Icarus最新文献

{"title":"Delivery of carbonaceous materials to the Moon","authors":"Linxi Li ,&nbsp;Mengfan Qiu ,&nbsp;Sen Hu ,&nbsp;Hejiu Hui ,&nbsp;Yi Chen ,&nbsp;Qiu-Li Li ,&nbsp;Wei Yang ,&nbsp;Yuyang He ,&nbsp;Shitou Wu ,&nbsp;Hao Wang ,&nbsp;Guoqiang Tang ,&nbsp;Di Zhang ,&nbsp;Lihui Jia ,&nbsp;Lixin Gu ,&nbsp;Huicun He ,&nbsp;Yubing Gao ,&nbsp;Liang Gao ,&nbsp;Zhan Zhou ,&nbsp;Yangting Lin ,&nbsp;Xian-Hua Li ,&nbsp;Fu-Yuan Wu","doi":"10.1016/j.icarus.2025.116802","DOIUrl":"10.1016/j.icarus.2025.116802","url":null,"abstract":"<div><div>Asteroidal impacts play an important role in creating new lithology, shaping the morphology, and transporting water to the inner Solar System planets. Massive impact records have been preserved on the Moon; however, exogenous impactors have not been adequately identified in lunar samples. Here we carried out petrological and geochemical investigations on the newly lunar samples returned by Chang'e-6 (CE6) to estimate the source of impactors to the Moon. One spinel-bearing troctolite-like clast was identified in the CE6 soils. This clast displays porphyritic texture and is mainly composed of olivine (32 %), plagioclase (31 %), and mesostasis (34 %) with minor troilite (2 %) and spinel (1 %), and rare Fe-Ni metal, in area%. The sample olivines have a forsterite variation range of 75–85 and a Fe/Mn atomic ratio of 55–80. The trace element concentrations of Co (113–223 μg.g⁻¹), Ni (121–938 μg.g⁻¹), Cr (1191–4832 μg.g⁻¹), and P (827–1645 μg.g⁻¹) in olivines are notable higher than the typical lunar samples. Furthermore, these olivines exhibit notable ¹⁶O depletion features (δ¹⁸O: +10.7 ‰ to +16.7 ‰ and δ¹⁷O: +5.9 ‰ to +9.5 ‰). The investigated clast has a bulk Ir content of 51 ng.g⁻¹, significantly higher than local lunar materials. The unusual texture, mineral chemistry, trace element concentrations, and oxygen isotopic compositions suggest this clast was likely derived from an impact event created by a CI- or CY-like carbonaceous chondrite. Such chemical and isotopic features are correlated with textures, indicating that some olivine have relict cores originated from the impactor. Such an impact event could have produced a new lithology of spinel-bearing troctolite on the Moon. Meanwhile, the carbonaceous chondritic impactor would have delivered a great amount of water and volatiles to the Moon.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"444 ","pages":"Article 116802"},"PeriodicalIF":3.0,"publicationDate":"2025-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145048225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A comprehensive study of comet 67P/Churyumov-Gerasimenko in the 2021/2022 apparition. I. Photometry, spectroscopy, morphology","authors":"Vira Rosenbush ,&nbsp;Valerii Kleshchonok ,&nbsp;Oleksandra Ivanova ,&nbsp;Igor Luk'yanyk ,&nbsp;Colin Snodgrass ,&nbsp;Daniel Gardener ,&nbsp;Ludmilla Kolokolova ,&nbsp;Johannes Markkanen ,&nbsp;Elena Shablovinskaya","doi":"10.1016/j.icarus.2025.116799","DOIUrl":"10.1016/j.icarus.2025.116799","url":null,"abstract":"<div><div>We present observations of comet 67P/Churyumov–Gerasimenko during its 2021/22 apparition, aiming to investigate its dust and gas environment and compare the results with those obtained in 2015/16 using the same telescope. Quasi-simultaneous photometric, spectroscopic, and polarimetric observations were carried out at the 6-m BTA SAO telescope. The comet was observed on 6 October 2021, 31 days before perihelion, with <em>g-</em>sdss and <em>r-</em>sdss filters, and on 6 February 2022, 96 days after perihelion, using narrowband cometary filters: <em>BC</em> (λ4450/62 Å), <em>RC</em> (λ6839/96 Å), and <em>CN</em> (λ3870/58 Å). These were complemented by images from the 2-m Liverpool Telescope (La Palma). On 6 October 2021, a sunward jet and long dust tail were detected. By 6 February 2022, the dust coma morphology had changed noticeably, revealing a bright sunward neckline structure superimposed on the projected dust tail, along with two jets at position angles of 133° and 193°. Spectra showed strong CN emission, with relatively weak C₂, C₃, and NH₂ emissions. The dust production rate <em>Afρ</em> did not exceed 200 cm (uncorrected for phase angle) in both epochs. An unusual CN coma morphology was observed, with evidence of an additional CN source associated with dust jets. Geometric modeling of the jets' dynamics indicated an active area at latitude −70° ± 4° with a jet opening angle of 20° ± 6° on 6 October 2021, and two active areas at latitudes −58° ± 5° and − 53° ± 10°, separated by longitude 150° ± 20°, producing the observed jets on 6 February 2022. The average particle velocity in the jets was about 0.32 ± 0.04 km s⁻¹.