编译 | 李言

Nature, 10 August 2023, Volume 620 Issue 7973

《自然》2023年8月10日，第620卷，7973期

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天文学Astronomy

Sustained wet–dry cycling on early Mars

火星早期持续的干湿循环

▲ 作者：W. Rapin, G. Dromart, B. C. Clark et al.

▲ 链接：

https://www.nature.com/articles/s41586-023-06220-3

▲ 摘要：

在此，我们报告好奇号火星车在盖尔陨石坑的观测结果，表明在早期火星表面环境中发生了高频率的干湿循环。我们观察到在Y形连接处连接挖掘出的具有硫酸盐富集的厘米级多边形山脊，记录了由于规则强度的反复干湿循环而在新鲜泥浆中形成的裂缝。

我们的发现不是由撞击或火山引起的偶尔水文活动，而是指向了火星早期持续的、周期性的，甚至可能是季节性的气候。此外，由于干湿循环可以促进前生物聚合，盖尔蒸发盆地可能特别有利于这些过程。

我们观察到的多角形模型在物理和时间上与蒙脱石粘土向含硫酸盐地层的转变有关，这是一个全球分布的矿物过渡。这表明Noachian–Hesperian过渡时期（38 - 36亿年前）可能具备了类似地球的气候制度和有利于前生物进化的地表环境。

▲ Abstract：

Here we report observations by the Curiosity rover at Gale Crater indicating that high-frequency wet–dry cycling occurred in early Martian surface environments. We observe exhumed centimetric polygonal ridges with sulfate enrichments, joined at Y-junctions, that record cracks formed in fresh mud owing to repeated wet–dry cycles of regular intensity. Instead of sporadic hydrological activity induced by impacts or volcanoes, our findings point to a sustained, cyclic, possibly seasonal, climate on early Mars. Furthermore, as wet–dry cycling can promote prebiotic polymerization, the Gale evaporitic basin may have been particularly conducive to these processes. The observed polygonal patterns are physically and temporally associated with the transition from smectite clays to sulfate-bearing strata, a globally distributed mineral transition. This indicates that the Noachian–Hesperian transition (3.8-3.6 billion years ago) may have sustained an Earth-like climate regime and surface environments favourable to prebiotic evolution.

Martian dunes indicative of wind regime shift in line with end of ice age

火星沙丘表明，风向随着冰河时代的结束发生改变

▲ 作者：Jianjun Liu, Xiaoguang Qin et al.

▲ 链接：

https://www.nature.com/articles/s41586-023-06206-1

▲ 摘要：

在这里，我们展示了祝融号探测器在穿越火星乌托邦平原南部LDM区域时获得的一组测量结果。我们发现了一个地层序列的证据，包括最初的barchan沙丘形成，表明东北风及沙丘沉积物胶结，之后受到西北风的侵蚀，侵蚀barchan沙丘并产生独特的纵向沙丘，风向转变与冰河时代的结束相一致。

这些结果与火星极地地层记录相一致，将有助于提高我们对火星古代气候历史的理解。

▲ Abstract：

Here we present a suite of measurements obtained by the Zhurong rover during its traverse across the southern LDM region in Utopia Planitia, Mars. We find evidence for a stratigraphic sequence involving initial barchan dune formation, indicative of north-easterly winds, cementation of dune sediments, followed by their erosion by north-westerly winds, eroding the barchan dunes and producing distinctive longitudinal dunes, with the transition in wind regime consistent with the end of the ice age. The results are compatible with the Martian polar stratigraphic record and will help improve our understanding of the ancient climate history of Mars.

物理学Physics

Solid-body trajectoids shaped to roll along desired pathways

固体轨迹体被塑造成沿着期望路径滚动的形状

▲ 作者：Yaroslav I. Sobolev, Ruoyu Don et al.

▲ 链接：

https://www.nature.com/articles/s41586-023-06306-y

▲ 摘要：

在此，我们开发了一种算法来设计“轨迹体”，然后通过3D打印计算出的形状并跟踪它们的滚动路径来验证这些设计，包括那些靠近自己的物体，这样物体的质量中心就会间歇性地向上移动。

我们的研究主要是出于好奇心，但是大多数路径的轨迹线的存在对量子和经典光学具有意想不到的影响，因为量子比特、自旋和光偏振的动力学可以精确地映射到轨迹线及其路径。

▲ Abstract：

Here, we develop an algorithm to design such bodies—which we call ‘trajectoids’—and then validate these designs experimentally by three-dimensionally printing the computed shapes and tracking their rolling paths, including those that close onto themselves such that the body’s centre of mass moves intermittently uphill. Our study is motivated largely by fundamental curiosity, but the existence of trajectoids for most paths has unexpected implications for quantum and classical optics, as the dynamics of qubits, spins and light polarization can be exactly mapped to trajectoids and their paths.

材料科学Material science

Oriented nucleation in formamidinium perovskite for

photovoltaics

光伏用甲脒钙钛矿的定向成核

▲ 作者：Pengju Shi, Yong Ding, Bin Ding et al.

