Negative ion chemistry in Titan's upper atmosphere

Vuitton, V.; Lavvas, P.; Yelle, R. V.; Galand, M.; Wellbrock, A.; Lewis, G. R.; Coates, A. J.; Wahlund, J. E.

doi:10.1016/j.pss.2009.04.004

Cited by 257 publications

(265 citation statements)

References 105 publications

(115 reference statements)

Supporting

Mentioning

258

Contrasting

Unclassified

Order By: Relevance

“…Previous studies show that the ion-neutral chemistry is responsible for the molecular growth of the N 2 and CH 4 photolysis products to larger-mass gas species reaching to masses up to a few hundred daltons (13,25,34,39). Here we provide a selfconsistent picture for the growth of aerosol particles from 100 Da to tens of thousands of daltons.…”

Section: Discussionmentioning

confidence: 84%

“…The overall density and shape of the simulated spectrum are in good agreement with the CAPS/ELS observations for masses larger than 100 Da, indicating that the observed heavy negative ions are charged particles. The small masses (below 100 Da) identified in the CAPS/ELS spectrum correspond to gas-phase negative ions, which we have characterized in the past (34). Thus, the ELS spectrum shows a smooth transition from the gas-phase chemistry to the aerosol growth in Titan's ionosphere.…”

Section: Lessons From Titanmentioning

confidence: 78%

“…For the processes considered here, the small mass negative ions are lost mainly by recombination with positive ions. Here we do not include neutral chemistry processes, which are important for the loss of the small mass negative ions (34), but this assumption does not affect our conclusions because the small mass negative ions have a minimal contribution to the overall charge balance and the mass growth of the aerosols. Hence, the increase of the positive ions due to the presence of charged particles causes an increased loss of negative ions (Fig.…”

Section: Lessons From Titanmentioning

confidence: 99%

See 2 more Smart Citations

Aerosol growth in Titan’s ionosphere

Lavvas

Yelle

Koskinen

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

140

134

View full text Add to dashboard Cite

Photochemically produced aerosols are common among the atmospheres of our solar system and beyond. Observations and models have shown that photochemical aerosols have direct consequences on atmospheric properties as well as important astrobiological ramifications, but the mechanisms involved in their formation remain unclear. Here we show that the formation of aerosols in Titan's upper atmosphere is directly related to ion processes, and we provide a complete interpretation of observed mass spectra by the Cassini instruments from small to large masses. Because all planetary atmospheres possess ionospheres, we anticipate that the mechanisms identified here will be efficient in other environments as well, modulated by the chemical complexity of each atmosphere.planetary sciences | heterogeneous chemistry | particles charging | plasma P hotochemical aerosols are observed in many atmospheres of our solar system (1-3), and their presence is also detected in exoplanet atmospheres (4). Apart from their direct influence on the atmospheric properties through their interaction with the radiation field, aerosols have further astrobiological implications; their presence in the early Earth's atmosphere could have protected the surface and any life evolving there from UV radiation (5), and laboratory studies of Titan aerosol analogs have identified an in vitro formation of amino acids during aerosol production (6). However, the general mechanisms involved in the production and growth of photochemical aerosols from atmospheric gases have remained elusive. Titan, as the most extreme example of an aerosol-dominated atmosphere, provides a unique opportunity to investigate these mechanisms.Cassini observations revealed the presence of aerosols in multiple regions of the atmosphere, from the troposphere (7), stratosphere (8), and mesosphere (9, 10) up to the thermosphere where the detection of large mass positive and particularly negative ions has been suggested to be the signature of aerosol formation (11)(12)(13)(14). During a recent flyby (T70), the Cassini spacecraft penetrated to deeper regions of Titan's thermosphere than usual, reaching altitudes close to 880 km that had not previously been sampled with in situ measurements. Measurements from the Langmuir probe (LP) during this unique flyby reveal a high abundance of negative ions at closest approach, comparable to the positive ion density, and a corresponding decrease in the electron density (15). This conclusion is supported by the analysis of multiple Cassini observations, which reveals that the observed electron density is smaller than the density anticipated from photochemical equilibrium, implying that the photochemical models are missing a significant electron loss mechanism (16, 17). Thus, current observations demonstrate a significant decrease of the electron density relative to the positive ion density in the lower ionosphere with a concurrent increase in the density of the negative ions.Aerosols, or dust particles in general, are known to interact with free electr...

