Pub Date : 2025-12-13DOI: 10.1016/j.icarus.2025.116917
Alain S.J. Khayat, Michael D. Smith, Scott D. Guzewich
Surface-atmosphere interactions play a major role in shaping the north polar layered deposits (NPLD) on Mars, the major source of atmospheric water during northern spring and summer seasons. Extensive work has been undertaken to study and understand polar processes and their evolutionary patterns. High-resolution water vapor retrievals provide context into these polar processes, in particular with respect to the sublimation of surface ice and the volatile transport across the NPLD. We here report the first high-spatial resolution (∼ 160 m) retrievals of water vapor over the north polar region, including the NPLD, and extending between MY 28, Ls = 113° (September 29, 2006) and MY 31, Ls = 115° (May 21, 2012). We have processed 1.7 million near-infrared spectra from hyperspectral observations returned by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) aboard the Mars Reconnaissance Orbiter (MRO) to provide the column-integrated water vapor abundance (pr-μm), after improving our radiative transfer model to accommodate the presence of surface ice. Our findings demonstrate that water vapor can accumulate significantly at the bottom of polar troughs, acting as a catalyst for trough cloud formation. We further identify scenarios where elevated water vapor levels correlate with surface ice rather than topography, and conversely, situations where combined sloped terrain and surface ice did not yield significant water vapor increases. These critical water vapor results would help understand the formation of trough clouds, a direct observation of the ice migration processes in the NPLD, hence the evolution of the north polar cap.
地表-大气相互作用在形成火星上的北极层状沉积物（NPLD）中起着重要作用，这是火星北部春季和夏季大气水的主要来源。已经进行了大量的工作来研究和了解极地过程及其演化模式。高分辨率的水汽检索提供了这些极地过程的背景，特别是关于表面冰的升华和通过NPLD的挥发性运输。在此，我们报告了包括NPLD在内的北极地区首次高空间分辨率（~ 160 m）的水汽检索，并在MY 28， Ls = 113°（2006年9月29日）和MY 31， Ls = 115°（2012年5月21日）之间扩展。我们对火星勘测轨道器（MRO）上的火星紧凑侦察成像光谱仪（CRISM）传回的高光谱观测数据中的170万张近红外光谱进行了处理，以提供柱集成的水蒸气丰度（pr-μm），并改进了我们的辐射传输模型，以适应表面冰的存在。我们的研究结果表明，水蒸气可以在极地槽底部大量积累，作为槽云形成的催化剂。我们进一步确定了水汽水平升高与表面冰而不是地形相关的情况，相反，斜坡地形和表面冰结合的情况不会产生显著的水汽增加。这些临界水蒸气的结果将有助于了解槽云的形成，直接观察NPLD的冰迁移过程，从而了解北极帽的演变。
{"title":"Tracking the non-uniformity in atmospheric water vapor over the north polar layered deposits on Mars using high-resolution observations by MRO/CRISM","authors":"Alain S.J. Khayat, Michael D. Smith, Scott D. Guzewich","doi":"10.1016/j.icarus.2025.116917","DOIUrl":"10.1016/j.icarus.2025.116917","url":null,"abstract":"<div><div>Surface-atmosphere interactions play a major role in shaping the north polar layered deposits (NPLD) on Mars, the major source of atmospheric water during northern spring and summer seasons. Extensive work has been undertaken to study and understand polar processes and their evolutionary patterns. High-resolution water vapor retrievals provide context into these polar processes, in particular with respect to the sublimation of surface ice and the volatile transport across the NPLD. We here report the first high-spatial resolution (∼ 160 m) retrievals of water vapor over the north polar region, including the NPLD, and extending between MY 28, L<sub>s</sub> = 113° (September 29, 2006) and MY 31, L<sub>s</sub> = 115° (May 21, 2012). We have processed 1.7 million near-infrared spectra from hyperspectral observations returned by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) aboard the Mars Reconnaissance Orbiter (MRO) to provide the column-integrated water vapor abundance (pr-μm), after improving our radiative transfer model to accommodate the presence of surface ice. Our findings demonstrate that water vapor can accumulate significantly at the bottom of polar troughs, acting as a catalyst for trough cloud formation. We further identify scenarios where elevated water vapor levels correlate with surface ice rather than topography, and conversely, situations where combined sloped terrain and surface ice did not yield significant water vapor increases. These critical water vapor results would help understand the formation of trough clouds, a direct observation of the ice migration processes in the NPLD, hence the evolution of the north polar cap.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"447 ","pages":"Article 116917"},"PeriodicalIF":3.0,"publicationDate":"2025-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145797655","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}
