Meteorite impacts leave behind time-capsules of ecosystems

Glass beads that form inside hot meteors as they fall to Earth capture particles from the atmosphere, creating a kind of permanent record of historic climates.

Meteorite impacts can be very destructive. One that fell in Mexico around 66m years ago created a 180km crater and caused the extinction of dinosaurs while spewing debris and molten rock into the air. Now, in what is a fascinating tale of serendipity, researchers have found that these events don’t entirely destroy all traces of life at the site of impact. Molten rocks can capture and preserve organic matter as they cool down to form glass beads.

When a meteor enters Earth’s atmosphere, the air around the meteor gets very quickly compressed causing it to heat up, scorching everything in its path. Most of the time that is where the story ends, as the meteor burns up in the sky as a “shooting star”. But sometimes it is big enough to reach all the way to the surface and transfer its remaining energy to the ground.

This energy is dissipated, as mild earthquakes, sound shockwaves – but mostly as heat. The heat energy can be so great that it melts rocks on the surface and hurls them up in the atmosphere. Anything that comes in contact with this molten rock would presumably get burnt, leaving nothing but rocky material that cools down in the atmosphere, forming glass beads and tektites (gravel-sized natural glass). This is what City University of New York researcher Kieren Howard assumed, but he was able to show that his assumptions were wrong.

For his PhD, Howard was studying the glass beads and tektites found near the Darwin crater in Tasmania. The 1.2km wide crater was created by a meteorite impact about 800,000 years ago.

The natural glass formed during cooling is (as implied by the term glass) not crystalline. Instead of a regular arrangement of atoms, the atoms inside it are randomly arranged. Howard’s analysis, however, kept showing the presence of crystals. At first, he dismissed this as a problem with the machine or with his method of analysis. But when it kept showing up, as a good scientist, he thought he should ask an expert to look at his data.

“This is unusual,” says Chris Jeynes, a physicist at the University of Surrey. “If there were indeed crystals, then it was the result of uneven cooling, which can occur when something gets trapped inside these glass beads.”

Jeynes used proton-beam analysis, a method to peer inside the glass to reveal its elemental make-up. Inside he found carbon. “Howard had no idea what his samples were, and he was very surprised when I told him,” Jeynes says.

The natural glass formed should contain only silicon, titanium, oxygen and other metallic elements in trace amounts. Detection of carbon meant that there was some organic matter inside. The only hypothesis was that, somehow during the formation of these glass beads, they captured organic matter that was floating in the atmosphere. That organic matter might have already been in the air, but it might also include material thrown up by the impact.

Howard then went to another expert to break open these glass beads and reveal what the carbon-rich matter was. It turned out that it included were cellulose, lignin and other biopolymers. This meant that somehow this matter, which originated from plants, had survived the temperature of more than 500°C, which is what the molten rock would have reached before cooling into a glass bead. Usually these temperatures will break down the organic matter, but clearly it didn’t in this case.

Mark Sephton, a geochemist at Imperial College London, was surprised and pleased: “What the results show is that these glass beads can capture an aliquot of the atmosphere of the planet at impact. It is like a time capsule of that ecosystem.” These results are published in Nature Geoscience.

The implications are enormous. It shows that other meteorite impacts, like the one that wiped out the dinosaurs, could have created such time capsules too. Sephton is now working on finding glass beads from other impact sites to reveal information about Earth’s ancient atmosphere.

This method of analysis means that we could also go looking for similar beads on other planets, like Mars, where meteorite impacts are common. They could also reveal vital information about the past atmosphere of those planets. Maybe they captured organic matter – if it ever existed there.

“We would not know any of this if it wasn’t for Howard,” Jeynes says, adding that Howard’s persistence to find out what “the wrong results” led the researchers to a phenomenon that nobody knew existed.

This article was originally published at The Conversation. Read the original article.

