Site Of Biggest Ever Meteorite Collision In The UK Discovered

Scientists believe they have discovered the site of the biggest meteorite impact ever to hit the British Isles.

Evidence for the ancient, 1.2 billion years old, meteorite strike, was first discovered in 2008 near Ullapool, NW Scotland by scientists from Oxford and Aberdeen Universities. The thickness and extent of the debris deposit they found suggested the impact crater — made by a meteorite estimated at 1km wide — was close to the coast, but its precise location remained a mystery.

In a paper published today in Journal of the Geological Society, a team led by Dr Ken Amor from the Department of Earth Sciences at Oxford University, show how they have identified the crater location 15-20km west of a remote part of the Scottish coastline. It is buried beneath both water and younger rocks in the Minch Basin.

Dr Ken Amor said: ‘The material excavated during a giant meteorite impact is rarely preserved on Earth, because it is rapidly eroded, so this is a really exciting discovery. It was purely by chance this one landed in an ancient rift valley where fresh sediment quickly covered the debris to preserve it.

‘The next step will be a detailed geophysical survey in our target area of the Minch Basin.’

Using a combination of field observations, the distribution of broken rock fragments known as basement clasts and the alignment of magnetic particles, the team was able to gauge the direction the meteorite material took at several locations, and plotted the likely source of the crater.

Dr Ken Amor said: ‘It would have been quite a spectacle when this large meteorite struck a barren landscape, spreading dust and rock debris over a wide area.’

1.2 billion years ago most of life on Earth was still in the oceans and there were no plants on the land. At that time Scotland would have been quite close to the equator and in a semi-arid environment. The landscape would have looked a bit like Mars when it had water at the surface.

Earth and other planets may have suffered a higher rate of meteorite impacts in the distant past, as they collided with debris left over from the formation of the early solar system.

However, there is a possibility that a similar event will happen in the future given the number of asteroid and comet fragments floating around in the solar system. Much smaller impacts, where the meteorite is only a few meters across are thought to be relatively common perhaps occurring about once every 25 years on average.

It is thought that collisions with an object about 1 km (as in this instance) across occur between once every 100,000 years to once every one million years — but estimates vary.

One of the reasons for this is that our terrestrial record of large impacts is poorly known because craters are obliterated by erosion, burial and plate tectonics.

Star Formation Burst In The Milky Way 2-3 Billion Years Ago

A team led by researchers of the Institute of Cosmos Sciences of the University of Barcelona (ICCUB, UB-IEEC) and the Besançon Astronomical Observatory have found, analysing data from the Gaia satellite, that a severe star formation burst occurred in the Milky Way about 2 to 3 billion years ago. In this process, more than 50 percent of the stars that created the galactic disc may have been born. Their results come from the combination of the distances, colors and magnitude of the stars that were measured by Gaia with models that predict their distribution in our Galaxy. The study has been published in the journal Astronomy & Astrophysics.

Just like a flame fades when there is no gas in the cylinder, the rhythm of the stellar formation in the Milky Way, fuelled by the gas that was deposited, should decrease slowly and in a continuous way until it has used up the existing gas. The results of the study show that, although this was the process that took place over the first 4 billion years of the disc formation, a severe star formation burst, or “stellar baby boom” — as stated in the article published in the Nature Research Highlights –, inverted this trend. The merging with a satellite galaxy of the Milky Way, which was rich in gas, could have added new fuel and reactivated the process of stellar formation, in a similar way to when a gas cylinder is changed. This mechanism would explain the distribution of distances, ages and masses that are estimated from the data taken from the European Space Agency Gaia satellite.

“The time scale of this star formation burst together with the great amount of stellar mass involved in the process, thousands of millions of solar mass, suggests the disc of our Galaxy did not have a steady and paused evolution, it may have suffered an external perturbation that began about five billion years ago,” said Roger Mor, ICCUB researcher and first author of the article.

“We have been able to find this out due having — for the first time — precise distances for more than three million stars in the solar environment,” says Roger Mor. “Thanks to these data, we could discover the mechanisms that controlled the evolution more than 8-10 billion years ago in the disc of our Galaxy, which is not more than the bright band we see in the sky on a dark night and with no light pollution.” As in many research fields, these findings have been possible thanks to the availability of the combination of a great amount of unprecedented precision data, and the availability of many hours in computing in the computer facilities funded by the FP7 GENIUS European project (Gaia European Project for Improved data User Services) -in the Center for Scientific and Academic Services of Catalonia (CSUC).

