Resumen: Heat flow calculations based on geological and/or geophysical indicators can help to constrain the thickness,
and potentially the geochemical stratification, of the martian crust. Here we analyze the Warrego
rise region, part of the ancient mountain range referred to as the Thaumasia highlands. This region has
a crustal thickness
much greater than the martian average, as well as estimations of the depth to the brittle–
ductile transition beneath two scarps interpreted to be thrust faults. For the local crustal density
(2900 kg m3) favored by our analysis of the flexural state of compensation of the local topography,
the crustal thickness is at least 70 and 75 km at the scarp locations. However, for one of the scarp locations
our nominal model does not obtain heat flow solutions permitting a homogeneous crust as thick as
required. Our results, therefore, suggest that the crust beneath the Warrego rise region is chemically
stratified with a heat-producing enriched upper layer thinner than the whole crust. Moreover, if the mantle
heat flow (at the time of scarp formation) was higher than 0.3 of the surface heat low, as predicted by
thermal history models, then a stratified crust rise seems unavoidable for this region, even if local heatproducing
element abundances lower than average or hydrostatic pore pressure are considered. This
finding is consistent with a complex geological history, which includes magmatic-driven activity.
Resumen: Claritas rise is a prominent ancient (Noachian) center of tectonism identified through investigation of
comprehensive paleotectonic information of the
western hemisphere of Mars. This center is interpreted to
be the result of magmatic-driven activity, including uplift and associated tectonism, as well as possible
hydrothermal activity. Coupled with its ancient stratigraphy, high density of impact craters, and complex
structure, a possible magnetic signature may indicate that it formed during an ancient period of Mars'
evolution, such as when the dynamo was in operation. As Tharsis lacks magnetic signatures, Claritas rise may
pre-date the development of Tharsis or mark incipient development, since some of the crustal materials
underlying Tharsis and older parts of the magmatic complex, respectively, could have been highly resurfaced,
destroying any remanent magnetism. Here, we detail the significant characteristics of the Claritas rise,
and present a case for why it should be targeted by the Mars Odyssey, Mars Reconnaissance Orbiter, and Mars
Express spacecrafts, as well as be considered as a prime target for future tier-scalable robotic reconnaissance.
Resumen: Mercurian lobate scarp sare interpreted to be the surface expressions of thrust faults formed by
planetary cooling and contraction, which deformed the crust downto the brittle–ductile transition
(BDT) dep that the time of faulting. In this work we have used a for ward modeling procedure
in order to
analyze the relation be tweens carptopography and fault geometrie sand dep thsas sociated with a
group of prominent lobate scarps (Santa Maria Rupes and twoun named scarps) located inthe Kuiper
region of Mercury for which Earth-based radar altimetry is available. Also aback thrust associated with
one of the lobate scarps has been included in this study. We have obtained best fits for depthsof
faul ting between 30 and 39 km; the results are consistent with the previous results for o ther lobate
scarps on Mercury.
The so-derived fault depths have been used to calculate surface heat flows for the time of faulting,
taking into account crustal heat source sand a heterogeneous surface temperature due to the variable
in solation pattern. Deduced surface heat flow sare be tween 19 and 39m Wm-2 for the Kuiper region,
and between 22 and 43 mWm-2 for Discovery Rupes. Both BDT depth sand heat flows are consistent
with the predictions of thermal history models for the range of time relevant for scarp formation.
Resumen: Mercury’s coupled 3:2 spinâ€orbit resonance in conjunction with its relatively high
eccentricity of ∼0.2 and nearâ€zero obliquity results in both a latitudinal and longitudinal
variation in annual average solar insolation and thus equatorial hot and cold regions.
This results in an asymmetric temperature distribution
in the lithosphere and a long
wavelength lateral variation in lithosphere structure and strength that mirrors the insolation
pattern. We employ a thermal evolution model for Mercury generating strength envelopes
of the lithosphere to demonstrate and quantify the possible effects the insolation pattern
has on Mercury’s lithosphere. We find the heterogeneity in lithosphere strength is
substantial and increases with time. We also find that a crust thicker than that of the Moon
or Mars and dry rheologies for the crust and mantle are favorable when compared with
estimates of brittleâ€ductile transition depths derived from lobate scarps. Regions of
stronger and weaker compressive strength imply that the accommodation of radial
contraction of Mercury as its interior cooled, manifest as lobate scarps, may not be
isotropic, imparting a preferential orientation and distribution to the lobate scarps.
Resumen: In this paper, we show that the complex geological evolution of Valles Marineris, Mars, has been highly
influenced by the manifestation
of magmatism (e.g., possible plume activity). This is based on a diversity of
evidence, reported here, for the central part, Melas Chasma, and nearby regions, including uplift, loss of huge
volumes of material, flexure, volcanism, and possible hydrothermal and endogenic-induced outflow channel
activity. Observations include: (1) the identification of a new N50 km-diameter caldera/vent-like feature on
the southwest flank of Melas, which is spatially associated with a previously identified center of tectonic
activity using Viking data; (2) a prominent topographic rise at the central part of Valles Marineris, which
includes Melas Chasma, interpreted to mark an uplift, consistent with faults that are radial and concentric
about it; (3) HiRISE-identified landforms along the floor of the southeast part of Melas Chasma that are
interpreted to reveal a volcanic field; (4) CRISM identification of sulfate-rich outcrops, which could be
indicative of hydrothermal deposits; (5) GRS K/Th signature interpreted as water–magma interactions and/
or variations in rock composition; and (6) geophysical evidence that may indicate partial compensation of
the canyon and/or higher density intrusives beneath it. Long-term magma, tectonic, and water interactions
(Late Noachian into the Amazonian), albeit intermittent, point to an elevated life potential, and thus Valles
Marineris is considered a prime target for future life detection missions.
