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Mon, 22 Apr 2019
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Comets


Fireball 2

SpaceX contracted by NASA to attempt to 'redirect' asteroid

Asteroids
© Pixabay

Despite an admission last year that it may be impossible to stop the 8.8 ton asteroid
Bennu from annihilating life on Earth, the perennial optimists at NASA have nevertheless granted SpaceX a $69 million contract to assist in the Double Asteroid Redirection Test (DART), intended to save Earth from interstellar armageddon. The test, tentatively scheduled for June 2021, will have Elon's Musketeers crashing a kinetic impactor - in this case, a spacecraft equipped with cameras and solar panels - into a small moonlet accompanying Didymos, an 800-meter-long near-Earth asteroid. NASA notes that the moonlet, dubbed "Didymoon" by scientists, "is more typical of the size of asteroids that could pose a more common hazard to Earth" than its massive chaperone.

The goal, NASA says, is to launch the DART spacecraft atop a SpaceX Falcon 9 rocket that will then make its way to Didymos and Didymoon to attempt to alter the latter's trajectory in a rehearsal for what could one day be a high-stakes game of cosmic bumper cars. "By using solar electric propulsion," NASA says, "DART will intercept the asteroid Didymos' small moon in October 2022, when the asteroid will be within 11 million kilometers of Earth." Meanwhile, Earthlings will watch with bated breath.

"The collision will change the speed of the moonlet in its orbit around the main body by a fraction of one percent," NASA promises, "enough to be measured using telescopes on Earth."

Info

'Morphospace' governs recovery after mass extinction

Mass Extinction Event
© MARK GARLICK/SCIENCE PHOTO LIBRARY/Getty Images
The re-establishment of species diversity following an extinction event is consistently slower than evolutionary theory predicts.
Theory tells us that after a mass extinction, an event where the diversity of species is drastically reduced, nature should rebound with a flurry of creativity. Species should quickly proliferate to refill desolate ecosystems, something called adaptive radiation.

Yet, the paleontological record suggests that this doesn't happen at anywhere near the expected pace. Now, research published in the journal Nature Ecology and Evolution argues that understanding something called "morphospace" might help us find the cause.

Extinction events happen with alarming regularity: there's the "big five", but a host of slightly smaller, yet still devastating extinctions have peppered the planet's history.

Scientists now worry that we might be in the middle of one of our own making, so this makes it all the more important to understand how the natural world bounces back from such catastrophes.

Perhaps the most well-known of the earth's mass extinctions is the Cretaceous-Paleogene (K-Pg) extinction event. This took place 66 million years ago when an asteroid smacked into the earth next to what is now the Yucatán Peninsula, creating the nearly 200-kilometre-wide depression known as the Chicxulub crater. This impact drove the extinction of all the non-avian dinosaurs, and much else besides.

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Meteor outburst detected in the Southern hemisphere

Meteor Portal
© NASA
Peter Jenniskens and Jack Baggaley announced today in CBET telegram 4617 that Ian Crumpton and Peter Aldous of CAMS NewZealand detected a brief outburst of 5 meteors from comet C/1907 G1 (Grigg-Mellish) on March 31 in the nine minutes between 17:36 and 17:45 UTC (see the CAMS radiant map for March 31). According to Jenniskens, this is the first instrumental evidence that this comet is a meteor shower parent, after visual observers long reported an annual shower named the delta Pavonids (IAU 120, DPA) radiating from the theoretical radiant of this comet.

The poorly observed comet could be of long period type (orbital period > 200 years), in which case the outburst is dust ejected in the previous return and future outbursts can now be predicted. If the comet is of Halley-type (orbital period 112-200 years), then the outburst could be from a number of different returns and the activity could signal the return of the comet.

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Streaking meteor fireball caught on dash-cam over Wisconsin

Meteor over Kenosha
© Screen Capture Youtube
A meteor entering the earth's atmosphere lit up the sky early Wednesday around 2 a.m.

