Extraterrestrial stone brings first supernova clues to Earth

New chemistry 'forensics' indicate that the stone named Hypatia from the Egyptian desert could be the first tangible evidence found on Earth of a supernova type Ia explosion. These rare supernovas are some of the most energetic events in the universe.

This is the conclusion from a new study published in the journal Icarus, by Jan Kramers, Georgy Belyanin and Hartmut Winkler of the University of Johannesburg, and others.

Since 2013, Belyanin and Kramers have discovered a series of highly unusual chemistry clues in a small fragment of the Hypatia Stone.

In the new research, they eliminate 'cosmic suspects' for the origin of the stone in a painstaking process. They have pieced together a timeline stretching back to the early stages of the formation of Earth, our Sun and the other planets in our solar system.

A cosmic timeline

Their hypothesis about Hypatia's origin starts with a star: A red giant star collapsed into a white dwarf star. The collapse would have happened inside a gigantic dust cloud, also called a nebula.

That white dwarf found itself in a binary system with a second star. The white dwarf star eventually 'ate' the other star. At some point the 'hungry' white dwarf exploded as a supernova type Ia inside the dust cloud.

After cooling, the gas atoms which remained of the supernova Ia started sticking to the particles of the dust cloud.

"In a sense we could say, we have 'caught' a supernova Ia explosion 'in the act', because the gas atoms from the explosion were caught in the surrounding dust cloud, which eventually formed Hypatia's parent body," says Kramers.

A huge 'bubble' of this supernova dust-and-gas-atoms mix never interacted with other dust clouds.

Millions of years would pass, and eventually the 'bubble' would slowly become solid, in a 'cosmic dust bunny' kind of way. Hypatia's 'parent body' would become a solid rock some time in the early stages of formation of our solar system.

This process probably happened in a cold, uneventful outer part of our solar system -- in the Oort cloud or in the Kuiper belt.

At some point, Hypatia's parent rock started hurtling towards Earth. The heat of entry into earth's atmosphere, combined with the pressure of impact in the Great Sand Sea in south-western Egypt, created micro-diamonds and shattered the parent rock.

The Hypatia stone picked up in the desert must be one of many fragments of the original impactor.

"If this hypothesis is correct, the Hypatia stone would be the first tangible evidence on Earth of a supernova type Ia explosion. Perhaps equally important, it shows that an individual anomalous 'parcel' of dust from outer space could actually be incorporated in the solar nebula that our solar system was formed from, without being fully mixed in," says Kramers.

"This goes against the conventional view that dust which our solar system was formed from, was thoroughly mixed."

Three million volts for a tiny sample

To piece together the timeline of how Hypatia may have formed, the researchers used several techniques to analyse the strange stone.

In 2013, a study of the argon isotopes showed the rock was not formed on earth. It had to be extraterrestrial. A 2015 study of noble gases in the fragment indicated that it may not be from any known type of meteorite or comet.

In 2018 the UJ team published various analyses, which included the discovery of a mineral, nickel phosphide, not previously found in any object in our solar system.

At that stage Hypatia was proving difficult to analyse further. The trace metals Kramers and Belyanin were looking for, couldn't really be 'seen in detail' with the equipment they had. They needed a more powerful instrument that would not destroy the tiny sample.

Kramers started analysing a dataset that Belyanin had created a few years before.

In 2015, Belyanin had done a series of analyses on a proton beam at the iThemba Labs in Somerset West. At the time, Dr Wojciech Przybylowicz kept the three-million Volt machine humming along.

In search of a pattern

"Rather than exploring all the incredible anomalies Hypatia presents, we wanted to explore if there is an underlying unity. We wanted to see if there is some kind of consistent chemical pattern in the stone" says Kramers.

Belyanin carefully selected 17 targets on the tiny sample for analysis. All were chosen to be well away from the earthly minerals that had formed in the cracks of the original rock after its impact in the desert.

"We identified 15 different elements in Hypatia with much greater precision and accuracy, with the proton microprobe. This gave us the chemical 'ingredients' we needed, so Jan could start the next process of analysing all the data," says Belyanin.

Proton beam also rules out solar system

The first big new clue from the proton beam analyses was the surprisingly low level of silicon in the Hypatia stone targets. The silicon, along with chromium and manganese, were less than 1% to be expected for something formed within our inner solar system.

