VOA科学技术2023--Study Suggests New Cause for Strongest ‘Marsquake’ Ever

Study Suggests New Cause for Strongest ‘Marsquake’ Ever

Scientists now believe the largest quake ever recorded on Mars was the result of seismic¹ 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.

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 differentiate² between seismic signals coming from inside Mars and activity coming from above the surface, such as wind or meteorite³ 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 crater⁴ that would have been created by a large meteorite hit.

The team was led by researchers from Britain's University of Oxford⁵. 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 craters⁶ 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 noted⁷, 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 decided⁸ 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 seismically⁹ active than previously¹⁰ 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 ongoing¹¹ 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 fully¹² 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 spoke¹³ 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."

Words in This Story

seismic – adj. relating to or caused by an earthquake

meteorite – n. a piece of rock from outer space that has fallen to a planet's surface

crater – n. a big hole left in the ground or an object by a force of impact

tectonic – adj. relating to the structure of the Earth and the way it is formed, changed and moved by forces inside it

stress –n. tension or strain

crust –n. the hard outer layer of certain things

unravel¹⁴ – v. to make something known or understood

1 seismic   

a.地震的，地震强度的

参考例句：

• Earthquakes produce two types of seismic waves.地震产生两种地震波。
• The latest seismic activity was also felt in northern Kenya.肯尼亚北部也感觉到了最近的地震活动。

2 differentiate   

vi.(between)区分；vt.区别；使不同

参考例句：

• You can differentiate between the houses by the shape of their chimneys.你可以凭借烟囱形状的不同来区分这两幢房子。
• He never learned to differentiate between good and evil.他从未学会分辨善恶。

3 meteorite   

n.陨石；流星

参考例句：

• The meteorite in Jilin Exhibition Hall is believed to be the largest in the world.吉林展览馆的陨石被认为是世界上最大的。
• The famous Murchison meteorite smashed into the Australian ground in 1969.1969年著名的默奇森陨石轰然坠落在澳大利亚。

4 crater   

n.火山口，弹坑

参考例句：

• With a telescope you can see the huge crater of Ve-suvius.用望远镜你能看到巨大的维苏威火山口。
• They came to the lip of a dead crater.他们来到了一个死火山口。

5 Oxford   

n.牛津（英国城市）

参考例句：

• At present he has become a Professor of Chemistry at Oxford.他现在已是牛津大学的化学教授了。
• This is where the road to Oxford joins the road to London.这是去牛津的路与去伦敦的路的汇合处。

6 craters   

n.火山口( crater的名词复数 )；弹坑等

参考例句：

• Small meteorites have left impact craters all over the planet's surface. 这个行星的表面布满了小块陨石留下的撞击坑。 来自《简明英汉词典》
• The battlefield was full of craters made by exploding shells. 战场上布满弹坑。 来自《现代英汉综合大词典》

7 noted   

adj.著名的，知名的

参考例句：

• The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
• Jim is noted for arriving late for work.吉姆上班迟到出了名。

8 decided   

adj.决定了的，坚决的；明显的，明确的

参考例句：

• This gave them a decided advantage over their opponents.这使他们比对手具有明显的优势。
• There is a decided difference between British and Chinese way of greeting.英国人和中国人打招呼的方式有很明显的区别。

9 seismically   

地震

参考例句：

• The crust and mantle are separated by a seismically determined boundary known as the Moho-discontinuity. 改译为：地壳与地幔的交接处系根据地波走失而确定的一个界面，通称为莫霍界面。 来自互联网
• China's code is now on par with similar codes in seismically active areas of the world. 中国现在施行的标准与世界其他地震活跃地区施行的标准基本一致。 来自互联网

10 previously   

adv.以前，先前（地）

参考例句：

• The bicycle tyre blew out at a previously damaged point.自行车胎在以前损坏过的地方又爆开了。
• Let me digress for a moment and explain what had happened previously.让我岔开一会儿，解释原先发生了什么。

11 ongoing   

adj.进行中的，前进的

参考例句：

• The problem is ongoing.这个问题尚未解决。
• The issues raised in the report relate directly to Age Concern's ongoing work in this area.报告中提出的问题与“关心老人”组织在这方面正在做的工作有直接的关系。

12 fully   

adv.完全地，全部地，彻底地；充分地

参考例句：

• The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气，然后全部呼出。
• They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。

13 spoke   

n.（车轮的）辐条；轮辐；破坏某人的计划；阻挠某人的行动 v.讲，谈（speak的过去式）；说；演说；从某种观点来说

参考例句：

• They sourced the spoke nuts from our company.他们的轮辐螺帽是从我们公司获得的。
• The spokes of a wheel are the bars that connect the outer ring to the centre.辐条是轮子上连接外圈与中心的条棒。

14 unravel   

v.弄清楚（秘密）；拆开，解开，松开

参考例句：

• He was good with his hands and could unravel a knot or untangle yarn that others wouldn't even attempt.他的手很灵巧，其他人甚至都不敢尝试的一些难解的绳结或缠在一起的纱线，他都能解开。
• This is the attitude that led him to unravel a mystery that long puzzled Chinese historians.正是这种态度使他解决了长期以来使中国历史学家们大惑不解的谜。