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It turns out that comets also have a part to play in solar system history. Each one has a treasury of clues locked in its ice and dust about conditions in our solar system, particularly when they formed in the protosolar nebula some 4.5 billion (or more) years ago. And if our "home" comets do that, think about what "alien" ones from other planetary systems can tell us about distant places in the galaxy.

Introducing an alien comet

We have a perfect example in Comet 3I/ATLAS, the interstellar intruder that skimmed through the inner solar system between Earth and Mars in 2025. It passed within 1.8 AU of Earth and developed a thick coma (cloud of gas and dust). Astronomers used the James Webb Space Telescope (JWST) and its highly sensitive NIRSpec to study the chemical makeup of that comet and found that it was enriched in the element deuterium. In fact, it contains more than 30 times the amount of deuterium seen in our "home" solar system comets. That tells astronomers quite a bit about conditions where the comet formed in its own home system, how old it is and even a little something about our own solar system.

"This was a unique opportunity to study an ancient object from the distant galaxy, probably predating our sun and solar system," said astrochemist Martin Cordiner of NASA's Goddard Space Flight Center in Greenbelt, Maryland. "On the one hand, we get direct insight into that distant time and place, and on the other, we learn something about how unusual our own solar system may be." Cordiner is first author of the study published in Nature.

Deuterium in a comet

As any comet gets close to a source of heat, it starts to sublimate and "outgas" some of its material. 3I/ATLAS was no different. Its passage between Earth and Mars warmed the ices, and that puffed up a gas coma. The NIRSpec on JWST captured spectra of the light emitted by the coma, and those data were used to determine the ratios of carbon and deuterium in the comet.

Deuterium is a useful element to study. It's an isotope of hydrogen that does not exist well in the presence of heat. Most of what we see in nature was formed in the Big Bang. It can also be formed in stars, but fusion reactions quickly destroy it. Thus, it likes things cold. Once it's exposed to any kind of long-term heating, it gets reprocessed into the hydrogen that makes up water. If you take a sample of water here on Earth (or in any "home built" comet from our system), it has a certain ratio of deuterium to hydrogen. The more hydrogen there is, the less deuterium exists. That's a valuable ratio for figuring out the conditions under which the comet formed.

Nobody has pinpointed the home system of 3I/ATLAS yet, but the high deuterium-to-hydrogen ratio indicates that it very likely formed in a very cold system very early in the history of the Milky Way. Based on its trajectory, some astronomers have suggested that its home system could have been in the thin or thick disk of the Milky Way.

In addition, they suspect it formed at least 10 billion years ago or longer. That was a time when star formation was really kicking off across the galaxy, which provided the comet with its birthplace around a now-ancient star. Its travel through interstellar space has not subjected it to much heating, which is why it still has its high "birth" ratio of deuterium. In other words, it's been in a deep freeze most of its existence.

Carbon fills out the story

Deuterium isn't the only age and chemical tracer that science teams used JWST to study in the alien comet. Isotopes of carbon also provided insight into the comet's past. NIRSpec showed only traces of carbon-13 compared with lighter carbon-12. This also points to a very old origin for 3I/ATLAS. That's because stellar systems become enriched with carbon-13 over time as generations of stars are born and die in the galaxy. When stars die, they lose their carbon (and other elements to space), and eventually that material gets taken up in new generations of stars (and planets). That is why there are higher levels of carbon-13 in our system, around our sun, which formed relatively recently, 4.5 billion years ago.

JWST wasn't the only telescope to study this fascinating comet. ESO's Very Large Telescope looked at the comet and found a carbon and nitrogen compound called cyanide. That's a prebiotic compound involved in the formation of life and indicates that wherever this comet formed, it might have the conditions that could have led to life.

According to team member Stefanie Milam of NASA Goddard, finding such chemicals elsewhere in the galaxy is a rare discovery. "For us as scientists, finding these rare isotopes is fascinating, but the bigger picture here is looking at the possibilities of prebiotic chemistry elsewhere in the galaxy," said Milam of NASA Goddard. "So far, we know of only one place in the vast cosmos where chemical ingredients led to life—our solar system, our Earth. Analysis of these interstellar objects is a major step toward learning how common, or uncommon, the conditions for the evolution of life are in the universe."

