Not by Asteroids Alone: ESA Explains the Dangers of Possible Comet Impact

With Asteroid Day looming on the horizon, the European Space Agency has launched a series of tweets that explain the “potentially risky sides” of other type of cosmic wanderers that might, in theory, pose a threat to our planet – comets.

As ESA explains, the biggest threat posed by a comet or an asteroid impact comes from an atmospheric explosion "which occurs before any material touches the ground and creates a shock wave that is responsible for most of the damage".

But while comets are less dense that asteroids and thus "carry less energy" for a given diameter, "most comets are in higher-eccentricity and inclination orbits, resulting in much higher relative velocities with respect to Earth", which, in turn, means that they will have a lot more kinetic energy that asteroids.

​"Therefore, an average comet of a given diameter will likely cause more damage than an average asteroid of the same size", the ESA warns.

​The space agency notes that while no "discovered comet has ever impacted Earth", the same does not necessarily apply to "cometary material", as one theory suggests that the legendary Tunguska event of 1908 was caused by "a comet, mostly made of ice, which did not survive long on the ground".

​"Of course, most meteors are generated by tiny fragments of comets, so in a certain sense they do impact us every year", ESA added.

​Asteroid Day is a global event that was launched in 2014 and is observed annually on 30 June – the anniversary of the Tunguska event.