原文地址：http://news.sciencenet.cn/htmlnews/2023/7/505719.shtm
編譯 | 未玖
Nature, 27 July 2023, VOL 619, ISSUE 7971
《自然》2023年7月27日，第619卷，7971期
天文學Astronomy
Spectroscopic identification of water emission from a main-belt comet
主帶彗星水輻射的光譜識別
▲ 作者：Michael S. P. Kelley, Henry H. Hsieh, Dennis Bodewits, Mohammad Saki, Geronimo L. Villanueva, Stefanie N. Milam, et al.
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06152-y
▲ 摘要：
主帶彗星是位于小行星帶的小型太陽系天體，在其近日點通道中反復表現出類似彗星的活動（即塵埃彗發或彗尾），強烈表明冰升華。雖然主帶彗星的存在意味著小行星帶中有尚存的水冰，但盡管用世界上最大的望遠鏡進行了嚴密探測，在這些天體周圍仍未發現氣體。
研究組展示了詹姆斯·韋伯太空望遠鏡的觀測結果，它清楚地表明，主帶彗星238P/Read有一個水蒸氣彗發，但缺乏明顯的二氧化碳氣體彗發。該發現表明，Read彗星的活動是由水冰升華驅動的，這意味著主帶彗星與普通彗星群有著根本的不同。
無論Read彗星是否經歷了不同的形成環境或演化史，它都不太可能是最近才從外太陽系闖入小行星帶的。根據這些結果，主帶彗星似乎代表了一種揮發性物質樣本，且這種物質目前在經典彗星的觀測和隕石記錄中沒有代表性，這對于理解早期太陽系的揮發性物質及其隨后演變非常重要。
▲ Abstract：
Main-belt comets are small Solar System bodies located in the asteroid belt that repeatedly exhibit comet-like activity (that is, dust comae or tails) during their perihelion passages, strongly indicating ice sublimation. Although the existence of main-belt comets implies the presence of extant water ice in the asteroid belt, no gas has been detected around these objects despite intense scrutiny with the world’s largest telescopes. Here we present James Webb Space Telescope observations that clearly show that main-belt comet 238P/Read has a coma of water vapour, but lacks a significant CO2 gas coma. Our findings demonstrate that the activity of comet Read is driven by water–ice sublimation, and implies that main-belt comets are fundamentally different from the general cometary population. Whether or not comet Read experienced different formation circumstances or evolutionary history, it is unlikely to be a recent asteroid belt interloper from the outer Solar System. On the basis of these results, main-belt comets appear to represent a sample of volatile material that is currently unrepresented in observations of classical comets and the meteoritic record, making them important for understanding the early Solar System’s volatile inventory and its subsequent evolution.
物理學Physics
Femtosecond proton transfer in urea solutions probed by X-ray spectroscopy
X射線光譜學探測尿素溶液中的飛秒質子轉移
▲ 作者：Zhong Yin, Yi-Ping Chang, Tadas Bal?iūnas, Yashoj Shakya, Aleksa Djorovi?, Geoffrey Gaulier, et al.
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06182-6
▲ 摘要：
質子轉移是水相化學中最基本的事件之一，也是超快電子和結構動力學耦合的典型范例。在飛秒時間尺度上解耦電子和核動力學仍是一項艱巨挑戰，特別是在液相、生化過程的自然環境中。
研究組利用臺式水窗X射線吸收光譜的獨特特性來揭示水溶液中離子化尿素二聚體的飛秒質子轉移動力學。借助于從頭算量子力學和分子力學計算，利用X射線吸收光譜的元素特異性和位點選擇性，研究組展示了除質子轉移之外，尿素二聚體的后續重排和電子結構相關變化如何通過位點選擇性來識別。
這些結果表明，平板射流、臺式X射線吸收光譜在闡明生物分子系統中溶液相超快動力學方面具有相當大的潛力。
▲ Abstract：
Proton transfer is one of the most fundamental events in aqueous-phase chemistry and an emblematic case of coupled ultrafast electronic and structural dynamics. Disentangling electronic and nuclear dynamics on the femtosecond timescales remains a formidable challenge, especially in the liquid phase, the natural environment of biochemical processes. Here we exploit the unique features of table-top water-window X-ray absorption spectroscopy to reveal femtosecond proton-transfer dynamics in ionized urea dimers in aqueous solution. Harnessing the element specificity and the site selectivity of X-ray absorption spectroscopy with the aid of ab initio quantum-mechanical and molecular-mechanics calculations, we show how, in addition to the proton transfer, the subsequent rearrangement of the urea dimer and the associated change of the electronic structure can be identified with site selectivity. These results establish the considerable potential of flat-jet, table-top X-ray absorption spectroscopy in elucidating solution-phase ultrafast dynamics in biomolecular systems.
能源科學Energy Science
Accelerating the energy transition towards photovoltaic and wind in China
加速中國向光伏和風能的能源轉型
▲ 作者：Yijing Wang, Rong Wang, Katsumasa Tanaka, Philippe Ciais, Josep Penuelas, Yves Balkanski, et al.
