ancient wet aeolian environments on earth: clues to presence of fossil/live microorganisms on mars

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Icarus 171 (2004) 39–53www.elsevier.com/locate/icaru

Ancient wet aeolian environments on Earth:clues to presence of fossil/live microorganisms on Mars

William C. Mahaneya,∗, Michael W. Milnera, D.I. Netoffb, David Mallochc, James M. Dohmd,Victor R. Bakerd, Hideaki Miyamotoe,f , Trent M. Hareg, Goro Komatsuh

a Geomorphology and Pedology Lab, York University, 4700 Keele St., North York, ON M3J 1P3, Canadab Department of Geography and Geology, Sam Houston State University, Huntsville, TX 77341, USA

c Department of Botany, University of Toronto, Toronto, ON M5S 1A1, Canadad Department of Hydrology and Water Resources, University of Arizona, Tucson, AZ 85721, USA

e Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USAf Department of Geosystem Engineering, University of Tokyo, Japan

g United States Geological Survey, Flagstaff, AZ 86001, USAh International Research School of Planetary Sciences, Università d’Annunzio, Viale Pindaro 42, 65127 Pescara, Italy

Received 10 July 2003; revised 22 April 2004

Available online 26 June 2004

Abstract

Ancient wet aeolian (wet-sabkha) environments on Earth, represented in the Entrada and Navajo sandstones of Utah, contain pipconsidered to be the product of gas/water release under pressure. The sediments originally had considerable porosity allowing the ingresliving plant structures, microorganisms, clay minerals, and fine-grained primary minerals of silt and sand size from the surface dowthe sedimentary column. Host rock material is of a similar size and porosity and presumably the downward migration of fine-grainedwould have been possible prior to lithogenesis and final cementation. Recent field emission scanning electron microscopy (FESEM(energy-dispersive spectrometry) examination of sands from fluidized pipes in the Early Jurassic Navajo Sandstone reveal the pfossil forms resembling fungal filaments, some bearing hyphopodium-like structures similar to those produced by modern troparasites. The tropical origin of the fungi is consistent with the paleogeography of the sandstone, which was deposited in a tropicaenvironment. These fossil fungi are silicized, with minor amounts of CaCO3 and Fe, and in some cases a Si/Al ratio similar to smectite. Texist as pseudomorphs, totally depleted in nitrogen, adhering to the surfaces of fine-grained sands, principally quartz and orthoclase. Siwet aeolian paleoenvironments are suspected for Mars, especially following catastrophic sediment-charged floods of enormous mthat are believed to have contributed to rapid formation of large water bodies in the northern plains, ranging from lakes to oceaevents are suspected to have contributed to a high frequency of constructional landforms (also known as pseudocraters) relatedvolatiles and water-enriched sediment underneath athick blanket of materials that were subsequently released to the martian surface, formingpiping structures at the near surface and constructional landforms atthe surface. This constructional process on Mars may help unravecomplex history of some of the piping structures observed on Earth; on Earth, evidence for the constructional landforms has beerased and the near-surfacepiping structures exposed through millions of years of differential erosion and topographic inversion now occuras high-standing promontories. If the features on both Earth and Mars formed by similar processes, especially involving water and ovolatiles, and since the piping structures of Earth provided suitable environments for life to thrive in, the martian features in theplains should be considered as prime targets for physico/mineral/chemical/microbiological analyses once the astrobiological exploratiothe red planet begins in earnest. 2004 Elsevier Inc. All rights reserved.

Keywords:Extraterrestrial life; Entombed microorganisms on sand clasts; Pipe-like structures on Mars and Earth

radoa-

* Corresponding author.E-mail address:[email protected] (W.C. Mahaney).

0019-1035/$ – see front matter 2004 Elsevier Inc. All rights reserved.doi:10.1016/j.icarus.2004.04.014

1. Introduction

Jurassic sandstones and mudstones in the ColoPlateau (Fig. 1) commonly contain a wide range of deform

http://www.elsevier.com/locate/icarus

40 W.C. Mahaney et al. / Icarus 171 (2004) 39–53

Fig. 1. Location of the San Rafael Swell in theNavajo sandstone on the Colorado Plateau.

ing,

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tional features that include small-scale faulting and folddisruption of bedding, liquefaction, and fluidization(Chanet al., 2002). Fluidized masses of sandstone are particulabundant in the Middle Jurassic Carmel and Entrada fortions in the lower part of Glen Canyon National RecreatArea and in the Escalante Bench area located to the nof Glen Canyon. Here, these features typically form la(> 100-m wide and> 100-m high) cylindrical, pipe-likemasses that stand vertically and cut across adjacentrock at right angles, exposed by millions of years of diffential erosion of more competent piping structure matesurrounded by weaker host rocks (Fig. 2). These structureare among the largest fluidization pipes of continentalgin in the stratigraphic record(Netoff, 2002). The size ofthe structures, the mixed sandand breccia fabric and the Msignature, both in clay skins and minor, relict, carbonatement, conjure up kimberlitic diatreme structures(Mitchell,1986). Other pipe-bearing Jurassic strata in the Plateauclude the Navajo sandstone, the Cow Springs sandstonethe Page sandstone. Many of these pipes stand either initive or negative relief compared to the enclosing host rbecause of the amount and type of cement in the pipetive to the surrounding rock, indicating that the pipes ac

t

d-

-

as conduits for groundwater movement during or after lification(Netoff and Shroba, 2001).

Fossil microorganisms (e.g., bacteria and fungi) ocon and between sand grains of a fluidization pipe witthe Early Jurassic Navajo sandstone (Fig. 3). They occur innear-surface samples of dip-slope outcrops in the San R(Green River) Desert of south-central Utah. Pipe-bearingwater may have provided habitats for these organismthrive and subsist.

The unique occurrence of clusters of huge fluidizatpipes may be the result of several coincidental envirmental factors, including: (1) an abundant source of figrained sand; (2) a long-term subsiding depositional basin(3) a persistent arid climate; (4) water saturation; (5) woverpressurization; (6) preservation (burial vs. erosion);(7) a triggering mechanism (possibly including earthquamagmatism, meteoric impact, hydrothermal activity). TJurassic wet aeolian-sabkha environment of the ColoPlateau meets most of the above conditions (it is probthat few if any other environments in the history of Easatisfied all of these requisite conditions).