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"444 ","pages":"Article 116799"},"PeriodicalIF":3.0,"publicationDate":"2025-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145048119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Wavelet analysis of concentric crater fill surface ridges","authors":"Claire W. Cook,&nbsp;Shane Byrne","doi":"10.1016/j.icarus.2025.116797","DOIUrl":"10.1016/j.icarus.2025.116797","url":null,"abstract":"<div><div>Concentric crater fill (CCF) are debris-covered ice deposits widespread in the mid-latitudes of Mars, which often exhibit ridges parallel to the crater walls. Surface ridges on debris-covered glaciers, which may be due to englacial or supraglacial debris transport, can provide insight into past climate variations. Alternatively, ridges may be related to non-climatic processes such as viscous buckle folding due to compression. We test the hypothesis that surface ridges on CCF are related to climate variations, driven by variations in orbital parameters, by identifying periodicities in CCF ridges and, where possible, comparing ratios of pairs of wavelengths to ratios of orbital periodicities. We identified wavelengths in surface ridges on concentric crater fill using wavelet analysis of profiles across HiRISE images and DTMs. For 68 % of CCF sites, we identified at least one significant wavelength, and identified a median wavelength of ∼33 m from brightness profiles. For elevation profiles, we found a median wavelength of ∼32 m. We identified only five cases with two wavelengths overlapping over a significant distance along profile that appeared to correspond to distinct periodicities. These rare cases did not have ratios clearly related to ratios of two orbital periodicities. Based on this, our results do not support the idea that CCF ridge spacing is related to orbital periodicities. We favor the possibility that CCF ridge spacing is instead due to buckle folding. The median wavelength of CCF ridges is consistent with buckle folding for a debris/ice viscosity ratio of 1–2 and a debris layer thickness of 6–8 m.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"444 ","pages":"Article 116797"},"PeriodicalIF":3.0,"publicationDate":"2025-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145048156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The YORP effect for meter-sized asteroids","authors":"Conor J. Benson,&nbsp;Daniel J. Scheeres","doi":"10.1016/j.icarus.2025.116794","DOIUrl":"10.1016/j.icarus.2025.116794","url":null,"abstract":"<div><div>The spin states of meter-sized asteroids should evolve rapidly due to the Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) effect. While these asteroids are very challenging to observe, artificial geosynchronous (GEO) satellites are convenient analogues given that they are driven primarily by solar torques, evolve rapidly, and are easy to observe. These artificial objects could provide insight about the evolution of their natural counterparts. Recent studies of YORP for defunct GEO satellites with full and tumbling-averaged models have uncovered rich dynamical structure with tumbling cycles, angular momentum sun-tracking, and tumbling resonances. Applying the tumbling-averaged YORP models to meter-sized pseudo asteroids, we find that the solar torque structure yields sun-tracking precession in many cases, particularly for asteroids with at least some elongation. Precession about the sun line results in the long-term obliquity averaging to roughly 90°. As a result, the sun-tracking behavior could potentially shut off Yarkovsky drift for these asteroids and thereby limit their mobility out of the main asteroid belt. For some asteroid shapes, tumbling cycles with alternating spin up and spin down are also observed. These tumbling cycles offer a possible avenue to prevent spin-driven disruption of meteoroids.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"444 ","pages":"Article 116794"},"PeriodicalIF":3.0,"publicationDate":"2025-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145048227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Behaviors of Martian CO2-driven dry climate system and conditions for atmospheric collapses","authors":"Yasuto Watanabe ,&nbsp;Eiichi Tajika ,&nbsp;Arihiro Kamada","doi":"10.1016/j.icarus.2025.116795","DOIUrl":"10.1016/j.icarus.2025.116795","url":null,"abstract":"<div><div>The present Martian climate is characterized by a cold and dry environment with a thin atmosphere of carbon dioxide (CO₂). In such conditions, the planetary climate is determined by the distribution of CO₂ between exchangeable reservoirs, that is, the atmosphere, ice caps, and regolith. This produces unique responses of the Martian CO₂-driven climate system to variations of astronomical forcings. Specifically, it has been shown that the phenomenon called an atmospheric collapse occurs when the axial obliquity is low, affecting the Martian climatic evolution. However, the long-term evolution of the behavior of the Martian climate system and the accompanying changes in climate and habitability remain ambiguous. Here we employed a latitudinally-resolved Martian energy balance model and assessed the possible climate on Mars for wider ranges of orbital parameters, solar irradiance, and total exchangeable CO₂ mass. We show that, among the orbital parameters, variations of axial obliquity have a strong impact on the carbon distribution on Mars, while variations of eccentricity and longitude of perihelion have a minor impact. We show that the threshold obliquity for atmospheric collapse under cold and dry conditions decreases from ∼20° at the end of Noachian to ∼14° at the present condition, indicating that the atmospheric collapse would have occurred repeatedly in the history of Mars. When the obliquity is over ∼20°, the atmospheric <em>p</em>CO₂ on Mars would be affected primarily by the changes in the total exchangeable CO₂ mass. We also show that the magnitude of the variation of atmospheric <em>p</em>CO₂ when atmospheric collapse occurs decreases during the Hesperian. Even considering the broad ranges of these parameters, the habitable conditions in the Martian CO₂-driven dry climate system would be limited to high-latitude summers if there are no warming mechanisms other than the greenhouse effect of CO₂ and H₂O.