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06180-8
▲ 摘要：
中國到2060年實現碳中和目標要求將光伏（PV）和風能的發電量從1 PWh/年增加至10~15 PWh/年。然而，根據可再生能源設備安裝的歷史速率，即最近的高分辨率能源系統模型和基于中國“十四五”能源發展（CFED）的預測，到2060年，發電量僅能達到5~9.5 PWh/年。
研究組表明，通過單獨優化部署3844個新公用事業規模的PV和風電場，與超高壓（UHV）輸電和儲能相協調，并考慮到電力負荷的靈活性和學習動態，PV和風電的發電量可以從9 PWh/年（對應CFED路徑）增至15 PWh/年，伴隨著平均減排成本從每噸二氧化碳（tCO2）97美元降至6美元。
為了實現這一目標，PV和風能的年化投資應從2020年的770億美元（當前水平）增至21世紀20年代的1270億美元，并在21世紀50年代進一步增至4260億美元/年。PV和風能的大規模部署可實現共同獲益，以增加最貧窮地區居民的收入。
該研究結果突出了通過建設儲能、擴大輸電能力和調整需求側電力負荷來升級電力系統的重要性，以降低部署PV和風力發電來實現中國碳中和的經濟成本。
▲ Abstract：
China’s goal to achieve carbon (C) neutrality by 2060 requires scaling up photovoltaic (PV) and wind power from 1 to 10–15PWh ?year?1. Following the historical rates of renewable installation, a recent high-resolution energy-system model and forecasts based on China’s 14th Five-year Energy Development (CFED), however, only indicate that the capacity will reach 5–9.5 PWh year?1 by 2060. Here we show that, by individually optimizing the deployment of 3,844 new utility-scale PV and wind power plants coordinated with ultra-high-voltage (UHV) transmission and energy storage and accounting for power-load flexibility and learning dynamics, the capacity of PV and wind power can be increased from 9 PWh year?1(corresponding to the CFED path) to 15 PWh year?1, accompanied by a reduction in the average abatement cost from US$97 to US$6 per tonne of carbon dioxide (tCO2). To achieve this, annualized investment in PV and wind power should ramp up from US$77 billion in 2020 (current level) to US$127 billion in the 2020s and further to US$426 billion year?1 in the 2050s. The large-scale deployment of PV and wind power increases income for residents in the poorest regions as co-benefits. Our results highlight the importance of upgrading power systems by building energy storage, expanding transmission capacity and adjusting power load at the demand side to reduce the economic cost of deploying PV and wind power to achieve carbon neutrality in China.
人工智能Artificial Intelligence
Heat-assisted detection and ranging
熱輔助探測和測距
▲ 作者：Fanglin Bao, Xueji Wang, Shree Hari Sureshbabu, Gautam Sreekumar, Liping Yang, Vaneet Aggarwal, et al.
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06174-6
▲ 摘要：
機器感知使用先進的傳感器來收集周圍場景的信息，以實現態勢感知。當智能代理數量增加時，使用主動聲納、雷達和激光雷達來增強相機視覺的最先進機器感知面臨諸多困難。利用無處不在的熱信號，有望擴展感知的新前沿。
然而，物體及其環境不斷地發射和散射熱輻射，導致了被稱為“重影效應”的無紋理圖像。因此，熱視覺不受信息丟失的特異性限制，而對導航至關重要的熱測距即使與人工智能（AI）相結合，也很難實現。
研究組提出并實驗證明了熱輔助探測和測距（HADAR）可克服重影這一公開挑戰，并將其針對AI增強的熱感測進行了基準測試。HADAR不僅能在黑暗中像白天一樣看到紋理和深度，還能感知到RGB或熱視覺之外的紛雜物理屬性，這為完全被動和物理感知的機器感知奠定了基礎。
研究組開發了HADAR估計理論，并解決了其光子散粒噪聲極限，該極限描述了基于HADAR的AI性能的信息理論邊界。HADAR在夜間的測距優于熱測距，其精度可與白天的RGB立體視覺相媲美。
該自動化HADAR熱成像技術在溫度精度上達到了Cramér–Rao界限，超越了現有的熱成像技術。該研究工作帶來了一種顛覆性技術，可通過基于HADAR的自主導航和人機社交來加速第四次工業革命（工業4.0）。
▲ Abstract：
Machine perception uses advanced sensors to collect information about the surrounding scene for situational awareness. State-of-the-art machine perception using active sonar, radar and LiDAR to enhance camera vision faces difficulties when the number of intelligent agents scales up. Exploiting omnipresent heat signal could be a new frontier for scalable perception. However, objects and their environment constantly emit and scatter thermal radiation, leading to textureless images famously known as the ‘ghosting effect’. Thermal vision thus has no specificity limited by information loss, whereas thermal ranging—crucial for navigation—has been elusive even when combined with artificial intelligence (AI). Here we propose and experimentally demonstrate heat-assisted detection and ranging (HADAR) overcoming this open challenge of ghosting and benchmark it against AI-enhanced thermal sensing. HADAR not only sees texture and depth through the darkness as if it were day but also perceives decluttered physical attributes beyond RGB or thermal vision, paving the way to fully passive and physics-aware machine perception. We develop HADAR estimation theory and address its photonic shot-noise limits depicting information-theoretic bounds to HADAR-based AI performance. HADAR ranging at night beats thermal ranging and shows an accuracy comparable with RGB stereovision in daylight. Our automated HADAR thermography reaches the Cramér–Rao bound on temperature accuracy, beating existing thermography techniques. Our work leads to a disruptive technology that can accelerate the Fourth Industrial Revolution (Industry 4.0) with HADAR-based autonomous navigation and human–robot social interactions.
