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Enceladus, one of Saturn's largest moons, is a potential habitat for extraterrestrial microbial life. Researchers at HSE University and Space Research Institute of RAS have calculated the characteristics of dusty plasma and electric fields, and the densities of photoelectrons near the surface of Enceladus. Despite the satellite’s large distance from the Sun, the photoelectric effect plays a significant role in the formation of dusty plasma over Enceladus. The paper has been published in the Journal of Experimental and Theoretical Physics Letters.
Outer space is filled with myriads of tiny dust particles. Solar radiation and interactions with electrons and ions from surrounding plasma causes these particles to become charged and to form an essential component of the space medium known as dusty plasma. Plasma is the fourth state of matter, beyond the solids, liquids, and gases. Dusty plasma contains electrons, ions, neutral particles, as well as charged solid particles and/or liquid droplets. It forms over the surfaces of planets, within cosmic clouds, and in the space between celestial bodies.
Enceladus is the first object in the outer Solar System where dusty plasma has been observed. It is the sixth largest and the 14th most distant of Saturn's 146 moons. This satellite is considered one of the most promising locations for the existence of extraterrestrial microbial life within the Solar System. Scientists also suggest that the penultimate ring of Saturn was formed due to the activity of Enceladus' cryovolcanoes that eject fountains of ice and silicate particles.
Using a physical and mathematical model, scientists at HSE University and RAS Space Research Institute determined the properties of dusty plasma, electric fields, photoelectrons, and their distribution depending on altitude in the near-surface layer of Enceladus.
The photoelectric effect above the surface of the satellite influences plasma formation: photons of light eject photoelectrons from the surface of Enceladus and dust particles, causing the dust to become charged. The scientists note that despite Enceladus being located at a distance of about 10 astronomical units from the Sun (equivalent to 10 times the distance from the Sun to Earth), a significant photoelectric effect is observed on its surface.
We had expected that due to the distance of both Saturn and Enceladus from the Sun, solar radiation would not play a substantial role in the formation of dusty plasma. However, it turned out that photoelectric processes do have a significant impact on dusty plasma. Their manifestations are comparable to similar phenomena observed in near-lunar dusty plasma, despite the Moon being much closer to the Sun.
Мы ожидали, что из-за удалённости Сатурна и Энцелада от Солнца роль солнечного излучения при образовании пылевой плазмы не будет значительной. Однако оказалось, что фотоэлектрические процессы влияют на пылевую плазму достаточно. Их проявления сопоставимы с аналогичными проявлениями в случае окололунной пылевой плазмы, хотя Луна и находится гораздо ближе к Солнцу.
The researchers studied the movement of dusty plasma in the electric field over the satellite and determined the sizes of particles at various altitudes above Enceladus' surface. The sizes of levitating dust particles were found to range from 0.2 to 0.4 micrometres, which exceeds the typical sizes of dust particles observed above the surface of the Moon (about 0.1 micrometres).
Studying plasma contributes to our understanding of how charged particles interact with magnetic fields and with each other, and how structures in outer space form as a result. Learning more about dusty plasma is also valuable for improving the protection and efficiency of spacecraft navigating through dust clouds. The team of scientists intends to continue their research to develop a more detailed model of dusty plasma, as well as a model of the dust cloud near Enceladus.
IQ
Sergey Popel
Professor, Faculty of Physics, HSE University; Head, Laboratory of Dusty Plasma Processes in Space Objects, RAS Space Research Institute