JAXA's Hayabusa2 spacecraft executed several low-altitude (down to <25 m) operations during its proximity maneuvers on asteroid Ryugu. Analysis of images acquired during the ascent (i.e., soon after thruster gas injection) revealed that many surface boulders were in motion on Ryugu. While previous studies documented boulder movement resulting from physical contact, such as the Hayabusa2 touchdowns and NASA's OSIRIS-REx sampling operations, this study uniquely confirms movement induced by remote disturbance through thruster gas. Boulder movement was analyzed using a series of Optical Navigation Camera (ONC) images taken during the DO-S01 operation, where the greatest number of boulders displayed movement over an extended period among the low-altitude descents by Hayabusa2. 74 moving boulders were identified, and the largest one was approximately 40 cm in diameter. The maximum velocity was 1.7 cm/s. The momentum imparted to the rock from the thruster injection pressure exceeded the observed momentum, suggesting that the boulder motion was induced directly by thruster gas, and subsequent friction with the surface decelerated the boulders. Notably, the observations revealed sustained boulder motion lasting more than 10 min, during which the trajectories of some boulders changed, suggesting multiple bouncing on the asteroid surfaces. This observation implies a significant restitution coefficient for boulder motion on microgravity asteroids, allowing for multiple bouncing. However, shadow measurements indicate minimal or zero leap height. This indicates that a mode of motion akin to rolling on the surface should not be ruled out either. Comparison between moving and stationary boulders showed that the numbers of the moving boulders relative to the stational is lower for smaller size. This suggests that the inertia of larger boulders, making them harder to stop, has stronger effect than the ease of acceleration in smaller boulders. These findings on the characteristics of motion are pivotal for predicting the dynamical response of surface materials after physical disturbances on asteroids. This understanding is crucial for deciphering the mode of surface renewal in near-Earth asteroids and for planning expected proximity observations of near-Earth objects (e.g., OSIRIS-APEX and RAMSES missions).
{"title":"Boulder motions on asteroid Ryugu induced by thruster gas disturbance by Hayabusa2","authors":"Naoya Sakatani , Shingo Kameda , Kosuke Kitsunai , Hiroshi Kikuchi , Shota Kikuchi , Yuto Takei , Yuya Mimasu , Osamu Mori , Toru Kouyama , Tomokatsu Morota , Eri Tatsumi , Yuichiro Cho , Manabu Yamada , Yasuhiro Yokota , Moe Matsuoka , Chikatoshi Honda , Hidehiko Suzuki , Masahiko Hayakawa , Kazuo Yoshioka , Kazunori Ogawa , Seiji Sugita","doi":"10.1016/j.icarus.2025.116916","DOIUrl":"10.1016/j.icarus.2025.116916","url":null,"abstract":"<div><div>JAXA's Hayabusa2 spacecraft executed several low-altitude (down to <25 m) operations during its proximity maneuvers on asteroid Ryugu. Analysis of images acquired during the ascent (i.e., soon after thruster gas injection) revealed that many surface boulders were in motion on Ryugu. While previous studies documented boulder movement resulting from physical contact, such as the Hayabusa2 touchdowns and NASA's OSIRIS-REx sampling operations, this study uniquely confirms movement induced by remote disturbance through thruster gas. Boulder movement was analyzed using a series of Optical Navigation Camera (ONC) images taken during the DO-S01 operation, where the greatest number of boulders displayed movement over an extended period among the low-altitude descents by Hayabusa2. 74 moving boulders were identified, and the largest one was approximately 40 cm in diameter. The maximum velocity was 1.7 cm/s. The momentum imparted to the rock from the thruster injection pressure exceeded the observed momentum, suggesting that the boulder motion was induced directly by thruster gas, and subsequent friction with the surface decelerated the boulders. Notably, the observations revealed sustained boulder motion lasting more than 10 min, during which the trajectories of some boulders changed, suggesting multiple bouncing on the asteroid surfaces. This observation implies a significant restitution coefficient for boulder motion on microgravity asteroids, allowing for multiple bouncing. However, shadow measurements indicate minimal or zero leap height. This indicates that a mode of motion akin to rolling on the surface should not be ruled out either. Comparison between moving and stationary boulders showed that the numbers of the moving boulders relative to the stational is lower for smaller size. This suggests that the inertia of larger boulders, making them harder to stop, has stronger effect than the ease of acceleration in smaller boulders. These findings on the characteristics of motion are pivotal for predicting the dynamical response of surface materials after physical disturbances on asteroids. This understanding is crucial for deciphering the mode of surface renewal in near-Earth asteroids and for planning expected proximity observations of near-Earth objects (e.g., OSIRIS-APEX and RAMSES missions).</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"448 ","pages":"Article 116916"},"PeriodicalIF":3.0,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145882260","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}
Pub Date : 2025-12-12DOI: 10.1016/j.icarus.2025.116915
Rahil Makadia , Steven R. Chesley , Davide Farnocchia , Brent W. Barbee , Siegfried Eggl