Publication details

Martin Cordiner et al, Isotopic evidence for a cold and distant origin of 3I/ATLAS, Nature (2026). DOI: 10.1038/s41586-026-10771-6

Journal information: Nature

Who's behind this story?

Lisa Lock

BA art history, MA material culture. Former museum editor, paramedic, and transplant coordinator. Editing for Science X since 2021. Full profile →

Andrew Zinin

Master's in physics with research experience. Long-time science news enthusiast. Plays key role in Science X's editorial success. Full profile →

Citation: Deuterium in comets tells interesting tales (2026, July 5) retrieved 17 July 2026 from https://phys.org/news/2026-06-deuterium-comets-tales.html

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Scorecard

England's T20 World Cup hopes were crushed as Australia clinched their seventh title with a comprehensive seven-wicket victory at Lord's.

Despite all of England's improvements to this point, their Ashes rivals ensured there would be no first trophy for the hosts since their iconic win on this ground in 2017, as Australia instead delivered an emphatic display of their strength.

England struggled to cut loose in making 150-4 - captain Nat Sciver-Brunt needing 53 balls for 58 - before Australia brutally put that score into context.

After Georgia Voll was bowled by Lauren Bell in the second over, Phoebe Litchfield and Beth Mooney put on a dismissive partnership of 100 in just 67 balls.

By the time Litchfield fell for 48, Australia needed only 34 runs from 42 balls.

Mooney took them within 11 of the finish line in a brilliant 64, before one more piece of England-Australia controversy.

With seven runs needed, Sophie Ecclestone appeared to have taken a clean catch to dismiss Ellyse Perry in the 17th over, but Perry was called back by the TV umpire.

The crowd booed and Ecclestone was incensed but it would have had no impact. The winning runs came when England's spinner bowled five wides in the next over.

The victory margin denied the tournament a competitive finale fitting of the day, with Lord's filled by a capacity crowd in another landmark moment for the women's game.

The occasion is one positive for England, as are the signs of progress they have shown under coach Charlotte Edwards at this tournament, but Australia were ultimately a class above yet again.

Even had Ecclestone's catch been allowed, it would have been too late.

There would be no dramatic fightback, like the one Anya Shrubsole inspired against India in 2017.

Perhaps too timid with the bat, England were unable to counter a pitch that appeared low and slow.

They certainly put in their worst bowling performance of the tournament - a display which was exposed by the class of left-handed duo Litchfield and Mooney.

With England's seamers offering width too often, Australia had matched their boundary count by the 10th over of the chase.

Overhauling Australia was always going to be a huge ask, given the 16-0 margin of England's Ashes defeat last year, when issues with fitness and fielding loomed large.

Those issues have been put to bed as England ended a run of three tournaments in a row without reaching a final.

The first part of their rebuild, one of consolidation and improvement, is done. Now they must close the gap on Australia before the Ashes at home next summer.

England's lack of batting fireworks were summed up by Sciver-Brunt, who hit only five fours. Against South Africa in the semi-final on Thursday she hit 75 runs in 47 balls.

England's captain was again in early - Amy Jones unable to emerge from her slump as she sliced a drive to backward point in the second over for six - but after stroking her first ball for four, Sciver-Brunt never found top gear.

Danni Wyatt-Hodge, who ends as the tournament's leading run-scorer despite defeat, was unfortunate to glove a catch down the leg side off Sutherland in the fifth over for eight.

Early on, England hit the fielders in the deep too often when Australia strayed from their straight lines.

Alice Capsey struck two fours and a six in the ninth over but was bowled attempting a reverse sweep to Molineux in the 10th. When Heather Knight was hit on the pad by a leg-stump half-volley from Kim Garth, England were 70-4 in the 11th.

Freya Kemp timed the ball better than any of her team-mates in making 44 not out from 28. She hit one fine straight six in the last over but England's total always looked below par.

For Australia, who finish the tournament unbeaten, this is an incredible 14th World Cup win across formats, in addition to one Commonwealth Games gold.

After semi-final defeats in the last T20 and 50-over World Cups, they are at the top of the world again.

There has been evolution since their last win in 2023, when Meg Lanning was captain and Alyssa Healy wicketkeeper and opener.

Molineux has steered her team with minimal fuss in their place after doubts over whether she should make their best XI.

For Litchfield and Voll this is also a first World Cup win. In contrast, Perry now has nine to her name and Mooney five.

