titan’s equatorial region in
cylindrical projection. The annotations on the map show that each major sand sea or dune field has sand corridors
from the west from which new sand can arrive and sand corridors to the east for it to exit. Two possible exceptions are
indicated as pink ‘x’s: small dunefields within Adiri and some east of Yalaing Terra. The major obstacle to global sand
transport then is Xanadu, for which we propose two possible mechanisms for the sand to bridge the gap (see text),
fast-moving barchan dunes and fluvial sediment transport in river channels. These particular sand transport corridors
are hypothetical, though consistent with both topography and observed sand transport directions .