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Wed, 18 Sep 2019
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Comet 2

Spectacular Delta Aquariids meteor shower set to light up skies tonight

Meteor shower
© National Park Service
An annual meteor shower is set to peak tonight in a stunning night sky display that could see up to 20 flaming by per hour. Here's everything you need to know to catch the spectacular celestial show.

What?

The Delta Aquariids meteor shower is a spectacular display of what is essentially space dust and bits of debris from a comet (or comets) in our orbital path that flew close to the Sun.

The comet sheds particles that then smash into our atmosphere - around 60 miles above Earth - and zoom across our skies at about 90,000mph (150,000kph), at times vaporizing into shooting stars and leaving a trail of blazing light behind.

Comet 2

Impact hazard from disintegrating comets

Comet 73P
© NASA/JPL-Caltech/W.Reach [SSC/Caltech]
Last month, Bill Napier (co-creator of the coherent catastrophism theory, with Victor Clube) published his latest paper (MNRAS, vol. 488, p 1822-1827) on the impact hazard from disintegrating comets in the inner solar system. His focus is on a large 100 km comet in an Encke-like orbit. It is a sophisticated work that extends his earlier estimates, this time by combining explicit orbital simulations with a calibrated model of comet fragmentation (published by de Sisto et al. in 2009).

His aim, like mine in Prehistory Decoded, is to estimate the hazard to Earth from the kind of comet thought to have become trapped in our inner system a few tens of thousands of years ago. We know, pretty much, that this happened because of the massive zodiacal dust cloud and correlated fragments that remain in orbit.

He concludes that we can expect one or two impact collisions over the last 20,000 years, or so, with energy over 6000 Mt, and that this energy will likely be unevenly distributed across a hemispherical region. This is roughly 600 times the energy of the Tunguska impact, which itself was large enough to demolish one of our biggest modern-day cities (like Greater London).

This broadly supports my own estimates in Prehistory Decoded, based on simple fragmentation pathways and Opik's collision formula, where I find that we can expect one or two collisions with an energy of at least 10,000 Mt, and perhaps another ten with energy over 1,000 Mt, from the same sized comet over the same timescale. Great!

Fireball 5

Suspected meteorite crashes into rice field in India

Suspected Meteorite
© STR/AFP/Getty Images
The object was spotted ‘coming down from the sky’ and then excavated from a 150cm-deep hole by residents of Mahadeva village.
Madhubani/Patna: Farmers working in a paddy field at a village in Madhubani district were left shaken when a meteorite-like object weighing around 15kg fell from the sky, leaving a crater at the spot where it crashed.

Madhubani DM Shirsat Kapil Ashok told TOI that the incident took place around 2.30pm on Monday. "Agriculture labourers working the paddy field where the meteorite struck claimed that they saw a fireball-like object coming down from the sky and made a deep crater where it hit the ground. The farmers also saw smoke coming out from the spot in the water-filled agriculture field," Shirsat said.

Displaying the 'meteorite' wrapped in a red cloth on Tuesday morning, the Madhubani DM said the stone-like object has magnetic properties. He added that the mysterious object was kept secure in the treasury office at the Madhubani collectorate.

"I have written a letter to the principal secretary of the science and technology department along with a copy to the principal secretary of state art, culture and youth affairs department," Shirsat said, adding the sample was sent to Patna on Tuesday evening.

"The science and technology department will take a decision regarding further action. The object might be sent to space research organisations like ISRO or any museum," Shirsat said.

Fireball

Meteor fireball streaks across Australian skies

Fireball over Australia
© Screenshot YouTube
A screenshot from a YouTube video that is reportedly of the meteor that flew across the South East sky on the night of July 5.
Social media is buzzing with reports of a meteor spotted over the South Coast on Friday night.

On the Facebook group Australian Meteor Reports, administrator David Finlay said the meteor was spotted about 9pm on July 5 and believed it had come to ground somewhere in Victoria.

"I have reports of sonics from Forest Hill (Melbourne) to Mallacoota Vic. That's a distance of 400km. I've never heard of sonics being reported so far apart," he said in a Facebook post to the group.

He said sightings had been reported from as far north as Sydney and Orange.

"From these reports, and as long as this object was over land and not the ocean, I'm already predicting there are now meteorites on the ground somewhere in Victoria from this fall," he said.

Fireball 5

Nuke sensors detect asteroid explosion in the atmosphere over the Caribbean

Asteroid Explosion
© William Straka III/University of Wisconsin
On June 22nd at 21:25 UT, a small asteroid entered Earth's atmosphere and exploded in broad daylight south of Puerto Rico. Airwaves recorded by the Comprehensive Nuclear Test Ban Treaty Organization's infrasound station in Bermuda pegged the blast energy between 3 and 5 kilotons of TNT-a fraction of a WW II atomic bomb. The explosion was clearly visible in images from NOAA's GOES-16 weather satellite:


Meteor expert Peter Brown of the University of Western Ontario says the infrasound signal is consistent with a "small multi-meter sized near-Earth asteroid." According to data compiled by NASA's Center for Near Earth Object Studies, asteroids of this size and energy hit Earth's atmosphere about once a year. That means it's rare-but not exceptionally so.

Comet 2

ESA puts comet mission on fast track

Montezuma observing a comet.
© DEA / G. DAGLI ORTI/Getty Images
A sixteenth century illustration showing Montezuma observing a comet. The European Space Agency has a different plan.
Scientists at the European Space Agency (ESA) are working on a new "fast" mission to make the first flyby of a pristine comet - meaning one that has never before passed close to the sun.

Since the first comet mission, all the way back in 1978, numerous space agencies have made more than a dozen comet flybys, including one rendezvous and landing.

But never before has a mission attempted to visit a comet on its first plunge toward the sun, when its never-before-heated surface is almost unchanged from when it formed at the dawn of the solar system, some 4.5 billion years ago.

The recently approved mission, called Comet Interceptor, will also be unique in what it does as it nears its target.

Rather than simply flying by, it will split into four parts, each of which will whizz past the comet on a slightly different trajectory.

Three of these will be tiny instrument packages, which will view the comet from different angles. This will allow scientists back on Earth to create detailed 3D models not only of its surface, but of the gas, dust, and plasma surrounding it.

The fourth will be the mother ship, which will collect data from the smaller probes and relay it back to Earth.

"It's a novel concept," says Fabio Favata, head of the Strategy, Planning, and Coordination Office in ESA's Directorate of Science.

Details of the mission have yet to be determined, but the use of the word "fast" in its description doesn't mean it will be traveling at warp speed.

Fireball

Meteor fireball sends shockwaves over Queensland, Australia

meteor
Weather monitoring cameras have captured the moment a meteor exploded over Queensland, Australia on Saturday night (June 22)

According to the operator of the cameras, the blast at 10 pm sent shockwaves towards the Brisbane area.

A second camera showed the blast lighting the sky green above homes in the city of Ipswich.

Fireball 5

Massive meteor fireball last month turned night into day in 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.