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Hypothesis of an ancient northern ocean on Mars and insights from the Zhurong rover 火星北部古代海洋的假设和 "祝融 "号探测器的启示
IF 12.9 1区 物理与天体物理 Q1 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-08-27 DOI: 10.1038/s41550-024-02343-3
Le Wang, Jun Huang
Various landforms suggest the past presence of liquid water on the surface of Mars. The putative coastal landforms, outflow channels and the hemisphere-wide Vastitas Borealis Formation sediments indicate that the northern lowlands may have housed an ancient ocean. Challenges to this hypothesis are from topography analysis, mineral formation environment and climate modelling. Determining whether there was a northern ocean on Mars is crucial for understanding its climate history, geological processes and potential for ancient life, and for guiding future explorations. Recently, China’s Zhurong rover has identified marine sedimentary structures and multiple subsurface sedimentary layers. The unique in situ perspective of the Zhurong rover, along with previous orbital observations, provides strong support for an episodic northern ocean during the early Hesperian and early Amazonian (about 3.6–2.5 billion years ago). The ground truth from future sample-return missions, such as China’s Tianwen-3 or the Mars sample-return programmes by NASA, ESA and other agencies, will be required for a more unambiguous confirmation. This Perspective presents the evidence in favour of and against the existence of an ancient ocean covering the Martian northern plains (Vastitas Borealis), discussing in particular the contribution of the Chinese Zhurong rover observations in supporting the presence of an ocean and the key role of the upcoming sample return.
各种地貌表明火星表面曾经存在液态水。推测的海岸地貌、外流通道和覆盖整个半球的 Vastitas Borealis Formation 沉积物表明,北部低地可能曾有一个古老的海洋。对这一假设的质疑来自地形分析、矿物形成环境和气候建模。确定火星北部是否存在海洋对于了解火星的气候历史、地质过程和远古生命的潜力以及指导未来的探索至关重要。最近,中国的 "祝融 "号探测器确定了海洋沉积结构和多个地下沉积层。祝融号探测器独特的原位视角,加上之前的轨道观测,为早期黑斯伯纪和早期亚马逊纪(距今约36-25亿年)北方海洋的形成提供了强有力的支持。未来的取样返回任务,如中国的天文三号或美国宇航局、欧空局和其他机构的火星取样返回计划,将需要地面实况来进行更明确的确认。
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引用次数: 0
Scenarios of future annual carbon footprints of astronomical research infrastructures 天文研究基础设施未来每年碳足迹的设想方案
IF 12.9 1区 物理与天体物理 Q1 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-08-26 DOI: 10.1038/s41550-024-02346-0
Jürgen Knödlseder, Mickael Coriat, Philippe Garnier, Annie Hughes
Research infrastructures have been identified as an important source of greenhouse gas emissions of astronomical research. Based on a comprehensive inventory of 1,211 ground-based observatories and space missions, we assessed the evolution of the number of astronomical facilities and their carbon footprint from 1945 to 2022. We found that space missions dominate greenhouse gas emissions in astronomy, showing an important peak at the end of the 1960s, followed by a decrease that has turned again into a rise over the last decade. Extrapolating past trends, we predict that greenhouse gas emissions from astronomical facilities will experience no strong decline in the future, and may even rise substantially, unless research practices are changed. We demonstrate that a continuing growth in the number of operating astronomical facilities is not environmentally sustainable. These findings should motivate the astronomical community to reflect about the necessary evolutions that would put astronomical research on a sustainable path. A comprehensive inventory of the carbon footprints of 1,211 ground-based astronomical observatories and space missions over a period of 78 years is used to model the expected future annual carbon footprint from astronomical research infrastructures.