Similar environmental conditions may have existedMars, especially during its first 500 myr or so of develo

Ancient wet aeolian environments on Earth 41

hown
Fig. 2. 3D perspective using a USGS Digital Orthoquad image at 1 m pixel−1 centered at longitude 111.207◦ W and latitude 37.182◦ N near Lake Powell inKane County, Utah. The image is draped over a 10 m pixel−1 National Elevation Dataset (NED) digital elevation model with no vertical exaggeration. Sis a 400 m-wide pipe structure cropping out of a debris apron.
lsesu-or-)that;

997;lyx-

rom

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onsuchhereLake

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ment and perhaps later episodically related to major puof magmatic-driven activity at Tharsis and Elysium sperplumes, which triggered catastrophic flooding of enmous proportions(Baker et al., 2002; Dohm et al., 2002.These flood waters with estimated peak dischargesranged from 107 to 1010 m3 s−1 (Komar, 1979; Baker, 1982Robinson and Tanaka, 1990; Komatsu and Baker, 1Dohm et al., 2001a)ponded in the northern plains to rapidform large water bodies and initiate short-lived climatic ecursions (approximately tens of thousands of years) fprevailing cold and dry desert conditions(Baker et al.,1991, 2001; Dohm et al., 2001b; Fairén et al., 2003). Thesecatastrophically-derived environments coupled with graalmost half that of Earth may have contributed to the fmation of piping structures and associated constructilandforms through the release of trapped volatiles and waenriched sediments from beneath a thick blanket of materials, forming habitats for the development of microorganis

to thrive and persist similar to those of Earth. FeaturesMars, often referred to as pseudocraters, may markphenomena, especially in parts of the northern plains wpossible paleolakes as much as 15 times the size ofHuron have been mapped (e.g.,Scott et al., 1995) and/oroceans are hypothesized to have existed(Parker et al., 1993Head et al., 1999; Fairén et al., 2003), such as in the ChrysPlanitia region (Figs. 4A, 4B). Extensive aeolian deposisuch as the circum-polar sand seas of the northern hsphere(Dial, 1984; Tanaka and Scott, 1987; Dial and Doh1994)and seismic events related to magmatic-driven acity (Anderson et al., 2001)and impact cratering events (e.gScott and Tanaka, 1986) may have both contributed to thformation of pipe structures in the northern plains of Maespecially when the putative large water bodies were prein the northern plains. In addition, pipe-like conduits in mtian dune fields could have provided a long-term moistsource that would have been protected from intense co


uc-

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ewmal

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Fig. 3. Stratigraphy of Jurassic rocks in east-central Utah.

radiation and insulated from the dramatic temperature fltuations on the surface.

2. Previous work on pipes

Cylindrical and irregular-shaped bodies of deformsandstone that cut across the enclosing host rock haveidentified in a variety of continental, marine, and transitiopaleoenvironments. They have been calledclastic plugs, col-lapse plug pipes, sandstone cylinders, sandstone plupipes, sandstone pipes, silica plugs, pipe-like slump sttures, type B pillars, fluid escape structures, clastic pipsedimentary pipes, sand cylinders, dewatering pipes, spipes, breccia pipes, tubularfluidization pipes, injectionstructures, escape burrows, and sand volcano vents(seesummaries of these features inHunter et al., 1992, anDionne and Perez Alberti, 2000). The intensity of deformation of these structures ranges from brittle fracture (smscale faults, joints, and deformation bands) to hydropladeformation (sagged and contorted beds) to liquefiedfluidized bodies (without primary sedimentary structure)

The origin of these deformational structures remains ctroversial. Down-faulted and slumped beds in pipes an

n

adjacent host rock have been interpreted as strata collainto underground cavities(Weir et al., 1961; Barrington anKerr, 1963; Wenrich, 1985; Hunter et al., 1992). Beds oflimestone and gypsum are common in units such asCarmel, and thin beds of fresh water limestone (playaposits) occur as thin lenses within the predominantly eoNavajo sandstone. Contorted beds in the Carmel and Enhave been attributed to dune loading(Baars, 1995, 2000,plastic adjustment of water-saturated muds and sandsgently-sloping sea floor(Baker, 1946), and meteoric impac(Alvarez et al., 1998).

Cylindrical masses of homogeneous rock enclosedstratified host rock calls for the injection of water andsand slurries from above or below by over-pressuriwater or gasses(Gabelman, 1955; Phoenix, 1958; Alle1961; Schlee, 1963; Megrue and Kerr, 1965; Lowe, 19Hannum, 1980; Collinson, 1994; Dionne and Perez Albe2000; Baer and Steed, 2000). Overpressurization may havbeen caused by overburden pressure, perhaps amplifitriggered by seismic vibrations associated with faulting, vcanism, or meteoric impact(Jones, 1972; Horowitz, 1982Glennie and Bullar, 1983; Allen, 1986; Alvarez et al., 19Galli, 2000). Although the case can be made for slurryjection from above, such as from impact processes, thecommon interpretation is injection from below by ascendinsprings(Dionne and Perez Alberti, 2000)or in situ fluidiza-tion of host rock(Netoff, 2002). The boiling sand springalong the Dismal River in the Sand Hills of Nebraska rthrough cylindrical conduits from a pressurized aquiferunknown source(Guhman and Pederson, 1992).

Regardless of their origin, there is little disagreementduring and after the formation of these cylindrical structuthere was sufficient porosity and permeability to permit fland gas to pass through them. Pore space of 12 pipeples from the Entrada Sandstone determined in thin-seaveraged 22.4 percent, and initial void space (prior tomentation and clay coatings) averaged 36.9 percent(Netoffand Shroba, 2001). Thin-section comparison of pipe vershost rock indicates that diagenetic alterations of the pipehost differ, also suggesting differential water transmissivThe mineralogy of clay coatings on detrital grains as was interstitial clay [smectite (montmorillonite) with minillite] in the Entrada pipes reflects low temperature diagesis (Netoff et al., 1995). A significant Mg signature in botclay skins on sand grains and relict carbonate cement imdolomitization related to these pipes. A few pipes in NMexico have clay mineral suites that suggest hydrotheralteration(Megrue and Kerr, 1965).

3. The study area

A cluster of clastic pipes crops out in an area in the Jusic Navajo sandstone ‘slickrock’ on the dip slope of a lanortheast trending monocline called the San Rafael S(seeRigby, 1987) in the Canyonlands Section of the Co


, is

tori

(A)

Fig. 4. (A) Context image of a region within Acidalia Planitia (33.045◦ N, 322.004◦ E). This region, which includes patterned ground and pseudocratersthe debouch region of the Circum-Chryse outflow channels and the site of a possible lake(Scott et al., 1995)and/or paleo-ocean(Parker et al., 1993). Alsoshown is location of 4B (outlined area “B”). (B) THEMIS visual image showingpseudocraters and terraces that form the margins of some of the promones(image width is approximately 23 km; north is a top). Both images are courtesy of ASU THEMIS Science Team.