show abstract

Section: Discussionmentioning

confidence: 84%

Section: Lessons From Titanmentioning

confidence: 78%

Section: Lessons From Titanmentioning

confidence: 99%

See 1 more Smart Citation

Aerosol growth in Titan’s ionosphere

Lavvas

Yelle

Koskinen

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

140

134

View full text Add to dashboard Cite

show abstract

“…In the stratosphere, it amounts to as much as 100 K, due to the absorption of the solar infrared flux by haze. Haze results from polymerization and condensation of the photochemical products of methane, particularly, polyynes, polycyclic aromatic hydrocarbons and nitriles in the neutral upper atmosphere (Wilson & Atreya 2004) and heavy organics in the ionosphere (Vuitton et al 2009). In the troposphere, opacity induced by collisions of methane-nitrogen, nitrogen-hydrogen (from methane) and nitrogen-nitrogen molecules results in a net temperature increase of 12 K. Without above heating effects initiated by methane, Titan's atmosphere would shrink substantially due to the condensation of nitrogen.…”

Section: S K Atreyamentioning

confidence: 99%

Atmospheric moons Galileo would have loved

Atreya

2010

Proc. IAU

View full text Add to dashboard Cite

Abstract. In the spirit of the symposium and the theme of the session of this presentation, "Our solar system after Galileo, the grand vision," I review briefly a relatively recently discovered phenomenon in the solar system − existence of atmospheres on certain moons, including Io, one of the four moons Galileo discovered four centuries ago. The origin of such atmospheres is discussed, and comparisons are made between various gassy moons.

show abstract

“…This CR-induced ionization of the Titan atmosphere has been modeled by several authors (Capone et al, 1980;Borucki et al, 1987Borucki et al, , 2006Molina-Cuberos et al, 1999a, 1999b, but of greatest significance in the interests of the astrobiology of Titan is the role this ionization-driven atmospheric chemistry plays in creating organic molecules. The upper, solar UV-generated ionosphere has been observed (by instruments aboard Cassini) to contain both positively charged organic molecules (Cravens et al, 2006) and heavy negative ions (Coates et al, 2007;Vuitton et al, 2009), which are believed to be important in the atmospheric hydrocarbon chemistry and transformation of simple gaseous species into organic-rich aerosol compounds-the socalled tholins. These long-chain hydrocarbons form the atmospheric haze layers and fall to deliver organics to the surface of Titan .…”

Section: Titan Atmosphere Ionizationmentioning

confidence: 99%

Ionizing Radiation and Life

2011

View full text Add to dashboard Cite

Ionizing radiation is a ubiquitous feature of the Cosmos, from exogenous cosmic rays (CR) to the intrinsic mineral radioactivity of a habitable world, and its influences on the emergence and persistence of life are wideranging and profound. Much attention has already been focused on the deleterious effects of ionizing radiation on organisms and the complex molecules of life, but ionizing radiation also performs many crucial functions in the generation of habitable planetary environments and the origins of life. This review surveys the role of CR and mineral radioactivity in star formation, generation of biogenic elements, and the synthesis of organic molecules and driving of prebiotic chemistry. Another major theme is the multiple layers of shielding of planetary surfaces from the flux of cosmic radiation and the various effects on a biosphere of violent but rare astrophysical events such as supernovae and gamma-ray bursts. The influences of CR can also be duplicitous, such as limiting the survival of surface life on Mars while potentially supporting a subsurface biosphere in the ocean of Europa. This review highlights the common thread that ionizing radiation forms between the disparate component disciplines of astrobiology.

show abstract

Negative ion chemistry in Titan's upper atmosphere

Cited by 257 publications

References 105 publications

Aerosol growth in Titan’s ionosphere

Aerosol growth in Titan’s ionosphere

Atmospheric moons Galileo would have loved

Ionizing Radiation and Life

Contact Info

Product

Resources

About