Study Suggests New Cause for Strongest ‘Marsquake’ Ever

Study Suggests New Cause for Strongest ‘Marsquake’ Ever

研究表明有史以来最强“地震”的新原因

【原文听力】

　　By Bryan Lynn

　　29 October 2023

　　Scientists now believe the largest quake ever recorded on Mars was the result of seismic activity, not a strike by a space object.

　　Instruments attached to the InSight lander identified the quake in 2021. The InSight lander is a Mars explorer operated by the American space agency NASA. On Earth, seismic activity causes earthquakes. Scientists often call seismic activity on Mars "marsquakes."

　　NASA estimated the largest marsquake had a strength of 4.7. While this level of quake would not be considered major on Earth, it is very powerful on Mars.

　　This artist's concept shows a cutaway of Mars, along with the paths of seismic waves from two separate quakes in 2021. (NASA/JPL-Caltech/University of Maryland)

　　Scientists say a marsquake happens when Martian soil is subjected to a buildup of pressure so great that it causes rock structures to break. So far, the InSight lander has identified, or detected, more than 1,300 marsquakes. The explorer uses a device called a seismometer to detect the ground movements.

　　The seismometer was designed to be extremely sensitive for the Martian environment. It aims to differentiate between seismic signals coming from inside Mars and activity coming from above the surface, such as wind or meteorite strikes.

　　Researchers look at other things to confirm whether a marsquake was caused by seismic activity below the surface or by an outside force hitting the planet. In the case of the strongest marsquake ever recorded, an international team of scientists looked for evidence of a crater that would have been created by a large meteorite hit.

　　The team was led by researchers from Britain's University of Oxford. But scientists working for space agencies in Europe, China, India and the United Arab Emirates also took part. China has an explorer on Mars and the other agencies all have spacecraft orbiting the planet.

　　A recently released study describes the findings in Geophysical Research Letters.

　　The research team estimated that a 4.7-level marsquake would have created a crater at least 300 meters in diameter. Two other large marsquakes left craters of about 150 meters. So, the researchers searched satellite data collected by InSight as well as the other space agencies.

　　Each agency examined data from their satellites for evidence of a large crater, as well as other signs that a meteorite might have struck before the largest marsquake. Another sign, team members noted, could have been a dust cloud appearing in the hours after the quake.

　　But after several months of searching, the researchers said no new, larger crater was found. They said their examinations ruled out a meteorite strike as the cause of the 4.7 marsquake.

　　The researchers decided instead that the largest marsquake must have been caused by the release of powerful "tectonic forces" at work deeper inside the Red Planet. This finding suggests that Mars "is much more seismically active than previously thought," the Oxford University team said in a statement.

　　Benjamin Fernando is a professor of physics at Oxford University who led the study. He said in a statement that scientists do not believe Mars has ongoing tectonic movements. Rather, Fernando said the team thinks the largest marsquake was "caused by the release of stress within Mars' crust."

　　He added that such stress is likely the result of billions of years of development on Mars, including the cooling and shrinking of different parts of the planet at different speeds. "We still do not fully understand why some parts of the planet seem to have higher stresses than others, but results like these help us to investigate further," Fernando said.

　　Constantinos Charalambous is a planetary scientist at Imperial College London who helped lead the research. He spoke to Reuters news agency about the finding. He said it "represents a significant step forward in our understanding of Martian seismic activity – and takes us one step closer to better unraveling the planet's tectonic processes."

　　Fernando added, "One day, this information may help us to understand where it would be safe for humans to live on Mars and where you might want to avoid."

　　I'm Bryan Lynn.

　　Bryan Lynn wrote this story for VOA Learning English, based on reports from Reuters, the University of Oxford and NASA.

