The extinction of the dinosaurs came because something large and dangerous from outer space slammed into planet earth about 65 million years ago, mostly likely at the site in Mexico where the 112 mile wide Chicxulub crater is found to this day. Most scientists think it was a large, slow-moving asteroid. But could it have been a small, fast-moving comet that skidded across the landscape instead?
Last week, Dartmouth college researcher Jason Moore and his team presented evidence for the comet theory at the 44th Lunar and Planetary Science Conference in The Woodlands, Texas. They looked at the chemistry of the sediments deposited by the collision. According to their results, a smaller object hit the Chicxulub site than we previously believed — which means that it had to be moving fast when it hit. Otherwise, a smaller object would not have done as much damage as it did.
And it just so happens that we have plenty of smallish, fast-moving objects jaunting around the solar system all the time. They’re called comets, people, and we see them semi-regularly near the earth.
This month, a great many of us, including me, have enjoyed views of the beautiful comet PanSTARRS. An even more impressive comet, projected to be brighter than the moon, is predicted to enter our skies in November.
However, neither of those objects will come dangerously close to the earth, and we don’t have to worry yet about following the dinosaurs into extinction.
Now, when a big old asteroid smashes into the earth, you definitely know about it. Just ask the victims of the February Russian meteor, a stony meteorite which injured over 1,200 people and damaged over 4,000 buildings.
A comet? Not so much. Often, it’s just an oversized snowball that melts as it gets too near the sun, causing a long streamerlike tail to develop. And a comet’s tail colliding with earth, which has happened before, just doesn’t do much that anyone notices.
However, it’s certainly possible that the stony core of the comet could do some serious damage.
Whether it was the heart of a comet or an ordinary asteroid that impacted at Chicxulub, the result for the dinosaurs was the same — extinction.
[comet photo courtesy Naskies and Wikipedia Commons]
