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M2020CandidateLandingSiteDataSheets MelasChasma

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Melas ChasmaLocation(lat,lon):

9°48’N,283°30’E

Summaryofobservationsandinterpretedhistory,includingunknowns:

LocatedonthemarginsofVallesMarineris,MelasChasmaisanenclosedbasincontainingdiverserockformationsandmineralsformedinmultipleaqueouspaleoenvironmentsoverasustainedperiod.Timingof lacustrineactivity iswidelyagreedtohavebeenLateHesperianoryounger.Materialserodedfromeastern andwestern ends of the basin formed a diverse array of subaqueous sedimentary deposits,including11fans.Thesesedimentsweredepositedinlakesasdeepas400mduringasmanyasthreedifferentlacustrineepisodesinthebasin.Periodsofsubaerialexposureareindicatedbymegaripplesinadistinctivestratigraphicmarkerbedofprobableeolianorigin.AvarietyofmineralsoccurintheMelasregion,andincludesCa-sulfates,Fe-sulfates(jarosite),Fe/Mg-smectitesand/orAlsmectites(outsidethebasin),opalinesilica,andpossibleotherhydratedminerals.

TheinterpretationofgeologichistoryatMelasisbasedonarobustassemblageofobservationsincludinglandforms, mineralogy, stratigraphy, depositional architecture, field relationships and bedforms. Aplethora of aqueous landforms includes thewell-studied lacustrine assemblagewith eleven differentsubaqueousfans,atleasttwoofwhichweredepositedindeepwater.Therearealsolayeredlacustrinebeds-aninterpretationevidencedbytheiroccurrencebelowthelakerimelevationasdeterminedfromfanelevation).Roughagreementinvolumeestimatesoftheerodedmaterialfromtheeasternwatershedandthelayeredbedsinthebasinindicatesthebedscomprisereworkedmaterialtransportedfromtheinciseduplandvalleys(asopposedtoairfalldust/eoliantransport).

Potentialforfundamentalscientificdiscoveries:Withdifferentsedimentarymaterialsbeingsuppliedfromdrainage/erosion from eastern and western source areas, and then being deposited in such diverseenvironments, therewould havebeen a variety of potential habitats andpathways for recording theevolving basin chemistry, sedimentary processes, weathering processes, evolving atmosphere andclimate,andpotentiallyamicrobialbiosphere.ThedepositswithinSWMelasareexhumedandthedeepsubaqueous fan deposits (ROI 1) are an erosionalwindow into the strata, indicating protection fromharmfulirradiation.Thisattributeisamajorcontrastfromotherdeltaicsitesunderconsideration,whichdonotappeartohavebeenformerlyburied.

KeyUnknowns:Presence/amountofigneousrock.Alandslidefromthesouthmayhaveprovidedsomeigneous rock from thewalls of VallesMarineris although it is unclearwhether or howmuch igneousmaterialisintheellipse.

Land-on science: The ellipse is entirely made up of materials of interest. Layered deposits, inferredlacustrinedepositsarepervasiveinlandingzoneandwouldbesampledinanytraverse.Therefore,thesewere not designated a separate ROI. The landing ellipse includes layered deposits believed to beemplaced inshallowtodeepwaterconditions, reflectingarangeofhabitableenvironments.Geologic


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context is clearly visible from orbit. Outcrop exposure is excellent. Superposition relationships existbetweenmultiplelayereddepositsandfanswithinthebasin,whichcanbeusedtobetterconstrainthesequenceofeventsthatshapedthisregion.

Summaryofkeyinvestigations

- Assesswaterdepthvariations.Identifyshallowanddeepwaterdeposits,episodes/areasofsubaerialexposure.Evaluatediagenetichistory.

-Lookforauthigenicminerals,chemicalsediments:possiblesitesforchemical,mineralogical,organic,micromorphological,macromorphological,isotopicbiosignatures.

-Lookforquietwaterconditions.

-Determinemineralogyanddepositionalenvironmentofthelacustrinesediments.

- Determineoriginandenvironmentofformationoftheopalinesilicaandsulfate-bearingoutcrops

CognizantIndividuals/Advocates:

BeckyWilliams,PSI

LinktoJMARSsessionfile|LinktoWorkshop2rubricsummary

https://docs.google.com/spreadsheets/d/16Rmn2qHFQc6BKJtiyIeDLcyBxJqq8Oq4VO3etqrZ8lo/edit?invite=CNm8lqYF&pref=2&pli=1#gid=868597987

KeyPublicationslist:

Dromart,G.etal.,2007.StratigraphicarchitecturesspottedinsouthernMelasChasma,VallesMarineris,Mars.Geology35,363–366.http://dx.doi.org/10.1130/G23350A.1.

Liu,Y.,andJ.G.Catalano,2016.xIcarus,271,283-291.Mangold,N.etal.,2004.EvidenceforprecipitationonMarsfromdendriticvalleysintheVallesMarinerisarea.Science305,78–81.http://dx.doi.org/10.1126/science.1097549.

