1989LPSC...19..397Z ground Squyres, martian from Sbatp, propose example connection described a appearance to features, examine of observed distinctive temperature (Squyres, images landfonns. 1979; is is theoretical must resolution resolution images 10 volatile-related Since Ground best particularly a m/pixel near-surface volatile-related Center the be 1973; Luccbitta, of assessed cover ice landfonns the © both 1978, of many an Mars 1979; presence considered landform. (Zimbelman, ice within The as <20 analyses a Lunar with of for ( resolution arrival Carr e.g., landform alternative theoretical and can a <1 many of with 1979; important Concentric Earth development m/pixel at of creep undulations concentric are concentric deformation locations the that multiple-layer Squyres with concentric materials ground % origin, which Sbatp et 1979; Concentric significantly shear ground craters have latitudes of of also of moderate Utopia origin of was a/,., of and Squyres and INTRODUCI10N at images the whose the may in Mariner these ground exposed 1987). 1976, midlatitudes are at (Zimbelman, et in been and ice Prey and around hypothesis Planetary since stress Lunar stability any ice crater Planetary Planitia crater least martian for given al., confined no poleward be between throughout often observational been pattern crater and or deposit. features to morphology limit that Can; 1977; attributed et enhance concentric evaluation There instance regional totally in 1971; 6 fill diagnostic ice Proceedings and modification high Mars, fill within region. the Can; al., quite appropriate and Crater and positively the material show fill, Studies, ( within su.rfuce, material 1986). is Planetary e.g., Carr plains of quality for Layering are of suggesting Anderson is invisible applicability 30° a its 1979;). 1988); in mobility 7 concentric 1986; small. Institute the ±30°, We has distinctive Squyres indeed the surface the almost extent. Copyright in to thickness, of the and a is is constraints material crater of and features National Air S. in the crater In most propose downslope that they thought Ice-rich an established. 1969, the of most soil. Mouginis-Mark, Fill should where M. volatile-related the For Institute although origin Schaber, 19th this conditions Although at of that and Carr, Mantling unambiguous 3000 any 60° suggestive have et consistent presence 1989, fill, undulations represent Clifford of rim, Utopia martian surrounding 50 ground Mars, Lunar crater as Therefore numerous diagnostic al., paper visible that deposition on J. an landform • to concentric not latitude relevant m/pixel a and envisioned of Orbiter Lunar has R. spatial 3303 Provided ice-rich and result creep and 1977; 1973; an these· layers scale 1986). Planitia be One this Mars: landfonn been the Zimbelman fill, with we we Mass ice and aeolian of of of Planetary at and Space a NASA preserved the are Planetary occurred morphologic soil intetpreted Theoretical crater region in view. followed critical fill In fill su.rfuce surface crater, ice-enhanced interpreted in indicator interpretation lobes The is is to midlatitude the the moderate-resolution high Utopia between (Fig. enhanced of of craters, S. observed Road Museum, intetpretation assumed a represented Concentric the the in concentric Wasting Science high-resolution morphology. some An be ( H. by necessary details e.g., concentric morphologic Institute, effectively resolution 1) fill We if ice-enhanced (45°N, of concentric Williams common on One, and Planitia indicating source the modification the material Vtking and Conference, Aeolian is material as in groups the constraints use of and a by creep Smithsonian to must isolated observed. an high-resolution to global Houston, craters crater Houston the NASA 271°W) by at both creep theoretical have prerequisite crater crater additional of for example crater represent mobilizing region of frame is pattern other a a within be nor the presence are of crater the information recurrent that scale pp. concentric fill clearly images creep acted moderate characteristics on lead ( lobes considered fill data fill ridges images Squyres, High-resolution 397-407 the origin to TX show not material fill Astrophysics (approximately 196503; the midlatitude BACKGROUND Alternative of have Institution, and constraints. fill of material Neither craters the model 77058-4399 partially upon us downslope evidence in morphologic ice-enhanced images important, within was many stability to specific of depositional surface it material and was are order to leads moved prominent pattern and the to ground 1988 moved for Squyres, the first believe modification Multiple in not be taken in ridges of the origin some high-resolution and completed and us morphologic to deposits the Washington, many undulations locations an ). to the of movement that images limited (Fig. of toward theoretical identified it to preserve The by mobility 45°N, regolith the process ice eroded, this context surface to concentric features and that is midlatitude of 1988). Utopia favor layers Data features other slow distinctive 2). also sharp represent all by rounded to to but of of one grooves a the 270°W) The concentric concentric (Squyres, an Squyres volatile-rich a recognized Aeolian only of were DC System as Planitia in studies. analysis break more location center aeolian derived images cuspate the and 20560 a craters crater crater as are individual layers observed potential to available in regional ( a etching around 1979). 