编译 | 李言

Science, 30 SEP 2022, VOL 377, ISSUE 6614

《科学》2022年9月30日，第377卷，6614期

材料科学Material Sciences

Promotion of superconductivity in magic-angle graphene multilayers

磁角石墨烯多层膜中超导性的提升

▲ 作者：YIRAN ZHANG, ROBERT POLSKI, CYPRIAN LEWANDOWSKI et al.

▲ 链接：

https://www.science.org/doi/10.1126/science.abn8585

▲ 摘要：

石墨烯摩尔超晶格显示出丰富的相关绝缘、拓扑和超导相。尽管强相关性和非平凡拓扑的起源可以直接与平坦带联系起来，但超导性的特质仍然是个谜团。

我们证明了，将扭曲三层、四层和五层石墨烯置于单层二烯化钨上的后产生的魔角装置表现出极化和超导性。我们还观察到三层和四层石墨烯在有限电位移场下产生了绝缘态。

随着层数的增加，超导性在一个增强的填充因子范围内出现，在五层石墨烯中，它扩展到每个摩尔的4个电子的填充。我们的结果突出了扁平带和更分散带之间的相互作用在石墨烯摩尔超晶格中延伸超导区域的角色。

▲ Abstract：

Graphene moiré superlattices show an abundance of correlated insulating, topological, and superconducting phases. Whereas the origins of strong correlations and nontrivial topology can be directly linked to flat bands, the nature of superconductivity remains enigmatic. We demonstrate that magic-angle devices made of twisted tri-, quadri-, and pentalayer graphene placed on monolayer tungsten diselenide exhibit flavor polarization and superconductivity. We also observe insulating states in the tril- and quadrilayer arising at finite electric displacement fields. As the number of layers increases, superconductivity emerges over an enhanced filling-factor range, and in the pentalayer it extends well beyond the filling of four electrons per moiré unit cell. Our results highlight the role of the interplay between flat and more dispersive bands in extending superconducting regions in graphene moiré superlattices.

化学Chemistry

Inefficient and unlit natural gas flares both emit large quantities of methane

低效和未点燃的天然气火炬都会释放大量的甲烷

▲ 作者：GENEVIEVE PLANT, ERIC A. KORT, ADAM R. BRANDT et al.

▲ 链接：

https://www.science.org/doi/10.1126/science.abq0385

▲ 摘要：

火炬被化石燃料工业广泛用于处理天然气。工业界和政府通常认为，火炬保持燃烧，同时以98%的效率消耗甲烷——天然气的主要成分。然而，这两种想法都不是基于现实世界的观察。我们通过对三个占美国燃烧的80%的盆地的空中采样计算燃烧效率，并将这些观测结果与未点燃的火炬覆盖率调查相结合。

我们发现，未点燃的火炬和低效燃烧对无效甲烷破坏的贡献都相当大，火炬只能有效破坏91.1%的甲烷。

这意味着甲烷排放量比目前的假设增加了5倍，占美国油气甲烷排放总量的4%至10%。这一发现强调了此前未被重视的甲烷来源和减排机会。

▲ Abstract：

Flaring is widely used by the fossil fuel industry to dispose of natural gas. Industry and governments generally assume that flares remain lit and destroy methane, the predominant component of natural gas, with 98% efficiency. Neither assumption, however, is based on real-world observations. We calculate flare efficiency using airborne sampling across three basins responsible for >80% of US flaring and combine these observations with unlit flare prevalence surveys. We find that both unlit flares and inefficient combustion contribute comparably to ineffective methane destruction, with flares effectively destroying only 91.1% (90.2, 91.8; 95% confidence interval) of methane. This represents a fivefold increase in methane emissions above present assumptions and constitutes 4 to 10% of total US oil and gas methane emissions, highlighting a previously underappreciated methane source and mitigation opportunity.

天文学Astronomy

Aqueously altered igneous rocks sampled on the floor of Jezero crater, Mars

火星杰泽罗陨石坑的水蚀火成岩样本

▲ 作者：K. A. FARLEY, K. M. STACK, D. L. SHUSTER et al.

▲ 链接：

https://www.science.org/doi/10.1126/science.abo2196

▲ 摘要：

“毅力”号火星车在火星杰泽罗陨石坑着陆，调查古代湖泊和河流沉积物。我们报告了对陨石坑底部的观察，在陨石坑的沉积层下面，发现底部由被水改变的火成岩组成。含量最少的成分，非正式命名为Séítah，是一种粗糙结晶的富含橄榄石的岩石，它积累在岩浆体的底部。

沿晶界的镁铁碳酸盐表明在缺水条件下与富含二氧化碳的水发生反应。Séítah之上是一种名为Máaz的成分，我们将其解释为熔岩流或层状火成岩体中Séítah的化学补充物。

这些岩石中的空洞含有硫酸盐和高氯酸盐，很可能是后来近地表卤水蒸发引入的。这些岩石的岩心样本已经被储存在“毅力号”上，以便有可能返回地球。

▲ Abstract：

The Perseverance rover landed in Jezero crater, Mars, to investigate ancient lake and river deposits. We report observations of the crater floor, below the crater’s sedimentary delta, finding that the floor consists of igneous rocks altered by water. The lowest exposed unit, informally named Séítah, is a coarsely crystalline olivine-rich rock, which accumulated at the base of a magma body. Magnesium-iron carbonates along grain boundaries indicate reactions with carbon dioxide–rich water under water-poor conditions. Overlying Séítah is a unit informally named Máaz, which we interpret as lava flows or the chemical complement to Séítah in a layered igneous body. Voids in these rocks contain sulfates and perchlorates, likely introduced by later near-surface brine evaporation. Core samples of these rocks have been stored aboard Perseverance for potential return to Earth.

