Artistic rendition of the Chicxulub impactor striking ancient Earth, with Pterosaur observing. Could pieces of the same impact swarm have hit the Moon, too? Credit: NASA
For decades, scientists have theorized that a massive impact caused the Cretaceous-Paleogene extinction event. This event occurred about 66 million years ago and caused the mass extinction of about 75% of all plant and animal species on Earth (including the non-avian dinosaurs). With the discovery of the massive Chicxulub crater in the Yucatan Peninsula (southern Mexico) in the 1970s, scientists concluded that they’d found the impact responsible. Based on all the available data, the Chicxulub Impact event is believed to have been as powerful as 100,000 billion metric tons (110,231 U.S tons) of TNT.
This blast was more powerful than all the nuclear devices in the world combined and sent an estimated 25 trillion metric tons (~27.5 US tons) of hot dust, ash, and steam into the atmosphere, creating a global winter. But according to new research led by the University of Michigan, an international team of geologists has determined that the impact also created a global tsunami. According to their findings, this tsunami was 30,000 times more powerful than the 2004 Indian Ocean tsunami, one of the largest and most devastating tsunamis on record.
Melanie During excavating a paddlefish in the Tanis deposit. Credit: Jackson Leibach, via Nature.
We’ve long known a disaster took place about 66 million years ago, where in a geological instant, 75% of the plants and animals on Earth were wiped out, including all the land-roaming dinosaurs. But here’s a new detail about that event: Even though we can’t pinpoint exactly what year this disaster took place, we now know it happened during the springtime.
How do you track an asteroid that hit the Earth over 60 million years ago? By using a combination of geology and computer simulations, at least according to a team of scientists from the Southwest Research Institute (SwRI). Those methods might have let them solve a long-standing mystery of both archeology and astronomy – where did the asteroid that killed the dinosaurs come from?
Artist's rendering of a comet headed towards Earth. Public domain illustration.
About 66 million years ago a massive chunk of rock slammed into Earth in what is the modern-day Yucatan Peninsula. The impact extinguished about 75% of all life on Earth. Most famously, it was the event that wiped out the dinosaurs.
While mainstream scientific thought has pointed to an asteroid as the impactor, a new research letter says it could’ve, in fact, been a comet.
A three-dimensional cross-section of the hydrothermal system in the Chicxulub impact crater and its seafloor vents. The system has the potential for harboring microbial life. Illustration by Victor O. Leshyk for the Lunar and Planetary Institute.
How did life arise on Earth? How did it survive the Hadean eon, a time when repeated massive impacts excavated craters thousands of kilometres in diameter into the Earth’s surface? Those impacts turned the Earth into a hellish place, where the oceans turned to steam, and the atmosphere was filled with rock vapour. How could any living thing have survived?
Ironically, those same devastating impacts may have created a vast subterranean haven for Earth’s early life. Down amongst all those chambers and pathways, pumped full of mineral-rich water, primitive life found the shelter and the energy needed to keep life on Earth going. And the evidence comes from the most well-known extinction event on Earth: the Chicxulub impact event.
An artist's illustration of an asteroid shower on the Earth-Moon system. Image Credit: Murayama/Osaka Univ.
Natural processes here on Earth continually re-shape the planet’s surface. Craters from ancient asteroid strikes are erased in a short period of time, in geological terms. So how can researchers understand Earth’s history, and how thoroughly it may have been pummeled by asteroid strikes?
Scientists can turn their attention to our ancient companion, the Moon.
An ankylosaurus enjoying a drink of water while the asteroid strikes in the distance. Image Credit: Fabio Manucci
It seems almost certain that an asteroid impact wiped out the dinosaurs. But only almost. Another competing theory won’t completely go away: the extinction-by-volcano theory.
A new study from the UK piles more evidence on the asteroid side of the debate, while adding a new volcanic twist. These researchers say that volcanic activity actually helped life recover from the asteroid strike.
A Three-dimensional cross-section of the hydrothermal system in the Chicxulub impact crater and its seafloor vents. The system has the potential for harboring microbial life. Illustration by Victor O. Leshyk for the Lunar and Planetary Institute.
The Chicxulub impact event was an enormous catastrophe that left a huge imprint on the Earth’s surface. Not only did it cause the mass extinction of the dinosaurs, it left a crater 180 km (112 miles) in diameter, and deposited a worldwide layer of concentrated iridium in the Earth’s crust.
But a new study shows that the impact also left its mark deep underground, in the form of a vast hydrothermal system that modified a massive chunk of the Earth’s crust.
What an asteroid hitting the Earth might look like. Image credit: NASA/Don Davis.
Which camp are you in: volcanoes? Or asteroids?
When it comes to the extinction of the dinosaurs, science has whittled it down to those two possibilities. The asteroid strike has been the leading candidate for quite some time now, but those darn volcanoes refuse to stand down.