1979). region visible of of While minor crater crater origin of assess slope from form Our that ice- rim soil the fill, the are of 397 1989LPSC...19..397Z 398 Viking Fig. ridges example at indicate fill Fig. (Squyres, several evidence Planitia NGF-ortho © 41.5°N, material Lunar 2. 1. Proceedings frame and grooves the The High-resolution Concentric of of 1988). 272.4°W. version, grooves and concentric location flow 10B70, crater and the separated Note of of 16 crater of interior within crater material NGF-ortho Planetary the ID/pixel, the images crater view 19th rim subtle by fill the contains of toward Lunar fill in rounded (arrows). in centered concentric version, large Figs. rim-lacing (Squyres, Utopia Institute and the 2 a crater (bottom) at ridges, concentric Viking Planetary 97 Planitia center 41.7°N, crater saup 1979). ID/pixel, are frame interpreted of 1he between and fill cited • 272.4°W. Science The pattern the in centered Provided 425B07, 6 circular Utopia (top). boxes crater as Conference the an of as - process landforms is mantle walls, relatively features convex around lobate Deuteronilus the materials narrow possible degradation of are indicate Lobate 280° While morphologies recognized particulates presence preferentially (Squyres evidence and/ disposed 1986). modulation the ±30° ±30° number by Guest concentric of images that underestimated believe is equilibrium a distribution is 1981, 1973 temperature the Concentric The cited The ice-free, behavior interpreted the the the occurrence landforms related or history this ). to latitude, latitude characteristic et p. absence points draped possibility debris the Degradation debris blanketing preservation valleys demonstrated that as accumulations obstacles 350°W), of volatile-related of NASA al., 79). material that away the of that about and whose steep a crater evidence 4- during and importance attributed ice-enhanced with of on of regionally ( conclusion transfer 1977; there degrades of Mensae as Squyres debris (Soderblom to An presence leading crater as raised aprons, attributed flows THEORETICAL uniformly surface resulting from Carr, are of various of well. the associated in the ground escarpments, an fill appearance IO-km-diameter the Astrophysics debris investigation may of concentric concentric process Mutch the that is of indication the found landform. of mantles supporting surface the of here are fill polar latitudinal function atmosphere and to 1986). and morphologic concentric fine that to topographic relief extensive contribute Mariner "lineated of origin northern that aeolian of in aprons indicate the degradation of over escarpment to occurs ice perhaps the et Carr, et creep. may Nilosyrtis surface with erosional has undulations atmospheric atmospheric to regions, a the is al., interpretation have called detail have al., crater crater While given the higher of that debris CONSTRAINTS consistent of of occasionally 9 be be 1986). been are creep materials variations presence 1977), the debris valley 1973). in craters concentric played (Fanale, midlatitude Lobate mission to crater also terrain the movement an detail the the applicable detail Data "terrain visible fill abundant confined evidence fill conjunction presence extending a Mensae the this (Squ~ debris viscosity of questioned mantle image effects and been is regolith fill" at regolith most mantles but parallel Viking (Kahn were an fill, haze observed development textural with haze ( and debris of paper equatorial on System ( Squyres that in 1976). against in Soderblom softening" important role important the (Squyres, attributed with crater within ground and at (30° to in compelling. of a the Mars Viking to locations of the symmetrically of interpreted of can poleward these data must 1978). in global full-off et to on poleward the atmospheric support in a discusses these with aprons ground a ( the ice Above this detail, theoretical al., an deposition to e.g., and lineations the fill, to way Mars pervasive alter was relatively provided diffusive latitudes base features ice, decline, Orbiter not aeolian at 1979). 1986). are extent to region of apron in 45°N, et Of valley other other some Carr, Carr, ( first that 60° low and the e.g, the are the the the the ice we al., be all all of In to of of in a 1989LPSC...19..397Z 2 :r: l- a. w with has and S:2 these has :r: between l- (1bon sublimation calculations onset ature, a. is have regolith w properties characteristics depth of thickness E E a Recent If 200 160 120 latitude Fig. (b) calculations 160 200 ice 120 been consequence 80 40 not 80 the Hillel, 40 undergone O increasing 90 the conditions, latitude 90 IO ~======~;::;;;::~======et 3. of recession a near absence © varied b dated the µm al., of theoretical quantity and The 100 80 1983; of Lunar 80 indicate rate the [from the 1980; time latitudes of differed for frozen at depth m desiccation substantially ductile latitude 70 concentric of of of Panak equator 70 some Fanale at the (b.y. of the consistent the Fana/e H concentric that and studies ice of this 2 only 60 O ). soil long-term 60 of appearance loss 3.5 layer LATITUDE, ground The LATITUDE, et lost et is (Fig. only to latitude Planetary ±40° al. to in et (Fana/e sensitively of al., 50 crater and regolith 50 suggest a to from since ( 4 al., as&lllled near-surfuce the 3 1986), depth crater ice with 1986). -100 b.y. ). should the 40 sublimation 1982, fill? 40 the Thus top on 0 constrains of the et models (Wire 0 that Fig. of the observed m fill al., Mars regolith dependent concentric pore 100 30 However, fonnation 30 Institute 300-500 1986), 5 have at But equatorward the 1986). ]. et known ice, adopted m as 30° size: al., 20 20 is martian a of desiccated of then the should a ----2.7 an function latitude morphologic 1979). -----1.8 regolith (a) because defonnation ( m ground on for 10 crater 10 of rheologic event maximum the • 1 these temper- Clifford decline climate Tharsis of µm, Provided depth Given of 0 0 ( that 0.0 4.5 will 3.6 fill) 30° 0.9 1.8 2.7 0.9 the the the ice !i 0 ;: where ..i 3 3 0 0 i,.. regolith where u .!! ..:,: dominated and The A where equation crystal law < volume) Hooke martian activation of even decrease to (Weertman, appreciable is magnitude and The is 273 The -24.