We introduce a new method for selecting kinetic impactor target sites on near-Earth asteroids. Most asteroids that possess a significant impact risk with Earth admit multiple impacting trajectories. Uncontrolled deflection of such asteroids might dismiss the immediate impact risk but can also push the asteroid into a ‘keyhole’, which would lead to a future impact. Our method maps potential outcomes of a kinetic impactor mission to the surface of the asteroid, allowing us to identify the optimal target site and rotation phase that minimizes the risk of pushing the asteroid off the Earth and into a keyhole. In this work, we illustrate this process using the keyholes for asteroid (101955) Bennu. We map the Bennu keyholes onto shape models of various asteroids to demonstrate the influence of shapes on the deflection outcomes. By computing the per-facet impact probability for different shapes, we can assess the dependence of the optimal target site on the asteroid’s shape and spin state. Our results indicate that an optimal kinetic impact mission must take the spin state and shape of the target asteroid into account to minimize post-deflection impact risk. We also assess the effect of varying the targeting uncertainty of the kinetic impactor spacecraft in anticipation of future improvements. This work provides a framework for selecting optimal timing and target locations for kinetic impact missions at near-Earth asteroids, which can be used by mission designers to inform future asteroid impact hazard mitigation efforts.
{"title":"Keyhole-aware target site selection for kinetic impact missions to near-Earth asteroids","authors":"Rahil Makadia , Steven R. Chesley , Davide Farnocchia , Brent W. Barbee , Siegfried Eggl","doi":"10.1016/j.icarus.2025.116915","DOIUrl":"10.1016/j.icarus.2025.116915","url":null,"abstract":"<div><div>We introduce a new method for selecting kinetic impactor target sites on near-Earth asteroids. Most asteroids that possess a significant impact risk with Earth admit multiple impacting trajectories. Uncontrolled deflection of such asteroids might dismiss the immediate impact risk but can also push the asteroid into a ‘keyhole’, which would lead to a future impact. Our method maps potential outcomes of a kinetic impactor mission to the surface of the asteroid, allowing us to identify the optimal target site and rotation phase that minimizes the risk of pushing the asteroid off the Earth and into a keyhole. In this work, we illustrate this process using the keyholes for asteroid (101955) Bennu. We map the Bennu keyholes onto shape models of various asteroids to demonstrate the influence of shapes on the deflection outcomes. By computing the per-facet impact probability for different shapes, we can assess the dependence of the optimal target site on the asteroid’s shape and spin state. Our results indicate that an optimal kinetic impact mission must take the spin state and shape of the target asteroid into account to minimize post-deflection impact risk. We also assess the effect of varying the targeting uncertainty of the kinetic impactor spacecraft in anticipation of future improvements. This work provides a framework for selecting optimal timing and target locations for kinetic impact missions at near-Earth asteroids, which can be used by mission designers to inform future asteroid impact hazard mitigation efforts.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"447 ","pages":"Article 116915"},"PeriodicalIF":3.0,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145797666","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}
Pub Date : 2025-12-11DOI: 10.1016/j.icarus.2025.116912
Jayesh Pabari , M. Roshni
During summer in Mars' southern hemisphere, dust devils/storms routinely sweep across the surface, lofting massive quantities of dust that drastically lower the atmosphere's electrical conductivity. In this study, we investigate a dust devil triggered under either low-dust or high-dust conditions, which is set by a prior dust activity, and show outcomes of its electrification by varying atmospheric conductivity in existing models. By tracking how the electric field evolves and comparing it to Mars' breakdown threshold, we determined a narrow range of conductivity from [1–9.6] × 10−13 S/m, as the condition where near surface lightning becomes feasible. We also examined conductivity profiles spanning few Martian years, confirming that these low-conductivity conditions indeed recur on Mars.
By analyzing time-domain evolution of electric field in Martian dust devils, we derived the discharge current characteristics based on allowable streamer speeds on Mars. The current provided the three moments in the three-component analysis, viz. current moment, charge moment and radiation moment, to estimate electromagnetic radiation's frequency spectrum. The electrical discharge launches extremely low frequency waves in surface-ionosphere cavity, potentially exciting Schumann Resonances on Mars. We further compute the resonator's quality factor and signal attenuation under different dust conditions. Our findings highlight that dust-driven electrical discharges on Mars could be strong enough to generate detectable Extremely Low Frequency signals. The work could be useful to plan observations of lightning or Schumann Resonance, the most promising detection related to electrical activity on the Red Planet, by a future mission.
