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Is stof die enigste rede waarom die Marshemel so helder is?

Is stof die enigste rede waarom die Marshemel so helder is?


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Die atmosferiese druk op die oppervlak van Mars is gemiddeld 0,00609 atm en hoogstens 0,012 atm in die Hellasbekken. Op die aarde, onder hierdie druk, wat op 30-35 km (19-22 myl) hoogtes voorkom, is die lug baie swart en vol sterre. Op die Marsoppervlak is die lug egter steeds helder (naamlik oranje) en bedags is daar geen sterre / planete sigbaar vanaf die seevlak nie (behalwe die son en miskien die aarde). Is dit slegs te danke aan die baie stof in die Mars-atmosfeer, of is daar ook ander redes waarom die lug nie swart is nie, maar steeds oranje is tydens hierdie druk?


Dit is heel waarskynlik as gevolg van stofdeeltjies. Die kleur van die Marshemel word beskryf as geelbruin "butterscotch" -kleur gedurende die dag (soms pienkrooi) en blou tydens die opkoms en sonondergang (baie anders as wat op aarde gebeur). Die tipiese kleur is omdat die stofdeeltjies in die lug groot is in vergelyking met die golflengte van sigbare lig, dat dit blou lig absorbeer en effektief as spieëls optree deur die oorblywende golflengtes te versprei. Die voorkoms van 1% volumemagnetiet in die stofdeeltjies versterk die kleur ook. Skemer duur lank nadat die son ondergegaan het en voordat dit opkom.

Soms kry die Marshemel 'n violet kleur as gevolg van ligverspreiding deur baie klein waterysdeeltjies in wolke.

Lees hierdie uitstekende referaat vir meer inligting: Die kleur van die Marshemel en die invloed daarvan op die beligting van die Marsoppervlak

Bykomende bronne:

  1. http://www.webexhibits.org/causesofcolor/14C.html
  2. http://www.mkrgeo-blog.com/what-is-the-colour-of-martian-sky/

Vir meer inligting oor Mars Twilight, sien:


'N Besonderste sonsondergang

U sou dit nie dadelik weet nie, maar daar is iets vreemds aan hierdie prentjie. Dit is 'n sonsondergang, ja, maar let op die blos van kleur reg bokant die son. Dit is blou. En as jy opkyk, vervaag die blou in 'n flou roos of pienk kleur.

Dink nou aan die sonsondergange wat u gesien het, hoe gereeld die lug goud of oranje, soms pienk, rooi kan word, maar as u opkyk, weg van die ondergaande son, vervaag die kleure na 'n ligte skemerblou? Dit is selde dat 'n sonsondergang in blou gedoop word.

Hierdie foto is dus 'n raaisel: dit is blou waar die rooi moet wees en rooi waar die blou moet wees. Hoekom?

Omdat ons nie op aarde is nie. Dit is 'n Mars-sonsondergang. Op 19 Mei 2005 het die kamera op NASA se klein robot, die dwarsbalk met die naam Spirit, hierdie foto geneem terwyl hy in die Gusev-krater op Mars gesit het. Die persverklaring, NASA, het die foto geknip, "omstreeks 6:07 die aand van die Rover se 489ste Marsdag."

Klaarblyklik het Mars heeltyd blou sonsondergange. Aarde nie.

NASA gee toe dat daar 'n kleurfilter op die kamera van Spirit is wat die kleure effens oordryf, maar hulle sê dat die blues wat jy hier sien 'soortgelyk is aan wat 'n mens sou sien' op Mars. Nie soseer die pienke nie. Pienke is effens meer uitgesproke op hierdie foto's, maar die blues is ware kleure.

Hier is ons vraag: waarom is die sonsondergange van die Mars blou?

Die lug op Mars verskil van die lug op aarde

Op die aarde is die lug meestal stikstof en suurstof. Ons het ook vog, stofdeeltjies, rook, aërosols, stuifmeel, sout uit die see. Die atmosfeer op aarde is digter - wat beteken dat daar meer molekules per kubieke duim in ons lug is.

Marslug daarenteen is baie, baie dunner, ongeveer 1 persent die digtheid van die lug op Aarde, plus die gasse is anders: hulle het CO2, stikstof en argon, maar die belangrikste, sê Mark Lemmon, medeprofessor in planetêre wetenskappe aan die Texas A&M Universiteit, lug op Mars is ryk aan tienerige, tienerige stofdeeltjies. Hulle stof is kleiner as ons stof, en hulle het meer daarvan in die Marshemel. Stof is die sleutel tot die rede waarom die twee sonsondergange anders lyk, dus sal ons die stof van Mars bewaak.

Lig versprei anders op Mars as op aarde

Kom ons staan ​​teenoor die son op Mars. Dit is vroeg in die aand. Die son sak. Lig stroom na ons oë en beweeg deur die stowwerige lug. Wat gebeur?

Sonskyn bevat, soos u weet, baie verskillende golflengtes van lig. As u 'n ligstraal in 'n prisma vang (Newton het dit gedoen), breek dit in 'n reënboog van kleure - rooi, viooltjies, blues. As die sonskyn op Mars die wolke fyn stof wat deur die lug dryf, tref, breek dit ook in verskillende kleure. Marsstof is presies die regte grootte om die blou golflengtes van lig op te neem en rooi golflengtes oor die lug te versprei. Daarom, as u op Mars staan ​​en wegkyk van die ondergaande son, is die grootste deel van die lug rooskleurig, pienk en met verskillende skakerings van rooi.

Maar kyk nou reguit na die ondergaande son. Op Mars, die ligstrale wat na u toe stroom, nadat hulle hul rooi golwe verloor het, wys die golflengtes wat nie verstrooi het nie. Daardie oorblywende lig is oorwegend blou. As jy dus reguit na die son op Mars kyk, sien jy 'n waas van blou. Kyk weg van die son af, en die lig is rooi.

Dit is presies die teenoorgestelde op aarde.

Hier, wanneer die sonskyn ons atmosfeer tref, is die golwe wat strooi blou van kleur. Daarom is ons lug oral blou - behalwe as ons reguit na die ondergaande son kyk. Daar ontbreek die blou lig, dus die oorblywende golflengtes oorheers, en dit is meestal die rooi, die goud, die lemoene.

Ons atmosfeer verstrooi blou Mars se atmosfeer strooi rooi uit.

Ons sonsondergange is rooi. Mars se sonsondergange is blou.

Dit is omdat ons lug verskil van Mars se lug.

Wat van daardie blou stralekrans rondom die son?

Kyk na hierdie kort animasie van NASA. Genaamd 'Ek droom van 'n blou sonsondergang', is 'n rekonstruksie van stilfoto's, waar u 'n helderblou stralekrans rondom die son kan sien terwyl dit na die horison sak. Waarom is daardie stralekrans daar?

Volgens professor Lemmon, wanneer sonskyn die stof van die Mars tref, wip die blou lig nie ver nie. Dit hou naby die stof en sit op kort afstand rond. Daarom, as daar 'n stofstorm aan die horison is (en dit is wat blykbaar in die video gebeur), val die gebied rondom die son baie blou lig vas, en dit lyk asof die son blou skyn.

Rooi lig, soos ons gesê het, ricochets baie verder af, so in die video is die rooierige kolle 'n entjie van die son af, die blou is naby geleë.

Die punt daarvan is dat as u op Mars uitkamp en 'n intense blou sonsondergang sien soos in die video, moet u seker maak dat die wind nie in u rigting waai nie, want die sandstorm kan oor 'n paar uur tent af. (U het onthou om 'n tent saam te bring, nee?)


Marsbries was vroeër 'n reddende genade vir die Mars-rovers wat op sonkrag beweeg, en het opgehoopte stof weggevoer en die rovers in staat gestel om te herlaai en terug te keer na die wetenskap. Dit is Opportunity in 2014.

