The part of the universe that forms our neighbourhood mostly works like clockwork. This helps astronomers predict the visits of comets, movement of planets, eclipses and tides with an unerring degree of certainty. The same science helps researchers calculate dangers from the sky brought about by objects such as asteroids. One such large rock is widely believed to have pummeled into the Yucatan peninsula in Mexico and wiped away the dinosaurs millions of years ago.
It is unimaginable what would happen if one such big rock collides with Earth today. The probability of an asteroid hitting Earth is 100%. We are, indeed, getting hit every day. Look up on a clear, dark night and you will find a shooting star. Most of these are too small and burn out upon entering Earth’s atmosphere. What matters is the size of the asteroid. The larger it is, the greater is the size of disaster it will cause on the planet.
Astronomers have already catalogued many of these dangerously large objects lurking in Earth’s backyard. The bad news is that we are sitting ducks for asteroid target practice. We already know that very large asteroids, capable of triggering mass extinction of diameters of 1km or more, hit Earth only about every half-a-million years. However, there are many smaller asteroids, and these hit us more often.
In 2013, one 18 meter in diameter asteroid broke up nearly 30 km above the city of Chelyabinsk in Russia and generated a shockwave that shattered glass and injured about 1,200 people. These rocks hit us every 20-30 years. And space rocks of the size that exploded in the sky over the remote forest of Podkamennaya Tunguska River in Siberia, flattening close to 80 million trees on June 30, 1908, pay us a visit once every few hundred years.
According to Nasa astronomers, there are no near-Earth objects (NEO) on collision course with Earth right now. However, there is no assurance that the situation will not change dramatically. The uncertainty arises because NEO orbits are chaotic. Even in a clockwork universe, this makes the behaviour of these rocks uncertain. Suddenly a predicted innocuous asteroid flyby becomes a catastrophic event.
Fortunately, constant refinement of tools and meticulous observation by a dedicated team of researchers from Nasa, the European Space Agency (ESA) and other nations have increased the event prediction time of both fortunate and difficult kinds involving asteroids and other NEOs.
In 2004, asteroid Apophis raised anxiety levels when a group of scientists announced the likelihood of it hitting Earth to be quite high. As always, the media interpreted it as Apophis heading towards us. The NEO had a quiet flyby.
Recently, the possibility of an impact during its close approach in 2029 was excluded by asteroid watchers. But what will happen in the more distant future is less known.
This clear and present danger of a cataclysmic event often gets lost in the din of political and economic crises. The information vacuum gives rise to superstitions, grossly misinterpreted TV news and Hollywood-style exaggeration. The scientific community also needs a voice in the corridors of power to get more attention to this issue.
The answer to the need came from astrophysicist Brian May, more famous as the guitarist of the rock band, Queen. In 2015, May — along with astronaut Rusty Schweickart, filmmaker Grigorij Richters and Danica Remy of the B612 Foundation, a non-profit organisation to protect Earth from asteroids through early detection — created Asteroid Day to educate and raise awareness about asteroids. They selected the date of the Tunguska disaster, June 30, as the Day of Space Rock. Last year, the UN decided to mark the day to spread the knowledge of asteroids.
Every day scientists are adding to our knowledge about asteroids. But the fact remains that there is no plan, secret or otherwise, to stop an asteroid if it comes hurtling towards Earth. There are a few interesting proposals to prevent an impact — ranging from blasting an asteroid to deflect it using a ‘slingshot’ — on the table from Nasa, the European Space Agency and other independent teams. There have been dialogues in the recent past between the US and Europe to fund a couple of these proposals. But nothing has happened. And the clock keeps ticking.
It is a natural disaster that we can predict. With a bit more understanding and experiments, we may even prevent one. But politicians are busy squabbling over other issues impacting funding.
It is true that you cannot see a large asteroid falling from the sky. Sixtysix billion years ago, many of the dinosaurs did not see one coming. They just perished.
