Icarus最新文献

{"title":"Magnetically controlled ionosphere of Mars: A model analysis with the vertical plasma drift effects","authors":"T. Majeed ,&nbsp;S.W. Bougher ,&nbsp;P. Withers ,&nbsp;S.A. Haider ,&nbsp;A. Morschhauser","doi":"10.1016/j.icarus.2024.116447","DOIUrl":"10.1016/j.icarus.2024.116447","url":null,"abstract":"<div><div>We use our 1-D chemical diffusive model to quantify the physical processes necessary to interpret the dayside ionospheric electron density profiles measured with the Mars Radio Science (MaRS) experiment onboard the Mars Express (MEX) and Radio Occultation Science Experiment (ROSE) onboard the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft. The electron density profiles selected for this study represent the southern high-latitude region of Mars, where the crustal magnetic field is strong and near-vertical in orientation. These electron density measurements have shown the topside plasma distribution with unusually large electron density (N_e) scale heights presumably in response to downward accelerating solar wind electrons along magnetic field lines. We find that the photochemical control of the Martian ionosphere ceases at a height well above the ionospheric peak. To interpret the measured ionospheric structure at altitudes where plasma transport dominates, we find it is necessary to impose field-aligned vertical plasma drifts most likely caused by the motion of neutral winds. The most interesting finding of this study is that both upward (between 30 ms⁻¹ and 60 ms⁻¹) and downward (between −12 ms⁻¹ and -90 ms⁻¹) drifts are required to maintain the topside N_e distribution comparable with the measured distribution. We also find that a fixed velocity boundary condition at the upper boundary with a sizeable upward ion velocity is needed to encounter any unexpected ion accumulation in the topside ionosphere to limit the Martian ionospheric outflow. Given the complex nature of neutral dynamics and its relationship to plasma transport processes over magnetic anomalies, we consider that a simple model, such as we have developed, is still capable of yielding valuable insights relating to the neutral wind system at Mars.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"429 ","pages":"Article 116447"},"PeriodicalIF":2.5,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134724","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":"Impact of a bimodal dust distribution on the 2018 Martian global dust storm with the NASA Ames Mars global climate model","authors":"Richard A. Urata ,&nbsp;Tanguy Bertrand ,&nbsp;Melinda A. Kahre ,&nbsp;R. John Wilson ,&nbsp;Alexandre M. Kling ,&nbsp;Michael J. Wolff","doi":"10.1016/j.icarus.2024.116446","DOIUrl":"10.1016/j.icarus.2024.116446","url":null,"abstract":"<div><div>Dust plays a critical role in the Martian climate, significantly impacting heating and circulation in the atmosphere. Global dust storms (GDS) are planet-encircling extreme dust events that occur every few Mars years with the most recent one happening in 2018, Mars Year (MY) 34. While they do occur on a relatively regular basis (recent ones occurring in 2001/MY25, 2007/MY28, 2018/MY34), much is still to be learned about the processes that lead to various characteristics of dust during these storms. Global climate models (GCMs) have been useful tools to interpret various observations made during the MY34 GDS. Here, we have implemented a bimodal dust lifting scheme in the NASA Ames Mars GCM. This new method for lifting dust splits the mass and number of dust particles lifted into multiple log-normal size modes as prescribed. We ran simulations assuming a small mode of dust with an effective radius of 0.3 μm and a large mode of dust with an effective radius of 3 μm lifted from the surface, with the amount of dust lifted in each mode prescribed as a fraction of the dust to be lifted. The dust is lifted to match a Mars Year 34 climatology map (Montabone et al., 2020), then transported by the general circulation and sediments with gravity. Dust is assumed to coagulate following Bertrand et al. (2022). Coagulation was found to have the greatest effect on the small mode of dust due to the large number of small dust particles lifted in that mode. We find that using a simple bimodal dust lifting scheme transports dust to higher altitude in the model simulations of the MY34 GDS, bringing the model closer to observations of atmospheric temperature, surface temperature, tides, etc.