▲ 链接：

https://www.nature.com/articles/s41586-023-06208-z

▲ 摘要：

在此，我们通过对钙钛矿结晶过程的原位监测来报告一种定向成核机制，该机制可以帮助避免不良相的存在，并提高光伏器件在不同薄膜加工场景下的性能。该器件的功率转换效率为25.4%（经认证为25.0%），该模块的面积为27.83 cm2，经认证的孔径效率为21.4%，令人印象深刻。

▲ Abstract：

Here we use in situ monitoring of the perovskite crystallization process to report an oriented nucleation mechanism that can help to avoid the presence of undesirable phases and improve the performance of photovoltaic devices in different film-processing scenarios. The resulting device has a demonstrated power-conversion efficiency of 25.4% (certified 25.0%) and the module, which has an area of 27.83 cm2, has achieved an impressive certified aperture efficiency of 21.4%.

地球科学Earth Science

Rift-induced disruption of cratonic keels drives kimberlite volcanism

裂谷引起的克拉通龙骨断裂驱动金伯利岩火山作用

▲ 作者：Thomas M. Gernon, Stephen M. Jones et al.

▲ 链接：

https://www.nature.com/articles/s41586-023-06193-3

▲ 摘要：

在此，我们展示了大多数跨越过去 10 亿年的金伯利岩，在大陆分裂后大约 3000 万年（Myr）喷发，表明与裂谷过程有关。我们的动力学和分析模型表明，在裂谷过程中形成的物理上陡峭的岩石圈—软流圈边界（LABs）在软流圈中产生对流不稳定性，这些对流不稳定性缓慢地向裂谷带内部迁移数百至数千公里。

这些不稳定性在大陆分裂后持续了数千万年，并破坏了几十公里厚的克拉通岩石圈（或称龙骨)）基底的稳定。移位的龙骨被回流中热的、上涌的软流圈和富含挥发物的龙骨的混合物所取代，导致减压部分融化。我们的计算表明，这一过程可以产生小体积、低度、富含挥发物的熔体，与金伯利岩的预期特征非常接近。

总而言之，这些结果通过克拉通龙骨的渐进破坏，提供了金伯利岩喷发和超大陆旋回之间的定量和机械联系。

▲ Abstract：

Here we show that most kimberlites spanning the past billion years erupted about 30 million years (Myr) after continental breakup, suggesting an association with rifting processes. Our dynamical and analytical models show that physically steep lithosphere–asthenosphere boundaries (LABs) formed during rifting generate convective instabilities in the asthenosphere that slowly migrate many hundreds to thousands of kilometres inboard of rift zones. These instabilities endure many tens of millions of years after continental breakup and destabilize the basal tens of kilometres of the cratonic lithosphere, or keel. Displaced keel is replaced by a hot, upwelling mixture of asthenosphere and recycled volatile-rich keel in the return flow, causing decompressional partial melting. Our calculations show that this process can generate small-volume, low-degree, volatile-rich melts, closely matching the characteristics expected of kimberlites. Together, these results provide a quantitative and mechanistic link between kimberlite episodicity and supercontinent cycles through progressive disruption of cratonic keels.

A cool runaway greenhouse without surface magma ocean

没有地表岩浆海洋的凉爽失控温室模型

▲ 作者：Franck Selsis, Jérémy Leconte et al.

▲ 链接：

https://www.nature.com/articles/s41586-023-06258-3

▲ 摘要：

在此，我们报告使用由辐射层形成纯蒸汽大气的气候模型，使其热结构强烈依赖于恒星光谱和内部热流。当不施加绝热剖面时，表面温度较低；地壳的融化需要比现在高几倍的日照，而这在太阳主序期是不会发生的。

与之前的研究结果相反，金星表面可以在大气逃逸之前凝固。在最红的恒星（Teff < 3000 K）周围，无论含水量如何，表面岩浆海洋都不能仅靠恒星的力量形成。这一发现影响了蒸汽大气和系外行星质量半径关系的可观测特征，极大改变了目前对TRAPPIST-1行星含水量猜测的限制因素。

对高压不透明的新测量，特别是远离H2O吸收带的测量，蒸汽大气是类地行星演化的重要阶段，对于完善蒸汽大气的模型是有必要的。

▲ Abstract：

Here, we report using a consistent climate model that pure steam atmospheres are commonly shaped by radiative layers, making their thermal structure strongly dependent on the stellar spectrum and internal heat flow. The surface is cooler when an adiabatic profile is not imposed; melting Earth’s crust requires an insolation several times higher than today, which will not happen during the main sequence of the Sun. Venus’s surface can solidify before the steam atmosphere escapes, which is the opposite of previous works. Around the reddest stars (Teff < 3,000 K), surface magma oceans cannot form by stellar forcing alone, whatever the water content. These findings affect observable signatures of steam atmospheres and exoplanet mass–radius relationships, drastically changing current constraints on the water content of TRAPPIST-1 planets. Unlike adiabatic structures, radiative–convective profiles are sensitive to opacities. New measurements of poorly constrained high-pressure opacities, in particular far from the H2O absorption bands, are thus necessary to refine models of steam atmospheres, which are important stages in terrestrial planet evolution.