Also, similar impacts can be expected every 250 million to 750 million years

Dinosaurs were wiped out from Earth over 66 million years ago when an asteroid from the belt between Mars and Jupiter slammed into the planet. However, researchers have now found it was a comet from the edge of the solar system which caused the devastation, not a nearby asteroid.
Jupiter was responsible for the long-distance comet to crash into our planet, and similar impacts can be expected every 250 million to 750 million years, says a study.
Amir Siraj, a Harvard student, co-authored the paper with Professor Avi Loeb and published in the journal Scientific Reports this week, which pushes back against older claims of the cataclysmic event.
Siraj told AFP that Jupiter acts as a kind of pinball machine that kicks these incoming long-period comets into orbits that bring them very close to the sun.
The duo has developed a statistical model that showed the probability that long-period comets would hit Earth is consistent with the age of Chicxulub and other known impactors.
Their theory is: Jupiter’s gravity shot this incoming comet into an orbit that brought it very close to the sun, whose tidal forces caused the comet to break apart. Some of the comet’s fragments entered Earth’s orbit, and one 50 miles across, roughly the size of Boston slammed into the coast of Mexico, said reports.
Also, another line of evidence in favour of their argument is the composition of Chicxulub: only about a tenth of all asteroids from the Main Belt, which lies between Mars and Jupiter, is made up of carbonaceous chondrite, while most comets have it.