The James Webb Space Telescope has detected water around a rare comet located in the main asteroid belt between Jupiter and Mars.
The observation represents another scientific breakthrough for the James Webb Space Telescope (JWST), marking the first time that gas, in this case water vapor, has been detected around a comet in the main asteroid belt. This is important because it shows that water in the early solar system could have been preserved as ice in the main asteroid belt.
“In the past, we’ve seen objects in the main belt with all the characteristics of comets, but only with this precise spectroscopic data from JWST can we say ‘yes,’ it’s definitely the water ice that’s creating this effect,” University of Maryland astronomer Michael Kelly said. who led this research, in a statement (Opens in a new tab). “Through JWST’s observations of Comet Read, we can now demonstrate that water ice from the early solar system could be preserved in the asteroid belt.”
The discovery of water vapor around comet 238P/Read could significantly bolster theories that water, a vital ingredient for life, was delivered to our planet from space by comets. But studying the comet also presented a conundrum: carbon dioxide, which astronomers had expected to see, is missing from comet 238P/Reed.
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The apparent lack of carbon dioxide around comet 238P/Read surprised the team more than the discovery of water vapor, since this compound was previously calculated to make up up to 10% of the volatile matter in easily-boiled comets. by the sun.
The team said there are two possible reasons behind Comet 238P/Read’s loss of carbon dioxide. First, the comet may have contained carbon dioxide during its formation, which it lost due to warming by the Sun.
“Being in the asteroid belt for a long time could do that – carbon dioxide evaporates more easily than water ice and can seep out over billions of years,” Kelly said.
An alternative theory for the carbon dioxide deficiency is that this main comet belt may have formed in a region of the solar system devoid of the compound.
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As its name suggests, the main asteroid belt is primarily home to rocky bodies like asteroids. However, it also hosts the occasional comet-like object such as Comet 238P/Read. These cometary objects can be identified by the fact that they periodically light up as a halo of material, or coma, that surrounds them. They can also develop a tail of matter that is characteristic of comets.
The comet’s coma and tail come from solid icy material, which turns directly into gas through a process called sublimation when comets come close to the Sun and heat up. This sublimation is why astronomers assume all comets come from the Kuiper Belt far beyond Neptune, or the Oort Cloud, which is believed to be at the edge of the solar system. Both locations for water ice in these bodies would provide protection from solar radiation, allowing it to be preserved, while a location closer to the Sun near Mars might not.
The classification of a “main belt comet” is fairly new, and comet 238P/Read was one of three objects that helped form the family of near-Earth comets. Astronomers weren’t clear if these icy bodies could also be clinging to frozen water. This is the first hard evidence that they can.
Observing the comet in such detail is a remarkable achievement for the powerful space telescope, and marks the first time gas has been confirmed in a main belt comet.
“Our world full of water, full of life and unique in the universe as far as we know, is something of a mystery — we’re not sure how all that water got here,” research co-author and Webb’s deputy project scientist for Planetary Sciences Stephanie Milam said in the release. “Understanding the history of water distribution in the solar system will help us understand other planetary systems and whether they are on their way to hosting an Earth-like planet.”
The team will now aim to look beyond Comet 238P/Read to discover if similar rare comets have similar compositions. This may include more observations with JWST and other telescopes and on-site missions that could already collect samples from main belt comets.
“These asteroid belt objects are small and faint, and with JWST we can finally see what’s going on with them and draw some conclusions,” said Heidi Hamill, co-author and astronomer at Universities in Research Astronomy (AURA). “Do other main belt comets also lack carbon dioxide? Either way, it will be exciting to find out.”
The team’s research is published in the journal nature (Opens in a new tab).
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