NASA has held a tabletop exercise this week in which planetary defence officials pretend an asteroid is about to hit the Earth in order to see how key players respond.
The hypothetical impact scenario has been run all through this week from April 26 at the 7th International Academy of Astronautics Planetary Defence Conference 2021.
The exercise is being led by NASA's Center for Near Earth Object Studies (CNEOS).
Throughout the week, CNEOS has been releasing new information each day to conference participants, skipping through months at a time as more and more information about the asteroid is "discovered."
At the start of the scenario, a pretend asteroid was "discovered" on April 19 this year, given the fictional name 2021 PDC. Using impact monitoring systems, scientists agreed the impact will take place in six months' time, though the probability was initially 1 in 2,500. By April 26, the chance of impact had been revised upwards to 5 percent. The pretend asteroid 2021 PDC is estimated to be between 35 and 700 meters in size.
There is also a table highlighting possible impact effects, ranging from an in-air explosion that causes no damage to a mass extinction event.
By the next day of the conference, the scenario had skipped forward to May 2021. By this time scientists had calculated the asteroid would certainly hit the Earth and impact somewhere in Europe or Northern Africa.
Still little was known about the size. CNEOS states that there were some mission options left that might hypothetically be available at this point, including launching a nuclear bomb at the asteroid: "Because deflection is impractical, we consider disruption of the asteroid via a nuclear explosive device."
By day 3 of the conference it was late June in the scenario and 2021 PDC's diameter had been estimated using telescope measurements to be 160 meters with an uncertainty of 80 meters either side and its impact area had been narrowed down to a large area of central Europe.
On the last day of the conference the pretend asteroid's size will have been revised down to around 105 meters across. In the imaginary scenario, it will land in the Czech Republic near the border of Germany and Austria with an average impact energy of around 40 Mt, or 40,000,000 tonnes of TNT—the size of a large nuclear bomb. It will damage a region of around 150 kilometers.
Throughout all stages leaders have been requesting feedback for the steps that follow based on the most recent data they have revealed.
The exercise briefing concludes: "Had a more sensitive asteroid survey such as NEOSM or Rubin Observatory (LSST) been in place in 2014, it would almost certainly have detected the scenario object, and the 7-year warning of potential impact would have opened up a host of different possible outcomes."
Lindley Johnson, NASA's planetary defense officer, said in a statement: "Each time we participate in an exercise of this nature, we learn more about who the key players are in a disaster event, and who needs to know what information, and when.
"These exercises ultimately help the planetary defense community communicate with each other and with our governments to ensure we are all coordinated should a potential impact threat be identified in the future."
In real life, NASA is currently planning to launch a spacecraft that will demonstrate the possibility of redirecting an asteroid to adjust its orbit in the event that one were heading towards Earth.
The Double Asteroid Redirection Test, or DART, is due to launch in late 2021 or early 2022. It will arrive at the Didymos binary asteroid system in late September and deliberately crash itself into one of the asteroids at a speed of nearly 7 kilometers per second to measure how the asteroid's path through space changes.