{"title":"Electrification in Martian dust devils: Possibility and implications","authors":"Jayesh Pabari , M. Roshni","doi":"10.1016/j.icarus.2025.116912","DOIUrl":"10.1016/j.icarus.2025.116912","url":null,"abstract":"<div><div>During summer in Mars' southern hemisphere, dust devils/storms routinely sweep across the surface, lofting massive quantities of dust that drastically lower the atmosphere's electrical conductivity. In this study, we investigate a dust devil triggered under either low-dust or high-dust conditions, which is set by a prior dust activity, and show outcomes of its electrification by varying atmospheric conductivity in existing models. By tracking how the electric field evolves and comparing it to Mars' breakdown threshold, we determined a narrow range of conductivity from [1–9.6] × 10<sup>−13</sup> S/m, as the condition where near surface lightning becomes feasible. We also examined conductivity profiles spanning few Martian years, confirming that these low-conductivity conditions indeed recur on Mars.</div><div>By analyzing time-domain evolution of electric field in Martian dust devils, we derived the discharge current characteristics based on allowable streamer speeds on Mars. The current provided the three moments in the three-component analysis, viz. current moment, charge moment and radiation moment, to estimate electromagnetic radiation's frequency spectrum. The electrical discharge launches extremely low frequency waves in surface-ionosphere cavity, potentially exciting Schumann Resonances on Mars. We further compute the resonator's quality factor and signal attenuation under different dust conditions. Our findings highlight that dust-driven electrical discharges on Mars could be strong enough to generate detectable Extremely Low Frequency signals. The work could be useful to plan observations of lightning or Schumann Resonance, the most promising detection related to electrical activity on the Red Planet, by a future mission.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"447 ","pages":"Article 116912"},"PeriodicalIF":3.0,"publicationDate":"2025-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145797664","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}
Pub Date : 2025-12-10DOI: 10.1016/j.icarus.2025.116911
Suyun Wang, Kazuma Hiramatsu
Electromagnetic properties of regolith are critical for understanding planetary subsurface structure and resource potential. However, their behavior in the terahertz (THz) frequency range remains poorly characterized. THz waves are particularly sensitive to fine-grained structure and hydration state, offering new opportunities for high-resolution planetary subsurface sensing. To investigate these interactions, we performed THz reflection measurements on FJS-1 lunar regolith simulants while varying bulk density (1.44–1.81 g/cm) and volumetric water content (0–46.1%). Measurements were conducted across 220–500 GHz using dual polarizations (HH, VV) and angle-resolved configurations (20–70° incidence angles). Results show clear density and hydration dependence of THz reflection coefficients, with Brewster angle shifts indicating changes in dielectric contrast. VV polarization demonstrated significantly higher sensitivity to both variables than HH polarization, enabling improved discrimination of subsurface properties. Results provide new experimental constraints on THz wave propagation in granular materials under controlled conditions, establishing a measurement framework applicable to future planetary remote sensing strategies for landing site assessment and water detection.