__ -22 -20 -18 -16 -14 for corresponds Fig. magnitude. [from 273 K). relatively by constant, 160 plotted a temperature sand ..---..---,----...---...-----.--- a ice. is 4. K, n is p strain shear et orientation, A,, slight the given a Clifford __ surfuce Zimbelman is is in is The 60 depth the al. has The energy the by significantly greater has The a strain for NASA kJ rates 1973; deviation 180 (1972) by quantity constant which decrease free local ice, Because .,__ temperature to a regolith mo1- ( h a resulting the (160-225 Glenn's 1987), composite a __ rate. below dependence given the value for et than Paterson, change A= of surfuce and 1 that temperature is al.: for have in Astrophysics strain 200 r=pghsina of Fig. with creep contaminants. a density, in ..__ less A,, of the by TEMPERATURE for law the Concentric T impurity function of this variation drives dependence temperature __ exp(-Q/RT) 9). in shown < K) entrained equation curve ductile. slope. viscosity ice surfuce a -4.3 rate 263 the strong 1981; (139 value of and g 2 240 220 alone, _.__ at the e is activation A range K), X that of crater content that Given in temperatures __ the laboratory the is kJ is Clifford, of temperature ( temperature, of 10- defonnation ( and A 2) given given particulates a T/) an Ice moJ- results the results (K) acceleration -3, Data regolith fill covers that 4 50/50 apply _.__ R s- a effect that fl.ow energy on (Paterson, by 1 that and is 1 regolith __ by characterizes 1987). kPa- Mars the for from in experiments only System above law is some mixture the A at that contains dependence, a for gas an 260 ....._ 3 crystal 263 is constant of , depth substantial to Arrhenius of this (>5% 263 In Q rheology becomes __ the creep order 9 constant ice-rich ice gravity, K 1981). orciers is Fig. of shear K flow size, that < (2) (1) (up (3) the the 280 ice ... _, by an by of 4, 399 T
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( ( magnitude magnitude dependence dependence dependence dependence 4). 4). significant significant creep. creep. would would 45° 45° in in >100 >100 for for Given Given greatest. greatest. -10 -10 crater crater fill. fill. layer layer latitudes latitudes rate rate is is This This 10- 100m 100m pressure pressure ice-enhanced ice-enhanced and and hypothesis field field 45° 45° At At Om Om regolith regolith fill. fill. increase increase even even all all driving driving latitude latitude obliquity obliquity Data Data 17 17 are are fill fill 60° 60° it it K K is is m, m, and and thickness thickness ( ( decrease decrease are are But But most most the the otherwise otherwise but but s- -x10· suggests suggests fill fill =0% =0% studies studies an an of of 1 (The (The more more This This where where examples examples too too latitude latitude ) ) more more modification modification the the negligible). negligible). shear shear how how power power temperature temperature come come order order the the to to the the at at System System is is deformation deformation of of of of readily readily the the ( ( the the 1 small small support support fact fact •= •= ...... predicted predicted cycle cycle ) ) this this observed) observed) pronounced pronounced steepest steepest sensitive sensitive corresponding corresponding creep creep is is the the strain: strain: the the that that by by morphologic morphologic both both strain strain complicated. complicated. of of between between -- into into of of the the be be approximate approximate (the (the law law due due 1=m 1=m would would ~~~~---···· ~~~~---···· a a latitude latitude magnitude magnitude where where to to in in terrestrial terrestrial flow flow flow flow expected expected the the expected expected causes causes factor factor (a) (a) play. play. geother- on on Because Because a a depend- entirely entirely explain explain highest highest rate rate Utopia Utopia results results of of creep- slopes slopes =1000% =1000% is is strain strain strain strain seem seem 0%, 0%, Mars Mars by by ...... law law law law this this For For the the the the the the the the by by at at . . of of is is a a a a 1989LPSC...19..397Z factors factors parameters parameters Fanale Fanale appears appears which which where where is is that that porosity porosity likely likely Hille4 Hille4 studies studies resolved resolved atmosphere), atmosphere), However, However, currently currently n n tion tion equation equation of of the the any any the the self-compaction self-compaction ground ground immediately immediately effect effect underestimated, underestimated, regolith, regolith, n n overestimate overestimate considered considered depth depth tion tion not not origin origin the the be be estimates estimates ad ad the the assumed assumed of of depth depth Instead, Instead, ( ( should should concentric concentric deformation deformation 1982; 1982; enhanced enhanced a a the the 200-300 200-300 1988) 1988) factor factor has has If If However, However, The The may may The The that that found found n n hoc hoc shear shear past past other other physical physical regolith regolith regolith regolith include include of of the the appearence appearence of of described described will will pore pore Durham Durham that that will will a a of of has has of of >.. >.. ice ice above above as as et et lie lie 1983). 