Further, high iron, high sulphur, high phosphorus, high copper and high vanadium were conspicuous and anomalous, adds Kramers.

"We found a consistent pattern of trace element abundances that is completely different from anything in the solar system, primitive or evolved. Objects in the asteroid belt and meteors don't match this either. So next we looked outside the solar system," says Kramers.

Not from our neighnourhood

Then Kramers compared the Hypatia element concentration pattern with what one would expect to see in the dust between stars in our solar arm of the Milky Way galaxy.

"We looked to see if the pattern we get from average interstellar dust in our arm of the Milky Way galaxy fits what we see in Hypatia. Again, there was no similarity at all," adds Kramers.

At this point, the proton beam data had also ruled out four 'suspects' of where Hypatia could have formed.

Hypatia did not form on earth, was not part of any known type of comet or meteorite, did not form from average inner solar system dust, and not from average interstellar dust either.

Not a red giant

The next simplest possible explanation for the element concentration pattern in Hypatia, would be a red giant star. Red giant stars are common in the universe.

But the proton beam data ruled out mass outflow from a red giant star too: Hypatia had too much iron, too little silicon and too low concentrations of heavy elements heavier than iron.

Nor a supernova Type II

The next 'suspect' to consider was a supernova type II. Supernovas of type II cook up a lot of iron. They are also a relatively common type of supernova.

Again, the proton beam data for Hypatia ruled out a promising suspect with 'chemistry forensics'. A supernova type II was highly unlikely as the source of strange minerals like nickel phosphide in the pebble. There was also too much iron in Hypatia compared to silicon and calcium.

It was time to closely examine the predicted chemistry of one of the most dramatic explosions in the universe.

Heavy metal factory

A rarer kind of supernova also makes a lot of iron. Supernovas of the type Ia only happen once or twice per galaxy per century. But they manufacture most of the iron (Fe) in the universe. Most of the steel on earth was once the element iron created by Ia supernovas.

Also, established science says that some Ia supernovas leave very distinctive 'forensic chemistry' clues behind. This is because of the way some Ia supernovas are set up.

First, a red giant star at the end of its life collapses into a very dense white dwarf star. White dwarf stars are usually incredibly stable for very long periods and most unlikely to explode. However, there are exceptions to this.

A white dwarf star could start 'pulling' matter off another star in a binary system. One can say the white dwarf star 'eats up' its companion star. Eventually the white dwarf gets so heavy, hot and unstable, it explodes in a supernova Ia.

The nuclear fusion during the supernova Ia explosion should create highly unusual element concentration patterns, accepted scientific theoretical models predict.

Also, the white dwarf star that explodes in a supernova Ia is not just blown to bits, but literally blown to atoms. The supernova Ia matter is delivered into space as gas atoms.

In an extensive literature search of star data and model results, the team could not identify any similar or better chemical fit for the Hypatia stone than a specific set of supernova Ia models.

Forensic elements evidence

"All supernova Ia data and theoretical models show much higher proportions of iron compared to silicon and calcium than supernova II models," says Kramers.

"In this respect, the proton beam laboratory data on Hypatia fit to supernova Ia data and models."

Altogether, eight of the 15 elements analysed conform to the predicted ranges of proportions relative to iron. Those are the elements silicon, sulphur, calcium, titanium, vanadium, chromium, manganese, iron and nickel.

Not all 15 of the analysed elements in Hypatia fit the predictions though. In six of the 15 elements, proportions were between 10 and 100 times higher than the ranges predicted by theoretical models for supernovas of type 1A. These are the elements aluminium, phosphorus, chlorine, potassium, copper and zinc.

"Since a white dwarf star is formed from a dying red giant, Hypatia could have inherited these element proportions for the six elements from a red giant star. This phenomenon has been observed in white dwarf stars in other research," adds Kramers.

If this hypothesis is correct, the Hypatia stone would be the first tangible evidence on Earth of a supernova type Ia explosion, one of the most energetic events in the universe.

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Alien radioactive element prompts creation rethink

The first-ever discovery of an extraterrestrial radioactive isotope on Earth has scientists rethinking the origins of the elements on our planet.

The tiny traces of plutonium-244 were found in ocean crust alongside radioactive iron-60. The two isotopes are evidence of violent cosmic events in the vicinity of Earth millions of years ago.

