Asteroids are smacking Earth twice as often as before

The team counted 29 craters that were no older than 290 million years

Giant rocks from space are falling from the sky more than they used to, but don’t worry.

For the past 290 million years, large asteroids have been crashing into Earth more than twice as often as they did in the previous 700 million years, according to a new study in Thursday’s journal Science .

But no need to cast a wary glance up. Asteroids still only smack Earth on average every million or few million years, even with the increased crash rate. NASA’s list of potential big space rock crashes shows no pending major threats. The biggest known risk is a 4,200-foot (1.3-km) wide asteroid with a 99.988 per cent chance that it will miss Earth when it whizzes very near here in 861 years.

Tell that to the dinosaurs. Most scientists think dinosaurs and a lot of other species went extinct after a huge space rock crashed into Central America about 65 million years ago.

“It’s just a game of probabilities,” said study lead author Sara Mazrouei, a University of Toronto planetary scientist. “These events are still rare and far between that I’m not too worried about it.”

Mazrouei and colleagues in the United Kingdom and United States compiled a list of impact craters on Earth and the moon that were larger than 12 miles (20 km) wide and came up with the dates of them. It takes a space rock that’s half a mile (800 metres) wide to create holes that big.

The team counted 29 craters that were no older than 290 million years and nine between 291 million years and 650 million years old.

But we can see relatively few big craters on Earth because the planet is more than 70 per cent ocean and past glaciers smoothed out some holes, said University of Toronto planetary scientist Rebecca Ghent, a study co-author.

Extrapolating for what can’t be seen brings the total to about 260 space crashes on Earth in the last 290 million years. Adding in other factors, the science team determined that the current space crash rate is 2.6 times more than the previous 700 million years.

Craters older than 650 million years are mostly wiped off on Earth by glacial forces so the scientists used impact craters on the nearby moon as a stand-in for holes between 650 million and 1 billion years old. The moon is a good guide for estimating Earth crashes, because it is close enough to be in the same bombardment path and its craters last longer.

READ MORE: Cigar-shaped interstellar object could be alien probe, says Harvard study

So what happened nearly 300 million years ago?

“Perhaps an asteroid family was broken up in the asteroid belt,” Mazrouei speculated. The space rocks then headed toward the Earth and moon, and the planet got slightly more because it is a bigger target and it has higher gravity, Ghent said.

Outside scientists are split about the research. Jay Melosh at Purdue said he found the number of craters too small to come to a reasonable conclusion, but Harvard’s Avi Loeb said the case was convincing.

Humans might not have emerged without mass extinctions from space rocks about 250 million and 65 million years ago, Loeb said in an email, adding, “but this enhanced impact rate poses a threat for the next mass extinction event, which we should watch for and attempt to avoid with the aid of technology.”

“This demonstrates how arbitrary and fragile human life is,” Loeb wrote.

___

The Associated Press Health & Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.

Seth Borenstein, The Associated Press


Like us on Facebook and follow us on Twitter.

Just Posted

B.C. BUDGET: Surplus $374 million after bailouts of BC Hydro, ICBC

Growth projected stronger in 2020, Finance Minister Carole James says

Battle of the Bands winner set to perform at Char’s Landing

Sean Lyons is a singer-songwriter originally from Port Alberni

Port Alberni sends large contingent of athletes to Special Olympics Winter Games

Veteran curler Simone Myers dreams of gold in her seventh provincials

Steelhead LNG stops work on Kwispaa LNG project near Bamfield

Huu-ay-aht First Nations ‘deeply disappointed; Steelhead says funding is the problem

West coast group campaigns for seal, sea lion harvest

‘Salmon are going the way of the buffalo unless we do something’

Mermen calendar targets ‘toxic masculinity,’ raises big money for charities

Newfoundland and Labrador Beard and Moustache Club gave a cheque for more than $202,000 to Violence Prevention NL

‘Bullet missed me by an inch’: Man recounts friend’s killing at Kamloops hotel

Penticton man witnessed Summerland resident Rex Gill’s murder in Kamloops

B.C. BUDGET: Income assistance raise still leaves many below poverty line

$50 per month increase included in funding for poverty and homelessness reduction

B.C. BUDGET: Indigenous communities promised billions from gambling

Extended family caregiver pay up 75 per cent to keep kids with relatives

B.C. BUDGET: New benefit increases family tax credits up to 96 per cent

BC Child Opportunity Benefit part of province’s efforts to reduce child poverty

B.C. BUDGET: Carbon tax boosts low-income credits, electric vehicle subsidies

Homeowners can get up to $14,000 for heating, insulation upgrades

B.C. man survives heart attack thanks to Facebook

A Princeton man suffered a heart attack while at an isolated property with no cell service

B.C. man sues Maxime Bernier’s People’s Party over trademark

Satinder Dhillon filed application for trademark same day Maxime Bernier announced the new party

New trial ordered over banning whales, dolphins at Vancouver aquarium

Park board’s appeal reverses previous decision that found it had no right to implement a ban

Most Read