An olivine cumulate outcrop on the floor of Jezero crater, Mars

火星杰泽罗陨石坑底部的橄榄石堆积露头

▲ 作者：Y. LIU, M. M. TICE, M. E. SCHMIDT et al.

▲ 链接：

https://www.science.org/doi/10.1126/science.abo2756

▲ 摘要：

火星杰泽罗陨石坑底部的地质单元是一个延伸到陨石坑外更广泛的、富含橄榄石的区域地层的一部分。我们研究了杰泽罗底部的Séítah复合物中橄榄石和碳酸盐的岩石学情况。利用“毅力”号获得的多光谱图像和x射线荧光数据，我们对该单元内的Bastide和Brac露头进行了岩石学分析。

我们发现这些露头是由被水流体适度改变的火成岩组成的。火成岩主要由粗粒橄榄石构成，类似于一些火星陨石。我们认为它们是由厚岩浆体经过多级冷却而沉淀和富集橄榄石形成的橄榄石堆积岩。

▲ Abstract：

The geological units on the floor of Jezero crater, Mars, are part of a wider regional stratigraphy of olivine-rich rocks, which extends well beyond the crater. We investigated the petrology of olivine and carbonate-bearing rocks of the Séítah formation in the floor of Jezero. Using multispectral images and x-ray fluorescence data, acquired by the Perseverance rover, we performed a petrographic analysis of the Bastide and Brac outcrops within this unit. We found that these outcrops are composed of igneous rock, moderately altered by aqueous fluid. The igneous rocks are mainly made of coarse-grained olivine, similar to some martian meteorites. We interpret them as an olivine cumulate, formed by settling and enrichment of olivine through multistage cooling of a thick magma body.

地球科学Earth Science

A detection of the sea level fingerprint of Greenland Ice Sheet melt

格陵兰冰盖融化的海平面指纹探测

▲ 作者：SOPHIE COULSON, S?NKE DANGENDORF, JERRY X. MITROVICA et al.

▲ 链接：

https://www.science.org/doi/10.1126/science.abo0926

▲ 摘要：

冰盖和冰川的快速融化对海平面产生了独特的地理学形态，或指纹。然而，由于在高纬度的观测较少，以及从信号中分离海洋动态变化的困难，对单个海平面指纹的检测一直具有挑战性。

我们利用雷达测高数据和附近冰川的模型重建估计的近期冰质量损失，预测了格陵兰冰盖（GrIS）融化的指纹，并将这一预测与一个独立的、基于测高得出的海面高度趋势进行了比较，该趋势修正了冰盖附近地区的海洋动态变化。

两个场之间的统计显著相关性（P < 0.001）提供了一个对我们的变暖世界中的近期GrIS融化的近场海平面指纹明确的观察性探测。

▲ Abstract：

Rapid melting of ice sheets and glaciers drives a unique geometry, or fingerprint, of sea level change. However, the detection of individual fingerprints has been challenging because of sparse observations at high latitudes and the difficulty of disentangling ocean dynamic variability from the signal. We predict the fingerprint of Greenland Ice Sheet (GrIS) melt using recent ice mass loss estimates from radar altimetry data and model reconstructions of nearby glaciers and compare this prediction to an independent, altimetry-derived sea surface height trend corrected for ocean dynamic variability in the region adjacent to the ice sheet. A statistically significant correlation between the two fields (P < 0.001) provides an unambiguous observational detection of the near-field sea level fingerprint of recent GrIS melting in our warming world.

Climate change drives rapid decadal acidification in the Arctic Ocean from 1994 to 2020

从1994年到2020年，气候变化推动了北冰洋的加速酸化

▲ 作者：DI QI, ZHANGXIAN OUYANG, LIQI CHEN et al.

▲ 链接：

https://www.science.org/doi/10.1126/science.abo0383

▲ 摘要：

近几十年来，北冰洋经历了快速变暖和海冰消失，成为第一个经历广泛文石欠饱和的公海盆地[文石饱和状态（Ωarag）< 1]。

然而，它的长期海洋酸化趋势和潜在机制仍然没有记录。在此，我们报告了北冰洋的快速酸化，其速率是其他海洋盆地的三到四倍，并将其归因于海冰覆盖在十年时间尺度上的变化。

海冰融化使海水暴露在大气中，促进了大气中二氧化碳的快速吸收，降低了其碱度和缓冲能力，从而导致pH值和文石饱和状态急剧下降。我们预测，未来pH值将进一步下降，特别是在海冰退缩严重的高纬度地区，而北极变暖可能抵消文石饱和状态的下降。

▲ Abstract：

The Arctic Ocean has experienced rapid warming and sea ice loss in recent decades, becoming the first open-ocean basin to experience widespread aragonite undersaturation [saturation state of aragonite (Ωarag) < 1]. However, its trend toward long-term ocean acidification and the underlying mechanisms remain undocumented. Here, we report rapid acidification there, with rates three to four times higher than in other ocean basins, and attribute it to changing sea ice coverage on a decadal time scale. Sea ice melt exposes seawater to the atmosphere and promotes rapid uptake of atmospheric carbon dioxide, lowering its alkalinity and buffer capacity and thus leading to sharp declines in pH and Ωarag. We predict a further decrease in pH, particularly at higher latitudes where sea ice retreat is active, whereas Arctic warming may counteract decreases in Ωarag in the future.