(The Hill) — An asteroid the size of a football stadium slammed into the needle between Earth and the Moon Saturday morning — the second of two astronomical near-collisions in three days.
In this case, near miss is a relative term: Saturday’s asteroid, 2024 MK, came within 180,000 miles of Earth. Meanwhile, on Thursday, asteroid 2011 UL21 flew within 4 million miles.
But Saturday’s passage of 2024 MK – which scientists discovered just two weeks ago – coincides with a sobering reminder of threats from space.
Sunday is Asteroid Day, the anniversary of the 1908 explosion of a rock from space above a Russian city – the kind of danger that, astronomers warn, still lurks as the Earth rushes into space.
Here’s what you need to know about asteroids, the risk from space and Saturday’s near-miss flyby.
What is an asteroid?
Asteroids are rocks in space that orbit the Sun, much like the planets they occasionally pass by.
Like planets, asteroids formed more than 4.6 billion years ago from the cloud of condensed dust and gas that formed the solar system, making them effectively time capsules from a distant time before the Earth or the Sun formed.
Scientists have identified about 1.3 million of them, most of them orbiting in the vast space between Mars and Jupiter. Individually or collectively, they tend to be small: the total weight of all the asteroids in the solar system is thought to be less than that of the moon.
Throughout long history, asteroid impacts may also have been crucial to life on Earth.
In other asteroid news last week, scientists announced Wednesday the results of a 2023 mission to the asteroid Bennu that returned with samples, suggesting the possibility that it is filled with ingredients for water.
These results suggest an advantage to asteroid impacts. “Asteroids like this may have played a key role in bringing water and the building blocks of life to Earth,” said co-author Nick Timms of Curtin University.
What happens if we hit Earth now?
An asteroid doesn’t have to be particularly large to cause damage. In 2013, for example, an asteroid about 20 meters in diameter that shattered nearly 32 kilometers above Siberia released 30 times more energy than the atomic bomb that hit Hiroshima.
While most of the impact energy was absorbed by the atmosphere, the detonation triggered a shockwave that shattered windows and injured more than a thousand people.
Asteroid Day, Sunday, commemorates an even larger impact, the Tunguska event of 1908, which also occurred over Siberia.
During this event, the Russian newspaper Sibir (Siberia) reported that peasants looking up saw a “strangely bright bluish-white celestial body (impossible to look at), which for 10 minutes moved downward.”
The body appeared to be a cylinder of “pipe,” which began to “stain” as it hit the denser atmosphere above the forest and broke up into black smoke,” the article said.
“A loud bang (not thunder) was heard as if large stones were falling or artillery was firing. All the buildings shook. At the same time, the cloud began to emit flames of uncertain shapes. All the villagers panicked and took to the streets, the women were crying, thinking it was the end of the world.
If 2024 MK, with a diameter of 150 to 240 meters, were to hit Earth rather than pass by it on Saturday, it wouldn’t be the end of the world, at least not quite. Such an impact “would have impact energy equivalent to hundreds of megatons approaching a gigatonne,” Peter Brown of Canada’s Western University told the Canadian Broadcasting Service.
This is a huge potential impact: for context, the explosion would be 10 to 20 times larger than that of most tested hydrogen bombs, which are in the 50 megatons range.
“This is the kind of thing that, if it hit the East Coast of the United States, would have catastrophic consequences for most of the East Coast. But it’s not big enough to affect the entire world,” Brown said.
The impact of a hypothetical collision with 2011 UL21, the asteroid passed by Thursday, would be much more disastrous. Although it was comfortably far out in space and had no chance of hitting Earth, it was also very large: the approximate size of Mount Everest.
With a diameter of 2.4 km, this asteroid was about a quarter the size of the asteroid that hit Earth 65 million years ago, wiping out all the dinosaurs that walked, along with the majority of life on earth.
What is the risk of collision?
Research suggests that number is very, very low. NASA has estimated that a civilization-ending event (such as an asteroid the size of Thursday’s hitting Earth) is likely to occur only every few million years.
And such an impact from an asteroid half a mile in diameter or more will be nearly impossible for a very long time, according to results published last year in The Astronomical Journal.
“This is good news,” Oscar Fuentes-Muñoz, study leader at the University of Colorado Boulder, told the MIT Technology Review. “As far as we know, there will be no impact in the next 1,000 years. »
NASA’s catalog of large and dangerous objects like 2011 UL21 is now 95 percent complete, Technology Review reported.
But as the explosions of 1908 and 2013 suggest, a relatively small asteroid can still “cause a lot of damage”, Áine O’Brien, of the University of Glasgow, warned the Technology Review.
The map of asteroids the size of the one passing between Earth and the moon on Saturday – which could destroy a city if it hit the planet – is still only 40% complete, the magazine reported, according to Big Think.
How do scientists detect and track asteroids?
They do this by continually scanning the sky for relatively small, fast-moving objects. The Asteroid Earth Impact Alert System that detected 2024 MK is one of many surveys looking for risks.
These surveys provide early warnings that could help prevent asteroid impacts, Alan Fitzsimmons of Queen’s University in Northern Ireland told the CBC.
“This is the only natural disaster we can stop. You can’t stop a tsunami, you can’t stop an earthquake, you can’t stop a volcano,” he said. “We can actually stop or prevent an asteroid impact, at least in theory. »
NASA successfully knocked an asteroid off course in 2022, when its Double Asteroid Redirection Test (DART) projected a satellite the approximate weight of a small car onto Dimorphos, a rock about the same size as 2024 MK, slightly modifying its orbit.
The DART mission, which required NASA to execute a precise collision from 7 million miles away, showed “that NASA is trying to be ready for whatever the universe throws at us,” said l Agency Administrator Bill Nelson during a briefing at the time.
But there is an old scientific adage that although in theory there is no difference between theory and practice, in practice there is. Achieving a feat like the DART mission to prevent an asteroid from hitting Earth “is certainly possible, but would be a difficult and expensive task,” astronomer Alistair Gunn of the University of Manchester wrote for the British Broadcasting Corporation.
“The key would be to divert the asteroid from its collision course with Earth rather than breaking it into equally dangerous debris,” Gunn added.
He also stressed that implementing such a plan would take at least five years, which is why early warning is “vitally important”.
This need for early warning is one reason why the 2024 MK passage is so worrisome: scientists discovered it this month.
Earlier this week, NASA announced that its plan to deflect an asteroid still had “high-level deficiencies,” USA Today reported.
“We’re using the capabilities that we have to try to eliminate that danger, to understand what’s going on and to know if something poses a threat,” Kelly Fast, NASA’s acting planetary defense chief, said. media.
Were the Americans able to see Saturday’s asteroid?
Yes, if they are in the right area and are both very prepared and lucky.
Americans in the southwestern United States — or Hawaii — who were plagued by light pollution and wanted to get up before dawn might have a chance to see 2024 MK as a fast-moving dot that will make its closest approach to Earth around 9:46 a.m. Eastern Time.
That’s 90 minutes before dawn in Hawaii and about an hour after dawn on the West Coast — although the asteroid is faintly visible before making its pass.
For anyone outside of these areas, the Virtual Telescope Project is being streamed live during the pass.
Even those in the right area might find it difficult to observe the passage, Queen’s University’s Fitzsimmons told the CBC. Sky observers will need a telescope and be ready to spot a faint, fast-moving object. “You have to know exactly where to look,” he said. It’s an engine. »