By Larry Klaes

Tau Zero journalist Larry Klaes now returns with a look at the impact that evidently killed the dinosaurs, and the unusual family of planetoids now thought responsible. Is Chicxulub an event that could only have happened in the distant past, or a warning of possible danger ahead?

About 65 million years ago, a large planetoid at least six miles in diameter struck our planet at what is now the Yucatan Peninsula in Mexico, leaving a crater over 100 miles across. The force of the impact, which was two million times more powerful than the greatest nuclear bomb ever detonated, instantly killed every living thing within a one thousand mile radius.

Many other creatures suffered similar fates when debris from the planetoid impact flung high into the air came plunging back to the ground, setting off firestorms that spread across the globe. The clouds of smoke and dust from this event hung in our atmosphere for several years, blocking out the Sun and terminating many plants that relied on solar energy for photosynthesis. As a result, many plant eating creatures died from the loss of their food source, which in turn affected the animals that preyed on them.

The dinosaurs, having existed on Earth for over 160 million years, were among those victims who disappeared from our planet. The mammals, which until then had been little more than groups of rodents, came to prominence and are among the dominant species today, with humanity being among their members.

One major factor that remained unknown was what made what is now called the Chicxulub crater. Scientists assumed it was either a planetoid or comet, but the ‘Dino Killer’s’ exact nature and place of origin seemed lost in time and space.

Now a team of team of researchers from the Southwest Research Institute (SwRI) and Charles University in Prague think they may know where the space rock in question came from. They have described their ideas in an article titled, “An asteroid breakup 160 Myr ago as the probable source of the K/T impactor,” published in the September 6 issue of the science periodical Nature.

According to the theory developed by the international team, which includes Dr. William Bottke (SwRI), Dr. David Vokrouhlicky (Charles University, Prague), and Dr. David Nesvorny (SwRI), about 160 million years ago – give or take 20 million years – a large planetoid residing deep within the planetoid belt between the planets Mars and Jupiter was struck by a smaller but still significantly sized planetoid. The resulting debris became what is known today as the Baptistina planetoid family.

Some of the many pieces from this family eventually drifted from the planetoid belt and became Earth-crossing objects. One space rock from the Baptistina family may have struck our Moon some 108 million years ago, creating the prominent ray crater Tycho in the lunar southern hemisphere. Another family member went on to form our planet’s Chicxulub crater, significantly changing the types of creatures on Earth 65 million years ago.

Support for these conclusions comes from the impact history of Earth and Moon. Both worlds bear the scars of a two-fold increase in the formation rate of large craters over the last 100 to 150 million years.

“The Baptistina bombardment produced a prolonged surge in the impact flux that peaked roughly 100 million years ago,” explained Nesvorny. “This matches up pretty well with what is known about the impact record.”

For those who might think that the threat to our world from space has passed, Bottke warns that “…we are in the tail end of this shower now. Our simulations suggest that about 20 percent of the present-day, near-Earth asteroid population can be traced back to the Baptistina family.” This means there is still a chance that a Near Earth Object (NEO) could strike our planet, causing destruction and death on a level equivalent to the one experienced by the dinosaurs.

Ever since humanity became aware of this celestial danger, some scientists and others have been devising means to keep our species from going the way of the dinosaurs. As they planned methods to deflect and destroy NEOs that could strike Earth, they also realized that a detailed knowledge about the types of bodies that threaten our world needed to be made. Otherwise, an incorrect technique to protect our planet could make a bad situation worse.

One method scientists have deployed to learn more about NEOs is with powerful radar beams from Earth, which determine not only the shape of such planetoids but also their makeup. Radar helps researchers learn if a planetoid is a solid or porous body. Such information is critical when determining how best to deflect or destroy a space rock headed for our world.

The best tool for this task has been the Arecibo Radio Observatory on the island of Puerto Rico. The 1,000 foot wide dish is 25 times better than any other existing similar instrument for peering into the nature of these potentially deadly objects in space.

Unfortunately for this branch of science, budget constraints imposed upon Arecibo by the National Science Foundation (NSF) have curtailed much of the planetary radar operations from that facility. The very existence of Arecibo itself is in jeopardy through the year 2011. With no other comparable facilities being built for at least a decade or more, it is hoped that those who control the finances in these areas will see the wisdom in continuing the study and search for planetoids that could cause irreversible harm to our civilization and all life on Earth.