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. 2006 Nov 28;103(48):18035-42.
doi: 10.1073/pnas.0608561103. Epub 2006 Nov 13.

Organic haze on Titan and the early Earth

Melissa G Trainer  1 , Alexander A Pavlov, H Langley DeWitt, Jose L Jimenez, Christopher P McKay, Owen B Toon, Margaret A Tolbert
Affiliations

Organic haze on Titan and the early Earth

Melissa G Trainer et al. Proc Natl Acad Sci U S A. .

Abstract

Recent exploration by the Cassini/Huygens mission has stimulated a great deal of interest in Saturn's moon, Titan. One of Titan's most captivating features is the thick organic haze layer surrounding the moon, believed to be formed from photochemistry high in the CH(4)/N(2) atmosphere. It has been suggested that a similar haze layer may have formed on the early Earth. Here we report laboratory experiments that demonstrate the properties of haze likely to form through photochemistry on Titan and early Earth. We have used a deuterium lamp to initiate particle production in these simulated atmospheres from UV photolysis. Using a unique analysis technique, the aerosol mass spectrometer, we have studied the chemical composition, size, and shape of the particles produced as a function of initial trace gas composition. Our results show that the aerosols produced in the laboratory can serve as analogs for the observed haze in Titan's atmosphere. Experiments performed under possible conditions for early Earth suggest a significant optical depth of haze may have dominated the early Earth's atmosphere. Aerosol size measurements are presented, and implications for the haze layer properties are discussed. We estimate that aerosol production on the early Earth may have been on the order of 10(14) g.year(-1) and thus could have served as a primary source of organic material to the surface.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
A hazy early Earth? It has been proposed that if the early Earth's atmosphere contained CH4, photochemical formation of an organic haze layer may have made the Earth's appearance very similar to that of Saturn's moon Titan (44). The role of CO2 in the haze formation process complicates understanding the atmospheric chemistry on the early Earth. Image of Earth appears courtesy of NASA/JPL/Space Science Institute.
Fig. 2.
Fig. 2.
Averaged mass spectrum for aerosols formed in 0.1% CH4 in N2. This spectrum is a representative spectrum for all aerosols produced in a range of mixtures of CH4 in N2. Data to the right of the dashed line at 50 amu are multiplied by 5 for ease of viewing. Prominent peaks are discussed in the text.
Fig. 3.
Fig. 3.
Aerosol mass production trends for CH4/N2 experiments as a function of CH4 concentration and mixing ratio. The data presented with black circles are derived from integrating the mass spectrum at each CH4 concentration. The red solid line shows the amount of particle mass calculated from the photochemistry model developed from mechanism A. The black dashed line shows the amount of particle mass calculated from the model developed from mechanism B.
Fig. 4.
Fig. 4.
Physical dimensions for aerosol analogs for Titan and early Earth. The black lines represent the particle traces from the AMS, measured for the m/z 41 fragment, as a function of Dva. The red lines represent the volume distribution measured by the SMPS, as a function of Dm. (a) Size distributions for aerosols produced in 0.1% CH4 in N2. The average Dva is 36.5 ± 3.4 nm, and the average Dm is 46.3 ± 3.5 nm. (b) TEM image of particles collected from the 0.1% CH4 mixture described in a. Magnification was set at ×92,000, and particle sizes are indicated. The average particle diameter observed with the TEM was ≈50 nm. (c) Size distributions for aerosols produced in 0.1% CH4/0.1% CO2 in N2 (C/O = 1). The average Dva is 34.4 ± 5.5 nm, and the average Dm is 54.5 ± 7.2 nm. (d) TEM image of particles collected from the C/O = 1 mixture described in c. Magnification was set at ×64,000, and particle sizes are indicated. The average particle diameter observed with the TEM was ≈50 nm.
Fig. 5.
Fig. 5.
Averaged mass spectra for standard early Earth simulations. Gas mixtures are composed of 0.1% CH4 and 0.02% CO2, C/O = 3 (a), 0.05% CO2, C/O = 1.5 (b), 0.1% CO2, C/O = 1 (c), 0.11% CO2, C/O = 0.95 (d), and 0.5% CO2, C/O = 0.6 (e). Data to the right of the dashed line at 50 amu are multiplied by 10 for ease of viewing. The spectrum for 0.1% CH4 with no CO2 added was shown in Fig. 2.
Fig. 6.
Fig. 6.
Total aerosol mass produced as a function of the C/O ratio of the starting gas mixture. For all points CH4 is at 0.1%. The filled circles are data derived from integrating the AMS mass spectra. The horizontal line shows the mass production from the CH4-only experiments. Error bars are represented by the standard deviation of all experiments performed. The data at a C/O ratio of 1 show an average enhancement factor of β = 1.5 for aerosol production in the experiments with C/O = 1 as compared with the CH4-only experiments.
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References

    1. Porco CC, Baker E, Barbara J, Beurle K, Brahic A, Burns JA, Charnoz S, Cooper N, Dawson DD, Del Genio AD, et al. Nature. 2005;434:159–168. - PubMed
    1. Waite JH, Niemann H, Yelle RV, Kasprzak WT, Cravens TE, Luhmann JG, McNutt RL, Ip WH, Gell D, De La Haye V, et al. Science. 2005;308:982–986. - PubMed
    1. Flasar FM, Achterberg RK, Conrath BJ, Gierasch PJ, Kunde VG, Nixon CA, Bjoraker GL, Jennings DE, Romani PN, Simon-Miller AA, et al. Science. 2005;308:975–978. - PubMed
    1. Shemansky DE, Stewart AIF, West RA, Esposito LW, Hallett JT, Liu XM. Science. 2005;308:978–982. - PubMed
    1. Israel G, Szopa C, Raulin F, Cabane M, Niemann HB, Atreya SK, Bauer SJ, Brun J-F, Chassefiere E, Coll P, et al. Nature. 2005;438:796–799. - PubMed

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