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Wed, 19 Jun 2019
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Comets


Fireball 5

Massive meteor fireball over Adelaide, Australia

A late night sight that definitely woke up countless residents!

Fireball over Adelaide
© YouTube/Caters Clips
Late last month, Australia's Adelaide experienced a spectacular and somewhat alarming sight as a fireball released a massive flare in the night sky before plummeting to Earth.

The meteor, captured on the Royal Adelaide Hospital's helipad camera, shined so bright that it made the sky appear to be in mid-sunrise at one point.

Info

Oldest meteorite collection on Earth found in the Atacama Desert

Meteorite recovery campaign
© Photo by Katherine Joy (University of Manchester)
Meteorite recovery campaign in the Atacama Desert (Nov. 2017).
Boulder, Colo., USA: Earth is bombarded every year by rocky debris, but the rate of incoming meteorites can change over time. Finding enough meteorites scattered on the planet's surface can be challenging, especially if you are interested in reconstructing how frequently they land. Now, researchers have uncovered a wealth of well-preserved meteorites that allowed them to reconstruct the rate of falling meteorites over the past two million years.

"Our purpose in this work was to see how the meteorite flux to Earth changed over large timescales-millions of years, consistent with astronomical phenomena," says Alexis Drouard, Aix-Marseille Université, lead author of the new paper in Geology.

To recover a meteorite record for millions of years, the researchers headed to the Atacama Desert. Drouard says they needed a study site that would preserve a wide range of terrestrial ages where the meteorites could persist over long time scales.
Meteorite in Atacama Desert
© Photo by Jérôme Gattacceca (CEREGE)
Meteorite with thin, dark, fusion crust in the Atacama Desert.
While Antarctica and hot deserts both host a large percentage of meteorites on Earth (about 64% and 30%, respectively), Drouard says, "Meteorites found in hot deserts or Antarctica are rarely older than half a million years." He adds that meteorites naturally disappear because of weathering processes (e.g., erosion by wind), but because these locations themselves are young, the meteorites found on the surface are also young.

"The Atacama Desert in Chile, is very old ([over] 10 million years)," says Drouard. "It also hosts the densest collection of meteorites in the world."

Comet

Taurid comet debris may raise chances of impacts on Earth in June

Tunguska Event
© Western University
An expedition in 1929 discovered the extent of the damage caused by the Tunguska Event in 1908.
A new study from Western University posits proof to the possibility that an oncoming swarm of meteors - likened to the Loch Ness Monster and Bigfoot by some extraterrestrial experts - may indeed pose an existential risk for Earth and its inhabitants. (That's us.)

When considering catalysts for catastrophic collision, there are two main sources Near Earth Objects (NEOs) like asteroids and meteoroids and interlopers from the outer solar system, which are typically comets. Over the past few decades, a great deal of effort has been expended in cataloguing more than 90 per cent of the potentially hazardous NEOs, and work is ongoing to detect, catalogue and track greater numbers and smaller sizes of these objects. Interlopers from the outer solar system are much harder to chart but again, much work is underway.

The Taurid swarm is a third potential source of risk that changes the probabilities of possible catastrophic impacts. The Tunguska (Russia) explosion of 1908 is considered a one-in-1000-year event, assuming a random distribution of events over time. But the Taurid swarm, a dense cluster within the Taurid meteoroid stream, and through which the Earth periodically passes, changes the odds significantly and gives a possible reason for the unlikely occurrence that a once per 1000-year event occurred just over a century ago. If the hypothesized might of the Taurid swarm is successfully proven, this also heightens the possibility of a cluster of large impacts over a short period of time.

Comet

'Oumuamua was a fragment from a disintegrated comet

Oumuamua
© ESO / M. Kornmesser
One artist's impression shows ʻ1I/'Oumuamua as a cigar-shaped object.
'Oumuamua's strange trajectory back out to interstellar space can be explained if the object was a comet fragment with the density of air.

'1/'Oumuamua, the interstellar mystery object that briefly visited the inner solar system in 2018, has proven a difficult nut to crack. Astronomers are still arguing about what it even is - asteroid, comet, or something else altogether? Now, in a pair of studies posted recently on the arXiv (paper 1, paper 2), Zdenek Sekanina (JPL-Caltech) suggests the object might be an ultra-low density fragment from a comet that disintegrated while passing near the Sun.

Info

New study confirms Libyan Desert Glass formed by airburst

Libyan Desert
© Associated Press
In the remote desert of western Egypt, near the Libyan border, lie clues to an ancient cosmic cataclysm.

Libyan desert glass is the name given to fragments of canary-yellow glass found scattered over hundreds of kilometres, between giant shifting sand dunes.

Interest in Libyan desert glass goes back more than 3,000 years. Among items recovered from King Tut's burial chamber is a gold and jewel-encrusted breastplate. In the centre sits a beautiful scarab beetle, carved from Libyan desert glass.

Libyan desert glass - raw and carved - is easily available today, but how the glass formed has long puzzled scientists.

Our research has found the answer.

Fireball 2

Meteor fireball lights up Northern New Zealand's sky

Meteor Over NZ
© ABC
Kiwis and Australians witnessed a short but stunning light show as a meteor burnt up in the atmosphere just after midnight.
Kiwis and Australians witnessed a short but stunning light show in our skies this morning as a meteor burnt up in the atmosphere just after midnight.

At around 12.25am Northlanders were woken to a flight of light, a deep rumbling and a flash of colour flying off the burning meteor.

