Dinosaurs might still be roaming the Earth if the celestial object that smashed into the present-day Gulf of Mexico had hit almost anywhere else on the planet. By hitting the rocky terrain of the Yucatan Peninsula about 65 million years ago, however, the impact sent the soot into the air that would trigger a chain reaction and lead to mass extinction.

Even with the impressive 9-kilometer (5.6-mile) diameter of the object, believed to be an asteroid, that caused the event, the odds that it would have wiped out the dinosaurs were only 13 percent, the Japanese scientists Kunio Kaiho and Naga Oshima have found, according to new research they published on Thursday in the journal Scientific Reports.

"They were unlucky," Kaiho told Britain's Guardian newspaper.

Read more: Protecting the earth from an asteroid strike — what can we do?

Gambling with extinction

Impacts on this scale are rare enough, but the object that initiated what scientists call the Cretaceous-Paleogene extinction event happened to also hit an area rich in hydrocarbon and sulfate. The force of the impact heated the materials, "forming stratospheric soot and sulfate aerosols and causing extreme global cooling and drought," the scientists report in the paper. German scientists have also speculated on the significance of the site of impact.

"The amount of hydrocarbon and sulfur in rocks varies widely, depending on location," the scientists found; 87 percent of the Earth's surface did not harbor enough of these deposits.

"The site of asteroid impact, therefore, changed the history of life on Earth," the scientists wrote.

The presumed site of the collision on the Yucatan is a subterranean, partially submerged crater about 180 kilometers wide and 20 kilometers deep.

'Particularly bad time'

With soot blocking the sunlight, the Earth's average temperature dropped by about 10 degrees Celsius (18 F), destroying plant life and driving the existing ecosystem to collapse. In the end, about 75 percent of animals were extinct, including nearly all dinosaurs.

In 2014, the Edinburgh University paleontologist Steve Brusatte said dinosaurs might have survived the impact "if it had hit a few million years earlier or later."

"The asteroid hit at a particularly bad time," he wrote in the journal Nature, speculating that a decrease in the diversity of plant-eating dinosaurs about 66 million years ago might have made the ecosystem more vulnerable to extinction-level events.

The impact might have been a stroke of bad luck for dinosaurs, but it also led to "the subsequent macroevolution and diversification of mammals," including humans, Kaiho and Oshima write.