Cosmologic models predict our galaxy would have been growing due the merging with other galaxies, a fact that has been stated by other studies using Gaia data. One of these mergers could be the cause of the severe star formation burst that was detected in this study.

“Actually, the peak of star formation is so clear, unlike what we predicted before having data from Gaia, that we thought necessary to treat its interpretation together with experts on cosmological evolution of external galaxies,” notes Francesca Figuerars, lecturer at the Department of Quantum Physics and Astrophysics of the UB, ICCUB member and author of the article.

According to the expert on simulations of galaxies similar to the Milky Way, Santi Roca-Fàbrega -from the Complutense University of Mardid and also author of the article, “the obtained results match with what the current cosmological models predict, and what is more, our Galaxy seen from Gaia’s eyes is an excellent cosmological laboratory where we can test and confront models at a bigger scale in the universe.”

Gaia mission until 2020

This study has been conducted with the second release of the Gaia mission, which was published a year ago, on April 25, 2018. Xavier Luri, director of ICCUB and also an author of the article states: “The role of scientists and engineers of the UB has been essential so that the scientific community enjoys the excellent quality of data from the Gaia release.”

More than 400 scientists and engineers from around Europe are part of the consortium in charge of preparing and validating these data. “Their collective work brought the international scientific community a release that is making us rethink many of the existent scenarios on the origins and evolution of our galaxy,” notes Luri.

In one year, more than 1,200 peer review articles published in journals show the before and after Gaia in almost all fields of astrophysics, from the recent detection of new stellar clusters, new asteroids, to the affirmation of the star extragalactic origin in our Galaxy, going through the calculus of the Milky Way mass and the findings that show compact stars end up slowly solidified.

Cosmic Dust Forms On Supernovae Blasts

Scientists claim to have solved a longstanding mystery as to how cosmic dust, the building blocks of stars and planets, forms across the Universe.

Cosmic dust contains tiny fragments or organic material and is spread out across the Universe. The dust is primarily formed in stars and is then blown off in a slow wind or a massive star explosion.

Up until now, astronomers have had little understanding as to why so much cosmic dust exists in the interstellar medium, with theoretical estimates suggesting it should be obliterated by supernova explosions.

A supernova is an event that occurs upon the violent death of a star and is one of the most powerful events in the Universe, producing a shockwave which destroys almost anything in its path.

Yet new research published in the Monthly Notices of the Royal Astronomical Society has observed the survival of cosmic dust around the closest supernova explosion detected to us, Supernova 1987A.

Observations using NASA’s research aircraft, the Stratospheric Observatory for Infrared Astronomy (SOFIA), have detected cosmic dust in a distinctive set of rings that form part of Supernova 1987A.

The results seem to suggest that there is rapid growth of cosmic dust within the rings, leading the team to believe that dust may actually be re-forming after it is destroyed in the wake of a supernova blast wave.

This immediacy – that the post-shock environment might be ready to form or re-form dust – had never been considered before, and may be pivotal in fully understanding how cosmic dust is both created and destroyed.

“We already knew about the slow-moving dust in the heart of 1987A,” said Dr. Mikako Matsuura, lead author on the paper from the School of Physics and Astronomy.

“It formed from the heavy elements created in the core of the dead star. But the SOFIA observations tell us something completely new.”

Cosmic dust particles can be heated from tens to hundreds of degrees causing them to glow at both infrared and millimeter wavelengths. Observations of millimeter-wave dust emission can generally be carried out from the ground using telescopes; however, observations in the infrared are almost impossible to interference from the water and carbon dioxide in the Earth’s atmosphere.

By flying above most of the obscuring molecules, SOFIA provides access to portions of the infrared spectrum not available from the ground.

Life Thrived On Earth 3.5 Billion Years Ago, Research Suggests

3.5 billion years ago Earth hosted life, but was it barely surviving, or thriving? A new study carried out by a multi institutional team with leadership including the Earth-Life Science Institute (ELSI) of Tokyo Institute of Technology (Tokyo Tech) provides new answers to this question. Microbial metabolism is recorded in billions of years of sulfur isotope ratios that agree with this study’s predictions, suggesting life throve in the ancient oceans. Using this data, scientists can more deeply link the geochemical record with cellular states and ecology.

