The photochemical evolution of polycyclic aromatic hydrocarbons and nontronite clay on early Earth and Mars

Kopacz, Nina; Corazzi, Maria Angela; Poggiali, Giovanni; Essen, Ayla von; Kofman, Vincent; Fornaro, Teresa; Ingen, Hugo van; Camprubí, Eloi; H, King; Brucato, J. R.; Kate, I. L. ten

doi:10.1016/j.icarus.2023.115437

“…Polycyclic aromatic hydrocarbons (PAHs) are recognized as a highly important class of organic compounds. They have long been, and still are, of interest in many research fields ranging from environmental science, where they are investigated for their role as pollutants [ 1 ], to Earth science and astronomy, in which they are of great interest to early Earth and Mars origin-of-life studies [ 2 ], and then to organic electronics, where they are used as semiconductors [ 3 , 4 , 5 , 6 , 7 , 8 , 9 ]. Among this wide family of chemical species, pyrene emerges as the preferred chromophore in both fundamental and applied photochemical research thanks to its properties, which have found application in many scientific areas [ 9 ].…”

Section: Introductionmentioning

confidence: 99%

Eclipsed and Twisted Excimers of Pyrene and 2-Azapyrene: How Nitrogen Substitution Impacts Excimer Emission

Dai,

Rambaldi,

Negri

2024

Molecules

0

View full text Add to dashboard Cite

Due to their unique photophysical and electronic properties, pyrene and its analogues have been the subject of extensive research in recent decades. The propensity of pyrene and its derivatives to form excimers has found wide application in various fields. Nitrogen-substituted pyrene derivatives display similar photophysical properties, but for them, excimer emission has not been reported to date. Here, we use time-dependent density functional theory (TD-DFT) calculations to investigate the low-lying exciton states of dimers of pyrene and 2-azapyrene. The excimer equilibrium structures are determined and the contribution of charge transfer (CT) excitations and intermolecular interactions to the exciton states is disclosed using a diabatization procedure. The study reveals that the dimers formed by the two molecules have quite similar exciton-state patterns, in which the relevant CT contributions govern the formation of excimer states, along with the La/Lb state inversion. In contrast with pyrene, the dipole–dipole interactions in 2-azapyrene stabilize the dark eclipsed excimer structure and increase the barrier for conversion into a bright twisted excimer. It is suggested that these differences in the nitrogen-substituted derivative might influence the excimer emission properties.

show abstract

“…However, the documentation of the collected samples is performed by characterizing abraded patches of the same rock, which are exposed to ambient Martian UV after the subsurface material is revealed by the Perseverance's abrasion tool. For rover operational reasons, abraded patches are exposed to ambient UV for at least 1 𝑠𝑜𝑙 before measuring with proximity science instruments, which can be enough to cause photochemical reactions of possible organics if embedded into photocatalytic mineral matrices 1,12,13 . A severe molecular photodegradation due to exposure to UV before measuring with the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) 14 Perseverance instrument might lead to a significant underestimation of the astrobiological relevance of the Jezero samples.…”

Section: Introductionmentioning

confidence: 99%

Investigating the stability of aromatic carboxylic acids in hydrated magnesium sulfate under UV irradiation to assist detection of organics on Mars

Alberini,

Fornaro,

Florentino

et al. 2024

Preprint

0

View full text Add to dashboard Cite

The Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument onboard the Mars 2020 Perseverance rover detected so far some of the most intense fluorescence signals in association with sulfates analyzing abraded patches of rocks at Jezero crater, Mars. To assess the plausibility of an organic origin of these signals, it is key to understand if organics can survive exposure to ambient Martian UV after exposure by the Perseverance abrasion tool and prior to analysis by SHERLOC. In this work, we investigated the stability of organo-sulfate assemblages under Martian-like UV irradiation and we observed that the spectroscopic features of phthalic and mellitic acid embedded into hydrated magnesium sulfate do not change for UV exposures corresponding to at least 48 Martian sols and, thus, should still be detectable in fluorescence when the SHERLOC analysis takes place, thanks to the photoprotective properties of magnesium sulfate. In addition, different photoproduct bands diagnostic of the parent carboxylic acid molecules could be observed. The photoprotective behavior of hydrated magnesium sulfate corroborates the hypothesis that sulfates might have played a key role in the preservation of organics on Mars, and that the fluorescence signals detected by SHERLOC in association with sulfates could potentially arise from organic compounds.

show abstract

“…However, the documentation of the collected samples is performed by characterizing abraded patches of the same rock, which are exposed to ambient Martian UV after the subsurface material is revealed by the Perseverance’s abrasion tool. For rover operational reasons, abraded patches are exposed to ambient UV for at least before measuring with proximity science instruments, which can be enough to cause photochemical reactions of possible organics if embedded into photocatalytic mineral matrices 1 , 15 , 16 . A severe molecular photodegradation due to exposure to UV before measuring with the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) 17 .…”

Section: Introductionmentioning

confidence: 99%

Investigating the stability of aromatic carboxylic acids in hydrated magnesium sulfate under UV irradiation to assist detection of organics on Mars

Alberini,

Fornaro,

García-Florentino

et al. 2024

Sci Rep

0

View full text Add to dashboard Cite

The Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument onboard the Mars 2020 Perseverance rover detected so far some of the most intense fluorescence signals in association with sulfates analyzing abraded patches of rocks at Jezero crater, Mars. To assess the plausibility of an organic origin of these signals, it is key to understand if organics can survive exposure to ambient Martian UV after exposure by the Perseverance abrasion tool and prior to analysis by SHERLOC. In this work, we investigated the stability of organo-sulfate assemblages under Martian-like UV irradiation and we observed that the spectroscopic features of phthalic and mellitic acid embedded into hydrated magnesium sulfate do not change for UV exposures corresponding to at least 48 Martian sols and, thus, should still be detectable in fluorescence when the SHERLOC analysis takes place, thanks to the photoprotective properties of magnesium sulfate. In addition, different photoproduct bands diagnostic of the parent carboxylic acid molecules could be observed. The photoprotective behavior of hydrated magnesium sulfate corroborates the hypothesis that sulfates might have played a key role in the preservation of organics on Mars, and that the fluorescence signals detected by SHERLOC in association with sulfates could potentially arise from organic compounds.

show abstract

The photochemical evolution of polycyclic aromatic hydrocarbons and nontronite clay on early Earth and Mars

Cited by 6 publications

References 92 publications

Eclipsed and Twisted Excimers of Pyrene and 2-Azapyrene: How Nitrogen Substitution Impacts Excimer Emission

Eclipsed and Twisted Excimers of Pyrene and 2-Azapyrene: How Nitrogen Substitution Impacts Excimer Emission

Investigating the stability of aromatic carboxylic acids in hydrated magnesium sulfate under UV irradiation to assist detection of organics on Mars

Investigating the stability of aromatic carboxylic acids in hydrated magnesium sulfate under UV irradiation to assist detection of organics on Mars

Contact Info

Product

Resources

About