In 1971 was wetenskaplikes gretig vir hul eerste orbitale siening van Mars. Maar toe Mariner 9 in 'n baan aankom, is die Rooi Planeet verswelg deur 'n wêreldwye stofstorm wat 'n maand lank die grootste deel van die oppervlak verberg het. Toe die stof gaan lê, kry geoloë 'n gedetailleerde uitsig oor die oppervlak van die Mars, insluitend die eerste glimp van ou rivierlope wat in die droë en stowwerige landskap uitgekap is.


Veroorsaak Mars-stofstorms die misterieuse sterretjielig?

Vanuit die Noordelike Halfrond, in die weke en maande rondom die ewening, kan jy elke aand weswaarts kyk nadat ware duisternis in die rigting van 'n geheimsinnige wasige ligpiramide gekom het. Dit word die sterretjie-lig genoem, en jy kan dit vanaf die Suidelike Halfrond ook sien, op hierdie tyd van die jaar, sou jy oos kyk voor dagbreek. Hierdie vreemde kolom van wasige lig kan baie helder en opvallend wees in donker lug, veral vanaf breedtegrade nader aan die ewenaar, soos dié in die suide van die VS Verder noord of suid, die lig lyk flouer, maar dit kan nog steeds opgespoor word teen 'n donker lug agtergrond. Hierdie geheimsinnige lig staan ​​al lank bekend as sonlig wat weerkaats van stofkorrels wat in die vlak van ons sonnestelsel beweeg. Asteroïdes en komete is vermoedelik die bron daarvan. Maar op 9 Maart 2021 het wetenskaplikes wat met die Juno-ruimtetuig werk en nou om Jupiter wentel, 'n ernstige ontdekking deur Juno aangekondig wat voorgestel het dat stofstorms van Mars die bron van die sterreteken is.

Die wetenskaplikes het in 'n verklaring gesê dat 'n instrument aan boord van Juno stofdeeltjies aan die lig gebring het wat tydens die reis van die aarde na Jupiter in die ruimtetuig toegeslaan het ná die lansering van die aarde in 2011. Met die impak kon hulle die verspreiding van die stof vir die eerste keer opspoor, en hulle het gevind dat dit in 'n byna sirkelvormige band rondom die son lê. Die binnekant van hierdie stofwolk eindig op die aarde, het hierdie wetenskaplikes gesê, omdat die aarde se swaartekrag al die stof wat daar naby kom, opsuig. Die buitenste rand van die stofband gaan na ongeveer 2 astronomiese eenhede, oftewel AU (dit wil sê 2 aarde-tot-son-eenhede van afstand). Die stofband eindig net anderkant Mars. Hierdie feit het wetenskaplikes 'n idee gegee dat die stof kan voortspruit uit die wêreldwye stofstorms wat Mars en die oppervlak gereeld verswelg. John Leif Jørgensen van die Tegniese Universiteit van Denemarke, wat die instrumentasie ontwerp het om Juno hierdie stof op te spoor, het in 'n verklaring gesê:

& # 8230 die natuurlike gedagte is dat Mars 'n bron van hierdie stof is.

Hierdie wetenskaplikes het eers laat in 2020 hul werk aanlyn gepubliseer, in die ewekniebeoordeelde Tydskrif vir geofisiese navorsing: planete. Jørgensen het gesê:

Ek het nooit gedink ons ​​sou interplanetêre stof soek nie.

Kyk op EarthSky Community Photos. | Caroline Haldeman het hierdie wonderlike beeld van Flagstaff, Arizona, op 11 Januarie 2021 vasgelê. Die wazige piramide aan die linkerkant is die sterretjielig en dit is die sonlig wat stofkorrels weerspieël, moontlik vanaf Mars! Die wasige boog aan die regterkant is glad nie waas nie. Dit is die gesamentlike lig van miljarde sterre: die sterreband van ons Melkwegstelsel. Terloops, hierdie beeld is deel van 'n video wat Caroline gemaak het, wat u hier kan sien. Dankie, Caroline! Kyk op EarthSky Community Photos. | Dit gebeur so dat jy nou Mars en die sterretjielig in dieselfde deel of die lug kan sien as jy in die Noordelike Halfrond is. Christin Nelson het hierdie beeld van die lig op 5 Maart 2021 by Deadman Pass Road, Death Valley, Kalifornië, vasgevang. Sien jy dit? Dit is die flou ligkegel aan die regterkant. Christin het geskryf: & # 8220 Ek het na 'n dagkamp naby Death Valley uitgegaan en was gelukkig genoeg om die sterretjielig na sononder te vang. Nadat ek by die huis gekom het en EarthSky gelees het om die verbinding met Mars en die Pleiades te sien, het ek besluit om my foto's te kontroleer en sou dit nie weet nie, dit is ook daar. Die sterreteken lig daarop. :) & # 8221 Dankie, Christin!

Jørgensen en Jack Connerney, 'n ander Juno-sendingwetenskaplike, het opgemerk dat die meeste stofstoot tussen die aarde en die asteroïde gordel aangeteken is, met gapings in die verspreiding wat verband hou met die invloed van Jupiter se swaartekrag. Hulle verklaring lui:

& # 8230 dit was 'n radikale openbaring. Voorheen kon wetenskaplikes nie die verspreiding van hierdie stofdeeltjies in die ruimte meet nie. Toegewyde stofverklikkers het beperkte opvangareas gehad en dus 'n beperkte sensitiwiteit vir 'n yl hoeveelheid stof. Hulle tel meestal die meer volop en kleiner stofdeeltjies uit die interstellêre ruimte. Ter vergelyking, Juno se uitgestrekte sonpanele het 1 000 keer meer opvangarea as die meeste stofverklikkers.

Hierdie wetenskaplikes het gesê dat die invloed van Jupiter se swaartekrag as 'n versperring dien en voorkom dat stofdeeltjies vanaf die binneste sonnestelsel in die diep ruimte kruis. Dieselfde verskynsel, bekend as orbitale resonansie, werk ook andersom, waar dit stof wat in die diep ruimte ontstaan ​​in die binneste sonnestelsel blokkeer.

Waarom is hierdie wetenskaplikes vol vertroue dat stof van Mars en stof die bron van die sterreteken is? Hulle verklaring het verduidelik:

Die navorsers het 'n rekenaarmodel ontwikkel om die lig wat deur die stofwolk weerkaats word te voorspel, versprei deur gravitasie-interaksie met Jupiter wat die stof in 'n dikker skyf verstrooi. Die verstrooiing hang slegs van twee hoeveelhede af: die stofhelling tot die ekliptika en die wentel-eksentrisiteit daarvan. Toe die navorsers die orbitale elemente van Mars ingeprop het, het die verspreiding die tell-handtekening van die variasie van zodiacale lig naby die ekliptika akkuraat voorspel.

Dit is volgens my 'n bevestiging dat ons presies weet hoe hierdie deeltjies in ons sonnestelsel wentel en waar dit vandaan kom.

'N Stilbeeld van die video boaan, wat wys hoe die verspreiding van stofkorrels in ons sonnestelsel en die bron van die geheimsinnige sterretjielig ooreenstem met die wentelbaan van Mars. Beeld via NASA.

Die navorsers het egter gewaarsku dat hulle nog nie kan verduidelik hoe die stof die greep van die Mars se swaartekrag kon vryspring nie. Hulle het gesê dat hulle hoop dat ander wetenskaplikes hulle sal help.

Die navorsers merk op dat die vind van die ware verspreiding en digtheid van stofdeeltjies in die sonnestelsel ingenieurs sal help om ruimtetuigmateriaal te ontwerp wat beter stofweerstand kan weerstaan.

Intussen het ons op aarde nog 'n ander rede om op 'n helder Maartaand onder 'n donker lug te staan ​​en weswaarts te kyk. Terwyl ons na die skoonheid van die sterretjielig kyk, kan ons ook die bron daarvan voorstel as die rooi stof wat in groot stofstorms oor die oppervlak van Mars waai!