研究基础设施被认为是天文研究温室气体排放的一个重要来源。基于对 1,211 个地面观测站和太空任务的全面盘点,我们评估了 1945 年至 2022 年期间天文设施数量及其碳足迹的演变情况。我们发现,太空任务在天文学的温室气体排放中占主导地位,在 20 世纪 60 年代末达到一个重要的峰值,随后有所下降,而在过去十年中又转为上升。根据过去的趋势推断,我们预测,除非改变研究方法,否则天文设施的温室气体排放量在未来不会出现大幅下降,甚至可能大幅上升。我们证明,运行中的天文设施数量的持续增长在环境上是不可持续的。这些发现应促使天文学界思考必要的变革,使天文学研究走上可持续发展的道路。
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引用次数: 0
Cosmological constraints from non-Gaussian and nonlinear galaxy clustering using the SimBIG inference framework 利用 SimBIG 推理框架从非高斯和非线性星系聚类得出的宇宙学约束条件
IF 12.9 1区 物理与天体物理 Q1 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-08-21 DOI: 10.1038/s41550-024-02344-2
ChangHoon Hahn, Pablo Lemos, Liam Parker, Bruno Régaldo-Saint Blancard, Michael Eickenberg, Shirley Ho, Jiamin Hou, Elena Massara, Chirag Modi, Azadeh Moradinezhad Dizgah, David Spergel
The standard ΛCDM cosmological model predicts the presence of cold dark matter, with the current accelerated expansion of the Universe driven by dark energy. This model has recently come under scrutiny because of tensions in measurements of the expansion and growth histories of the Universe, parameterized using H0 and S8. The three-dimensional clustering of galaxies encodes key cosmological information that addresses these tensions. Here we present a set of cosmological constraints using simulation-based inference that exploits additional non-Gaussian information on nonlinear scales from galaxy clustering, inaccessible with current analyses. We analyse a subset of the Baryon Oscillation Spectroscopic Survey (BOSS) galaxy survey using SimBIG, a new framework for cosmological inference that leverages high-fidelity simulations and deep generative models. We use two clustering statistics beyond the standard power spectrum: the bispectrum and a summary of the galaxy field based on a convolutional neural network. We constrain H0 and S8 1.5 and 1.9 times more tightly than power spectrum analyses. With this increased precision, our constraints are competitive with those of other cosmological probes, even with only 10% of the full BOSS volume. Future work extending SimBIG to upcoming spectroscopic galaxy surveys (DESI, PFS, Euclid) will produce improved cosmological constraints that will develop understanding of cosmic tensions. By extracting non-Gaussian cosmological information on galaxy clustering at nonlinear scales, a framework for cosmic inference (SimBIG) provides more precise constraints for testing cosmological models.
标准ΛCDM 宇宙学模型预言存在冷暗物质,当前宇宙的加速膨胀是由暗能量驱动的。由于宇宙膨胀和增长历史的测量结果存在矛盾,这一模型最近受到了审查,其参数为 H0 和 S8。星系的三维聚类包含了解决这些矛盾的关键宇宙学信息。在这里,我们利用基于模拟的推理,提出了一套宇宙学约束条件,利用了星系团聚非线性尺度上的额外非高斯信息,而这些信息是目前的分析无法获得的。我们利用 SimBIG 分析了重子振荡光谱巡天(BOSS)星系巡天的一个子集,SimBIG 是一个利用高保真模拟和深度生成模型进行宇宙学推断的新框架。我们使用了标准功率谱之外的两种聚类统计:双谱和基于卷积神经网络的星系场摘要。我们对 H0 和 S8 的约束比功率谱分析严格 1.5 倍和 1.9 倍。随着精度的提高,我们的约束与其他宇宙学探测器的约束相比是有竞争力的,即使只有 BOSS 全部体积的 10%。未来的工作将把 SimBIG 扩展到即将开展的光谱星系巡天(DESI、PFS、Euclid),这将产生更好的宇宙学约束,从而加深对宇宙张力的理解。
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引用次数: 0
The formation of the TRAPPIST-1 system in two steps during the recession of the disk inner edge TRAPPIST-1系统在星盘内缘后退过程中分两步形成
IF 12.9 1区 物理与天体物理 Q1 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-08-20 DOI: 10.1038/s41550-024-02342-4
Gabriele Pichierri, Alessandro Morbidelli, Konstantin Batygin, Ramon Brasser
TRAPPIST-1 hosts seven planets. The period ratios of neighbouring pairs are close to the 8:5, 5:3, 3:2, 3:2, 4:3 and 3:2 ratios in increasing distance from the star. The Laplace angles associated with neighbouring triplets are observed to be librating, proving the resonant nature of the system. This compact, resonant configuration is a manifest sign of disk-driven migration; however, the preferred outcome of such evolution is the establishment of first-order resonances, not the high-order resonances observed in the inner system. Here, we explain the observed orbital configuration with a model that is largely independent of the specific disk migration and orbital circularization efficiencies. Together with migration, the two key elements of our model are that the inner border of the protoplanetary disk receded with time and that the system was initially separated into two subsystems. Specifically, the inner b, c, d and e planets were initially placed in a 3:2 resonance chain and then evolved to the 8:5–5:3 commensurability between planets b, c and d due to the recession of the inner edge of the disk, whereas the outer planets migrated to the inner edge at a later time and established the remaining resonances. Our results pivot on the dynamical role of the presently unobservable recession of the inner edge of protoplanetary disks. They also reveal the role of recurring phases of convergent migration followed by resonant repulsion with associated orbital circularization when resonant chains interact with migration barriers. The dynamical history of the seven-planet TRAPPIST-1 system, which is marked by delicate orbital resonances, is meticulously reconstructed. This study unveils the key physical processes that shaped its formation during and beyond the circumstellar disk phase.
