In this review I summarize the current state of knowledge about the composition of Titan's atmosphere and our current understanding of the suggested chemistry that leads to that observed composition. I begin with our present knowledge of the atmospheric composition, garnered from a variety of measurements including -, the , and other ground- and space-based telescopes. This review focuses on the typical vertical profiles of gases at low latitudes rather than global and temporal variations. The main body of the review presents a chemical description of how complex molecules are believed to arise from simpler species, considering all known "stable" molecules-those that have been uniquely identified in the neutral atmosphere. The last section of the review is devoted to the gaps in our present knowledge of Titan's chemical composition and how further work may fill those gaps.
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http://dx.doi.org/10.1021/acsearthspacechem.2c00041 | DOI Listing |
Life (Basel)
January 2025
Department of Biology, University of Crete, Voutes University Campus, GR-70013 Heraklion, Crete, Greece.
This study investigates the resilience of the unicellular green microalga to extreme atmospheric conditions simulating those of Mars, Jupiter, and Titan. Using Earth as a control, experiments were conducted under autotrophic and mixotrophic conditions to evaluate the organism's photosynthetic efficiency, oxygen production, and biomass growth over 2, 5, and 12 days. Photosynthetic performance was analyzed through chlorophyll a fluorescence induction (JIP-test), metabolic activity via gas chromatography, and biomass accumulation measurements.
View Article and Find Full Text PDFNat Geosci
December 2024
Université Paris Cité, Institut de Physique du Globe de Paris, CNRS, Paris, France.
Saturn's rings have been estimated to be as young as about 100 to 400 million years old according to the hypothesis that non-icy micrometeoroid bombardment acts to darken the rings over time and the Cassini observation indicated that the ring particles appear to be relatively clean. These young age estimates assume that the rings formed out of pure water ice particles with a high accretion efficiency of impacting non-icy micrometeoroid material ( ≳ 10%). Here we show, using numerical simulations of hypervelocity micrometeoroid impacts on a ring particle, that non-icy material may not be as readily accreted as previously thought.
View Article and Find Full Text PDFJ Phys Chem A
January 2025
Department of Chemistry, Saitama University, Saitama City, Saitama 338-8570, Japan.
Rate coefficients for ion-polar-molecule reactions between acetonitrile molecules (CHCN) and nitrogen molecular ions (N), which are of importance to the upper atmospheric chemistry of Saturn's moon Titan, were measured for the first time at low translational temperatures. In the experiments, the reaction between sympathetically cooled N ions embedded in laser-cooled Ca Coulomb crystals and velocity-selected acetonitrile molecules generated using a wavy Stark velocity filter was studied to determine the reaction rate coefficients. Capture rate coefficients calculated by the Su-Chesnavich approach and by the perturbed rotational state theory considering the rotational state distribution of CHCN were compared to the experimental rate coefficients.
View Article and Find Full Text PDFSci Data
January 2025
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 91109, USA.
The Imaging Science Subsystem onboard the Cassini spacecraft recorded numerous high-quality images of Jupiter and Saturn at various wavelengths, from ultraviolet to near-infrared, during its 20-year mission from 1997 to 2017. Using these images, we have developed global maps of Jupiter and Saturn across multiple wavelengths. These maps reveal the global atmospheric structures of Jupiter and Saturn, offering a comprehensive tool to study the physical and dynamic processes of these atmospheric systems on a global scale.
View Article and Find Full Text PDFJ Phys Chem Lett
January 2025
Department of Chemistry, University of Hawai'i at Ma̅noa, Honolulu, Hawaii 96822, United States.
What if an experiment could combine the power of cycloaddition and cross-coupling with the formation of an aromatic molecule in a single collision? Crossed molecular beam experiments augmented with electronic structure and statistical calculations provided compelling evidence on a novel radical route involving 1,3-butadiynyl (HCCCC; X∑) radicals synthesizing (substituted) arylacetylenes in the gas phase upon reactions with 1,3-butadiene (CHCHCHCH; XA) and 2-methyl-1,3-butadiene (isoprene; CHC(CH)CHCH; XA'). This elegant mechanism merges two previously disconnected concepts of cross-coupling and cycloaddition-aromatization in a single collision event via the formation of two new C(sp)-C(sp) bonds and bending the 180° moiety of the linear 1,3-butadiynyl radical out of the ordinary by 60° to 120°. In addition to its importance to fundamental organic chemistry, this unconventional mechanism links two previously separated routes of gas-phase molecular mass growth processes of polyacetylenes and polycyclic aromatic hydrocarbons (PAHs), respectively, in low-temperature environments such as in cold molecular clouds like the Taurus Molecular Cloud (TMC-1) and in hydrocarbon-rich atmospheres of planets and their moons such as Titan, which revises the established understanding of low-temperature molecular mass growth processes in the Universe.
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