This 25-year-old sci-fi disaster movie is still lauded by scientists — here's why

In anticipation of the 25-year-anniversary of "Deep Impact," Dr. Clark R. Chapman and his wife Y Chapman decided to rewatch the classic sci-fi disaster flick. Dr. Chapman is uniquely qualified to assess the movie's merits: "Deep Impact" is about a comet the size of Mount Everest that is heading on a collision course with Earth, and Chapman is a planetary scientist for the B612 Foundation, a nonprofit which protects Earth from comets, asteroids and other near-Earth Objects (NEOs).

Perhaps unusual for a big-budget sci-fi flick, Dr. Chapman strongly approved of the film's science, and both he and Y — an environmental activist and artist who donates to the B612 Foundation — said that as a work of art they "highly rate the movie's production and creativity. It treats a number of characters in sufficiently intimate detail that viewers get to 'know' them."

The Chapmans are far from alone when it comes to scientists and artists who respect "Deep Impact," although usually praise has been reserved for its scientific merits. Then again, any kind of long-term high regard for "Deep Impact" seemed improbable when it was first released in 1998, when most critics mocked the film's attempts to engage in thoughtful character studies. While some scientists and journalists stepped forward to offer more nuanced takes, the consensus view was to dismiss "Deep Impact" as little more than a melodramatic companion piece to "Armageddon," a Michael Bay-directed, jock-minded asteroid movie that was released two months later (and which critics similarly savaged).

"Deep Impact," which was released on May 8, 1998, was directed by Mimi Leder ("The Peacemaker"), co-written by Bruce Joel Rubin ("Ghost") and Michael Tolkin ("The Rapture") and sported an all-star cast including Morgan Freeman, Robert Duvall, Téa Leoni, Elijah Wood, Maximilian Schell, Leelee Sobieski, Kurtwood Smith and even future "Iron Man" trilogy director Jon Favreau. After the deadly comet is discovered by astronomer Dr. Marcus Wolf (Charles Martin Smith) and high school student Leo Biederman (Wood), the movie follows three major plot threads: Duvall must lead a team of astronauts (including Favreau) to either destroy the comet or deflect its path away from Earth; Wood and Sobieski are ordinary civilians hoping to be selected to survive the comet's impact; and Leoni is an ambitious MSNBC reporter named Jenny Lerner whose intrepidity leads her to stumble upon the comet's existence, thereby forcing President Tom Beck (Freeman) to inform the world in advance. Lerner also has a moving subplot about reconciling with her estranged father, played by Schell.

Grossing nearly $350 million on an $80 million budget, "Deep Impact" was a financial success, although not as much of a blockbuster as "Armageddon," which grossed $553 million on a $140 million budget. This is perhaps unfortunate, because while scientists tend to view "Armageddon" as horribly inaccurate in its physics (including many who spoke to Salon), scientists whom Salon spoke to had favorable feelings towards "Deep Impact." 

"It's not hard to be more scientifically accurate than most sci-fi movies," explained Dr. Joshua Colwell, a planetary scientist and physics professor at the University of Central Florida. Colwell, who served as a "comet advisor" on "Deep Impact," told Salon by email that the movie's "director, producers, and writers made a decision to make the movie as realistic as possible while staying true to the story they were telling." This included having a large amount of time separate the discovery of the comet from the time of impact; giving the comet a realistic size (7 miles/11 kilometers wide), depicting the comet's features realistically; showing the impact realistically; and conveying the physics of the comet realistically. To the last point, that included conveying the astronaut's near weightlessness on the comet, and having the spacecraft itself tethered to the comet because of its low gravity.

"The movie depicts both an attempt to deflect the comet and also the creation of a subterranean 'ark' to house a large number of people to survive the catastrophic and long-lasting effects of the impact," Colwell observed. "Both of these activities are plausible, but both require huge resources and a lot of time to put together."

Emory University Physics Professor Dr. Sidney Perkowitz — whose famous criticisms of the pseudoscience in the 2003 sci-fi movie "The Core" catalyzed the creation of the Science and Entertainment Exchange, which works with Hollywood to encourage scientific accuracy — was not involved in making "Deep Impact." Yet he also praised the movie as among the most accurate of the sci-fi sub-genre that he dubs "Rocks from Space." In addition to "Deep Impact" and "Armageddon," that sub-genre includes "When Worlds Collide" (1951), "Meteor" (1979), "Don't Look Up" (2021), and "Moonfall" (2022).

"'Deep Impact' has the best combination of reasonably correct science, good special effects, a dramatic story, and a look at what a comet strike would mean to people individually and world-wide," Perkowitz told Salon. "I think that's the 'closest to reality' a sci-fi film can get."