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"429 ","pages":"Article 116446"},"PeriodicalIF":2.5,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134557","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":"Vortex crystals at Jupiter’s poles: Emergence controlled by initial small-scale turbulence","authors":"Sihe Chen ,&nbsp;Andrew P. Ingersoll ,&nbsp;Cheng Li","doi":"10.1016/j.icarus.2024.116438","DOIUrl":"10.1016/j.icarus.2024.116438","url":null,"abstract":"<div><div>At the poles of Jupiter, cyclonic vortices are clustered together in patterns made up of equilateral triangles called vortex crystals. Such patterns are seen in laboratory flows but never before in a planetary atmosphere, where the planet’s rotation and gravity add new physics. Siegelman (2022b) used a one-layer quasi-geostrophic (QG) model with an infinite radius of deformation to study the emergence of vortex crystals from small-scale turbulence, and Li (2020) showed that shielding of the vortices is important for the stability of the vortex crystals. Here we use the shallow water (SW) equations at the pole of a rotating planet to study the emergence and evolution of vortices starting from an initial random pattern of small-scale turbulence. The flow is in a single layer with a free surface whose slope produces the horizontal pressure gradient force. With the planet’s radius and rotation used to define the units, only three input parameters are needed to define the system: the mean kinetic energy of the initial turbulence, the horizontal scale of the initial turbulence, and the radius of deformation of the undisturbed fluid layer. We identified a non-dimensional number, <span><math><mrow><mi>Δ</mi><mi>h</mi><mo>/</mo><mi>h</mi></mrow></math></span>, which is related to the relative layer thickness variation of the initial turbulence and determines whether the vortex crystal or chaotic patterns emerge: Small <span><math><mrow><mi>Δ</mi><mi>h</mi><mo>/</mo><mi>h</mi></mrow></math></span> values lead to vortex crystals, and large <span><math><mrow><mi>Δ</mi><mi>h</mi><mo>/</mo><mi>h</mi></mrow></math></span> values lead to chaotic patterns. The value <span><math><mrow><mi>Δ</mi><mi>h</mi><mo>/</mo><mi>h</mi></mrow></math></span> is related to the radius of deformation as <span><math><msubsup><mrow><mi>L</mi></mrow><mrow><mi>d</mi></mrow><mrow><mo>−</mo><mn>2</mn></mrow></msubsup></math></span>. This means that a large polar radius of deformation is positively correlated to the emergence of vortex crystals, and this implies either a polar atmosphere enriched with water or deeper roots for the vortices than previously estimated.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"429 ","pages":"Article 116438"},"PeriodicalIF":2.5,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134789","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Adaptive sampling with PIXL on the Mars Perseverance rover","authors":"Peter R. Lawson ,&nbsp;Tanya V. Kizovski ,&nbsp;Michael M. Tice ,&nbsp;Benton C. Clark ,&nbsp;Scott J. VanBommel ,&nbsp;David R. Thompson ,&nbsp;Lawrence A. Wade ,&nbsp;Robert W. Denise ,&nbsp;Christopher M. Heirwegh ,&nbsp;W. Timothy Elam ,&nbsp;Mariek E. Schmidt ,&nbsp;Yang Liu ,&nbsp;Abigail C. Allwood ,&nbsp;Martin S. Gilbert ,&nbsp;Benjamin J. Bornstein","doi":"10.1016/j.icarus.2024.116433","DOIUrl":"10.1016/j.icarus.2024.116433","url":null,"abstract":"<div><div>Planetary rovers can use onboard data analysis to adapt their measurement plan on the fly, improving the science value of data collected between commands from Earth. This paper describes the implementation of an adaptive sampling algorithm used by PIXL, the X-ray fluorescence spectrometer of the Mars 2020 <em>Perseverance</em> rover. PIXL is deployed using the rover arm to measure X-ray spectra of rocks with a scan density of several thousand points over an area of typically 5 × 7 mm. The adaptive sampling algorithm is programmed to recognize points of interest and to increase the signal-to-noise ratio at those locations by performing longer integrations. Two approaches are used to formulate the sampling rules based on past quantification data: (1) Expressions that isolate particular regions within a ternary compositional diagram, and (2) Machine learning rules that threshold for a high weight percent of particular compounds. The design of the rulesets are outlined and the performance of the algorithm is quantified using measurements from the surface of Mars. To our knowledge, PIXL’s adaptive sampling represents the first autonomous decision-making based on real-time compositional analysis by a spacecraft on the surface of another planet.