Kortom: Die sterretjielig is 'n vreemde piramide van lig wat strek vanaf die oostelike of westelike horison voor dagbreek of as die ware duisternis val. Dit is bekend dat dit spruit uit stof wat in die sonnestelsel beweeg. Die Juno-ruimtetuig het bevind dat Mars die stofbron kan wees. REGSTELLING TOEGEVOEG OP 11 MAART 2021: Die oorspronklike artikel het gesê dat die baan van Mars & # 8217; s meer sirkelvormig is as die van die aarde. Dit is verkeerd. Die baan van die aarde is meer sirkelvormig as dié van Mars. Ons dank aan die deeglike leser James Machin wat hierdie fout gewys het.


Hier is die rede waarom die naghemel donker is al skyn daar miljoene sterre op ons pad

Daar is baie sterre daarbuite - na raming 70 miljard biljoen. Met soveel sterre wat op ons pad straal, lyk dit net logies dat die naghemel so helder soos dag sal wees.

Dit is die kern van die sogenaamde donker naghemelparadoks, ook bekend as Olbers se paradoks na die Duitse sterrekundige Heinrich Wilhelm Matthias Olbers (1758-1840).


Die verste oog van die heelal ooit, geneem deur die Hubble-ruimteteleskoop. Selfs met hierdie uiterste vergroting is daar steeds groot gapings tussen sterrestelsels sigbaar.

Al was Olbers die eerste wat die paradoks formeel beskryf het, lê die krediet vir die oplossing daarvan in 1823 elders. Sommige sê dat dit die eerste keer in 1901 deur die Britse fisikus Lord Kelvin (1824-1907) opgelos is. Maar volgens die webwerf van die American Museum of Natural History kom die eerste aanneemlike verklaring vir die paradoks in Eureka: A Prose Poem, 'n opstel uit 1848 deur Edgar Allen Poe.

Die heelal is miskien oneindig groot, het hy gedink, maar daar is nog nie genoeg tyd sedert die heelal begin het vir sterlig, wat met die snelheid van die lig beweeg, om ons vanuit die verste uithoeke van die ruimte te bereik nie.

Dit blyk verbasend te wees naby die verklaring wat die huidige sterrekundiges gee.

"Terwyl ons uitkyk, sien ons terug in die tyd, en teen die tyd dat ons 12 miljard jaar terug sien, is die heelal net 'n paar miljard jaar oud en is daar nie dinge wat ons kan sien nie," het dr. Jay. M. Pasachoff, professor in sterrekunde aan Williams College in Williamstown, Massachusetts, en mede-outeur van The Cosmos: Astronomy in the New Millennium, het aan The Huffington Post gesê. "Die belangrikste oplossing vir Olbers se paradoks is dat die heelal nie oud genoeg is vir sterre en sterrestelsels om ons siening te vul as ons na buite kyk nie."

Of, soos dr. Anil Chandra Seth, assistent professor in fisika en sterrekunde aan die Universiteit van Utah in Salt Lake City, in 'n e-pos aan The Huffington Post gesê het: "Daar is 'n paar redes waarom die lug nie helder is nie. Eerstens is die die heelal besig is om uit te brei en 'n eindige ouderdom het, beteken dit dat ons sterrestelsels nie oneindig ver kan sien nie (selfs al is die heelal oneindig). Die uitbreiding beteken ook dat lig energie verloor as dit beweeg. "

Benewens hierdie twee redes, het dr. Seth gesê dat die lig wat al die sterre uitstraal opgeneem word deur interstellêre stof in die melkweg, die sterrestelsel wat ons sonnestelsel bevat.

'As dit nie stof was nie,' het hy gesê, 'sou die Melkweg baie helderder in die lug wees.'

Nog 'n rede waarom die naghemel meestal donker is, het te make met die ongevoeligheid van ons oë vir die golflengtes van die lig wat die aarde bereik vanaf die verste sterre.

Omdat hierdie sterre baie vinnig van ons af wegjaag, word hul lig 'rooi verskuif' na langer golflengtes - op dieselfde manier as dat die geluid van 'n ambulans se sirene 'n laer toonhoogte het as die ambulans van ons af wegjaag as as dit op ons afstuur.

Uiteindelik, soos Pasachoff en sy medeskrywer dit in The Cosmos stel, bevraagteken die vraag waarom die naghemel donker is in plaas van lig tot 'ongelooflike interessante moontlike gevolgtrekkings rakende die aard van die heelal. Die volgende keer as u vriende ontsag het oor die skoonheid van die sterre, wys ook op die diepgaande implikasies van die duisternis! "


Die rooi kleur van Mars is net millimeter dik

Hierdie sandduin, bekend as Dingo Gap, is in 2014 deur Mars Curiosity oorgesteek. [+] effens 'wit gebalanseerd' in teenstelling met 'n regte kleur, wat die verskille in die samestellings en intrinsieke kleure van die funksies en gesteentes op die oppervlak duideliker laat sien.

As ons vanuit die ruimte na ons planeet Aarde kyk, sien ons 'n magdom verskillende kleure. Die lug self is blou, aangesien die atmosfeer verkieslik blou lig met korter golflengte in alle rigtings uitstrooi, en dit gee ons atmosfeer 'n kenmerkende kleur. Die oseane self is blou, aangesien watermolekules beter is om rooi lig met 'n langer golflengte te absorbeer as blou lig. Intussen lyk die vastelande bruin of groen, afhangend van die plantegroei (of die gebrek daaraan) wat daar groei, terwyl die yskappe en wolke altyd wit lyk.

Maar op Mars oorheers een kleur: rooi. Die grond is rooi: oral rooi. Die laaglande is rooi die hooglande is rooi die opgedroogde rivierlope is rooi die sandduine is rooi dis alles rooi. Die atmosfeer self is ook rooi op elke plek waar ons dit kan meet. Die enigste uitsondering blyk die yskappe en wolke te wees, wat wit is, alhoewel met 'n rooierige tint soos dit vanaf die aarde waargeneem word. Nogtans verrassend is die "rooiheid" van Mars ongelooflik vlak as jy net die kleinste bietjie onder die oppervlak grawe, verdwyn die rooiheid. Hier is die wetenskaplike verhaal agter net wat die rooi planeet so rooi maak.

Mars, saam met sy dun atmosfeer, soos in die 1970's van die Viking-baan gefotografeer. Die . [+] helderrooi atmosfeer is te wyte aan die teenwoordigheid van Marsstof in die atmosfeer, en die samestelling van Mars-gesteentes is vir die eerste keer deur die Vikinglanders ontdek.

Uit die ruimte kan die rooi voorkoms van Mars nie ontken word nie. Vir al die opgetekende geskiedenis in 'n wye verskeidenheid tale was die rooiheid van Mars die belangrikste kenmerk. Mangala, die Sanskrit-woord vir Mars, is rooi. Har decher, sy antieke naam in Egipties, beteken letterlik 'rooi'. En namate ons die ruimtetydperk gevorder het, toon foto's wat die oppervlak van die atmosfeer onderskei, duidelik dat die lug bokant Mars self 'n intrinsiek rooi kleur het.

In die aarde se atmosfeer oorheers die verspreiding van Rayleigh, wat blou lig in alle rigtings gooi, terwyl die rooi lig relatief ongestoord beweeg. Die atmosfeer van Mars is egter net 0,7% so dik soos die aarde s'n, wat die verspreiding van Rayleigh vanuit die gasmolekules in Mars se atmosfeer 'n weglaatbare effek maak. In plaas daarvan oorheers stofdeeltjies in die Mars-atmosfeer op (waarskynlik) twee maniere:

Die ongefilterde waarheid agter menslike magnetisme, entstowwe en COVID-19

Uitgelê: Waarom hierdie week se 'Strawberry Moon' so laag, so laat en so helder sal wees

Mars, Venus en 'n 'Super Solstice Strawberry Moon' -vonkel in skemer: wat jy hierdie week in die naghemel kan sien

  • groter absorpsie by kort optiese golflengtes (400-600 nm) as by langer (600+ nm) golflengtes,
  • en dat groter stofdeeltjies (

In vergelyking met die bestraling wat op die aarde se oppervlak ontvang word, is die lig wat op die oppervlak van Mars ontvang word. [+] ernstig onderdruk in korter (blouer) golflengtes. Dit stem ooreen met klein hematietstofdeeltjies wat in die Mars-atmosfeer opgeskort word, met die dekking wat toeneem met verhoogde stofdigtheid.

