Tag Archives: impact

Asteroid that killed the dinosaurs hit at “deadliest possible” angle

New simulations from Imperial College London reveals that the gigantic lizards of old had the worst possible luck when the asteroid hit.

Image credits Ruben / Flickr.

The team’s work shows that the asteroid hit our planet at an angle of around 60 degrees, an incidence angle that caused the largest possible quantity of climate-altering gases to be released into the atmosphere. The impact vaporized billions of tons of sulfur, the team estimates, which blocked incoming sunlight and effectively plunged the Earth into a nuclear winter that killed 75% of life on the planet.

Hard-hitter

“Our simulations provide compelling evidence that the asteroid struck at a steep angle, perhaps 60 degrees above the horizon, and approached its target from the north-east,” says Professor Gareth Collins, of Imperial’s Department of Earth Science and Engineering, lead author of the paper describing the findings.

“We know that this was among the worst-case scenarios for the lethality on impact, because it put more hazardous debris into the upper atmosphere and scattered it everywhere — the very thing that led to a nuclear winter.”

The team used 3D impact simulations and geophysical data recovered from the site of the impact, now known as Chicxulub, to piece together the 66 million-year-old event.

They looked at the subsurface structure and shape of the impact crater and then simulated impact scenarios to see what combination of angle and direction would create a site that matched with Chicxulub. By using rock cores drilled from the crater, they could gauge the forces generated by the asteroid impact, helping them better control the simulation scenarios.

Another key piece of information was obtained by comparing the geometry of the crater to subsurface structures some 30 km beneath the crater. The relationship between the two — both created by the impact — helped the team estimate the direction of the impact and the incoming angle. These two structures were aligned in a southwest-northeast direction, the authors found.

The location Chicxulub.
Image credits Demetia / Flickr.

Simulated impacts at an angle of 60 degrees reproduced all of these observations almost exactly, they add.

That the upper geological layers around the Chicxulub crater (in present-day Mexico) contain a large amount of porous carbonate rocks, evaporite rocks, and are rich in water. Under the extreme conditions created by an asteroid impact, such rocks would have decomposed to release immense quantities of carbon dioxide, sulphur compounds, and water vapor into the atmosphere.

Sulphur, in particular, has a very strong and quick-acting cooling effect on climate (that’s why large volcanic eruptions can create cold stretches of time). Sulphur aerosols block incoming sunlight, which not only reduces the amount of heat incoming to the surface but also interferes with photosynthesis. The combination of climate upheaval and lack of food then leads to massive extinction events.

The incoming angle of 60 degrees was the worst possible scenario seen in the simulations, as it maximized the transfer of energy from this impact into adjacent rocks — in other words, it was the perfect angle to throw as much of them into the atmosphere as possible.

“Large craters like Chicxulub are formed in a matter of minutes, and involve a spectacular rebound of rock beneath the crater,” says co-author Dr. Thomas Davison, also of Imperial’s Department of Earth Science and Engineering. “Our findings could help advance our understanding of how this rebound can be used to diagnose details of the impacting asteroid.”

The team hopes that their findings can help us better understand why the impact proved so deadly and that they can help us better piece together the characteristics of past impact events and the asteroids responsible for them just by looking at the craters they formed.

The paper “A steeply-inclined trajectory for the Chicxulub impact” has been published in the journal Nature Communications.

Illustration of newly discovered immense crater in Greenland. Credit: Nasa/Cryospheric Sciences Lab/Natural History Museum of Denmark.

Scientists find huge 19-mile impact crater under Greenland’s ice sheet

Researchers recently identified a huge bowl-shaped crater measuring a staggering 19 miles (31 km) across under half a mile of Greenland ice. The immense crater was likely formed by the impact of a mile-wide iron meteorite, which must have unleashed 47,000,000 times the energy of the nuclear bomb dropped on Hiroshima at the very end of WWII. The biggest question on everybody’s mind right now is when it all happened.

Illustration of newly discovered immense crater in Greenland. Credit: Nasa/Cryospheric Sciences Lab/Natural History Museum of Denmark.

