spaceSpace and Physics

Large Chunk Of Europe "Annihilated" In NASA's Latest Asteroid Impact Simulation Exercise


Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

clockMay 3 2021, 17:00 UTC
Artist impression of asteroid impact

Artist impression of an asteroid impact. Image Credit: Solarseven/

Every two years, international governmental and space agencies take part in a tabletop scenario as part of the Planetary Defense Conference. In this exercise, a space rock is discovered to be heading toward Earth and members of different agencies have to work out what are the best things to do to try and avoid catastrophe.

In 2019, a daring deflection mission went awry with fatal consequences. An asteroid that was going to impact Denver was shifted towards New York. The Big Apple was razed to the ground. The whole scenario played out over eight fictional years of technology approaches and political disagreements.


For 2021, the scenario selected had a completely different sense of urgency. The asteroid discovered was going to impact in just six months. On the first of the conferences, members of these agencies find themselves with the report of a fictional asteroid called 2021 PDC approaching our planet with a five percent chance of hitting us on October 20, 2021.

There are many uncertainties at first. We don’t know if it will hit (but come on it’s a tabletop exercise of course it will hit), where, and how big it is. First estimates, based on a fake week of studies, suggests a body between 35 meters (115 feet) but maybe as large as 700 meters (2300 feet).

The Asteroid Impact Simulation Day By Day

The first day has the teams looking at what can be done and how serious the situation is. International groups are called to weigh in on a possible deflection mission. With a week more of observations, astronomers believe that they can have a better idea if it’s going to hit or not. Currently, the target area extends to two-thirds of the planet, South-East Asia, Australasia, and Antarctica are safe.

Day Two starts after this hypothetical week. In such a brief amount of time, astronomers have been tracking almost constantly and it is certain that it will impact. The team also knows that it will end up somewhere in either Europe or North Africa. This was possible because the asteroid was actually caught in previous observations but not actually recognized as such.

Fictional impact area from 2021 PDC
Fictional impact area from 2021 PDC just two weeks after discovery. NASA/JPL-Caltech/Paul Chodas/CNEOS

The second day also sees a detailed look at what missions could be sent to deflect such an asteroid. And it’s not good news. The asteroid is too close and too fast (and possibly too big) for a course correction. So you ought to hit it hard. Either a nuclear weapon, among the biggest, ever assembled during the Cold War, or shooting like dozens of rockets at it. With the risk that it would fragment and still crash into Earth.

“If confronted with the 2021 PDC hypothetical scenario in real life we would not be able to launch any spacecraft on such short notice with current capabilities,” members of the group stated.

Day three takes place on June 30. Months of observation have allowed the team to narrow down the size and likely location of impact. It is estimated to be between 35 and 500 meters and land somewhere between Germany, Czech Republic, Austria, Slovenia, and Croatia. Up to 6.6 million people could be affected. Too many things are still uncertain and the consequences could be minor structural damage if the object were to burn up high in the atmosphere to an unsurvivable level of devastation. However, it remains uncertain. 

Fictional impact area from 2021 PDC
Fictional impact area from 2021 PDC just days before impact. NASA/JPL-Caltech/Paul Chodas/CNEOS

The final day takes place on October 14, 2021. The last six months of observations have allowed researchers to reduce the size of the object to 105 meters with a ten percent uncertainty and the likely impact location to a region at the border of the Czech Republic, Germany, and Austria.


But even then, our lack of knowledge leaves us with so much uncertainty on the potential energy of the impact and the size of the devastation that it might leave in its wake.

This image shows the full range of regions potentially at risk to local ground damage from all modeled cases (shaded regions). The line contours correspond to the average damage risk ca
The possible range of destruction in the region that would be impacted in the simulation. NASA/JPL-Caltech/Paul Chodas/CNEOS

Today We Are Not Ready. Maybe, Tomorrow

Over the years, these simulations have shown what we are doing well and what we are doing not so well, and where we are dangerously unprepared. Many aspects of the 2021 Planetary Defense Conference fall in the latter category.

The briefs show that if such an object were to be discovered today or tomorrow, we would struggle to protect the planet. In 2019, a 100-meter (330-foot) long asteroid called 2019 OK was only discovered one month before it passed 72,500 kilometers (45,000 miles) from our planet.

Observatories such as the Vera Rubin, and many others, will help to discover more of these objects (if they are not too affected by satellites megaconstellations like Starlinks) but more is needed to keep our planet safe. The simulation actually points out that if the Rubin Observatory had been online in 2014, it would have spotted the fictional 2021 PDC.


The chances of a truly dangerous asteroid hitting our planet remain astronomically low but when it comes to the risk they pose, we ought to be prepared. And we are not. 


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