To this day, all major celestial bodies in the solar system have been "visited" at close range by human probes, and some probes have even directly brought soil from alien planets back to the earth. In addition to the moon, soil from asteroids hundreds of millions of kilometers away has been brought back.
However, Mars is an exception. Although Mars is a key exploration target for humans, and there are still many Mars rovers launched by humans operating on Mars, so far, humans have never brought soil from Mars back to Earth. This situation makes people curious, how terrible is Martian soil? Why don’t humans dare to bring Martian soil back to Earth?
After years of exploration, humans have gained a certain understanding of Mars. Various signs indicate that a long time ago, there was a natural environment suitable for life on Mars. Therefore, a common idea is that there may be some unknown creatures in the Martian soil. If the Martian soil is brought back to the earth rashly, it may trigger a terrible "interstellar biological invasion."
However, judging from the harsh natural conditions on Mars now, it is almost impossible for life to survive in the soil on the surface of Mars. To say the least, even if there is life in the Martian soil, it will only be some simple microorganisms at most. As long as humans take good protection (for modern humans, this is very easy to do), there will be no problem.
It can be seen from this that Martian soil is not terrible, and humans are not "dare to bring Martian soil back to Earth." In fact, the main reason why humans have not brought Martian soil back to Earth is actually technical problems.
Bringing soil from alien planets back to Earth can actually be simply divided into four steps: 1. Launch a probe to the target planet; 2. The probe lands on the target planet and collects soil samples, then seals them and places them in the returner; 3. The probe launches the returner from the surface of the planet to free it from the gravitational constraints of the target planet; 4. The returner returns to Earth with the sealed sample sample.
For the return of samples from Mars, the most technically difficult step is step 3. Although Mars is much smaller than the Earth, it is a large planet after all, and its gravity is still relatively strong. According to scientists' estimates, the escape velocity on the surface of Mars is about 5.027 kilometers/second, which requires a lot of fuel.
Considering that there is no fuel supply on Mars, these fuels must be carried by the probe when it is launched from the earth. And we all know that if you want to send an object of a certain mass from the surface of the earth to space, you need much more fuel than the mass of the object to provide power for launch. As a result, the difficulty and cost of launch will increase exponentially.
In addition, Mars also has an atmosphere. Although it is much thinner than the Earth's atmosphere, it will still cause a lot of trouble for the launch of the returner.
Relatively speaking, the escape velocity of the moon is only about 2.4 kilometers/second, and there is no atmosphere. As for asteroids, in addition to having no atmosphere, their gravity is so weak that it can be ignored. For example, the asteroid "Ryuugu" sampled by "Hyabusa 2" has an escape velocity of only about 1 meter/second, so the technical difficulty of sampling and returning from the moon and asteroids is much lower.
It is worth mentioning that although it is technically difficult to bring Martian soil back to Earth, it is not impossible with the current level of human science and technology. In fact, humans have already proposed two plans to return samples from Mars.
One of them is the "Mars Sample Return" (MSR) from NASA and ESA. Steps 1 and 2 of this plan have been initially completed by "Perseverance". The probe carries 43 test tubes for collecting Martian rock, soil and atmosphere samples. Some of them have been sampled and are currently waiting for the next mission.
It is expected that in 2026, another spacecraft will be launched from the surface of the Earth. When it reaches Mars, it will orbit Mars. After that, the collected Martian samples will be launched from the surface of Mars by a small rocket and then docked with the spacecraft orbiting Mars. Then this spacecraft will embark on its return journey and bring Martian samples back to Earth in 2031.
Another plan is my country's "Tianwen-3" Mars exploration mission. As we all know, our country's "Tianwen-1" Mars exploration mission has been successfully completed. In fact, "Tianwen-1" is just the beginning of a series of missions for our country to explore deep space. According to the plan, our country will implement the "Tianwen-2" asteroid detection mission in 2025. This mission will accompany an asteroid numbered "2016HO3" and return samples.
"Tianwen-3" will directly return Martian samples to Earth. According to the plan, "Tianwen-3" will be launched in 2028, and will fly to Mars, land on Mars and return samples on the surface of Mars in one go. It is expected that in 2031, we will obtain soil from Mars. I have to say, this is really exciting.
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