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Is vloeibare water op Mars so 'n groot sprong vergeleke met ys?

Is vloeibare water op Mars so 'n groot sprong vergeleke met ys?


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Ek het gedink ons ​​het bakterieë of ander soorte lewe op Mars gevind.

Nou is dit vloeibare water. Is daar so 'n groot verskil tussen vloeibare water en yswater?


Ons het nog geen lewe gevind, bakterieel of andersins, anders as die aarde nie. Ek dink jy bedoel die verskil tussen vloeibare water en waterys. Hierdie verskil hou verband met die gasvryheid in die lewe. Die lewe van die soort waaraan ons gewoond is, het vloeibare water nodig, selfs al is dit net vasgevangde vog, tensy die lewe tydelik in hangende animasie is. As daar geen vloeibare water op Mars was nie, sou daar wel blyk om geen moontlikheid van voortgaande lewe daar te wees nie.

Dit is belangrik om gasvrye omstandighede te onderskei van lewenslange bewyse. Alhoewel dit 'n gasvrye omgewing is nodig lewenslank is dit nog lank nie 'n bewys van die lewe nie. Die groot struikelblok is om die lewe te begin of om dit êrens anders heen te bring.

Daar is 'n verskeidenheid gasvrye omgewings in die sonnestelsel en op eksoplanete, soos dat sekere lewens van die Aarde (soos ekstremofiele bakterieë) op een of ander manier daar geplaas sou kon word. Maar dit beteken nie dat daar in werklikheid lewe is nie.

Nog 'n belangrike punt, Mars was vroeg in sy geskiedenis gasvryer met liggame van vloeibare water. Wat belangrik is, want al is die begin van die lewe op Mars onder huidige omstandighede onvoorstelbaar, was die vroeë Mars nogal aardagtig en kon dit moontlik lewe begin of ontvang.


Hoe Mars 4 Miljoen Jaar gelede gelyk het

Vandag is Mars 'n koue, woestynwêreld. Vloeibare water kan nie oral op die oppervlak voorkom nie as gevolg van die lae atmosferiese druk en oppervlaktemperatuur, alhoewel daar bewyse is vir aanleiding tot vloeistofvloei wat miskien bestaan ​​uit 'n sanderige oplossing met 'n verlaagde vriespunt. Water onder huidige toestande kan ys wees of direk in dampe sublimeer sonder om in 'n vloeibare fase te bly.

Ongeveer 4 biljoene jare gelede, toe die planeet jonk was, het dit blykbaar 'n dik atmosfeer gehad wat warm genoeg was om oseane van vloeibare water te ondersteun en 'n kritieke bestanddeel vir die lewe.

Die animasie wys hoe die oppervlak van die Rooi Planeet tydens hierdie antieke klimaatsperiode sou kon verskyn, begin met 'n oorrompeling van 'n meer.

& # 8220Daar is kenmerkende dendritiese gestruktureerde kanale wat, net soos op aarde, ooreenstem met die erosie van die oppervlak deur waterstrome. Die binnekant van sommige impakkraters het wasbakke wat daarop dui dat kratermere, met baie wat aansluitkanale toon wat ooreenstem met water wat in en uit die krater vloei, ”het dr. Joseph Grebowsky van die NASA en Goddard Space Flight Centre in Greenbelt, wat die projekwetenskaplike is, verduidelik. NASA se Mars Atmosphere and Volatile Evolution (MAVEN) missie.

“Klein impakkraters is mettertyd verwyder en groter kraters toon voor 3,7 miljard jaar gelede erosie deur water. En sedimentêre gelaagdheid word op valleimure gesien. Daar is minerale op die oppervlak wat slegs in die teenwoordigheid van vloeibare water geproduseer kan word. ”

Daar is beramings gemaak van die hoeveelheid water wat nodig is om hierdie kenmerke te verklaar, wat gelykstaande is aan soveel as 'n planeetwye laag van 1,640 voet diep of meer. As daar vroeër vloeibare oppervlakwater bestaan ​​het, moes die atmosfeer van Mars en # 8217 'n ander klimaat gehad het wat warmer was en 'n druk naby of groter as die huidige aardse atmosferiese druk op die oppervlak.

In die animasie word vinnig bewegende wolke gebruik om die verloop van tyd voor te stel, en die verskuiwing van 'n warm en nat na 'n koue en droë klimaat word getoon namate die video vorder.

Die mere opdroog en vries, terwyl die atmosfeer geleidelik oorgaan van aardagtige blou lug na die stowwerige pienk en bruin kleur wat vandag op Mars gesien word.

Hierdie beeld toon antieke Mars wat vloeibare water op sy oppervlak kan dra. Beeldkrediet: Michael Lentz / NASA Goddard Conceptual Image Lab.

Dit is onbekend of die bewoonbare klimaat lank genoeg geduur het om op Mars te kan opduik.

& # 8220Die enigste direkte bewys vir die lewe vroeg in die geskiedenis van 'n planeet se evolusie is dat dit op aarde is, 'het dr Grebowsky gesê.

& # 8220 Die vroegste bewys vir die aardse lewe is die organiese chemiese struktuur van 'n rots wat op die oppervlak in Groenland voorkom. Die oppervlak is vermoedelik afkomstig van 'n antieke sediment van die seebodem. Die ouderdom van die rots is geskat op 3,8 miljard jaar, 700 miljoen jaar vanaf die Aarde se skepping. Daar is nog geen fossielbewyse van lewe gevind nie. Die oudste beweerde mikrofossiele dateer uit 3,5 miljard jaar gelede. Die bestaan ​​van 'n potensiële lewensversorgende klimaat op Mars het naby hierdie tye geëindig. 'N Vergelyking tussen die twee lewensgeskiedenisse van die planeet moet met omsigtigheid gedoen word as gevolg van die verskillende chemiese samestellings van die oppervlaktes en verskillende vulkaniese en meteoroïede impakgeskiedenisse. Die geskiedenis van die lewe op die een of ander planeet was moontlik ook nie deurlopend nie. Katastrofiese gebeure kon die hele lewe op een slag doodgemaak het, net om weer opnuut te begin. & # 8221

Die animasie word afgesluit met 'n illustrasie van NASA & # 8217; s MAVEN missie in 'n wentelbaan om die huidige Mars.

MAVEN sal ondersoek instel na hoe Mars sy atmosfeer verloor het. Dit word beplan om in November bekendgestel te word en sal in September 2014 by Mars aankom.


Doel-2 Doel 2: Kenmerk die klimaat van Mars

Hierdie beeld, wat data van twee instrumente aan boord van NASA & # 39 s Mars Global Surveyor kombineer, toon 'n wentelbaanuitsig op die noordpoolgebied van Mars. Krediete: NASA / JPL-Caltech / MSS Laai die volledige beeld af & rsaquo

'N Hoogste prioriteit in ons verkenning van Mars is die begrip van die huidige klimaat, hoe dit in die verre verlede was en die oorsake van klimaatsverandering oor tyd.

Hoe lyk die Marsklimaat vandag?

Die huidige Marsklimaat word gereguleer deur seisoenale veranderinge van die koolstofdioksied-yskappe, die beweging van groot hoeveelhede stof deur die atmosfeer en die uitruil van waterdamp tussen die oppervlak en die atmosfeer. Een van die mees dinamiese weerpatrone op Mars is die opwekking van stofstorms wat gewoonlik in die suidelike lente en somer voorkom. Hierdie storms kan groei tot die hele planeet. Om te verstaan ​​hoe hierdie storms ontwikkel en groei, is een doel van toekomstige klimaatstudies.

Wat kan die huidige klimaat op Mars oor die verlede openbaar?

'N Beter begrip van die huidige klimaat op Mars en # 39 sal wetenskaplikes help om sy klimaatsgedrag in die verlede effektief te modelleer. Om dit te doen, het ons gedetailleerde weerkaarte van die planeet nodig en inligting oor hoeveel stof en waterdamp in die atmosfeer is.

Deur die planeet gedurende een volle Marsjaar (687 Aardae) vir hierdie inligting te monitor, sal dit ons help om te verstaan ​​hoe Mars gedurende sy seisoenale siklus optree, en sal ons lei om te verstaan ​​hoe die planeet oor miljoene jare verander.

