NASA’s recent Dart mission to deflect an asteroid’s path, serves to illustrate just how precarious Earth’s existence is. We are at the mercy of what the Universe throws at us. Our atmosphere and magnetic field serve us well in protecting us from cosmic rays, eruptions of particles and energy from the Sun, and the small meteors that continually bombard us. The presence of large planets like Jupiter and Saturn in our Solar System act as protective big brothers, sweeping up any wayward asteroids that happen to pass by on the way to Earth.
Nevertheless, Earth has suffered a violent past. A quick glance at the Moon in binoculars shows its cratered surface, each crater the result of a strike from space. Earth would look similar, but plate tectonics, erosion, and life on Earth have eliminated most of the evidence of our violent past. However, it is not a matter of ‘if’, but more a matter of ‘when’ the Earth gets struck by a large asteroid again.
65 million years ago, the Earth was hit by a large asteroid that wiped out the dinosaurs. The impact of the city sized asteroid created an 80 km creator, just off the Yucatan Oeninsula in Mexico. The resulting clouds of ash and dust created night-like conditions that persisted for years, if not for decades. Plants died off and entire ecosystems were decimated with most large animals going extinct.
When conditions did improve, evolution took off and created an abundance of plant and subsequent animal life. Who is to say whether humans would have evolved, let alone survived, alongside the dinosaurs and become the dominant species we are today, if the asteroid didn’t impact 65 million years ago.
The Dart mission was a great first step and a proof of concept. We can target and hit a fast moving asteroid. However, In order to truly protect the planet, we have to ensure we find these asteroids well in advance and develop powerful early strike capabilities that can divert the course of asteroids away from the Earth. We will probably find all the larger ones with time to spare, but it is the smaller ones that sneak through that could prove to be problematic.
Hopefully NASA’s planetary defence work will continue and will be on hand to disrupt or destroy the path of any incoming asteroid before it reaches us.