Illustration of the newly-discovered immense crater in Greenland. Credit: Nasa/Cryospheric Sciences Lab/Natural History Museum of Denmark.

Kurt Kjær, a Professor at the Natural History Museum of Denmark in Copenhagen, suspected an impact crater might be hidden away under Greenland’s ice after NASA radar images showed a massive depression of the bedrock beneath the Hiawatha glacier, in the northwestern part of the island.

In May 2016, one year after the satellite images were released, scientists flew over the glacier pointing a cutting-edge ice-penetrating radar onto the glacier to map the underlying rock. The 3-D images clearly show all the hallmarks of an impact crater — a 19.3-mile-wide circular feature with a rim around it and an elevated central region.

The crater’s basin is about 300 meters deep, suggesting it was perhaps made by a one-mile-wide meteorite. This immediately classes the impact site among the top 25 largest known craters on Earth. According to the researchers, the impact would have melted and vaporized approximately ~20 km3 of rock.

“There would have been debris projected into the atmosphere that would affect the climate and the potential for melting a lot of ice, so there could have been a sudden freshwater influx into the Nares Strait between Canada and Greenland that would have affected the ocean flow in that whole region,” co-author John Paden, Associate Professor of electrical engineering and computer science at Kansas University, told the AFP.

Kurt Kjær collecting sediment samples from the crater's dranage system. Credit: Natural History Museum Denmark.

Kurt Kjær collecting sediment samples from the crater’s drainage system. Credit: Natural History Museum Denmark.

The meteorite was likely mostly made of iron, judging from geochemical tests performed on particles of shocked quarts collected from a nearby floodplain.

“Beyond the grains in the sediment sample that we interpret to be possible ejecta, no ejecta layer associated with this structure has yet been identified. Despite the absence of such additional evidence, an impact origin for the structure beneath Hiawatha Glacier is the simplest interpretation of our observations,” the authors wrote in their new study.

Black triangles represent elevated rim picks from the radargrams, and the dark purple circles represent peaks in the central uplift. Credit: Science Advances.

Black triangles represent elevated rim picks from the radargrams, and the dark purple circles represent peaks in the central uplift. Credit: Science Advances.

When exactly did the impact actually takes place is not at all certain. Kjær and colleagues are confident that the crater is no older than 3 million years, the time when ice began to cover Greenland.

“The age of this impact crater is presently unknown, but from our geological and geophysical evidence, we conclude that it is unlikely to predate the Pleistocene inception of the Greenland Ice Sheet,” the authors wrote in the journal Science Advances

As for the lower limit, radar images show that the deepest layers of the glacier that are older than 12,000 years are very deformed compared to upper layers and are filled with lumps of rock. To be sure, researchers will have to use radiometric dating techniques on material from the crater — that means drilling through half a mile of ice. It might take a few years before this happens, however.

 

asteroid impact.

Dinosaurs might have still been alive today had apocalyptic asteroid fallen somewhere else 66 million years ago

asteroid impact.

Image Credit: NASA/Don Davis.

About 66 million years ago, a 6-mile-wide asteroid slammed into Chicxulub, now a gaping crater near the same-named city on Mexico’s Yucatan Peninsula. In the aftermath of the nuclear winter-like conditions that followed, about 75 percent of Earth’s species went extinct, including the whole family of dinosaurs (with the notable exception of birds’ ancestors). Two Japanese researchers argue, however, that had that asteroid fallen in some different spot on Earth, dinosaurs would have likely survived the ordeal.

What if …

This tragic event has remained permanently etched in the planet’s geological history, through a band called the K-T Boundary, which separates the Cretaceous and Tertiary periods in geologic history. According to research published this week by British researchers at Imperial College London found the asteroid impact was even more devastating than previously thought. Their sophisticated model suggests that the asteroid slammed into the planet with the force of 40,000 US nuclear warheads, all triggered in a matter of seconds.

