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José Miguel Pasini: Mars references
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VR1.0
PT J
AU Burr, DM
Carling, PA
Beyer, RA
Lancaster, N
TI Flood-formed dunes in Athabasca Valles, Mars: morphology, modeling, and implications
SO ICARUS
AB Estimates of discharge for martian outflow channels have spanned orders of magnitude due in part to uncertainties in floodwater height. A methodology of estimating discharge based on bedforms would reduce some of this uncertainty. Such a methodology based on the morphology and granulometry of flood-formed ('diluvial') dunes has been developed by Carling (1996b, in: Branson, J., Brown, A.G., Gregory, K.J. (Eds.), Global Continental Changes: The Context of Palaeohydrology. Geological Society Special Publication No. 115, London, UK, 165-179) and applied to Pleistocene flood-formed dunes in Siberia. Transverse periodic dune-like bedforms in Athabasca Valles, Mars, have previously been classified both as flood-formed dunes and as antidunes. Either interpretation is important, as they both imply substantial quantities of water, but each has different hydraulic implications. We undertook photoclinometric measurements of these forms, and compared them with data from flood-formed dunes in Siberia. Our analysis of those data shows their morphology to be more consistent with dunes than antidunes, thus providing the first documentation of flood-formed dunes on Mars. Other reasoning based on context and likely hydraulics also supports the bedforms' classification as dunes. Evidence does not support the dunes being aeolian, although a conclusive determination cannot be made with present data. Given the preponderance of evidence that the features are flood-formed instead of aeolian, we applied Carling's (1996b, in: Branson, J., Brown, A.G., Gregory, K.J. (Eds.), Global Continental Changes: The Context of Palaeohydrology. Geological Society Special Publication No. 115, London, UK, 165-179) dune-flow model to derive the peak discharge of the flood flow that formed them. The resultant estimate is approximately 2 x 10(6) m(3)/s, similar to previous estimates. The size of the Athabascan dunes' in comparison with that of terrestrial dunes suggests that these martian dunes took at least 1-2 days to grow. Their flattened morphology implies that they were formed at high subcritical flow and that the flood flow that formed them receded very quickly. (C) 2004 Elsevier Inc. All rights reserved.
PD SEP
PY 2004
VL 171
IS 1
BP 68
EP 83
UT ISI:000223407200006
ER

PT J
AU Fenton, LK
Bandfield, JL
Ward, AW
TI Aeolian processes in Proctor Crater on Mars: Sedimentary history as analyzed from multiple data sets
SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
AB Proctor Crater is a 150 km diameter crater in Noachis Terra, within the southern highlands of Mars. The analysis leading to the sedimentary history incorporates several data sets including imagery, elevation, composition, and thermal inertia, mostly from the Mars Global Surveyor mission. The resulting stratigraphy reveals that the sedimentary history of Proctor Crater has involved a complex interaction of accumulating and eroding sedimentation. Aeolian features spanning much of the history of the crater interior dominate its surface, including large erosional pits, stratified beds of aeolian sediment, sand dunes, erosional and depositional streaks, dust devil tracks, and small bright bed forms that are probably granule ripples. Long ago, up to 450 m of layered sediment filled the crater basin, now exposed in eroded pits on the crater floor. These sediments are probably part of an ancient deposit of aeolian volcaniclastic material. Since then, some quantity of this material has been eroded from the top layers of the strata. Small, bright dune forms lie stratigraphically beneath the large dark dune field. Relative to the large dark dunes, the bright bed forms are immobile, although in places, their orientations are clearly influenced by the presence of the larger dunes. Their prevalence in the crater and their lack of compositional and thermal distinctiveness relative to the crater floor suggests that these features were produced locally from the eroding basin fill. Dust devil tracks form during the spring and summer, following a west-southwesterly wind. Early in the spring the dust devils are largely restricted to dark patches of sand. As the summer approaches, dust devil tracks become more plentiful and spread to the rest of the crater floor, indicating that the entire region acquires an annual deposit of dust that is revealed by seasonal dust devils. The dark dunes contain few dust devil tracks, suggesting that accumulated dust is swept away directly by saltation, rather than by the passage of dust devils. Spectral deconvolution indicates that the dark dunes have infrared spectra consistent with basalt-like materials. The average thermal inertia calculated from Thermal Emission Spectrometer bolometric temperatures is 277+/-17 J m(-2) s(-0.5) K-1, leading to an effective grain size of 740+/-170 mm, which is consistent with coarse sand and within the range expected for Martian sand. The coarse sand that composes the large dune field may have originated from outside the crater, saltating in from the southwest. Most of the transport pathway that delivered this sand to the dune field has since been eroded away or buried. The sand was transported to the east center of the crater floor, where beneath the present-day dunes a 50 m high mound of sand has accumulated. Dune slip faces indicate a wind regime consisting of three opposing winds. Some of these wind directions are correlated with the orientations of dust devil tracks and bright bed forms. The combination of a tall mound of sand and three opposing winds is consistent with a convergent wind regime, which produces the large reversing transverse and star dunes that dominate the dune field. The dark dunes have both active slip faces and seemingly inactive slip faces, suggesting that the dunes vary spatially in their relative activity. Nevertheless, the aeolian activity that has dominated the history of Proctor Crater still continues today.
PD DEC 4
PY 2003
VL 108
IS E12
AR 5129
UT ISI:000187484300001
ER