Metz,J.M.etal.,2009.SublacustrinedepositionalfansinsouthwestMelasChasma.J.Geophys.Res.114,E10002.http://dx.doi.org/10.1029/2009JE003365.


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Quantin,C.etal.,2005.FluvialandlacustrineactivityonlayereddepositsinMelasChasma,VallesMarineris,Mars.J.Geophys.Res.110,E12S19.http://dx.doi.org/10.1029/2005JE002440.

Weitz,C.M.,NoeDobrea,E.,Wray,J.J.,2015.MixturesofclaysandsulfateswithindepositsinwesternMelasChasma.Icarus252,291–314.doi:http://dx.doi.org/10.1016/j.icarus.2014.04.009

Williams,R.M.E.,Weitz,C.M.,2014.ReconstructingtheaqueoushistorywithinthesouthwesternMelasbasin, Mars: Clues from stratigraphic and morphometric analyses of fans. Icarus 242, 19–37.http://dx.doi.org/10.1016/j.icarus.2014.06.030

RegionalContextFigure(Williams&Weitz,2014)


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EllipseROIMaporGeologicMapFigure(Williams2ndlandingsiteworkshop)

Layereddeposits,inferredlacustrinedepositsarepervasiveinlandingzoneandwouldbesampledinanytraverse.Therefore,thesewerenotdesignatedaseparateROI.


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Mappedunitsandmineralogicalobservations


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Regional(~3xellipse)StratigraphicColumnFigure(Metzetal,2009)

Sketchofthepaleolakedepositswithanupperfanfeedbythevalleynetworkupstream,andlowerfansformedbysubaqueouschanneldeposits.

InferredTimelineFigure


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SummaryofTop3-5Units/ROIs

ROI AqueousorIgneous?

Environmentalsettingsforbiosignaturepreservation

Aqueousgeochemicalenvironmentsindicatedbymineralassemblagesorotherevidence

1 Aqueous Deepsubaqueousfanforpreservingbiosignaturesviaclasticdepositionand/orchemicalsedimentation

Deepwaterfanisindicatedbylandforms,stratigraphicarchitecture,fieldrelationships

2 Aqueous Hydrothermal,chemicalsedimentaryordiageneticalteration

Hydratedsilicacouldindicateanyofthoseenvironments

3 Aqueous Layeredlacustrinedeposits Opalinesilica;nearbyjarosite

4 Igneous? Landslidefront Nomineralogy,likelyigneousfloatrocksfromthewallsofVM

Top3-5Units/ROIsDetailedDescriptionsUnit/ROIName:Lakebeds

Aqueous

Description:

Horizontallayereddepositsthatareabundantintheellipse

Interpretation(s):

● Layersinterpretedaslacustrinebecausetheyareallbelowthepaleolakeleveltracedbyfansandclinoforms

InSituInvestigations:

● mapup-sectionandlateralvariationsintexture,bedforms,chemistry,mineralogy,organics.● Studycontacts:Channels?anysignsofsubaerialexposure?Couldprovideinsightstoancientatmosphericcompositionetc.Howdidtheenvironmentabove/belowcontactchange?Thiscouldprovideinsighttoevolutionofsurfaceprocesses,climateandhabitability.

● PetrologywithPIXL,SHERLOC,SUPERCAM:clastics–composition,shape,alterationrims,cements,matrixetc–forprovenancestudies,evolutionofwaterchemistry,waterdepth,waveenergy,sedimentationrate,benthicprocessesetc.overtime


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● Lookforpossiblemicrobialtexturesandtexturalvariations● Lookforpossiblemicrobialstructures(stromatolites,bioherms,reefs),organics.● Lookformaterialsthatcouldprovideinsightstotheprocessesaffectingisotopefractionation(e.g.crusts,interstitialcements)

● Lookforunusualdistiributionsofelementsofmineralsthatcouldreflectmicrobialactivity● Lookforprecipitatedmineraldepositsthatmaypreservemicrofossils,organics,gasorfluidinclusions,isotopicproxiesforpaleoenvironment,atmosphereandclimate

● Lookforveinstocompareandcontrastwithsedimentarymaterialsandprovideexperimentalcontrolsonanalysesinsituorreturnedsamples

● Lookforigneousclastsorashdeposits,spherulesorothervolcanic“eventdeposits”forpossiblegeochronologystudies

● Lookforooidsandotheraccretionaryfeaturesfromthesedimentaryenvironment● Lookfororganicsinfineclasticsediments● Lookforpossiblechemicalbioisignaturessuchasreductionspots● Lookforalterationfeaturesandcomparethoserelatedtomodernweatheringtoalterationcausedbypaleosurfaceprocessesorburialdiageneticprocesses.

● RIMFAX:mapsubsurfacelayers,includingspatialchanges.Searchforsubsurfaceboundarybetweenproposedlakelayersandbasalterraintoassessthickness,mapcontactsbetweenotherunitsincluding,ifpossible,spatialchangesinthickness.Searchforburiedchannels.

ReturnedSampleAnalyses:

● Analyzeawellcharacterizedsuiteofsamplesrepresentingthekeyfaciesandmicrofacies.Continuetheinvestigationsasoutlinedabove,butatsmallerscalesandwithdifferenttechniques.

