Comets


Info

Hiawatha crater in Greenland older than thought

Greenland Ice Sheet
© Pierre BeckFieldwork at the edge of the Greenland Ice Sheet in 2019.
Danish and Swedish researchers have dated the enormous Hiawatha impact crater, a 31 km-wide asteroid crater buried under a kilometer of Greenlandic ice. The dating ends speculation that the asteroid impacted after the appearance of humans and opens up a new understanding of Earth's evolution in the post-dinosaur era.

Ever since 2015, when researchers at the University of Copenhagen's GLOBE Institute discovered the Hiawatha impact crater in northwestern Greenland, uncertainty about the crater's age has been the subject of considerable speculation. Could the asteroid have slammed into Earth as recently as 13,000 years ago, when humans had long populated the planet? Could its impact have catalyzed a nearly 1,000-year period of global cooling known as the Younger Dryas?

New analyses performed on grains of sand and rocks from the Hiawatha impact crater by the Natural History Museum of Denmark and the GLOBE Institute at the University of Copenhagen, as well as the Swedish Museum of Natural History in Stockholm, demonstrate that the answer is no. The Hiawatha impact crater is far older. In fact, a new study published in the journal Science Advances today reports its age to be 58 million years old.

"Dating the crater has been a particularly tough nut to crack, so it's very satisfying that two laboratories in Denmark and Sweden, using different dating methods arrived at the same conclusion. As such, I'm convinced that we've determined the crater's actual age, which is much older than many people once thought," says Michael Storey of the Natural History Museum of Denmark.

Telescope

2nd 'Trojan Asteroid' confirmed orbiting with Earth

The second Earth Trojan asteroid
© NOIRLab/NSF/AURA/J. da Silva/Spaceengine Acknowledgment: M. Zamani (NSF’s NOIRLab))The second Earth Trojan asteroid known to date will remain Trojan — that is, it will be located at the Lagrangian point — for 4,000 years.
Asteroid 2020 XL5 will be Earth's buddy for the next 4,000 years.

A rocky body spotted orbiting in Earth's path is a "Trojan asteroid" that escorts our planet around the sun, astronomers have confirmed.

Asteroid 2020 XL5 is the second Trojan asteroid ever discovered. It's three times larger than the only other known Earth Trojan, called Asteroid 2010 TK7, which was confirmed in 2011. These small space rocks orbit along with Earth, but they are hard to spot from our planet — Asteroid 2010 TK7 is sometimes on the other side of the sun from us. They sit in gravitational sweet spots known as Lagrangian points. If Earth and the sun make up two points of an equilateral triangle, the Lagrangian point would be that triangle's third point. Earth and the sun have five of these points.

The newfound Trojan is at a Lagrangian point that has it orbiting ahead of Earth in the two bodies' shared path and the asteroid will stay there for 4,000 more years, researchers reported Tuesday (Feb. 1) in the journal Nature Communications. The asteroid is probably about 0.7 miles (1.18 kilometers) in diameter, though that estimate may be off if the surface of the asteroid is more or less reflective than astronomers assume.

Comment: See also:


Info

Comet's fiery destruction led to downfall ancient Hopewell

UC researchers find evidence of cosmic cataclysm 1,500 years ago at 11 ancient sites.
UC Researchers
© Larry SandmanUniversity of Cincinnati researchers take sediment samples at a Hopewell site at the confluence of the Ohio and Great Miami rivers. From left they are anthropology student Louis Herzner, biology student Stephanie Meyers, anthropology professor Kenneth Tankersley and UC geology alumnus Stephen Meyers.
The rapid decline of the Hopewell culture about 1,500 years ago might be explained by falling debris from a near-Earth comet that created a devastating explosion over North America, laying waste to forests and Native American villages alike.

Researchers with the University of Cincinnati found evidence of a cosmic airburst at 11 Hopewell archaeological sites in three states stretching across the Ohio River Valley. This was home to the Ohio Hopewell, part of a notable Native American culture found across what is now the eastern United States.

The comet's glancing pass rained debris down into the Earth's atmosphere, creating a fiery explosion. UC archaeologists used radiocarbon and typological dating to determine the age of the event.

The airburst affected an area bigger than New Jersey, setting fires across 9,200 square miles between the years A.D. 252 and 383. This coincides with a period when 69 near-Earth comets were observed and documented by Chinese astronomers and witnessed by Native Americans as told through their oral histories.

The study was published in the Nature journal Scientific Reports.