Die gelaagde terrein van die Marspoolgebiede bevat ook leidrade oor die planeet se verlede, net soos die ringe van 'n boom 'n rekord van sy geskiedenis gee. Wanneer en hoe is hierdie poollae afgesit? Was die klimaat van Mars ooit soos die van die aarde? En indien wel, wat het die planeet verander in die droë, koue, dorre woestyn wat dit vandag is? Dit is die vrae waarop ons missies nog moet beantwoord.


Rotse op Mars

Moddersteen: Hierdie foto, geneem deur NASA se Mars Rover Curiosity in 2015, toon afsettingsgesteentes van die Kimberley-formasie in Gale Crater. Die krater bevat dik neerslae van fyn gelamineerde moddersteen wat fynkorrelige sedimente voorstel wat neergelê is in 'n staande watermassa wat vir 'n lang tydperk aangehou het - lank genoeg om sedimente tot aansienlike dikte te laat ophoop. Beeld deur NASA. Vergroot die prentjie. [8]

Sandsteen: Die foto is geneem deur NASA se Mars Rover Curiosity op 27 Augustus 2015 met behulp van sy mastkamera. Dit toon 'n uitkruis van kruisbed-sandsteen op die onderste helling van Mars 'Mount Sharp. Die kruisbeddegoed is baie soortgelyk aan die windgeblaasde sanduitvalle wat algemeen in die Amerikaanse suidweste voorkom. NASA het hierdie beeld direk vergelyk met 'n uitkyk van die Navajo Sandstone in Utah. Beeld deur NASA. Vergroot die prentjie. [7]

Skalie: Hierdie foto is geneem deur NASA se Mars Rover Curiosity in 2012 met behulp van sy mastkamera. Dit toon 'n gedeelte van 'n buitewêreld binne die Gale Krater. Hierdie aansig toon 'n oppervlakte van ongeveer een meter breed. Die kleur is gebalanseer om die toneel te laat lyk asof dit op die aarde is.

In hierdie beeld is gesteentes sigbaar wat baie ooreenstem met die skalies wat op die aarde voorkom. Hulle is fynkorrelig, dun laag en skeurbaar (wat beteken dat dit maklik in dun lakens breek). Rotse op aarde wat so breek, bestaan ​​gewoonlik uit kleiminerale of mika-korrels wat uit 'n waterige suspensie neergesak het. Hul plaatvormige korrels neergesit op die bodem in 'n parallelle oriëntasie. Dit gee die rots die vermoë om in dun lae te verdeel. Daar is bekend dat kleiminerale volop op Mars voorkom, en dit is waarskynlik dat hierdie gesteentes uit kleiminerale bestaan.

Mars-impakkraters is 'n wonderlike plek om rotse waar te neem, want die impak het 'n gat in die planeet se oppervlak geblaas met uitsakings in die kraterwalle. In hierdie toneel kan groot hoeveelhede fynkorrelige sedimente op die grond gesien word. Sediment op die oppervlak van Mars is 'n produk van miljoene jare van asteroïde-impak en meganiese verwering. Hulle word vandag deur die wind verwerk, en in die verlede is hulle verskuif, neergelê en deur stromende water herwerk. Beeld deur NASA. Vergroot die prentjie. [1]

Konglomeraat: Die foto aan die linkerkant is in 2012 deur NASA se Mars Rover Curiosity met behulp van sy mastkamera geneem. Dit toon 'n gedeelte van 'n rots wat soortgelyk is aan die konglomerate wat op die aarde voorkom. Die klippies onder die rots is groepe wat deur die rots verweer is. Die foto aan die regterkant is 'n konglomeraat van die aarde af om ooreenkomste te toon.

Die teenwoordigheid van konglomeraat en sandstene op Mars is 'n bewys van bewegende water. Wind is nie sterk genoeg om klippies van meer as een sentimeter in deursnee op te tel en in die stroom saam te dra nie. Die klippies in hierdie rots toon 'n hoë afrondingsvlak wat 'n aansienlike afstand van vervoer impliseer. Daar word vermoed dat die rooi kleur ystervlekke is, wat amper op Mars voorkom en dit die naam "Rooi Planeet" gee. Die "sement" wat die deeltjies in hierdie gesteentes bind, kan 'n sulfaatmineraal wees. Beeld deur NASA. Vergroot die prentjie. [2]

Kruis beddegoed: Dit is nog 'n foto wat deur NASA se Mars Rover Curiosity in 2012 geneem is met behulp van sy mastkamera in die Gale Krater. Dit toon 'n gedeelte van 'n uitkoms met 'n sedimentêre struktuur soortgelyk aan die kruisbedklippe wat op die aarde voorkom. Wanneer 'n sedimentêre gesteente wat in byna horisontale lae neergesit is, 'n lae laag het wat teen 'n ander hoek skuins is, staan ​​die struktuur bekend as 'kruisbeddegoed'. Die grootskaalse gelaagdheid in hierdie gesteentes is skuins na links, maar die kleiner inwendige lae skuins onder verskillende hoeke. Verskeie hoeke van kruisbeddegoed wys dat die rigting van wind of watervloei oor tyd verander het. Beeld deur NASA. Vergroot die prentjie. [3]

Kolomvormige basalt: Die beeld aan die linkerkant is van bo af geneem deur die Mars Reconnaissance Orbiter naby Marte Vallis. Dit toon 'n uitloop van 'n basaltvloei met kolomverbinding. Die foto aan die regterkant is 'n National Park Service-foto van die bekendste voorbeeld van kolomverbinding op aarde. Dit is van 'n basaltvloei wat by die Devils Postpile National Monument in Kalifornië uitkom. Beelde deur NASA en die National Park Service. [4]

Meteoriet: Dit is 'n foto van die 'Heat Shield Rock', die eerste meteoriet wat ooit op die oppervlak van 'n ander planeet ontdek is. Dit is 'n baseball-grootte yster-nikkel meteoriet wat deur NASA se Mars Exploration Rover Opportunity in 2005 ontdek is. Opportunity het 'n spektrofotometer gebruik om die samestelling daarvan te bepaal. Beeld deur NASA. Meer meteoriete vanaf Mars. [5]

Scoria: Hierdie beeld toon 'n veld besaai met stukke van 'n vulkaniese rots wat baie ooreenstem met die scoria wat op die aarde voorkom. Die rots op die voorgrond van die beeld is ongeveer 18 sentimeter breed en is deur die Spirit Rover gevind. Die rots het 'n growwe oppervlak en blasies soos scoria. Beeld deur NASA. [6]

Sandduine: Hierdie satellietbeeld wat deur NASA se Mars Reconnaissance Orbiter in Julie 2015 verkry is, toon 'n sandduin wat oor 'n baie gebreekte berggrondoppervlak beweeg wat deur fisiese spanning en temperatuurverandering gebreek is. Die voorste oppervlak van die sandduin is bedek met sand rimpelings. Dit is net een uit 'n enorme veld duine. Beeld deur NASA. Vergroot die prentjie. [9]

Ejecta-ringe rondom impakkraters: Die paar satellietbeelde hierbo toon asteroïde-inslagkraters en hul helder ringe van uitwerpings. Die studie van impakkraters op aarde help wetenskaplikes om impakkraters op ander planete en mane in ons sonnestelsel te verstaan.

