New discovery about meteorites informs atmospheric entry threat assessment

Researchers at the University of Illinois Urbana-Champaign watched fragments of two meteors as they ramped up the heat from room temperature to the temperature it reaches as it enters Earth's atmosphere and made a significant discovery. The vaporized iron sulfide leaves behind voids, making the material more porous. This information will help when predicting the weight of a meteor, its likelihood to break apart, and the subsequent damage assessment if it should land.

"We extracted samples from the interiors that had not already been exposed to the high heat of the entry environment," said Francesco Panerai, professor in the Department of Aerospace Engineering at UIUC. "We wanted to understand how the microstructure of a meteorite changes as it travels through the atmosphere."

Panerai and collaborators at NASA Ames Research Center used an X-ray microtomography technique that allowed them to observe the samples in place as they were heated up to 2,200 degrees Fahrenheit and create images in three dimensions. The experiments were performed using the synchrotron Advanced Light Source at Lawrence Berkeley National Laboratory.

"The iron sulfide inside the meteorite vaporized as it heated. Some of the grains actually disappeared leaving large voids in the material," Panerai said. "We were surprised by this observation. The ability to look at the interior of the meteorite in 3D, while being heated, led us to discover a progressive increase of material porosity with heating. After that, we took cross sections of the material and looked at the chemical composition to understand the phase that had been modified by the heating, changing its porosity.

"This discovery provides evidence that meteorite materials become porous and permeable, which we speculate will have an effect on its strength and propensity for fragmentation."

NASA selected Tamdakht as case study, a meteorite that landed in a Moroccan desert a few years ago. But the team of researchers wanted to corroborate what they'd seen so they repeated experiments on Tenham to see if a meteorite with different composition would behave in the same way. Both specimens were from a similar class of meteorite called chondrites, the most common among the meteorite finds that are made up of iron and nickel, which are high-density elements.

"Both became porous, but the porosity that develops depends upon the content of the sulfides," Panerai said. "One of the two had higher iron sulfides, which is what evaporates. We found that the vaporizing of iron sulfides happens at mild entry temperatures. This is something that would happen, not at the external fusion crust of the meteorite where the temperature is a lot higher, but just underneath the surface."

The study was motivated by the potential threat meteorites pose humans -- the clearest example being the Chelyabinsk meteor that blasted the Earth's atmosphere over Russia in 2013 and resulted in about 1,500 people being injured from indirect effects such as broken glass from the shock wave. After that incident, NASA created the Asteroid Threat Assessment Program to provide scientific tools that can help decision makers understand potential meteorite threats to the population.

"Most of the cosmic material burns away as it enters. The atmosphere protects us," Panerai said. "But there are significant sized meteorites that can be harmful. For these larger objects that have a non-zero probability of hitting us, we need to have tools to predict what damage they would do if they would hit Earth. Based on these tools, we can predict how it enters the atmosphere, its size, how it behaves as it goes through the atmosphere, etc. so decision makers can take counter measures."

Panerai said the Asteroid Threat Assessment Program is currently developing models to show how meteorites behave and models require a lot of data. "We used machine learning for the data analysis because the amount of data to analyze is huge and we need efficient techniques.

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Lunar samples solve mystery of the moon's supposed magnetic shield

In 2024, a new age of space exploration will begin when NASA sends astronauts to the moon as part of their Artemis mission, a follow-up to the Apollo missions of the 1960s and 1970s.

Some of the biggest questions that scientists hope to explore include determining what resources are found in the moon's soil and how those resources might be used to sustain life.

In a paper published in the journal Science Advances, researchers at the University of Rochester, leading a team of colleagues at seven other institutions, report their findings on a major factor that influences the types of resources that may be found on the moon: whether or not the moon has had a long-lived magnetic shield at any point in its 4.53 billion-year history.

The presence or absence of a shield matters because magnetic shields protect astronomical bodies from harmful solar radiation. And the team's findings contradict some longstanding assumptions.

"This is a new paradigm for the lunar magnetic field," says first author John Tarduno, the William R. Kenan, Jr., Professor of Geophysics in the Department of Earth and Environmental Sciences and dean of research for Arts, Sciences & Engineering at Rochester.

Did the Moon Ever Have a Magnetic Field?

For years, Tarduno has been a leader in the field of paleomagnetism, studying the development of Earth's magnetic shield as a means to understanding planetary evolution and environmental change.

Earth's magnetic shield originates deep within the planet's core. There, swirling liquid iron generates electric currents, driving a phenomenon called the geodynamo, which produces the shield. The magnetic shield is invisible, but researchers have long recognized that it is vital for life on Earth's surface because it protects our planet from solar wind -- streams of radiation from the sun.

But has Earth's moon ever had a magnetic shield?