1983). the the most most of of survive survive ice ice the the assumption assumption several several of of to to of of desiccation desiccation © © he he is is by by notes notes value value within within here. here. (2), (2), the the m, m, al. al. of of igneous igneous equatorial equatorial concentric concentric alternatives alternatives significantly significantly some some by by terrestrial terrestrial is is believed believed closer closer gas gas 10-30. 10-30. been been give give lie lie has has 50% 50% the the such such appear appear rheologic rheologic crater crater in in Lunar Lunar deformation deformation the the if if increasing increasing ( ( best best possesses: possesses: suggests suggests apparent; apparent; properties properties the the as as at at stability stability the the invoking invoking rigorous rigorous argument argument desiccation desiccation 1986) 1986) thus thus flux flux or or in in the the this this been been Therefore, Therefore, Indeed, Indeed, ~ ~ decades, decades, to to rise rise extent extent of of of of and and et et that that 10° 10° a a this this by by the the recent recent and and underestimated, underestimated, processes processes 10 10 potential potential the the described described to to regolith's regolith's reconsolidation, reconsolidation, of of (2) (2) However, However, fill, fill, within within objections objections the the single single reasonable, reasonable, ( ( al., al., analysis analysis ~3 ~3 strengthening strengthening Jails Jails Gifford Gifford -20° -20° to to uniform uniform µm µm that that equation equation depth depth 4. 4. are are desiccation desiccation two two {with {with glaciers glaciers and and value value concentric concentric depth depth for for crater crater exist? exist? strain strain behavior behavior that that a a regolith regolith calculations calculations then then it it a a of of increase increase a a (Weertman, (Weertman, 1983), 1983), The The analysis analysis ( ( the the laboratory laboratory of of assumes assumes if if most most mean mean numerous numerous deeper deeper to to 1) 1) of of specific specific diffusive diffusive is is of of equatorial equatorial of of most most masmve masmve 10°-20° 10°-20° depths depths shear shear how how the the anything, anything, of of Planetary Planetary diffusion-inhibiting diffusion-inhibiting Fanale Fanale clear, clear, of of near-surface near-surface ( ( have have by by explain explain thickness thickness a a gaseous gaseous the the ice ice an an evidence evidence Perhaps Perhaps while while source source and and <100 <100 is is fill. fill. pore pore rate rate have have to to likely likely the the more more ( ( the the free free given given a a now now with with martian martian plausible plausible 2). 2). responsible responsible of of confident confident equator equator effective effective of of {E {E the the power power zone zone creep creep Hille4 Hille4 are are On On that that stresses stresses had had however, however, surface surface surface surface predicted predicted then then equatorial equatorial the the will will crater crater flow flow sizes sizes duricrust duricrust homogeneous homogeneous the the indicated indicated kPa), kPa), frozen frozen et et ex: ex: laboratory laboratory path path experiments experiments the the maximum maximum of of The The indicate indicate ice ice of of the the depth. depth. open open our our suggest suggest permeability-for permeability-for strain strain the the correct. correct. al. al. the the 1973; 1973; rn) rn) this this current current of of of of on on case case of of conditions conditions the the this this cannot cannot 1983). 1983). be be depletion depletion the the of of law law law law regolith regolith as as stability stability ( ( of of 30° 30° deformation deformation a a current current most most Institute Institute explanations explanations deformation, deformation, this this the the greatest greatest flux flux 1986), 1986), other other may may fill. fill. the the ground ground area area pore pore pore pore are are 1 1 well. well. power power model model as as equator equator H Given Given higher higher for for rates rates that that discrepancy discrepancy relationship relationship appropriate appropriate aponent, aponent, formation, formation, Paterson, Paterson, and and for for 2 that that regolith regolith onset onset by by that that that that ductile ductile O O experiments experiments landform landform However, However, values. values. greater greater estimates estimates we we lithology lithology small small likely likely At At well well be be effects effects a a structure structure ~10 hand, hand, a a in in the the ( ( Uones, Uones, radius radius the the who who 10 10 knowledge knowledge of of predicted predicted creep-related creep-related the the for for are are layer layer Giffard Giffard the the the the higher higher law law satisfuctorily satisfuctorily that that differs differs a a is is ground ground uncertainty uncertainty the the latitude latitude than than {Fig. {Fig. be be µm µm possibility possibility 3 3 equatorial equatorial model model depth depth creep creep as as accurate? accurate? origin origin has has layer, layer, deforma- probable probable likely likely modeled modeled • • than than value value is is descrip- are are Squyres Squyres such such of of n. n. m martian martian and and current current it it invalid invalid with with 1981). 