Die ronde funksie in die middel van die beeld aan die linkerkant is 'n onlangs gevormde impakkrater op Mars. Dit word omring deur 'n helder, stervormige neerslag van uitwerp wat deur die krag van die inslag uit die krater geblaas is. Die helder kleur van die uitwerp kontrasteer skerp met die donkerder oppervlakkige materiaal rondom die krater. Dit is 'n klein krater, ongeveer 13 meter in deursnee. Die beeld is in Januarie 2021 deur die Context Camera op die Mars Reconnaissance Orbiter vasgelê. [10]

Die ronde funksie in die middel van die prentjie aan die regterkant is Meteor Crater, 'n asteroïde-impakkrater naby Flagstaff, Arizona. Dit het ook 'n helder ring van uitwerp, maar die ring is nie so helder nie, want hierdie impakstruktuur is ongeveer 50 000 jaar oud. Gedurende die tyd was die uitwerping verweer en gemeng met plaaslike oppervlakkige materiale deur die werking van wind en neerslag. Meteor Krater is ongeveer 1200 meter in deursnee. Die beeld is voorberei deur NASA Earth Observatory met behulp van Landsat-data van die United States Geological Survey. [11]

Sedimentêre ritmes: Hierdie satellietbeeld, wat in Desember 2008 deur die NASA se Mars Reconnaissance Orbiter verkry is, toon 'n gebied van gelaagde sedimentêre gesteentes in die Becquerel-krater van Mars. Hierdie beeld was die eerste wat 'n rekord van ritmiese sedimentasie in die rotse van Mars onthul het, wat waarskynlik veroorsaak is deur 'n kombinasie van klimaatsiklusse en astronomiese siklusse. Lae van dieselfde dikte in hierdie gebied (en in drie nabygeleë kraters) herhaal tientalle tot honderde kere. Die rotslae is verweer tot 'n trap-topografie waar lae wat weerstandbiedend is vir verwerende kaplae wat minder bestand is - soortgelyk aan die patroon op die aarde waar lae sedimentêre gesteentes blootgestel word oor breë gebiede. Beeld deur NASA. Vergroot die prentjie. [12]

Inligting oor die foto's
[1] Wye aansig van 'Shaler' Outcrop, Sol 120: Beeldvrystelling geplaas op NASA se Curiosity Rover-webwerf, Januarie 2013.

[2] NASA Rover Find Old Streambed on Martian Surface: Beeldvrystelling geplaas op NASA se Curiosity Rover-webwerf, September 2012.

[3] Bewyse van 'Shaler' Unit of Stream Flow: Beeldvrystelling geplaas op NASA se Curiosity Rover-webwerf, Desember 2012.

[4] 'Heuningkoeke' en heksakopters help om die verhaal van Mars te vertel: artikel is op die NASA se webwerf van die sonnestelsel, Februarie 2012, gepubliseer.

[5] Opportunity Rover vind 'n ystermeteoriet op Mars: artikel verskyn op NASA se Exploration Rover-webwerf, Januarie 2005.

[6] Volcanic Bumpy Boulder on Mars: Astronomy Picture of the Day vir 15 Mei 2006.

[7] Vista from Curiosity Shows Crossbedded Martian Sandstone: artikel geplaas op NASA se Mars Science Laboratory-webwerf, September 2015.

[8] NASA se Curiosity Rover Team bevestig antieke mere op Mars: artikel is op NASA se Mars Science Laboratory-webwerf, Oktober 2015, geplaas.

[9] Al die frakture: artikel geplaas op die NASA se Mars Science Laboratory webwerf, Oktober 2015.

[10] 'n Nuwe impakkrater met Bright Ejecta: artikel deur NASA, JPL-Caltech en die Universiteit van Arizona op 24 Mei 2021 op die NASA-webwerf geplaas.

[11] Arizona's Meteor Crater: Artikel deur Joshua Stevens en Kathryn Hansen geplaas op die NASA Earth Observatory Webwerf, 16 Mei 2021.


Vorming:

Ongeveer 4,5 miljard jaar gelede het ons sonnestelsel in die konfigurasie gekom wat ons vandag sien.

Mars is gevorm toe die wervelende gas en stof weens swaartekrag saamgeval het en die vierde plant uit die son geskep het.

Terwyl ons ander sonnestelsels ondersoek, sien ons dat baie van hul groter gasreuse diegene is wat nader aan die binnebane van die son is, en ons sonnestelsel verskil omdat ons aardplanete het wat nader is.

Mars is 'n aardse planeet met 'n sentrale kern, rotsagtige mantel en 'n soliede kors.


Toe die sonnestelsel ongeveer 4,5 miljard jaar gelede in die huidige uitleg was, het Mars gevorm toe swaartekrag wervelende gas en stof ingehaal het om die vierde planeet van die son te word. Mars is ongeveer die helfte so groot soos die aarde, en net soos sy aardse planete het dit 'n sentrale kern, 'n rotsagtige mantel en 'n soliede kors.

Die Rooi Planeet is eintlik baie kleure. Aan die oppervlak sien ons kleure soos bruin, goud en bruin. Die rede waarom Mars rooierig lyk, is die gevolg van oksidasie en roesroes en yster in die rotse, regoliet (Mars & ldquosoil & rdquo) en stof van Mars. Hierdie stof word in die atmosfeer opgeskop en laat die planeet op 'n afstand meestal rooi lyk.

Interessant genoeg, terwyl Mars ongeveer die helfte van die deursnee van die aarde is, het die oppervlak daarvan amper dieselfde oppervlakte as die droëland van die aarde en rsquos. Sy vulkane, impakkraters, korstbeweging en atmosferiese toestande soos stofstorms het die landskap van Mars oor baie jare verander, wat van die mees interessante topografiese kenmerke van die sonnestelsel geskep het.

'N Groot kloofstelsel genaamd Valles Marineris is lank genoeg om van Kalifornië tot New York en meer as 4800 kilometer te strek. Hierdie Mars-kloof is 320 kilometer op sy breedste en 7 kilometer op sy diepste. Dit is ongeveer tien keer so groot soos die Aarde en die Grand Canyon.

'N Groot skaal

Mars is die tuiste van die grootste vulkaan in die sonnestelsel, Olympus Mons. Dit is drie keer hoër as die Aarde & Mt. Everest met 'n basis van die grootte van die staat New Mexico.

Dit lyk asof Mars 'n waterige verlede gehad het, met ou riviervallei-netwerke, delta's en meerbeddings, sowel as rotse en minerale op die oppervlak wat net in vloeibare water kon gevorm het. Sommige kenmerke dui daarop dat Mars ongeveer 3,5 miljard jaar gelede groot oorstromings ervaar het.

Daar is vandag water op Mars, maar die atmosfeer van die Mars is te dun vir vloeibare water om lank op die oppervlak te bestaan. Vandag word water op Mars aangetref in die vorm van water-ys net onder die oppervlak in die poolgebiede, sowel as in soutwater (sout) wat seisoenaal afloop op sommige heuwels en kraterwalle.


Mariner 9-beelding het die eerste direkte bewyse van water in die vorm van rivierbeddings, klowe (insluitend die Valles Marineris, 'n stelsel van klowe van meer as 4 020 kilometer (2500 myl), onthul, bewyse van erosie en afsetting van water, weerskante, mis , en meer. [1] Die bevindings van die Mariner 9-missies was die latere Viking-program. Die enorme Valles Marineris-kloofstelsel is vernoem na Mariner 9 ter ere van sy prestasies.

Warrego Valles, soos gesien deur Mariner 9. Hierdie beeld dui daarop dat reën / sneeu nodig was om hierdie soort vertakte netwerk van kanale te vorm.

Deur die ontdekking van baie geologiese vorms wat gewoonlik uit groot hoeveelhede water gevorm word, het Viking-wentelbane 'n rewolusie veroorsaak in ons idees oor water op Mars. Groot riviervalleie is in baie gebiede aangetref. Hulle het getoon dat vloede water deur damme gebreek het, diep valleie gekerf het, groewe in die rots geslyp het en duisende kilometers afgelê het. [2] Groot gebiede in die suidelike halfrond het vertakte vallei-netwerke bevat, wat daarop dui dat reën eens geval het. Die flanke van sommige vulkane is vermoedelik blootgestel aan reënval omdat dit lyk soos die wat op Hawaise vulkane voorkom. [3] Baie kraters lyk asof die impak in modder geval het. Toe hulle gevorm is, het ys in die grond moontlik gesmelt, die grond in modder verander en dan het die modder oor die oppervlak gevloei. [4] Normaalweg gaan materiaal van 'n impak op, dan af. Dit vloei nie oor die oppervlak nie en loop ook nie deur hindernisse soos in sommige Mars-kraters nie. [5] [6] [7] Dit lyk asof streke, wat 'chaotiese terrein' genoem word, vinnig groot hoeveelhede water verloor het, wat veroorsaak het dat groot kanale stroomaf gevorm het. Die hoeveelheid water wat betrokke was, was byna ondenkbaar - ramings vir sommige kanaalvloei beloop tien duisend keer die vloei van die Mississippi-rivier. [8] Ondergrondse vulkanisme het moontlik bevrore ys gesmelt, die water het dan weggevloei en die grond het net in duie gestort om chaotiese terrein te verlaat.

