James Webb investigates mystery of where Earth’s water comes from

By Georgina Torbet Published May 18, 2023

As wild as it might sound, scientists have a theory that water on Earth didn’t actually originate here: the first water may have been brought to our planet by a comet. To understand whether that is the case, astronomers look to the comets commonly found in the asteroid belt between Mars and Jupiter, and recent research using the James Webb Space Telescope has identified a clue in this long-standing mystery.

Researchers used Webb’s Near-Infrared Spectrograph instrument to look at the composition of a comet in the asteroid belt, and they found evidence of water vapor around a comet in this area for the first time. Looking at Comet 238P/Read showed nearby vapor, supporting the idea that water could be carried by such a comet. While many comets come from more distant locations like the far-off Oort cloud, which is a long way from the sun where it is easier for water ice to survive, this particular comet hangs out in the main asteroid belt.

This illustration of Comet 238P/Read shows the main belt comet sublimating—its water ice vaporizing as its orbit approaches the Sun. This is significant, as the sublimation is what distinguishes comets from asteroids, creating their distinctive tail and hazy halo, or coma. It is especially important for Comet Read, as it is one of 16 identified main belt comets found in the asteroid belt, as opposed to the colder Kuiper Belt or Oort Cloud, more distant from the Sun. Comet Read was one of three comets used to define the class of main belt comets in 2006. — This illustration of Comet 238P/Read shows the main belt comet sublimating—its water ice vaporizing as its orbit approaches the Sun. This is significant, as the sublimation is what distinguishes comets from asteroids, creating their distinctive tail and hazy halo, or coma. It is especially important for Comet Read, as it is one of 16 identified main-belt comets found in the asteroid belt, as opposed to the colder Kuiper Belt or Oort Cloud, more distant from the Sun. NASA, ESA

That helps astronomers understand how water could have arrived on Earth. “Our water-soaked world, teeming with life and unique in the universe as far as we know, is something of a mystery – we’re not sure how all this water got here,” explained one of the researchers, Stefanie Milam, in a statement. “Understanding the history of water distribution in the solar system will help us to understand other planetary systems, and if they could be on their way to hosting an Earth-like planet.”

Recommended Videos

“With Webb’s observations of Comet Read, we can now demonstrate that water ice from the early solar system can be preserved in the asteroid belt,” said fellow researchers Michael Kelly.

However, there was something odd about the data from this comet. While the results showed water vapor was present, there wasn’t any carbon dioxide detected, which had been expected. Comets usually carry around 10% carbon dioxide, so it’s odd not to find any. It might be that the comet formed in an unusually warm area where carbon dioxide wasn’t present, or it could be that the comet used to have carbon dioxide but lost it over time as it warmed.

To find out more, the researchers want to look at more comets in the asteroid belt to see if they have similar compositions — something that is now possible thanks to Webb’s powerful instruments.

“These objects in the asteroid belt are small and faint, and with Webb, we can finally see what is going on with them and draw some conclusions. Do other main belt comets also lack carbon dioxide? Either way, it will be exciting to find out,” said co-author Heidi Hammel.

The research is published in the journal Nature.

Georgina Torbet

Former Space Writer

Georgina has been the space writer at Digital Trends space writer for six years, covering human space exploration, planetary…

Topics

Space

Starship is finally going orbital, and SpaceX has picked September 22

Flight 14 is aiming for orbit, Starlink V3 deployment and a very long day in space.

Starship rocket.

SpaceX is finally ready to give Starship its biggest test yet. The company says the massive rocket's 14th test flight is scheduled for September 22, when it will attempt to put the upper stage into Earth orbit for the first time. The launch is currently pending regulatory approval, with a 75-minute window opening at 7:15 a.m. CT.

Starship has 26 Starlink satellites to deliver

Space

Want a city on the Moon? Scientists say there’s not enough water

A billion tons still comes up short

Artist impression of activities in a Moon Base.

For decades, humanity has looked up at the Moon and wondered what it would be like to live on it. Think sprawling cities, factories, research centers, and permanent human settlements. Unfortunately, there is one fairly fundamental problem with that vision.

A new study published in Frontiers in Space Technologies argues that even the Moon's potentially enormous reserves of frozen water may be nowhere near enough to support city-sized populations sustainably. Researchers Martin Elvis and Jonathan McDowell estimate that the permanently shadowed regions near the lunar poles could contain roughly one billion tons of water. It sounds like an extraordinary amount until you put a million thirsty humans next to it.

Space

NASA’s new telescope can see 100 times more sky than Hubble in a single shot

NASA just launched a $4 billion telescope to map billions of galaxies

NASA Roman Telescope Launch Featured

The Hubble telescope has an almost legendary status. Over the last three decades, Hubble gave us some of the most spectacular close-ups of the universe ever captured, and now, NASA’s newest space telescope wants to see the bigger picture. The Nancy Grace Roman Space Telescope successfully launched aboard a SpaceX Falcon Heavy from Kennedy Space Center in Florida at 7:26 a.m. EDT on August 30. Roman is now beginning a roughly three-month journey toward the Sun-Earth L2 point, nearly a million miles away, where it will spend its primary five-year mission surveying huge portions of the cosmos.

Roman carries a 2.4-meter primary mirror, the same diameter as Hubble’s, but its Wide Field Instrument can capture a field of view at least 100 times larger than Hubble’s. NASA expects it to use that combination of sharpness and scale to map billions of galaxies, study dark matter and dark energy, and discover enormous numbers of previously unknown worlds.