A new study is presenting even more evidence that it was the impact that wiped out the dinosaurs, and not volcanoes.
Artistic rendition of the Chicxulub impactor striking ancient Earth, with Pterosaur observing. Could pieces of the same impact swarm have hit the Moon, too? Credit: NASA
Sixty-six million years ago, an asteroid struck Earth in what is now the Yucatan Peninsula in southern Mexico. This event, known as the Chicxulub asteroid impact, measured 9 km in diameter and caused extreme global cooling and drought. This led to a mass extinction, which not only claimed the lives of the dinosaurs, but also wiped out about 75% of all land and sea animals on Earth.
However, had this asteroid impacted somewhere else on the planet, things could have turned out very differently. According to a new study produced by a team of Japanese researchers, the destruction caused by this asteroid was due in large part to where it impacted. Had the Chicxulub asteroid landed somewhere else on the planet, they argue, the fallout would not have been nearly as severe.
Satellite views of the Chicxulub impact site in the Yucutan Peninsula, southern Mexico. Image credit: NASA/JPL
Dr. Kaiho and Dr. Oshima began by considering recent studies that have shown how the Chicxulub impact heated the hydrocarbon and sulfur content of rocks in the region. This is what led to the formation of stratospheric soot and sulfate aerosols which caused the extreme global cooling and drought that followed. As they state in their study, it was this (not the impact and the detritus it threw up alone) that ensured the mass extinction that followed:
“Blocking of sunlight by dust and sulfate aerosols ejected from the rocks at the site of the impact (impact target rocks) was proposed as a mechanism to explain how the physical processes of the impact drove the extinction; these effects are short-lived and therefore could not have driven the extinction. However, small fractions of stratospheric sulfate (SO4) aerosols were also produced, which may have contributed to the cooling of the Earth’s surface.“
Another issue they considered was the source of the soot aerosols, which previous research has indicated were quite prevalent in the stratosphere during the Cretaceous/Paleogene (K–Pg) boundary (ca. 65 million years ago). This soot is believed to coincide with the asteroid impact since microfossil and fossil pollen studies of this period also indicate the presence of iridium, which has been traced to the Chicxulub asteroid.
Previously, this soot was believed to be the result of wildfires that raged in the Yucatan as a result of the asteroid impact. However, Kaiho and Oshima determined that these fires could not have resulted in stratospheric soot; instead positing that they could only be produced by the burning and ejecting of hyrdocarbon material from rocks in the impact target area.
When an asteroid struck the Yucatan region about 66 million years ago, it wiped out the dinosaurs, and most of life on Earth. If it had hit elsewhere, the dinosaurs might well have survived. Credit: NASA/Don Davis
The presence of these hydrocarbons in the rocks indicate the presence of both oil and coal, but also plenty of carbonate minerals. Here too, the geology of the Yucatan was key, since the larger geological formation known as the Yucatan Platform is known to be composed of carbonate and soluble rocks – particularly limestone, dolomite and evaporites.
To test just how important the local geology was to the mass extinction that followed, Kaiho and Oshima conducted a computer simulation that took into account where the asteroid struck and how much aerosols and soot would be produced by an impact. Ultimately, they found that the resulting ejecta would have been sufficient to trigger global cooling and drought; and hence, an Extinction Level Event (ELE).
This sulfur and carbon-rich geology, however, is not something the Yucatan Peninsula shares with most regions on the planet. As they state in their study:
“Here we show that the probability of significant global cooling, mass extinction, and the subsequent appearance of mammals was quite low after an asteroid impact on the Earth’s surface. This significant event could have occurred if the asteroid hit the hydrocarbon-rich areas occupying approximately 13% of the Earth’s surface. The site of asteroid impact, therefore, changed the history of life on Earth.”
Mass extinction only occurred when the asteroid having 9-km diameter hit the orange areas. Credit: Kunio Kaiho
Basically, Kaiho and Oshima determined that 87% of Earth would not have been able to produce enough sulfate aerosols and soot to trigger a mass extinction. So if the Chicxulub asteroid struck just about anywhere else on the planet, the dinosaurs and most of the world’s animals would have likely survived, and the resulting macroevolution of mammals probably would not have taken place.
In short, modern hominids may very well owe their existence to the fact that the Chicxulub asteroid landed where it did. Granted, the majority of life in the Cretaceous/Paleogene (K–Pg) was wiped out as a result, but ancient mammals and their progeny appear to have lucked out. The study is therefore immensely significant in terms of our understanding of how asteroid impacts affect climatological and biological evolution.
It is also significant when it comes to anticipating future impacts and how they might affect our planet. Whereas a large impact in a sulfur and carbon-rich geological region could lead to another mass extinction, an impact anywhere else could very well be containable. Still, this should not prevent us from developing appropriate countermeasures to ensure that large impacts don’t happen at all!
