 |
| Titel |
A comparative study of Interior Layered Deposits on Mars |
| VerfasserIn |
M. Sowe, L. H. Roach, E. Hauber, R. Jaumann  , J. F. Mustard, G. Neukum |
| Konferenz |
EGU General Assembly 2009
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250026719
|
|
|
|
|
|
| Zusammenfassung |
| Using information from high-resolution image (MOC, HiRISE), elevation (HRSC DTMs)
and spectral data (TES, THEMIS, OMEGA, CRISM) a comparative study of Interior Layered
Deposits (ILDs) located in the eastern Valles Marineris and their adjacent chaotic regions is
performed in order to ascertain possible correlations between ILDs. ILDs have been reported
from several regions around Valles Marineris that are in strong association with chaotic
regions, hydrated minerals and haematite.
This study shows that ILDs partly vary in terms of erosional shape, thickness, elevation,
material competence and possibly mineralogy, but that their morphologies are mostly
comparable. Two different types of morphology were ascertained on their tops, these in turn
apparently correlate with their mineralogical properties.
The majority of ILDs that exhibit a protective but spectrally neutral cap rock (showing
surface vugs, monadnocks, sharp crests) on their top are the ones that coevally exhibit
hydrated sulphates in their lower unit, whereas the ones that show a heavily fluted and
grooved top tend to be spectrally neutral on the whole. At the time, the two types differ in
their albedo as well as in their state of weathering and erosion. However, there is no
correlation with elevation, thickness, or competence that could reinforce the above
correlation.
Stair-stepped morphologies observed suggest alternating strata of competent and less
competent material. Thickly bedded lower units and thinly layered upper units can be
observed. Moreover, the ILD material is highly consolidated, which is confirmed by
meter-sized boulders and talus produced by steep scarps, which is visible on HiRISE images.
Different hydration states of sulphates (mono- and polyhydrated) are present here and have
been found on ILDs in the western Valles Marineris as well. Thus, post-formational humidity
changes may be responsible for volume changes resulting in angular joints and rock
fragmentation into boulders. Convoluted-like bedding on the cap rock may also confirm this
observation as they indicate dehydration. Hydrated sulphates demonstrate sufficient water or
humidity was present up to a certain elevation suggesting a warmer, more humid
Mars and acidic conditions that potentially existed in the Hesperian. The maximum
elevation of hydrated sulphates corresponds to Ganges Mensa (-500Â m) for the
chasmata and Iani Chaos ILDs (-3000Â m) for the eastern chaotic terrains. This
in turn indicates ILDs are in parts sulphate bearing up to the top, so the original
uppermost elevation that experienced hydration could be higher than measured. |
|
|
|
|
|
|