While the moon has no magnetic shield now, there has been debate over whether or not the moon may have had a prolonged magnetic shield at some point in its history.

"Since the Apollo missions, there has been this idea that the moon had a magnetic field that was as strong or even stronger than Earth's magnetic field at around 3.7 billion years ago," Tarduno says.

The belief that the moon had a magnetic shield was based on an initial dataset from the 1970s that included analyses of samples collected during the Apollo missions. The analyses showed that the samples had magnetization, which researchers believed was caused by the presence of a geodynamo.

But a couple of factors have since given researchers pause.

"The core of the moon is really small and it would be hard to actually drive that kind of magnetic field," Tarduno explains. "Plus, the previous measurements that record a high magnetic field were not conducted using heating experiments. They used other techniques that may not accurately record the magnetic field."

When Lunar Samples Meet Lasers

Tarduno and his colleagues tested glass samples gathered on previous Apollo missions, but used CO2 lasers to heat the lunar samples for a short amount of time, a method that allowed them to avoid altering the samples. They then used highly sensitive superconducting magnetometers to more accurately measure the samples' magnetic signals.

"One of the issues with lunar samples has been that the magnetic carriers in them are quite susceptible to alteration," Tarduno says. "By heating with a laser, there is no evidence of alteration in our measurements, so we can avoid the problems people may have had in the past."

The researchers determined that the magnetization in the samples could be the result of impacts from objects such as meteorites or comets -- not the result of magnetization from the presence of a magnetic shield. Other samples they analyzed had the potential to show strong magnetization in the presence of a magnetic field, but didn't show any magnetization, further indicating that the moon has never had a prolonged magnetic shield.

"If there had been a magnetic field on the moon, the samples we studied should all have acquired magnetization, but they haven't," Tarduno says. "That's pretty conclusive that the moon didn't have a long-lasting dynamo field."

Lack of Magnetic Shield Means an Abundance of Elements

Without the protection of a magnetic shield, the moon was susceptible to solar wind, which may have caused a variety of volatiles -- chemical elements and compounds that can be easily evaporated -- to become implanted in the lunar soil. These volatiles may include carbon, hydrogen, water, and helium 3, an isotope of helium that is not present in abundance on Earth.

"Our data indicates we should be looking at the high end of estimates of helium 3 because a lack of magnetic shield means more solar wind reaches the lunar surface, resulting in much deeper reservoirs of helium 3 than people thought previously," Tarduno says.

The research may help inform a new wave of lunar experiments based on data that will be gathered by the Artemis mission. Data from samples gathered during the mission will allow scientists and engineers to study the presence of volatiles and better determine if these materials can be extracted for human use. Helium 3, for instance, is currently used in medical imaging and cryogenics and is a possible future fuel source.

A lack of magnetic shielding also means that ancient lunar soils may hold records of past solar wind emissions. Analyzing cores of soil samples could therefore provide scientists with a better understanding of the evolution of the sun.

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Cooling of Earth caused by eruptions, not meteors

Volcanic eruption

Ancient sediment found in a central Texas cave appears to solve the mystery of why the Earth cooled suddenly about 13,000 years ago, according to a research study co-authored by a Texas A&M University professor.

Michael Waters, director of The Center for The Study of the First Americans and Distinguished Professor at Texas A&M University, and colleagues from Baylor University and the University of Houston have had their work published in Science Advances.

Some researchers believed the event -- which cooled the Earth by about 3 degrees Centigrade, a huge amount -- was caused by an extraterrestrial impact with the Earth, such as a meteor collision.

But Waters and the team found that the evidence left in layers of sediment in Hall's Cave were almost certainly the result of volcanic eruptions.

Waters said that Hall's Cave, located in the Texas hill country, has a sediment record extending over 20,000 years and he first began researching the cave in 2017.

"It is an exceptional record that offers a unique opportunity for interdisciplinary cooperation to investigate a number of important research questions," he said.

"One big question was, did an extraterrestrial impact occur near the end of the last ice age, about 13,000 years ago as the ice sheets covering Canada were melting, and cause an abrupt cooling that thrust the northern hemisphere back into the ice age for an extra 1,200 years?"

Waters and the team found that within the cave are layers of sediment, first identified by Thomas Stafford (Stafford Research Laboratories, Colorado), that dated to the time of the proposed impact that could answer the question and perhaps even identify the trigger that started the ancient cold snap.

The event also likely helped cause the extinction of large mammals such as mammoth, horse and camel that once roamed North America.

"This work shows that the geochemical signature associated with the cooling event is not unique but occurred four times between 9,000 and 15,000 years ago," said Alan Brandon, professor of geosciences at University of Houston and head of the research team.

