Ammonites basking under the Late Cretaceous sun. Artwork by Callum Pursall (@cpursall on X)
I must confess, I think asteroids and I think of movies like Deep Impact or Armageddon! Scientists think that an asteroid like the ones that appeared in the Hollywood blockbusters struck Mexico 66 million years ago and led to the extinction of the dinosaurs. It now seems they may not have been the only ones that were wiped from our planet. Ammonites are marine mollusks that flourished for 350 million years but they were wiped out too. Some research suggests they were struggling in North America but thriving in other parts of the world.
This is a computer-generated, three-dimensional perspective of the surface of Venus showing Maat Mons. It's Venus's highest volcano and is 8 kilometres (5.0 mi) high. The viewpoint is located 634 kilometers (393 miles) north of Maat Mons at an elevation of 3 kilometers (2 miles) above the terrain. Lava flows extend for hundreds of kilometers across the fractured plains shown in the foreground, to the base of Maat Mons. The vertical scale in this perspective has been exaggerated 10 times.
Credits: NASA/JPL
Is there anything good about volcanoes? They can be violent, dangerous, and unpredictable. For modern humans, volcanoes are mostly an inconvenience, sometimes an intriguing visual display, and occasionally deadly.
But when there’s enough of them, and when they’re powerful and prolonged, they can kill the planet that hosts them.
Impactors strike during the reign of the dinosaurs (image credit: MasPix/devianart)
For decades scientists have believed that an asteroid impact event ended the era of the dinosaurs 66 million years ago. Now, analysis from the crater site itself seals the deal: the same elements that were deposited around the world from the impact have been found inside the crater itself.
This illustration shows the percentage of marine animals that went extinct during Earth's worst extinction at the end of the Permian era by latitude, from the model (black line) and from the fossil record (blue dots).A greater percentage of marine animals survived in the tropics than at the poles. The color of the water shows the temperature change, with red being most severe warming and yellow less warming. At the top is the supercontinent Pangaea, with massive volcanic eruptions emitting carbon dioxide. The images below the line represent some of the 96 percent of marine species that died during the event. [Includes fossil drawings by Ernst Haeckel/Wikimedia; Blue crab photo by Wendy Kaveney/Flickr; Atlantic cod photo by Hans-Petter Fjeld/Wikimedia; Chambered nautilus photo by John White/CalPhotos.]Justin Penn and Curtis Deutsch/University of Washington
Humanity can have a love/hate relationship with itself, but there’s no denying that we’re the pinnacle of evolution on Earth as things stand now. But it took an awfully long time for evolution to produce beings such as we. Several times, life had to drag itself back from near annihilation.
The largest extinction setback was the Permian-Triassic extinction, also called the “Great Dying,” some 252 million years ago. Up to 96% of all marine species and 70% of terrestrial vertebrate species went extinct.
A case study of the inhabitants of Easter Island served in part as the basis for a mathematical model showing the ways a technologically advanced population and its planet might develop or collapse together. Credit: University of Rochester illustration / Michael Osadciw
Welcome back to our Fermi Paradox series, where we take a look at possible resolutions to Enrico Fermi’s famous question, “Where Is Everybody?” Today, we examine the possibility that we haven’t heard from aliens because intelligent life only survives for so long.
In 1950, Italian-American physicist Enrico Fermi sat down to lunch with some of his colleagues at the Los Alamos National Laboratory, where he had worked five years prior as part of the Manhattan Project. According to various accounts, the conversation turned to aliens and the recent spate of UFOs. Into this, Fermi issued a statement that would go down in the annals of history: “Where is everybody?“
This became the basis of the Fermi Paradox, which refers to the disparity between high probability estimates for the existence of extraterrestrial intelligence (ETI) and the apparent lack of evidence. Since Fermi’s time, there have been several proposed resolutions to his question, which include the possibility that civilizations only have a “Brief Window” with which to communicate with the cosmos before going extinct.