TRAPPIST-1 有七颗行星。相邻行星对的周期比接近于 8:5、5:3、3:2、3:2、4:3 和 3:2,随着与恒星距离的增加而增加。据观测,与相邻三胞胎相关的拉普拉斯角是平移的,这证明了该系统的共振性质。这种紧凑的共振构造是磁盘驱动迁移的明显标志;然而,这种演化的首选结果是建立一阶共振,而不是在内部系统中观测到的高阶共振。在这里,我们用一个与具体的磁盘迁移和轨道圆化效率基本无关的模型来解释观测到的轨道构型。除了迁移之外,我们的模型还有两个关键要素,一是原行星盘的内部边界随着时间的推移而后退,二是该系统最初被分离成两个子系统。具体来说,内侧的b、c、d和e行星最初处于3:2共振链中,后来由于盘内侧边缘的后退,b、c和d行星之间的共振演化为8:5-5:3共振,而外侧行星则在后来迁移到盘内侧边缘,并建立了剩余的共振。我们的研究结果集中体现了目前无法观测到的原行星盘内缘后退的动力学作用。这些结果还揭示了当共振链与迁移障碍相互作用时,先是会聚迁移,然后是共振排斥以及相关的轨道环化等反复出现的阶段的作用。
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引用次数: 0
Seeing disks in context 从背景中看磁盘
IF 12.9 1区 物理与天体物理 Q1 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-08-20 DOI: 10.1038/s41550-024-02355-z
Paul Woods
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引用次数: 0
High hopes for high energy 对高能量寄予厚望
IF 12.9 1区 物理与天体物理 Q1 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-08-20 DOI: 10.1038/s41550-024-02356-y
While the early 2020s are seeing a resurgence in new space-based X-ray missions — including the NASA-led Imaging X-ray Polarimetry Explorer — a stalwart of the field, Chandra, faces an uncertain future.
虽然在 2020 年代初,新的天基 X 射线任务(包括美国国家航空航天局领导的成像 X 射线极化探测器)正在重新崛起,但该领域的中坚力量钱德拉却面临着不确定的未来。
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引用次数: 0
The interior as the dominant water reservoir in super-Earths and sub-Neptunes 内部是超地球和次海王星的主要储水层
IF 12.9 1区 物理与天体物理 Q1 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-08-20 DOI: 10.1038/s41550-024-02347-z
Haiyang Luo, Caroline Dorn, Jie Deng
Water is an important component of exoplanets, with its distribution, that is, whether at the surface or deep inside, fundamentally influencing the planetary properties. The distribution of water in most exoplanets is determined by yet-unknown partition coefficients at extreme conditions. Here we first conduct ab initio molecular dynamics simulations to investigate the metal–silicate partition coefficients of water up to 1,000 GPa and then model planet interiors by considering the effects of water content on density, melting temperature and water partitioning. Our calculations reveal that water strongly partitions into iron over silicate at high pressures and, thus, would preferentially stay in a planet’s core. The results of our planet interior model challenge the notion of water worlds as imagined before: the majority of the bulk water budget (even more than 95%) can be stored deep within the core and the mantle, and not at the surface. For planets more massive than ~6 M⨁ and Earth-size planets (of lower mass and small water budgets), the majority of water resides deep in the cores of planets. Whether water is assumed to be at the surface or at depth can affect the radius up to 15–25% for a given mass. The exoplanets previously believed to be water-poor on the basis of mass–radius data may actually be rich in water. If water exists in super-Earth and sub-Neptune exoplanets, it is expected to be hidden deep in their cores and mantles, rather than at their surfaces. Exoplanets considered to be relatively dry might actually have abundant water sequestered in their interiors.
