ESA and national disaster response offices recently rehearsed how to react if a threatening space rock is ever discovered to be on a collision course with Earth.
Last month, experts from ESA's Space Situational Awareness (SSA) programme and Europe's national disaster response organisations met for a two-day exercise on what to do if an asteroid is ever found to be heading our way.
In ESA's first-ever asteroid impact exercise, they went through a countdown to an impact, practising steps to be taken if near-Earth objects, or NEOs, of various sizes were detected.
The exercise considered the threat from an imaginary, but plausible, asteroid, initially thought to range in size from 12 m to 38 m – spanning roughly the range between the 2013 Chelyabinsk airburst and the 1908 Tunguska event – and travelling at 12.5 km/s.
Critical times to take action
ESA Space Situational Awareness: detecting space hazards Space Situational Awareness - Near Earth Objects Teams were challenged to decide what should happen at five critical points in time, focused on 30, 26, 5 and 3 days before and 1 hour after impact.
"There are a large number of variables to consider in predicting the effects and damage from any asteroid impact, making simulations such as these very complex," says Detlef Koschny, head of NEO activities in the SSA office.
"These include the size, mass, speed, composition and impact angle. Nonetheless, this shouldn't stop Europe from developing a comprehensive set of measures that could be taken by national civil authorities, which can be general enough to accommodate a range of possible effects.
"The first step is to study NEOs and their impact effects and understand the basic science."
ESA's Optical Ground Station (OGS) is 2400 m above sea level on the volcanic island of Tenerife.
How should Europe react
Participants came from various departments and agencies of the ESA member states Germany and Switzerland, including Germany's Federal Office of Civil Protection and Disaster Assistance.
They studied questions such as: how should Europe react, who would need to know, which information would need to be distributed, and to whom?
"For example, within about three days before a predicted impact, we'd likely have relatively good estimates of the mass, size, composition and impact location," says Gerhard Drolshagen of ESA's NEO team.
"All of these directly affect the type of impact effects, amount of energy to be generated and hence potential reactions that civil authorities could take."