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"444 ","pages":"Article 116795"},"PeriodicalIF":3.0,"publicationDate":"2025-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145061631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geological mapping and chronology of lunar landing sites: Apollo 15","authors":"W. Iqbal ,&nbsp;J.W. Head III ,&nbsp;L. Wueller ,&nbsp;H. Hiesinger ,&nbsp;C.H. van der Bogert ,&nbsp;D.R. Scott","doi":"10.1016/j.icarus.2025.116791","DOIUrl":"10.1016/j.icarus.2025.116791","url":null,"abstract":"<div><div>Apollo 15 was the first extended exploration mission to the Moon. The data acquired from the Apollo 15 mission constitutes a comprehensive geological dataset, significantly enhancing our understanding of volcanic, impact and other geological processes, and the chronological and thermal evolution of the Moon. Moreover, the Apollo 15 data provide a critical calibration point for the lunar cratering chronology function. This chronology is established through the systematic correlation of crater size-frequency distributions (CSFDs) with radioisotopic ages of samples from the Apollo, Luna, and Chang'e landing sites. Establishing this link between samples and CSFDs necessitates a thorough understanding of the geology of the landing sites. In this study, we present a newly developed, detailed regional geological map of the Apollo 15 landing site, utilizing modern data. Our new geological map enables the identification of homogeneous regions suitable for new CSFD measurements, from which updated <em>N</em>(1) values (i.e., the cumulative number of craters with diameters ≥1 km) can be derived for the corresponding geological units. Furthermore, this geological map addresses outstanding scientific questions, which have been outlined as objectives for the 500-day Hadley Max design reference mission (DRM) (<span><span>Daniti et al., 2024</span></span>). The new calibration point obtained from comparing these updated <em>N</em>(1) values with sample ages was found to be consistent with the lunar chronology proposed by <span><span>Neukum (1983)</span></span>. This consistency, in conjunction with our previous research, reinforces the validity of Neukum's lunar cratering chronology. We summarize the key outstanding scientific questions identified by the new geologic map as a basis for future human and robotic lunar exploration of the Moon.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"444 ","pages":"Article 116791"},"PeriodicalIF":3.0,"publicationDate":"2025-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145097718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Temperature dependence of CH3CNN2 line broadening predicted from extended rotational-band measurements","authors":"J. Buldyreva ,&nbsp;A.S. Dudaryonok ,&nbsp;N.N. Lavrentieva","doi":"10.1016/j.icarus.2025.116793","DOIUrl":"10.1016/j.icarus.2025.116793","url":null,"abstract":"<div><div>As methyl cyanide is one of the complex organic molecules present in planetary atmospheres, comets and interstellar medium but extremely scarce data are available for its radiative transfer modeling, we focus on providing exhaustive sets of theoretical nitrogen-broadening coefficients of CH<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span>CN lines for a large set of quantum numbers and a wide temperature range of astrophysical interest. Taking advantage of recent extensive measurements of rotational transitions with Voigt- and Speed-Dependent-Voigt profiles at room temperature and the corresponding update of the temperature-independent parameters of the semi-empirical approach suitable for CH<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span>X-type molecules with large dipole moments, we employ these parameters in calculations for lower and higher temperatures with a further determination of temperature-dependence exponents. CH<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span>CN<img>N<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> line-broadening parameters are calculated for both line-profile models in the temperature range 100–2000 K for the rotational numbers <span><math><mrow><mi>J</mi><mo>=</mo><mn>0</mn></mrow></math></span>–80, <span><math><mrow><mi>K</mi><mo>=</mo><mn>0</mn></mrow></math></span>–20 typically requested by spectroscopic databases. The temperature-dependence exponents for the reference