{"title":"Terahertz characteristics of regolith simulants: Effects of bulk density and water content on electromagnetic response for planetary remote sensing","authors":"Suyun Wang, Kazuma Hiramatsu","doi":"10.1016/j.icarus.2025.116911","DOIUrl":"10.1016/j.icarus.2025.116911","url":null,"abstract":"<div><div>Electromagnetic properties of regolith are critical for understanding planetary subsurface structure and resource potential. However, their behavior in the terahertz (THz) frequency range remains poorly characterized. THz waves are particularly sensitive to fine-grained structure and hydration state, offering new opportunities for high-resolution planetary subsurface sensing. To investigate these interactions, we performed THz reflection measurements on FJS-1 lunar regolith simulants while varying bulk density (1.44–1.81 g/cm<span><math><msup><mrow></mrow><mrow><mn>3</mn></mrow></msup></math></span>) and volumetric water content (0–46.1%). Measurements were conducted across 220–500 GHz using dual polarizations (HH, VV) and angle-resolved configurations (20–70° incidence angles). Results show clear density and hydration dependence of THz reflection coefficients, with Brewster angle shifts indicating changes in dielectric contrast. VV polarization demonstrated significantly higher sensitivity to both variables than HH polarization, enabling improved discrimination of subsurface properties. Results provide new experimental constraints on THz wave propagation in granular materials under controlled conditions, establishing a measurement framework applicable to future planetary remote sensing strategies for landing site assessment and water detection.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"449 ","pages":"Article 116911"},"PeriodicalIF":3.0,"publicationDate":"2025-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146035950","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}
Pub Date : 2025-12-10DOI: 10.1016/j.icarus.2025.116910
Sean N. Raymond , Nathan A. Kaib
An instability among the giant planets’ orbits can match many aspects of the Solar System’s current orbital architecture. We explore the possibility that this dynamical instability was triggered by the close passage of a star or substellar object during the Sun’s embedded cluster phase. We run N-body simulations starting with the giant planets in a resonant chain and an outer planetesimal disk, with a wide-enough planet-disk separation to preserve the planets’ orbital stability for Myr. We subject the system to a single flyby, testing a wide range in flyby mass, velocity and closest approach distance. We find a variety of outcomes, from flybys that over-excite the system (or strip the planets entirely) to flybys too weak to perturb the planets at all. An intermediate range of flybys triggers a dynamical instability that matches the present-day Solar System. Successful simulations – that match the giant planets’ orbits without over-exciting the cold classical Kuiper belt – are characterized by the flyby of a substellar object () passing within 20 au of the Sun. We performed Monte Carlo simulations of the Sun’s birth cluster phase, parameterized by the product of the stellar density and the cluster lifetime . The balance between under- and over-excitation of the young Solar System is at Myr pc−3, in a range consistent with previous work. We find a probability of 1% that the Solar System’s dynamical instability was triggered by a substellar flyby. The probability increases to 5% if the occurrence rate of free-floating planets and low-mass brown dwarfs is modestly higher than predicted by standard stellar initial mass functions.
{"title":"Was the Solar System’s dynamical instability triggered by a (sub)stellar flyby?","authors":"Sean N. Raymond , Nathan A. Kaib","doi":"10.1016/j.icarus.2025.116910","DOIUrl":"10.1016/j.icarus.2025.116910","url":null,"abstract":"<div><div>An instability among the giant planets’ orbits can match many aspects of the Solar System’s current orbital architecture. We explore the possibility that this dynamical instability was triggered by the close passage of a star or substellar object during the Sun’s embedded cluster phase. We run N-body simulations starting with the giant planets in a resonant chain and an outer planetesimal disk, with a wide-enough planet-disk separation to preserve the planets’ orbital stability for <span><math><mrow><mo>></mo><mn>100</mn></mrow></math></span> Myr. We subject the system to a single flyby, testing a wide range in flyby mass, velocity and closest approach distance. We find a variety of outcomes, from flybys that over-excite the system (or strip the planets entirely) to flybys too weak to perturb the planets at all. An intermediate range of flybys triggers a dynamical instability that matches the present-day Solar System. Successful simulations – that match the giant planets’ orbits without over-exciting the cold classical Kuiper belt – are characterized by the flyby of a substellar object (<span><math><mrow><mn>3</mn><mo>−</mo><mn>30</mn><msub><mrow><mi>M</mi></mrow><mrow><mi>Jup</mi></mrow></msub></mrow></math></span>) passing within 20 au of the Sun. We performed Monte Carlo simulations of the Sun’s birth cluster phase, parameterized by the product of the stellar density <span><math><mi>η</mi></math></span> and the cluster lifetime <span><math><mi>T</mi></math></span>. The balance between under- and over-excitation of the young Solar System is at <span><math><mrow><mi>η</mi><mi>T</mi><mo>≈</mo><mn>5</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>4</mn></mrow></msup></mrow></math></span> Myr pc<sup>−3</sup>, in a range consistent with previous work. We find a probability of <span><math><mo>∼</mo></math></span>1% that the Solar System’s dynamical instability was triggered by a substellar flyby. The probability increases to <span><math><mo>∼</mo></math></span>5% if the occurrence rate of free-floating planets and low-mass brown dwarfs is modestly higher than predicted by standard stellar initial mass functions.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"447 ","pages":"Article 116910"},"PeriodicalIF":3.0,"publicationDate":"2025-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145748592","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}
Pub Date : 2025-12-06DOI: 10.1016/j.icarus.2025.116905
Yiqi Li , Xiaobing Sun , Xiao Liu , Honglian Huang , Xiaobing Zheng , Yichen Wei , Yizhe Fan , Shun Yao
Using the PyMieDAP radiative-transfer model, we constructed a multi-layer representation of Venus clouds and haze and designed multiple observing scenarios to quantify the sensitivity of intensity and polarization measurements to aerosol parameters as a function of altitude, wavelength, and phase angle. Intensity observations are more sensitive to variations in lower-cloud microphysical parameters (, ), whereas polarization at small phase angles () is dominated by single scattering and is therefore more sensitive to upper-cloud parameters. Introducing a joint-observation mode increases the degrees of freedom for signal (DFS) by about 3; further adding potential Venspec-H near-infrared bands yields an additional DFS. The optimal observing geometry depends on phase angle: upper-cloud parameters are best constrained at ; lower-cloud parameters and the real refractive index () at . The upper-cloud number density () is best retrieved near . For future instrument design, appropriate aerosol-window bands should be selected across 650 nm–; under the joint-observation mode, we recommend polarization accuracy and intensity (radiance) accuracy to optimize retrieval accuracy.
