Maybe there was a second (it's recent history), but let's stick to the already "established" facts. About 66 million years ago, an asteroid nearly 10 kilometers (6 miles) in diameter struck Earth near Mexico's Yucatan peninsula, ending the lives of many species on the planet. Chicxulub, this is the name by which we indicate that asteroid, produced a crater 177 kilometers (110 miles) wide and 20 kilometers (12 miles) deep. And today scientists have also estimated more precisely the apocalyptic proportions of the Tsunami that the "dinosaur asteroid" generated.

Unthinkable waves
Scientists of the National Oceanic and Atmospheric Administration (NOOA) calculated that the waves caused by the tsunami reached an impressive height of 4 kilometers (2,5 miles) when they slammed into the coast of the Gulf of Mexico. An estimated catastrophe 30.000 times larger than any other recorded event.
NOAA also created a simulation of the tsunami expanding around the planet, comparing both what Earth looked like 66 million years ago (with land masses in black) and the planet's current shape (represented by a white outline). . It is worth noting that the Earth continues to change shape due to continental drift which occurs at a rate of about 2,5cm (one inch) per year.
After the asteroid of the dinosaurs, prevent there is one "of the humans"
It must be said, it's not a question of "if", but only of "when". There are asteroids that could cause great damage to the Earth, and sooner or later some will appear. Maybe not tomorrow, but it's better to prevent the circumstance. That's why NASA tries to find ways to deflect or destroy any asteroid that poses a threat.
Last year the project had an excellent response Double Asteroid Redirect Test (DART), who managed to change the orbit of an asteroid by hitting it with a car-sized spacecraft. For things like the dinosaur asteroid we'll need more strength and means, but... hey, that's what training is for.