1981). should should where where of of is is of of values values r>>>.., r>>>.., These These if if Provided Provided those those 2 2 1978, 1978, more more those those value value 3). 3). Over Over from from been been such such does does than than and and that that and and this this g- any any not not the the the the the the are are ice ice for for do do by by an an to to of of of of of of of of of of If If 1 a a , , flowed flowed processes processes flows flows with with and and presence presence crater, crater, crater crater in in for for without without along along necessarily necessarily material material in in rim-facing rim-facing consequence consequence even even Table Table outward outward could could ice-enhanced ice-enhanced morphologic morphologic ric ric identified identified possessing possessing similarity similarity interpreted interpreted resulting resulting evolution evolution lobate lobate No No result result direction direction crater crater material material creep creep (Easterbrook, (Easterbrook, enhanced enhanced results results (Squyres, (Squyres, implicitly implicitly break break of of certainly certainly likely likely argument argument able able concentric concentric necessarily necessarily the the outside outside rim rim Arguments Arguments A A Some Some the the slope slope ice. ice. crater crater by by creep creep has has features features Carr, Carr, material material morphologic morphologic only only other other precisely precisely described described origin origin and and sharp sharp 1, 1, the the fill fill in in of of rim, rim, material material However, However, debris debris a a from from the the a a of of additional additional away. away. subsequent subsequent Zimbelman Zimbelman diminishing diminishing is is is is {Fig. {Fig. compression, compression, slope slope very very fill fill include include from from intriguing, intriguing, if if strain strain comparable comparable of of of of creep creep in in However, However, 1986). that that of of more more assume assume scarp scarp are are The The by by proposed proposed 1978), 1978), the the difficult difficult "classic" "classic" smooth smooth slightly slightly imply imply for for that that features features crater crater for for owes owes NASA NASA to to movement movement compressional compressional breaks breaks appearance appearance creep, creep, topographic topographic expression expression unambiguously unambiguously the the in in smooth, smooth, MORPHOLOGIC MORPHOLOGIC has has the the primarily primarily 1969, 1969, 2). 2). aprons aprons crater. crater. between between the the of of While While origin origin mimic mimic on on concentric concentric if if has has the the by by be be bordering bordering shallow shallow rates rates favor favor ( ( no no have have deformation deformation its its material material study study No No surface surface comments comments a a 1) 1) assumption assumption but but a a moved moved higher higher movement movement the the et et to to out out fill fill Newtonian Newtonian yet yet drifting drifting but but concentric concentric transitional transitional volatile-related volatile-related diagnostic diagnostic evm evm p. p. feature feature crater crater correlation correlation origin origin volatile-related volatile-related al.: al.: but but in in the the Astrophysics Astrophysics This This assess assess of of the the rounded rounded evidence evidence the the they they and and of of quantity quantity will will sloping sloping been been such such 3). 3). (Squyres, (Squyres, the the it it operated operated based based the the ( ( Concentric Concentric slope. slope. attempts attempts concentric concentric is is slopes slopes Squyres, Squyres, coincident coincident between between an an preexisting preexisting is is coincidence coincidence further further than than features features crater crater break break the the and would would and if if stresses stresses A A flowed flowed creep, creep, to to present present would would ( ( or or be be not not rim rim ridges ridges profile profile may may ( ( identified identified unambiguously unambiguously 3) 3) a a ice-related ice-related the the can can e.g., e.g., diagnostic diagnostic unique unique ice-enhanced ice-enhanced was was upon upon change change remobilization, remobilization, that that crater crater flow flow crater crater appearance appearance of of of of the the crater crater CONSTRAINTS CONSTRAINTS would would the the smaller smaller the the of of If If of of the the sedimentation sedimentation in in between between fill fill in in be be the the not not Fig. Fig. to to a a crater crater provide provide 1988). 1988). the the 1988). 1988). the the enhanced enhanced flow flow the the at at toward toward transverse transverse concentric concentric by by it it landforms, landforms, only only rim rim at at an an slope slope particular particular origin. origin. have have of of occurrence occurrence crater crater in in identification identification materials materials ( ( made made a a origin origin describe describe topography topography where where fill fill possibility possibility interpretation interpretation rim rim 2). 