{"title":"Information content analysis of venus clouds and haze based on polarization bands of the SPICAV IR and Venspec-H instruments","authors":"Yiqi Li , Xiaobing Sun , Xiao Liu , Honglian Huang , Xiaobing Zheng , Yichen Wei , Yizhe Fan , Shun Yao","doi":"10.1016/j.icarus.2025.116905","DOIUrl":"10.1016/j.icarus.2025.116905","url":null,"abstract":"<div><div>Using the <span>PyMieDAP</span> radiative-transfer model, we constructed a multi-layer representation of Venus clouds and haze and designed multiple observing scenarios to quantify the sensitivity of intensity and polarization measurements to aerosol parameters as a function of altitude, wavelength, and phase angle. Intensity observations are more sensitive to variations in lower-cloud microphysical parameters (<span><math><msubsup><mrow><mi>r</mi></mrow><mrow><mi>g</mi></mrow><mrow><mn>3</mn></mrow></msubsup></math></span>, <span><math><msubsup><mrow><mi>σ</mi></mrow><mrow><mi>g</mi></mrow><mrow><mn>3</mn></mrow></msubsup></math></span>), whereas polarization at small phase angles (<span><math><mrow><mi>α</mi><mo>≈</mo><mn>15</mn><mo>°</mo></mrow></math></span>) is dominated by single scattering and is therefore more sensitive to upper-cloud parameters. Introducing a joint-observation mode increases the degrees of freedom for signal (DFS) by about 3; further adding potential <span>Venspec-H</span> near-infrared bands yields an additional <span><math><mrow><mo>∼</mo><mn>0</mn><mo>.</mo><mn>6</mn></mrow></math></span> DFS. The optimal observing geometry depends on phase angle: upper-cloud parameters are best constrained at <span><math><mrow><mi>α</mi><mo>></mo><mn>140</mn><mo>°</mo></mrow></math></span>; lower-cloud parameters and the real refractive index (<span><math><msub><mrow><mi>n</mi></mrow><mrow><mi>r</mi></mrow></msub></math></span>) at <span><math><mrow><mi>α</mi><mo><</mo><mn>20</mn><mo>°</mo></mrow></math></span>. The upper-cloud number density (<span><math><msubsup><mrow><mi>V</mi></mrow><mrow><mn>0</mn></mrow><mrow><mn>2</mn></mrow></msubsup></math></span>) is best retrieved near <span><math><mrow><mi>α</mi><mo>≈</mo><mn>80</mn><mo>°</mo></mrow></math></span>. For future instrument design, appropriate aerosol-window bands should be selected across 650 nm–<span><math><mrow><mn>2</mn><mo>.</mo><mn>5</mn><mspace></mspace><mi>μ</mi><mi>m</mi></mrow></math></span>; under the joint-observation mode, we recommend polarization accuracy <span><math><mrow><mo>≤</mo><mn>0</mn><mo>.</mo><mn>002</mn></mrow></math></span> and intensity (radiance) accuracy <span><math><mrow><mo>≤</mo><mn>3</mn><mtext>%</mtext></mrow></math></span> to optimize retrieval accuracy.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"447 ","pages":"Article 116905"},"PeriodicalIF":3.0,"publicationDate":"2025-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145748591","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}
Pub Date : 2025-12-05DOI: 10.1016/j.icarus.2025.116902
J.M. Comellas , A. Essunfeld , R.A. Morris , P.J. Gasda , N.L. Lanza , S.K. Sharma , A.K. Huynh , D. Das , C.C. Bedford , E. Dehouck , B.C. Clark , W. Fischer , V. Lueth , D. Delapp , S. Clegg , O. Gasnault , R.C. Wiens
Manganese plays a crucial role as a paleo-environmental and geological indicator due to its sensitivity to redox potential and pH variations in the environment. On Earth, the association between the rise of atmospheric oxygen during the Great Oxidation Event and the presence of Mn in the sedimentary rock record underscores its significance. In this study, we reexamined ChemCam targets from the first 600 sols of the Mars Science Laboratory mission, focusing on identifying instances of above-average Mn within these targets. These elevated-Mn targets were categorized into distinct geologic classes, revealing a pattern linking heightened Mn levels with diagenetically altered materials, such as calcium-sulfate veins and concretions, as well as clay minerals within the same targets, indicating a compelling relationship between Mn enrichment and diagenetic processes. High concentrations of Mn were observed in chemically altered targets, suggesting the occurrence of multiple fluid events: the first to alter the material and the second to deposit Mn. The observed patterns suggest multiple diagenetic events and redox cycling that facilitated the deposition and transport of Mn subsequent to the initial dissolution of basaltic materials. This research sheds light on the complexity of martian diagenetic processes and their implications for the planet’s environmental evolution.
