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Nitrogen oxides on Mars

1965; Elsevier BV; Volume: 13; Issue: 1 Linguagem: Inglês

10.1016/0032-0633(65)90134-0

1873-5088

Carl Sagan, Philip L. Hanst, A. T. Young,

Planetary Science and Exploration

In a series of recent papers, Kiess and collaborators have announced the identification of nitrogen peroxide on Mars and have attempted to interpret a wide range of Martian phenomena in terms of nitrogen oxides. Analyses of observations at a variety of wavelengths in the present paper, and previously by Sinton, Spinrad and Moroz, place a firm upper limit on the Martian NO2 abundance of 1 mm-atm. Nitrogen dioxide is a highly photolabile gas and will be photodissociated by visible and ultraviolet radiation on Mars. The photochemical equilibria of nitrogen oxides on Mars have been computed from the observational upper limits on the NO and O2 abundances. The same procedure gives consistent results for the Earth, at locales free from urban pollution. The corresponding theoretical upper limit to the abundance of NO2 on Mars is 1 mm-atm, when reactions with water are neglected. When reactions with water are considered, the NO2 abundance is further diminished. These low abundances are inadequate to account for the Martian observables discussed by Kiess et al. The one Martian phenomenon in which nitrogen peroxide may play a role is the blue haze, where 1 mm-atm may help to explain not only the general blue and violet opacity, but also the dependence of the opacity on time and position. The required abundance of NO must then be >50 cm-atm. Kiess et al. have expressed the opinion that the quantity of nitrogen peroxide on Mars is so large as to exclude indigenous life. It is of interest to note that a typical value for the abundance of NO2 over the city of Los Angeles exceeds the corresponding value for Mars. B Pядe HeдaBHич HayчHыч cTaTeй Киcc и eгo coTPyдHики зaяBили o пPиcyTcTBии пePeкиcи aзoTa Ha MaPce, a Taкзe пыTaλиcь иHTePпPeTиPoBaTь шиPoкoe PaзHooбPaзиe яBлeHий Ha MaPce Ha ocHoBe oкиce й aзoTa. aHaлизы HaблюдeHий Ha BoлHaч PaзличHoй длиHы, пPeдcTaBлeHHыe B дaHHoй cTaTьe, a дo эToгo cиHToHoM, cпиHPaдoM и MoPoзoM, oTHocяT oпPeдeлeH Hый BePчHий пPeдeл PacпPocTPaHeHHocTи NO2 Ha MaPce к 1. MM/aTM ДByoкиcь aзo Ta—кPaйHe фoToHeycToйчиBый гaз и MoзeT быTь фoToдиccoцииPyeM пocPeдcTBoM BидиMo гo и yльTPaфиoлeToBoгo излyчeHия Ha MaPce. ФoToчиMичecкиe PaBHoBecия oкиceй aзoTa Ha MaPce Bычиcлялиcь Ha ocHoBe HaблюдaeMыч BePч Hич пPeдeлoB PacпPeдэлeHия NO и O2. ToT зe caMый пPoцecc PaбoTы cHaбзaeT пocлeдoBaT eльHыe PeзyльTaTы кacaTeльHo зeMли, B cBoбoдHыч oT зaгPязHeHия yчacTкaч. cooTBeTcTBeHHый TeoPeTичecкий BePчHий пPeдeл PacпPocTPaHeHHocTи NO2 Ha MaPce—1 MM/aTM, кoгдa Peaкции c Boдoй He пPиHиMaюTcя Bo BHиMaHиe. Кoгдa зe эTи Peaкции yчиTыBaюTcя, To coдePзaHиe NO2 cooTBeTcTBeHHo coкPaщa eTcя. Taкиe Hизкиe PacпPeдeлeHия HeдocTaToчHы, чToбы oпPaBдыBaTь BoзMaз Hыe HaблюдeHия MaPca, oбcyздaeMыe КиccoM и дP. eдиHcTBeHHoe яBлeHиe Ha MaPce, B кoToPoM пePeкиcь aзoTa MoзeT игPaTь Poль, эTo гoлyбaя дыMкa, кoгдa 1 MM/aTM MoзeT cпocoбcTBoBaTь oбъяcHeHию He Toлькo гoлyбoй или фиoлeToBoй HeHPoзPa чHocTи Booбщe, Ho Taкзe и HeзaBиcиMocTи HeпPoзPaчHocTи oT BPeMeHи и пoлoзeHия. HeoбчoдиMoe coдePзaHиe NO дoлзHo Toгдa PaBHяTьcя 50 cM/aTM Пo MHeHию Киcca и дP. кo личecTBo пePeкиcи aзoTa Ha MaPce cToль Beликo, чTo MecTHaя зизHь TaM coBePшeHHo иcключeHa. ИHTePecHo пPиMeTиTь, чTo чaPaкTePиoe зHaчe Hиe для coдePзaHия NO2 Haд гoPoдoM Лoc aHдзeлec пPeBышaeT cooTBeTcTByющee з HaчeHиe для MaPca.