Is there really life on Enceladus? Chinese scientists found the last piece of the puzzle

Enceladus is the second satellite of Saturn discovered by humans. Now, in terms of size, Enceladus is the sixth satellite of Saturn. As of 2019, people have discovered that Saturn has 82 satellites, which is more than Jupiter's 79, making it the planet with the most satellites in the solar system.

After exploration and analysis, scientists generally believe that there are very few planets in the solar system that may have life. Mars is the only planet with a high probability of having life, and the rest are several satellites, roughly Enceladus, Titan, and Ganymede. Enceladus is ranked first because it has a large amount of liquid water on it.

Journey of Discovery

Among the several extraterrestrial satellites that may harbor life, Enceladus is the smallest, with a diameter of only about 500 kilometers, only about one-tenth of Titan. Due to its small size and distance from the sun, its albedo is extremely high, reaching 1.38 (the earth is only 0.37), so all the sun's energy is emitted, resulting in an extremely low surface temperature of only 75K (-198℃).

Scientists used to believe that this planet, which is covered with thick ice, has too little internal energy to support the long-term existence of liquid water, and the possibility of life is low. However, the Voyager 1 and 2 sister probes launched by NASA in the last century made amazing discoveries.

These two unmanned probes flew past Saturn in 1980 and 1981 respectively. Voyager 2, in particular, flew closer to the surface of Enceladus at a distance of 87,000 kilometers, obtaining a large amount of data including clear images of Enceladus. Scientists speculated from the distribution of craters on its surface and some young landforms that there is still strong energy activity inside the planet, which caused a sensation in the world scientific community.

In order to further understand the state of Enceladus, NASA launched the Cassini unmanned spacecraft in 1997, which reached the orbit around Saturn in 2004. As the most important observation target, Cassini flew over Enceladus many times at different distances, with the closest distance to its surface being only 50 kilometers. Through a comprehensive survey of the planet, it discovered many surprising facts.

The surface of Enceladus is rich in tiger stripes, that is, there are many parallel cracks on the surface, indicating that there is a lot of geological activity on Enceladus. There are also many ice volcanoes on the surface of Enceladus, and the plumes ejected are as high as 250 kilometers. Cassini passed through these plumes and obtained samples. After chemical analysis, it was found that there are rich inorganic and organic substances in them, including carbon, hydrogen, oxygen, nitrogen, sulfur and their compounds.

These discoveries indicate that there is a deep underground ocean on Enceladus, and that there is a heat source environment, which is an environment that supports the existence of life. Therefore, Enceladus is identified as one of the planets in the solar system that is most likely to have extraterrestrial life.

But until now, phosphorus, one of the six basic elements for life, has not been found. On Earth, phosphorus is generally considered to be a key nutrient element that limits the origin of life and the scale of organisms. So, is there phosphorus in the seawater of Enceladus? Will the presence of phosphorus limit the origin and habitability of life on Enceladus?

This question has been puzzling the scientific community, and scientists hope to find the last piece of the puzzle for the existence of life.

Chinese scientists have completed the final piece of the puzzle of the conditions for the existence of life through modeling research

In Earth's seawater, phosphorus often exists in the form of orthophosphoric acid (HxPO4-), and its solubility is extremely low, only 10^-7molal. The seawater of Enceladus is believed to be alkaline, with a pH between 8.5 and 11, and a large amount of H2 is reduced. What effect will this very different seawater chemistry have on phosphorus chemistry? Clarifying this question is the key to whether there is phosphorus in the seawater of Enceladus.

Hao Jihua, a researcher at the School of Earth and Space Sciences of the University of Science and Technology of China, collaborated with scholars such as Christopher Green of the Southwest Research Institute of the United States to construct a water-rock interaction model for the subglacial ocean of Enceladus by interpreting data sent back by NASA's Cassini probe, and simulated the chemical environment of the seawater of Enceladus.

