London, July 28 (ANI): A new study of ancient rocks in Greenland has suggested that icy comets – not rocky asteroids – launched a dramatic assault on the Earth and moon around 3.85 billion years ago, thus causing the lunar surface to become scarred.
“We can see craters on the moon’s surface with the naked eye, but nobody actually knew what caused them – was it rocks, was it iron, was it ice?” Uffe Grae Jorgensen, an astronomer at the Niels Bohr Institute in Copenhagen, Denmark, told New Scientist.
“It’s exciting to find signs that it was actually ice,” he said.
Evidence suggests that the Earth and moon had both formed around 4.5 billion years ago.
But, almost all the craters on the moon date to a later period, the “Late Heavy Bombardment” 3.8 to 3.9 billion years ago, when around 100 million billion tonnes of rock or ice crashed onto the lunar surface.
To find out whether asteroids or comets were the main culprits for the bombardment, Jorgensen decided to measure levels of the element iridium in ancient terrestrial rocks.
Iridium is rare on the Earth’s surface because almost all of it bound to iron and sank into the Earth’s core soon after the planet had formed. But iridium is relatively common in comets and meteorites.
His team calculated the amount of iridium that asteroids would leave on the Earth and moon compared to comets.
Because comets have more volatile elements and higher impact speeds due to their more elongated orbits around the sun, they would create giant plumes on impact, allowing more iridium to escape into space than during asteroid impacts.
The team predicted that asteroid bombardment would leave iridium levels of 18,000 and 10,000 parts per trillion in rocks on the Earth and moon respectively, while the same figures for comet bombardment would be about 130 and 10.
Ancient moon rocks returned by NASA’s Apollo missions have already confirmed that the lunar iridium levels are 10 parts per trillion or less.
To find out the terrestrial value, Jorgensen’s team sampled some of the world’s oldest rocks from Greenland, aged 3.8 billion years, and asked a Japanese laboratory to assess their iridium levels more accurately than ever before.
They contained iridium levels of 150 parts per trillion, which strongly suggests comets, rather than asteroids, caused the violent bombardment. (ANI)
Sponsored tweets no big deal, for now
Despite Twitter’s announcement that it will finally feature advertisements on its social networking service, several long-time users and commentators have shrugged off any major concern.
Questions had been raised over just how Twitter, a privately-held company which does not report its earnings, will generate revenue to satisfy its investors and justify a $1 billion price tag.
Media sites and a variety of blogs are concerned by the news that advertisers will be able to pay to give their tweets more prominence on search pages.
But with 75 million people using the service, this new advertising platform could be the answer to Twitter’s financial dilemma.
Some users are not impressed with the announcement. As peachymg tweets: “That utopic advertisement-free state in which Twitter has revelled, is now shrivelled. NOT looking forward to the bombardment!”
But Mark Pesce, a social media enthusiast and panellist on the ABC’s New Inventors program, is not too fussed.
“I’ve just seen a promoted tweet. Meh. Will I see any in TweetDeck? Not unless I do searches. Which I do only rarely,” he tweets.
But when it comes to tweets within his own feed, he is not so sure: “When that happens it’ll be annoying.”
JorgeLamen is not as scathing: “I’d prefer if they stayed out of my stream, although I suppose I’d learn to live with it if they were to start showing up in it”.
But the “promoted tweets”, as they are called, will only initially show up as sponsored search results similar to those found on Google.
Eventually they will find their way onto user feeds and will also feature on third-party clients such as TweetDeck and Twhirl.
Jason Wilson, lecturer in digital communications at the University of Wollongong and a regular Twitter user, says although he is not sure that promoted tweets are the definitive answer, Twitter certainly needed to address its lack of a clear business model.
“They had to think of some way to monetise what they’re doing and keep the platform going,” Dr Wilson said.
“The longer things went on without them having some kind of way to make this pay, I’d be more and more concerned that this service just wouldn’t be sustainable over the long-term.”
He says at the very least, he is happy Twitter is trying something to pay for itself.
“I think personally, as a user, I can cope with a sponsored search result when I search for Twitter,” he said.
“I think some people will initially be upset about it… rightly a lot of people see advertising as intrusive and compromising the nature of the services.
“As long as it’s not too intrusive, I think [Twitter] has got the balance right.”
Dr Wilson says that if Twitter continues to play a useful role in people’s lives, most users will not give up on the service.
But if companies soon find their way onto users’ feeds, some might not be as accepting.
Laurel Papworth, who tweets under the name SilkCharm, is an online communities strategist and has collected more than 20,000 followers on Twitter.
She is one of many who are concerned that sponsored tweets will be appearing as the top search result on Twitter pages.
“If they are contextually relevant [it] might be okay. But if they interrupt the flow, [it] could be an issue,” she tweets.
Time will tell just how prominently these promoted tweets will feature on user feeds. One question yet to be answered is just how advertisers will decide who to tweet to.
“At the moment it’s only in search… but later? Like an annoying younger brother – always eavesdropping and interrupting your conversation. Will have to be clever,” SilkCharm tweets.
“I don’t want Woolies offering me Tim Tams every time I tweet I want a cup of tea and a biscuit. Unless they are free…”