Star explosions, or supernovae create many of the heavy elements in the periodic table, including those vital for human life, such as iron, potassium and iodine.

To form even heavier elements, such as gold, uranium and plutonium it was thought that a more violent event may be needed, such as two neutron stars merging.

However, a study led by Professor Anton Wallner from The Australian National University (ANU) suggests a more complex picture.

"The story is complicated -- possibly this plutonium-244 was produced in supernova explosions or it could be left over from a much older, but even more spectacular event such as a neutron star detonation," lead author of the study, Professor Wallner said.

Any plutonium-244 and iron-60 that existed when the Earth formed from interstellar gas and dust over four billion years ago has long since decayed, so current traces of them must have originated from recent cosmic events in space.

The dating of the sample confirms two or more supernova explosions occurred near Earth.

"Our data could be the first evidence that supernovae do indeed produce plutonium-244," Professor Wallner said

"Or perhaps it was already in the interstellar medium before the supernova went off, and it was pushed across the solar system together with the supernova ejecta."

Professor Wallner also holds joint positions at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and Technical University Dresden in Germany, and conducted this work with researchers from Australia, Israel, Japan, Switzerland and Germany.

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Extra-terrestrial impacts may have triggered 'bursts' of plate tectonics

When -- and how -- Earth's surface evolved from a hot, primordial mush into a rocky planet continually resurfaced by plate tectonics remain some of the biggest unanswered questions in earth science research. Now a new study, published in Geology, suggests this earthly transition may in fact have been triggered by extra-terrestrial impacts.

"We tend to think of the Earth as an isolated system, where only internal processes matter," says Craig O'Neill, director of Macquarie University's Planetary Research Centre. "Increasingly, though, we're seeing the effect of solar system dynamics on how the Earth behaves."

Modelling simulations and comparisons with lunar impact studies have revealed that following Earth's accretion about 4.6 billion years ago, Earth-shattering impacts continued to shape the planet for hundreds of millions of years. Although these events appear to have tapered off over time, spherule beds -- distinctive layers of round particles condensed from rock vaporized during an extra-terrestrial impact -- found in South Africa and Australia suggest the Earth experienced a period of intense bombardment about 3.2 billion years ago, roughly the same time the first indications of plate tectonics appear in the rock record.

This coincidence caused O'Neill and co-authors Simone Marchi, William Bottke, and Roger Fu to wonder whether these circumstances could be related. "Modelling studies of the earliest Earth suggest that very large impacts -- more than 300 km in diameter -- could generate a significant thermal anomaly in the mantle," says O'Neill. This appears to have altered the mantle's buoyancy enough to create upwellings that, according to O'Neill, "could directly drive tectonics."

But the sparse evidence found to date from the Archaean -- the period of time spanning 4.0 to 2.5 billion years ago -- suggests that mostly smaller impacts less than 100 km in diameter occurred during this interval. To determine whether these more modest collisions were still large and frequent enough to initiate global tectonics, the researchers used existing techniques to expand the Middle Archaean impact record and then developed numerical simulations to model the thermal effects of these impacts on Earth's mantle.

The results indicate that during the Middle Archaean, 100-kilometer-wide impacts (about 30 km wider than the much younger Chixculub crater) were capable of weakening Earth's rigid, outermost layer. This, says O'Neill, could have acted as a trigger for tectonic processes, especially if Earth's exterior was already "primed" for subduction.

"If the lithosphere were the same thickness everywhere, such impacts would have little effect," states O'Neill. But during the Middle Archean, he says, the planet had cooled enough for the mantle to thicken in some spots and thin in others. The modelling showed that if an impact were to happen in an area where these differences existed, it would create a point of weakness in a system that already had a large contrast in buoyancy -- and ultimately trigger modern tectonic processes.

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Did an extraterrestrial impact trigger the extinction of ice-age animals?

A controversial theory that suggests an extraterrestrial body crashing to Earth almost 13,000 years ago caused the extinction of many large animals and a probable population decline in early humans is gaining traction from research sites around the world.