Fireball 2

When it comes to mass extinction, meteorite size doesn't matter

New research shows it's the composition of the rock a meteorite hits, and not the impactor's size, that causes an extinction-level event.
Near-Earth objects pass by our planet in this artist's rendering.
© ESA - P.CarrilNear-Earth objects pass by our planet in this artist's rendering.
It's a well-known story in our planet's past: A giant space rock slams into Earth, causing a catastrophe that ends in mass extinction. You might think that when it comes to determining which hits will cause such widespread devastation, the size of the incoming impactor is what matters. But new research suggests that something else might matter more: The composition of the ground where that meteorite hits.

The work, published Dec. 1, 2021, in Journal of the Geological Society, focuses on explaining why some meteorite impacts cause mass extinctions, while others don't. For example, the famous impact that killed the dinosaurs and left the Chicxulub crater was much smaller than many other impact events that didn't cause massive loss of species. Why might this be?

Info

Is the Eye of the Sahara 'the Lost City of Atlantis'?


Comment: Short answer; no it is not. It's an impact site (caused by an overhead cometary explosion)...


Atlantis and Richat Structure
© Chubbinsure Net
Could a curious geological formation in the Mauritanian part of the Sahara desert anything to do with the lost city of Atlantis?

If you type the word "Atlantis" into Google, around 120 million results will pop up. Obviously, Plato's legend of Atlantis has long occupied many people, from scientists to mysticists, with many candidates being cited as the possible location of this lost and sunken civilization. But did such a city ever exist at all? And if yes, where could the ruins be?

The only mention of Atlantis by name in historical texts is in Plato's Dialogues (written around 360 B.C.), which gives dozens of precise details about what Atlantis looked like, and where it may have been located in relation to other landmarks in the ancient world. It was this level of detail that has set many people off thinking that Atlantis actually existed.

One of the best clues that Plato gives about Atlantis is that there was a series of concentric circles around the city, black and red stone, and of course it was a seafaring society:
Poseidon carved the mountain where his love dwelt into a palace and enclosed it with three circular moats of increasing width, varying from one to three stadia and separated by rings of land proportional in size. The Atlanteans then built bridges northward from the mountain, making a route to the rest of the island. They dug a great canal to the sea, and alongside the bridges carved tunnels into the rings of rock so that ships could pass into the city around the mountain; they carved docks from the rock walls of the moats. Every passage to the city was guarded by gates and towers, and a wall surrounded each ring of the city. The walls were constructed of red, white, and black rock, quarried from the moats, and were covered with brass, tin, and the precious metal orichalcum, respectively.
So, according to Plato, Atlantis looked something like this:
Atlantis Artist Drawing
© Rocío Espín Piñar

Comment:

Watch Randall Carlson's discussion of the Richat Structure.




Comet 2

Comet Leonard, the brightest of the year, is fading and 'acting strange'

Comet Leonard
© ESA/NEOCCComet Leonard shines bright in this image from the European Space Agency's Near-Earth Object Coordination Centre using the Calar Alto Schmidt telescope in Spain. It was created by stacking 90 5-second exposure images of the comet taken on Dec. 7, 2021 on top of each other.
Something strange is happening to skywatchers' most anticipated comet of the year.

Astronomers first spotted what's been dubbed Comet Leonard in January 2021, and soon skywatchers were eagerly anticipating December and January, when the comet was due to pass by first Earth, then the sun. But by late November, observers noticed something strange. The comet should be getting brighter as it approaches the sun — and it is, but apparently only because it's getting closer to Earth, not because it's becoming inherently brighter.

Instead, it seems to be fading.

Comment: Another image of Comet Leonard from the 5th December shows it with "2 streamers":

See also: And check out SOTT radio's:


Info

Study pinpoints timing of Chicxulub asteroid impact

Chicxulub Impact Event
© Florida Atlantic UniversitySpringtime, the season of new beginnings, ended the 165-million-year reign of dinosaurs and changed the course of evolution on Earth.
A groundbreaking study led by researchers at Florida Atlantic University and an international team of scientists conclusively confirms the time year of the catastrophic Chicxulub asteroid, responsible for the extinction of dinosaurs and 75 percent of life on Earth 66 million years ago. Springtime, the season of new beginnings, ended the 165-million-year reign of dinosaurs and changed the course of evolution on Earth. Results of the study, published in the journal Scientific Reports , greatly enhances the ability to trace the first stages of damage to life on Earth. FAU's Robert DePalma, senior author and an adjunct professor in the Department of Geosciences, Charles E. Schmidt College of Science, and a doctoral student at the University of Manchester; and Anton Oleinik, Ph.D., second author and an associate professor, FAU's Department of Geosciences, contribute to a major scientific advancement in the ability to understand the massive impact that brought an end to the dinosaurs.

