Review of the movie “Greenland”, released on pay-per-view ($19.99) or
streaming on Dec. 18, 2020
By Clark R. Chapman
“Greenland” is a high-production-value movie nominally about the onset
of the apocalypse due to an interstellar “comet” (unfortunately, from my
perspective, named Comet Clarke) striking Earth over a period of several
days, as specially selected individuals strive, amid general panic, to get to underground bunkers in Greenland.  As a generic well-acted drama and thriller, some may like it and others may not, but how realistic is the storyline and how bad is the science?  I’m no expert about the politics and sociology depicted by the plot, but I don’t think it is credible that there would exist (e.g. today) a hidden plan to send a few thousand selected people to top-secret bunkers to try to survive an
“Extinction Level Event.”  And I’m sure that Rutgers Prof. Lee Clarke
(there’s that name again!) would disagree that the threatened impact
would generate such widespread panic.  Clarke has written articles about
how panic is a fiction of the media, rather than a realistic way that
people usually react in disasters (he spoke at an NEO impact session a
couple of us arranged for an AAAS meeting two decades ago).
As for the physical science, “Greenland” is rubbish.  A few crudely correct things are said about the difference between comets and asteroids.  But the media headline about Comet Clarke traveling through the Milky Way to strike Earth illustrates the detachment of the script from reality. 
Totally missing from the story is anything remotely real about how astronomers track asteroids/comets and predict an impact. Comet Clarke is pretty huge.  It is a daylight comet (like the Great Comet of 1910 [not Halley]), so would surely have been tracked long beforehand.  It is predicted to strike somewhere in the Atlantic Ocean, but a couple of days later a large piece of it actually strikes – and largely destroys — Tampa, Florida.  During the next couple of days, what must be millions of fragments strike all over planet Earth, creating a dozen >100 km wide craters in the U.S. alone prior to a 15 km wide “fragment” striking Europe, exceeding the K-T impact by several times.  This would be a grossly exaggerated version of the outlandish Firestone et al. hypothesis of what caused the Younger Dryas cooling.
But basically the idea that astronomers would have little or no idea about when and where the “fragments” would strike is simply wrong.  And what caused the wholly unphysical fragmentation of the comet just days before impact is never mentioned in the script.
One episode in the movie repeats a common misunderstanding of meteorite strikes. Someplace in upstate New York, there is a traffic jam as people attempt to get to Canada.  Suddenly there is a local bombardment
of fiery projectiles that rain down, striking the autos, downing a helicopter, setting fires, and so on, like being in the midst of a terrible military attack with Molotov cocktails, grenades, and IEDs.  As we all know, but the movie-makers didn’t, baseball-sized meteorites do not strike the ground as fiery projectiles but rather have been slowed and cooled as they penetrate the lower atmosphere.
There are some striking scenes in “Greenland” such as the rapidly spreading shock waves from the larger impact explosions.  I don’t know how realistic these images are, never having witnessed such an event. But if one suspends one’s disbelief and forgets all about real comets/physics/astronomy/sociology, some viewers might enjoy the 120 minutes of panicked people trying to get to Greenland, or angry that they weren’t chosen, as fiery projectiles explode all around them.
Dr. Clark R. Chapman is Senior Scientist at the Southwest Research Institute’s Boulder, Colorado, Department of Space Studies where his research focuses on asteroids and comets.

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