"Thus, the trigger for this cooling event didn't come from space. Prior geochemical evidence for a large meteor exploding in the atmosphere instead reflects a period of major volcanic eruptions.

"I was skeptical," Brandon said. "We took every avenue we could to come up with an alternative explanation, or even avoid, this conclusion. A volcanic eruption had been considered one possible explanation but was generally dismissed because there was no associated geochemical fingerprint."

After a volcano erupts, the global spread of aerosols reflects incoming solar radiation away from Earth and may lead to global cooling post eruption for one to five years, depending on the size and timescales of the eruption, the team said.

"The Younger Dryas, which occurred about 13,000 years ago, disrupted distinct warming at the end of the last ice age," said co-author Steven Forman, professor of geosciences at Baylor.

The Earth's climate may have been at a tipping point at the end of Younger Dryas, possibly from the ice sheet discharge into the North Atlantic Ocean, enhanced snow cover and powerful volcanic eruptions that may have in combination led to intense Northern Hemisphere cooling, Forman said.

"This period of rapid cooling coincides with the extinction of a number of species, including camels and horses, and the appearance of the Clovis archaeological tradition," said Waters.

Brandon and fellow University of Houston scientist Nan Sun completed the isotopic analysis of sediments collected from Hall's Cave. They found that elements such as iridium, ruthenium, platinum, palladium and rhenium were not present in the correct proportions, meaning that a meteor or asteroid could not have caused the event.

"The isotope analysis and the relative proportion of the elements matched those that were found in previous volcanic gases," said Sun, lead author of the report.

Volcanic eruptions cause their most severe cooling near the source, usually in the year of the eruption, with substantially less cooling in the years after the eruption, the team said.

The Younger Dryas cooling lasted about 1,200 years, "so a sole volcanic eruptive cause is an important initiating factor, but other Earth system changes, such as cooling of the oceans and more snow cover were needed to sustain this colder period, "Forman said.

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Ancient meteorite site on Earth could reveal new clues about Mars' past

Scientists have devised new analytical tools to break down the enigmatic history of Mars' atmosphere -- and whether life was once possible there.

A paper detailing the work was published today in the journal Science Advances. It could help astrobiologists understand the alkalinity, pH and nitrogen content of ancient waters on Mars, and by extension, the carbon dioxide composition of the planet's ancient atmosphere.

Mars of today is too cold to have liquid water on its surface, a requirement for hosting life as we know it.

"The question that drives our interests isn't whether there's life on present-day Mars," said Tim Lyons, UCR distinguished professor of biogeochemistry. "We are driven instead by asking whether there was life on Mars billions of years ago, which seems significantly more likely."

However, "Overwhelming evidence exists that Mars had liquid water oceans roughly 4 billion years ago," Lyons noted.

The central question astrobiologists ask is how that was possible. The red planet is farther from the sun than Earth is, and billions of years ago the sun generated less heat than it does today.

"To have made the planet warm enough for liquid surface water, its atmosphere would likely have needed an immense amount of greenhouse gas, carbon dioxide specifically," explained Chris Tino, a UCR graduate student and co-first-author of the paper along with Eva Stüeken, a lecturer at the University of St. Andrews in Scotland.

Since sampling Mars' atmosphere from billions of years ago to learn its carbon dioxide content is impossible, the team concluded that a site on Earth whose geology and chemistry bear similarities to the Martian surface might provide some of the missing pieces. They found it in southern Germany's Nordlinger Ries crater.

Formed roughly 15 million years ago after being struck by a meteorite, Ries crater features layers of rocks and minerals better preserved than almost anywhere on Earth.

The Mars 2020 rover will land in a similarly structured, well-preserved ancient crater. Both places featured liquid water in their distant past, making their chemical compositions comparable.

According to Tino, it's unlikely that ancient Mars had enough oxygen to have hosted complex life forms like humans or animals.

However, some microorganisms could have survived if ancient Martian water had both a neutral pH level and was highly alkaline. Those conditions imply sufficient carbon dioxide in the atmosphere -- perhaps thousands of times more than what surrounds Earth today -- to warm the planet and make liquid water possible.

While pH measures the concentration of hydrogen ions in a solution, alkalinity is a measure dependent on several ions and how they interact to stabilize pH.

"Ries crater rock samples have ratios of nitrogen isotopes that can best be explained by high pH," Stüeken said. "What's more, the minerals in the ancient sediments tell us that alkalinity was also very high."

However, Martian samples with mineral indicators for high alkalinity and nitrogen isotope data pointing to relatively low pH would demand extremely high levels of carbon dioxide in the past atmosphere.

The resulting carbon dioxide estimates could help solve the long-standing mystery of how an ancient Mars located so far from a faint early sun could have been warm enough for surface oceans and perhaps life. How such high levels could have been maintained and what might have lived beneath them remain important questions.