The results show that in the special ocean environment of Enceladus, phosphorus still exists in the form of orthophosphate, and can reach a content of 10^-5 to 10^-3 molal, which is several orders of magnitude higher than the phosphorus concentration in the Earth's ocean. This is due to the alkalinity and high carbonate characteristics of Enceladus' seawater, which leads to very low content of alkaline earth and transition metal elements, thereby increasing the solubility of phosphate minerals.

This phenomenon has been confirmed in many alkaline and high-carbonate lakes on Earth. According to this model, it can be considered that the water of Enceladus contains abundant dissolved phosphate, which can support the origin and reproduction of microorganisms there. This research result was published in the world-class academic journal "Proceedings of the National Academy of Sciences of the United States", revealing for the first time the existence of phosphorus, a key nutrient element for life on Enceladus, filling the gap in the study of the habitability of the ocean of Enceladus.

This achievement can be considered as the last piece of the puzzle in the search for the conditions for the existence of life on Enceladus, and it is of great significance. The project research is mainly carried out by Chinese scholars, and has received support and funding from the Ministry of Science and Technology of China, the Chinese Academy of Sciences, and the University of Science and Technology of China. Therefore, the first corresponding author of the published paper is Hao Jihua, and the first corresponding unit is the University of Science and Technology of China.

So, what kind of life could exist on Enceladus?

Enceladus is almost an ice ball, its surface is covered with dazzling white ice, and it is the planet with the highest albedo in the solar system, so it is very cold. The surface of Enceladus is covered with glacial mountains and gullies, and some large canyons are about 200 kilometers long, 5 to 10 kilometers wide, and about 1 kilometer deep.

On the surface of Enceladus, especially in the South Pole, there are some "volcanoes" that are constantly erupting, but what they spew out is not hot lava, but ice, water and volatile gases, forming plumes hundreds of kilometers high, forming gas clouds above Enceladus. Cassini flew through these gas clouds and plumes and obtained cloud samples.

The onboard scientific instruments analyzed and found that the plumes and clouds are mainly water vapor, and also contain a small amount of molecular nitrogen, methane and carbon dioxide. Scientists call these constantly erupting "volcanoes" "ice volcanoes" and the erupted materials "ice plumes".

It is these phenomena that make scientists suspect that there is a huge ocean beneath the frozen surface of Enceladus. This ocean is located 20 to 30 kilometers below the ice layer on the surface of Enceladus. It is conservatively estimated to be 10 to 20 kilometers deep, and some estimate it to be as deep as 65 kilometers. There is also energy activity in the core deep in the ocean.

The average depth of the Earth's ocean is only 3.6 kilometers, which is nothing compared to Enceladus. Studies have found that the ocean of Enceladus contains various elements for the existence of life. The research results of Hao Jihua and others have filled in the last piece of the puzzle for the elements for the existence of life.

But even so, the possibility of life on Enceladus is still just a hypothesis, and whether it exists or not still needs further exploration in the future. NASA plans to send a special probe to the surface of Enceladus in the future, drill through the thick ice layer, and let AI go deep into the ocean to find out.

Currently, NASA scientists are still analyzing the data sent back by the long-dead Casio probe. It is said that there is a drop of water obtained from the ice plume of Enceladus. Whether there will be signs of life in it is still unknown. However, scientists generally believe that even if there is life on Enceladus, it is very low-level life, just like the low-level organisms near the deep-sea hydrothermal vents on Earth, and it is very likely to be completely different from the life on Earth.

Therefore, don't expect too much, as it is unlikely that there are advanced organisms like Earth's terrestrial animals, let alone alien civilizations. However, even if a bacterium or cell is found on Enceladus, it will be a breakthrough that will rewrite the history of life in the universe, which is worth looking forward to.

Because, so far, scientists have exhausted almost everything, but have not found any trace of extraterrestrial life. That's all for today, thank you for reading, welcome to discuss.

This work is the original copyright of Space-Time Communication. Please respect it and do not plagiarize it. Thank you for your understanding and support.