J.F. Bell III, D. Savransky, en amp M.J. Wolff, JGR Planets, 111, E12 (2006)

As u die opgeskortde atmosferiese stof in detail op Mars bekyk en vra: 'Hoe is dit,' is die antwoord ongelooflik insiggewend. Net deur na die spektrale eienskappe daarvan te kyk - of "hoe dit die lig beïnvloed", kan ons sien dat die stof baie ooreenstem met die streke op Mars wat:

  • is baie reflektief,
  • helder grondafsettings voorstel,
  • en is ryk aan yster: d.w.s. met groot hoeveelhede ysteroksiede.

As ons die stof in detail bekyk, veral met die OMEGA-instrument op die Mars Express-missie van ESA, kom ons agter dat die algemeenste soort stof afkomstig is van nanokristalliese rooi hematiet, met die chemiese formule α-Fe2O3. Die deeltjies waaruit hierdie hematiet bestaan, is klein: tussen ongeveer 3 en 45 mikron in deursnee. Dit is die regte grootte en samestelling, sodat die vinnige Marswinde, wat gewoonlik teen snelhede waai

Vee groot hoeveelhede stof voortdurend tot 100 km / u in die atmosfeer, waar dit redelik goed gemeng bly, selfs as daar geen stofstorms is nie.

Dieselfde panoramiese saamgestelde beeld, geneem deur Opportunity, met twee verskillende kleure. [+] opdragte. Die boonste prentjie is in 'regte kleur', soos menslike oë dit vir Mars sien, terwyl die onderkant in vals kleur is vir kleurkontras.

NASA / JPL-Caltech / Cornell / Arizona State Univ.

As ons na die Marsoppervlak self kyk, word die verhaal egter baie interessanter. Vandat ons die Marsoppervlak in detail begin ondersoek het - eers vanaf missies en later landers en rovers - het ons opgemerk dat die oppervlakkenmerke mettertyd sou verander. In die besonder sou ons sien dat daar donkerder en helderder gebiede was, en dat die donker gebiede in 'n bepaalde patroon sou ontwikkel:

  • hulle sal donker begin,
  • hulle word bedek met stof wat ons vermoed uit die helderder gebiede kom,
  • en dan sou hulle weer weer donker word.

Ons het lank nie geweet hoekom nie, totdat ons opgemerk het dat die donker areas wat verander almal 'n paar dinge gemeen het, veral in vergelyking met die donker areas wat nie verander het nie. In die besonder het die donker gebiede wat met verloop van tyd verander het, relatief laer hoogtes en kleiner hellings gehad, en was omring deur helderder gebiede. Daarenteen het die hoërliggende, steiler skuins en baie groot donker gebiede mettertyd nie so verander nie.

Op Mars hou kaal-rotsstrukture die hitte baie beter vas as sandagtige strukture, wat beteken. [+] sal snags helderder vertoon as dit in die infrarooi gekyk word. 'N Verskeidenheid rotssoorte en kleure kan gesien word, aangesien stof baie beter aan ander oppervlaktes kleef as ander. Van naby is dit baie duidelik dat Mars nie 'n eenvormige planeet is nie.

NASA / JPL-Caltech / MSSS, Mars Curiosity Rover

Dit was 'n duo wetenskaplikes - waarvan Carl Sagan een was - wat die oplossing verras het: Mars is bedek met 'n laag van hierdie dun, sanderige stof wat deur winde dwarsoor die Marsoppervlak gedryf word. Hierdie sand word van gebied tot gebied geblaas, maar die stof is die maklikste om:

  • reis kort afstande,
  • reis van hoër tot laer hoogtes of na vergelykbare hoogtes, eerder as tot baie hoër hoogtes,
  • en om af te waai van gebiede met steiler hellings, in teenstelling met gebiede met vlakker hellings.

Met ander woorde, die rooi stof wat die kleurpalet van Mars oorheers, is net vel diep. Dit is in hierdie geval nie eens 'n poëtiese wending nie: die grootste deel van Mars word bedek met 'n stoflaag wat net 'n paar millimeter dik is! Selfs in die streek waar die stof die dikste is - die groot plato bekend as die Tharsis-streek, wat bestaan ​​uit drie baie groot vulkane wat pas van Olympus Mons (wat in die noordweste van die plato verskyn) verreken het - is dit na raming ongeveer 2 meter (

Mars Orbiter Laser Hoogtemeter (MOLA) gekleurde topografiese kaart van die westelike halfrond van Mars,. [+] wat die streke Tharsis en Valles Marineris vertoon. Die impakbekken Argyre is regs onder, met die laagland Chryse Planitia regs (oos) van die Tharsis-streek.

NASA / JPL-Caltech / Arizona State University

U kan dan na hierdie feite kyk en u die volgende afvra: het ons 'n topografiese kaart van Mars en 'n kaart van die ferro-oksiede op Mars, en korreleer hierdie kaarte enigsins met mekaar?

Dit is 'n slim gedagte en een wat ons binne 'n sekonde sal bekyk, maar "ysteroksied" beteken nie noodwendig "rooi Marsstof" soos u dink nie. Eerstens is ysteroksiede oral op die planeet aanwesig:

  • binne die kors,
  • gevind in lawa-uitvloei,
  • en in die Marsstof wat geoksideer is deur reaksies met die atmosfeer.

Aangesien die atmosfeer, selfs vandag nog, aansienlike hoeveelhede koolstofdioksied en water bevat, is daar 'n maklik beskikbare bron van suurstof om enige ysterryke materiaal te oksideer wat dit na die oppervlak bring: waar dit met die atmosfeer in aanraking kom.

As gevolg hiervan, as ons na 'n ysteroksiedkaart van Mars kyk - weer gemaak deur die fantastiese OMEGA-instrument aan boord van ESA se Mars Express - vind ons dat ja, die ysteroksiede is oral, maar die oorvloed is die hoogste in die noorde en midde. breedtegrade en die laagste oor die suidelike breedtegrade.

Hierdie kaart, deur die OMEGA-instrument op ESA se Mars Express, teken die verspreiding van ysteroksiede, a. [+] minerale fase van yster, oor die oppervlak van Mars. Ferri-oksiede ('n ysteroksied) kom oral op die planeet voor: binne die grootste kors, vloei die lawa uit en die stof word geoksideer deur chemiese reaksies met die Mars-atmosfeer. Blouer kleure verteenwoordig laer hoeveelhede ferrooksied, rooier kleure is hoër.

ESA / CNES / CNRS / IAS / Université Paris-Sud, Orsay Agtergrondfoto: NASA MOLA

Aan die ander kant wys die topografie van Mars dat die hoogte van die rooi planeet op 'n interessante manier oor die oppervlak verskil, en op 'n manier wat net gedeeltelik gekorreleer is met die oorvloed van ysteroksiede. Die suidelike halfrond is oorwegend baie hoër as die laaglande in die noorde. Die grootste verhogings kom voor in die Tharsis-gebied met 'n yster-oksied, maar in die laaglande ten ooste daarvan daal die oorvloed van ysteroksiede.

Wat u moet besef, is dat die rooi hematietvorm van ysteroksied, wat moontlik die skuldige is vir die "rooiheid" van Mars, nie die enigste vorm van ysteroksied is nie. Daar is ook magnetiet: Fe3O4, wat swart van kleur is in plaas van rooi. Alhoewel die wêreldtopografie van Mars blykbaar 'n rol speel in die oorvloed van ysteroksied, is dit duidelik nie die enigste faktor wat speel nie, en is dit miskien nie eens die primêre faktor om Mars se kleur te bepaal nie.