temperature <span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>ref</mi></mrow></msub></math></span> = 296 K are extracted for the Earth’s-atmosphere related interval 200–400 K, the interval of theoretical validity 300–2000 K, and the full interval of interest 100–2000 K, showing an excellent applicability of the traditional one-power temperature law. Although the semi-classical treatment is not rigorously justified at low temperatures 100–300 K but seems to be the only feasible one, separate datasets are provided for this interval as well. As no clear experimental evidence exists neither for branch- nor for vibrational dependency of N<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>-broadening of CH<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span>CN lines, the data computed for the rotational band can be used for other branches in other bands of vibrotational transitions.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"443 ","pages":"Article 116793"},"PeriodicalIF":3.0,"publicationDate":"2025-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145003909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A new method for density and temperature retrieval from Cassini/UVIS solar occultations at Saturn","authors":"P. Stephenson ,&nbsp;T.T. Koskinen ,&nbsp;J.I. Moses ,&nbsp;Z.L. Brown","doi":"10.1016/j.icarus.2025.116787","DOIUrl":"10.1016/j.icarus.2025.116787","url":null,"abstract":"<div><div>Ultraviolet solar occultations by Saturn probe the extent, temperature and density of the thermosphere. The Cassini Ultraviolet Imaging Spectrograph (UVIS) observed 24 solar occultations by Saturn between 2007 and 2013 in the extreme ultraviolet (EUV). We have developed a new methodology to retrieve temperature and density profiles from the solar occultations, providing calibration-independent <figure><img></figure> profiles. To demonstrate this methodology here, we present a case study on 17 Nov 2007 at a latitude of -47.5 °.Our motivation was to retrieve a robust H profile for comparison with Lyman <span><math><mi>α</mi></math></span> dayglow observations of this location and time, given the uncertainty in absolute brightness calibration at Lyman <span><math><mi>α</mi></math></span> wavelengths. We will apply this method to the remaining solar occultations in future work. With improved removal of background contamination compared to previous analyses, we retrieve H and H₂ densities as deep as the methane homopause level, simultaneously fitting the full available altitude and wavelength range in the EUV. This demonstrates the potential of solar occultations to constrain the density and temperature profiles in Saturn’s upper atmosphere and extend the coverage of other observations. We closely reproduce the observed transmission from 560<!--> <!-->Å to 1150<!--> <!-->Å, with substantial absorption by <figure><img></figure> including the fine structure of the H₂ band absorption cross sections above 804<!--> <!-->Å. We find a revised exospheric temperature of <span><math><mrow><mn>487</mn><mo>±</mo><mn>22</mn></mrow></math></span> <!--> <!-->K, a reduction from the <span><math><mrow><mn>526</mn><mo>±</mo><mn>11</mn></mrow></math></span> <!--> <!-->K previously retrieved, due to wider spectral coverage. The atomic H column density of <span><math><mrow><mn>2</mn><mo>.</mo><mn>82</mn><mo>±</mo><mn>0</mn><mo>.</mo><mn>2</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>16</mn></mrow></msup></mrow></math></span> <!--> <!-->cm⁻² above the methane homopause is consistent with column densities required to generate the Lyman-<span><math><mi>α</mi></math></span> emissions from Saturn’s disk, also observed with Cassini/UVIS. The atomic H column density and temperatures are also consistent with the Voyager Ultraviolet Spectrometer (UVS) solar occultations, but the column density exceeds photochemical model predictions by a factor of two. This may be driven by circulation or otherwise enhanced mixing near the homopause level.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"444 ","pages":"Article 116787"},"PeriodicalIF":3.0,"publicationDate":"2025-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145048155","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The history of Martian water during the Hesperian and Amazonian epochs","authors":"Bruce M. Jakosky ,&nbsp;Noora R. Alsaeed ,&nbsp;Eryn M. Cangi ,&nbsp;Michael S. Chaffin ,&nbsp;Justin Deighan ,&nbsp;Margaret E. Landis ,&nbsp;Michael T. Mellon ,&nbsp;Edward M.B. Thiemann","doi":"10.1016/j.icarus.2025.116782","DOIUrl":"10.1016/j.icarus.2025.116782","url":null,"abstract":"<div><div>Evidence points to there having been more surface and near-surface Martian water in the late Hesperian and early Amazonian than there is at present: (i) The measured enrichment in the D/H isotopic ratio suggests that the total amount of H₂O lost to space during the Amazonian was significant relative to the amount currently locked up in the polar and non-polar ice deposits, and that it was more than expected based on the current rate of loss to space. (ii) The Dorsa Argentea Formation (DAF), surrounding the South Polar