Die onderstaande beelde, van die beste van die Viking Orbiters, is mosaïeke van baie klein, hoë resolusie beelde. Klik op die prente vir meer besonderhede. Sommige van die foto's is gemerk met plekname.

Bahram Vallis, soos gesien deur Viking. Valley is geleë in Noord-Lunae Planum en die Lunae Palus vierhoek. Dit lê byna halfpad tussen Vedra Valles en onderste Kasei Valles.

Gestroomlynde eilande wat deur Viking gesien is, het getoon dat groot oorstromings op Mars voorgekom het. Beeld is in die vierhoek van Lunae Palus geleë.

Traandruppelvormige eilande veroorsaak deur vloedwater van Maja Valles, soos gesien deur Viking Orbiter. Beeld is in die vierhoek van Oxia Palus geleë. Die eilande word gevorm in die uitwerp van die kraters van Lod, Bok en Gold.

Skuurpatrone, geleë in die vierhoek van Lunae Palus, is vervaardig deur vloeiende water uit Maja Valles, wat net links van hierdie mosaïek lê. Die detail van die vloei rondom die Dromore-krater word op die volgende afbeelding getoon.

Groot hoeveelhede water was nodig om die erosie in hierdie Viking-beeld uit te voer. Beeld is in die vierhoek van Lunae Palus geleë. Die erosie het die uitwerping rondom die Dromore-krater gevorm.

Water van Vedra Valles, Maumee Valles en Maja Valles het vanaf Lunae Planum aan die linkerkant, na Chryse Planitia aan die regterkant. Image is geleë in die Lunae Palus vierhoek en is deur Viking Orbiter geneem.

Die uitwerp van die Arandas-krater werk soos modder. Dit beweeg om klein kraters (aangedui deur pyle), in plaas daarvan om net daarop neer te val. Kraters soos hierdie dui daarop dat groot hoeveelhede bevrore water gesmelt is toe die impakkrater geproduseer is. Image is geleë in die Mare Acidalium vierhoek en is deur Viking Orbiter geneem.

Hierdie uitsig op die flank van Alba Mons toon verskeie kanale / bakke. Sommige kanale hou verband met lawastrome, ander word waarskynlik deur lopende water veroorsaak. 'N Groot bak of graben verander in 'n lyn van ineenstortingsputte. Beeld is in Arcadia vierhoek en is deur Viking Orbiter geneem.

Vertakte kanale in Thaumasia vierhoek, soos gesien deur Viking Orbiter. Netwerke van kanale soos hierdie is 'n sterk bewys vir reën op Mars in die verlede.

Die vertakte kanale wat deur Viking vanaf 'n baan gesien is, het sterk aangedui dat dit vroeër op Mars gereën het. Beeld is in die vierhoek van Margaritifer Sinus geleë.

Ravi Vallis, soos gesien deur Viking Orbiter. Ravi Vallis is waarskynlik gevorm toe katastrofiese vloede regs uit die grond gekom het (chaotiese terrein). Beeld in die vierkant van Margaritifer Sinus.

Resultate van landingseksperimente van Viking dui sterk op die teenwoordigheid van water in die hede en in die verlede van Mars. Al die monsters wat in die gaschromatograaf-massaspektrometer (GSMS) verhit is, het water afgegee. Die manier waarop die monsters hanteer is, het egter 'n presiese meting van die hoeveelheid water verbied. Maar dit was ongeveer 1%. [9] Algemene chemiese ontleding het voorgestel dat die oppervlak in die verlede aan water blootgestel is. Sommige chemikalieë in die grond bevat swael en chloor wat soos die oorblyfsels was nadat seewater verdamp het. Swael was meer gekonsentreer in die kors bo-op die grond as in die grootste grond daaronder. Daar is dus tot die gevolgtrekking gekom dat die boonste kors saamgesementeer is met sulfate wat in die water opgelos is na die oppervlak. Hierdie proses is algemeen in die woestyne van die aarde. Die swael kan voorkom as sulfate van natrium, magnesium, kalsium of yster. 'N Ystersulfied is ook moontlik. [10] Met behulp van die resultate van die chemiese metings, dui minerale modelle aan dat die grond 'n mengsel van ongeveer 90% ysterryke klei, ongeveer 10% magnesiumsulfaat (kieseriet?), Ongeveer 5% karbonaat (kalsiet) en ongeveer 5 kan wees. % ysteroksiede (hematiet, magnetiet, goetiet?). Hierdie minerale is tipiese verweringsprodukte van maffiese stollingsgesteentes. Die aanwesigheid van klei, magnesiumsulfaat, kieseriet, kalsiet, hematiet en goetiet dui sterk daarop dat water eens in die omgewing was. [11] Sulfaat bevat chemies gebonde water, en dit dui daarop dat water in die verlede bestaan ​​het. Viking 2 het 'n soortgelyke groep minerale gevind. Aangesien Viking 2 baie verder noord was, het dit in die winter ryp getoon.

Foto van die Viking 2-lander geneem deur die Mars Reconnaissance Orbiter in Desember 2006.

Ryp by die landingsterrein.

Die Mars Global Surveyor's Thermal Emission Spectrometer (TES) is 'n instrument wat minerale samestelling op Mars kan opspoor. Mineraalsamestelling gee inligting oor die teenwoordigheid of afwesigheid van water in antieke tye. TES het 'n groot (30 000 vierkante kilometer) gebied (in die Nili Fossae-formasie) geïdentifiseer wat die mineraal olivien bevat. Daar word vermoed dat die antieke impak wat die Isidis-kom geskep het, gelei het tot foute wat die olivyn blootgestel het. Olivien kom voor in baie mafiese vulkaniese gesteentes in die teenwoordigheid van water wat dit verweer in minerale soos goetiet, chloriet, smektiet, maghemiet en hematiet. Die ontdekking van olivien is 'n sterk bewys dat dele van Mars lank droog was. Olivien is ook in baie ander klein buitewyke binne 60 grade noord en suid van die ewenaar ontdek. [12] Olivien is gevind in die SNC (shergottiet, nakhliet en chassigny) meteoriete wat algemeen aanvaar word dat dit van Mars afkomstig is. [13] Latere studies het bevind dat olivienryke gesteentes meer as 113 000 vierkante kilometer van die Marsoppervlak beslaan. Dit is 11 keer groter as die vyf vulkane op die Big Island of Hawaii. [14]

Op 6 Desember 2006 publiseer NASA foto's van twee kraters genaamd Terra Sirenum en Centauri Montes, wat op een of ander stadium tussen 1999 en 2001. die voorkoms van vloeibare water op Mars toon. [15] [16]

Honderde slote is ontdek wat gevorm is uit vloeibare water, wat die afgelope tyd moontlik was. Hierdie slote kom op steil hellings voor en meestal in sekere breedtebande. [17] [18] [19] [20] [21]

Hieronder is 'n paar voorbeelde van slote wat deur Mars Global Surveyor gefotografeer is.

Groep slote op die noordelike muur van die krater wat wes van die krater Newton lê (41,3047 suid breedtegraad, 192,89 oos longitide). Beeld is in die Phaethontis-vierhoek geleë.

Meeue in 'n krater in die Eridania-vierhoek, noord van die groot krater Kepler. Daar is kenmerke wat oorblyfsels van ou gletsers kan bevat. Een het regs die vorm van 'n tong.

Gullies aan die een muur van die Kaiser-krater. Meeue kom gewoonlik net in een muur van 'n krater voor. Die ligging is 'n vierhoek van Noachis.

Volkleurbeeld van slote op die muur van Gorgonum Chaos. Beeld is in die Phaethontis-vierhoek geleë.