Die Mars Orbiter Laser Altimeter (MOLA) -instrument, deel van Mars Global Surveyor, het meer as 200 versamel. [+] miljoen laserhoogtemetermetings tydens die konstruksie van hierdie topografiese kaart van Mars. Die Tharsis-streek, middel-links, is die hoogste gebied op die planeet, terwyl die laaglande in blou vertoon. Let op die veel laer hoogtepunt van die noordelike halfrond in vergelyking met die suidelike.

Mars Global Surveyor MOLA-span

Wat ons dink plaasvind - en dit is al jare lank 'n konsekwente beeld - is dat daar 'n helder, wêreldwyd verspreide, wêreldwye homogene stel stof is wat in die atmosfeer opgeswaai word en daar bly. Daardie stof hang basies in die dun atmosfeer van Mars, en hoewel gebeure soos stofstorms die konsentrasie kan verhoog, daal dit nooit tot 'n onbeduidende lae waarde nie. Mars se atmosfeer is altyd ryk aan hierdie stof dat stof die atmosfeer se kleur gee, maar die kleurkenmerke van Mars se oppervlak is glad nie eenvormig nie.

Die "afsakking van atmosferiese stof" is slegs een faktor om die oppervlakkleur van verskillende streke van Mars te bepaal. Dit is iets wat ons baie goed by ons landers en rovers geleer het: Mars is glad nie 'n eenvormige rooi kleur nie. Trouens, die oppervlak self is meer oranje in die kleur van die botterskorsie, en dit lyk asof verskillende rotsagtige voorwerpe en afsettings op die oppervlak verskillende kleure het: bruin, goudkleurig, bruin en selfs groenerig of geel, afhangende van watter minerale maak daardie deposito's op.

Hierdie foto, geneem deur Mars Pathfinder van sy Sojourner-rover, toon verskillende kleure. Die swerwer s'n. [+] wiele is rooierig as gevolg van die Marshematiet, die versteurde grond is baie donkerder onder. Rotse van verskillende intrinsieke kleure kan gesien word, maar ook die rol wat die sonlig se hoek speel, kan ook duidelik gesien word.

Een vraag wat nog ondersoek word, is die presiese meganisme waardeur hierdie rooi hematietdeeltjies gevorm word. Alhoewel daar baie idees is wat molekulêre suurstof behels, word dit slegs in klein, klein hoeveelhede aangetref deur die fotodissosiasie van water. Reaksies waarby water of hoë temperature betrokke is, is moontlik, maar dit is termodinamies ongunstig.

My twee gunsteling moontlikhede is reaksies met waterstofperoksied (H2O2), wat van nature op Mars in lae hoeveelhede voorkom, maar 'n baie sterk oksidant is. Die feit dat ons groot hoeveelhede α-Fe sien2O3 maar geen gehidreerde yster-minerale minerale kan 'n aanduiding wees van hierdie weg nie.

Alternatiewelik kan ons hematiet kry bloot deur 'n suiwer fisiese proses: erosie. As u magnetietpoeier, kwartsand en kwartsstof saam meng en dit in 'n fles laat tuimel, skakel sommige van die magnetiet in hematiet om. In die besonder sal 'n "swart" mengsel (gedomineer deur magnetiet) rooi vertoon, aangesien die kwarts gebreek word, wat suurstofatome blootstel wat aan die gebreekte magnetietbindings heg, wat hematiet vorm. Miskien is die begrip "water is verantwoordelik vir ferro-oksiede" tog 'n letterlike rooi haring.

Die begin van die 2018 stofstorm wat gelei het tot die ondergang van NASA se Opportunity Rover. Selfs hieruit. [+] growwe kaart, is dit duidelik dat die stof rooi van kleur is en die atmosfeer ernstig rooi maak, aangesien groter hoeveelhede stof in die Mars-atmosfeer hang.

Al met al is Mars rooi as gevolg van hematiet, wat 'n rooi vorm van ysteroksied is. Alhoewel ysteroksiede op baie plekke voorkom, is slegs die hematiet hoofsaaklik verantwoordelik vir die rooi kleur, en die klein stofdeeltjies wat in die atmosfeer hang, en wat die boonste paar millimeter tot meter van die oppervlak van Mars bedek, is heeltemal verantwoordelik vir die rooi kleur sien ons.

As ons die atmosfeer op 'n manier vir 'n lang tyd sou kon kalmeer en die stof van die Mars kon laat uitsak, sou u kon verwag dat die verspreiding van Rayleigh sou oorheers soos op aarde, en die lug blou sou word. Dit is net gedeeltelik korrek, maar omdat die atmosfeer van die Mars so dun en sag is, sal die lug baie donker lyk: amper heeltemal swart, met 'n effense blou tint daaraan. If you could successfully block out the brightness coming from the planet’s surface, you would likely be able to see some stars and up to six planets — Mercury, Venus, Earth, Jupiter, Saturn, and sometimes Uranus — even during the daytime.

Mars might be the red planet, but only a tiny, minuscule amount of it is actually red. Fortunately for us, that red part is the outermost layer of its surface, pervasive in the Martian atmosphere, and that accounts for the color we actually perceive.


Why is the moon so bright?

The moon is actually quite dim, compared to other astronomical bodies. The moon only seems bright in the night sky because it is so close to the earth and because the trees, houses, and fields around you are so dark at night. In fact, the moon is one of the least reflective objects in the solar system. The DSCOVER spacecraft captured this single photograph of the moon and the earth. Both the earth and the moon are illuminated by the same amount of sunlight coming from the same angle in this photo. As you can see in this photo, the earth is much brighter than the moon.

In general, we can see objects because they direct light into our eyes (or into cameras which record information that is later used by display screens to direct light into our eyes). There are two main ways that an object can direct light into our eyes. Either the object creates new light or it reflects light that already existed. Objects that create light tend to also reflect ambient light, so that they tend to be the brightest objects around. Examples include campfires, light bulbs, candle flames, and computer screens. In terms of astronomical bodies, stars are the main objects that create significant amounts of visible light, and therefore are some of the brightest objects in the universe. In contrast, planets and moons do not generate their own visible light*. If a planet somehow became large enough to initiate nuclear fusion and begin glowing, it would no longer be a planet. It would be a star.

Since planets and moons do not emit light, the only reason we can see them is because they reflect light from some other source. The strongest source of light in our solar system is the sun, so usually we see planets and moons because they are reflecting sunlight. The amount of sunlight incident on a moon or planet that gets reflected depends on the materials in its surface and atmosphere as well as its surface roughness. Snow, rough ice, and clouds are highly reflective. Most types of rock are not. Therefore, a planet that is covered with clouds, such as Earth or Venus, is generally brighter than a rocky moon or planet that has no atmosphere.

There are two main types of reflectivity: specular reflectivity and diffuse reflectivity. Specular reflectivity measures how much of the incoming light gets reflected by the object in the direction given by the mirror angle. In contrast, diffuse reflectivity measures how much light gets reflected in all directions. A mirror has high specular reflectivity and low diffuse reflectivity. In contrast, sand has low specular reflectivity and high diffuse reflectivity. In everyday life, we experience specular reflectivity as the perception of mirror images and glare spots on the surface of objects. We experience diffuse reflectivity as a somewhat uniform brightness and color that exists on the surface of the object and is roughly the same no matter what our viewing angle is. Many objects display significant amounts of both specular reflectivity and diffuse reflectivity. For instance, a red polished sports car looks red from all angles because of its diffuse reflectivity, while at the same time displays bright spots of glare because of its specular reflectivity. In general, roughening a surface tends to increase its diffuse reflectivity and decrease its specular reflectivity. This is true because a rough surface has many little reflecting planes all oriented differently which scatter light in many different directions. In fact, the easiest way to turn a strong specular reflector into a strong diffuse reflector is to roughen it up. For instance, take a smooth sheet of ice and scratch it up. You turn a surface that is bright only in the mirror direction of the light source into a surface that bright in all directions.