{"title":"Elevated-Mn ChemCam targets illuminating Mn redox cycling and diagenesis in the Bradbury Rise, Gale Crater, Mars","authors":"J.M. Comellas , A. Essunfeld , R.A. Morris , P.J. Gasda , N.L. Lanza , S.K. Sharma , A.K. Huynh , D. Das , C.C. Bedford , E. Dehouck , B.C. Clark , W. Fischer , V. Lueth , D. Delapp , S. Clegg , O. Gasnault , R.C. Wiens","doi":"10.1016/j.icarus.2025.116902","DOIUrl":"10.1016/j.icarus.2025.116902","url":null,"abstract":"<div><div>Manganese plays a crucial role as a paleo-environmental and geological indicator due to its sensitivity to redox potential and pH variations in the environment. On Earth, the association between the rise of atmospheric oxygen during the Great Oxidation Event and the presence of Mn in the sedimentary rock record underscores its significance. In this study, we reexamined ChemCam targets from the first 600 sols of the Mars Science Laboratory mission, focusing on identifying instances of above-average Mn within these targets. These elevated-Mn targets were categorized into distinct geologic classes, revealing a pattern linking heightened Mn levels with diagenetically altered materials, such as calcium-sulfate veins and concretions, as well as clay minerals within the same targets, indicating a compelling relationship between Mn enrichment and diagenetic processes. High concentrations of Mn were observed in chemically altered targets, suggesting the occurrence of multiple fluid events: the first to alter the material and the second to deposit Mn. The observed patterns suggest multiple diagenetic events and redox cycling that facilitated the deposition and transport of Mn subsequent to the initial dissolution of basaltic materials. This research sheds light on the complexity of martian diagenetic processes and their implications for the planet’s environmental evolution.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"447 ","pages":"Article 116902"},"PeriodicalIF":3.0,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145748588","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}
Pub Date : 2025-12-05DOI: 10.1016/j.icarus.2025.116904
Francesco Axel Pio Romio , Gianni Lobosco , Francesco Sauro , Riccardo Pozzobon , Alessandro Marraffa
Lava tubes, also known as“pyroducts”, are caves found on terrestrial volcanoes and on analogue terrains on the Moon and Mars. Their morphometry is the expression of genetic parameters, which are often not well understood, like lava effusion rates and rheology, and cooling rates. Lunar and Martian tubes could offer protection from radiation, micrometeorites, and extreme temperatures, making them promising candidates for future extraterrestrial habitats. Models used in planetary geology and space architectural studies rely on a few terrestrial examples and notional geometries. This paper introduces Pyroduct, the first fully parametric 3D lava tube generator, developed as a free plug-in for Grasshopper in Rhinoceros 3D. Based on a wide catalog of terrestrial lava tube cross-sections, Pyroduct enables the simulation of realistic cave environments for planetary research. It also supports terrestrial applications, offering a cost-effective method for reconstructing lava tubes' 3D geometries for the evaluation of volcanic hazard and creation of VR models.
