The impact of the asteroid would trigger a tsunami. Photo / 123RF
The impact of the asteroid would trigger a tsunami. Photo / 123RF
A 370-metre-wide asteroid has been orbiting Earth for decades and scientists say the effects could be catastrophic.
A series of very unfortunate events would have to coalesce for it to strike — but if it did you could kiss goodbye to vast swathes of the North American continent, reports href="https://www.news.com.au/technology/science/space/neil-degrasse-tysons-dire-asteroid-tsunami-warning-for-north-america/news-story/92113ce68b4eff36442167605a569016" target="_blank">news.com.au.
The asteroid, named Apophis 99942, has long been classed as a "near-Earth" space rock and briefly caused a panic in December 2004 when scientists estimated there was a 3 per cent chance it could hit Earth in 2029.
But by 2006, after scientists had had some time to properly study the mammoth rock, they realised the asteroid would instead pass through a gravitational keyhole — a small region in space that changes an object's gravity — which pushed the date of Apophis' impact to April 13, 2036.
But a 2036 impact has since been deemed almost impossible with scientists instead eyeing the year 2068 with a tiny one in 150,000 chance of collision.
While Apophis might never hit Earth's surface, prominent astrophysicist and author Neil deGrasse Tyson spoke chillingly about what could happen.
Revealing his research at a university lecture in 2008, Dr Tyson said if the asteroid were to hit Earth, it would cause horrific damage and could potentially wipe out the entire west coast of North America.
"In the era of observing the cosmos with technology, this will be the closest, biggest thing we will ever see," he said.
"The orbit we now have for it is uncertain enough because these things are hard to measure, we cannot tell you exactly where that trajectory will be.
"We know it won't hit Earth, we know it will be closer than the orbiting satellites.
"But there is a 600-mile (965km) zone — we call it the keyhole — and if the asteroid goes through the middle of that it will hit the Earth 13 years later."
Scientists have done further research on the keyhole since Dr Tyson's speech and found the keyhole was instead just over 500m wide, leaving not much space for Apophis to pass through.
Dr Tyson estimated the asteroid would hit 800km west of Santa Monica, a popular, coastal suburb of Los Angeles.
The impact of the asteroid, already sped up by passing through the Earth's atmosphere, would trigger a tsunami.
"If it goes through the centre (of the keyhole), it will plunge down into the Pacific Ocean to a depth of three miles (4km), at which point it explodes, cavitating the Pacific in a hole that's three miles (4km) wide.
"That will send a tsunami wave outwards from that location that is 50 feet (15m) high.
"Oceans don't like having holes in them, so this three-mile-high wall does what? It collapses.
"It falls back into the hole sloshing against itself with such ferocity that it rises high into the atmosphere and falls back down to the ocean, cavitating the ocean again.
"So now you make a cavity a second time. This cycle takes about 50 seconds, you can calculate it."
While Apophis (not pictured) might never hit Earth's surface, Neil deGrasse Tyson spoke chillingly about what could happen. Photo / 123RF
As hundreds of people sat and listened to Dr Tyson's terrifying prediction, he had a final blow for everyone living on the west coast of North America.
"So there you are on the beaches of Malibu and a tsunami comes in," he said.
"Unlike the tsunami in Indonesia, which was one wave that went deep into the shore, this first wave needs a supply of water to exist so that the next wave actually sucks back on it to create itself.
"So, this tsunami will go in only about a quarter of a mile before it gets sucked back out for the next wave to come in. Here's the problem, whatever was there on the coastline is now brought back out to sea and the next tsunami brings it back to the shore.
"All the million-dollar homes in Malibu, they get taken out to the sea and then back. But they're in a slightly different shape.
"So what happens is, all the artificial stuff, all the houses, factories, they get churned into the ablative force that sandblasts the entire west coast of North America clean."
Dr Tyson said the world would know on April 12, 2029 if the asteroid had "threaded the keyhole", leaving North Americans seven years to find a new home.
But despite the terrifying lecture, scientists have since said Apophis passing through the tiny keyhole was near impossible.
In 2008, NASA reaffirmed the chance of Apophis impacting Earth in 2036 as being one in 45,000.
And by February 2014, the odds of an impact on April 12, 2068 were calculated by the JPL Sentry risk table as one in 150,000.