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　　布莱恩·林恩

　　2023年10月29日

　　科学家们现在认为，火星上有史以来最大的地震是由地震的活动，而不是空间物体的撞击。

　　InSight着陆器上的仪器识别出了2021年的地震。InSight着陆器是由美国航天局NASA运营的火星探测器。在地球上，地震活动引起地震。科学家通常称火星上的地震活动为“地震”

　　美国宇航局估计最大的火星地震强度为4.7级。虽然这种级别的地震在地球上不会被认为是大地震，但在火星上却非常强烈。

　　这位艺术家的概念展示了火星的剖面图，以及2021年两次独立地震的地震波路径。(美国国家航空航天局/JPL加州理工学院/马里兰大学)

　　科学家说，当火星土壤受到如此大的压力积累，导致岩石结构破裂时，就会发生地震。到目前为止，洞察号着陆器已经识别或探测到了1300多次地震。探险者使用一种叫做地震仪的设备来探测地面运动。

　　地震仪被设计成对火星环境极其敏感。它旨在区分来自火星内部的地震信号和来自地表以上的活动，如风或地震流星罢工。

　　研究人员观察其他东西来确认火星地震是由地表下的地震活动引起的，还是由撞击地球的外力引起的。在有史以来最强的地震中，一个国际科学家小组寻找证据火山口那可能是由大陨石撞击造成的。

　　该小组由英国牛津大学的研究人员领导。但是为欧洲、中国、印度和阿拉伯联合酋长国的太空机构工作的科学家也参加了。中国在火星上有一个探索者，其他机构都有绕火星飞行的宇宙飞船。

　　A 最近发布的研究描述了中的发现地球物理研究快报.

　　研究小组估计，一场4.7级的地震将会造成一个直径至少300米的陨石坑。另外两次大地震留下了大约150米的陨石坑。因此，研究人员搜索了InSight和其他太空机构收集的卫星数据。

　　每个机构都检查了来自卫星的数据，以寻找大型陨石坑的证据，以及最大地震前陨石可能撞击的其他迹象。小组成员指出，另一个迹象可能是地震后几小时出现的尘云。

　　但是经过几个月的搜索，研究人员说没有发现新的更大的陨石坑。他们说，他们的检查排除了陨石撞击是4.7级地震的原因。

　　相反，研究人员认为最大的地震一定是由释放强大的建筑的“在这颗红色星球内部更深处工作的力量”。牛津大学的研究小组称，这一发现表明火星“比以前认为的更加地震活跃”说在一份声明中。

　　本杰明·费尔南多是领导这项研究的牛津大学物理学教授。他在一份声明中说，科学家不相信火星有持续的构造运动。相反，费尔南多说，该小组认为最大的地震是“由释放的强调“在火星内部”外壳."

　　他补充说，这种压力可能是火星上数十亿年发展的结果，包括地球不同部分以不同速度冷却和收缩。费尔南多说:“我们仍然不完全明白为什么地球上的一些地方似乎比其他地方压力更大，但这些结果有助于我们进一步调查。”

　　康斯坦丁诺斯·沙拉兰鲍斯是伦敦帝国理工学院的行星科学家，他帮助领导了这项研究。他向路透社讲述了这一发现。他说，这“代表着我们对火星地震活动的理解向前迈出了重要的一步——并使我们更进一步解开地球的构造过程。"

　　费尔南多补充说，“有一天，这些信息可能会帮助我们了解人类在火星上生活在哪里是安全的，以及你可能想要避免的地方。”

　　我是布莱恩·林恩。

　　布莱恩·林恩根据路透社、牛津大学和美国国家航空航天局的报道，为美国之音英语学习撰写了这篇报道。

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　　这个故事中的词语

　　seismic – adj. 关于地震的或由地震引起的

　　meteorite – n. 从外层空间坠落到行星表面的一块岩石

　　crater – n. 冲击力在地面或物体上留下的大洞

　　tectonic – adj. 与地球的结构及其内部力量形成、改变和移动的方式有关的

　　stress –n. 紧张或紧张

　　crust –n. 某些事物坚硬的外层

　　unravel – v. 使某事为人所知或理解