The small asteroid will enter Earth’s atmosphere at 19 km/s (43,000 mph) on April 29, 2027, producing a large fireball or “megabolide,” and predicted to release 5-20 megatons of energy in the airburst. Scientists on the ground now know that the asteroid is headed towards New York City. Today, on Day 5 of the exercise, we’ve jumped ahead in time to 10 days from impact. “You don’t learn anything if you don’t study the worst possible case each day.” “We need to challenge ourselves and ask the tough questions,” Chodas said.

But that’s not the point of an exercise like this, he said. More likely, any asteroid heading towards a certain Earth impact would end up in an ocean. He stressed that no one at the conference believes that this exact scenario would play out this way in real life. “Each day we ask, what if?” said Paul Chodas, the creator of this week’s scenario and the director of the Center for Near Earth Object Studies at NASA’s Jet Propulsion Laboratory in Pasadena, California. The kinetic impactors hit the asteroid…but ended up splitting off a chunk, which, on Day 4 (four years from impact), again was headed towards Earth. Once they found out it was on a certain collision, NASA and space agencies around the world decided to send a fleet of kinetic impactors to deflect the asteroid. Every day, the audience heard updates - at one point, they weren’t sure whether the 140-260-meter-wide (500-850 feet) asteroid was actually going to hit Earth. This week at the 2019 Planetary Defense Conference, conference participants were tasked with responding to a hypothetical asteroid impact scenario in which they have eight years to stop an asteroid on a collision course with Earth. Currently, there is no known asteroid with a significant probability of impacting Earth in the next century. This scenario is designed to help key decision makers practice for a real asteroid impact. Each day this week, we will be providing updates on a fictional impact scenario playing out at the International Planetary Science Conference in College Park, Maryland.

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