The Conversation

Meteor Crater in Arizona. (Photo: Angle Schatz/Flickr)
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Why Twitter is dying, in ten tweets

It's ironic that the most heated discussions of the platform's weaknesses are playing out on the platform itself. 

Twitter has been dying since 2009, and commentators have pre-emptively declared it deceased pretty much every year since. To declare that it's on the downturn has become a bit of a cliché. But that doesn't mean that it isn't also, well, true.

Grumbling among users and commentators has grown to a roar over the past few days, thanks in part to a Buzzfeed report (refuted by Jack Dorsey, Twitter's CEO) claiming the service will move away from a chronological timeline and towards an algorithmic one. Users coined the hashtag #RIPTwitter in response, and, tellingly, many of their complaints spanned beyond the apparently erroneous report. 

They join a clutch of other murmurings, bits of data and suggestions that things are not as they should be in the Twitter aviary. 

Below is one response to the threat of the new timeline, aptly showing that for lots of users, the new feed would have been the straw that broke the tweeters' backs:

Twitter first announced it was considering a new 10,000 character limit in January, but it's yet to be introduced. Reactions so far indicate that no one thinks this is a good idea, as the 140 character limit is so central to Twitter's unique appeal. Other, smaller tweaks – like an edit button – would probably sit much more easily within Twitter's current stable of features, and actually improve user experience: 

While Dorsey completely denied that the change would take place, he then followed up with an ominous suggestion that something would be changing:

"It'll be more real-time than a feed playing out in real time!" probably isn't going to placate users who think the existing feed works just fine. It may be hard to make youself heard on the current timeline, but any kind of wizardry that's going to decide what's "timely" or "live" for you is surely going to discriminate against already alienated users.

I've written before about the common complaint that Twitter is lonely for those with smaller networks. Take this man, who predicts that he'll be even more invisible in Twitter's maelstrom if an algorithm deems him irrelevant: 

What's particularly troubling about Twitter's recent actions is the growing sense that it doesn't "get" its users. This was all but confirmed by a recent string of tweets from Brandon Carpenter, a Twitter employee who tweeted this in response to speculation about new features:

...and then was surprised and shocked when he received abuse from other accounts:

This is particularly ironic because Twitter's approach (or non-approach) to troll accounts and online abusers has made it a target for protest and satire (though last year it did begin to tackle the problem). @TrustySupport, a spoof account, earned hundreds of retweets by mocking Twitter's response to abuse:

Meanwhile, users like Milo Yiannopolous, who regularly incites his followers to abuse and troll individuals (often women and trans people, and most famously as part of G*merg*te), has thrived on Twitter's model and currently enjoys the attentions of almost 160,000 followers. He has boasted about the fact that Twitter could monetise his account to pull itself out of its current financial trough:

The proof of any social media empire's decline, though, is in its number and activity of users. Earlier this month, Business Insider reported that, based on a sample of tweets, tweets per user had fallen by almost 50 per cent since last August. Here's the reporter's tweet about it:

Interestingly, numbers of new users remained roughly the same – which implies not that Twitter can't get new customers, but that it can't keep its current ones engaged and tweeting. 

Most tellingly of all, Twitter has stopped reporting these kinds of numbers publicly, which is why Jim Edwards had to rely on data taken from an API. Another publication followed up Edwards' story with reports that users aren't on the platform enough to generate ad revenue:

The missing piece of the puzzle, and perhaps the one thing keeping Twitter alive, is that its replacement hasn't (yet) surfaced. Commentators obsessed with its declining fortunes still take to Twitter to discuss them, or to share their articles claiming the platform is already dead. It's ironic that the most heated discussions of the platform's weaknesses are playing out on the platform itself. 

For all its faults, and for all they might multiply, Twitter's one advantage is that there's currently no other totally open platform where people can throw their thoughts around in plain, public view. Its greatest threat yet will come not from a new, dodgy feature, but from a new platform – one that can actually compete with it.

Barbara Speed is a technology and digital culture writer at the New Statesman and a staff writer at CityMetric.