When it comes to planets and moons, the surface roughness is quite high. For this reason, their overall brightness is best described by their diffuse reflectivity. There are several ways to define and measure the diffuse reflectivity. In the context of planets and moons, the common and perhaps most useful way is to define it in terms of "bond albedo". The bond albedo is the average amount of total light scattered by the body in any direction, relative to the total amount of light that is incident. A bond albedo of 0% represents a perfectly black object and a bond albedo of 100% represents an object that scatters all of the light. The earth has a bond albedo of 31%. In contrast, the moon has a bond albedo of 12%. To bring this closer to home, the moon has the same bond albedo as old asphalt, such as is found in roads and parking lots. The bond albedo of major objects in our solar system are listed below as reported in the textbook Fundamental Planetary Science: Physics, Chemistry, and Habitability by Jack K. Lissauer and Imke de Pater.

ObjectBond Albedo
Triton85%
Venus75%
Pluto50%
Jupiter34%
Saturnus34%
Aarde31%
Neptunus31%
Uranus29%
Mars25%
Titan20%
Mercury12%
Maan12%

As this table makes clear, the moon is one of the dimmest objects in our solar system. If Triton, one of Neptune's moons, were to become the moon of the earth, then it would be about seven times brighter in the night sky than our current moon. Triton is bright because almost all of its surface is covered by several layers of rough ice. In contrast, earth's moon is so dark because it contains very little ice, snow, water, clouds, and atmosphere. The moon consists mostly of rock dust and dark rocks that are similar in composition to rocks on earth. The albedo values in the table above are averages since the albedo varies through time. For example, the number of clouds covering the earth varies from season to season. Therefore, the albedo of the earth varies a few percent throughout the year.

The perceived brightness of a planet or moon (i.e. what we see with our eyes), depends on three things: (1) the object's albedo, (2) the total amount of light that is hitting the object in the first place, and (3) the distance between the object and the eye or camera that is viewing it. Planets and moons that are closer to the sun receive much more sunlight and therefore generally have a higher perceived brightness. Also, planets and moons that are closer to the earth have more of their reflected light reach the earth and therefore generally have a higher perceived brightness as seen from earth. The moon indeed looks brighter than Venus to a human standing on earth's surface, but that's just because the moon is so close to earth.

*Note that many planets and moons can create small amounts of light through localized phenomena. Examples of such phenomena include lightning, glowing lava, and atmospheric aurora. While such phenomena can lead to stunning photos when captured by nearby spacecraft, they generate such little light that they do not contribute significantly to the brightness of the planet or moon when viewed from a distance.


Big Dust Storm Blows up on Mars (Updated)

By: Bob King June 25, 2018 16

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Will Mars soon be hidden under a veil of dust? Let's hope not. We explore the current storm and the planet's upcoming close opposition.

UPDATE (June 19, 2018): Go the end of the article for our most recent update.

UPDATE (June 14, 2018): Scroll down for a new image of the advancing dust storm.

UPDATE (June 13, 2018): Scroll down for our update on NASA's Opportunity rover.

John Boudreau captured the dust storm (intersection of the tick marks) on Mars in Mare Acidalium at 8:52 GMT on May 31, 2018. South is up in this photo and others unless noted.

Atmospheric scientists may pray for a global dust storm to blow up on Mars, but the rest of us . . . please, no! Just as the Red Planet began to inch into the evening sky, a swath of bright, yellow dust clouds lit up over the dark albedo feature Mare Acidalium at the end of May.

Within days, the gale had moved south and expanded, covering much of Sinus Meridiani, Oxia Palus, and Margaritifer Sinus and coursing the length and breadth of the sprawling Martian canyon system Valles Marineris. This is a big storm. Under the eye of NASA's Mars Reconnaissance Orbiter, it measures more than 18 million square km (7 million square miles), an area greater than the continent of North America. (But see update at the end of the article.)

While there's no way to foretell if the gale will balloon into a planet-girdling storm, NASA's Opportunity rover team has taken precautions to protect the rolling robot, which sits squarely in the storm's path in Sinus Meridiani. Science operations have been suspended to conserve power.

"A dark, perpetual night has settled over the rover's location in Mars' Perseverance Valley," reads the most recent agency press release, referring to thick clouds blowing dust in the area.

Looks wicked out there. This global map of Mars shows the growing dust storm as of June 6, 2018. The map was produced by the Mars Color Imager (MARCI) camera on NASA's Mars Reconnaissance Orbiter spacecraft. Click for a high resolution image.
NASA / JPL-Caltech / MSSS

Opportunity made it through the last bad storm in 2007, but this one’s worse. Dust blocks the sunlight used by the rover's solar panels to create the power needed to run its instruments and stay warm. Mars is no picnic. Although dust storms can limit temperature extremes — analogous to a cloudy day on Earth — the longer they last, the less power available to the rover. Batteries only last so long.

This map of the planet Mars is based on observations made by amateur astronomers. The most prominent dark features for 4-inch or larger instruments are Syrtis Major, Mare Acidalium, Mare Erythraeum, and Mare Cimmerium. The storm began in Mare Acidalium (lower left) and tracked west across Chryse and Oxia Palus, then into Sinus Meridiani.
ALPO Another perspective of the storm taken by NASA's Mars Reconnaissance Orbiter.
NASA / JPL-Caltech / Malin Space Science Systems

The good news is that NASA engineers received a transmission from Opportunity on Sunday morning, a welcome sign that despite the worsening storm, the rover still has enough battery power to communicate with ground controllers. Meanwhile, the Mars Curiosity rover is still in the clear in the opposite hemisphere, though an increase in dust is expected in the coming days.

Two mages taken by NASA's Mars Global Surveyor orbiter in 2001 show the dramatic change in the planet's appearance before and during a global dust storm. North is up.
NASA / JPL / MSSS

The current storm is significantly larger than the 2005 storm but so far pales in comparison to the global storm that wracked the Red Planet in 2001. That one began in the bright, circular feature Hellas, an ancient impact basin with a floor 9 km deep in the planet's southern hemisphere. Die

10° temperature difference between basin bottom and surface drove winds that spawned a modest storm. But on June 27th that year, the storm exploded in size, spilling out of the basin to eventually cover the entire planet.

No one's certain on exactly how a big storm gets rolling, but it appears that a positive feedback loop can turn a zephyr into a monster under the right conditions:

Before and after photos show significant changes wrought by the current storm. Dust now covers many of the dark surface markings visible earlier in May. The orange, linear feature near the center of Mars is the giant canyon system Valles Marineris — dark in May but now filled with bright dust!
Damien Peach (left) / Anthony Wesley

"One theory holds that airborne dust particles absorb sunlight and warm the Martian atmosphere in their vicinity," said Phil Christensen, planetary geologist at the University of Arizona, referring to the 2001 storm. "Warm pockets of air rush toward colder regions and generate winds. Strong winds lift more dust off the ground, which further heats the atmosphere." More heat means more energy and stronger winds, which lift even more dust into the air, amplifying a small disturbance into a large one.

This sequence of photos shows the development of the bright dust storm on Mars. It’s most obvious in the top row images. North is up.
Paul Maxson

This storm is a little different. Instead of occurring at the height of southern summer as in 2001 and 2005, it erupted in the northern hemisphere only days after the northern fall equinox. Similar to how arctic fronts descend one after another on North America during late fall and winter, multiple storm fronts parade along the north polar cap during Martian fall. Some of these can break off and head south, where they feast on warmer air and burgeon into much bigger storms.

Mars, now brighter than Sirius and a distinctive fiery hue, climbs above the tree line in the southeastern sky on June 10th. The planet rises late — around midnight local time in mid-June — and is best observed in early dawn when it stands due south on the meridian.
Bob King

From an observer's point of view, let's hope the dust settles . literally. Mars is finally coming into its own. At magnitude –1.6, it's now brighter than any star in the night sky. On Monday morning (June 11th) I easily found it in my 8×50 finderscope at sunrise and did all my observing in a blue sky. Mars's apparent diameter has swelled to nearly 18″ (arcseconds) on its way to a chunky 24.3″ when it reaches opposition on July 27th. Closest approach to the Earth occurs on July 31st at 57.6 million kilometers, its most neighborly position since the 2003 opposition.