Locals took to social media to describe what they saw and heard, with many revealing they thought it was a supersonic aircraft.

"It was a meteor. I saw it really close overhead at Oromahoe shortly after midnight. I could see green, yellow, orange flames coming off the rock as it burnt up," described one Northlander.

"It was very close and incredibly bright and afterwards there was a long rumbling sound. It was certainly bright enough to be seen at Paihia and Kaikohe."

Comet 2

New Comet C/2019 J1 (Lemmon)

CBET 4625 & MPEC 2019-J122, issued on 2019, May 12, announce the discovery of a comet (magnitude ~17.5) in the course of the "Mt. Lemmon Survey" (G96), in images taken on 2019, May 04 with a 1.5-m reflector + 10K CCD. This object was reported as a comet by R. A. Kowalskiand D. Rankin (G96, May 4). The new comet has been designated C/2019 J1 (Lemmon).

I performed follow-up measurements of this object while it was still on the PCCP webpage. Stacking of 12 unfiltered exposures, 120 seconds each, obtained remotely on 2019, May 06.4 from H06 (iTelescope network) through a 0.25-m f/3.4 reflector + CCD, shows that this object is a comet with a diffuse coma about 10 arcsec in diameter.

My confirmation image (click on it for a bigger version)

Comet C/2019 Lemmon
© Remanzacco Blogspot

Fireball 2

17 meteorites hit Earth everyday

Meteor Over Minsk
© SERGEI GAPON/AFP/Getty Images
A meteor crosses the night sky over a statue of Jesus Christ in the village of Ivye some 125 kilometres west of Minsk, in 2016.
Every year, the Earth is hit by about 6100 meteors large enough to reach the ground, or about 17 every day, research has revealed.

The vast majority fall unnoticed, in uninhabited areas. But several times a year, a few land in places that catch more attention.

Three months ago, for example, a small asteroid probably about the size of a minivan, flashed across the midday sky and exploded over western Cuba, showering the town of Viñales with falling rocks, some of which reportedly landed on rooftops.

Nobody was hurt, but it was a reminder that just as it's not safe to turn your back on the ocean for fear of being washed out to sea by an unusually large wave, space hazards are also capable of catching us by surprise.

To calculate how often such meteor falls occur, Gonzalo Tancredi, an astronomer at the University of the Republic in Montevideo, Uruguay, examined a database of incident reports, discovering that in the last 95 years people have directly observed 95 such events - an average of about eight per year.

To figure out how many others occur unobserved, Tancredi noted that people only occupy a tiny fraction of the Earth's surface - about 0.44% of its land area, or 0.13% of its total surface area.

That means that for every impact that is actually seen by someone, another 770 splash into the sea or fall in a desert, forest, or other locations so remote that nobody sees it happen.

"Some places on the Earth are heavily populated," Tancredi says, "but most places are very lowly populated."

Book 2

A Book Review - Prehistory Decoded

Gobekli Tepe
© Wikipedia Commons
Any follower of Catastrophism the last few years has seen extraordinary confirmations of ancient cataclysm and novel contributions to our way of thinking. To the Tusk, three revelations have characterized the period: The discovery of an extraordinarily youthful late Pleistocene crater in Greenland; a series of popular, comprehensive and unrefuted major journal articles which exquisitely defined hard evidence for the Younger Dryas impact catastrophe; and the singular contribution of Dr. Martin Sweatman, as made in his fabulous book, Prehistory Decoded.

Dr. Sweatman has done our planet and history a tremendous favor by writing Prehistory Decoded. By employing the hard science of probability, he has managed to demystify the world's very earliest and most mysterious art.

Prehistory Decoded begins by documenting Sweatman's initial discovery, reported worldwide in 2015, of an empirical method for decoding the world's first art using pattern matching and statistics. Guess what? The code is a memorial and date stamp for our favorite subject here: the Younger Dryas Catastrophe, and its associated Taurid meteor traumas.

Sweatman has managed to produce a synthesis explanation for the previously indecipherable succession of artistic animal figures at Gobekeli Tepe in Turkey, Chauvet Cave in France, Lascaux Cave in France, and Çatalhöyük in Turkey, among others. Unsurprisingly to the open minded, the ancient artists are communicating using a universally handy and persistent reference set: Stars. Or, more precisely, the appearance of constellations as adjusted over time according earth's precession.

(Don't you love the internet? One hyperlink and no need to explain all that!)

It seems reasonable then to the Tusk that, if there were a code, someone, somewhere, would break the code soon given the global availability and intense interest in the information. In fact, if I waited much longer without someone cracking it, the Tusk may have become convinced the oldest art is simply stunning cave paintings, and heavy carved rocks, with no relevant common narrative (other than horses are pretty, and moving rocks is cool).

Fireball 2

International space agencies team up to practice for an asteroid striking Earth

Asteroid Strike
© Pixabay
You've gotta hand it to America's space scientists: they're resilient. Despite an admission that they may not be able to stop the asteroid Bennu from turning Earth into a smoldering crater filled with the ashen remains of its human inhabitants, NASA's Planetary Defense Coordination Office (PDCO) has teamed up with FEMA and other agencies for what amounts to a wargaming exercise to prepare themselves for a catastrophic asteroid strike.

The best part of this? The ESA is tweeting out bits and pieces of the scenario - that an asteroid named 2019PDC has been spotted and calculated to have a 1 in 100 chance of striking Earth - as if it were happening in real time. The agency has wisely hashtagged the relevant tweets with #FICTIONALEVENT to avoid any War of the Worlds scenarios.