The impact released about 325 gigatons of sulfur and 425 gigatons of carbon dioxide into the atmosphere, more than 10 times global human emissions of carbon dioxide in 2014.  The huge cloud of sulfur that loomed over the planet’s surface blocked the sun, causing a dramatic cooling. Earth’s average surface air temperature dropped by as much as a staggering 26 degrees Celsius (47 degrees Fahrenheit). The sub-freezing temperatures persisted for over three years — enough to destroy plant life and everything else up the food web.

All of this gloomy picture might have never happened had the asteroid fallen elsewhere on the planet, claim paleontologist Kunio Kaiho, of Tohoku University, and Naga Oshima, an atmospheric chemist at Japan’s Meteorological Research Institute.

According to calculations made by the two, only 13 percent of Earth’s surface is made up of rocks that could have burned off that much soot. A staggering 1.7 billion tons of fine-particle black carbon were ejected into the atmosphere following the Chicxulub impact, the authors wrote in the journal Scientific Reports.

Scientists reconstructed a map of areas around the world with a high probability of being rich in hydrocarbon-bearing sedimentary rocks at the end of the Cretaceous. For dinosaurs to be alive today, all that was required was for that cataclysmic asteroid to fall somewhere away from such area, in the rest of the 87 percent of the planet’s surface. Indeed, based on the maps, even a few hundred miles away would have sufficed.

In other words, the Japanese scientists argue, the mass extinction event from 66 million years ago was of low probability. Unfortunately for dinosaurs (and fortunately for humans and their mammalian relatives), they drew the short straw. To be fair, it would still have been incredibly devastating for life on Earth even otherwise but not quite as rough as it was.

It’s interesting to note the implications that this study has for life on Earth in the future. According to NASA’s Near Earth Object Program, there’s a significant risk Earth could be impacted by a killer asteroid. Scientists are busy tracking and mapping all the objects in the solar system and beyond that could one day enter a collision course with Earth. At the end of the day, we can sleep maybe a bit more soundly knowing that an asteroid is not likely to reach its maximum damaging potential — though history showed it sure could.

Mistastin lake.

Gemstones prove asteroid impact was the hottest event ever recorded on Earth

Snow-clad Canada boasted, for the briefest of moments, the highest temperature ever recorded on Earth. The blistering event, clocking in at some 2370°C (4300°F), was the product of a chunk of space rock crashing down on the planet. Researchers looking into the event say we had no idea “real rocks can get that hot,” underscoring how devastating meteorite impacts can be.

Mistastin lake.

Image credits Jcmurphy / Wikimedia.

Some 40 million years ago in what we now call Canada, an otherworldly visitor was dropping in for a visit. This meteorite crashed with such speed and force that it heated rocks at the impact site to over half the temperature of the Sun’s surface — some 2370°C (4300°F). This event, which has the distinction of being the highest temperature witnessed on our planet, was recorded in gemstones formed under that immense release of heat.

Falling skies

Impacts between space-faring matter and the Earth release a monumental amount of energy — which leads to some mind-bogglingly high temperatures developing in the collision zone. In fact, the more energetic of such impacts (those which involved larger pieces of space rock) shaped the planet into what we know today. They affect the chemical makeup of the atmosphere and crust, directly playing a part in Earth’s habitability, and could even have created the Moon.

Pinning an actual number on these temperatures, however, is a tricky proposition. For one, notable impacts took place a very long time ago, on the order of millions of years. Secondly, because they’re near apocalyptic events, shock waves released during impacts tend to literally vaporize both the meteorites and the rocks they hit. Which is really bad news if you’re trying to analyze those rocks and estimate how much heat they were subjected to.

So researchers have an idea of the upper extremes these temperatures can reach — estimated to be well over 2000°C (3632°F) — but no way to refine that estimate since there’s no geological evidence to test it against. After all, you’d need something that can shrug off an event of such magnitude it turns rocks into thin air.

Thankfully, a team led by Nicholas Timms, a senior researcher and lecturer of Geology at the Curtin University in Perth, Australia, has found one such substance. Their work focused on the 28-kilometer (17.4 miles) wide Mistastin Lake crater in Labrador, Canada, estimated to have been the site of a violent impact some 40 million years ago. The team reports that there was enough energy released during the impact to fuse rock-borne zircon into gem-like cubic zirconia, whose minimum formation temperature is 2370 °C.