This more detailed map created by Damian Peach is based on photographs taken during the 2005 apparition. Changes, some subtle some not, occur in the tone and shape of some dark markings due to winds that alternately cover and uncover the landscape with dust. Click for a large version.
Damian Peach

Provided the storm takes a chill pill, telescopic observers have lots to see now through fall. First off, the south polar cap is obvious, and we'll be able to watch it shrink as its dry-ice shell sublimes in the intensifying spring heat. Large, dark albedo features like Syrtis Major, Hellas, Mare Tyhrrhenum, Mare Cimmerium, Solis Lacus (the Eye of Mars), Aurorae Sinus, Sinus Meridiani, and Sinus Sabaeus can be discerned in good seeing and with practice. A red filter and magnifications of 150× and higher will help to bring out them out.

Maryland amateur Robert Bunge sketched a wealth of detail on Mars as seen through his 6-inch telescope on June 5th. The thumb-shaped feature at left is Syrtis Major. The dotted bright area at right corresponds to the dust storm.
Robert Bunge

Observers in mid-northern latitudes will have to work harder than more southerly skywatchers to get their Mars fix. The planet spends much of the summer and fall in southern Capricornus, south of declination –20°. The seeing at that elevation is rarely good, the reason I recommend observing Mars near the meridian and as often as possible, the better to catch it on those rare nights of serene seeing and fine definition.

Be aware that even if we make it past the current storm, we're not out of the woods. Summer's a comin' for the south. As carbon dioxide ice vaporizes from the southern pole cap, expect new winds to develop and a good possibility for major storms to return in August and September. If you routinely observe Mars, a dust storm will betray itself by color (yellow-orange), brightness and the plain fact that a feature you saw a few nights has seemingly disappeared. I've watched them evolve night to night — most exciting!

Resources to enhance your Mars experience:

    find out which side of Mars and what features are visible the latest photos from amateurs around the world reports based on Mars Reconnaissance Orbiter imagery

*** Dust storm update June 13, 2018:

This series of images shows simulated views of a darkening Martian sky blotting out the Sun from the point of view of NASA’s Opportunity rover, with the right side simulating Opportunity’s current view in the global dust storm (June 2018). The left starts with a blindingly bright mid-afternoon sky, with the Sun appearing bigger because of brightness. The right shows the Sun so obscured by dust it looks like a pinprick.
NASA / JPL-Caltech / TAMU

NASA engineers attempted to contact the Opportunity rover on June 12 but did not hear back probably because the charge in its batteries has dropped below 24 volts. At that point, the rover enters low power mode where everything is turned off except the mission clock. The clock is programmed to wake the computer so it can check power levels. If there's not enough, the rover goes back to sleep until the next check.

The dust cover is now extreme at Opportunity's location and has spread to cover a quarter of the planet — equal to the combined area of North America and Russia. Mission engineers believe there may not be enough sunlight to charge the batteries for the next few days. The concern is that without battery power, the rover won't be able to keep its electronics alive. To hear the replay of the NASA teleconference about Opportunity's fate held earlier today, click hier.

If there's a silver lining in this dark scenario, the increase in atmospheric temperature caused by the Sun-warmed dust along with the warming of the air with the arrival of spring will combine to moderate temperatures at Opportunity's location, keeping the rover just warm enough to survive till the dust clears.

*** Dust storm update June 14, 2018:

This set of images from NASA's Mars Reconnaissance Orbiter (MRO) shows the evolution of the dust storm (salmon-colored area) from May 31st, when the dust event was first detected, through June 11th. Rovers on the surface are indicated as icons.

*** Dust storm update June 19, 2018:

Only a few dark albedo markings still showed well on Mars when this photo was taken on June 15th at 7:49 UT. You're looking at the dark marking called Mare Cimmerium with Mare Chronium above it. Hints of Mare Tyrrhennum are seen under haze at far right. South is up.
Damian Peach / Chilescope Team

Conditions at Mars continue to worsen however the storm has not reached global proportions. For the moment, it still remains a large regional storm. Dust obscures many once prominent features including Syrtis Major, Sinus Meridiani and much of the south polar cap. The Opportunity rover is still silent and will likely remain so until the storm blows over.

Australian amateur Anthony Wesley photographed Mars on June 19th and included a reference image made using WINJUPOSto show how much dust has altered the planet's appearance. The normally prominent feature Syrtis Major is heavily obscured as is much of the south polar cap.

*** Dust storm update June 22, 2018:

Recent photos taken by Australian amateur Anthony Wesley indicate that the dust may be starting to clear. His image from June 21 still shows plenty of suspended dust, but the dark albedo features Syrtis Major and Sinus Meridiani are beginning to show through the haze. There's also a prominent dark collar along the northern border of the south polar cap around CM 330°.

Some of Mars's better-known features are beginning to show through the dust in this photo taken on June 21.8 UT. The prominent dark "thumb" is Syrtis Major.
Anthony Wesley

I finally got a good view of Mars on June 21.4 UT (CM = 171°) through a 10-inch telescope and saw part of Mare Sirenum and Mare Cimmerium, which were crossing the central meridian at the time. The polar cap, which would normally be distinct, appeared pale-white and patchy using a magnification of 254x. You could see it was there but the outline was unclear. There's plenty of time for potentially great views with opposition still more than a month away.

Two images from the NASA's Curiosity rover depict the change in the color of light illuminating the Martian surface since the dust storm engulfed Gale Crater. The left image shows the "Duluth" drill site on May 21st the right image is from June 17th. The cherry-red color in the post-storm photo is due to a couple of factors: The exposure time for the right image is nine times longer than the one on the left because of low-lighting conditions brought on by the dust. But the primary reason for the color change is the dust filters out most of the green and all of the blue light from the Sun.
NASA / JPL-Caltech / MSSS

NASA attempts to contact the Opportunity rover every day, but there's still no reply. Meanwhile, the Curiosity rover on the other hemisphere of Mars has been recording thickening dust conditions. In other news, the storm is officially a "planet-encircling" or global dust event, according to Bruce Cantor of Malin Space Science Systems, San Diego, who is deputy principal investigator of the Mars Color Imager camera on board NASA's Mars Reconnaissance Orbiter. This storm's more patchy compared to the big global storms of 1971-72 and 2001 which totally obscured the surface.

A self-portrait taken by NASA's Curiosity rover taken on Sol 2082 (June 15, 2018) at the "Duluth" drilling site. (center). A Martian dust storm has reduced sunlight and visibility at the rover's location.
NASA / JPL-Caltech / MSSS

*** Dust storm update June 25, 2018:

Ah, the good old days. These photos were taken 15 days apart and show the same hemisphere of Mars. Note how airborne dust has obscured the outlines of familiar features including Syrtis Major (dark India-shaped marking below center.) Dust also shrouds much of the south polar cap. CM = 300° on right image. South is up.
Damian Peach (left) / Christopher Go (right)

Mars remains hazy and most of the planet's dark markings show low contrast. But with patience and good seeing, observers are gradually making out a few more features. Syrtis Major and Sinus Meridiani are returning, but it appears that Mare Cimmerium has recently gone missing!

Mare Cimmerium is only visible as low contrast patches in this photo taken on June 24th. CM =238°. South is up.
Christoper Go

You can really see how dramatically the storm has altered the appearance of once prominent markings in the side-by-side panel above taken only two weeks apart. No word yet from the Opportunity rover — last contact was June 10th.

Why does Mars have planet-wide dust storms and not Earth? There are at least two factors involved: the planet's weaker gravity and its lack of oceans. Once atmospheric conditions are ripe for a storm to spark, wind-borne dust remains aloft longer because of the planet's weaker gravitational pull. Mars has no bodies of water to moisten the air. The added humidity provided by Earth's oceans helps remove dust from the lower atmosphere and slow or prevent dust storms on from crossing continents. With no oceans, Mars dust blows hither and yon.


Why Is Mars Red?

Expect to see a lot of red-orange landscapes over the next few weeks, as the Curiosity rover beams back its first photos of the rugged Martian scenery. But why is Mars red, anyway?

