Two planets about 300 light years from Earth slammed into each other recently, US astronomers said Tuesday, the first time evidence of such a catastrophic collision has been seen by scientists.

Astronomers from the University of California, Los Angeles (UCLA) and the California Institute of Technology (CALTECH) said the crash involved two planets orbiting a star in the Aries constellation.

The collision was uncovered while astronomers were attempting to measure the star's age, and found an unusually large amount of dust orbiting the star.

"It's as if Earth and Venus collided with each other," said Benjamin Zuckerman, UCLA professor of physics and astronomy.

"Astronomers have never seen anything like this before. Apparently, major catastrophic collisions can take place in a fully mature planetary system."

The astronomers' research will be published in the December issue of Astrophysical Journal. The collision was an "ultimate extinction event" that would have wiped out any life on either planet in minutes, the report said.

The prospect of Earth suffering an apocalyptic collision with another planet or asteroid has been fodder for science-fiction writers and film-makers ever since Philip Wylie and Edwin Balmer's 1933 novel "When Worlds Collide."

Astronomers said however the odds of such collisions occurring remained low.

Tennessee State University astronomer Gregory Henry said scientists in the United States and France have long studied the stability of planetary orbits.

"Their computer models predict planetary motions into the distant future and they find a small probability for collisions of Mercury with Earth or Venus sometime in the next billion years or more," Henry said.

Zuckerman noted, however, that collisions have occurred in our solar system's past. "Many astronomers believe our moon was formed from the grazing collision of two planetary embryos, the young Earth and a body about the size of Mars, a crash that created tremendous debris, some of which condensed to form the moon and some of which went into orbit around the young sun," he said.