Mooney, who averages 76.42 in T20 finals, showed class in putting away anything full and cracked away anything short.

England had no answer until it was far too late. %!s()

Race control initially said the safety car would be coming in with one lap to go, setting the scene for a thrilling one-lap dash to the finish, but it then stayed out, meaning the order remained the same until the chequered flag.

After the race, a statement from governing body the FIA said "the 'safety car in this lap' message was displayed erroneously due to a software error".

Silverstone has seen many remarkable races in its long history but this was one of the most extraordinary.

First, championship leader Kimi Antonelli suffered a wheel-fairing failure when he was closing in on the Ferrari for the lead, and seeming set for another win.

As Antonelli dropped down the field, amid a series of increasingly desperate radio messages, Red Bull's Max Verstappen crashed at Stowe while chasing Hamilton for second place.

The safety car for that incident promoted Russell to second place as Mercedes decided not to pit the Briton while everyone else took fresh tyres.

Antonelli crossed the line ninth but was demoted to 16th by a five-second penalty for exceeding track limits - incurred while he was battling with the problems with his car.

Adding to the drama, Hamilton was investigated after the race for a yellow-flag infringement but the stewards gave him a reprimand rather than imposing a penalty.

The result has a major impact on the championship, narrowing Antonelli's lead over Russell to 25 points. Hamilton is seven points further adrift.

Leclerc said he was "so incredibly happy" even though "unfortunately the end was maybe not the one I will have dreamt of".

The key stories of an incident-packed race were:

• A superb drive from Leclerc, deserving of ending a long victory drought for the Monegasque

• Contrasting fortunes at Mercedes changing the face of the title battle

• A rare mistake from Verstappen as he sought an unlikely second place for Red Bull

The race started in front of a record crowd of 175,000 fans with the expectation that Antonelli, imperious through the weekend, would cruise to a comfortable victory from pole position.

Instead, a slow start, caused by over-eager use of the accelerator, meant he was passed by both Ferraris off the line, Leclerc sweeping into the lead on the inside, Hamilton moving into second on the outside.

That set the pattern of the race, Leclerc building a lead over Hamilton, who fought to hold off Antonelli, just as he had for the first nine laps of the sprint on Saturday.

This time, Hamilton held the Mercedes back for one more lap, and Leclerc was 4.4 seconds ahead when Antonelli passed the seven-time champion into Copse on lap 11.

Leclerc stopped for fresh tyres on lap 25, by which time Antonelli was 2.5secs adrift, while Mercedes kept the Italian out for a further 10 laps, aiming to build a tyre offset for the second stint.

When Antonelli rejoined, he started carving chunks out of Leclerc's lead until lap 41, when the Mercedes driver reported a problem with his car.

Antonelli pitted and had fresh tyres fitted, only to find the problem remained when he rejoined the track, and he had to come in again to have the loose brake duct removed, dropping to the back of the points places.

Leclerc now looked locked in for victory, but there was great doubt over second place.

Hamilton, who earlier had a five-second penalty for moving before the lights went out at the start, was 20 seconds back from his team-mate, but Verstappen was closing in and Russell was going with the Dutchman, having dropped back because of a pit stop on lap 34 forced by a slow puncture.

But on lap 48, Verstappen spun off at Stowe. Red Bull team principal Laurent Mekies said the rear wing did not close properly, meaning Verstappen had less downforce as he turned in, causing his loss of control.

Verstappen's off brought out the safety car, and initially it looked as if there would be a short blast to the finish with the Ferrari drivers contesting victory on fresh tyres.

But Russell did not pit, so he would have taken any restart between them, which would have delayed Hamilton's charge, even by a few seconds.

Mercedes decided to leave Russell out because Verstappen had crashed with only four laps to go, and there was doubt about whether the incident would be cleared in time.

As the cars came around to approach the start of the final lap, the timing screen initially said the safety car would pull in, but a few seconds later that message was replaced by another saying it would stay out.

The full post-race FIA statement said: "The safety-car period regulation states that one lap must be completed following the unlapping procedure.

"This process was followed by race operations. The 'safety car in this lap' message was displayed erroneously due to a software error." %!s()

When my husband and I bought the base-trim Challenger from the original owner, it had a lot of miles on the odometer and an unfortunate recent history of sitting under the neighbors' sprinkler. On its roof, where the cracked vinyl top held water against unpainted metal, corrosion was eating tiny pinholes through the steel.