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orado Plateau in Utah (Fig. 1). The fold is likely fault-coredand of Laramide age, presumably much younger thanpipe and host rock. Near-surface (0–7 cm) samples ofpipe sandstone, as well as the enclosing cross-beddedrock, were extracted from a barren dipslope located ab200 m to the northeast of the Temple Wash watergap (38◦39.541′ N; Long. 110◦39.833′ W, elev. 1670 m a.s.l.Temple Mountain Quadrangle).

A thick sequence (700–900 m) of Jurassic sedimenstrata is exposed along the San Rafael Swell (Fig. 1). Theyrepresent a sequence of alternating eolian dunes (WinNavajo, Page, and Entrada), fluvial deposits (Kayentalower Morrison), and shallow marine/tidal flat depos(Carmel, Curtis, Summerville, and upper Morrison). Theleogeographic setting was one of transgressing and reging, shallow tropical seas bordered by sabkha and coand inland dune fields, crossed occasionally by streamsuing from nearby and distant highlands. The Early JuraNavajo sandstone, which is discussed here, represents aceptionally thick, widespread erg. Thin lenses of limestinterbedded with the cross-bedded sandstone are probinterdune playa deposits. Soft sediment deformational sttures within the Navajo, Page, and Entrada sandstonescluding fluidization pipes, suggest that at least some of thunits are wet eolian.

4. Methods

Samples were examined by light microscope (LM) asubsamples prepared for analysis by secondary emisScanning Electron Microscope (JEOL-840 JSM) and FEmission Scanning Electron Microscope using a Hitach4500 following methods outlined byMahaney (1990, 2002

t

,

-l

-

y

-

and Vortisch et al. (1987). A minimum of 300–500 grainswere examined per sample with selected groups of 50samples studied in detail. Twenty-five bulk samples wrecovered from the San Rafael Swell (pipe) of the Navsandstone and subsampled to derive an unwashed septhe remainder subjected to gravimetric separation to obtailight and heavy fractions (seeMahaney and Milner, 1998).The results discussed herein are from the unwashedtions of medium (500–250 µm) and fine and very fine (2563 µm) sands coated with gold-palladium. The imagerrepresentative of the grains studied. Chemical spectraobtained by energy dispersive spectrometry using a LISIS system.

5. Results

A wide field image of filaments partially embeddedcoatings of clay minerals and carbonate, both of which hsignificant signatures of Mg and Fe–Mg silicates is showFig. 5A. The filaments are present mainly in the pipe strtures being only infrequently observed in the host rock,all lack the blue-green colors of living forms as seen unthe LM. Various silt-sized fragments, consisting of mainorthoclase and quartz with occasional mica, are loosely embedded (bottom) to well encrusted (top) in the coatinga very fine sand particle. The angularity of fine sandsilt in aeolian sediments is well documented (seeMahaney,2002), with resulting collisions engendering abrasiontigue, which creates a disrupted lattice in quartz andthoclase. This disrupted lattice, in turn, produces a greproportion of angular to subangular grains.

The enlargement of the frame inFig. 5A, shown inFig. 5B, emphasizes the interconnectedness of filam


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n B,in-

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osi-er-nd-

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(B)

Fig. 4. Continued.

structures and the biofilm thatforms where filaments joinsuch as in the center and lower parts of the frame. Tis little in the way of chemical differences between theaments and more amorphous biofilms, all encrustedCa–Mg carbonate, clay minerals, and Fe–Mg silicates.

At first glance, the large bulbous framboid form shoin Fig. 5Cappears to be pyrite; chemistry indicated by Eshows an Si:Al ratio of nearly 2:1 with minor amounts

Ca, K, and little Fe. The Ca:K ratio is approximately 3which supports an identification of randomly interstratifiillite-smectite with somewhat higher smectite. The mateappears to be of biogenic origin, although there is the rempossibility that the colliform may result from heating withe electron beam.

A representative image of filaments more deeply embded or encrusted in the surface of thick coatings on quis shown inFig. 5D. Even detrital particles, which are nmerous on the surface of the quartz grain, are more thicoated than on previous frames and here EDS spectracate a combination of 1:1 and 2:1 clay minerals mixed inamong the filaments. The large cup-like feature attachea filament to the right of center may be fossilized fungi wa slightly higher Si composition than along the central fiment, which disappears into thick coating on the upperof the grain.

The chemistry of the filaments shown inFig. 5 is simi-lar to the EDS spectrum shown inFig. 6with the exceptionthat C and Ca are sometimes slightly higher, whereas Si isometimes lower.

More robust filament forms, sometimes containing ribbstructures, are shown inFig. 7A where a fungus-like organism is found with radiating branches deeply embedin coating. Numerous clay flakes are shown in this fraalmost all of which are partially coated with amorphous mterial with a combined C, Ca, Fe, Si, and Al compositthat is variable. A wide field of view at lower magnificatioof this organism well embedded on the surface of ortclase is shown inFig. 7B. The interbranching filaments othe upper portion of the grain grade into faint traces thatwell-encrusted on the left-hand side. Numerous coated bigenic forms are well preserved in the middle of the grathe coating is perhaps among the thickest encountered ipopulation of grains studied. The area below the mainment complex contains a triangular shaped area somefresher than the rest of the coated surface. This areahave been exposed by weathering of orthoclase, at stime during diagenesis. The enlargement of the area ishown in C, illustrates the degree to which filaments areterconnected and show excellentcharacteristics, includingflattened bioform or apron extending from the filament inlow central portion of the image.

A further enlargement (Fig. 7D) shows the character okaolin flakes and fungal hypha-like structures and a cform biogenic form to the upper right.