The simple explanation for the Red Planet's color is that its regolith, or surface material, contains lots of iron oxide — the same compound that gives blood and rust their hue. But why does Mars have so much iron, why is that iron "oxidized," and why does iron oxide look red?

It all started 4.5 billion years ago. When the solar system formed, many of the planets landed a dose of iron. Forged in the heart of long-dead stars, the heavy element swirled around in the cloud of gas and dust that gravitationally collapsed to form the sun and planets. Whereas the bulk of Earth's iron sank to its core when the planet was young and molten, NASA scientists think Mars' smaller size (and weaker gravity) allowed it to remain less differentiated. It does have an iron core, but abundant iron exists in its upper layers, also.

Plain-old iron looks shiny black. The element only takes on a reddish tinge when it has been exposed to oxygen, and enough oxygen at that for it to become iron(III) oxide, an atomic fivesome composed of two iron atoms and three oxygen atoms. So why did so much of the iron on Mars' surface oxidize, or gang up with oxygen?

In fact, the jury's still out on that one. For sure, some sort of weathering gradually rusted the iron on Mars. But did the ancient rainstorms that are thought to have occurred on a young, wet Mars rust the iron by pounding the regolith with oxygen atoms freed from water molecules? Or, did the oxidation happen gradually over billions of years, as sunlight broke down carbon dioxide and other molecules in the atmosphere, producing oxidants such as hydrogen peroxide and ozone? Or, as a group of Danish scientists suggested in 2009, have Martian dust storms slowly rusted the iron, by crumbling the quartz crystals that also exist in the regolith and leaving their oxygen-rich surfaces exposed?

Because no one yet knows the right explanation, the color of Mars is, in a sense, still a mystery. But however its surface rusted, the compound iron(III) oxide appears red because it absorbs the blue and green wavelengths of the light spectrum while reflecting the red wavelengths. [Your Color Red Could Be My Blue]

The planet's bloody tinge — visible even from millions of miles away — got it strapped with the name of the Roman god of war, while other civilizations also named the planet for what was once its main distinguishing feature. The Egyptians called it "Her Desher," meaning "the red one," while ancient Chinese astronomers went with "the fire star."

Follow Natalie Wolchover on Twitter @nattyover or Life's Little Mysteries @llmysteries. We're also on Facebook & Google+.


Martian sands move in unearthly ways

Linear sand dunes in Proctor Crater as seen by the Mars Reconnaissance Orbiter (MRO) on June 10, 2007. Image via NASA/JPL/University of Arizona.

Like Earth, Mars has sand dunes, a lot of them, but scientists are now learning that the processes involved in their formation and movement can be quite different from what happens on our own planet. A team of planetary scientists from the University of Arizona (UA) has conducted the most detailed study yet of how sands move around on Mars, and how that movement differs from sand movement in deserts on Earth.

The new research was led by Matthew Chojnacki at the Lunar and Planetary Laboratory (LPL) at UA and the peer-reviewed results were published in the current issue of the journal Geology on March 11, 2019.

The team found that processes nie involved in sand movement on Earth are very much involved in how sand gets transported on Mars, most notably large-scale features on the landscape and differences in landform surface temperature. As Chojnacki explained:

Because there are large sand dunes found in distinct regions of Mars, those are good places to look for changes … If you don’t have sand moving around, that means the surface is just sitting there, getting bombarded by ultraviolet and gamma radiation that would destroy complex molecules and any ancient Martian biosignatures.

Another stunning set of rolling sand dunes, big and small, in Proctor Crater on Mars, as seen by MRO on February 9, 2009. Image via NASA/JPL/University of Arizona.

It may seem surprising that Mars even has sand dunes, since its atmosphere is so thin – about 0.6 percent of Earth’s air pressure at sea level – but it does, and they can range from just a few feet tall to hundreds of feet in height. They have been seen from spacecraft in orbit and close-up on the ground by rovers. The sand dunes on Mars do move much more slowly, however, about two feet per Earth year (about one Martian year), while sand dunes on Earth can migrate as much as 100 feet per year. According to Chojnacki:

On Mars, there simply is not enough wind energy to move a substantial amount of material around on the surface. It might take two years on Mars to see the same movement you’d typically see in a season on Earth.

There were other questions the researchers wanted to address, such as whether the Martian sand dunes are still active today, or just relics from millions or billions of years ago when the atmosphere was thicker. As Chojnacki stated:

We wanted to know: Is the movement of sand uniform across the planet, or is it enhanced in some regions over others? We measured the rate and volume at which dunes are moving on Mars.

Sand dunes inside Victoria Crater, near the Opportunity rover landing site as seen by MRO on October 3, 2006. Image via NASA/JPL/University of Arizona. Barchan sand dunes in the Hellespontus region, as seen by MRO on March 16, 2008. Image via NASA/JPL/University of Arizona. Spotted sand dunes near the Martian north pole, as seen by MRO on April 13, 2008. The spots are where carbon dioxide ice has sublimated off the dunes. Image via NASA/JPL/University of Arizona. Frosted sand dunes near the Martian north pole, as seen by MRO on February 19, 2008. Image via NASA/JPL/University of Arizona.

In order to help figure out the causes of sand movement on Mars, the researchers used high-resolution images taken by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter (MRO). MRO has been orbiting Mars since 2006, taking thousands of detailed images of the surface all over the planet. For this particular work, the researchers mapped sand volumes, dune migration rates and heights for 54 dune fields, encompassing 495 individual dunes. Chojnacki said:

This work could not have been done without HiRISE. The data did not come just from the images, but was derived through our photogrammetry lab that I co-manage with Sarah Sutton. We have a small army of undergraduate students who work part time and build these digital terrain models that provide fine-scale topography.

What the researchers found was surprising. While there are some ancient, inactive sand dunes, there are also many still active today. They fill and sweep across craters, canyons, rifts, cracks, volcanic remnants, polar basins and plains surrounding craters. Mars’ atmosphere may be thin, but it is still good at transporting sand grains across a diverse array of landscapes.

There are three regions that have the most activity: Syrtis Major Planum, a dark area larger than Arizona Hellespontus Montes, a mountain range about two-thirds the length of the Cascades and Olympia Undae (North Polar Erg), a sea of sand surrounding the north polar ice cap. What makes these areas unique is that they experience conditions not known to affect terrestrial sand dunes: stark transitions in topography and surface temperatures. According to Chojnacki:

Those are not factors you would find in terrestrial geology. On Earth, the factors at work are different from Mars. For example, ground water near the surface or plants growing in the area retard dune sand movement.

Close-up view of a sand dune called Namib Dune, part of the Bagnold Dunes near Mount Sharp in Gale Crater, as seen by the Curiosity rover on December 18, 2015. Namib is about 16 feet (5 meters) tall. Image via NASA/JPL-Caltech/MSSS. Another view from Curiosity of part of the Bagnold Dunes near Mount Sharp in Gale Crater. Image via NASA/JPL-Caltech/MSSS.

The researchers also found that small basins filled with bright dust had higher rates of sand movement as well, as Chojnacki noted:

A bright basin reflects the sunlight and heats up the air above much more quickly than the surrounding areas, where the ground is dark, so the air will move up the basin toward the basin rim, driving the wind, and with it, the sand.

NASA’s Curiosity rover has studied a field of dunes in Gale Crater up close, called the Bagnold Dunes, and the Mars Odyssey orbiter also recently saw an unusual hexagonal-shaped dune field created by the Martian winds.

Mars is often referred to as a desert world, for good reason. Sand dunes flow across the surface just as they do in deserts on Earth, like the Sahara. In some locations, you could swear you were in the American Southwest, with the scenery being uncannily similar-looking. But Mars is not Earth, and different geological and other environmental factors play a key role in how sand dunes behave, and differ, on both worlds.

Bottom line: This new study shows how sand dunes on Mars – while visually and aesthetically similar to their earthly counterparts – can differ significantly in how they are formed and how they migrate across the surface of this cold desert world.