地球科學Earth Science
Increased occurrences of consecutive La Ni?a events under global warming
全球變暖下連續拉尼娜事件頻率增加
▲ 作者：Tao Geng, Fan Jia, Wenju Cai, Lixin Wu, Bolan Gan, Zhao Jing, et al.
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06236-9
▲ 摘要：
大多數厄爾尼諾事件都是偶發性的，并在一個冬季達到峰值，而拉尼娜往往在厄爾尼諾之后發展，并持續兩年或更長時間。相對于單年拉尼娜，連續拉尼娜的特點是經向東風范圍更廣，因此赤道太平洋的熱量補給速度較慢，使寒冷異常現象持續存在，這對全球氣候、生態系統和農業產生長期影響。持續多年拉尼娜事件的未來變化仍然未知。
利用未來溫室氣體強迫下的氣候模型，研究組發現連續拉尼娜事件的頻率增加，范圍從低排放情景下的19±11%增至高排放情景下的33±13%，并得出高排放情景下頻率更強的模型間共識。
在溫室變暖的情況下，副熱帶東北太平洋的均態變暖最大值增強了針對擾動的區域熱力學響應，產生了比20世紀響應厄爾尼諾溫暖異常更北的異常東風。赤道東太平洋的一個變暖極大值進一步增加了向北更廣異常模式的敏感性。
較慢的熱量補給與向北更廣的偏東異常有關，使得第一年拉尼娜的寒冷異常一直持續到第二年拉尼娜。因此，在史上連續拉尼娜事件中出現的極端氣候可能在21世紀會更頻繁地發生。
▲ Abstract：
Most El Ni?o events occur sporadically and peak in a single winter, whereas La Ni?a tends to develop after an El Ni?o and last for two years or longer. Relative to single-year La Ni?a, consecutive La Ni?a features meridionally broader easterly winds and hence a slower heat recharge of the equatorial Pacific, enabling the cold anomalies to persist, exerting prolonged impacts on global climate, ecosystems and agriculture. Future changes to multi-year-long La Ni?a events remain unknown. Here, using climate models under future greenhouse-gas forcings, we find an increased frequency of consecutive La Ni?a ranging from 19 ± 11% in a low-emission scenario to 33 ± 13% in a high-emission scenario, supported by an inter-model consensus stronger in higher-emission scenarios. Under greenhouse warming, a mean-state warming maximum in the subtropical northeastern Pacific enhances the regional thermodynamic response to perturbations, generating anomalous easterlies that are further northward than in the twentieth century in response to El Ni?o warm anomalies. The sensitivity of the northward-broadened anomaly pattern is further increased by a warming maximum in the equatorial eastern Pacific. The slower heat recharge associated with the northward-broadened easterly anomalies facilitates the cold anomalies of the first-year La Ni?a to persist into a second-year La Ni?a. Thus, climate extremes as seen during historical consecutive La Ni?a episodes probably occur more frequently in the twenty-first century.
The social value of offsets
碳減排補償的社會價值
▲ 作者：Ben Groom & Frank Venmans
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06153-x
▲ 摘要：
目前尚不清楚為了補償一噸二氧化碳的排放，應當在臨時和有風險的補償中儲存多少碳。研究組將補償社會價值（SVO）作為反映補償持續時間以及非額外性和失敗風險的碳社會成本的一個明確部分，其中SVO按照避免的經濟損失來衡量。
SVO反映了臨時儲存的價值，并克服了先前氣候科學和經濟學的短板。SVO與政策相關。如果SVO/成本比超過替代方案的效益/成本比，則有效的凈零政策將包括補償。SVO提供了一個指標，通過SVO與碳社會成本之比來衡量補償與永久碳儲存的等效性。
研究組為不同的風險、持久性和氣候情景提供了等效因子矩陣。經估算得出一個經驗法則：在50年的時間里，每補償封存1噸碳，就相當于永久封存0.33~0.5噸碳。
等效策略提供了一種用更簡單、易于監督的短期合同取代永久補償合同的方法，可用于碳生命周期分析和碳債務估值，并可作為比較自愿和合規市場中不同質量補償的基礎。
▲ Abstract：