Dune Worlds - Dune Worlds: How Windblown Sand Shapes Planetary Landscapes - page 113

Part III

Dune Worlds

In this section of the topic, we consider various planetary
bodies in our Solar System in turn, and discuss how they
have been explored, and what has been learned about dunes
on them. The winds and sand transport parameters have
already been discussed in Part II, and thus the character of
transport and the scale of dunes and ripples has been
explained. But the extent of dunes depends on the planetary
history, how sand may have been formed (and/or destroyed)
and how it has been moved around. The resultant coverages
(estimated in an excellent review article by Fenton et al.
2013) are summarized in Table 3.0.1 .
It is striking, given the early discovery of dunes and
blowing sand on Mars, that dunes cover only about 1 % of
the surface of that world—while ubiquitous, dunes are
sparse. In contrast, the Earth has a similar coverage, but
concentrated in a small number of large sand seas. On Titan,
the concentration is even more defined, with one almost

continuous belt of sand seas around the equator, covering a
whopping 12 % or so of the surface (Titan mapping is still
ongoing, so this number may hop up and down by a point or
two). On Venus, dunes—at least at the scale with which we
have observed the surface to date—seem to be an aberrant
exception, associated with particular spots where sand

happens to be available.
In our Solar System, then, Titan wins as the dominant
'Dune World', although in a later Part V, we discuss some
fictional worlds that challenge it (they may challenge reality
too, however—among the thousand-odd extrasolar planets
now discovered, it may be that none approach fictional
Arrakis' dune coverage).
Although dunes are not known on Triton, Io or Pluto, we
review briefly the prospects for aeolian bedforms on these
worlds with tenuous atmospheres.

Table 3.0.1 Planetary dune parameters
Planetary body

Venus Earth Mars Titan

Radius (km) 6052 6370 3396 2575

Surface gravity (m/s 2 ) 8.9 9.8 3.7 1.35

Atmospheric pressure (mbar) 90,000 1000 4-10 1497

Estimated dune field coverage (million km 2 )

0.0183 5 0.9 10

Dune field coverage (%) *0.004 *1 *0.6 *12

Predominant dune types (unknown) Linear, transverse Barchan, transverse Linear