編譯 | 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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天文學Astronomy

Sustained wet–dry cycling on early Mars

火星早期持續的干濕循環

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

▲ 鏈接：

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

▲ 摘要：

在此，我們報告好奇號火星車在蓋爾隕石坑的觀測結果，表明在早期火星表面環境中發生了高頻率的干濕循環。我們觀察到在Y形連接處連接挖掘出的具有硫酸鹽富集的厘米級多邊形山脊，記錄了由于規則強度的反復干濕循環而在新鮮泥漿中形成的裂縫。

我們的發現不是由撞擊或火山引起的偶爾水文活動，而是指向了火星早期持續的、周期性的，甚至可能是季節性的氣候。此外，由于干濕循環可以促進前生物聚合，蓋爾蒸發盆地可能特別有利于這些過程。

我們觀察到的多角形模型在物理和時間上與蒙脫石粘土向含硫酸鹽地層的轉變有關，這是一個全球分布的礦物過渡。這表明Noachian–Hesperian過渡時期（38 - 36億年前）可能具備了類似地球的氣候制度和有利于前生物進化的地表環境。

▲ 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，風向隨著冰河時代的結束發生改變

▲ 作者：Jianjun Liu, Xiaoguang Qin et al.

▲ 鏈接：

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

▲ 摘要：

在這里，我們展示了祝融號探測器在穿越火星烏托邦平原南部LDM區域時獲得的一組測量結果。我們發現了一個地層序列的證據，包括最初的barchan沙丘形成，表明東北風及沙丘沉積物膠結，之后受到西北風的侵蝕，侵蝕barchan沙丘并產生獨特的縱向沙丘，風向轉變與冰河時代的結束相一致。

這些結果與火星極地地層記錄相一致，將有助于提高我們對火星古代氣候歷史的理解。

▲ 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.

物理學Physics

Solid-body trajectoids shaped to roll along desired pathways

固體軌跡體被塑造成沿著期望路徑滾動的形狀

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

▲ 鏈接：

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

▲ 摘要：

在此，我們開發了一種算法來設計“軌跡體”，然后通過3D打印計算出的形狀并跟蹤它們的滾動路徑來驗證這些設計，包括那些靠近自己的物體，這樣物體的質量中心就會間歇性地向上移動。

我們的研究主要是出于好奇心，但是大多數路徑的軌跡線的存在對量子和經典光學具有意想不到的影響，因為量子比特、自旋和光偏振的動力學可以精確地映射到軌跡線及其路徑。

▲ 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.

材料科學Material science

Oriented nucleation in formamidinium perovskite for

photovoltaics

光伏用甲脒鈣鈦礦的定向成核

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

▲ 鏈接：

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

▲ 摘要：

在此，我們通過對鈣鈦礦結晶過程的原位監測來報告一種定向成核機制，該機制可以幫助避免不良相的存在，并提高光伏器件在不同薄膜加工場景下的性能。該器件的功率轉換效率為25.4%（經認證為25.0%），該模塊的面積為27.83 cm2，經認證的孔徑效率為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%.

地球科學Earth Science

Rift-induced disruption of cratonic keels drives kimberlite volcanism

裂谷引起的克拉通龍骨斷裂驅動金伯利巖火山作用

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

▲ 鏈接：

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

▲ 摘要：

在此，我們展示了大多數跨越過去 10 億年的金伯利巖，在大陸分裂后大約 3000 萬年（Myr）噴發，表明與裂谷過程有關。我們的動力學和分析模型表明，在裂谷過程中形成的物理上陡峭的巖石圈—軟流圈邊界（LABs）在軟流圈中產生對流不穩定性，這些對流不穩定性緩慢地向裂谷帶內部遷移數百至數千公里。

這些不穩定性在大陸分裂后持續了數千萬年，并破壞了幾十公里厚的克拉通巖石圈（或稱龍骨)）基底的穩定。移位的龍骨被回流中熱的、上涌的軟流圈和富含揮發物的龍骨的混合物所取代，導致減壓部分融化。我們的計算表明，這一過程可以產生小體積、低度、富含揮發物的熔體，與金伯利巖的預期特征非常接近。

總而言之，這些結果通過克拉通龍骨的漸進破壞，提供了金伯利巖噴發和超大陸旋回之間的定量和機械聯系。

▲ 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

沒有地表巖漿海洋的涼爽失控溫室模型

▲ 作者：Franck Selsis, Jérémy Leconte et al.

▲ 鏈接：

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

▲ 摘要：

在此，我們報告使用由輻射層形成純蒸汽大氣的氣候模型，使其熱結構強烈依賴于恒星光譜和內部熱流。當不施加絕熱剖面時，表面溫度較低；地殼的融化需要比現在高幾倍的日照，而這在太陽主序期是不會發生的。

與之前的研究結果相反，金星表面可以在大氣逃逸之前凝固。在最紅的恒星（Teff < 3000 K）周圍，無論含水量如何，表面巖漿海洋都不能僅靠恒星的力量形成。這一發現影響了蒸汽大氣和系外行星質量半徑關系的可觀測特征，極大改變了目前對TRAPPIST-1行星含水量猜測的限制因素。

對高壓不透明的新測量，特別是遠離H2O吸收帶的測量，蒸汽大氣是類地行星演化的重要階段，對于完善蒸汽大氣的模型是有必要的。

▲ 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.