Scientists want to know how long life has existed on Earth. If it has been around for almost as long as the planet, this suggests it is easy for life to originate and life should be common in the Universe. If it takes a long time to originate, this suggests there were very special conditions that had to occur. Dinosaurs, whose bones are presented in museums around the world, were preceded by billions of years by microbes. While microbes have left some physical evidence of their presence in the ancient geological record, they do not fossilize well, thus scientists use other methods for understanding whether life was present in the geological record.

Presently, the oldest evidence of microbial life on Earth comes to us in the form of stable isotopes. The chemical elements charted on the periodic are defined by the number of protons in their nuclei, for example, hydrogen atoms have one proton, helium atoms have two, carbon atoms contain six. In addition to protons, most atomic nuclei also contain neutrons, which are about as heavy as protons, but which don’t bear an electric charge. Atoms which contain the same number of protons, but variable numbers of neutrons are known as isotopes. While many isotopes are radioactive and thus decay into other elements, some do not undergo such reactions; these are known as “stable” isotopes. For example, the stable isotopes of carbon include carbon 12 (written as 12C for short, with 6 protons and 6 neutrons) and carbon 13 (13C, with 6 protons and 7 neutrons).

All living things, including humans, “eat and excrete.” That is to say, they take in food and expel waste. Microbes often eat simple compounds made available by the environment. For example, some are able to take in carbon dioxide (CO2) as a carbon source to build their own cells. Naturally occurring CO2 has a fairly constant ratio of 12C to 13C. However, 12CO2 is about 2 % lighter than 13CO2, so 12CO2 molecules diffuse and react slightly faster, and thus the microbes themselves become “isotopically light,” containing more 12C than 13C, and when they die and leave their remains in the fossil record, their stable isotopic signature remains, and is measurable. The isotopic composition, or “signature,” of such processes can be very specific to the microbes that produce them.

Besides carbon there are other chemical elements essential for living things. For example, sulfur, with 16 protons, has three naturally abundant stable isotopes, 32S (with 16 neutrons), 33S (with 17 neutrons) and 34S (with 18 neutrons). Sulfur isotope patterns left behind by microbes thus record the history of biological metabolism based on sulfur-containing compounds back to around 3.5 billion years ago. Hundreds of previous studies have examined wide variations in ancient and contemporary sulfur isotope ratios resulting from sulfate (a naturally occurring sulfur compound bonded to four oxygen atoms) metabolism. Many microbes are able to use sulfate as a fuel, and in the process excrete sulfide, another sulfur compound. The sulfide “waste” of ancient microbial metabolism is then stored in the geological record, and its isotope ratios can be measured by analyzing minerals such as the FeS2 mineral pyrite.

This new study reveals a primary biological control step in microbial sulfur metabolism, and clarifies which cellular states lead to which types of sulfur isotope fractionation. This allows scientists to link metabolism to isotopes: by knowing how metabolism changes stable isotope ratios, scientists can predict the isotopic signature organisms should leave behind. This study provides some of the first information regarding how robustly ancient life was metabolizing. Microbial sulfate metabolism is recorded in over a three billion years of sulfur isotope ratios that are in line with this study’s predictions, which suggest life was in fact thriving in the ancient oceans. This work opens up a new field of research, which ELSI Associate Professor Shawn McGlynn calls “evolutionary and isotopic enzymology.” Using this type of data, scientists can now proceed to other elements, such as carbon and nitrogen, and more completely link the geochemical record with cellular states and ecology via an understanding of enzyme evolution and Earth history.

Ancient Asteroid Impacts Played A Role In Creation Of Earth’s Future Continents

The heavy bombardment of terrestrial planets by asteroids from space has contributed to the formation of the early evolved crust on Earth that later gave rise to continents — home to human civilisation.

More than 3.8 billion years ago, in a time period called the Hadean eon, our planet Earth was constantly bombarded by asteroids, which caused the large-scale melting of its surface rocks. Most of these surface rocks were basalts, and the asteroid impacts produced large pools of superheated impact melt of such composition. These basaltic pools were tens of kilometres thick, and thousands of kilometres in diameter.

“If you want to get an idea of what the surface of Earth looked like at that time, you can just look at the surface of the Moon which is covered by a vast amount of large impact craters,” says Professor Rais Latypov from the School of Geosciences of the University of the Witwatersrand in South Africa.

The subsequent fate of these ancient, giant melt sheet remains, however, highly debatable. It has been argued that, on cooling, they may have crystallized back into magmatic bodies of the same, broadly basaltic composition. In this scenario, asteroid impacts are supposed to play no role in the formation of the Earth’s early evolved crust.