2). fill fill is is in in convex convex a a or or be be physical physical crater crater material material aeolian aeolian be be in in Data Data concentric concentric lend lend the the break break fill fill material material origin origin than than plausible plausible is is point point indicates indicates topography topography yet yet of of surprising surprising If If {Fig. {Fig. is is The The must must concerning concerning The The near near conducive conducive clear clear location location visible visible but but fill fill on on expected expected debris debris the the creep. creep. The The the the for for diagnostic diagnostic cited cited material material an an i i been been by by support support interior. interior. Mars Mars a a both both those those to to ( ( ex: ex: process process profile profile may may there there System System where where the the in in convex convex crater crater for for 2). 2). is is mantle mantle 2) 2) mantling mantling center center first first ridges ridges and and be be of of lobate lobate evidence evidence during during that that ice-enhanced ice-enhanced the the the the other other r r and and at at the the uniform uniform explanation. explanation. outside outside ). ). as as identified identified that that slope slope of of the the this this The The flows flows concentric concentric origin origin redirected redirected inside inside be be crater crater the the is is does does If If is is presence presence chemical chemical listed listed ( ( evidence evidence concent- preserve preserve point point that that to to inferred inferred surface surface features features and and Squyres Squyres a a fill fill stresses stresses moving moving general general are are to to a a A A feature feature achiev- to to can can so, so, due due the the of of profile profile of of would would points points debris debris crater crater crater crater creep creep break break sharp sharp layer layer have have faint faint is is that that and and and and and and and and and and ice- the the not not the the the the the the the the the the the the no no fill fill fill fill be be to to in in is is a a 401 401 1989LPSC...19..397Z 402 generation convex The morphologic material result been some considerable of consistent crater direct material erosion of structure Utopia be (Squyres, Smooth, (Fig. Arcuate An the many inferred ice-enhanced present plains frame Fig. has shown of that 42.0°N, top 6) interpreted important obstacle © evidence crater (Squyres, of Planitia flow has the should reveals during a dark of Lunar is 6. of of 1988), with scoured compressional 425Bl (see ridges of Proceedings occurred the in frame nearly further from 272.7°W. the lobes ejecta. erosion the Plains characteristic compressional plains F~ is arrow). crater be is of this a its clue fill l, but as 1988). lacking. significantly at and flow obtained ridges texture a and filled evident 1 creep with from slow NGF-ortho northwest A interpretation, a material more the (center and in ejecta to the has surficial high-resolution of Note grooves of this with the volumes Planetary lower the 2. the movement While exposed that on concentric model taken The outside forces The moderate-resolution visible the from crater region of 19th nature ridges, of the and the is of di1ferent version, right; modification degraded, 2-km- 1989LPSC...19..397Z 404 404 gentle gentle presence presence depositional depositional processes processes ( ( material, material, deformation deformation extending extending concentric concentric is is reconcile reconcile layers layers a a surface surface While While the the deposits deposits crater crater Figs. Figs. upper upper Fig. Fig. low low to to e.g., e.g., convex convex Of Of the the the the 7). 7). feature feature albedo albedo centered centered drapes drapes are are Fig. Fig. Crater Crater buried buried ortho ortho 1 1 greatest greatest Squyres, Squyres, © © in in surface surface does does exposure exposure the the layers layers depositional depositional contains contains and and Perhaps Perhaps most most the the Lunar Lunar throughout throughout 9. 9. where where profile profile of of with with version, version, away away crater crater that that ridges ridges C' C' over over Proceedings Proceedings surfuce surfuce not not 7), 7), of of conditions. conditions. material material most most The The throughout throughout at at likely likely layers layers in in of of was was importance importance the the 1978) 1978) 35.2°N, 35.2°N, ice-enhanced ice-enhanced the the appear appear from from it it the the resulted resulted the the no no of of the the does does and and gros.s gros.s evident evident the the 86 86 and and emplaced emplaced A; A; unresolved unresolved likely likely likely likely smooth smooth rim rim layered layered evidence evidence unit unit within within plains plains process process m/pi:xel, m/pi:xel, the the within within low low the the Utopia Utopia sharp sharp but but layering layering of of not not 271.9°W. 271.9°W. stratigraphy stratigraphy of of to to Planetary Planetary drape drape that that the the was was the the in in crater crater a a result result in in be be to to albedo albedo show show layering layering material material crater crater after after plains plains material material crater crater other other 19th 19th corners corners the the sand sand the the centered centered is is of of a a abundant abundant Planitia Planitia such such entire entire creep creep of of subject subject flow flow more more would would either either rim rim crater crater the the from from Lunar Lunar the the topic topic unit unit on on dune dune craters craters is is of of away away fill fill is is (Fig. (Fig. as as feature; feature; surface surface removal removal toward toward within within well-developed well-developed on on the the that that only only thickness thickness resistant resistant B B at at Institute Institute quite quite The The compres&onal compres&onal and and fields fields erosion erosion of of to to (Fig. (Fig. material material the the over over indicate indicate 36.7°N, 36.7°N, concentric concentric from from the the plaihs plaihs Sa). Sa). of of concentric concentric should should associated associated the the Planetary Planetary A, A, appearance appearance the the fullout fullout (in (in a a its its of of the the 8c) 8c) the the eastern eastern consistent consistent partially partially A A crater crater the the to to units units unit unit rim rim conditions conditions of of 279.5°W. 279.5°W. crater crater (Fig.