“These new results underscore just how extreme conditions can be after asteroids strike,” Timms says.

“Nobody has even considered using zirconia as a recorder of temperatures of impact melts before. This is the first time that we have an indication that real rocks can get that hot.”

The finding showcases how extreme conditions can become in the few minutes after an asteroid impact, and offer us a sort of benchmark for shelters if we’re ever faced with such an event — for which we may be long overdue.

It also helps offer us a glimpse into the environment of early Earth, which was constantly and repeatedly bombarded from space. The team says these impacts could have churned the crust enough to keep hydrogen, carbon, and sulfur in circulation in the atmosphere. These elements are fundamental to life as we know it (you need to mix both hydrogen and oxygen to get water). However, they point out that too severe a bombardment would have negatively impacted the planet’s climate and chemical balance, making it less habitable in the long run.

The paper “Cubic zirconia in >2370 °C impact melt records Earth’s hottest crust” has been published in the journal Earth and Planetary Science Letters.

World’s largest asteroid impact zone found in Australia

Australian researchers have uncovered what might be the biggest impact asteroid impact zone in the world – at over 400 kilometers (250 miles)!

Image credit: A.Y. Glikson et al.

Naturally, the crater isn’t visible today, but geophysicists have found the impact’s scars deep below the surface. Lead researcher Dr Andrew Glikson from the ANU School of Archaeology and Anthropology explains:

“The two asteroids must each have been over 10 kilometres across – it would have been curtains for many life species on the planet at the time,” said Dr Glikson.

The material from the two sites seems very similar, so this made geologists believe that they are actually part of the same huge asteroid, which probably broke in half upon entering the atmosphere. The drill actually recovered traces of rocks that had been turned to glass by the extreme temperature and pressure – a smoking gun for an asteroid hit.

The twin scars of the impact were discovered rather unexpectedly during drilling as part of geothermal research, in the Warburton Basin. The exact date of the impact remains unclear; the only solid information we have so far is that the surrounding rocks are between 300 and 450 million years old – but that’s quite a large uncertainty. Still, their findings seem to be consistent with previous geophysical studies.

“The pre-Upper Carboniferous ~ 450 × 300 km-large Warburton Basin, north-eastern South Australia, is marked by distinct eastern and western magnetic, gravity and low-velocity seismic tomography anomalies.”

Warburton East and West sub-basins, northeast South Australia; the Birdsville Track Ridge divides the Warburton East Basin from the Warburton West Basin. Image credit: A.Y. Glikson et al.

Warburton East and West sub-basins, northeast South Australia; the Birdsville Track Ridge divides the Warburton East Basin from the Warburton West Basin. Image credit: A.Y. Glikson et al.

These impacts may have had a more significant impact on life on Earth than is currently assumed.

“Large impacts like these may have had a far more significant role in the Earth’s evolution than previously thought,” Dr Glikson said.

However, unlike the meteorite that wiped out the dinosaurs and many other species 66 million years ago (and whose crater was found only in the 1970s), there seems to be no major extinction connected to this event, and no other geological phenomenon associated with it (such as increased volcanic activity for example).

“When we know more about the age of the impact, then we will know whether it correlates with one of the large mass extinctions [at the end of specific eras]. At this stage we do not have all the answers, but there has been a lot of interest and people are certainly interested in any impact on the dinosaurs.”

Magnetic modelling of the area also revealed bulges hidden deep in the Earth, rich in iron and magnesium, corresponding to the composition of the Earth mantle. The impact zones seem to impact throughout the entire Earth’s crust, all the way down to the mantle.

“There are two huge deep domes in the crust, formed by the Earth’s crust rebounding after the huge impacts, and bringing up rock from the mantle below,” Dr Glikson said.

Journal Reference: A.Y. Gliksona, A.J. Meixnere, B. Radke, I.T. Uysal, E. Saygin, J. Vickers, T.P. Mernagh. Geophysical anomalies and quartz deformation of the Warburton West structure, central Australia. doi:10.1016/j.tecto.2014.12.010