An alternative model suggests that these sheets may undergo large-scale chemical change to produce layered magmatic intrusions, such as the Bushveld Complex in South Africa. In this scenario, asteroid impacts may have played an important role in producing various igneous rocks in the early Earth’s crust and therefore they may have contributed to its chemical evolution.

There is no direct way to rigorously test these two competing scenarios because the ancient Hadean impact melts have been later obliterated by plate tectonics. However, by studying the younger impact melt sheet of the Sudbury Igneous Complex (SIC) in Canada, Latypov and his research team have inferred that ancient asteroid impacts were capable of producing various rock types from the earlier Earth’s basaltic crust. Most importantly, these impacts may have made the crust compositionally more evolved, i.e. silica-rich in composition. Their research has been published in a paper in Nature Communications.

The SIC is the largest, best exposed and accessible asteroid impact melt sheet on Earth, which has resulted from a large asteroid impact 1.85 billion years ago. This impact produced a superheated melt sheet of up to 5 km thick. The SIC now shows a remarkable magmatic stratigraphy, with various layers of igneous rocks.

“Our field and geochemical observations — especially the discovery of large discrete bodies of melanorites throughout the entire stratigraphy of the SIC — allowed us to reassess current models for the formation of the SIC and firmly conclude that its conspicuous magmatic stratigraphy is the result of large-scale fractional crystallization,” says Latypov.

“An important implication is that more ancient and primitive Hadean impact melt sheets on the early Earth and other terrestrial planets would also have undergone near-surface, large-volume differentiation to produce compositionally stratified bodies. The detachment of dense primitive layers from these bodies and their sinking into the mantle would leave behind substantial volumes of evolved rocks (buoyant crustal blocks) in the Hadean crust. This would make the crust compositionally layered and increasingly more evolved from its base towards the Earth’s surface.”

“These impacts made the crust compositionally more evolved — in other words, silica-rich in composition,” says Latypov. “Traditionally, researchers believe that such silica-rich evolved rocks — which are essentially building buoyant blocks of our continents — can only be generated deep in the Earth, but we now argue that such blocks can be produced at new-surface conditions within impact melt pools.”

Missing-Link In Planet Evolution Found

For the first time ever, astronomers have detected a 1.3 km radius body at the edge of the solar system. Kilometer-sized bodies like the one discovered have been predicted to exist for more than 70 years. These objects acted as an important step in the planet formation process between small initial amalgamations of dust and ice and the planets we see today.

The Edgeworth-Kuiper Belt is a collection of small celestial bodies located beyond Neptune’s orbit. The most famous Edgeworth-Kuiper Belt Object is Pluto. Edgeworth-Kuiper Belt Objects are believed to be remnants left over from the formation of the solar system. While small bodies like asteroids in the inner solar system have been altered by solar radiation, collisions, and the gravity of the planets over time; objects in the cold, dark, lonely Edgeworth-Kuiper Belt preserve the pristine conditions of the early solar system. Thus astronomers study them to learn about the beginning of the planet formation process.

Edgeworth-Kuiper Belt objects with radii from 1 kilometer to several kilometers have been predicted to exist, but they are too distant, small, and dim for even world-leading telescopes, like the Subaru Telescope, to observe directly. So a research team led by Ko Arimatsu at the National Astronomical Observatory of Japan used a technique known as occultation: monitoring a large number of stars and watching for the shadow of an object passing in front of one of them. The Organized Autotelescopes for Serendipitous Event Survey (OASES) team placed two small 28 cm telescopes on the roof of the Miyako open-air school on Miyako Island, Miyakojima-shi, Okinawa Prefecture, Japan, and monitored approximately 2000 stars for a total of 60 hours.

Analyzing the data, the team found an event consistent with a star appearing to dim as it is occulted by a 1.3 km radius Edgeworth-Kuiper Belt Object. This detection indicates that kilometer sized Edgeworth-Kuiper Belt Objects are more numerous than previously thought. This supports models where planetesimals first grow slowly into kilometer sized objects before runaway growth causes them to merge into planets.

Arimatsu explains, “This is a real victory for little projects. Our team had less than 0.3 percent of the budget of large international projects. We didn’t even have enough money to build a second dome to protect our second telescope! Yet we still managed to make a discovery that is impossible for the big projects. Now that we know our system works, we will investigate the Edgeworth-Kuiper Belt in more detail. We also have our sights set on the still undiscovered Oort Cloud out beyond that.”

