This week, scientists from around the world were smeared by a fictional asteroid aimed at Earth.
A group of experts from US and European space agencies attended a one-week exercise led by NASA, in which they encountered a hypothetical scenario: An asteroid 35 million miles away was approaching the planet and could hit within six months.
With each passing day of the exercise, participants learned more about the size, trajectory and chance of the asteroid hitting. They then had to collaborate and use their technological knowledge to see if anything could be done to stop the cosmic rock.
The experts failed. The group determined that none of the existing technologies on Earth could stop the hypothetical asteroid from hitting the six-month simulation period. In this alternate reality, the asteroid crashed in Eastern Europe.
As far as we know, no asteroid currently poses a threat to Earth in this way. But approximately two-thirds of asteroids 460 feet or larger ̵
“These exercises ultimately help the planetary defense community communicate with each other and with our governments to ensure that we are all coordinated if a potential threat of future impact is identified,” said Lindley Johnson, a planetary defense officer. NASA in a press release.
6 months is not enough time to prepare for an asteroid strike
The dummy asteroid in the simulation was called 2021PDC. In the NASA scenario, it was “spotted” for the first time on April 19, at which time it is estimated that it achieved 5% of the impact on our planet on October 20, six months after the date of its discovery.
But Day 2 of the exercise shifted to May 2, when new calculations of the impact trajectory showed that 2021PDC would almost certainly hit either Europe or North Africa. Participants in the simulation considered various missions in which a spacecraft could try to destroy the asteroid or divert it from its path.
But they concluded that such missions would not be able to come out of the earth for a short time before the asteroid hit.
“If we are confronted with the hypothetical scenario for 2021PDC in real life, we will not be able to launch any spacecraft with such a short notice with current capabilities,” participants said.
They are also considering trying to blow up or destroy the asteroid using a nuclear explosive device.
“Deploying a nuclear destruction mission can significantly reduce the risk of damage,” they said.
Still, the simulation ruled that the 2021PDC could be 114 feet to half a mile in size, so the chance of a nuclear weapon making a dent is uncertain.
Day 3 of the exercise jumped to June 30, and the future of the Earth looked bleak: the trajectory of the 2021 strike, the PDC, showed that it was heading for Eastern Europe. By day 4, which quickly shifted to a week before the asteroid’s impact, there was a 99% chance that the asteroid would hit near the border between Germany, the Czech Republic and Austria. An explosion would bring as much energy as a large nuclear bomb.
All that could be done was to evacuate the affected regions some time ago.
Most asteroids fly under the radar and many are spotted too late
It is tempting to assume that in the real world, astronomers will notice an asteroid similar to 2021PDC, with much more six months’ notice. But the world’s ability to observe near-Earth objects (NEOs) is terribly incomplete.
Any cosmic rock with an orbit that takes it within 125 million miles of the sun is considered a NEO. However, Johnson said in July that NASA estimated that “we have found only about a third of the population of asteroids that are there that could pose a risk of impact on Earth.”
Of course, humanity hopes to avoid a surprise like the dinosaurs obtained 65 million years ago, when a 6-mile-wide asteroid crashed into Earth. But in recent years, scientists have missed many large, dangerous objects that have approached.
Comet Neowise, 3 miles wide of cosmic ice, passed 64 miles from Earth in July. No one knew the comet existed until NASA’s Space Telescope discovered it was approaching four months earlier.
In 2013, a meteor with a diameter of about 65 feet entered the atmosphere, traveling 40,000 mph. It exploded over Chelyabinsk, Russia, without warning, sending a shock wave that shattered windows and damaged buildings across the region. More than 1,400 people were injured.
And in 2019, the 427-foot-wide killer asteroid flew 45,000 miles from Earth. NASA had almost no warning about this.
This is because currently the only way scientists can track NEOs is to point one of a limited number of powerful telescopes on Earth in the right direction at the right time.
To address this problem, NASA announced two years ago that it would launch a new space telescope dedicated to observing dangerous asteroids. This telescope, called the Near-Earth Observation Mission, along with the European Space Agency’s newly created test bed telescope and the Flyeye telescope under construction in Italy, should eventually increase the number of NEOs we can track.
NASA is testing ways to stop an asteroid
NASA has studied the possibilities that scientists would have if they found a dangerous asteroid in a collision with Earth. These include detonating an explosive device near the space rock, as suggested by the exercise participants, or launching lasers that could heat and evaporate the asteroid enough to change its path.
Another possibility is to send a spacecraft to collide with an approaching asteroid, thus removing it from its trajectory. This is the strategy for which NASA is most serious: Later this year, the agency should launch a test for such technology. The double asteroid diversion test (DART) will send a spacecraft to the asteroid Dimorphos and will hit it purposefully in the fall of 2022.
NASA hopes that the collision will change the orbit of Dimorphos. Although this asteroid does not pose a threat to Earth, the mission can prove that redirecting an asteroid is possible with enough time to complete.