For one motorist driving west of Kenosha, it appeared that the streaking fireball had crashed near the Strawberry Creek club house and housing development. His 911 call triggered a response from both the Kenosha and Bristol fire departments.

Pleasant Prairie Police. dashcam video is below

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Green meteor fireball captured by amateur photographer over Tasmania

Meteor over Tasmania
© Leoni williams
Residents in Tasmania's south captured the fast flash of light on camera.
They were waiting for the Aurora Australis, but amateur photographers were left guessing after seeing a bright green flash light up the Tasmanian sky.

Amateur photographer Leoni Williams captured a shot of the green streak about 9:30pm on Thursday by "accident".

Overlooking Pipe Clay Lagoon, toward Clifton Beach in southern Tasmania, Ms Williams had her camera facing south in anticipation of an Aurora.

"I was very lucky to capture this bright green object before it disappeared over the horizon," Ms Williams said.

"I'm still not sure what it was. I didn't actually see it with the naked eye as I wasn't watching. I had just set the camera on 30 seconds and pushed the shutter and turned back to my phone.
"I would imagine it was pretty quick. I nearly missed it because it was at the end of the exposure."
Photo sparked social media debate

Ms Williams took to social media to try and find out what she'd captured on camera.

Opinions varied, with some thinking it was a shooting star, a fallen satellite or even a UFO.

Spotted from the Huon Valley to Dodges Ferry, other photos began popping up on social media.

Eventually, it was shared on social media page Australian Meteor Reports.

"It's definitely a meteor," page administrator David Finlay said.
"That flash that's been captured is a very, very bright meteor - it's what we'd call a 'fireball'. It probably lit up the countryside."
Mr Finlay - a former industrial chemist who has been studying astronomy from an very early age - said the flash was created by a "small rock from space, blazing through the atmosphere, creating friction with the atmosphere".

"It glows and ionises gas - that's what you see as this fireball blazing through the sky.

"If it actually survives atmospheric entry and lands as a rock on land, that's what we call a meteorite - only if it makes it to the ground."

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Meteor fireball falls in Russia's territory

Meteor over Krasnoyarsk Territory
© REUTERS/Ilya Naymushin
A truck drives along the M54 federal highway on the bank of the Us river in the Western Sayan mountains in Krasnoyarsk region, Russia, November 4, 2016.
An eyewitness filmed a glowing falling object on his car DVR in the night sky, near the village of Tura in the north of Russia's Krasnoyarsk Territory.

Earlier, the Yenisei TV channel published a dashcam video, which showed a falling luminous body. It is reported that the incident occurred on Friday evening near the village of Tura.

Info

YDB team publishes evidence from Chile for global climate cataclysm

YDB World Map
© Cosmic Tusk
The main objective of this study was to test the YDB impact hypothesis by analyzing a wide range of data from the Pilauco site in southern Chile. The following conclusions show that our data and interpretations are consistent with the YDB impact hypothesis and we found no evidence that refutes the hypothesis.

(1) At Pilauco, ~12,800-year-old peaks in high-temperature Pt-rich and native-Fe spherules are comparable to similar impact-related evidence found at more than 50 YDB sites in North America, Europe, and western Asia. It appears that the YDB layer at Pilauco is coeval with similar layers found at these sites on several continents and is also possibly related to the proposed YDB impact event.

(2) Identification of the YDB layer at Pilauco greatly expands the proposed YDB proxy feld ~6,000 km farther south of the closest well-studied YDB site in Venezuela, and ~12,000 km south of the northernmost YDB site in Canada, a distance equaling ~30% of Earth's circumference.

(3) Cr-rich spherules are found in the YDB layer at Pilauco, but not found at the ~50 other sites on four continents, suggesting that one or more local impacts/airbursts occurred in the Cr-rich basaltic terrain
circa Pilauco.

Meteor

6th mass extinction and the 'Shiva hypothesis'

Imapct Event
© Live Science
A total of five mass extinctions occurred during the last 500 million history of the planet earth, when more than 75 per cent of existing life forms had gone extinct. Various causes have been ascribed for each of the five mass extinctions.