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"429 ","pages":"Article 116433"},"PeriodicalIF":2.5,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134555","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Do icy dust aggregates break up when they pass the snow line?","authors":"Sin-iti Sirono","doi":"10.1016/j.icarus.2024.116430","DOIUrl":"10.1016/j.icarus.2024.116430","url":null,"abstract":"<div><div>Icy dust aggregates can break up when they pass the snow line or when a heating event occurs because of the sublimation of H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O ice. However, the original aggregate may absorb the fragment conducting the Brownian motion because the thickness of the icy mantle of a grain is less than the typical grain radius of <span><math><mrow><mo>∼</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>−</mo><mn>5</mn></mrow></msup><mspace></mspace></mrow></math></span>cm. On the other hand, the vapor pressure caused by the sublimated H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O molecules accelerates the fragment to escape. Rotation of the aggregate and electrostatic repulsion may also promote the escape of the fragment aggregate. Here, I determined a lower bound of the escaping fragment radius, including the effects of the vapor pressure, rotation, and electrostatic repulsion. It has been found that the breakup to the single grain does not occur, and the fragment radius strongly depends on the thickness of the icy mantle. The vapor pressure and the rotation produce fragments from large aggregates. The fragments escape from small aggregates by the electrostatic repulsion. Possible consequences of the breakup are discussed.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"429 ","pages":"Article 116430"},"PeriodicalIF":2.5,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hyperion (S VII): Shape, mosaic and control point network","authors":"A.E. Zubarev,&nbsp;I.E. Nadezhdina","doi":"10.1016/j.icarus.2024.116440","DOIUrl":"10.1016/j.icarus.2024.116440","url":null,"abstract":"<div><div>Saturn's odd-shaped satellite Hyperion is unique in its chaotic rotation. Owing to limited observational data, there is currently no functional model describing the object's changing orientation in space, commonly agreed upon. Consequently, there is also no established body-fixed reference frame, critical for the creation of mapping products. Using best 166 images obtained until the end of the Cassini mission we computed a new Control Point Network (CPN) of more than 2000 points for the satellite. On this basis, we established a reference frame working model for Hyperion, useful for estimates of new shape parameters and follow-up mapping products. Consequently, we find best-fit ellipsoid parameters of 180.9 × 129.0 × 102.0 km as well as new estimates for bulk density of 565 kg/km3, which is ∼4 % more than the values previously obtained by other researchers (P.C. Thomas; R.A. Jacobson). Based on the new CPN and reference frame, global mapping products were created, which included a gridded DEM and an orthomosaic (best resolution: 50 m/pixel).</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"429 ","pages":"Article 116440"},"PeriodicalIF":2.5,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134790","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":"Clusters of irregular patches on the Moon: A new GIS-based catalog","authors":"H.I. Hargitai ,&nbsp;P. Brož","doi":"10.1016/j.icarus.2024.116439","DOIUrl":"10.1016/j.icarus.2024.116439","url":null,"abstract":"<div><div>The aim of this work was to systematically map cluster-forming Irregular Patches (IPs) on the Moon. These features, formerly termed “Irregular Mare Patches”, are enigmatic features situated on the near side of the Moon, mostly in mare regions. IPs are pristine-looking features with textures at the meter scale, suggesting they formed millions of years ago on top of several-billion-year-old mare basalts. Morphologic and spectral studies could not provide conclusive evidence of their formative processes, or their age. Theories on their formation concentrate around three conflicting models - that they are formed by compact basalts and are only a few tens of millions of years old; that they are formed by mass wasting processes capable to remove regolith to this day; or that they are composed of lava foams and their age is the same as the host terrain's, i.e. billions of years. We present a GIS-based analysis to examine which formation model is supported by their geography. Previous catalogs mapped IPs ambiguously, with one single coordinate representing one unit or a group of units, with many isolated units around them remaining unmapped. To change that, we mapped isolated IPs individually as polygons because we wanted to reveal their areas and their local-scale