● Studyanyauthigenicminerals–dotheypreservemicrofossils,organics,gasorfluidinclusions?Analyzethese,measureisotopiccompositionsetc–yieldproxiesforpaleoenvironment,atmosphereandclimate

● Finescale(egsynchrotronXRF/XRD,TEM,SIMS,nanoSIMS)analysisofanyorganicstocharacterizemorphology,chemistry,isotopiccomposition,mineralassociation,assemblagecharacteristics.

● Geochronologystudiesofmineralgrains(authigenic,volcanic,clastic)● Provenancestudiesofgrains● Lookforpossiblebiominerals● Lookforpossiblechemicalbiosignaturessuchasreductionspots


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Unit/ROIName:Subaqueouschanneldeposits

Aqueous

Description:Digitatedfanspresentonthewesternmarginbelowthepaleolakelevel

Interpretation(s):

● Subaqueouschannelsandfans,asdeterminedfromtheirmorphologysimilartoterrestrialsubaqueousfans

● InSituInvestigations:

● InadditiontoinvestigationsoutlinedforROI1,alsoobservechannelandoverbankdepositsfordetailedinsightstothesedimentaryenvironment,includinganychangesthatwouldberelevantforhabitability(e.g.sedimentationrate,type)andpreservation.Lookforshallowwaterpartsorsedimentsdepositedinlowenergyenvironment:thesewouldprovideideallociforbenthicorganisms.Lookforpossiblemicrobialsedimentarytextures,structures,authigenicmineraldeposits(rationaleasabove)


Asabove


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Unit/ROIName:Opalinesilicaoutcrops

Description:

Locallayeredoutcropsthatpresentopalinesilicasignature

Interpretation(s):

● Specificalterationwithauthigenicsilica,locationtounderstandbetterthelacustrineenvironment


● Determinetheoriginofthesiliceousdeposits:● Studymineralogyindetail:what,ifanything,isthesilicamixedwith?Isitdepositedinlayersormassive?Whattexturesandfabricsdoesitexhibit?Howdotheyvary?Whatisthenatureofthecontactwithadjacentrockunits?

● Identifyfaciesandmicrofacies.Mapcontactsandspatialvariationsinfacies.● Lookformicrocrystallineoccurrences–possiblepreservationsiteforcellularstructures.● Searchfororganics● RIMFAX:Mapstratigraphicrelationshipofthesedepositstootherunits,aswellasinternallayeringwithinthedeposit.


● Microtexture – insights to origin of silica● Entrained organics – any microfossils● Gasorfluidinclusionsstudiesetc


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Unit/ROIName:Landslidemargin

Description:Landslidetongueatthesouthernmarginoftheellipse

Interpretation(s):

● IgneousrockfromVallesMarineriswallsmaybeaccessibleforexplorationandsamplinginthislandslide


● Studythecompositionofbouldersinthelandslide–especiallyforvariationsinigneousbouldercharacteristics(grainsize,mineralogy,chemistry,alteration),toinformsampleselection

● RIMFAX:Ifpossible,mapbasalboundaryoflandslideandinternalstructure.Mapcontactbetweenthisandsurroundingdeposits.


● Age dating of igneous rocks


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Biosignatures(M2020ObjectiveBandObjectiveC+e2e-iSAGType1A,1Bsamples)

BiosignatureCategory

InferredLocationatSite Biosig.Formation&PreservationPotential

Organicmaterials Quietwater(e.g.finegrained,finelylayered)deeporshallowlacustrinedepositsinanyofthefansorlayeredlacustrineunitscouldcontaineithertransportedorganicsthathavebeenhydraulicallysorted,pelagicorganics,orinsituorganicsformedatbenthicboundarylayer

Formation:Transportedorganicsthathavebeenhydraulicallysortedmaybedepositedindeepwater.Abundancedependsonproductivityinsourceregion.Pelagicorganics:BenthicorganicsPreservationrequiresburialandabsenceofoxidizingdiageneticprocessesetc.

Chemical Anywhereinthelacustrinedepositsoropalinesiica–texture-specificchemistrycanrevealavariaetyofpotentialcluestopastmicrobialactivityinavarietyofsubaqueousfaciesthatwouldoccuratthesite

High

Isotopic Authigenicmineralsand/ororganicsinthelacustrinedeposits.

High

Mineralogical Authigenicmineralsinlacustrinedeposits,silicadeposits

High

Micro-morphological Authigenicmineralsinlacustrinedeposits,opalinesilica,chemicalsediments,anyevaporativesedimentaryadeposits.Alsopossibleendolithicmicroboringsinclasticsinlacustrinedeposits

High

Macro-morphological Lacustrinedeposits High


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DateableUnit(s)forCrateringChronologyEstablishmentUnitName Total

Area(km2)

TimePeriod

GeologicInterpretationanduncertainties

Whatconstraintswouldtheunitprovideoncraterchronology?

KeyUncertainties/UnknownsabouttheSiteNoigneousunitswithwell-establishedcraterdensity

Durationoflacustrinedeposition.

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