"Time of year plays an important role in many biological functions such as reproduction, feeding strategies, host-parasite interactions, seasonal dormancy, and breeding patterns," said DePalma. "Hence, it is no surprise that the time of year for a global-scale hazard can play a big role in how harshly it impacts life. The seasonal timing of the Chicxulub impact has therefore been a critical question for the story of the end-Cretaceous extinction. Until now, the answer to that question has remained unclear."

For decades, it has been known that the cataclysmic Chicxulub asteroid impact hit the Yucatan peninsula 66 million years ago. The impact triggered the third-greatest extinction in Earth's history, dramatically changing global biomes in ways that directly relate to current global ecological crisis. Yet, the finer details of what happened after impact and how those events led to the third-worst mass-extinction in Earth's history remain very hazy.

The new study was a long-term effort that started in 2014 and applied a combination of traditional and cutting-edge techniques to piece together a trail of clues enabling identification of the season for the Chicxulub impact event. DePalma examined the Tanis research locality in southwestern North Dakota, one of the most highly detailed Cretaceous-Paleogene (KPg) boundary sites in the world, to understand the inner workings of the extinction event. The research provides important new data while building new academic bridges.

Comet 2

New study shows the largest comet ever observed was active at near-record distance

UMD astronomers discovered that comet Bernardinelli-Bernstein is among the most distant active comets from the sun, providing key information about its composition.
comet Bernardinelli-Bernstein
© NOIRLab/NSF/AURA/J. da Silva/SpaceengineThe Comet Bernardinelli-Bernstein (BB), represented in this artist rendition as it might look in the outer Solar System, is estimated to be about 1000 times more massive than a typical comet. The largest comet discovered in modern times, it is among the most distant comets to be discovered with a coma, which means ice within the comet is vaporizing and forming an envelope of dust and vapor around the comet’s core.
A new study by University of Maryland astronomers shows that comet Bernardinelli-Bernstein (BB), the largest comet ever discovered, was active long before previously thought, meaning the ice within it is vaporizing and forming an envelope of dust and vapor known as a coma. Only one active comet has been observed farther from the sun, and it was much smaller than comet BB.

The finding will help astronomers determine what BB is made of and provide insight into conditions during the formation of our solar system. The finding was published in The Planetary Science Journal on November 29, 2021.

"These observations are pushing the distances for active comets dramatically farther than we have previously known," said Tony Farnham, a research scientist in the UMD Department of Astronomy and the lead author of the study.

Knowing when a comet becomes active is key to understanding what it's made of. Often called "dirty snowballs" or "icy dirtballs," comets are conglomerations of dust and ice left over from the formation of the solar system. As an orbiting comet approaches its closest point to the sun, it warms, and the ices begin to vaporize. How warm it must be to start vaporizing depends on what kind of ice it contains (e.g., water, carbon dioxide, carbon monoxide or some other frozen compound).

Fireball 4

Asteroid-driven showers might be more common than previously thought

Asteroid Bennu
© NASA/Goddard/University of Arizona/Lockheed MartinBennu ejecting particles from its surface on Jan. 19, 2019.
Every day, thousands of small rocks — dust grain- to pebble-sized — cross paths with Earth's atmosphere and burn up. More organized collisions, known as meteor showers, are visible to us when the planet passes through whole clouds of rocky debris.

These fragments were long thought to come strictly from comets whose crusts had been heated by the Sun and cracked open. But early in 2019, NASA's OSIRIS-Rex spacecraft (short for Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) captured images from the near-Earth asteroid Bennu that flipped that line of thinking on its head.

The images showed small bits of rock launching off the asteroid's surface. Some of the rock fell back to the surface and some went into orbit around Bennu for several days, but about 30 percent was ejected with enough speed that its pieces escaped the asteroid's gravity and began to orbit around the Sun.

"This was surprising," says Robert Melikyan, a graduate student at the University of Arizona's Lunar and Planetary Laboratory. "Bennu doesn't have a lot of volatile material that can heat up and break up the way comets do."

Melikyan and a team of researchers modeled the evolution of the asteroid's dust cloud in a study published in the Journal of Geophysical Research: Planets earlier this year and found that the particles both spread out around Bennu's orbit and follow a similar elliptical path around the Sun.

Comet 2

Signs of a Tunguska like event in Chile 12000 years ago

Halley's Comet
© Wikimedia
Hello and welcome! My name is Anton and in this video, we will talk about a detection of a bolide explosion in Chile 12000 years ago.


Links:

Widespread glasses generated by cometary fireballs during the late Pleistocene in the Atacama Desert, Chile

81P/Wild