distribution patterns, which were not identifiable from previous mapping efforts. We named the isolated, elemental depressions <em>Irregular Patches</em> to differentiate them from previous works. After the mapping, we grouped these IPs into clusters. This new mapping revealed that over 2700 Irregular Patches form more than 100 clusters, often displaying characteristic patterns. Their geologic context suggests that these patterns are controlled by subsurface geologic structures and processes. This way even without penetrating radar, recognizing the clustered nature of IPs on the Moon enables us to infer details of the IP hosting regions' subsurface structures and infer subsurface processes that led to their formation.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"429 ","pages":"Article 116439"},"PeriodicalIF":2.5,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134553","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigating the formation and growth of Titan's atmospheric aerosols using an experimental approach","authors":"Zoé Perrin ,&nbsp;Nathalie Carrasco ,&nbsp;Thomas Gautier ,&nbsp;Nathalie Ruscassier ,&nbsp;Julien Maillard ,&nbsp;Carlos Afonso ,&nbsp;Ludovic Vettier","doi":"10.1016/j.icarus.2024.116418","DOIUrl":"10.1016/j.icarus.2024.116418","url":null,"abstract":"<div><div>Titan has a climate system with similarities to Earth, including the presence of a thick atmosphere made up of several atmospheric layers. As on Earth, Titan's climate is influenced by several factors: the gaseous species making up the atmosphere, the energy deposited on the satellite, and solid organic aerosols. Indeed, numerous observations have revealed the presence of solid particles in the form of an opaque orange haze in Titan's atmosphere, influencing radiation balance and atmospheric dynamics, for example. However, the influence of these suspended solid particles seems to evolve according to the atmospheric altitude where they are located, certainly testifying to the presence of organic solids with different physico-chemical properties. At present, it is suspected that several populations/classes of atmospheric aerosols may form following different chemical pathways, and that aerosols undergo growth processes that modify their properties. In this experimental study, we present new observations on the evolution of morphological and chemical properties observed on Titan aerosol analogues, produced from a mixture of 20 % CH₄ and 80 % N₂ injected into a dusty RF plasma experiment. Using SEM (morphological) and FTICR-LDI-MS (chemical composition) analyses, we observe that properties evolve according to certain formation and growth mechanisms, which differentiate over time. The evolution of the neutral gaseous chemical composition analyzed in-situ by QMS in parallel shows correlations with the evolution of solid properties, testifying to the selective involvement of certain neutral products in the formation and growth mechanisms of solid aerosols. By linking the analyses of the gas phase and organic solids, we propose the calculation of an uptake coefficient between six neutral gaseous products (C₂H₂, HCN, C₂H₆, C₂H₃N, HC₃N, C₂N₂) and the surface of the Titan aerosol analogues produced in this study.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"429 ","pages":"Article 116418"},"PeriodicalIF":2.5,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Abrasion experiments of mineral, rock, and meteorite particles: Simulating regolith particles abrasion on airless bodies","authors":"Akira Tsuchiyama ,&nbsp;Hirotaka Yamaguchi ,&nbsp;Motohiro Ogawa ,&nbsp;Akiko M. Nakamura ,&nbsp;Tatsuhiro Michikami ,&nbsp;Kentaro Uesugi","doi":"10.1016/j.icarus.2024.116432","DOIUrl":"10.1016/j.icarus.2024.116432","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The shape of regolith particles on airless bodies, such as the Moon and asteroids, reflects the processes that occur on their surfaces. Recent studies have shown that particles on the asteroid Ryugu tend to be angular, whereas some particles on the asteroid Itokawa are rounded, with a larger portions of lunar particles also exhibiting a rounded shape. These differences are thought to result from abrasion, but experimental studies on particle abrasion have been lacking. In this study, we performed experiments simulating the abrasion caused by impact on airless bodies using minerals, rocks, and meteorites related to the Moon and asteroids. Aggregates of particles ranging in size from 1 to 2 mm (6.5 to10 g) were subjected to oscillation in a bead-milling apparatus to assess the amount of abrasion at different oscillation rates, varying from 100 to 3000 