'N Paar kanale op Mars vertoon binnekanale wat dui op volgehoue ​​vloeistofvloei. Die bekendste is die een in Nanedi Valles. Nog een is in Nirgal Vallis gevind. [17]

Baie plekke op Mars wys donker strepe op steil hellings, soos kratermure. Donker hellingstreke is sedert die Mariner- en Viking-missies bestudeer. [22] Dit lyk asof strepe donker begin word, dan word hulle ligter met die ouderdom. Dikwels het hulle 'n klein smal plek, dan brei dit honderde meter af en brei dit afdraand uit. Dit lyk asof strepe nie met 'n spesifieke laag materiaal geassosieer word nie, want dit begin nie altyd op 'n gemeenskaplike vlak langs 'n helling nie. Alhoewel baie van die strepe baie donker lyk, is dit net 10% of minder donkerder as die omliggende oppervlak. Mars Global Surveyor het bevind dat daar binne minder as een jaar nuwe strepe op Mars ontstaan ​​het.

Verskeie idees is gevoer om die strepe te verduidelik. Sommige betrek water, [23] of selfs die groei van organismes. [24] [25] Die algemeen aanvaarde verklaring vir die strepe is dat dit gevorm word deur die stortvloed van 'n dun laag helder stof wat 'n donkerder oppervlak bedek. Helder stof lê na 'n tydperk op alle Marsoppervlaktes. [17]

Donker strepe kan op die onderstaande beelde gesien word, soos gesien deur Mars Global Surveyor.

Lae in die Tikhonravov-krater in Arabië. Lae kan ontstaan ​​uit vulkane, die wind of deur neerslag onder water. Die kraters aan die linkerkant is voetstukkraters. Dit lyk asof donker strepe uit sekere lae ontstaan ​​(u moet miskien op die prentjie klik om die strepe te sien).

Tikhonravov-kratervloer in Arabië vierhoekig. Klik op die prentjie om donker hellingstrepe en lae te sien.

Donker strepe in Arabië vierhoekig. Krater is ongeveer so groot soos die aarde se meteoorkrater in Arizona.

Sommige dele van Mars toon omgekeerde verligting. Dit vind plaas wanneer materiale op die vloer van 'n stroom neergelê word en dan weerstand bied teen erosie, miskien deur sementering. Later kan die gebied begrawe word. Uiteindelik verwyder erosie die bedekkingslaag. Eersgenoemde strome word sigbaar omdat dit bestand is teen erosie. Mars Global Surveyor het verskeie voorbeelde van hierdie proses gevind. [26] Baie omgekeerde strome is in verskillende streke van Mars ontdek, veral in die Medusae Fossae-formasie, [27] Miyamoto-krater, [28] en die Juventae-plato. [29] [30]

Die onderstaande afbeelding toon een voorbeeld.

Omgekeerde strome naby Juventae Chasma, soos gesien deur Mars Global Surveyor. Hierdie strome begin bo-op 'n rant en loop dan saam.

Pathfinder het gevind dat die temperatuur gedurende 'n dag siklus wissel. Dit was die koudste net voor sonop (ongeveer -78 Celsius) en die warmste net na die middaguur van Maart (ongeveer -8 Celsius). Hierdie uiterstes het naby die grond voorgekom, wat beide die vinnigste opgewarm en afgekoel het. Op hierdie plek het die hoogste temperatuur nooit die vriespunt van water (0 ° C) bereik nie, en Mars Pathfinder het bevestig dat dit te koud is vir vloeibare water waar dit beland het. Water kan egter as vloeistof bestaan ​​as dit met verskillende soute gemeng word. [31]

Oppervlaktedruk het daagliks oor 'n 0,2 millibar-reeks gewissel, maar het 2 daaglikse minima en twee daaglikse maksimums getoon. Die gemiddelde daaglikse druk het afgeneem van ongeveer 6,75 millibars tot 'n laagtepunt van net minder as 6,7 millibars, wat ooreenstem met die maksimum hoeveelheid koolstofdioksied op die suidpool. Die druk op die aarde is oor die algemeen nagenoeg 1000 millibars, dus die druk op Mars is baie laag. Die druk wat deur Pathfinder gemeet word, laat nie water of ys op die oppervlak toe nie. Maar as ys met 'n grondlaag geïsoleer is, kan dit lank duur. [32]

Ander waarnemings stem ooreen met die feit dat daar water in die verlede was. Sommige van die rotse op die Mars Pathfinder-terrein leun teen mekaar op 'n manier wat geoloë noem. Daar word geglo dat sterk vloedwater in die verlede die rotse rondgedruk het totdat dit van die stroom af gekyk het. Sommige klippies is afgerond, miskien in 'n stroom. Dele van die grond is korsagtig, miskien as gevolg van sementering deur 'n vloeistof wat minerale bevat. [33]

Daar was bewyse van wolke en miskien mis. [33]

In July 2003, at a conference in California, it was announced that the Gamma Ray Spectrometer (GRS) on board the Mars Odyssey had discovered huge amounts of water over vast areas of Mars. Mars has enough ice just beneath the surface to fill Lake Michigan twice. [34] In both hemispheres, from 55 degrees latitude to the poles, Mars has a high density of ice just under the surface one kilogram of soil contains about 500 g of water ice. But, close to the equator, there is only 2 to 10% of water in the soil. [35] [36] Scientists believe that much of this water is locked up in the chemical structure of minerals, such as clay and sulfates. Previous studies with infrared spectroscopes have provided evidence of small amounts of chemically or physically bound water. [37] [38] The Viking landers detected low levels of chemically bound water in the Martian soil. [9] It is believed that although the upper surface only contains a percent or so of water, ice may lie just a few feet deeper. Some areas, Arabia Terra, Amazonis quadrangle, and Elysium quadrangle contain large amounts of water. [35] [39] Analysis of the data suggest that the southern hemisphere may have a layered structure. [40] Both of the poles showed buried ice, but the north pole had none close to it because it was covered over by seasonal carbon dioxide (dry ice). When the measurements were gathered, it was winter at the north pole so carbon dioxide had frozen on top of the water ice. [34] There may be much more water further below the surface the instruments aboard the Mars Odyssey are only able to study the top meter or so of soil. If all holes in the soil were filled by water, this would correspond to a global layer of water 0.5 to 1.5 km deep. [41]

The Phoenix lander confirmed the initial findings of the Mars Odyssey. [42] It found ice a few inches below the surface and the ice is at least 8 inches deep. When the ice is exposed to the Martian atmosphere it slowly sublimates. In fact, some of the ice was exposed by the landing rockets of the craft. [43]

Thousands of images returned from Odyssey support the idea that Mars once had great amounts of water flowing across its surface. Some pictures show patterns of branching valleys. Others show layers that may have formed under lakes. Deltas have been identified. [44]

For many years researchers believed that glaciers existed under a layer of insulating rocks. [45] [46] [47] [48] [49] Lineated deposits are one example of these probable rock-covered glaciers. They are found on the floors of some channels. Their surfaces have ridged and grooved materials that deflect around obstacles. Some glaciers on the Earth show such features. Lineated floor deposits may be related to lobate debris aprons, which have been proven to contain large amounts of ice by orbiting radar. [48] [49] [50]

The pictures below, taken with the THEMIS instrument on board the Mars Odyssey, show examples of features that are associated with water present in the present or past. [51]

Drainage features in Reull Vallis. Click on image to see relationship of Reull Vallis to other features. Location is Hellas quadrangle.

Reull Vallis with lineated floor deposits. Click on image to see relationship to other features. Floor deposits are believed to be formed from ice movement. Location is Hellas quadrangle.

Auqakuh Vallis. At one time a dark layer covered the whole area, now only a few pieces remain as buttes. Click on image to see layers. Layers may have formed from deposition on the bottom of lakes.

Huo Hsing Vallis in Syrtis Major quadrangle. Straight ridges may be dikes in which liquid rock once flowed.

Nirgal Vallis that runs in two quadrangles has features looking like those caused by sapping. Nirgal Vallis is one of many ancient river valleys studied by THEMIS.

The long channel Nirgal Vallis is shown where it connects to Uzboi Vallis. The crater Luki is 21 km in diameter.

Channels near Warrego Valles. These branched channels are strong evidence for flowing water on Mars, perhaps during a much warmer period.

Semeykin Crater Drainage. Click on image to see details of beautiful drainage system. Location is Ismenius Lacus quadrangle.

Erosion features in Ares Vallis – the streamined shape was probably formed by running water.

