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Not far from the earth, cosmologically, there is a planet almost exactly like the earth. It is about the size of the earth, made of the same things and formed around the same stars.

For an alien astronomer who is light years away, observing the solar system through a telescope is actually similar to our planet. But knowing the surface condition of Venus-the temperature like a self-cleaning oven, and the saturated carbon dioxide and sulfuric acid clouds in the atmosphere is equivalent to knowing that it is not like the earth at all.

So, why do two planets with similar positions, shapes and compositions have such different results? This is a problem that puzzles more and more planetary scientists, and it has also inspired many proposed explorations of Venus. If scientists can understand why Venus is like this, we can better understand whether planets like Earth have the same fate.

I am a planetary scientist, and I am fascinated by how other worlds came into being. I am particularly interested in Venus, because it shows us a world that may not be much different from ours.

The surface of Venus seen from the panoramic view of the reprocessed perspective image of the Soviet Vinara 13 lander.

Once the blue Venus?

At present, the scientific view of Venus is that at some point in the past, there was much more water on Venus than the dry atmosphere now, and it may even be an ocean. But as the sun gets hotter and brighter (the natural result of aging), the surface temperature of Venus rises and eventually evaporates all the oceans.

With more and more water vapor in the atmosphere, Venus entered the runaway greenhouse and could not recover. Whether the earth-like plate structure (the outer layer of the planet is broken into large and movable fragments) has ever operated on Venus is still unknown. Water is the key to the operation of plate tectonics, and the runaway greenhouse effect will effectively close the process of running there.

But the end of plate tectonics does not mean the end of geological activities. The heat energy inside the planet constantly produces magma, which spews out in the form of a large number of lava flows and reshapes the surface of the planet. In fact, the average surface age of Venus is about 700 million years-very old, of course, but billions of years younger than the surface of Mars, Mercury or the moon.

In the artist's impression, what Venus, once rich in water, might look like.

The exploration of planet 2

"Venus has water" is just a hypothesis. Planetary scientists don't know what makes Venus so different from the Earth, or even whether the two planets really have the same conditions from the beginning. People's understanding of Venus is not as good as our understanding of other inner planets in the solar system, mainly because this planet has brought several unique challenges to human exploration.

For example, radar needs to penetrate opaque sulfuric acid clouds to see the surface of Venus clearly. This is much harder than those surfaces that are easy to see, such as the moon or mercury. Moreover, the surface temperature of 470 degrees Celsius (880 degrees Fahrenheit) means that the life of traditional electronic equipment will not exceed a few hours. This is far from the fact that the rover can work on Mars for more than ten years. Partly because of its high temperature, acidity and inconspicuous surface, Venus has not made a continuous exploration plan in the past few decades.

The artist's impression of Venus, which was once rich in water. Light with visible wavelength can't penetrate the thick clouds on Venus. Instead, we need to use radar to observe the surface of Venus from space. This is a mosaic of Venus global radar images composed of data returned by Magellan mission.

However, there were two special Venus missions in 2 1 century: the Venus Express of the European Space Agency (operated from 2006 to 20 14) and the Dawn spacecraft of the Japan Aerospace Exploration Agency (JAXA) are currently in orbit.

Humans don't always ignore Venus. It was once the darling of planetary exploration. Between the 1960s and 1980s, about 35 missions were sent to the second planet. 1962, NASA's Mariner 2 mission was the first spacecraft to successfully meet a planet while flying over Venus. The first images sent back from the surface of another world were issued after the landing of the Vinara 9 lander of the Soviet Union in 1975. Vinara 13 lander is the first spacecraft to return sound from the surface of another world. But NASA's last mission to Venus was the Magellan in 1989. Before 1994, when the spacecraft died in the atmosphere of Venus, almost the entire surface of Venus was photographed by radar.

Back to Venus?

In the past few years, NASA has sent several missions to Venus. The planetary mission chosen by NASA is a nuclear-powered spacecraft named Dragonfly, and its destination is Saturn's moon Titan. However, a proposal to measure the surface composition of Venus was selected for further technical development.

Other tasks under consideration include ESA's task of mapping the surface of Venus with high resolution, and Russia's plan. As the only country that successfully put a lander on the surface of Venus, the plan aims to carry on the tradition and make persistent efforts.

About 30 years after NASA set the course for our hellish neighbors, the future of Venus exploration looks promising. However, the task of radar orbiter or even long-life lander alone cannot solve all the outstanding mysteries.

On the contrary, we need a continuous exploration plan to make our understanding of Venus reach the same level as that of Mars or the moon. It takes time and money, but I believe it is worth it. If we can understand why Venus has become what it is now, we can better understand how the earth-sized world evolved as it approached the stars. In addition, Venus can even help us understand the fate of the earth in the brighter and brighter sun.

By Paul K. Bourne

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