The Mount Redoubt volcano in Alaska. Image Credit: By R. Clucas - http://pubs.usgs.gov/dds/dds-39/album.html and http://gallery.usgs.gov/photos/03_29_2013_otk7Nay4LH_03_29_2013_5#.UrvS2vfTnrc, Public Domain, https://commons.wikimedia.org/w/index.php?curid=5768911
200 million years ago, a mass extinction event wiped out about 76% of all species on Earth—both terrestrial and marine. That event was called the end-Triassic extinction, or the Jurassic-Triassic (J-T) extinction event. At that time, the world experienced many of the same things as Earth is facing now, including a warming climate and the acidification of the oceans.
A new paper shows that pulses of volcanic eruptions were responsible, and that those pulses released the same amount of CO2 as humans are releasing today.
Artist's concept of a large asteroid passing by the Earth-Moon system. Credit: A combination of ESO/NASA images courtesy of Jason Major/Lights in the Dark.
It’s become something of an action movie cliche: an asteroid is hurling towards Earth, its impact will cause a mass extinction, and the only hope for humanity is a ragtag group of astronauts and average Joes who will fly to the asteroid and blow it to pieces using nukes. The idea has been explored so many times by Hollywood that it seems like this is actually something space agencies have planned.
And in truth, they are, though the execution may be a little more sophisticated. For decades, space agencies have considered various methods for destroying asteroids that threaten Earth. But according to a new study led by researchers from John Hopkins University, incoming asteroids may be harder to break apart than we thought.
This illustration shows the percentage of marine animals that went extinct during Earth's worst extinction at the end of the Permian era by latitude, from the model (black line) and from the fossil record (blue dots).A greater percentage of marine animals survived in the tropics than at the poles. The color of the water shows the temperature change, with red being most severe warming and yellow less warming. At the top is the supercontinent Pangaea, with massive volcanic eruptions emitting carbon dioxide. The images below the line represent some of the 96 percent of marine species that died during the event. [Includes fossil drawings by Ernst Haeckel/Wikimedia; Blue crab photo by Wendy Kaveney/Flickr; Atlantic cod photo by Hans-Petter Fjeld/Wikimedia; Chambered nautilus photo by John White/CalPhotos.]Justin Penn and Curtis Deutsch/University of Washington
Everyone knows about the extinction of the dinosaurs. A cataclysmic asteroid strike about 66 million years ago (mya) caused the Death of the Dinosaurs. But there’ve been several mass extinctions in the Earth’s history, and they didn’t involve killer asteroids. The worst extinction was caused by a rapid rise in temperature.
Earth’s most severe extinction occurred long before the killer asteroid impact that wiped out the dinosaurs. It happened some 252 mya, and it marked the end of what’s called the Permian Period. The extinction is known as the Permian-Triassic Extinction Event, the End-Permian Extinction, or more simply, “The Great Dying.” Up to 70% of terrestrial vertebrates and up to 96% of all marine species were extinguished during The Great Dying.
Composite Spitzer, Hubble, and Chandra image of supernova remnant Cassiopeia A. A new study shows that a supernova as far away as 50 light years could have devastating effects on life on Earth. (NASA/JPL-Caltech/STScI/CXC/SAO)
There are a lot of ways that life on Earth could come to an end: an asteroid strike, global climate catastrophe, or nuclear war are among them. But perhaps the most haunting would be death by supernova, because there’s absolutely nothing we could do about it. We’d be sitting ducks.
New research suggest that a supernova’s kill zone is bigger than we thought; about 25 light years bigger, to be exact.
Iron in the Ocean
In 2016, researchers confirmed that Earth has been hit with the effects from multiple supernovae. The presence of iron 60 in the seabed confirms it. Iron 60 is an isotope of iron produced in supernova explosions, and it was found in fossilized bacteria in sediments on the ocean floor. Those iron 60 remnants suggest that two supernovae exploded near our solar system, one between 6.5 to 8.7 million years ago, and another as recently as 2 million years ago.