Variations in the chemical composition of the filameshown inFigs. 5 and 7are shown inFigs. 8 and 9. Alu-minum ranges from low to high depending on the comption of coatings and the amount of clay mineral or weathing products present. Abundant quartz in the Navajo Sastone was largely subjected to precipitation of Si durand after the slowdown in high-energy, hydrothermaltivity in the pipes. The high concentration of Si on boquartz and orthoclase grains in the pipes is due to theable presence of silica, as indicated by the variable amo


ith

Fig. 5. (A) Wide field image of quartz encrusted with filaments partially embedded in Fe-silicate coating. (B) Enlargement of area in center of (A). Triangulararea shows fine texture composed of clay minerals with variable Si:Al ratios indicating a mix of smectite and kaolinite. (C) Encrusted fossilized colliformbiogenic particles with high Si:Al ratio possibly indicating cementation with smectite and minor carbonate. (D) Quartz grain with filaments encrusted showingSi:Al ratio of 3:1. Large cup-like form attached to filament is probably fungi. This frame shows different degrees of filaments embedded in coating wvariable amounts of carbonate, clay minerals and Fe.

tra,he

ions

the

line

areent

theboths.

eed

con-th-;al.,,rs-eredfre-ing

dis

Fig. 6. EDS spectrum of the filament (center) ofFig. 5B. Four spot checkswith EDS along the length of the filament principally give similar specmostly with Si:Al of 2:1. Ca varies somewhat but is smaller than Al. Tfossilized form is cemented mainly with Si, carbonate and minor infusof clay minerals.

of oxygen seen onFigs. 8 and 9. Iron, which is alwayspresent in small amounts, is either a minor constituent of

clay complex or an oxide either in amorphous or crystalform.

Biogenic forms with the character of a delta or fansometimes encountered on and interconnected with filamfringes. They may be artifacts produced by heating ofsample by the electron beam, although they are seenwith high (20 kV) and low (1 kV) accelerating voltageThey are here referred to as biofilms (Fig. 10).

6. Formation of putative piping structures andconstructional landforms on Mars

Similar to Earth, wet aeolian paleoenvironments arsuspected for Mars, especially following Tharsis-derivepisodic catastrophic floods that are believed to havetributed to rapid formation of large water bodies in the norern plains, ranging from oceans to lakes(Baker et al., 1991Scott et al., 1995; Dohm et al., 2001a, 2001b; Fairén et2003; Komatsu et al., 2004a, 2004b). These flooding eventswhich resulted in the dissection and removal of kilometedeep, unvegetated upper crustal materials in the crathighlands, are suspected to have contributed to a highquency of constructional landforms and associated pipstructures, particularly in the Chryse, Utopia, and Isi


t infilaments

,

Fig. 7. (A) Branching filaments wellembedded in coating depict a well-formed colony of fungi. Filament in center shows a ribbed structure. Filamenupper center shows high Si:Al ratio of 4:1 with small Ca, Fe, and C and very minor Mg present. Silica is the main cement. (B) Encrusted grain withshowing well developed colonies of fungi. (C) High resolution image of areain upper right of (B). (D) Still higher resolution image to show details of filamentinterbranching with the mineral structure. Chemical composition of the mid part of the filament shows Si:Al ratio of 9:1 (seeFig. 5) along with higher Fe, Caand C. In this image most hexagonal flakes appear to be kaolinite. Tubular feature in center, with prominent primary node, may be filament with internal partsweathered out.

est-and

plain wa-

Fig. 8. EDS spectrum of the central branch of the filament inFig. 5A.Coating composition shows Si:Al of 2:1 and minor Ca and Mg sugging smectite. Anomalous C and O peaks, along with minor Ca and Mgpossibly Fe, represent carbonate.

Planitiae regions (Figs. 4A, 4B, 11 and 12). While volatile-release features such as mud volcanoes may aptly ex

Fig. 9. EDS spectrum of filament in the center ofFig. 5Bshowing a coatingof Si augmented with minor Fe and Ca, possibly carbonate.

many of the constructional features (e.g., seeOri et al., 2000;Tanaka et al., 2003), cinder cones(Scott et al., 1995),pseudocraters related to the interaction of ground ice or


mai
Fig. 10. Fossilized branched structure spreading out from filament giving the appearance of a flow-like feature, possibly a biofilm connected to thenfilament.
d)1;

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ter with volcanic flows(Carr, 1986), pingoes and ice-coreridges (Lucchitta, 1981; Rossbacher and Judson, 1981,moraines(Lucchitta, 1981; Scott and Underwood, 199Kargel and Strom, 1992; Lockwood et al., 1992), or moundsformed by the disintegration of stagnant ice covers(Grizzaffiand Schultz, 1989), cannot be ruled out as possible expnations for the formation of some of the relatively sm(generally< 1 km) conical hills, which occur in linear ancurvilinear assemblages and random clusters(Scott et al.,1995).

The origin of the piping structures that occur in the Etrada and Navajo sandstone of Utah is extremely diffito decipher due to the millions of years of erosion, as was deformation related to plate tectonism, and perhaps theare several possible mechanisms in their formation as previously discussed. All that remains are the piping structuthat are the result of millions of years of differential ersion of a more competent piping material surrounded bweaker host rock, resulting in inverted topography. Howepresent-day examples of mound-shaped constructionalforms produced by groundwater migration in wet-aeolenvironment are known on Earth, for example, in plaof southern Tunisia(Komatsu et al., 2004a, 2004b). Signifi-cant clues to their origin may be the constructional featuon Mars and associated putative underground piping stures related possibly to the following proposed succesof events: (1) episodic Tharsis-triggered floods would dis

-

cratered highland materials at kilometers depth, resultinsediment-charged floodwaters, (2) the sediment and volaticharged floodwaters would debouch into the northern plforming bodies of water ranging from oceans to lakes (laphases cycling with the existing water-enriched regionssulting from previous flood inundations), (3) the sedimentwould rapidly settle, entrapping volatiles and water-enricsediments, and finally (4) the trapped volatiles and waenriched sediments would eventually escape to the surfacresulting in the formation of underground piping structuand constructional landforms at the surface such asvolcanoes. Tectonism, volcanism, and impact crateringhave also triggered volatiles to the surface that were trapfor indefinite periods of time. A large occurrence of costructional landforms (pseudocraters), for example, ocin the Vastitas Borealis Formation(Tanaka et al., 2003). Thisgeologic formation is described in part as sedimentswere deposited during the formation of the Late HesperiEarly Amazonian Contact 2 ocean (e.g.,Head et al., 1999),related to Tharsis-induced flooding and related pond(Baker et al., 1991; Dohm et al., 2001a, 2001b; Fairénal., 2003), as well as spring-fed activity along the highlanlowland boundary(Tanaka et al., 2003).