Layered Deposits (SPLD) and having an area larger than the SPLD, is thought to be the remnant of a Hesperian-era polar cap that may have contained ∼20 m Global Equivalent Layer (GEL) or more of water that is not thought to be present in the DAF today. We explore the consequences of this greater surface water inventory, how it ties in with the exchange of water between the different non-atmospheric reservoirs and the loss of water to space from the Hesperian epoch up to the present. The combination of polar and atmospheric processes and the likelihood of the axial obliquity typically having been greater than today's 25.2° earlier in history would have resulted in more surface and near-surface water and therefore larger H₂O polar caps in the late Hesperian, enhanced atmospheric water content, and an enlargement of regions having stable ground ice so that global near-surface ice may have been the norm. In addition, the increased solar extreme ultraviolet (EUV) flux, solar flares, and coronal mass ejections (CMEs) during the earlier epochs would have enhanced loss of H and O to space above the current loss rate, so that much or all of the water from the DAF may have been lost to space. Coupling between solar processes, atmospheric and upper-atmospheric processes, and geological processes produces a self-consistent scenario for the evolution of water.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"443 ","pages":"Article 116782"},"PeriodicalIF":3.0,"publicationDate":"2025-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144996725","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The photochemistry of irradiated Enceladus ice analogues: Implications for the formation of ozone and carbon trioxide","authors":"T.-M. Bründl ,&nbsp;J. Terwisscha van Scheltinga ,&nbsp;S. Cazaux ,&nbsp;K.-J. Chuang ,&nbsp;H. Linnartz","doi":"10.1016/j.icarus.2025.116751","DOIUrl":"10.1016/j.icarus.2025.116751","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Detailed observations of Enceladus by the Cassini spacecraft revealed its astrobiological potential and transformed our perception of ocean worlds in the Solar System. Beneath Enceladus’ icy crust lies a warm ocean sustained by tidal heating. This ocean expels subsurface material through fissures at the south pole region into space as plumes. The particles in these plumes reaccrete on Enceladus’ surface, while some of the volatiles present in the sub-surface ocean diffuse through the ice shell to reach the surface. In this study, we irradiated thin Enceladus ice analogues in an ultra-high vacuum chamber optimised for ice chemistry at a surface temperature of 70 &lt;span&gt;&lt;math&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt; 2 K and compared the resulting composition with ices typical to the ISM (15 K). We studied the irradiation of ices composed of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;CO&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;NH&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; mixtures as a function of wavelength by using two different radiation sources that cover high and low photon energy ranges: The microwave-discharge hydrogen-flow lamp (MDHL) generating vacuum-ultraviolet (VUV) light, that is, between 115 - 180 nm, and the solar radiation Xe-arc lamp (SRL), simulating the solar broadband radiation from 200 nm - 1800 nm. Upon irradiation, solid-state photoproducts were identified using a Fourier-transform infrared (FTIR) spectrometer in the mid-infrared range (4000 - 700 &lt;span&gt;&lt;math&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;cm&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/math&gt;&lt;/span&gt; or 2.5 - 14.3 &lt;span&gt;&lt;math&gt;&lt;mi&gt;μ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;m). Sublimating gas-phase species were tracked using a quadrupole mass spectrometer (QMS). At 70 K, energetic photons from the MDHL formed new species such as &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;CO&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; in an &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;O:CO&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;:&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;NH&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; ice matrix due to the clustering of &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;CO&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; at elevated temperatures. Hereby, dissociation of segregated &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;CO&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; provides the necessary oxygen atoms to form &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; via the enhanced mobility and addition reaction of O-atoms. At 15 K, &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;CO&lt;/mi&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;OCN&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"444 ","pages":"Article 116751"},"PeriodicalIF":3.0,"publicationDate":"2025-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217769","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}