It’s unlikely to happen, but if a large space object ever hit Earth, the outcome would be calamitous. Humanity needs to start preparing now.
It’s a staple of disaster movies: a huge space rock hurtles towards Earth and the hero gloriously self-sacrifices in a nuclear fireball to save humankind. In reality, saving the planet from an oncoming asteroid will be less action hero and more acting together: countries need to plan well ahead and synchronise their approach to make sure Earth is prepared. But current preparation efforts are scattered and uncoordinated. International Asteroid Day is the perfect time to review how ready humankind is and what more remains to be done.
Near-Earth objects such as asteroids, meteoroids and comets imperil the planet. They have been implicated in previous mass extinctions, including that of the dinosaurs. An object hitting land could produce a crater kilometres across, rattling faraway infrastructure and blanketing the planet in dust, with knock-on effects for the climate. An ocean splashdown could cause a tsunami higher than most buildings just a few hours later.
When space objects hit the Earth’s surface they are called meteorites – and they have arrived within human history. The Kaali meteorite crater formed on the island of Saaremaa, Estonia, several millennia ago. Scientists still debate exactly when the meteorite landed and what its effects were for any humans living there at the time.
Even an object skimming through or breaking up in the atmosphere is dangerous. These objects are called meteors, and they have dangerously impacted Russia at least twice. On 30 June 1908, a still undetermined object blasted Tunguska in Siberia. It incinerated and toppled trees, and caused shockwaves felt dozens of kilometres away. On 15 February 2013 a meteor broke up over Chelyabinsk, shattering glass and setting off car alarms. More than 1,600 people were injured.
Rather than cleaning up afterwards, it would be better to stop space objects from reaching Earth in the first place. The best plan is to deflect the object so it misses Earth entirely. For that, early detection is key. The further away the object is, the less of a nudge it needs: a fraction of a degree change in its course expands over time to become a huge deviation. But the more distant the object, the longer it takes for a deflection measure to reach it. This emphasises the need for early planning.
Possible deflection plans come from science and science fiction. A large water tank could be landed on the object’s surface and then pierced with a small hole. As the water in the tank vents into space it would propel the space object like a rocket engine. More simply, any form of engine could be attached to the object.
Part of the object could be painted black to absorb sunlight. The differential warming of different parts of the surface would create a force altering the object’s path. A laser vaporising part of the object would change its trajectory as well.
Or perhaps a spacecraft could nose or tug the object a fraction of a degree. Explosives including nuclear weapons could be detonated near, rather than on, the object, and the blast’s force would cause a deflection.
Given the uncertainties and harsh conditions of operating in outer space, no plan is failsafe. Many simultaneous actions could be enacted – with collaboration required so they don’t conflict. Each requires years of investment, planning and preparation. Again, that means starting now.
And the option of last resort might indeed be a destructive bomb. At least Earth might then be hit by many smaller chunks rather than a single mammoth.
Careful planning could avoid reaching that stage of desperation, since trade-offs work in our favour. The larger an object and the faster it moves, the more damage it causes, but also the greater the likelihood of early detection – if the skies are monitored.
Comprehensive ground-based scanning for objects costs millions of dollars per year – but space missions can require billions. One estimate for a complete planetary defence system, without much justification or verifiable calculations, was US$15 billion to US$20 billion a year.
Even if all these figures need to be multiplied tenfold, the result is still far less than the US$2 trillion spent each year on declared defence spending. And preventing a meteorite disaster is indisputably far cheaper than the tens of trillions of dollars needed for post-impact rebuilding of several countries.
Even the best monitoring and response system will not prevent every space object from slipping through the net – many thus-far-unobserved types of space objects could exist. But a great deal of knowledge is still not being applied. Current efforts are ad hoc, lack secure funding, and bring the usual plethora of acronyms in their wake.
At the United Nations (UN), the Office for Outer Space Affairs (UNOOSA) is the main space agency, the Office for Disaster Risk Reduction (UNDRR) supports disaster prevention and the Office for Disarmament Affairs (UNODA) promotes peaceful use of outer space. Global groups without formal UN status include the International Asteroid Warning Network (IAWN) – with tasks as per its name – and the Space Mission Planning Advisory Group (SMPAG) for coordinating and acting in case of a threat. The International Astronomical Union (IAU) records and shares information about space objects and their possible trajectories.
Many other governmental and non-governmental initiatives monitor for objects and issue warnings. NASA in the United States has a centre dedicated to calculating object orbits and Earth-collision probabilities. The privately run Spaceguard Centre in the United Kingdom monitors, researches and provides information about dangerous objects.
Global preparedness for a space-object disaster is even less coordinated. In effect, each country or other authority decides for itself how it will address this scenario. Any other entity – business, non-profit organisation, family or individual – must determine for themselves what to be ready for and how.
A large meteorite strike could kill millions and recovery could span generations. Avoiding calamity will be easier and cheaper if humankind works together. Even if they stop just one object, preparation efforts will easily pay for themselves.
Ilan Kelman is Professor of Disasters and Health at University College London, England, and a Professor II at the University of Agder, Kristiansand, Norway. His overall research interest is linking disasters and health, including the integration of climate change into disaster research and health research.
The author declares no conflict of interest.