It may be appropriate to assume that the clay coatof materials in the putative piping structures of Marsflect later diagenesis. In this case, the initial pore spacerepresent the volumetric water content. Assuming that


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Fig. 11. MOC narrow angle image m0702587 at 3.7 m pixel−1 resolution.Center of image is located at longitude 334.067◦ E and latitude 33.874◦ N.MOLA points (yellow dots) and topographic profile (4 times exaggeratedare shown. The promontory, which is transected by the MOLA point1.5 km in length excluding the debris apron.

typical value of the initial void space is about 35–40%,fluidized material during pipe fluidization may have possiviscosity of the sand-water mixture with solid content of 665%, ranging from about 10 Pa s;(Major and Pierson, 1992to 104 Pa s(Morton and Campbell, 1974). If the fluidizedmaterial is discharged from a pressurized aquifer throu

pipe, it may be possible to calculate the velocity of the mrial using the Hargen–Poiseuille model: the average veloV , may be written as:

V = − 1

8η

(−ρg + �P

L

)R2,

whereη is the viscosity,ρ is the density,g is the accelerationdue to gravity,�P/L is the pressure gradient, andR is theradius of the pipe. The pressure gradient may be causethe lithostatic pressure overriding the aquifer, such as incase where a relatively thick blanketing layer traps volatand water-enriched sediments. In this case, the pressure(−ρg + �P/L) becomes (−�ρg), where�ρ is the densitydifference between the fluidized material and the surrouing material. Taking the viscosity,�ρ, and the radius a104 Pa s, 100 kg m3, and 20 m, respectively, we obtain ththe average velocity is about 2 m s. Using this value aeffusion rate of material onto the surface, we performed americal simulation of a viscous flow movement(Miyamotoand Sasaki, 1998)on a surface to show a possible pattof spreading of the fluidized material.Figure 13shows howthe material spreads over a plane with different viscosity val-ues. Note that this calculation is performed only to disphow the material can spread, so the result should be coered as preliminary. One interesting point is that the fluidizematerial, which emerges at the surface, moves quickly eunder the martian gravity field and does not show a colulike shape. Therefore, there is a possibility that a fluidimaterial flows quickly without preserving its original foras observed, even though the above discussion does nclude a non-Newtonian effect, which may change the reWe note that, even if later water-drainage can changerheology of the material, this effect is not expected to blarge because the viscosity of the debris flow is still lthan 104 Pa s even with the solid content more than 8(Curry, 1966). Therefore, it is possible that the rheologicproperty of the material forming the positive landformdifferent from that during the formation of the cylindricstructures. Additional mechanisms such as secondary malization from inorganic and/or organic processes to chathe rheological property of the fluidized material maynecessary to maintain the observed constructional landf

As shown by the modeling above, the groundwater migtion produces piping structures but on reaching the surfthe water (and gas)-rich slurry spreads and forms moshaped constructional landforms. Both eroded out pipesconstructional landforms could be observed on Mars.

7. Discussion

7.1. Exobiological implications of purported pipingstructures on Mars

The presence of well-developed fossil structures, psibly of fungal origin, in piping structures of the Nava


4
Fig. 12. This 3D perspective displays MOC narrow angle image m0702587 draped over 128 pixels per degree MOLA topography (vertical exaggeration istimes). Distinct promontories and associated aprons are shown.
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sandstone in Utah poses the questions of when, andwhat time span, the microorganisms developed. It seunlikely that microbial life could develop and flourish duing pipe fluidization, because high-speed collisions of grawithin the high-energy flow would preclude growth of funMost probably, fungi colonies developed along with the slgrowth of coatings seen on the majority of sands witthe pipe structures, benefiting from the increasing prelence of iron and other ions necessary for life procesThe prevalence of structures resembling hyphopodia, fotoday mainly in tropical leaf parasites, suggests microcolonies grew and thrived when much of Utah was at troplatitudes. Evidence of the Early Jurassic macro-vegetaand soils may have been removed by erosion.

r Underground piping structures on Mars are suspein several localities in the northern plains such as witthe Vastitas Borealis Formation, marked at the surfaceconstructional landforms(Tanaka et al., 2003). The possi-ble connection between constructional landforms andpothesized near-surface piping structures of Mars withing structures on Earth (the largest documented in GCanyon National Recreation Area) poses a further qtion of whether extraterrestrial life might reside, or haresided within them. We know from what is reported herthat Jurassic microflora have developed, its associationgrain mineralogy and coatings documented above. Theact relationship with soils and vegetation that existedthe site is not known. These have long since vanishe


Fig. 13. Simulated Newtonian flows spreading over the martian surface.

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similar microbial life forms have existed or do existMars, flourishing within pipe structures after quiescenwhat physiological processes might they have had? Wclimate did they exist in and over what span of time?present, given the presence of oxidants in the martianand the presence of lethal doses of radiation withinlower layers of the atmosphere, it is unlikely living funcan thrive at the planet’s surface. However, burial in the mtian soil may provide a habitat conducive to the growthmicroorganisms, either now or in the distant past, shieagainst cosmic rays and oxidizing substances that areabundant than on Earth. And development and survivamicroorganisms in sediments beneath the surface, parlarly in an environment where water and nutrients are pvided from below (via pipe conduits), seems more plable.

As demonstrated on Earth, recovery of well-preserpseudoforms of fungus-like organisms poses still anoquestion of whether such forms might be present on M(life forms in meteorites,Folk, 1998). Past climatic conditions on Mars may have been more favorable in the ancpast for the presence of life forms with warmer temperatuand an atmosphere capable of trapping more ultraviolediation. There is even the prospect of asteroid impactEarth producing ejecta that have transported microbeMars(Mileikowsky et al., 2000). Such microbes would contain ferrichromes necessary for respiration processes ilife forms, compounds that rely on the intake of iron. Tpresence of iron in small quantities in the coatings on Nasands may well in part result from the decay of microganisms at the termination of their life cycles. The avercomposition of iron in the martian crust is estimated to18%(Hviid et al., 1997), a concentration about 4 to 5 tim

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the average on Earth, providing an environment in whmicrobial life might thrive. When compared to present cditions, warmer temperatures on Mars are thought to hexisted at times during the Noachian and Hesperian Pe(Baker et al., 2002; for explanation of the Time-StratigraphSystem of Mars, seeScott and Tanaka, 1986), approach-ing present-day and paleotemperatures in some of theest environmental zones on Earth where microbial lifebeen studied in soils (seeMahaney, 1990, for Mt. Kenyain E. Africa andMahaney et al., 2001, for Antarctic pale-osols).