Athabasca Valles showing source of its water, Cerberus Fossae. Note streamined islands which show direction of flow to south. Athabasca Valles is in the Elysium quadrangle.

Channels west of Echus Chasma. The fine pattern of branching valleys were probably formed by water moving across the surface. Image is in Coprates quadrangle.

Dendritic channels on mesa of Echus Chasma. Image is 20 miles wide. Image is in Coprates quadrangle.

Branching channels on floor of Melas Chasma. Image is in Coprates quadrangle.

Much of the surface of Mars is covered by a thick smooth mantle that is thought to be a mixture of ice and dust. [52] [53] This ice-rich mantle, a few yards thick, smooths the land, but in places it displays a bumpy texture, resembling the surface of a basketball. The low density of craters on the mantle means it is relatively young.

Changes in Mars's orbit and tilt cause significant changes in the distribution of water ice. During certain climate periods water vapor leaves polar ice and enters the atmosphere. The water returns to the ground at lower latitudes as deposits of frost or snow mixed generously with dust. The atmosphere of Mars contains a great deal of fine dust particles. Water vapor condenses on the particles, then they fall down to the ground due to the additional weight of the water coating. When ice at the top of the mantling layer returns to the atmosphere, it leaves behind dust, which insulates the remaining ice. [54]

Dao Vallis begins near a large volcano, called Hadriaca Patera, so it is thought to have received water when hot magma melted huge amounts of ice in the frozen ground. The partially circular depressions on the left side of the channel in the image above suggests that groundwater sapping also contributed water. [55]

In some areas large river valleys begin with a landscape feature called "chaos" or chaotic terrain." It is thought that the ground collapsed, as huge amounts of water were suddenly released. Examples of chaotic terrain, as imaged by THEMIS, are shown below.

Blocks in Aram Chaos showing possible source of water. The ground collapsed when large amounts of water were released. The large blocks probably still contain some water ice. Location is Oxia Palus quadrangle.

Huge canyons in Aureum Chaos. Click on image to see the gullies which may have formed from recent flows of water. Gullies are rare at this latitude. Location is Margaritifer Sinus quadrangle.

The Phoenix lander confirmed the existence of large amounts of water ice in the northern regions of Mars. [42] This finding was predicted by theory. [56] and was measured from orbit by the Mars Odyssey instruments. [36] On June 19, 2008, NASA announced that dice-sized clumps of bright material in the "Dodo-Goldilocks" trench, dug by the robotic arm, had vaporized over the course of four days, strongly implying that the bright clumps were composed of water ice which sublimated following exposure. Even though dry ice also sublimates under the conditions present, it would do so at a rate much faster than observed. [57] [58] [59]

On July 31, 2008, NASA announced that Phoenix confirmed the presence of water ice on Mars. During the initial heating cycle of a new sample, the Thermal and Evolved-Gas Analyzer's (TEGA) mass spectrometer detected water vapor when the sample temperature reached 0 °C. [60] Liquid water cannot exist on the surface of Mars with its present low atmospheric pressure, except at the lowest elevations for short periods. [61] [62]

Results published in the journal Science after the mission ended reported that chloride, bicarbonate, magnesium, sodium potassium, calcium, and possibly sulfate were detected in the samples. Perchlorate (ClO4), a strong oxidizer, was confirmed to be in the soil. The chemical when mixed with water can greatly lower freezing points, in a manner similar to how salt is applied to roads to melt ice. Perchlorate may be allowing small amounts of liquid water to form on Mars today. Gullies, which are common in certain areas of Mars, may have formed from perchlorate melting ice and causing water to erode soil on steep slopes. [63]

Additionally, during 2008 and early 2009, a debate emerged within NASA over the presence of 'blobs' which appeared on photos of the vehicle's landing struts, which have been variously described as being either water droplets or 'clumps of frost'. [64] Due to the lack of consensus within the Phoenix science project, the issue had not been raised in any NASA news conferences. [64] One scientist's view poised that the lander's thrusters splashed a pocket of brine from just below the Martian surface onto the landing strut during the vehicle's landing. The salts would then have absorbed water vapor from the air, which would have explained how they appeared to grow in size during the first 44 Martian days before slowly evaporating as Mars temperature dropped. [64] [65] Some images even suggest that some of the droplets darkened, then moved and merged this is strong physical evidence that they were liquid. [66] [67] [68] [69]

Dice-sized clumps of bright material in the enlarged "Dodo-Goldilocks" trench vanished over the course of four days, implying that they were composed of ice which sublimated following exposure. [57]

Color versions of the photos showing ice sublimation, with the lower left corner of the trench enlarged in the insets in the upper right of the images.

For about as far as the camera can see, the land is flat, but shaped into polygons between 2–3 meters in diameter and are bounded by troughs that are 20 cm to 50 cm deep. These shapes are due to ice in the soil expanding and contracting due to major temperature changes.

Comparison between polygons photographed by Phoenix on Mars.

. and as photographed (in false color) from Mars orbit.

The microscope showed that the soil on top of the polygons is composed of flat particles (probably a type of clay) and rounded particles. Clay is a mineral that forms from other minerals when water is available. So, finding clay proves the existence of past water. [70] Ice is present a few inches below the surface in the middle of the polygons, and along its edges, the ice is at least 8 inches deep. When the ice is exposed to the Martian atmosphere it slowly sublimates. [71]

Snow was observed to fall from cirrus clouds. The clouds formed at a level in the atmosphere that was around −65 °C, so the clouds would have to be composed of water-ice, rather than carbon dioxide-ice (dry ice) because the temperature for forming carbon dioxide ice is much lower—less than −120 °C. As a result of mission observations, it is now believed that water ice (snow) would have accumulated later in the year at this location. [72] The highest temperature measured during the mission was −19.6 °C, while the coldest was −97.7 °C. So, in this region the temperature remained far below the freezing point (0°) of water. Bear in mind that the mission took place in the heat of the Martian summer. [73]

Interpretation of the data transmitted from the craft was published in the journal Science. As per the peer reviewed data the site had a wetter and warmer climate in the recent past. Finding calcium carbonate in the Martian soil leads scientists to believe that the site had been wet or damp in the geological past. During seasonal or longer period diurnal cycles water may have been present as thin films. The tilt or obliquity of Mars changes far more than the Earth hence times of higher humidity are probable. [74] The data also confirms the presence of the chemical perchlorate. Perchlorate makes up a few tenths of a percent of the soil samples. Perchlorate is used as food by some bacteria on Earth. [75] Another paper claims that the previously detected snow could lead to a buildup of water ice.

The Mars Rovers Spirit and Opportunity found a great deal of evidence for past water on Mars. Designed to last only three months, both were still operating after more than six years. Spirit got trapped in a sand pit in 2006, with NASA officially cutting with the rover in 2011. Opportunity lost contact with NASA on June 10 2018 and its mission was declared complete on February 13 2019.

The Spirit rover landed in what was thought to be a huge lake bed. However, the lake bed had been covered over with lava flows, so evidence of past water was initially hard to detect. As the mission progressed and the Rover continued to move along the surface more and more clues to past water were found.

On March 5, 2004, NASA announced that Spirit had found hints of water history on Mars in a rock dubbed "Humphrey". Raymond Arvidson, the McDonnell University Professor and chair of Earth and planetary sciences at Washington University in St. Louis, reported during a NASA press conference: "If we found this rock on Earth, we would say it is a volcanic rock that had a little fluid moving through it." In contrast to the rocks found by the twin rover Opportunity, this one was formed from magma and then acquired bright material in small crevices, which look like crystallized minerals. If this interpretation holds true, the minerals were most likely dissolved in water, which was either carried inside the rock or interacted with it at a later stage, after it formed. [76]

By Sol 390 (Mid-February 2005), as Spirit was advancing towards "Larry's Lookout", by driving up the hill in reverse, it investigated some targets along the way, including the soil target, "Paso Robles", which contained the highest amount of salt found on the red planet. The soil also contained a high amount of phosphorus in its composition, however not nearly as high as another rock sampled by Spirit, "Wishstone". Squyres said of the discovery, "We're still trying to work out what this means, but clearly, with this much salt around, water had a hand here".

