The frequency of massive rock falls from space

NEW YORK (Reuters Health) - Large rocks have fallen out of space at more than twice the normal rate, but they said there was no need to worry.

According to the study, published in Thursday's issue of Science, over 290 million years ago, asteroids have fallen on Earth more than twice as much as 700 million years ago.

However, there is no need to worry, as asteroids continue to hit the Earth on average every few million or millions of years, even as the collision rate increases.

NASA's list does not show a fall of potential large space rocks or imminent major threats.
The greatest known risk is a 1.3-km wide asteroid with a probability of 99.988 per cent not hitting the Earth when it is very close in 861 years.

Most scientists believe that dinosaurs and many other breeds were extinct after a huge space rock crashed in Central America about 65 million years ago.

"These events are so rare and so far away that I'm not worried about them," said study author Sarah Mazroui, a planetary scientist at the University of Toronto. "It's just a game of possibilities."
Mazroui and her colleagues in the United Kingdom and the United States compiled a list of drilling holes on the ground and the 20-kilometer-long moon that showed their dates.

A large nozzle requires a space rock of 800 meters.

The team scored 29 holes no more than 290 million years old and 9 between 291 million and 650 million years ago.