水是系外行星的重要组成部分,它的分布,即是在表面还是在内部深处,从根本上影响着行星的性质。水在大多数系外行星中的分布是由极端条件下未知的分配系数决定的。在这里,我们首先进行了ab initio分子动力学模拟,研究了水在1000 GPa以下的金属-硅酸盐分配系数,然后通过考虑水含量对密度、熔融温度和水分配的影响,建立了行星内部模型。我们的计算结果表明,在高压下,水与铁的分区强于与硅酸盐的分区,因此,水会优先留在行星的内核中。我们的行星内部模型的结果对以前想象的水世界的概念提出了挑战:大部分(甚至超过 95%)体积水预算可以储存在地核和地幔深处,而不是表面。对于质量大于~6 M⨁的行星和地球大小的行星(质量较低,水预算较小)来说,大部分水存在于行星内核深处。对于给定质量的行星来说,假设水在表面还是在深处会影响半径达15-25%。以前根据质量-半径数据认为贫水的系外行星实际上可能富含水。
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引用次数: 0
Machine learning reveals the merging history of nearby galaxies 机器学习揭示附近星系的合并历史
IF 12.9 1区 物理与天体物理 Q1 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-08-16 DOI: 10.1038/s41550-024-02335-3
A probabilistic machine learning method trained on cosmological simulations is used to determine whether stars in 10,000 nearby galaxies formed internally or were accreted from other galaxies during merging events. The model predicts that only 20% of the stellar mass in present day galaxies is the result of past mergers.
利用在宇宙学模拟基础上训练的概率机器学习方法来确定附近一万个星系中的恒星是在内部形成的,还是在合并过程中从其他星系吸积而来的。该模型预测,当今星系中只有 20% 的恒星质量是过去星系合并的结果。
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引用次数: 0
An early giant planet instability recorded in asteroidal meteorites 小行星陨石中记录的早期巨行星不稳定性
IF 12.9 1区 物理与天体物理 Q1 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-08-15 DOI: 10.1038/s41550-024-02340-6
Graham Harper Edwards, C. Brenhin Keller, Elisabeth R. Newton, Cameron W. Stewart
Giant planet migration appears widespread among planetary systems in our Galaxy. However, the timescales of this process, which reflect the underlying dynamical mechanisms, are not well constrained, even within the Solar System. As planetary migration scatters smaller bodies onto intersecting orbits, it would have resulted in an epoch of enhanced bombardment in the Solar System’s asteroid belt. Here, to accurately and precisely quantify the timescales of migration, we interrogate thermochronologic data from asteroidal meteorites, which record the thermal imprint of energetic collisions. We present a database of 40K–40Ar system ages from chondrite meteorites and evaluate it with an asteroid-scale thermal code coupled to a Markov chain Monte Carlo inversion. Simulations require bombardment to reproduce the observed age distribution and identify a bombardment event beginning $$11.{3}_{-6.6}^{+9.5}, {mathrm{Myr}}$$ after the Sun formed (50% credible interval). Our results associate a giant planet instability in our Solar System with the dissipation of the gaseous protoplanetary disk. Radiometric cooling ages of chondrite meteorites record asteroid belt bombardment beginning approximately 11 million years after the formation of the Solar System, indicating an episode of giant planet migration at that time.
在我们银河系的行星系统中,巨行星迁移似乎很普遍。然而,即使在太阳系内,这一过程的时间尺度也没有得到很好的制约,而这一尺度反映了基本的动力学机制。由于行星迁移会将较小的天体分散到相交的轨道上,这将导致太阳系小行星带出现一个轰击增强的时代。在这里,为了准确和精确地量化迁移的时间尺度,我们询问了小行星陨石的热年代学数据,这些数据记录了高能碰撞的热印记。我们提供了一个来自软玉陨石的 40K-40Ar 系统年龄数据库,并通过小行星尺度热代码和马尔科夫链蒙特卡罗反演对其进行了评估。模拟需要轰击来重现观测到的年龄分布,并确定了一个轰击事件开始于太阳形成之后(50%可信区间)(11.3}_{-6.6}^{+9.5}, {mathrm{Myr}} )。我们的结果将太阳系的巨行星不稳定性与气态原行星盘的消散联系起来。
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引用次数: 0
Giant planets migrated shortly after the Solar System’s protoplanetary disk dispersed 巨行星在太阳系原行星盘散开后不久就迁移了
IF 12.9 1区 物理与天体物理 Q1 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-08-15 DOI: 10.1038/s41550-024-02341-5
Early in the history of the Solar System, the giant planets — including Jupiter and Saturn — migrated under gravity into different orbits around the Sun, causing an epoch of chaos and collisions. Radioactive isotopes in asteroids record the thermal imprint of these collisions, and a broad survey of meteorites now constrains the timing of the migration to approximately 11 million years after the Solar System formed.
在太阳系历史的早期,包括木星和土星在内的巨行星在重力作用下迁移到围绕太阳的不同轨道上,造成了一个混乱和碰撞的时代。小行星中的放射性同位素记录了这些碰撞的热印记,现在对陨石的广泛调查将迁移的时间限制在太阳系形成后大约1100万年。
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引用次数: 0
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