Iron 60 is extremely rare here on Earth because it has a short half life of 2.6 million years. Any of the iron 60 created at the time of Earth’s formation would have decayed into something else by now. So when researchers found the iron 60 on the ocean floor, they reasoned that it must have another source, and that logical source is a supernova.
This evidence was the smoking gun for the idea that Earth has been struck by supernovae. But the questions it begs are, what effect did that supernova have on life on Earth? And how far away do we have to be from a supernova to be safe?
“…we can look for events in the history of the Earth that might be connected to them (supernova events).” – Dr. Adrian Melott, Astrophysicist, University of Kansas.
In a press release from the University of Kansas, astrophysicist Adrian Melott talked about recent research into supernovae and the effects they can have on Earth. “This research essentially proves that certain events happened in the not-too-distant past,” said Melott, a KU professor of physics and astronomy. “They make it clear approximately when they happened and how far away they were. Knowing that, we can consider what the effect may have been with definite numbers. Then we can look for events in the history of the Earth that might be connected to them.”
Earlier work suggested that a supernova kill zone is about 25-30 light years. If a supernova exploded that close to Earth, it would trigger a mass extinction. Bye-bye humanity. But new work suggests that 25 light years is an under-estimation, and that a supernova 50 light years away would be powerful enough to cause a mass extinction.
Supernovae: A Force Driving Evolution?
But extinction is just one effect a supernova could have on Earth. Supernovae can have other effects, and they might not all be negative. It’s possible that a supernovae about 2.6 million years ago even drove human evolution.
“Our local research group is working on figuring out what the effects were likely to have been,” Melott said. “We really don’t know. The events weren’t close enough to cause a big mass extinction or severe effects, but not so far away that we can ignore them either. We’re trying to decide if we should expect to have seen any effects on the ground on the Earth.”
Melott and his colleagues have written a new paper that focuses on the effects a supernova might have on Earth. In a new paper titled “A SUPERNOVA AT 50 PC: EFFECTS ON THE EARTH’S ATMOSPHERE AND BIOTA”, Melott and a team of researchers tried to shed light on Earth-supernova interactions.
The Local Bubble
There are a number of variables that come into play when trying to determine the effects of a supernova, and one of them is the idea of the Local Bubble. The Local Bubble itself is the result of one or more supernova explosion that occurred as long as 20 million years ago. The Local Bubble is a 300 light year diameter bubble of expanding gas in our arm of the Milky Way galaxy, where our Solar System currently resides. We’ve been travelling through it for the last five to ten million years. Inside this bubble, the magnetic field is weak and disordered.
Melott’s paper focused on the effects that a supernova about 2.6 million years ago would have on Earth in two instances: while both were within the Local Bubble, and while both were outside the Local Bubble.
The disrupted magnetic field inside the Local Bubble can in essence magnify the effects a supernova can have on Earth. It can increase the cosmic rays that reach Earth by a factor of a few hundred. This can increase the ionization in the Earth’s troposphere, which mean that life on Earth would be hit with more radiation.
Outside the Local Bubble, the magnetic field is more ordered, so the effect depends on the orientation of the magnetic field. The ordered magnetic field can either aim more radiation at Earth, or it could in a sense deflect it, much like our magnetosphere does now.
Focusing on the Pleistocene
Melott’s paper looks into the connection between the supernova and the global cooling that took place during the Pleistocene epoch about 2.6 million years ago. There was no mass extinction at that time, but there was an elevated extinction rate.
According to the paper, it’s possible that increased radiation from a supernova could have changed cloud formation, which would help explain a number of things that happened at the beginning of the Pleistocene. There was increased glaciation, increased species extinction, and Africa grew cooler and changed from predominantly forests to semi-arid grasslands.
Cancer and Mutation
As the paper concludes, it is difficult to know exactly what happened to Earth 2.6 million years ago when a supernova exploded in our vicinity. And it’s difficult to pinpoint an exact distance at which life on Earth would be in trouble.