PT J
AU Greeley, R
Wilson, G
Coquilla, R
White, B
Haberle, R
TI Windblown dust on Mars: laboratory simulations of flux as a function of surface roughness
SO PLANETARY AND SPACE SCIENCE
AB Experiments were conducted to determine the flux of dust (particles < few microns in diameter) under Martian atmospheric conditions for surfaces of three aerodynamic roughnesses (z(0)). For smooth surfaces on Mars (z(0) = 0.00125 cm corresponding to 0.0125 cm on Mars) suspension threshold was not achieved at the highest velocities run (u(*) = 322 cm/s); for a moderately rough surface (z(0) = 0.010 cm corresponding to 0.10 cm on Mars), flux averaged 1.5 x 10(-7) g/cm(2)/s; for a rough surface (z(0) = 0.015 cm corresponding to 0.15 flux on Mars), flux averaged 5 x 10(-7) g/cm(2)/s. Although the results are preliminary, flux varied widely as a function of wind speed and roughness, suggesting that raising dust into suspension on Mars is complex. Nonetheless, using these results as a guide, 9000 Mt of dust could be raised into the atmosphere of Mars per second from only 5% of the surface. (C) 2000 Elsevier Science Ltd. All rights reserved.
PD OCT-DEC
PY 2000
VL 48
IS 12-14
BP 1349
EP 1355
UT ISI:000166134700018
ER

PT J
AU Zimbelman, JR
TI Non-active dunes in the Acheron Fossae region of Mars between the Viking and Mars Global Surveyor eras
SO GEOPHYSICAL RESEARCH LETTERS
AB Comparison of a high resolution Viking image (422B10; 8 m/pixel) with a Mars Orbiter Camera image (SP2-502/06; 5.6 m/pixel) of dunes in the Acheron Fossae region of Mars (38 degrees N, 135 degrees W) reveals that the dunes moved <1 pixel during a span of almost 21 Earth years. Very shallow illumination in the MOC image indicates the dunes are <1.5 m high. The images indicate that any movement of these Martian dunes is <0.4 m/yr, a rate that is less than the documented movement of comparable dunes on Earth by a factor of up to 200. The Acheron Fossae dunes occur within a region of low thermal inertia, indicating that the dunes may be stabilized by a pervasive dust cover. Alternatively, the saltation threshold was not exceeded significantly at this location in more than 20 years.
PD APR 1
PY 2000
VL 27
IS 7
BP 1069
EP 1072
UT ISI:000086224500043
ER

PT J
AU Anderson, FS
Greeley, R
Xu, P
Lo, E
Blumberg, DG
Haberle, RM
Murphy, JR
TI Assessing the Martian surface distribution of aeolian sand using a Mars general circulation model
SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
AB A sand transport model using White's [1979] sand flux equation and the Mars general circulation model [Pollack et al., 1990] was developed to understand the erosional sources, transport pathways, and depositional sinks of windblown sand on Mars. An initially uniform distribution of sand (4 mm over the entire surface) is regionally transported based on wind stress, saltation threshold, and percentage of topographic trapping. Results are consistent with the observed polar and Hellespontus dunes and Christensen's [1986] modeled block size distribution, but only for an extremely low saltation threshold (0.024 N/m(2)). Low thresholds generally result in transport of sand-sized particles originating in the northern mid latitudes to the north pole, and transport from the northern lower latitudes to the southern hemisphere, Our results indicate that the polar dune fields could form in 50,000 years, consistent with the active polar dunes and lack of longitudinal dunes observed on the surface of Mars.
PD AUG 25
PY 1999
VL 104
IS E8
BP 18991
EP 19002
UT ISI:000082193300009
ER