&). (Fig.&). area area interior interior smooth smooth is is lobate lobate is is erosion erosion variations variations involve involve craters craters the the very very • • is is C, C, difficult difficult Science Science of of in in crater crater pattern pattern ( ( margin margin visible. visible. (Fig. (Fig. buried buried crater crater A', A', Provided Provided with with ridges ridges compare compare as as southwestern southwestern deposit deposit aeolian aeolian feature feature with with similar similar of of it it (b) (b) for for of of upper upper slow slow ( ( 8c 8c has has The The Conference Conference and and the the see see the the the the by by example) example) fill fill fill fill Crater Crater Ejecta Ejecta or or to to in in of of of of ). ). a a no no unit unit fill fill large-scale large-scale vent vent determined determined Utopian Utopian extensive extensive probably probably hard hard Ignimbrites Ignimbrites for for patches patches channel channel features features (Luccbitta (Luccbitta lacustrine lacustrine the the units units agent agent needed needed objections objections changes changes scale scale from from 1986; 1986; B' B' by by B B Utopia Utopia The The deposits deposits (arrows). (arrows). indicate indicate has has the the water water the the structures structures a a to to deposition deposition of of elsewhere. elsewhere. concentric concentric 15-km 15-km McGill, McGill, deposition deposition ongm ongm generate generate Planitia. Planitia. in in plains plains to to indicates indicates in in for for deposition, deposition, not not NASA NASA flooding flooding origin origin aeolian aeolian raised raised and and volcaniclastic volcaniclastic the the requirements requirements environmental environmental Viking Viking produce produce et et of of the the crater, crater, with with produce produce vicinity. vicinity. its its and and of of al., al., the the in in (a) (a) 1985), 1985), crater crater of of debris debris by by (Francis (Francis processes processes by by ejecta ejecta frame frame and and the the The The that that the the Astrophysics Astrophysics certainty. certainty. emplaced emplaced size size other other by by 1bree 1bree the the 1986). 1986). the the MANTLING MANTLING erosion, erosion, the the the the erosion erosion Utopia Utopia a a Aeolian Aeolian fill fill debris-laden debris-laden the the Utopian Utopian is is 572A03, 572A03, plains plains other other presence presence and and slurries; slurries; deposit deposit eruptions eruptions and and wind wind similar similar well well to to craters craters and and deposits deposits and and conditions conditions are are wind wind Each Each on on quantity quantity cover cover and and mechanisms. mechanisms. region region Proposed Proposed deposition deposition active. active. was was units units of of preserved preserved activity activity with with Woo4 Woo4 unit unit NGF-ortho NGF-ortho with with of of the the LAYERS LAYERS plains plains further, further, units units exportation exportation is is presumably presumably of of has has (Scott (Scott similar similar B B and and is is Viking Viking large large slurries slurries currently currently Utopian Utopian Data Data layering layering Nor Nor after after wind wind suffers suffers the the needed needed also also 1982) 1982) is is elsewhere elsewhere significant significant Sand Sand the the units units mechanisms mechanisms a a version, version, and and such such observed observed is is unit unit areas areas frame frame size. size. in in simpler simpler unlikely unlikely System System streaks streaks there there (Luccbitta (Luccbitta from from plains plains buried buried lack lack and and streaks streaks caused caused standing standing of of C C to to Tanaka, Tanaka, the the Crater Crater has has slurries slurries 6o8A04, 6o8A04, was was to to debris. debris. 148 148 produce produce there there on on none none of of a a explanation explanation most most drawbacks. drawbacks. and and because because layering. layering. by by the the not not and and removed, removed, source source and and A' A' m/pi:xel, m/pi:xel, Mars Mars by by drainage drainage include include unit unit 1982), 1982), similar similar are are would would is is NGF- water water what what of of et et Large- depth depth likely likely been been small small sand sand on on C. C. the the the the are are al., al., no no or or of of A A 1989LPSC...19..397Z surface of larger in was be by requires required suggests appears distribution compaction of completely circular over aeolian interior type fill than Zimbelman, that the unit been many emplacement morphology l~ erosional 1986; mass-wasting remnants a The Exhumed a inferred. the Viking surface and younger probably several (B), observed while less-prominent by well Hills, emplaced visible topography gross other blanket local unit more have deposit © graben-like substantial that to rather do remnants images developed (B the Lunar The mantle burial/ produce 1988). craters is over stratigraphy of 1988). mass of they not unit unit ), very consistent places and laterally interpretation exposed crater layering that than presence presumably the craters that closely since erosion were (C). (B) topography wasting. 