As Spirit traveled with a dead wheel in December 2007, pulling the dead wheel behind, the wheel scraped off the upper layer of the martian soil, uncovering a patch of ground that scientists say shows evidence of a past environment that would have been perfect for microbial life. It is similar to areas on Earth where water or steam from hot springs came into contact with volcanic rocks. On Earth, these are locations that tend to teem with bacteria, said rover chief scientist Steve Squyres. "We're really excited about this," he told a meeting of the American Geophysical Union (AGU). The area is extremely rich in silica – the main ingredient of window glass. The researchers have now concluded that the bright material must have been produced in one of two ways. One: hot-spring deposits produced when water dissolved silica at one location and then carried it to another (i.e. a geyser). Two: acidic steam rising through cracks in rocks stripped them of their mineral components, leaving silica behind. "The important thing is that whether it is one hypothesis or the other, the implications for the former habitability of Mars are pretty much the same," Squyres explained to BBC News. Hot water provides an environment in which microbes can thrive and the precipitation of that silica entombs and preserves them. Squyres added, "You can go to hot springs and you can go to fumaroles and at either place on Earth it is teeming with life – microbial life. [77] [78]

Opportunity rover was directed to a site that had displayed large amounts of hematite from orbit. Hematite often forms from water. When Opportunity landed, layered rocks and marble-like hematite concretions ("blueberries") were easily visible. In its years of continuous operation, Opportunity sent back much evidence that a wide area on Mars was soaked in liquid water.

During a press conference in March 2006, mission scientists discussed their conclusions about the bedrock, and the evidence for the presence of liquid water during their formation. They presented the following reasoning to explain the small, elongated voids in the rock visible on the surface and after grinding into it (see last two images below). [79] These voids are consistent with features known to geologists as "vugs". These are formed when crystals form inside a rock matrix and are later removed through erosive processes, leaving behind voids. Some of the features in this picture are "disk-like", which is consistent with certain types of crystals, notably sulfate minerals. Additionally, mission members presented first data from the Mössbauer spectrometer taken at the bedrock site. The iron spectrum obtained from the rock El Capitan shows strong evidence for the mineral jarosite. This mineral contains hydroxide ions, which indicates the presence of water when the minerals were formed. Mini-TES data from the same rock showed that it consists of a considerable amount of sulfates. Sulfates also contain water.


Historical landforms

In addition to examining the relatively recent (geologically speaking) presence of water, the various missions have also studied the surface of the planet in a historical context. The river beds of Mars don't run wet today, but scientists can study them to learn more about the evolution of the planet. [Photos: The Search for Water on Mars]

The flatter northern plains of Mars may once have hosted an ocean, or possibly, as the planet cycled through dry periods, two. The more recent body of water would likely have only been temporary, seeping into the ground, evaporating, or freezing in less than a million years, scientists say.

Riverbeds and gullies indicate that water ran, at least briefly, across the surface of Mars. A hundred times more water may have flowed annually through a large channel system known as Marte Vallis than passes through the Mississippi River each year, according to estimates. The gullies themselves are smaller, likely forming during brief torrential rainstorms when fast-moving water could have carved them across the land.

Curiosity found indications that at least one region of Mars, Mount Sharp, was built by sediments deposited in a lake bed millions of years ago, suggesting large pools existed on the planet for significant time periods.

"If our hypothesis for Mount Sharp holds up, it challenges the notion that warm and wet conditions were transient, local, or only underground on Mars," Curiosity deputy project scientist Ashwin Vasavada of NASA's Jet Propulsion Laboratory (JPL) said in a statement.

On Earth, the land around rivers and lakes is wetter, made up of mud and clays. Such deposits exist on Mars as well, trapping water and indicating where larger bodies may have once existed.

Water on Mars may be doing something more than sitting pretty. A new study reveals that when the liquid boils, thanks to low pressures, it can make the sand levitate.

"Sediment levitation must therefore be considered when evaluating the formation of recent and present-day Martian mass wasting features, as much less water may be required to form such features than previously thought," the researchers wrote in their study, which was published in the journal Nature Communications.


What Did They See?

Images were taken by the High Resolution Imaging Science Experiment (HiRISE) camera, which is installed on the Mars Reconnaissance Orbiter (MRO). Upon thoroughly studying these images, researchers noticed dark streaks (called recurring slope linae or RSL) that demonstrated a noticeable pattern. They appeared during warm weather (these streaks appeared when the temperature rose above -23 degrees Celsius), but faded away when temperatures dropped. Further analysis of these streaks demonstrated that these lines are caused by salty liquid water.

The numbers represent &lsquonumber of billion years&rsquo (Credits: Wikipedia)


Throwback Thursday: The Story of Mars

And how we’re about to take the amazing scientific leap from “we think” to “we know” when it comes to its history.

“Mars once was wet and fertile. It’s now bone dry. Something bad happened on Mars. I want to know what happened on Mars so that we may prevent it from happening here on Earth.” -Neil deGrasse Tyson

Oh, it’s true alright, something bad did once happen on Mars. Looking out at the barren, frozen desert-like wasteland that it is today, it might give you chills to think that Earth could have wound up in much the same state if things were only a little bit different.

As it turns out, there isn’t any real danger of that happening to Earth anytime soon (or anything that needs preventing), it’s time to tell all of you the story — as best we know it — about our red neighbor, and why it is the way it is today.

You see, when we think about Mars, we think about the smallish, red, desolate world that fascinates us today. We mostly think about the tremendous impact craters, the large mountains and the dry, rocky terrain. But Mars wasn’t always this way, and we know that to be true. There are clues to that, even today. Aerial views from orbiting spacecraft show us phenomena like dried up riverbeds with oxbow bends in them,

polar ice caps and (occasionally) atmospheric clouds,

and recently, landers and rovers have found sedimentary structures in the terrain, silica-rich layers beneath the surface, and even hematite spheres, all evidence that water once flowed freely across the Martian surface.

But no longer is there water on the Martian surface, and there hasn’t been for more than a billion years, to the best of our knowledge. In fact, liquid water is pretty much an impossibility on Mars today! You probably remember that like all substances, water exists in the solid, liquid or gaseous phases dependent on the pressure and temperature of its environment. While all three phases are common on Earth, only two of those phases — the solid and gaseous ones — are possible if the pressure is below a certain threshold, occurring at the triple point of water.

Unfortunately, the average atmospheric pressure on Mars is just 0.6% of what it is on Earth, placing it at-or-below the triple point of water, which makes the liquid phase a practical impossibility. Unless you’re at the bottom of the deepest Martian trenches, there’s simply no way to have water in any phase other than solid or gas.

But the overwhelming evidence for a watery past tells us that the red planet wasn’t always this way. In fact, if we go back to the early Solar System, Mars and Earth likely weren’t all that different.

We know that our home world — in its infancy — was different from Earth today in a number of important ways. The atmosphere was rich with hydrogen, as the most common gases were water, ammonia, methane and hydrogen gas, all excellent at trapping heat. Even though the Sun was only about 80% as luminous as it is today, Earth still had vast oceans and liquid water throughout its surface. In addition, bombardment by asteroids and comets was many orders of magnitude more common than it is today, and all the organics necessary for complex life — the building blocks of everything in our biosphere today — were in place.

And to the best of our knowledge, aside from being a bit smaller and farther from the Sun, those were the conditions on Mars, too.

We know that life took hold on Earth relatively quickly, within the first few hundred million years. We also know that life was able to sustain itself on Earth Mars, to the best of our knowledge, was probably not so lucky. At some point — perhaps after the first one or two billion years — those similar conditions on Earth and Mars, those conditions that were so conducive to life, became very different. We’re not certain what happened, but we have a leading (and compelling) hypothesis.

We don’t think about it on a day-to-day basis, but the Sun is constantly spewing out a stream of ionized, high-energy particles in all directions. If all we had, instead of Earth, was a big rock covered in gas, that stream of particles — the solar wind — would strip that gas away in short order. But that doesn’t happen! The main reason that the Earth steeds has the thick atmosphere it does is because we’ve got a powerful magnetic field generated in our planet’s core. Our hot, molten outer core gives way to an active, solid inner core at many thousands of degrees Celsius their interplay generates a magnetic dynamo responsible for our planet’s magnetic field.

