Is there life on Venus?
This was a hot topic last year. At the time, scientists detected phosphine (PH) in the clouds of Venus. On Earth, phosphine is a gas produced primarily through biological interactions, so the discovery has led scientists to think about the possibility of life on Venus. Since its publication, however, the discovery has sparked widespread controversy.
Venus is the closest planet to Earth, yet, in contrast to a vibrant Earth, the nearest neighbor is a scorching and suffocating wasteland. Its surface is hot enough to melt lead; its atmosphere is filled with thick carbon dioxide; even clouds are hostile to life as we know it—the entire planet is covered with droplets of sulfuric acid enough to burn human skin.
In this way, Venus really does not look like a world suitable for life. Still, the discovery of phosphine is like a key that opens up new windows to explore the possibilities of life on Venus, inspiring some scientists who study Venus.
Recently, a new study supports the long-standing idea that if Venus had life, it might have existed in Venus' clouds. These beings can neutralize the acidic environment in The Venus cloud by a chemical pathway, creating a self-sustaining living space in the clouds.
The new results were published in the recent Proceedings of the National Academy of Sciences.
In the new study, the researchers combed through data from past astronomical missions to Venus and found anomalies in Venus' clouds, such as very low concentrations of oxygen, non-spherical droplets of sulfuric acid, and unexpected levels of water vapor and sulfur dioxide. These phenomena have not been explained for decades, and the most puzzling of these phenomena is the presence of ammonia (NH).
Ammonia was first detected on Venus in the 1970s. At the time, the Venus 8 and Pioneer Venus probes had initially detected the gas in the clouds of Venus. Since then, the presence of ammonia has become an unsolved mystery related to Venus. Because any known chemical process on Venus should not be able to produce ammonia gas.
Paul Rimmer, an astronomer at the University of Cambridge, is one of the authors of the new study. He had speculated that perhaps we could use dust to explain these anomalies on Venus. Minerals swept into the clouds from the surface of Venus may interact with sulfuric acid, producing some of the anomalies that have already been observed. He gave the chemical principles that could justify this hypothesis, but found that this was not physically feasible: to produce observed anomalies, a large amount of dust would have to enter the clouds.
Sara Seager, a planetary scientist at the Massachusetts Institute of Technology who is another co-author of the study, wondered if these anomalies could be explained by ammonia.
Ammonia is a molecule that contains hydrogen, yet around Venus, only a small amount of hydrogen is present. So what exactly is the source of ammonia on Venus? They proposed a new hypothesis that the ammonia came from life on Venus, not from inanimate sources such as lightning or volcanic eruptions.
Does this hypothesis explain anomalies in Venus's clouds? To find out, they simulated a series of chemical processes.
Artistic Conception: The Biosphere that exists in the atmospheric clouds of Venus. In this image, imaginary microbes live in protective cloud particles in the Venus cloud, which drift with the wind around Venus. | Image credit: J. Petkowska via MIT News
The simulation results show that if life produces ammonia in the most efficient way, then the associated chemical reaction will naturally produce oxygen; once ammonia appears in the clouds, it will dissolve in sulfuric acid droplets, effectively neutralizing sulfuric acid, making the droplets relatively livable; in addition, the ammonia entering the droplets will make the original spherical form of the droplets into a non-spherical salty slurry. Once ammonia is dissolved in sulfuric acid, it also triggers the dissolution of the surrounding sulfur dioxide.
Thus, the presence of ammonia does explain most of the major anomalies seen in the clouds of Venus. Causes such as lightning, volcanic eruptions, and even meteorite impacts cannot produce ammonia that chemically explains these anomalies. The new model's predictions of the abundance of gases in Venus's atmosphere are more consistent with observations than any previous model, and are easy to verify.
Venus has incredible, unexplained atmospheric anomalies that leave room for the possibility of life. The new study provides a transformative hypothesis about the chemistry of clouds in Venus's atmosphere, suggesting that while any life we know cannot survive in a droplet of Venus, there may be some life there that is altering its environment to make it habitable.
In addition, the hypothesis proposed by the institute reconciles decades of atmospheric anomalies, and this hypothesis can eventually be tested. The new study provides a list of chemical signatures for some of the Venus life exploration programs to be launched in the coming years for them to probe for the presence of ammonia and signs of life in Venus' clouds, confirming or overturning this new idea.
#创作团队:
Text: No two Beidou
#参考来源:
https://news.mit.edu/2021/habitable-venus-clouds-acid-neutralizing-1220
#图片来源:
Cover image: J. Petkowska via MIT News