Exploring Mars in Progress / Above
Mars, like Venus, is a planet in the solar system that is in close proximity to the Earth, and has been studied for many years. In November 2018, NASA successfully landed on the Elysium Plain of Mars by developing the spacecraft InSight, which aims to elucidate the internal structure of Mars.
After that, we installed ultra-sensitive seismometers, and since the first-ever earthquake on Mars (also called a “firequake” because of Mars) in April 2019, we have observed a total of 1,319 earthquakes by the end of the mission in December 2022. Succeeded in detecting an earthquake.
In general, earthquakes occur when bedrock cracks under stress within the earth. Faults are formed in places where cracks occur, and earthquakes occur after repeated movements. The same is true for Mars, where the surface shrinks and pulls as it cools by releasing heat into space. This stress is believed to cause rocks to crack and cause earthquakes.
Mars is not as active as Earth, with the largest quake of 4.7 on May 4, 2022. Meanwhile, seismometers have also detected the tremors caused by meteor impacts on the surface of Mars, and several impact craters have been identified so far.
Identified in 2 years of observation
Furthermore, by collecting many earthquakes that occur on Mars, we can learn more about underground conditions. The same method is used to understand the internal structure of the Earth, but the difference in seismic wave velocity and waveform determines whether there is solid or liquid in the path. As a result, it was found that the same “core” as the Earth exists at the deepest part of Mars, and details such as the thickness of the “mantle” and “crust” above it were revealed.
It was found that the surface of Mars has a crust with a thickness of about 20 to 40 km, a mantle with a thickness of about 1,600 km, and a core with a radius of about 1,800 km at the deepest part. Also, since the mantle is solid but the core is liquid, the central half of Mars, which has a radius of about 3,400 kilometers, is molten. On Earth, which is twice the size of Mars, a solid inner core is surrounded by a liquid outer core (see Part 99 of this series).
Both Earth and Mars have followed the same history as planets in the solar system, born about 5 billion years ago. Until about 4 billion years ago, directly…
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