The most recent, 5th mass extinction took place about 66 million years ago, when a huge meteorite with a radius of about 10 km crashed on the earth and made a crater with 180 km diameter and 20 km deep in the Yucatan village, Chicxulubin Mexico. The impact created a doomsday scenario.

Superheated dust particles and steam filled the sky preventing sunlight to reach earth for decades killing plant life as they could not carry out photosynthesis. Many volcanoes around the earth became active and spewed lava. There were super-tsunamis drowning land animals and plants. The atmosphere of earth became unsuitable to support most of the existing life forms, leading to the extinction of dinosaurs.

Can the 6th mass extinction occur in a similar manner and all of us would disappear before we figure out what hit us? Michael Rampino and Bruce Haggerty (1984) proposed the 'Shiva hypothesis' (named after Lord Shiva, the Hindu God of destruction) based on an earlier paper of Napier and Clube (1979). According to this hypothesis, the earth experiences large impact events with comets every 30 million years when solar system crosses the plane of Milky Way galaxy. This causes gravitational disturbances in the cloud of comets (Oort cloud) surrounding the solar system and sends some of them hurling towards the inner solar system. These may be propelled to collide with the earth by the 'sling shot' gravitational action of Jupiter (NASA's Voyager-1 and 2 used this effect to escape Sun's gravity).

Modelling studies suggest that an object of 1 km size, depending upon its speed and angle of approach is enough to wipe out the humanity according to Rampino, who gave the 'Shiva hypothesis.' This could throw up enough pulverised rock to block the sun for months. The debris falling back on earth would cause wild fires increasing the surface temperature and killing everything living to death. The earth will then go through a process of cooling and a prolonged winter possibly creating new forms of life millions of years later.

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Asteroid much harder to destroy than previously thought

Impact Event
© MARK GARLICK/SCIENCE PHOTO LIBRARY/Getty Images
Past modelling for the effect of asteroid collisions has underestimated the force needed to bring about total destruction.
Asteroids are much harder to destroy than previously thought, new modelling shows.

The research, published in the journal Icarus, shows that an asteroid damaged in a collision - by another asteroid, for instance, or a nuclear missile fired at it in the blind hope that doing so will prevent it from smacking into the planet with catastrophic consequences - will substantially reconstruct itself because of the strong gravitational pull of its still-intact core.

The modelling, funded by NASA, substantially updates and contradicts earlier research that showed that a collision between a small asteroid and a large one would completely demolish the latter, the destruction facilitated by the rapid transit of cracks right through it.

The new study, conducted by Charles El Mir and KT Ramesh, of Johns Hopkins University, US, and Derek Richardson, of the University of Maryland, US, applies more fine-grain analysis and arrives at a distinctly different conclusion.

At issue, fundamentally, is the way rocks react to energetic impacts. This process is well understood at what can be called "laboratory scale", wherein real-world and simulated experiments use rocks roughly the size of a human fist.

But asteroids of a magnitude big enough to worry NASA scientists - or tempt would-be space-miners - are considerably larger than that. They might, indeed, be roughly the size of Berlin.

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Two previously unknown massive impact craters discovered

Impact Crater
© A. CAVOSIE
Hiding in plain sight: Morgan Cox (right) collecting breccia samples at the Yallalie impact site.
Researchers have discovered two previously unknown massive craters on Earth, the most recent estimated to have been produced by an impact only 800,000 years ago.

The craters - one in Western Australia and the other in Nicaragua - are revealed in a pair of papers published in the journal Meteoritics and Planetary Science.

In one sense, the Australian crater, in a location known as Yallalie, about 200 kilometres north of the state capital, Perth, has long been hiding in plain sight.

Buried deep beneath the surface, it was first tentatively identified as an impact site in 1992, after its discovery two years earlier during oil drilling exploration.

Subsequent studies of the 12-kilometre-wide circular formation, which also features a raised central structure three kilometres wide, identified it as the result of several meteorite impacts.