TOPIC OF THE MONTH – ASTEROIDS

MANY of us know that 66 million years ago a 17km wide asteroid hit Earth near Mexico, leaving a crater nearly 200km across which killed off three quarters of all species on the planet, including the dinosaurs.

But only fairly recently have scientists discovered why the impact had such a devastating effect.

Imaging and drilling into the impact crater have shown that the asteroid hit at an angle of 60 degrees and a speed of 12km per second.

It was the angle of impact that was critical.

At this particular angle the impact put vastly more debris into the upper atmosphere than if it had landed at a more vertical angle.

Calculations show the impact put 325 billion tonnes of sulphur and 425 billion tonnes of carbon dioxide into the atmosphere, creating a layer of aerosol that blocked sunlight, causing the temperature of the entire planet to fall to near freezing for several years.

However some hardy lifeforms survived and the researchers found microbial fossils in the impact crater itself within just a few years after the impact.

As the planet gradually warmed life recovered.

Now all the larger asteroids are monitored continuously to look for any dangerous changes in their orbits.