The study is published in Nature Astronomy.

Seeing Double Could Help Resolve Dispute About How Fast The Universe Is Expanding

The question of how quickly the universe is expanding has been bugging astronomers for almost a century. Different studies keep coming up with different answers — which has some researchers wondering if they’ve overlooked a key mechanism in the machinery that drives the cosmos.

Now, by pioneering a new way to measure how quickly the cosmos is expanding, a team led by UCLA astronomers has taken a step toward resolving the debate. The group’s research is published today in Monthly Notices of the Royal Astronomical Society.

At the heart of the dispute is the Hubble constant, a number that relates distances to the redshifts of galaxies — the amount that light is stretched as it travels to Earth through the expanding universe. Estimates for the Hubble constant range from about 67 to 73 kilometers per second per megaparsec, meaning that two points in space 1 megaparsec apart (the equivalent of 3.26 million light-years) are racing away from each other at a speed between 67 and 73 kilometers per second.

“The Hubble constant anchors the physical scale of the universe,” said Simon Birrer, a UCLA postdoctoral scholar and lead author of the study. Without a precise value for the Hubble constant, astronomers can’t accurately determine the sizes of remote galaxies, the age of the universe or the expansion history of the cosmos.

Most methods for deriving the Hubble constant have two ingredients: a distance to some source of light and that light source’s redshift. Looking for a light source that had not been used in other scientists’ calculations, Birrer and colleagues turned to quasars, fountains of radiation that are powered by gargantuan black holes. And for their research, the scientists chose one specific subset of quasars — those whose light has been bent by the gravity of an intervening galaxy, which produces two side-by-side images of the quasar on the sky.

Light from the two images takes different routes to Earth. When the quasar’s brightness fluctuates, the two images flicker one after another, rather than at the same time. The delay in time between those two flickers, along with information about the meddling galaxy’s gravitational field, can be used to trace the light’s journey and deduce the distances from Earth to both the quasar and the foreground galaxy. Knowing the redshifts of the quasar and galaxy enabled the scientists to estimate how quickly the universe is expanding.

The UCLA team, as part of the international H0liCOW collaboration, had previously applied the technique to study quadruply imaged quasars, in which four images of a quasar appear around a foreground galaxy. But quadruple images are not nearly as common — double-image quasars are thought to be about five times as abundant as the quadruple ones.

To demonstrate the technique, the UCLA-led team studied a doubly imaged quasar known as SDSS J1206+4332; they relied on data from the Hubble Space Telescope, the Gemini and W.M. Keck observatories, and from the Cosmological Monitoring of Gravitational Lenses, or COSMOGRAIL, network — a program managed by Switzerland’s Ecole Polytechnique Federale de Lausanne that is aimed at determining the Hubble constant.

Tommaso Treu, a UCLA professor of physics and astronomy and the paper’s senior author, said the researchers took images of the quasar every day for several years to precisely measure the time delay between the images. Then, to get the best estimate possible of the Hubble constant, they combined the data gathered on that quasar with data that had previously been gathered by their H0liCOW collaboration on three quadruply imaged quasars.

“The beauty of this measurement is that it’s highly complementary to and independent of others,” Treu said.

The UCLA-led team came up with an estimate for the Hubble constant of about 72.5 kilometers per second per megaparsec, a figure in line with what other scientists had determined in research that used distances to supernovas — exploding stars in remote galaxies — as the key measurement. However, both estimates are about 8 percent higher than one that relies on a faint glow from all over the sky called the cosmic microwave background, a relic from 380,000 years after the Big Bang, when light traveled freely through space for the first time.

“If there is an actual difference between those values, it means the universe is a little more complicated,” Treu said.

On the other hand, Treu said, it could also be that one measurement — or all three — are wrong.

The researchers are now looking for more quasars to improve the precision of their Hubble constant measurement. Treu said one of the most important lessons of the new paper is that doubly imaged quasars give scientists many more useful light sources for their Hubble constant calculations. For now, though, the UCLA-led team is focusing its research on 40 quadruply imaged quasars, because of their potential to provide even more useful information than doubly imaged ones.

Sixteen other researchers from 13 institutions in seven countries contributed to the paper; the research was supported in part by grants from NASA, the National Science Foundation and the Packard Foundation.