NASA baffled by doomsday asteroid
An enormous asteroid that could one day hit Earth in a devastating impact is mysteriously spitting out rocks.
So-called "doomsday" asteroid Bennu is ejecting metre-sized "particles" into space - and NASA is baffled.
Bennu has achieved infamy after being declared a "hazardous object" by astronomers.
The 487-metre asteroid could smash into Earth on several different dates in an event akin to all-out nuclear war.
Late last year's NASA's OSIRIS-REx probe arrived at Bennu and began circling it, relaying images and data to space scientists.
And researchers made an unexpected discovery: Bennu was occasionally "discharging" large chunks of material into space.
These particles then either briefly orbited Bennu and fell back onto its surface - or escaped into space.
"No one has ever seen an active asteroid up close like this," said Carl Hergenrother, an astronomer at the University of Arizona, speaking to Wired.
"It wasn't that long ago that the conventional wisdom was that asteroids are these dead bodies that didn't change very much."
Some of the chunks of material were travelling at more than three metres per second and were blasted out during "ejection events".
The largest of these events took place on January 6 and ejected 200 separate chunks.
"Among Bennu's many surprises, the particle ejections sparked our curiosity, and we've spent the last several months investigating this mystery," said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson.
"This is a great opportunity to expand our knowledge of how asteroids behave."
Scientists have several theories about what could be causing the ejection events.
It's possible that meteoroids are striking Bennu, blasting material up into space.
Thermal stress fracturing - where a change from cold to warm temperatures during the day creates rifts - could also be sparking ejections.
And the release of water vapour sending particles flying is the third theory being discussed.
"It could be that more than one of these possible mechanisms are at play," said Steve Chesley, an author on the paper and senior research scientist at NASA's Jet Propulsion Laboratory in Pasadena, California.
"For example, thermal fracturing could be chopping the surface material into small pieces, making it far easier for meteoroid impacts to launch pebbles into space."
Further examinations should reveal the truth.
Importantly, the OSIRIS-REx probe is also due to land on Bennu in 2023 to scoop up samples ahead of its return to Earth.
The other good news is that although Bennu could hit us, it's unlikely.
"The possibility of Bennu hitting Earth is very low (1 in 3000), and if it does, it will be in 150-200 years time," said Dr Robin Smith, a physicist at Sheffield Hallam University, speaking to The Sun earlier this year.
And by then, it's possible that we'll have put into place a sci-fi asteroid-blasting weapon to save us from certain doom.
However, an impact by Bennu would be devastating for Earth if it happened.
Astrophysicists recently revealed to The Sun what it would feel like for blitzed onlookers watching the 487-metre rock's impact from around the world.
The asteroid would hit Earth "with almost the same speed as in space - 27km/s (97,200km/h)", said Dr Martin Archer.
He's a space physicist at the Queen Mary University London and has told The Sun exactly how destructive Bennu's impact could be.
"The crater would be eight kilometres wide and 600 metres deep," Dr Archer explained.
And he warned that the scale of destruction would be staggering, akin to all-out nuclear war.
For anyone within a 1600-metre radius of the impact, it's game over.
"You'd probably be vaporised," sad Dr Archer.
"Or at least flung into the air at immense speed."
All the experts that we spoke to agreed that it would be similar to a major nuclear attack.
You would be killed instantly - before you even knew what was happening.
"You will get little warning and will be vaporised, like sitting at ground zero of a large nuke. Nothing will survive," Dr David L Clements, of Imperial College London, told The Sun.
"If it hit London then it's goodbye to London and everything and everyone in it and significant damage to anything closer than Birmingham.
"The impact of Bennu hitting the Earth would be the equivalent of a very large nuclear bomb going off," he added.
The situation isn't much cheerier 16 kilometres away from the impact either.
The asteroid strike will create so much heat that you and everything around you will be enveloped in flames.
"You'll be incinerated by the thermal flash from a fireball 275 times brighter than the sun," said Dr Clements.
"Clothing, wood, trees, grass ignite and you'll suffer third-degree burning from the flash before the ignited fires get you. It will be a firestorm.
"The blast will destroy pretty much all buildings, and 90 per cent of trees will be blown down.
"The blast arrives about 50 seconds after the flash, so everything will be on fire already."
What if you're 160 kilometres from the impact site? That's about the distance from Sydney to Newcastle.
Well, the air will be so hot - and moving at hundreds of kilometres an hour - that you're still at risk from third-degree burns.
Dr Archer says you'd see an eight kilometre-wide fireball that looks "five times bigger than the sun" for about a minute.
Next you'd feel a magnitude 7 earthquake around 30 seconds after impact.
After three minutes, you'd be hit by a dusting of ejected rock.
"And eight minutes later, you'd be hit by a sound about as loud as heavy traffic that could shatter windows," Dr Archer said.
And if that doesn't get you, superheated rocks falling from space could crush you.
Or simply burn you alive.
This article originally appeared on The Sun and was reproduced with permission