As a planet-killing asteroid hurtles towards Earth in the film Don’t Look Up, scientists Jennifer Lawrence and Leonardo DiCaprio scramble to get the world to take the threat seriously.
For many, the Netflix hit was an allegory of the world’s inaction on climate change, but now a pair of physicists have taken a more literal view of the question at the heart of the drama: if a 10km-wide asteroid is six months away from impact, is it possible to avert a planet-ending catastrophe?
The answer, from a purely technical perspective, appears to be yes.
“We show that humanity has crossed a technological threshold to prevent us from ‘going the way of the dinosaurs’,” Prof Philip Lubin and Alex Cohen, both physics researchers at the University of California Santa Barbara, conclude in their paper posted this week on the Arxiv database.
The 15-page analysis starts by weighing up the scale of the threat posed by a 10km-wide asteroid, concluding that it would have similar impact energy to the asteroid event that led to the extinction of the dinosaurs 66m years ago.
Allowing such an object to enter the Earth’s atmosphere could, in an extreme scenario, result in staggering atmospheric temperature rises of 300C, destroying virtually all life on Earth.
The merits of different options are considered, with the PI (Pulverize It) method being among those favoured. This would involve an array of penetrators being used to inject nuclear detonators that would split the asteroid into fragments that would either miss Earth entirely (for larger asteroids) or be small enough to burn up in the atmosphere (for asteroids smaller than 1km across). Radioactive fragments hitting the Earth would not be a major concern, the paper said.
The approach would pose political challenges, since testing the detonators before deployment would currently be banned under the nuclear test ban treaty.
“In any realistic scenario of an existential threat, presumably logic would prevail, at least one would hope,” the authors write, perhaps drawing inspiration from the 1979 film, Meteor, in which the United States (Sean Connery) and the then Soviet Union (Natalie Wood) put aside cold war tensions to deal with an incoming asteroid (not a meteor).
The paper also considers the option deployed in the 1999 film, Armageddon, where oil rig workers, Bruce Willis and Ben Affleck, are hired by Nasa to drill into an asteroid the size of Texas and detonate a nuclear bomb to break it into pieces. This is a less realistic scenario, the paper concludes. Such enormous asteroids do exist – Ceres, the first asteroid detected, is nearly this size. However, breaking it in half would require about 10m Gigatons TNT, equivalent to more than 1m times the energy of the Earth’s entire nuclear arsenal.
In the case that attempts to divert or destroy the incoming asteroid fail, the paper suggests that underwater or subterranean bunkers as a last-ditch line of defence. “Taking life underwater or underground would be a wise civil defence-based strategy to assure some survival of the human and other species,” the paper said.
The paper concludes on the optimistic note that averting the existential threat of a large, Earthbound asteroid is just at the limit of our technological capabilities. “Ideally, we would never be in this situation, but better ready than dead.”
The duo are not the first to consider the scenario from a technical perspective. There is an active research community working on planetary defence. The United Nations Office for Outer Space Affairs holds an annual conference on the subject in which experts consider mitigation scenarios, legal issues and how communications might be handled.
However, some were less than enthusiastic about the paper’s premise. Mark McCaughrean, senior adviser for science & exploration at the European Space Agency, described the work as “classic space bubble nerdery”. “Answer the technical question, but completely miss the point of the film, namely that the advice of scientists is routinely ignored,” McCaughrean said on Twitter. “Especially when the real disaster is happening now and in a way that’s too slow and boring for people to care.”