{"title":"Pyroduct: A novel parametric software for the simulation of terrestrial, lunar, and Martian lava tubes","authors":"Francesco Axel Pio Romio , Gianni Lobosco , Francesco Sauro , Riccardo Pozzobon , Alessandro Marraffa","doi":"10.1016/j.icarus.2025.116904","DOIUrl":"10.1016/j.icarus.2025.116904","url":null,"abstract":"<div><div>Lava tubes, also known as“pyroducts”, are caves found on terrestrial volcanoes and on analogue terrains on the Moon and Mars. Their morphometry is the expression of genetic parameters, which are often not well understood, like lava effusion rates and rheology, and cooling rates. Lunar and Martian tubes could offer protection from radiation, micrometeorites, and extreme temperatures, making them promising candidates for future extraterrestrial habitats. Models used in planetary geology and space architectural studies rely on a few terrestrial examples and notional geometries. This paper introduces Pyroduct, the first fully parametric 3D lava tube generator, developed as a free plug-in for Grasshopper in Rhinoceros 3D. Based on a wide catalog of terrestrial lava tube cross-sections, Pyroduct enables the simulation of realistic cave environments for planetary research. It also supports terrestrial applications, offering a cost-effective method for reconstructing lava tubes' 3D geometries for the evaluation of volcanic hazard and creation of VR models.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"447 ","pages":"Article 116904"},"PeriodicalIF":3.0,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145797667","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}
Pub Date : 2025-12-05DOI: 10.1016/j.icarus.2025.116903
Pruthviraj J. Acharya , Isaac B. Smith , Aymeric Spiga
The Cold and Bright Anomalies (CABAs) and Warm and Dark Anomalies (WADAs) on the North Polar Layered Deposit (NPLD) are distinct seasonal phenomena on Mars. CABAs, which are colder and brighter during early summer, and WADAs, which are warmer and darker in late summer, were analyzed across Mars Years (MYs) 29–35, focusing on solar longitudes (Ls) between 30° and 170°. Investigating temperature, albedo, wind patterns, and topography at multiple sites, we found that CABAs emerge around Ls = 78°, coinciding with peak katabatic wind activity, reach maximum difference from non-anomalous sites at Ls = 110°, and gradually dissipate by Ls = 140°. During late summer, after Ls = 140°, we observe three significant darkening events, approximately 10° of Ls dates apart, during which CABAs transition into WADAs, with albedo reductions of up to 38 % and intense regional dust activity. WADAs align spatially with bright halos (circumferential remnants of CABAs) surrounding elevated terrain (10–120 m). With mesoscale modeling, we find that WADAs form when transient eddies are prominent across the region, suggesting that these transient eddies strip away the CABA bright fine-grained surface ice, exposing darker larger-grained subsurface layers. The repeatable seasonal events begin in late spring, when the CABA sites experience weaker katabatic winds than nearby regions. This reduces wind shear and thus ice loss, allowing them to retain their brightness and cooler temperatures and act as cold traps. Late, during early summer, cold trapping further enhances these anomalies by condensing fresh ice, slowing the warming process. This dynamic interplay between atmospheric conditions, ice deposition and loss, and topography signifies the complexity of Martian polar climates and their evolution.
{"title":"Formation and evolution of cold and bright anomalies and warm and dark anomalies on the north polar layered deposits","authors":"Pruthviraj J. Acharya , Isaac B. Smith , Aymeric Spiga","doi":"10.1016/j.icarus.2025.116903","DOIUrl":"10.1016/j.icarus.2025.116903","url":null,"abstract":"<div><div>The Cold and Bright Anomalies (CABAs) and Warm and Dark Anomalies (WADAs) on the North Polar Layered Deposit (NPLD) are distinct seasonal phenomena on Mars. CABAs, which are colder and brighter during early summer, and WADAs, which are warmer and darker in late summer, were analyzed across Mars Years (MYs) 29–35, focusing on solar longitudes (L<sub>s</sub>) between 30° and 170°. Investigating temperature, albedo, wind patterns, and topography at multiple sites, we found that CABAs emerge around L<sub>s</sub> = 78°, coinciding with peak katabatic wind activity, reach maximum difference from non-anomalous sites at L<sub>s</sub> = 110°, and gradually dissipate by L<sub>s</sub> = 140°. During late summer, after L<sub>s</sub> = 140°, we observe three significant darkening events, approximately 10° of L<sub>s</sub> dates apart, during which CABAs transition into WADAs, with albedo reductions of up to 38 % and intense regional dust activity. WADAs align spatially with bright halos (circumferential remnants of CABAs) surrounding elevated terrain (10–120 m). With mesoscale modeling, we find that WADAs form when transient eddies are prominent across the region, suggesting that these transient eddies strip away the CABA bright fine-grained surface ice, exposing darker larger-grained subsurface layers. The repeatable seasonal events begin in late spring, when the CABA sites experience weaker katabatic winds than nearby regions. This reduces wind shear and thus ice loss, allowing them to retain their brightness and cooler temperatures and act as cold traps. Late, during early summer, cold trapping further enhances these anomalies by condensing fresh ice, slowing the warming process. This dynamic interplay between atmospheric conditions, ice deposition and loss, and topography signifies the complexity of Martian polar climates and their evolution.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"447 ","pages":"Article 116903"},"PeriodicalIF":3.0,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145797656","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}
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