The detrital particles observed adhering to larger grainFigs. 5 and 7may be produced by high-energy collisions,kinetic energy of each particle converted into elastic enegiving rise to lattice shattering and grain attrition. The wgrinding process that takes place during transport is simto abrasion fatigue described byPascoe (1961)and to glacialgrinding described bySmalley (1966) and Mahaney (1995.This process is considered to provide fewer adheringticles than dry grinding(Mahaney, 2002), but neverthelesleaves larger particles well coated with smaller fragmeSome of this fragmental matter is no doubt produced duaeolian transport with the majority resulting from collisiowithin the pipe structures.

The high degree of porosity and the friable nature ofsandstone, together with Mg rich clay skins and relict cbonate cement, imply Mg-rich solutions. These fluids mhave possible mantle origin or result from a process relto injection of shallow-seated ground water of hydrotherorigin diffused through dolomites. Other, fault related fluflow involving Fe and Mn metasomatism(Chan and Parry2001; Chan et al., 1999, 2000), does not appear to be reprsented here.


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8. Conclusions

The fossilized filaments described herein are foundbedded in coatings up to 2 µm thickness with a variacomposition of carbonate, clay minerals, and Fe-silicates ograins of variable mineral composition in the pipe structuThe clay mineralogy includes 1:1 (Si:Al= 1:1) species likekaolinite to 2:1 species of smectite with various degreecrystallinity, with the clay coatings usually in excess of cbonate and iron.

The filaments, which are the main subject of enqurange from hyphae of variable types to species bearing stures strongly reminiscent of fungal hyphopodia. The pageographic significance of these filaments is that they gin pipe-like structures of the Navajo Sandstone when Uwas located at tropical latitudes during the Early Jurassicpresumably thrived after the pipes became quiescent. Hdrothermal activity within the pipe-like structures was suthat particles were acceleratedin high-energy pressure fieldthat would likely destroy fungi. The most likely hypothesis that fungi inhabited the pipes after quiescence, becing entombed in diagenetic coatings but with well-presermorphology. These pipe-related environments, which apto have been prevalent during the Jurassic on Earth, arpected to be present on Mars, and thus serve as prime tsites for future geologic and exobiologic investigations.

Acknowledgments

This research was made possible by Minor ReseGrants to WCM from York University and funds from Quternary Surveys (Toronto). We thank Sal Boccia of the Mallurgy Faculty, University of Toronto for assistance with tFE SEM. John Dawson (ITC, York University) preparedillustrations.

References

Allen, J.R.L., 1961. Sandstone—plugged pipes in the Lower Red Sandstonof Shropshire, England. J.Sediment. Petrol. 31, 325–335.

Allen, J.R.L., 1986. Earthquake magnitude frequency, epicentretance, and soft sediment deformation in sedimentary basins. SedimenGeol. 46, 67–75.

Alvarez, W., Staley, E., O’Connor, D., Chan, M.A., 1998. Synsedimendeformation in the Jurassic of southeastern Utah; a case of impacting? Geology 26 (7), 579–582.

Anderson, R.C., Dohm, J.M., Golombek, M.P., Haldemann, A.FFranklin, B.J., Tanaka, K.L., Lias, J., Peer, B., 2001. Primary cenand secondary concentrations of tectonic activity through time in wern hemisphere of Mars. J. Geophys. Res. 106, 20563–20585.

Baars, D.L., 1995. Navajo County: A Geological and Natural History ofFour Corners Region. Univ. of NewMexico Press, Albuquerque, NM255 p.

Baars, D.L., 2000. Geology of Canyonlands National Park, Utah. InSprinkel, D.A., Chidsey Jr., T.C., Anderson, P.B. (Eds.), GeologyUtah’s National Parks and Monuments. In: Utah Geological Association Publication, vol. 28. UGA, Salt Lake City, UT, pp. 61–83.

-t

Baer, J.L., Steed, R.H., 2000. Geology of Kodachrome Basin StateKane County, Utah. In: Sprinkel, D.A., Chidsey Jr., T.C., AndersonP.B. (Eds.), Geology of Utah’s National Parks and Monuments. In: UGeological Association Publication, vol. 28. UGA, Salt Lake City, Upp. 448–463.

Baker, A.A., 1946. Geology of the Green River Desert—Cataract CanRegion, Emery, Wayne and Garfield counties Utah. United Stateslogical Survey, Bulletin, 951, 122 p.

Baker, V.R., 1982. The Channels of Mars. Univ. of Texas Press, Au198 p.

Baker, V.R., Strom, R.G., Gulick, V.C., Kargel, J.S., Komatsu, G., KV.S., 1991. Ancient oceans, ice sheets and the hydrological cyclMars. Nature 352, 589–594.

Baker, V.R., Strom, R.G., Kargel, J.S., Dohm, J.M., Ferris, J.C., 2001.recent, water-related landforms on Mars. In: Proc. Lunar Planet.Conf. 32nd. Abstract 1619 [CD-ROM].

Baker, V.R., Maruyama, S., Dohm, J.M., 2002. A theory of early platetonics and subsequent long-term superplume activity on Mars. ElectronGeosci. 7. http://lin.springer.de/service/journals/10069/free/confersuperplu/.

Barrington, J., Kerr, P.F., 1963. Collapse features and silica plugsCameron, Arizona. Geol. Surv. Am. Bull. 74, 1237–1258.

Carr, M.H., 1986. Mars: a water rich planet? Icarus 68, 187–216.Chan, M.A., Parry, W.T., 2001. Sandstone coloration and iron oxides

index to fluid flow in Jurassic reservoirs, southeastern Utah. Abstrwith programs. Geol. Soc. Am. 33 (6), 281.

Chan, M.A., Parry, W.T., Petersen, E.U., Hall, C.M., 1999. Iron and mganese mineralization, and timing of fault-related fluid flow in Jursic sandstones, southeastern Utah. Abstracts with programs. Geol. SoAm. 31 (7), 301.

Chan, M.A., Parry, W.T., Bowman, J.R., 2000. Diagenetic hematitemanganese oxides and fault-related fluid flow in Jurassic sandstonesoutheastern Utah. Am. Assoc. Petrol. Geol. Bull. 84 (9), 121310.

Chan, M.A., Netoff, D., Blakey, R., Kocurek, G., Alvarez, W., MarreR., 2002. Analysis of syndepositional deformation structures inPermian–Jurassic dune fields of theColorado Plateau. Geological Sciety of America, National Convention. Abstract, October, Denver, Corado.

Collinson, J.D., 1994. Sedimentary deformational structures. In: MaltmA. (Ed.), The Geological Deformation of Sediments. ChapmanHall, London, pp. 95–125.

Curry, R.R., 1966. Observation of alpine mudflows in the Tenmile ranCentral Colorado. Geol. Soc. Am. Bull. 77, 771–776.