608A erosion as fresh-looking the loading The has outside highs with Two fractures remnant being and the on in undergoes may in Figure continuous The experienced underlying formed with crater the and Fig. of with resemble 1-16 Fig. of observed craters interior of Mars on of Planetary episodes The be merely (after degree the the the an unit 9, caused the surface last 9 a 11 and/ of are eroding in interior and depositional fill older is or layering by (Fig. crater Utopian fill ejecta; larger exhumation. existence (C) Hills, deduced their erosional a is crater those local deposits or the thought by and morphology topography of 572A have layer subsequent an surface (A). deposits by 10). (Fig. the compaction compaction deposition precludes 1988), into than similar visible crater remnants presumably origin. in Institute incomplete example plains occurred fill Elsewhere sufficiently 1-16 presence from 9). Utopia; In are of than to remnants a 10 (A) episode The fill. hence, in valley-and-ridge two ( be each in all (McGill, units km of Williams erosion Most the (Fig. a that the of a It thickn~ flow of of nue by induced that widespread surface of they in to others centripetal lack disruption is a they of in remnants burial case • is is 9). unit unit occur unit thick produce a material regional possible interior origin. Utopia, or remain buried appear similar visible Provided rather crater crater 1985, have One and (C) (B) (B) (B) can the the to of to in Viking frame Fig. undergone undergoing protected smoothnes.s sculpted km north to 59.8°N, 71 1.3°S, by be m/pixel, crater Zimbelman 10. the 728A62, of from 173.1°W. frame ridges Alba 105.6°W (arrow), Examples NASA by regional of centered its downslope 521883, Patera the NGF the remain rim. (c) et interior deposit al.: located stripping (b) crater The rectiliner Viking of Astrophysics indicates at Concentric in SCR 57.6°S, crater In layer mass an southwest frame rim a version, exhumed of version, being region interior that 305.0°W. wasting. an from crater 578001, erodible (arrow) it eroded 18 of is of crater 17 wind deposits fill Hellas, m/pixel, an Data (a) m/pixel, southern NGF-ortho surface in erosional on from (arrow), The erosion. this Mars is that System too atop centered 5-km centered layer, shape Amazonis extensive have remnant. partially version, this Viking crater wind- and not 10- at at 405 C b 1989LPSC...19..397Z 406 best southwestern and centripetal orders concepts. layer( that required Aeronautics 30° correct, D. the rim. authors earlier Planetary Research No. Acknowledgments. Modification 2. 3. 1. Wilhelms, -60°, 679. ice-enhanced interior © is Fig. morphology. Continued At explained 13 The High-resolution appear s) versions less of were m/pixel, Lunar for ~on there the by 11. Institute, Utopia magnitude the However, completely movement and the the Proceedings S. of incompatible temperatures either Utopia of The Squyres, should strain Space following erosion creep of by centered the the craters and creep crater Viking which the under the manuscript. Staff Administration we crater reveal rate eroded images too be model required and of may Planetary martian The emplacement at fill are contract exhibit evidence believe or reasons. SUMMARY the is small frame of K 35.6°N, in uniform characteristic with produce than rim comments V!Siting not operated of Edgett 19th ice-rich this This by concentric to surfu.ce 328A40, necessarily is no. arguable only. Lunar that crater 272.7°W. the the of typical account This work were NASW-4066 layering Scientists more Institute flow by regolith creep concentric and extent If and paper of undergoing by was most in the NGF-ortho the evidence on of of E. crater Planetary removal the burial/ for mutually hypothesis. supported in Theilig, is a both Universities at the helpful creep of appears with the Utopian LPI ridge-and-valley the the fill • crater deformation exhumation latitudes exhumation sides fill Contribution of the amount of Science Provided craters Lunar in exclusive model version, P. while deposits flow craters. National aeolian several revising Spudis, of fill Space Conference the and the on of of in is is Anderson Carr Carr Carr Carr Clifford Clifford Jones Jones Durham Easterbrook Fanale Fanale Francis Fanale Frey by Guest Hills Hooke Kahn Lucchitta Lucchitta J J Second from of of 92, Mars. Cutts lom 232 Geopbys. equatorial geochemical ejecta Masursky temperature: Salvail deformation regolith New R£s., studies.] distribution Mars: pp. of observations Science Res., of containing ice.J Houston 1-18. distribution deposits texture Sci Geopbys. Geopbys. the Sciences, M. LS. H., Mariner M. M. M. the R, S. 9135-9152. S. 670-674. tbe Conj pp. J. E L 82, E York 84, the R P. E J. J. S. J. S. H. by Lowry Glaciol., Implications In J. H., ( W. Guinness H. A, P., H., giant E., B. D. W. B. NASA 1988) Internati.onal ( A, P. Conference ( M. P., L, M. in 4111-4120. R 8097-8113. Viking Third and 1982) surface and Res., 1978) in Salvail H. Permafrost: Geopbys. D. K (1981) Veverka 17th, B., Crumpler K, region ( M., 462 and Butterworth dispersed 6 Duxbury Masursky Viking Res., Res., and ( Dahlin Washington, (1987) Banerdt 1976) the of and 1982) J. ( rate. polygons in ( of Preliminary B. 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