The Younger Dryas Impact Hypothesis, controversial from the time it was presented in 2007, proposes that an asteroid or comet hit the Earth about 12,800 years ago causing a period of extreme cooling that contributed to extinctions of more than 35 species of megafauna including giant sloths, sabre-tooth cats, mastodons and mammoths. It also coincides with a serious decline in early human populations such as the Clovis culture and is believed to have caused massive wildfires that could have blocked sunlight, causing an "impact winter" near the end of the Pleistocene Epoch.

In a new study published this week in Scientific Reports, a publication of Nature, UofSC archaeologist Christopher Moore and 16 colleagues present further evidence of a cosmic impact based on research done at White Pond near Elgin, South Carolina. The study builds on similar findings of platinum spikes -- an element associated with cosmic objects like asteroids or comets -- in North America, Europe, western Asia and recently in Chile and South Africa.

"We continue to find evidence and expand geographically. There have been numerous papers that have come out in the past couple of years with similar data from other sites that almost universally support the notion that there was an extraterrestrial impact or comet airburst that caused the Younger Dryas climate event," Moore says.

Moore also was lead author on a previous paper documenting sites in North America where platinum spikes have been found and a co-author on several other papers that document elevated levels of platinum in archaeological sites, including Pilauco, Chile -- the first discovery of evidence in the Southern Hemisphere.

"First, we thought it was a North American event, and then there was evidence in Europe and elsewhere that it was a Northern Hemisphere event. And now with the research in Chile and South Africa, it looks like it was probably a global event," he says.

In addition, a team of researchers found unusually high concentrations of platinum and iridium in outwash sediments from a recently discovered crater in Greenland that could have been the impact point. Although the crater hasn't been precisely dated yet, Moore says the possibility is good that it could be the "smoking gun" that scientists have been looking for to confirm a cosmic event. Additionally, data from South America and elsewhere suggests the event may have actually included multiple impacts and airbursts over the entire globe.

While the brief return to ice-age conditions during the Younger Dryas period has been well-documented, the reasons for it and the decline of human populations and animals have remained unclear. The impact hypothesis was proposed as a possible trigger for these abrupt climate changes that lasted about 1,400 years.

The Younger Dryas event gets its name from a wildflower, Dryas octopetala, which can tolerate cold conditions and suddenly became common in parts of Europe 12,800 years ago. The Younger Dryas Impact Hypothesis became controversial, Moore says, because the all-encompassing theory that a cosmic impact triggered cascading events leading to extinctions was viewed as improbable by some scientists.

"It was bold in the sense that it was trying to answer a lot of really tough questions that people have been grappling with for a long time in a single blow," he says, adding that some researchers continue to be critical.

The conventional view has been that the failure of glacial ice dams allowed a massive release of freshwater into the north Atlantic, affecting oceanic circulation and causing the Earth to plunge into a cold climate. The Younger Dryas hypothesis simply claims that the cosmic impact was the trigger for the meltwater pulse into the oceans.

In research at White Pond in South Carolina, Moore and his colleagues used a core barrel to extract sediment samples from underneath the pond. The samples, dated to the beginning of the Younger Dryas with radiocarbon, contain a large platinum anomaly, consistent with findings from other sites, Moore says. A large soot anomaly also was found in cores from the site, indicating regional large-scale wildfires in the same time interval.

In addition, fungal spores associated with the dung of large herbivores were found to decrease at the beginning of the Younger Dryas period, suggesting a decline in ice-age megafauna beginning at the time of the impact.

"We speculate that the impact contributed to the extinction, but it wasn't the only cause. Over hunting by humans almost certainly contributed, too, as did climate change," Moore says. "Some of these animals survived after the event, in some cases for centuries. But from the spore data at White Pond and elsewhere, it looks like some of them went extinct at the beginning of the Younger Dryas, probably as a result of the environmental disruption caused by impact-related wildfires and climate change."

Additional evidence found at other sites in support of an extraterrestrial impact includes the discovery of meltglass, microscopic spherical particles and nanodiamonds, indicating enough heat and pressure was present to fuse materials on the Earth's surface. Another indicator is the presence of iridium, an element associated with cosmic objects, that scientists also found in the rock layers dated 65 million years ago from an impact that caused dinosaur extinction.

While no one knows for certain why the Clovis people and iconic ice-age beasts disappeared, research by Moore and others is providing important clues as evidence builds in support of the Younger Dryas Impact Hypothesis.

Read more at Science Daily