Note: This article concerns a hypothetical asteroid scenario. The information described in this article does not concern a real world event but is based on the practise scenario used at the PDC2015.
The planetary defense conference 2015 has gone through its last day this Friday, and this day was fully dedicated to the conclusion of the PDC2015 impact scenario. During the conference all the experts on planetary defence enacted a scenario in which an asteroid is on collision course with Earth. Using such a scenario the people can learn how political leaders, citizens, and the media would respond in the case of such a threat.
Day 1: An asteroid threat detected
On the first day of the conference the organizing committee presented the following scenario: A Near-Earth Asteroid is predicted to pass very close to the Earth on the 3rd of September 2022. The asteroid (designated 2015 PDC) has a chance of 1 in 110 of hitting the Earth. If the Earth would be hit by the asteroid it would strike somewhere on the corridor shown in the picture: The Middle-East, across South-Asia and the Pacific would all be of risk for the impact.
To discuss this scenario the experts were split in four groups. The first group represents the world leaders of countries that are in the path of the asteroid and are thus directly under risk of an impact. The second group represents all other leaders whose countries are not under direct threat from an impact. The third group are people who are living in the countries at risks and whose homes are under risk of being hit. Finally, the fourth group represents the media and needs to estimate how the media would react on this scenario.
See the day 1 scenario information here: http://neo.jpl.nasa.gov/pdc15/day1.html
Day 2: April 2016, 43% chance of impact
On the second day of the conference the organisation committee presented the participants with an updated scenario. The first day the scenario took place in June 2015, and the impact chance was smaller than a per cent. Now on day 2 the scenario made a jump in time to April 2016. The asteroid had passed through one orbit around the sun and now it could again be observed more closely again, allowing its orbit to be determined better. It however did not bring good news: The new orbit showed that the asteroid now has a 43% chance of hitting Earth! The image given shows the possible location of the asteroid (the red dots) at the possible time of impact.
The reaction of the experts was still one of doubt. As there was still a larger chance that the asteroid would miss the Earth compared to it actually hitting, all parties did not decide to start a deflection mission yet, but all parties did ask for extra information. Everyone wanted to know more about the asteroid and its orbit. More information was however not available as there were no telescopes or spacecraft available to observe the asteroid more closely.
For all the details of day 2, take a look at this site: http://neo.jpl.nasa.gov/pdc15/day2.html
Days 3 and 4: Certain impact, and kinetic impactors on their way
On day 3 and 4 the impact scenario became more definitive when the scenario jumped from December 2016 (day 3) to August 2019 (day 4). The reason for these large time-steps between the subsequent days is that due to the orbit of the asteroid around the Sun, it is not visible all the time. It is often hidden behind the sun from the point of view of the Earth, making it difficult to observe its size and orbit.
On day 3 it was announced that the impact of the asteroid was now a 100% certain. On day 4 the exact impact zone was then released: An impact was expected within the South-China sea. The impact of an asteroid between 150 and 250 meters (as expected in the scenario) would trigger a large tsunami that would impact all the coasts along this sea, hitting China, Vietnam, the Philippines, Malaysia, Brunei, Taiwan, and Indonesia. In total it would put more than 80 million people at risk. To mitigate the threat there are in total six kinetic impactors underway to push the asteroid out of its course so that it will miss Earth.
Within the discussion among the experts it quickly became clear that there was quite a bit of mistrust among the different country leaders concerning the kinetic impactor missions, and also specifically concerning a possible nuclear blast deflection option! The country leaders and the inhabitants of the countries around the South-China-Sea were worried if the kinetic impactors would actually be effective, and if it would be enough to deflect the asteroid. Also countries were suspicious of each other if any of them were developing nuclear deflection options, as they argued that although such a method could be effective against asteroids, it could also be used as a weapon.
For the detailed information provided on day 3, see here: http://neo.jpl.nasa.gov/pdc15/day3.html
And for the details of day 4, take a look at http://neo.jpl.nasa.gov/pdc15/day4.html
Day 5: Kinetic impactors not fully effective!
On day 5, the last day of the conference, the speed of the scenario was ramped up, and a total of three “press-releases” were presented to the participants during the day. The first one was already ominous enough: The date is January the 18th, 2021 (1.5 years before impact) and the kinetic impactors only have had partially effect. The asteroid turned out to be a lose rubble pile, and after the second kinetic impactor hit, the object was broken in two big pieces!
The bigger piece was fortunately pushed away by the impactors and no longer poses a threat to the Earth. The smaller piece however, which is still 60 to 100 metres large, is still on impact course with the Earth. Because of the impactors the orbit of the object is again uncertain, and therefore the impact corridor has widened again (see image above).
Later in the day the scenario progressed further and it ended on August the 27th, 2022, about a month before impact. The impact location had by now been determined to be at one of the worst possible locations: in the middle of Dhaka, the capital city of Bangladesh. Dhaka is the tenth biggest city in the world, with an estimated population of over 20 million in the 2020s. An asteroid of this size in the middle of the city would be disastrous.
The experts suggested that if a nuclear deflection options would still be possible, it should certainly be deployed to try and disintegrate the asteroid before it hit Earth. Furthermore the largest part of the city of Dhaka would need to be evacuated for the expected impact date.
The scenario ended at this point, but it left more then sufficient considerations and food for thought to be considered. Day 5 had a number of different information updates over the day, you can find these at:
Overall the scenario was very useful for the scientists and engineers, mostly because it teaches them what kind of social and civil aspects of a possible meteor strike are of importance: The impact of a NEO would certainly not be of scientific/engineering alone, it would be far more important politically and socially. Through the practice of these scenarios the experts also learn to think from the positions of political leaders, the media, and the public.
Interesting to note was specifically the discussion that arose over whether or not a nuclear deflection option should be developed and deployed. The development of such a device would certainly bring large political consequences with it.
Furthermore there is a large ethical aspect to consider as well: In the scenario the impact would first take place in the South-China-sea. Such an impact in the sea would trigger a large tsunami that would hit the coasts. It is however very difficult to predict how big such a tsunami would be, and how it much damage it would do. To stop the asteroid from hitting the Earth a number of nations developed kinetic impactors that were designed to deflect the asteroid. However they were unfortunately only partially successful, and this meant that a large city was now put at risk instead. Due to the kinetic impactors the people at the South-China-sea were now save, but the people at Dhaka will lose their homes! Are the states who build and launched the kinetic impactors now responsible for this? This is a major ethical question that needs to be looked at and practice scenarios such as this help to develop a proper policy of how to respond in these kinds of situations.