PT J
AU Fernandez, W
TI Martian dust storms: A review
SO EARTH MOON AND PLANETS
AB A review of the dust storms observed on Mars is made. This includes the seasonal and interannual variability of planet-encircling and regional dust storms. Although there is a significant interannual variability, planet-encircling dust storms have been observed to form during the southern spring and summer seasons, while regional dust storms tend to occur more frequently. Some aspects of possible mechanisms associated with the origin, maintenance and decay of the dust storms are also discussed.
PY 1997
VL 77
IS 1
BP 19
EP 46
UT ISI:000078954400002
ER

PT J
AU Edgett, KS
TI Aeolian dunes as evidence for explosive volcanism in the Tharsis region of Mars
SO ICARUS
AB Two transverse dune fields occur among Late Amazonian volcanic and aeolian landforms in southwestern Tharsis, Mars. The first is located similar to 70 km northwest of Biblis Patera, around 5 degrees N, 125 degrees W. The second is located about 500 km northwest of Arsia Mons, at 2 degrees S, 130 degrees W. The latter is the largest dune field thus far documented to occur in the equatorial latitudes of Mars. Unlike other dunes on the planet, both dune fields in Tharsis have low thermal inertias (<2.7 x 10(-3) cal cm(-2) sec(-0.5) K-1) and high albedos (similar to 0.26) that are indistinct from their surrounding terrain. Both dune fields have superposed features, such as impact craters, lava flows, smooth-surfaced units, and bright wind streaks. The dune fields therefore appear to be inactive and mantled by fine-grained material (i.e., particles <60 mu m). To form, aeolian dunes require a supply of sand. On Earth, most dune sands are supplied by fluvial and littoral processes, but this is not the case in Tharsis on Mars. Because they are superposed on a Late Amazonian surface, the climate is assumed to have been hyper-arid throughout the time that the dunes have existed. Under these conditions, the only plausible source for quantities of sediment sufficient to form transverse dune fields is explosive volcanism. Therefore, the two dune fields in Tharsis are evidence that explosive volcanism has occurred in this region in the Late Amazonian Epoch. (C) 1997 Academic Press.
PD NOV
PY 1997
VL 130
IS 1
BP 96
EP 114
UT ISI:A1997YK78400008
ER

PT J
AU THOMAS, PC
GIERASCH, PJ
TI POLAR MARGIN DUNES AND WINDS ON MARS
SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
AB The approximately concentric arrangement of layered deposits and dune fields at the two Martian poles may reflect a nearly steady state dispersal of material from the polar deposits. Data on effective surface winds from high resolution Viking Images combined with theory of local winds suggest that the northern dunes are in part confined to a latitude band by winds generated by their own low albedo. Dispersal of the dark sand from the southern polar region is not subject to this kind of feedback because the irregular topography prevents areal accumulations sufficiently extensive to produce winds.
PD MAR 25
PY 1995
VL 100
IS E3
BP 5397
EP 5406
UT ISI:A1995QN87700015
ER

PT J
AU EDGETT, KS
BLUMBERG, DG
TI STAR AND LINEAR DUNES ON MARS
SO ICARUS
AB A field containing 11 star and incipient star dunes occurs on Mars at 8.8 degrees S, 270.9 degrees W. Examples of linear dunes are found in a crater at 59.4 degrees S, 343 degrees W. While rare, dune varieties that form in bi- and multidirectional wind regimes are not absent from the surface of Mars. The occurrence of both of these dune fields offers new insight into the nature of martian wind conditions and sand supply. The linear dunes appear to have formed through modification of a formerly transverse aeolian deposit, suggesting a relatively recent change in local wind direction. The 11 dunes in the star dune locality show a progressive change from barchan to star form as each successive dune has traveled up into a valley, into a more complex wind regime. The star dunes corroborate the model of N. Lancaster (1989, Progr. Physical Geogr. 13, 67-91; 1989, Sedimentology 36, 273-289) for the formation of star dunes by projection of transverse dunes into a complex, topographically influenced wind regime. The star dunes have dark streaks emanating from them, providing evidence that the dunes were active at or near the time the relevant image was obtained by the Viking 1 orbiter in 1978. The star and linear dunes described here are located in different regions on the martian surface. Unlike most star and linear dunes on Earth, both martian examples are isolated occurrences; neither is part of a major sand sea. Previously published Mars general circulation model results suggest that the region in which the linear dune field occurs should be a bimodal wind regime, while the region in which the star dunes occur should be unimodal. The star dunes are probably the result of localized complication of the wind regime owing to topographic confinement of the dunes. Local topographic influence on wind regime is also evident in the linear dune field, as there are transverse dunes in close proximity to the linear dunes, and their occurrence is best explained by funneling of wind through a topographic gap in the upwind crater wall. (C) 1994 Academic Press, Inc.
PD DEC
PY 1994
VL 112
IS 2
BP 448
EP 464
UT ISI:A1994QF36600015
ER

