A team of researchers from the University of Illinois announces the discovery of hot atomic hydrogen atoms in the thermosphere, an upper layer of Earth’s atmosphere. This finding, which the authors report in the journal Nature Communications, significantly changes our current understanding of hydrogen distribution and its interaction with other atmospheric constituents.
Because hydrogen atoms are very light, they easily overcome a planet’s gravitational pull and often escape permanently into interplanetary space. The atmospheric escape of these atoms is one reason why Earth’s « sister planet » Mars once lost the vast majority of its water. In addition, hot hydrogen atoms (which are much hotter than ambient oxygen atoms) play a vital role in the physics governing Earth’s upper atmosphere, and also act as a weather shield from the atmosphere. space protecting our planet and its technology, such as the many satellites in low orbit.
“We know these atoms exist at very high altitudes, above several thousand kilometers”, explains Lara Waldrop, lead author of this study, “but to discover that they exist as low as 250 km is really surprising”.
This result thus suggests that we should review our current models of atmospheric leakage to the thermal structure of the upper atmosphere. “Classical assumptions about higher atmospheric physics did not allow for the presence of hot hydrogen atoms at these heights,” recalls Jianqi Qin, responsible for analyzing the data. « Once we changed our approach to incorporate this assumption, we were able to correctly interpret the data for the first time. » The team also found that the presence of these atoms in the thermosphere significantly affected the distribution of regular hydrogen atoms in the rest of the atmosphere. The question now is where do these atoms come from?
« We know that there must be a source of hot hydrogen atoms, either in the local thermosphere or in the outermost layers of the atmosphere, but we don’t have a solid answer yet, » he said. said Waldrop. « We will continue to work on this puzzle, because knowing the density distribution of these atoms is essential to the investigation of our atmospheric system as well as its response to weather which affects many space technologies that are so important to our modern society.