We typically think of the magnetic field as it is on the Earth’s surface, deflecting compass needles and aiding in navigation, but the reality is that it extends far into space! As high-energy, ionized particles stream towards us, the magnetic field deflects them, and protects us mightily from the solar wind, keeping our atmosphere intact.

But the Solar System is 4.5 billion years old now, and Mars is much, much smaller than Earth.

This is important, because it’s our size that allowed us to retain so much of our interior heat, but Mars was not so fortunate. Planets radiate heat away according to their surface area, and with a radius of just 3,390 km (or just 53% of Earth’s), Mars has just 28% of Earth’s surface area. But in addition to that, it’s much lower in mass Earth is approximately ten times as massive as Mars! Due to its much smaller mass-to-surface-area ratio, Mars has cooled much, much more quickly than Earth, including all the way down to its core. At some point, the dynamic magnetic field that Mars once had (and it had one we’ve seen fragments of the relic magnetic field imprinted in Martian rock) ceased to be. When that happened, the atmosphere of Mars was no longer protected from the solar wind.

On a world where a thick atmosphere and liquid water ruled for maybe a billion years or more, the death of Mars’ magnetic field meant that these high-energy, ionized particles would begin colliding with the particles in Mars’ upper atmosphere, giving many of them enough kinetic energy to escape from the gravitational pull of the red planet! In the span of just a few million years, Mars went from a world teeming with organics, liquid water and all the building blocks of life to the desolate, barren and mostly frozen world we see today.

At least, that’s the leading hypothesis. The big news from earlier this week is that the mission that’s about to test that hypothesis, Mars MAVEN, has just started its scientific mission!

We’ve already got rovers on the ground, digging into the soil, returning photographs, performing analysis and exploring the terrain in unprecedented detail. But if we want to know the story of what happened to Mars’ surface, that means learning what happened to Mars’ atmosphere, and MAVEN is right now becoming the first spacecraft to attempt to figure that out by measuring what’s happening to Mars’ atmosphere right now.

After a ten month journey, MAVEN reached Mars in September of this year, and then entered an eccentric orbit around the red planet, spending most of its time a significant distance — thousands of miles (or kilometers) — above the top of the Martian atmosphere. But once-per-orbit, it now dips down into the upper atmosphere and takes data. By measuring the solar wind and the flux of atmospheric particles escaping from Mars today, it’s going to give us the first hard data that will allow us to extrapolate how Mars lost its atmosphere in the first place!

One of the great things is that Mars Curiosity has similar instruments on board to the ones on MAVEN, so while MAVEN determines the atmospheric composition, elemental isotope ratios and presence-and-formation of volatiles (such as methane) in the upper atmosphere, Curiosity can do the same thing all the way down at the bottom of Mars’ atmosphere. In fact, Maven’s just returned its very first results, providing an element-based look at the upper atmosphere of Mars, and how it’s being stripped away by the solar wind even today!

With data combined from both missions, this incredible hypothesis of how the Martian atmosphere was reduced to such a paltry state will be scrutinized and possibly either validated or falsified by the forthcoming data! As the mission unfolds, you can follow its real-time status updates here.

So when you see this cold, dry, red planet hovering in the night skies, know that it not only wasn’t always that way, but that between the orbiters and the rovers we’ve got exploring it we just might be on the cusp of finding out how it came to be this way!

And that’s a little bit of insight into the fascinating, cautionary tale of Mars!


Why Is Water So Essential for Life?

Water. It's found everywhere on Earth, from the polar ice caps to steamy geysers. And wherever water flows on this planet, you can be sure to find life.

"When we find water here on Earth — whether it be ice-covered lakes, whether it be deep-sea hydrothermal vents, whether it be arid deserts — if there's any water, we've found microbes that have found a way to make a living there," said Brian Glazer, an oceanographer at the University of Hawaii at Manoa, who has studied astrobiology.

That's why NASA's motto in the hunt for extraterrestrial life has been "follow the water."

Yesterday (Sept. 28), NASA scientists announced they'd found it on Mars: Dark streaks that scientists have spotted seasonally for more than a decade in images of the Red Planet are evidence of flowing water, new research suggests. While the briny flows may be too full of chlorine-based salts to support life, they do raise the odds that Mars could have life right now, the researchers said. [In Photos: Is Water Flowing on Mars?]

But just why is water such a crucial molecule for life? And could there be other ingredients that also provide the perfect recipe for life on other planets?

It turns out that several chemical properties of water make it indispensable for living creatures. Not only can water dissolve nearly anything, but it is also one of only a few materials that can exist as solid, liquid and gas within a relatively narrow range of temperatures.

Flowing life

At heart, all life on Earth uses a membrane that separates the organism from its environment. To stay alive, the organism takes in important materials for making energy, while shuttling out toxic substances such as waste products.

In this regard, water is essential simply because it's a liquid at Earth-like temperatures. Because it flows, water provides an efficient way to transfer substances from a cell to the cell's environment. By contrast, deriving energy from a solid is a much tougher prospect (though there are microbes that eat rock), Glazer said.

But the other part of the equation — that water can carry things into and out of the cell — has to do with water's unique chemical configuration.

The humble water molecule is made up of two hydrogen atoms bonded to an oxygen atom.

"The way they're bonded together makes water this wonderful universal solvent," meaning that almost every substance can dissolve in water, Glazer told Live Science.

That's because the molecule has polarity, meaning the hydrogen atoms tend to bunch on one side of the molecule, creating a positive region, while the oxygen end has a negative charge. The positive hydrogen end tends to attract negative ions (or atoms with an extra electron in the outer shell), while the negative region lures in positive ions (which have had one of their electrons stripped off).

Water, with its amazing dissolving properties, is the perfect medium for transmitting substances, such as phosphates or calcium ions, into and out of a cell.

Phases of water

Another feature of water is that it can act as a solid, liquid and gas within the range of temperatures that occur on Earth. Other molecules that have been identified as good candidates for supporting life tend to be liquid at temperatures or pressures that would be inhospitable for most known life-forms, Glazer said. [5 Mars Myths and Misconceptions]

"Water really is at that sweet spot," Glazer said.

The fact that water can be in all three phases in a relatively tight range of pressures creates many opportunities for life to flourish, he added.

"All three [states of water] available on our planet creates this really neat variety of habitats and microclimates," Glazer said.

For instance, frozen ice can be found in glaciers that carve through mountains, whereas water vapor helps warm the atmosphere, Glazer said.

Watery cradle of life

Water may be more than a fluid to help facilitate life's essential processes — it may also have been the protective cradle that carried the building blocks of life to Earth, said Ralf Kaiser, a physical experimental chemist at the University of Hawaii at Manoa, who has research experience in astrochemistry.

One theory for how life on Earth emerged, called panspermia, posits that icy comets smashed into Earth, bearing tiny organic molecules that formed the precursors to life. But traveling through space is a harsh journey, with punishing levels of radiation that would normally degrade those delicate molecules, Kaiser said.

However, in its solid form, water could have provided a way to shield those molecules from radiation, Kasier speculated.

"One possibility is that because the building blocks are frozen within the water, it has this protective mantle around it that could be delivered," Kaiser told Live Science.

Accept some substitutes

Of course, while water is crucial to life on our home planet, there could be life-forms that don't conform to the Earthling playbook.

Scientists are also looking at other liquids that could play a similar role as universal solvent and transport medium. Some of the top contenders are ammonia and methane, said Chris McKay, an astrobiologist at the NASA Ames Research Center in Moffett Field, California. Ammonia, like water, is a polar molecule that is relatively abundant in the universe, but scientists haven't found any large bodies of ammonia anywhere in the solar system, McKay said.

Methane isn't polar, but it can dissolve many other substances. Unlike water, however, methane becomes liquid only at very cold temperatures — at a frigid minus 296 degrees Fahrenheit (minus 182 degrees Celsius).

"We know that there are large lakes of liquid methane and ethane on Titan," one of the moons of Saturn, McKay told Live Science in an email. "Thus there is keen interest is the question of whether life can use liquid methane/ethane."


Kyk die video: This is Mars 2018, Curiosity Rover (Desember 2022).