PT J
AU GREELEY, R
WILLIAMS, SH
TI DUST DEPOSITS ON MARS - THE PARNA ANALOG
SO ICARUS
AB Parna is an Australian aboriginal word meaning ''sandy dust.'' It has been applied to deposits of clay, silt, and sand which were initially transported by the wind as aggregates, or pellets, of sand size. Parna is distinguished by its silt and clay content, which in some cases exceeds 85% of the total volume of the deposit. Much of the fine-grained playa silt and clay is incorporated into the parna as sand-sized aggregates, which greatly facilitate their transportation and reworking by the wind. Rain following aggregate emplacement can cause their disintegration, rendering the parna immobile by the wind, yet some pellets can survive several wetting/drying episodes. Parna deposits on Earth occur both as dune forms and as sheet deposits which mantle older terrains. In both cases the deposits are typically derived from lacustrine (lake) beds, such as playas. There is substantial evidence to suggest that bodies of water existed on Mars in the past. Thus, the potential is high for lacustrine deposits and the formation of parna on Mars. Although no parna dunes have been identified, it is suggested that the deposits derived from White Rock (-8 degrees, 335 degrees W), near Mamers Valles (34 degrees, 343 degrees W), and elsewhere on Mars may represent sheet parna. Data obtained from the Mars-94/96 missions and potential landed spacecraft may provide additional evidence for the existence of parna on Mars. (C) 1994 Academic Press, Inc.
PD JUL
PY 1994
VL 110
IS 1
BP 165
EP 177
UT ISI:A1994PG37000009
ER

PT J
AU EDGETT, KS
LANCASTER, N
TI VOLCANICLASTIC AEOLIAN DUNES - TERRESTRIAL EXAMPLES AND APPLICATION TO MARTIAN SANDS
SO JOURNAL OF ARID ENVIRONMENTS
PD SEP
PY 1993
VL 25
IS 3
BP 271
EP 297
UT ISI:A1993MJ22200001
ER

PT J
AU EDGETT, KS
CHRISTENSEN, PR
TI THE PARTICLE-SIZE OF MARTIAN AEOLIAN DUNES
SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
AB The effective particle size of unconsolidated materials on the Martian surface can be determined from thermal inertia, due to a pore size dependence of thermal conductivity at Martian atmospheric pressures. Because dunes consist of a narrow range of well-sorted, unconsolidated particles, they provide for a test of the relationship between particle size and thermal inertia calculated from midinfrared emission data for the Martian surface. We use two independent approaches. First, thermal inertia data indicate that Martian dunes have an average particle size of about 500 +/- 100-mu-m, or medium to coarse sand. Second, we determine expected dune particle sizes from grain trajectory calculations and the particle size transition from suspension to saltation. On Earth, the transition occurs for a grain when the ratio of the terminal fall velocity to the wind friction speed (u*t) is near unity; for grains at u*t this occurs at about 52-mu-m. Terrestrial dune sands have a mean of 250-mu-m and are composed entirely of grains > 52-mu-m. The corresponding Martian transition grain size is about 210-mu-m, suggesting that Martian dunes should be significantly coarser than terrestrial dunes. Grain saltation path length as a function of particle size also show s that under Martian conditions, larger grain s than on Earth will become suspended. Both approaches indicate that Martian dune sand should be coarser than terrestrial dune sand. Thus, while terrestrial dune grains are in the fine to medium sand range, the average Martian dune sediments are probably medium to coarse sands. These results closely match the grain sizes determined from thermal inertia models, providing the first direct test of the validity of these models for actual Martian surface materials.
PD DEC 25
PY 1991
VL 96
IS E5
BP 22765
EP 22776
UT ISI:A1991GY19900005
ER

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