Initially, we weren't even planning on keeping the car. I already had a Challenger. It was a brute of a '72, with a transplanted V-8 and a rattle-can-black paint job that caused curtains to twitch when I parked in L.A.'s nicer neighborhoods. I was perfectly happy with my rat-rod muscle car, but then the '70 came home from the paint shop, glistening blue like a cartoon dolphin. I immediately forswore the dirtbag life, sold the '72, squeezed a 440-cubic-inch big-block under the blue Dodge's hood, and stuck it into service as both daily driver and weekend drag car. I kept it humming, commuting first to a job at a PR firm and later 60 miles round trip to the Hot Rod magazine offices before embarking on various excursions as a freelance writer and a Car and Driver staffer.

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Not only did the Dodge handle transportation duties and quarter-mile runs, but it also did a stint as a prototyping mule for an aftermarket suspension company, made an appearance on American Top Gear, and participated in several magazine dyno tests and photo shoots. I cannot tell you how many burnouts it did, only that one was in front of a police officer who did not find it funny when I said, "Sorry, I didn't see you through all the smoke."

All things return to the earth, and the hot hours on the freeway and steady kick of grit from the racetrack accelerated the Challenger's slide back to jalopydom. The paint cracked along the quarter-panels. The little holes in the roof spread, dimpling under the peeling clear-coat. The scratch in the front fender bled a rusty stain just below the side marker light, a humiliating reminder that I rolled into a post at the gas station one week after getting the car painted the first time. It was looking ragged, and not in a cool patina way.

Having already attempted a quick fix on the roof, I knew that this time it needed a full replacement. Aftermarket body panels are available for first-gen Challengers, so one exorbitant shipping cost later, I had a new roof ready to go to Peter the Swede. Peter, a metalworker friend who specializes in Mopars, is actually Finnish, and I do not know why everyone calls him the Swede, other than a general ignorance of Nordic peoples.

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As is always the case when you bring a project from one craftsperson to another, Peter was unimpressed by the previous bodywork. He texted me daily updates as he excavated layers of unnecessary Bondo and other surprises. The other surprises were rust. Car surprises are always rust, except when they're blown head gaskets. Once Peter had cut out all the rust, next came further disassembly to get the Challenger ready for paint.

One of my favorite things about buying a new (old) car is finding little clues about the previous owner: a collection of national-park maps in the glovebox, a pile of beer-can tabs behind a door panel, seven cloves of garlic tucked in the trunk. Now I got to do the same thing, but with myself. All this sand in the vents? That's from some off-roading when the hairpin at Buttonwillow Raceway proved too hairy. These tangled wires under the dash? A long-ago test of an aftermarket air-fuel meter. This expensive mascara between the seat and the console? Dang, I was looking for that—six years ago.

I pressed another pal into service: Dave Shuten, who normally specializes in high-end customs but agreed to slum it for my Dodge. Twice he came by the house, and twice he rejected our level of disassembly, both times with a crushing "Hey, it's up to you," trailed off with an implied judgment that were it up to him, he'd do better. Finally, the car was deemed stripped and clean enough to drop off at his shop, where it's getting smoothed out and resprayed in bright dolphiny blue. Then I get to put it back together. How hard can that be? I've done it before.

Like a sleeper agent activated late in the game, Elana Scherr didn’t know her calling at a young age. Like many girls, she planned to be a vet-astronaut-artist, and came closest to that last one by attending UCLA art school. She painted images of cars, but did not own one. Elana reluctantly got a driver’s license at age 21 and discovered that she not only loved cars and wanted to drive them, but that other people loved cars and wanted to read about them, which meant somebody had to write about them. Since receiving activation codes, Elana has written for numerous car magazines and websites, covering classics, car culture, technology, motorsports, and new-car reviews. In 2020, she received a Best Feature award from the Motor Press Guild for the C/D story "A Drive through Classic Americana in a Polestar 2."  In 2023, her Car and Driver feature story "In Washington, D.C.'s Secret Carpool Cabal, It's a Daily Slug Fest" was awarded 1st place in the 16th Annual National Arts & Entertainment Journalism Awards by the Los Angeles Press Club.
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