Scientists around the world have been bamboo this week by a fictitious asteroid heading for Earth.
A group of experts from American and European space organizations participated in a week-long exercise led by NASA, where they faced a hypothetical scenario: An asteroid that was 35 million miles away approached the planet and could hit within six months.
For each day that followed the exercise, participants learned more about the size, orbit, and chance of impact of the asteroid. Then they had to collaborate and use their technological knowledge to see if anything could be done to stop the space rock.
The experts came under. The group decided that none of the Earth’s existing technologies could prevent the hypothetical asteroid from hitting given the six-month simulation period. In this alternative reality, the asteroid crashed into Eastern Europe.
As far as we know, no asteroids currently pose a threat to Earth in this way. But an estimated two-thirds of the asteroids are 460 feet in size or larger – large enough to wreak havoc – remain undetected. Therefore, NASA and other agencies are trying to prepare for such a situation.
“These exercises will ultimately help the planetary defense community communicate with each other and with our governments to ensure that we are all coordinated if a potential impact threat is identified in the future,” Lindley Johnson, NASA’s planetary defense officer, said in a press release.
6 months is not enough time to prepare for an asteroid impact
The fictitious asteroid in the simulation was called 2021PDC. In NASA’s scenario, it was first “spotted” on April 19, and after a week, scientists were able to calculate that it had 5% of hitting our planet on October 20, six months after its discovery date.
But day 2 of the exercise quickly wound up until May 2, as new impact trajectory calculations showed that the 2021PDC would almost certainly hit either Europe or northern Africa. Participants in the simulation considered various missions where spacecraft could attempt to destroy the asteroid or divert it from its path.
But they concluded that such missions would not be able to get off in the short time before the asteroid was affected.
“If we are confronted with the hypothetical 2021PDC scenario in real life, we would not be able to launch any spacecraft at such short notice with current capabilities,” participants said.
They also considered trying to detonate or disrupt the asteroid using a nuclear explosive device.
“Implementing a nuclear disruption mission could significantly reduce the risk of shock damage,” they found.
Still, the simulation prescribed that the 2021PDC could be anywhere from 114 feet to half a mile in size, so the chance that a nuke could make a dent was uncertain.
Day 3 of the exercise ran until June 30, and the Earth’s future looked bleak: 2021PDC’s battlefield showed that it was heading for Eastern Europe. On day 4, which was fast until a week before the asteroid effect, there was a 99% chance that the asteroid would hit near the border between Germany, the Czech Republic and Austria. The explosion would bring as much energy as a large atomic bomb.
All that could be done was to evacuate the affected regions in advance.
Most asteroids fly under the radar and many are seen too late
It is tempting to assume that real world astronomers will spot an asteroid similar to 2021PDC with much more notice than six months. But the world’s ability to monitor near-Earth objects (NEOs) is sadly incomplete.
Any space rock with an orbit that takes it within 125 million miles of the sun is considered a NEO. But Johnson said in July that NASA believes that “we have only found about a third of the population of asteroids out there that could pose a danger of shock on Earth.”
Of course, humanity hopes to avoid a surprise that the dinosaurs got 65 million years ago when a 6 km wide asteroid crashed to Earth. But in recent years, researchers have missed lots of large, dangerous objects that came close.
Comet Neowise, a 3 km wide chunk of ice, passed within 64 million miles of Earth in July. No one knew the comet existed until a NASA space telescope discovered it was approaching four months earlier.
In 2013, a meteor about 65 feet in diameter entered the atmosphere, driving 40,000 mph. It exploded over Chelyabinsk, Russia without warning, sending out a shock wave that shattered windows and damaged buildings throughout the region. More than 1,400 people were injured.
And in 2019, a 427-foot-wide, “city-killer” asteroid flew within 45,000 miles of Earth. NASA had almost no warning about it.
This is because at the moment, the only way scientists can track a NEO is by pointing one of Earth’s limited number of powerful telescopes in the right direction at the right time.
To solve this problem, NASA announced two years ago that it would launch a new space telescope dedicated to looking for dangerous asteroids. The telescope, called the Near-Earth Object Surveillance Mission, together with the European Space Agency’s recently launched Test-Bed Telescope and Flyeye Telescope, being built in Italy, should ultimately strengthen the number of NEOs we can track.
NASA is testing ways to prevent an asteroid
NASA has studied the possibilities scientists would have if they were to find a dangerous asteroid on a collision course with Earth. These include detonating an explosive device near the space rock suggested by the participants, or firing lasers that could heat up and vaporize the asteroid enough to change its path.
Another option is to send a spacecraft up to slam into an oncoming asteroid and thereby strike it from its orbit. This is the strategy that NASA is most serious about: Later this year, the agency plans to launch a test of such technology. The Double Asteroid Redirection Test (DART) sends a spacecraft to the asteroid Dimorphos and hits it purposefully in the fall of 2022.
NASA hopes the collision will change Dimorphos’ orbit. While this asteroid is not a threat to Earth, the mission can prove that diversion of an asteroid is possible with sufficient lead time.
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