rpm for 0.33 to 720 min. The amount of abrasion increased with time and oscillation rate, following a power-law relationship. Once the oscillation rate exceeded a certain threshold, abrasion proceeded rapidly. At rates above 1000 rpm, particles floated and rubbed against each other due to the vertical oscillation of the container, leading to significant abrasion, whereas at rates below 300 rpm, the particles were constrained by Earth's gravity, resulting in minimal abrasion. This indicates that experiments conducted at ≥1000 rpm effectively simulated the abrasion that occurs on the Moon and asteroids. Scanning electron microscopy was used to observe the particles before and after the experiments, and X-ray microtomography was employed to track the shape changes of individual traceable particles and to measure the three-axial lengths of approximately160 particles. As abrasion progressed, some of the corners and edges of the particles were initially chipped, eventually leading to rounded corners, edges, and surfaces. This process corresponds to “adhesive wear” in tribology, which is caused by tangential relative motion between materials. In carbonaceous chondrite samples, particles tended to split along pre-existing cracks. The particles became smaller, their angularity decreased, and their sphericity increased, while the overall 3D shape of individual particles did not significantly change from their original form; however, the average three-axial ratio became more isotropic. These results indicate that the change in the average three-axial ratio of the Moon and Itokawa regolith particles can be explained by abrasion, as previously proposed. Based on the observed abrasion rates, we discuss the potential for abrasion to be caused by the impact-induced particle motion on the Moon and asteroids, considering models of regolith convection, excavation flow, and maximum acceleration. Although this discussion is rough and only semi-quantitative due to many assumptions, experimental errors, and uncertainties in the models, the results suggest that abrasion can occur on the Moon due to impact-induced p","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"429 ","pages":"Article 116432"},"PeriodicalIF":2.5,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143135205","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":"Distinguishing potential organic biosignatures on ocean worlds from abiotic geochemical products using thermodynamic calculations","authors":"Jordyn A. Robare ,&nbsp;Everett L. Shock","doi":"10.1016/j.icarus.2024.116431","DOIUrl":"10.1016/j.icarus.2024.116431","url":null,"abstract":"<div><div>The search for life in our solar system often involves efforts to detect organic molecules, which have been found on many extraterrestrial bodies, including planets, moons, meteorites, comets, and asteroids. These chemical signatures are not typically thought of as biosignatures because we know that organic synthesis can occur through abiotic processes. Therefore, development of methods for distinguishing biotic and abiotic biosignatures would enable interpretation of data collected from habitability and life-detection missions. Life on Earth harnesses energy-releasing reactions to power biosynthesis reactions, which often require energy. Using thermodynamic data, we can quantify the energy required for organic synthesis. If an organic molecule is detected in an abundance that is thermodynamically unstable, then it is possible that life coupled its synthesis to other energy-releasing reactions. On the other hand, if an organic molecule is detected in an abundance that is thermodynamically stable, then abiotic synthesis was plausible. This sorting framework can be applied to the search for life wherever we have geochemical data. One such example is Saturn's moon Enceladus. Small compounds involving the elements that comprise the majority of biomass were detected by the Cassini spacecraft in the plume gas erupting from the subsurface ocean. Using Enceladus as an example, we demonstrate the utility of thermodynamic calculations for distinguishing biosignatures and show that organic synthesis is often favorable using the carbon sources available on Enceladus. While these results may lead us to conclude that hypothetical organic signatures on Enceladus are abiotic, this framework can be applied to other environments in the search for genuine biosignatures.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"429 ","pages":"Article 116431"},"PeriodicalIF":2.5,"publicationDate":"2024-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134792","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}