Dial Jr., A.L., 1984. Geologic map of the Mare Boreum area of MaUnited States Geological Survey. Miscellaneous Investigation SMap I-1640 (1: 5,000,000).

Dial Jr., A.L., Dohm, J.M., 1994. Geologic map of science study areChasma Boreale region of Mars. United States Geological Survey.cellaneous Investigation Series Map I-2357 (1: 500,000).

Dionne, J.-C., Perez Alberti, A., 2000.Structures cylindriques verticaledans un depôt meuble Quaternaire, en Galice (Espagne) (Observationof vertical cylindrical structures in an unconsolidated Quaternaryposit, Galicia (Spain)). Geogr. Phys. Quatern. 54 (3), 343–349.

Dohm, J.M., Anderson, R.C., Baker, V.R., Ferris, J.C., Rudd, LHare, T.M., Rice Jr., J.W., Casavant, R.R., Strom, R.G., ZimbelmJ.R., Scott, D.H., 2001a. Latent outflow activity for western TharMars: significant flood record exposed. J. Geophys. Res. 106, 1212314.

Dohm, J.M., Ferris, J.C., Baker, V.R., Anderson, R.C., Hare, T.M., StrR.G., Barlow, N.G., Tanaka, K.L., Klemaszewski, J.E., Scott, D2001b. Ancient drainage basin of the Tharsis region, Mars: potesource for outflow channel systems and putative oceans or paleolJ. Geophys. Res. 106, 32943–32958.

Dohm, J.M., Maruyama, S., Baker, V.R., Anderson, R.C., Ferris, J.C., HT.M., 2002. Evolution and traits of Tharsis superplume, Mars. In:

http://lin.springer.de/service/journals/10069/free/conferen/superplu/




kyo,

rris,hern

ando

agle

r liq-

Eu-hstein

rich

iver,ge-

dikeung

-Mars

nntol-

-anort:

J.M.,.T.,ex-

i-

thel. 42,

,

rtian56–

logy

ofa and

n-.,s to

onSci.i-

ents

res.

,

transz

ions.

of40–

D.,or-0.

-

w

ck,.,to

as.

, S.

ra

rol-

withstern

ngEd.),n thetation,ing.

fea-r

erger,ins.

ate-

ve-eld,

Utah;ckyf

ood

istri-

ed-

als-

ar-h.

perplume International Workshop. Abstracts with Programs, Topp. 406–410.

Fairén, A.G., Dohm, J.M., Baker, V.R., de Pablo, M.A., Ruiz, J., FeJ.C., Anderson, R.C., 2003. Episodic flood inundations of the nortplains of Mars. Icarus 165, 53–67.

Folk, R.L., 1998. Nannobacteria-like carbon bodies in the AllendeMurchison carbonaceous chondrite meteorites, with comparisons tEarth. Abstracts with program. Geol. Soc. Am. 30 (7), A290.

Gabelman, J.W., 1955. Cylindrical structures in Permian (?) siltstone, ECounty, Colorado. J. Geology 63 (3), 214–227.

Galli, P., 2000. New relationships between magnitude and distance fouefaction. Tectonophysics 324, 169–187.

Glennie, K.W., Bullar, A.T., 1983. The Permian Weissliegend of NWrope: the partial deformation of aeolian dune sands caused by Zectransgression. Sediment. Geol. 35 (1), 43–81.

Grizzaffi, P., Schultz, P.H., 1989. Isidis basin: site of ancient volatile-debris layer. Icarus 77, 358–381.

Guhman, A.I., Pederson, D.T., 1992. Boiling sand springs, Dismal RNebraska; agents for formation of vertical cylindrical structures andomorphic change. Geology 20 (1), 8–10.

Hannum, C., 1980. Sandstone and conglomerate-breccia pipes andof the Kodachrome Basin area, Kane County, Utah. Brigham YoUniversity Geological Studies 27, 31–50.

Head, J.W., Hiesinger, H., Ivanov, M.A., Kreslavsky, M.A., Pratt, S., Thomson, B.J., 1999. Possible ancient oceans on Mars: evidence fromOrbiter Laser Altimeter data. Science 286, 2134–2137.

Horowitz, D.H., 1982. Geometry and origin of large-scale deformatiostructures in some ancient wind-blown sand deposits. Sedimeogy 29 (2), 155–180.

Hunter, R.E, Gelfenbaum, G.R., Rubin, D.M., 1992. Clastic pipes of probable solution-collapse origin in Jurassic rocks of the southern San JuBasin, New Mexico. United States Geological Survey, Bulletin, RepB 1808-L, pp. L1–L19.

Hviid, S.F., Madsen, M.B., Gunnlaugsson, H.P., Goetz, W., Knudsen,Hargraves, R.B., Smith, P., Britt, D., Dinesen, A.R., Morgensen, COlsen, M., Pedersen, C.T., Vistisen, L., 1997. Magnetic propertiesperiments on the Mars Pathfinder Lander: preliminary results. Scence 278, 1768–1770.

Jones, B.G., 1972. Deformation structures in siltstone resulting frommigration of an upper Devonian aeolian dune. J. Sediment. Petro935–940.

Kargel, J.S., Strom, R.G., 1992. Ancient glaciation on Mars. Geology 203–7.

Komar, P.D., 1979. Comparisons of the hydraulics of water flows in maoutflow channels with flows of similar scale on Earth. Icarus 37, 1181.

Komatsu, G., Baker, V.R., 1997. Paleohydrology and flood geomorphoof Ares Vallis. J. Geophys. Res. 162, 4151–4160.

Komatsu, G., Dohm, J.M., Hare, T.M., 2004a. Hydrogeologic processeslarge-scale tectomagmatic complexes in Mongolia–southern Siberion Mars. Geology 32, 325–328.

Komatsu, G., Ori, G.G., Marinangeli, L., Moersch, J.E., 2004b. Playa evironments on Earth: possible analogues for Mars. In: Chapman, M.GSkilling, P. (Eds.), Environments on Earth: Connections and Cluethe Geology of Mars. In press.

Lockwood, J.F., Kargel, J.S., Strom, R.B., 1992. Thumbprint terrainthe northern plains: a glacial hypothesis. In: Proc. Lunar Planet.Conf. 23rd, Houston, March 16–20,1992. Lunar and Planetary Insttute, Houston, pp. 795–796. Abstracts.

Lowe, D.R., 1975. Water escape structures in coarse-grained sedimSedimentology 22 (2), 157–204.

