Geoscience Reference
In-Depth Information
(a)
(b)
(c)
(d)
(e)
(f)
Figure 5.5
Arid landforms of Mars seen in surface imagery: (a) rock disaggregation, possibly from insolation or salt weathering,
Gusev crater; (b) tessellated megaripples, Endurance Crater, Meridiani Planum; (c) thermal contraction polygons, Vasitas Borealis;
(d) dry particulate flow in sand, Husband Hill, Gusev Crater; (e) multiple aeolian facets on rock in Columbia Hills, Gusev Crater; (f)
incipient honeycomb weathering, Columbia Hills, Gusev Crater.
related to moisture (
Opportunity
, Soderblom
et al.
, 2004)
including those of sulfur, chlorine and bromine (
Spirit
,
Haskin
et al.
, 2005; Crumpler
et al.
, 2005), carbonate
deposition (
Phoenix
, Boynton
et al.
, 2009) and ice segre-
gations (
Phoenix
, Smith
et al.
, 2009). Further studies of
soil profiles and processes on Mars await future surface
missions able to trench or core deeper into the soil and
perform detailed analyses at various depths.
(Thomas, Clarke and Pain, 2005), with abundant evidence
for a role by surface salts (Jagoutz, 2006). The
Phoenix
Lander imaged recent fracturing on the polar zone (Mellon
et al.
, 2009
)
and freezing is probably an important com-
ponent to rock fragmentation even in the martian tropics.
However, much still remains to be understood about the
rock fragmentation processes on Mars, e.g. what process
generated the large quantities of dark basaltic sands (e.g.
at the
Opportunity
site, Soderblom
et al.
, 2004) that form
many of the large dune fields, such as the circumpolar erg
(Warner and Farmer, 2008).
5.5.5.3
Rock breakdown processes
The long-term evolution of surface-hydrosphere interac-
tions (Bibring
et al.
, 2006) has led to a secular change in
rock breakdown processes on Mars (Chevrier and Mathe,
2007). The earliest epochs are characterised by chemi-
cal rock breakdown similar to that experienced in humid
terrestrial environments. As water became less common
the environment was subject to more sulfate-dominated
chemical and physical weathering. In the most recent
time physical processes assisted by moisture-driven pro-
cesses dominate. Surface images of ongoing processes
indicate active rock breakdown by aeolian-driven grains
5.5.5.4
Aeolian landforms
Wind is the most active process currently shaping the mar-
tian surface. Erosion features are visible over a wide range
of scales, including deflation surfaces, leaving pebbly
lags, ventifacts (Bridges
et al.
, 1999, 2007) and yardangs
(Zimbelman and Griffin, 2010). Wind is also responsible
for the stripping of dust mantles (Bridges
et al.
, 2007).
Large-scale denudation through the Amazonian has been
