Near-infrared image of the outgassing of Comet Read, obtained by the JWST.
The achievement was obtained after 15 years of attempts.
Astrophysicists led by the University of Maryland, USA, have detected successfully, for the first time, the water degassing on a comet that orbits within the main asteroid belt.
The feat was accomplished using the James Webb Space Telescope (JWST), after fifteen decades of attempts. The spectroscopic detection of water was carried out on Comet Read, which has a circular orbit between those of Mars and Jupiter.
This rare subclass of comets ejects fuzzy-looking icy material, which astronomers believe is produced by sublimation (transition from ice directly to gas). However, until now only ejected dust had been detected there, despite many attempts to detect escaping gases that should also accompany their activity.
Unlike most comets that spend much of their time in the cold outer Solar System, on very elongated orbits, these inner Solar System comets are not expected to have much ice, given their warmer location.
“From the discovery of main belt comets, hWe have collected a large amount of evidence that its activity is produced by sublimation, but until now it has all been indirect.
This new JWST result represents the first direct evidence of sublimation in the form of degassing wateror outgassing of any kind, in a main belt comet, after studies dating back to 2008,” explained Henry Hsieh, who is co-author of the paper.
“Due to than water ice, which is a major component of the volatile material which normally produces activity on ‘classical’ comets in the outer solar system, is unexpected on main belt asteroids, given how close they are to the Sunthere has always been some doubt as to whether the activity of main belt comets is produced by the sublimation of water ice rather than some other process that does not involve ice, such as impacts or material spewed into space by rapidly rotating asteroids.” Hsieh pointed out.
Diagram showing the orbit of Read’s Comet along with the main asteroid belt (shown as a white fuzzy ring in the center of the image) and Halley’s Comet for comparison.
The researchers discovered that Comet Read, and possibly others in the main belt, have a fundamentally different chemical composition than other similar bodies. Particularly, determined that they barely present carbon dioxidea common component in a comet’s outgassing, relative to the amount of water found on it.
“The water in main-belt comets is important, because those asteroids have been thought of as a potential source of water for Earth in the early solar system, and those present-day comets seem to provide an opportunity to test this hypothesis. However, this only works if they do indeed contain water ice,” Hsieh said.
“Confirmation of water outgassing in at least one main belt comet confirms that learning about the origin of Earth’s water from main belt comets is a viable possibility,” he said.
The team used JWST to observe Read shortly after its approach to the Sun, when outgassing was expected to be strongest. He then imaged and spectroscopically observed at near-infrared wavelengths to look for characteristic spectroscopic features of water vapor and other common gases produced by cometary sublimation. The results were published this Monday in Nature.