Lucchitta, B.K., 1981. Mars and Earth: comparison of cold-climate featuIcarus 45, 264–303.

Mahaney, W.C., 1990. Ice on the Equator. Wm Caxton Ltd., Ellison BayWI. 386 p.

Mahaney, W.C., 1995. Pleistocene and Holocene glacier thicknesses,port histories and dynamics inferredfrom SEM microtextures on quartparticles. Boreas 24, 293–304.

s

.

-

Mahaney, W.C., 2002. Atlas of Sand Surface Textures and ApplicatOxford Univ. Press, Oxford, UK. 237 p.

Mahaney, W.C., Milner, M.W., 1998. Zircon microstriators in the sandauriferous Andean tills: fine tools and noble metals. Boreas 27, 1152.

Mahaney, W.C., Dohm, J.M., Baker, V.R., Newsom, H.E., Malloch,Hancock, R.G.V., Campbell, I., Sheppard, D., Milner, M.W., 2001. Mphogenesis of antarctic paleosols: martian analog. Icarus 154, 113–13

Major, J.J., Pierson, T.C., 1992. Debris flow rheology: experimental analysis of fine-grained slurries. Water Resour. Res. 28, 841–857.

Megrue, G.H., Kerr, P.F., 1965. Alteration of sandstone pipes, Laguna, NeMexico. Geol. Soc. Am. Bull. 76, 1347–1360.

Mileikowsky, C., Cucinotta, F.A., Wilson, J.W., Gladman, B., HorneG., Lindegren, L., Melosh, J., Rickman, H., Valtonen, M., Zheng, J.Q2000. Natural transfer of viable microbes in space: 1. From MarsEarth and Earth to Mars. Icarus 145, 391–427.

Miyamoto, H., Sasaki, S., 1998. Numerical simulations of flood basalt lavflows: roles of some parameterson flow morphologies. J. GeophyRes. 103, 27489–27502.

Morton, D.M., Campbell, R.H., 1974. Spring mudflows at WrightwoodCalifornia. Quart. J. Eng. Geol. 7, 377–384.

Netoff, D., 2002. Seismogenically induced fluidization of Jurassic esands, south-central Utah. Sedimentology 49 (1), 65–80.

Mitchell, R.H., 1986. Kimberlites: Mineralogy, Geochemistry and Petogy. Plenum Press, New York. 442 p.

Netoff, D.I., Shroba, R.R., 2001. Conical sandstone landforms coredclastic pipes in Glen Canyon National Recreation Area, southeaUtah. Geomorphology 39 (3–4), 99–110.

Netoff, D.I., Cooper, B.J., Shroba, R.R., 1995. Giant sandstone weatheripits near Cookie Jar Butte, southeastern Utah. In: van Riper III, C. (Proceedings of the Second Biennial Conference on Research iColorado Plateau National Parks. Colorado Plateau Research SFlagstaff, AZ, pp. 25–53. National Park Transaction and ProceedSeries NPS/NRNUAU/NRTP-95-11.

Ori, G.G., Marinangeli, L., Komatsu, G., 2000. Gas (methane)—relatedtures on the surface of Mars and subsurface reservoirs. In: Proc. LunaPlanet. Sci. Conf. 31st. #1550.

Parker, T.J., Gorsline, D.S., Saunders, R.S., Pieri, D.C., SchneebD.M., 1993. Coastal geomorphology of the martian northern plaJ. Geophys. Res. 98, 11061–11078.

Pascoe, K.J., 1961. An Introduction to the Properties of Engineering Mrials. Blackie, London.

Phoenix, D.A., 1958. Sandstone cylinders as possible guides to paleomoment of groundwater. In: New Mexico Geological Society, 9th FiConference Guidebook. New Mexico Geological Society, Socorro, NMpp. 194–196.

Rigby, J.K., 1987. Stratigraphy and structure of the San Rafael Reef,A major monocline of the Colorado Plateau. In: Beus, S.S. (Ed.), RoMountain Section Centennial Field Guide, vol. 2. Geological Society oAmerica, Boulder, CO, pp. 269–273.

Robinson, M.S., Tanaka, K.L., 1990. Magnitude of a catastrophic flevent at Kasei Valles, Mars. Geology 18, 902–905.

Rossbacher, L.A., Judson, S., 1981. Ground ice on Mars: inventory, dbution, and resulting landforms. Icarus 45, 39–59.

Schlee, J.S., 1963. Sandstone pipes of the Laguna area, New Mexico. J. Siment. Petrol. 33, 112–123.

Scott, D.H., Tanaka, K.L., 1986. Geologic map of the western equatoriregion of Mars. United States Geological Survey. Miscellaneous Invetigation Series Map I-1802-A (1: 15,000,000).

Scott, D.H., Underwood Jr., J.R., 1991. Mottled terrain: a continuing mtian enigma. In: Proc. Lunar Planet.Sci. Conf. 21st, Houston, Marc12–16, 1990. Lunar and Planetary Institute, Houston, pp. 627–634


an-rvey.

n of

s.eries

.ogic

8.

er-,

uth-rvey.

.

Scott, D.H., Dohm, J.M., Rice Jr., J.W., 1995. Map of Mars showing chnels and possible paleolake basins. United States Geological SuMiscellaneous Investigations Series, Map I-2461 (1: 30,000,000).

Smalley, I.J., 1966. The properties of glacial loess and the formatioloess deposits. J. Sediment. Petrol. 36, 669–676.

Tanaka, K.L., Scott, D.H., 1987. Geologic map of the polar regions of MarUnited States Geological Survey. Miscellaneous Investigation SMap I-1802-C (1: 15,000,000).

Tanaka, K.L., Skinner Jr., J.A., Hare, T.M., Joyal, T., Wenker, A., 2003Resurfacing history of the northern plains of Mars based on geol

mapping of Mars Global Surveyor data. J. Geophys. Res. Planets 10doi:10.1029/2002JE001908.

Vortisch, W.B., Mahaney, W.C., Fecher, K., 1987. Lithology and weathing in a paleosol sequence on MountKenya. Geol. Paleotologica 1567–91.

Weir, G.W., Puffett, W.P., Dodson, C.L., 1961. Collapse structures in soern Spanish Valley, southeastern Utah. United States Geological SuProfessional Paper 424B, B173–B175.

Wenrich, K.J., 1985. Mineralization of breccia pipes in northern ArizonaEcon. Geol. 80, 1722–1735.

ancient wet aeolian environments on earth: clues to presence of fossil/live microorganisms on mars

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