5 Little-Known Facts About Earth Impactors And Meteorites


In this crazy age of Covid, when ‘staying alive’ has taken on a whole new meaning, the thought of being wiped out by an Earth-impacting comet or asteroid, seems more like the stuff of Hollywood science fiction than an immediate threat.

But a new book “Impact: How Rocks from Space Led to Life, Culture, and Donkey Kong” provides a lively and comprehensive history of how earth impactors and meteorites themselves have shaped both earth’s geophysical and cultural history since time immemorial. That’s even though meteorites —- solid debris from comets, asteroids, or meteoroids that reach a planetary or lunar surface —- weren’t officially recognized as being products of the heavens until the late 19th century.

Greg Brennecka, one of the world’s few professional meteoriticists and a cosmochemist at Lawrence Livermore National Laboratory in California, weaves a fascinatingly ambitious narrative that provides an eye-opening look at what happens when large meteors, asteroids and comets collide with our fragile biosphere. 

Coming on the heels of Netflix’s satirical comedy/disaster film “Don’t Look Up,” Brennecka’s book takes a serious historical look at how and why impactors and meteorites have continued to play such an important role in understanding the evolution of both our solar system and our own planet. But here are five underappreciated tidbits about meteorites that “Impact” manages to highlight.

—- Until only the 19th century, it wasn’t known for certain that meteorites originated from beyond Earth’s atmosphere.

They were often thought to be just regular Earth rocks tossed up by strong winds or volcanoes, writes Brennecka. But on average, over 100 tons of extraterrestrial material is added to Earth every day, mostly from micrometeorites, he writes. They’ve not only shaped our planet geophysically, but astrobiologically as well. “Large swaths of the ocean would be virtually devoid of life if micrometeorites did not provide bioavailable iron to plankton,” notes Brennecka.

—- The earliest known human interaction with a meteorite dates back some six thousand years.

Small rusted meteoritic beads have been found in a grave dating to 4000 B.C. at what is now Tepe Sialk in modern-day Iran, notes Brennecka. But despite their influence on both our planet and our culture and society, there remain only about a hundred fulltime, professional meteoritic researchers in the world today. “The Meteoritical Society, the sole international society engaged in the study and dissemination of information about meteorites, has a membership of fewer than one thousand people,” writes Brennecka.

—- Meteorites don’t discriminate. 

They are equal opportunity offenders and ignore all political and geographic boundaries. However, the most productive meteorite hunting grounds on Earth are areas that naturally lack dark rocks and are devoid of vision-obscuring vegetation, writes Brennecka.

Antarctica is arguably the best place to look for meteorites; there have been many martian meteorites found on the continent at the bottom of the world. However, three other arid expanses offer fabulous meteoritic hunting grounds. They are the flat, treeless expanse of the Nullarbor region of southern Australia, where one can find the largest single exposure of limestone in the world, notes Brennecka. As such, dark, black rocks stick out in dramatic fashion. And because the Nullarbor has had an arid climate for tens of thousand of years, meteorites do not degrade like they do in more temperate areas, he writes.

Northern Chile’s vast and flat Atacama Desert, one of the driest places on Earth, looks more like Mars than a limestone desert. But because it gets so little precipitation, it is the perfect place to preserve meteorites. “Multiple meteorites found in the Atacama had lain there for more than 2 million years,” writes Brennecka. 

Finally, Oman, on the southeastern coast of the Arabian Peninsula, has a desert with what Brennecka describes as intense areas of white terrain. “Carbonate beds and salt flats are common in Oman, providing a perfect backdrop to contrast dark meteorites,” writes Brennecka. 

—- Historically, human civilization hasn’t feared death by either impactors or large meteors.

That’s because only in the last few hundred years, did most people become aware that rocks could fall from space, as Brennecka writes. Secondly, as he points out, previous generations were preoccupied with earthly problems like cholera, famine, or even stampedes by groups of angry oxen. Today, we are preoccupied with a virus plague, but the extraterrestrial threat remains a reality.

As for the first human death caused by a meteorite?

Only within the last two years have corroborating documents been found that point to the 1888 death of a man via a meteoritic airburst, Brennecka writes. The airburst took place over what is modern-day iraq but the actual meteorite has yet to be located and verified, Brennecka writes.

—- What happens if we detect a monster impactor on heading our way?

The first step is to simply get a spacecraft within the near vicinity of a threatening object, Brennecka notes. “Since gravity acts like an invisible tether, the object is gravitationally attracted to the spacecraft once they are near one another,” writes Brennecka.  “Slowly change the course of the spacecraft with gentle thruster bumps every now and again, ever so slightly dragging the rock along with you in space,” in the manner of what he terms a “gravity tractor.”

If there’s not more than a few weeks to act before being obliterated by a civilization-ending impactor, Brennecka notes that we can always go nuclear. The options would include either firing a spacecraft loaded with either conventional or nuclear weapons into earth orbit and firing at the object from space itself. However, the simplest option would be to fire a ground-based ballistic missile onto a trajectory that would cross the object and hopefully neutralize it as a threat. 

We humans have yet to experience the full force of a civilization-ending impactor. But “impact” is both an entertaining and poignant reminder that we literally live in a sea of planetary debris that continues to shape this Valhalla of a planet. 

Let’s hope that as time clicks on, we will be better equipped to deal with a true planet killer once we have it in our sights.



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