In particular, Perkowitz singled out how "Deep Impact"'s central save-the-world plot — the astronauts must explode nuclear devices from within the comet so that they can alter its course — was pretty close to the truth, at least based on what was known at the time.

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"Most of the films I've listed imagine that nuclear weapons could deflect or destroy the incoming body," Perkowitz wrote to Salon. "That's made explicit in 'Armageddon,' where a NASA scientist calculates that an H-bomb going off deep within the incoming asteroid would split it in two, with the pieces flying off on paths that would miss the Earth." Apparently this would not work in real life; as Perkowitz explains, a group of physics students calcuated in 2002 that a hydrogen bomb would yield two astroid chunks that were a mere 1,200 feet apart, meaning the asteroid of "Armageddon" would still have struck Earth. 

"'Deep Impact' partially corrects this," Perkowitz noted. "The nuclear weapon splits the comet in two all right, but the smaller chunk lands in the Atlantic Ocean and raises a tsunami that devastates Manhattan."

Perkowitz noted that the film still inaccurately shows the larger chunk of the comet being destroyed by a nuclear bomb, but gives it points for showing that those nukes could produce collateral damage, which is why NASA no longer advocates for them in this potential situation.

"In its DART mission last year it showed the feasibility of using a spacecraft to nudge a space rock off a harmful path," Perkowitz wrote. "So 'Deep Impact' gets scientific points from me for correctly using the physics of nuclear weaponry. It also created an awe-inspiring CGI tsunami, which at the time I think was considered a big achievement."

Dr. Chapman also praises "Deep Impact"'s scientific chops — and that's saying something given that he attended the first asteroid-impact scientific meeting in 1981, which was organized by Gene Shoemaker, another 'comet advisor' for this film.

"If some threat like this were to arise, 'Deep Impact' roughly depicts a plausible set of events," Chapman wrote to Salon.

Chapman ticked off the (unrealistic) initial discovery of the comet by an amateur astronomer (the Virginia teenager Biederman), the follow up by a professional at Kitt Peak Observatory near Tucson, the involvement of NASA and high-ranking government officials going up to the president, the space expedition to implant nuclear devices, "preparing alternative 'civil defense' measures (like constructing caves to try to preserve elements of civilization if the deflection attempt fails)" and the creation of the immense tsunami at the film's climax.

"No other impact-disaster film I have seen has portrayed such a realistic scenario; other kinds of sci-fi movies generally take place in the more distant future, often involving fanciful elements that are totally beyond today's realities," Chapman concluded. "'Armageddon' is set in today's world but presents a much less believable story and a totally unrealistic picture of the oncoming celestial body" — an asteroid in the case of "Armageddon."

This does not mean that "Deep Impact" is without its inaccuracies. Perhaps the most notable one isn't so much a scientific error as it is a scientific improbability — namely, that the mathematical odds are overwhelmingly against an NEO-impact event occurring in our lifetimes.

"Such an impact is very, very, very improbable in the lifetime of anyone," Dr. David Stevenson, a planetary scientist at the California Institute of Technology, wrote to Salon. "It would be unwise to obsess over such events when there are things that happen much more often to be concerned about." Indeed, the average length of time between extinction-size asteroid strikes on Earth is tens or hundreds of millions of years. "The time between impacts is probably almost a million times the lifetime of any particular individual, probably even much longer than the total survival time of the human species based on what we know about biological evolution," Stevenson added.

Chapman echoed Stevenson on the low probability of an NEO collision in our lifetimes, and also pointed out other scientific errors in the film. At one point the filmmakers imply that the comet got "bumped" into Earth's orbit by other celestial bodies, but such collisions usually just create smaller fragments; orbital changes are generally caused by gravitational forces such as nearby planets. And a smaller quibble: the movie also purports in an early scene to show the double star Mizar and Alcor, but the photograph on screen is not of them. Similarly, a comet as bright as the one shown in that scene would have been discovered by other astronomers long before Wood's precocious teenage character does so.

That is not all.

"I don't understand the attempt to use 'Titan missiles' just days before impact, to deflect the body; whatever they had in mind would never work without violating physics," Chapman noted, adding that bombs large enough to blow the comet into smaller boulders which can safely disintegrate in Earth's atmosphere would have been used much earlier in the film's story. Indeed, waiting until the last second could obviate the plan's entire purpose: "It would have to be done much earlier or the debris would mainly strike the Earth with nearly equal E.L.E. consequences," Chapman explained, using the acronym for Extinction Level Event (which was invented by the filmmakers).

