You are still looking at the surface of Mars, but scientists have seen the inside of Mars. What is it like there?

2020 is the Year of Mars, and human beings have launched three probes to explore Mars in one breath, namely Tian Wen-1 in China, Perseverance in the United States and Hope in the United Arab Emirates.

At the beginning of this year, three probes arrived on Mars one after another, and two rovers landed smoothly, exploring the surface of Mars and sending back a series of spectacular photos of the surface of Mars. However, while we are still experiencing the surface environment of Mars, scientists have gradually seen the internal structure of Mars. It is not the above three detectors that lead us to see the inside of Mars, but another detector-Insight.

Insight is a Mars lander launched by NASA in May 20 18. Its main purpose is to understand the internal structure of Mars. Since landing, it has measured more than 700 Mars earthquakes, and used the data of 35 times to help scientists draw an unprecedented map of Mars crust, Mars mantle and Mars core. This is the first time in human history to use seismic data to study the internal structure of other planets.

Earthquake is indeed one of the most terrible natural disasters on earth, but it is an important tool for scientists to study the structure of celestial bodies on a planet without people. When vibration occurs at a certain position deep in the ground surface, seismic waves will begin to spread in all directions around, and different substances will produce different propagation and reflection effects. By analyzing these characteristics, scientists can infer what is inside the planet.

Unlike the earth, Mars seems to be relatively calm. We know that earthquakes are the result of plate movements, but there is no plate structure on Mars. Although there are some very old volcanic areas on Mars, there has been no new volcanic activity recently. Even deeper, Mars doesn't seem to have an inner core that rolls in a molten state like the Earth, so it doesn't even have a magnetic field. Therefore, for a long time, many people thought that there would be no earthquake on Mars.

I have to say that in this case, NASA still insists on launching Insight, which is really courageous. Fortunately, in April 20 19, it detected the first vibration from the depths of Mars-the bold attempt was not in vain, and we will be able to understand the internal structure of Mars through the earthquake!

Subsequently, the earthquake detection work progressed smoothly, and more than 700 Mars earthquakes were recorded, 35 of which were strong enough to help scientists analyze. This ratio seems a little low, but considering that there is no plate activity on Mars, Insight is fighting alone, unlike the use of multiple monitoring stations on the earth to obtain data, 35 times has been quite a lot. What's more, this is enough for scientists to analyze.

Bridget Knapmeyer-Ndren of the University of Cologne, Germany, introduced the principle of insight. He said: "Seismology is mainly measured by speed comparison, and the propagation speed of seismic waves in different substances is different. And just like light, we can observe phenomena similar to reflection and refraction. "

Finally, these data enabled scientists to output three papers in one breath, introducing the three-layer structure of Mars crust, Mars mantle and Mars core respectively, and introducing the mysterious structure of this red planet hidden under the surface to the world in Science magazine.

The main content of the first article is to introduce the structure and characteristics of the crust of Mars. The researchers pointed out that the Martian crust is about 24-72 kilometers thick and has at least two layers of structure.

They also found that the top layer of the Martian crust shows amazing porosity, especially in the area where Insight landed, and the crust is surprisingly thin. The researchers pointed out that the reason for this phenomenon should be that the content of radioactive elements in the crust is relatively high, which is beyond previous imagination.

The second paper discusses the Martian mantle. Insight data show that this layer is basically composed of simple rock layers, and the thickness of the lithosphere has reached 400-600 kilometers. Like the Martian crust, the Martian mantle may contain more radioactive elements.

In the last paper, the researchers introduced the Martian nucleus. They pointed out that the core of Mars is much larger than previously thought, reaching 1830 km. You know, the radius of Mars is 3390 kilometers, which means that the radius of the core of Mars is more than half of the radius of the planet, which is about 200 kilometers larger than previously predicted.

In addition, according to the seismic data, the researchers found that the core of Mars is also liquid. Considering that the core of Mars is larger than expected and its mass is certain, it means that the density of the core is lower. Based on this, the researchers speculate that perhaps the core elements are relatively light nonmetallic elements such as sulfur, oxygen, carbon and hydrogen, as well as heavy metals such as iron and nickel.

Simon St, a planetary seismologist at the Federal Institute of Technology in Zurich, Switzerland? Heller said: "In order to study the earth's core, scientists have spent hundreds of years; After the Apollo mission, they spent 40 years measuring the lunar nucleus. It took Insight only two years to detect the core of Mars. "

The exploration of the interior of Mars, especially the earth's core, helps scientists to understand how Mars lost its magnetic field and internal generator to a great extent. It is because of the loss of the magnetic field that the water vapor and other gases on Mars have finally changed from one of the most livable celestial bodies to today's desolate world.

At the same time, we can also use this to study the operating mechanism of the earth's magnetic field, which is equally important to us.

Although humans can't dig through the earth at present, we not only have the means to understand the interior of the earth, but also can study the interior of other planets.

However, whether it is this insight study or the study of the interior of the earth, we are still in a very primary stage. It is no exaggeration to say that we don't know as much about the interior of the earth as we do about the universe.