But high levels of radiation from a supernova could increase the cancer rate, which could contribute to extinction. It could also increase the mutation rate, another contributor to extinction. At the highest levels modeled in this study, the radiation could even reach one kilometer deep into the ocean.
There is no real record of increased cancer in the fossil record, so this study is hampered in that sense. But overall, it’s a fascinating look at the possible interplay between cosmic events and how we and the rest of life on Earth evolved.
Computer generated simulation of an asteroid strike on the Earth. Credit: Don Davis/AFP/Getty Images
For decades, scientists have debated the cause of the mass extinction that wiped out the dinosaurs and other life 65 million years ago. While the majority of researchers agree that a massive asteroid impact at Chicxulub, Mexico is the culprit, there have been some dissenters. Now, new research is questioning just a portion of the asteroid/Cretaceous-Paleogene extinction scenario. While the scientists involved in the study don’t doubt that such an asteroid impact actually happened, their research shows it is just not possible that vast global firestorms could have ravaged our planet and be the main cause of the extinction.
Researchers from the University of Exeter, University of Edinburgh and Imperial College London recreated the vast energy released from a 15-km wide asteroid slamming into Earth, which occurred around the time that dinosaurs became extinct.
They found that close to the impact site — a 180 km wide crater in Mexico — the heat pulse would have lasted for less than a minute. This intense but short-lived heat, the team says, could not have ignited live plants, challenging the idea that the impact led to global firestorms.
However, they did find that the effects of the impact would actually be worse on the other side of the planet, where less intense but longer periods of heat could have ignited live plant matter.
“By combining computer simulations of the impact with methods from engineering we have been able to recreate the enormous heat of the impact in the laboratory,” said Dr. Claire Belcher from the University of Exeter. “This has shown us that the heat was more likely to severely affect ecosystems a long distance away, such that forests in New Zealand would have had more chance of suffering major wildfires than forests in North America that were close to the impact. This flips our understanding of the effects of the impact on its head and means that palaeontologists may need to look for new clues from fossils found a long way from the impact to better understand the mass extinction event.”
The Cretaceous-Paleogene extinction was one of the biggest in Earth’s history and geologic evidence of the impact has been discovered in rock layers around the world from this time period. Some critics of the asteroid impact theory as a cause of the extinction have pointed to some of the microfossils from the Gulf of Mexico that show the impact occurred well before the extinction and could not have been its primary cause. Others point to volcanism that produced the Deccan traps of India around this time as a possible cause of the extinction.
But multiple models have showed such an impact would have instantly caused devastating shock waves, tsunamis, and the release of large amounts of dust, debris and gases that would have led to a low light levels and a prolonged cooling of Earth’s surface. The darkness and a global winter would have decimated the planet life and the dependent animals.
So while fire and brimstone may not have played a big role in the Cretaceous-Paleogene extinction, there was plenty of destruction and mayhem for the resulting extinction of more than 70% of known species.
Here’s a video from the researchers that shows their findings that close to the impact site, the heat pulse was too short to ignite live plant material.
![This illustration shows the percentage of marine animals that went extinct during Earth's worst extinction at the end of the Permian era by latitude, from the model (black line) and from the fossil record (blue dots).A greater percentage of marine animals survived in the tropics than at the poles. The color of the water shows the temperature change, with red being most severe warming and yellow less warming. At the top is the supercontinent Pangaea, with massive volcanic eruptions emitting carbon dioxide. The images below the line represent some of the 96 percent of marine species that died during the event. [Includes fossil drawings by Ernst Haeckel/Wikimedia; Blue crab photo by Wendy Kaveney/Flickr; Atlantic cod photo by Hans-Petter Fjeld/Wikimedia; Chambered nautilus photo by John White/CalPhotos.]Justin Penn and Curtis Deutsch/University of Washington](https://www.universetoday.com/wp-content/uploads/2018/12/Penn_sumfig_final.jpg)