Of course, as Chapman repeatedly acknowledged, "Deep Impact" is first and foremost trying to entertain audiences. Here, the scientists who spoke with Salon were of one mind: The Chapmans praised the acting, cinematography and special effects, concluding that it deserved better reviews; Stevenson said it "ranks high," in particular "much higher than 'Armageddon'"; Colwell gave it "an enthusiastic thumbs up" and recalled one of his students crying at the end; and Perkowitz argued that it "stands out for the human element it expresses, especially in two scenes: a group of people exiting their cars to watch as the smaller piece of the comet passes overhead, their faces showing that they understand what this means; and TV journalist Tea Leoni hugging her estranged father Maximillian Schell like a little girl seeking comfort, as the gargantuan tsunami towers over them before utterly destroying them."

Indeed, by telling realistic human stories, "Deep Impact" further achieves something in the direction of authenticity: Trying to depict how a broad swath of humanity would respond to the literal extinction of our species. If nothing else, one hopes that people would be guided by a strong, confident and wise leader during that period — such as Freeman's character and the undeniable highlight of the movie, President Tom Beck.

"I was amused and pleased to read the Gizmodo article's praise for President Beck's speech presaging the arrival of the wave, because it was taken very closely from my script notes provided shortly before the scene was shot," Colwell recalled to Salon.

"Deep Impact" co-screenwriter Bruce Joel Rubin (whom film critic Roger Ebert called one of "the brightest writers in Hollywood") told Salon that he believes the movie and Freeman's performance helped "pave the way for Barack Obama," America's first black president, to be elected a decade after the movie's release. This would be fitting with the story's humanitarian genesis; "Deep Impact" was a natural outgrowth of Rubin being inspired by a 1964 Oscar-winning short documentary called "To Be Alive!" Watching it as a young man at that year's New York's World's Fair, Rubin recalled being deeply moved by the innovative multi-screen format which explored the commonalities of different human cultures in the United States, Europe, Africa and Asia. Its basic message: Being alive is a "great joy" and should be celebrated.

"'Deep Impact,' in my mind, had a bigger canvas at one point," Rubin recalled. "There were images of half of Brooklyn standing on the shore watching the comet hit." However, that shot was taken out, and the one left in was just the actress Téa Leoni and her on-screen father standing and watching the comet. Rubin preferred the community shot: "It was about people reaching out and touching and holding each other and knowing this was the end. It was existentially potent, and I wish it had stayed in the film — but unfortunately as a writer you don't control those things."

This is not to say that Rubin isn't proud of "Deep Impact." Sometimes things he liked which were taken out later got put back in. While he had little say about the film's development after director Mimi Leder took over, Rubin's individual creative imprint is still all over the final movie — particularly its psychological complexity and progressive message.

Yet even within that message, there is nuance. Back in the 1990s, the body politic was not nearly as polarized as it is today; and Americans had more faith in their institutions to help and save them. Hence, "Deep Impact" shows a world where human institutions work as they're supposed to. As far as disaster movies are concerned, there's something faintly optimistic about that premise (particularly in contrast with the bumbling governmental response depicted in "Don't Look Up," its peer in the rocks-from-space genre).

Indeed, in the "Deep Impact" cinematic universe, the president is a good man who listens to scientists and offers sage advice; the news media tells the truth to the best of its ability; teachers pay attention to their students and encourage their intelligence; and the mass of humanity, instead of rioting and acting selfishly at the news of the comet's approach, for the most part remains civilized.

Rubin was unsure if the movie was actually optimistic, though. He recalled changes to the final scene of the film, in which Freeman's president eloquently declared, "Cities fall, but they are rebuilt. And heroes die, but they are remembered. We honor them with every brick we lay, with every field we sow, with every child we comfort, and then teach to rejoice in what we have been re-given."

"Because the end was so depressing, the scene of Morgan Freeman's speech was added after the filming was over," Rubin recalled. "They went back and said, 'There has to be an optimistic speech, a 'We will survive speech.' But that was not in the original movie. It was very, very dark."

Then Rubin reflected on how, despite his attempt to make "Deep Impact" dark, the last 25 years of history show reality is even darker than fiction. That includes humanity's failure to address climate change, American leaders' bungling of the COVID-19 pandemic, and the increasing prevalence overall of pollution.

"My feeling is optimism kind of is all we have," Rubin told Salon. "I hope it starts to generate some kind of action in the world today. But I have grandchildren and I am very pained by the reality of what I've presented in 'Deep Impact,' whether it's a fictional comet on a collision course with the Earth or our own real mishandling of the planet we live on."