If the asteroid that obliterated the dinosaurs had struck Earth just half a minute sooner or later, there might still be giant reptiles roaming the planet today.

That’s one revelation from a BBC documentary, The Day the Dinosaurs Died, that premiered Monday. “In the end it wasn’t the size of the asteroid, the scale of blast, or even its global reach that made dinosaurs extinct – it was where the impact happened,” says Ben Garrod, one of the presenters of the film. Garrod joined scientists on a mission to the Gulf of Mexico to drill into the seafloor and retrieve the first physical evidence of the space rock, which made impact 66 million years ago.

If the timing or the trajectory had been just slightly off, the asteroid quite likely would have struck the deep ocean of the Atlantic or Pacific, rather than shallow coastal waters. There, a lot less rocky material would have been vaporized and sent into the atmosphere, where it sent the planet into a sort of nuclear winter, killing most of the plants and all but the hardiest of the animals.

Sulfur dioxide, which is also released naturally through volcanic activity, is the opposite of a greenhouse gas — it reflects the sun’s energy and has a cooling effect. Both the vaporized rock itself and the massive volcanoes set off by the force of the impact would have added massive quantities of sulfur into the air, resulting in a long-term deep freeze.

As it stands, the asteroid likely penetrated right through Earth’s crust and into the upper mantle with the force ten billion times as large as the atomic bomb dropped on Hiroshima. The space rock and a large chunk of this planet would have been instantly liquefied, with a column of molten rock rising nine miles up before collapsing under its weight.

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If the asteroid had hit the deep ocean, it still would have been a hell of a show. But the long-term consequences would have been dulled, possibly allowing more species of dinosaur to survive through until today. But then again, if that planet-altering event hadn’t occurred exactly the way the that it did, there’s a very good chance humans would never have existed.

Photos via DiscoveryDinosaurs/YouTube