[ti:Scientists Record Largest 'Marsquakes' on the Red Planet]
[al:Science & Technology]
[ar:VOA]
[dt:2022-05-02]
[by:www.voase.cn]
[00:00.00]Scientists say they have identified the two largest "marsquakes" ever recorded on the Red Planet.
[00:12.15]A marsquake is a seismic event that happens on Mars.
[00:18.66]It is similar to earthquakes that happen on our planet.
[00:23.72]The activity was recorded by a device called a seismometer. 
[00:30.82]It is attached to the InSight lander, a spacecraft operated by the American space agency NASA.
[00:41.46]The seismometer was designed to be extremely sensitive for the Martian environment. 
[00:50.44]It aims to differentiate between seismic signals coming from inside Mars and activity coming from above the surface, such as wind or meteorite movements.
[01:07.48]One of the marsquakes happened on August 25, 2021. 
[01:14.48]It had a magnitude of 4.2. The other, on September 18, 2021, measured 4.1.
[01:26.24]An international team, led by researchers from Britain's University of Bristol, confirmed the seismic activity.
[01:37.45]The findings were recently reported in a study in the publication The Seismic Record.
[01:46.21]A marsquake happens when soil on Mars is subjected to a buildup of pressure so great that it leads rock structures to break, explains ETH Zurich. 
[02:02.35]ETH Zurich is a public research university in Zurich, Switzerland. 
[02:09.44]Researchers from the university took part in the latest study.
[02:16.66]The InSight lander brought the first seismometer to Mars in late 2018. 
[02:24.54]It recorded its first marsquake in April 2019. 
[02:31.34]Since then, it has recorded hundreds of marsquakes.
[02:37.25]But examinations of the two reported in the study suggest they were largest yet to hit Mars. 
[02:47.95]The researchers said the two marquakes were five times stronger than any others recorded before.
[02:58.00]They were also the first seismic events to happen on the planet's far side from where the InSight lander sits.
[03:09.82]The study notes that as of October 2021, records from InSight included nearly 1,000 seismic events. 
[03:22.26]All of those happened on the side of Mars where the spacecraft operates, in an area called Elysium Planitia.
[03:33.60]NASA says that area sits just north of Mars' equator and is the second largest volcanic area on the planet.
[03:45.22]As the seismic activity was still being studied, NASA noted in a statement last September that it appeared the 4.2 marsquake happened about 8,500 kilometers from the InSight lander.
[04:05.63]Both large marquakes happened in an area known as the "core shadow zone," said a statement by the Seismological Society of America.
[04:20.11]That is a part of Mars where some kinds of seismic waves cannot travel directly to InSight's seismometer.
[04:30.70]This is because the waves get blocked or are otherwise affected by the planet's core.
[04:38.87]The waves instead get "reflected at least once at the surface before traveling to the seismometer," the society statement said.
[04:51.67]"Recording events within the core shadow zone is a real stepping-stone for our understanding of Mars," said Savas Ceylan, a researcher with ETH Zurich who helped lead the study. 
[05:09.99]He added that the energy that travels within the core shadow of Mars has never been seismologically studied before.
[05:21.36]The researchers say such seismic wave data can help them learn more about deeper layers within Mars, as well as the planet's current seismic activity.
[05:36.60]I'm Bryan Lynn.