"Before this study, it wasn't clear that something as straightforward as nitrogen isotopes could be used to estimate the pH of ancient waters on Mars; pH is a key parameter in calculating the carbon dioxide in the atmosphere," Tino said.

Funding for this study came from the NASA Astrobiology Institute, where Lyons leads the Alternative Earths team based at UCR.

Included in the study were Gernot Arp of the Georg-August University of Göttingen and Dietmar Jung of the Bavarian State Office for the Environment.

When samples from NASA's Mars 2020 rover mission are brought back to Earth, they could be analyzed for their nitrogen isotope ratios. These data could confirm the team's suspicion that very high levels of carbon dioxide made liquid water possible and maybe even some forms of microbial life long ago.

Read more at Science Daily

Meteors help Martian clouds form

Mars.

How did the Red Planet get all of its clouds? CU Boulder researchers may have discovered the secret: just add meteors.

Astronomers have long observed clouds in Mars' middle atmosphere, which begins about 18 miles (30 kilometers) above the surface, but have struggled to explain how they formed.

Now, a new study, which will be published on June 17 in the journal Nature Geoscience, examines those wispy accumulations and suggests that they owe their existence to a phenomenon called "meteoric smoke" -- essentially, the icy dust created by space debris slamming into the planet's atmosphere.

The findings are a good reminder that planets and their weather patterns aren't isolated from the solar systems around them.

"We're used to thinking of Earth, Mars and other bodies as these really self-contained planets that determine their own climates," said Victoria Hartwick, a graduate student in the Department of Atmospheric and Ocean Sciences (ATOC) and lead author of the new study. "But climate isn't independent of the surrounding solar system."

The research, which included co-authors Brian Toon at CU Boulder and Nicholas Heavens at Hampton University in Virginia, hangs on a basic fact about clouds: They don't come out of nowhere.

"Clouds don't just form on their own," said Hartwick, also of the Laboratory for Atmospheric and Space Physics at CU Boulder. "They need something that they can condense onto."

On Earth, for example, low-lying clouds begin life as tiny grains of sea salt or dust blown high into the air. Water molecules clump around these particles, becoming bigger and bigger until they form the large puffs that you can see from the ground.

But, as far as scientists can tell, those sorts of cloud seeds don't exist in Mars' middle atmosphere, Hartwick said. And that's what led her and her colleagues to meteors.

Hartwick explained that about two to three tons of space debris crash into Mars every day on average. And as those meteors rip apart in the planet's atmosphere, they inject a huge volume of dust into the air.

To find out if such smoke would be enough to give rise to Mars' mysterious clouds, Hartwick's team turned to massive computer simulations that attempt to mimic the flows and turbulence of the planet's atmosphere.

And sure enough, when they included meteors in their calculations, clouds appeared.

"Our model couldn't form clouds at these altitudes before," Hartwick said. "But now, they're all there, and they seem to be in all the right places."

The idea might not be as outlandish as it sounds, she added. Research has shown that similar interplanetary schmutz may help to seed clouds near Earth's poles.

But she also says that you shouldn't expect to see gigantic thunderheads forming above the surface of Mars anytime soon. The clouds her team studied were much more like bits of cotton candy than the clouds Earthlings are used to.

"But just because they're thin and you can't really see them doesn't mean they can't have an effect on the dynamics of the climate," Hartwick said.

The researchers' simulations, for example, showed that middle atmosphere clouds could have a large impact on the Martian climate. Depending on where the team looked, those clouds could cause temperatures at high altitudes to swing up or down by as much as 18 degrees Fahrenheit (10 degrees Celsius).

And that climactic impact is what gets Brian Toon, a professor in ATOC, excited. He said that the team's findings on modern-day Martian clouds may also help to reveal the planet's past evolution and how it once managed to support liquid water at its surface.

Read more at Science Daily

Meteor magnets in outer space: Finding elusive giant planets

Jupiter.

Astronomers believe planets like Jupiter shield us from space objects that would otherwise slam into Earth. Now they're closer to learning whether giant planets act as guardians of solar systems elsewhere in the galaxy.

A UCR-led team has discovered two Jupiter-sized planets about 150 light years away from Earth that could reveal whether life is likely on the smaller planets in other solar systems.

"We believe planets like Jupiter have profoundly impacted the progression of life on Earth. Without them, humans might not be here to have this conversation," said Stephen Kane, lead study author and UCR associate professor of planetary astrophysics. "Understanding how many other stars have planets like Jupiter could be very important for learning about the habitability of planets in those systems."

Along with liquid water oceans, Kane said astronomers believe such planets have the ability to act as 'slingshots,' pulling objects like meteors, comets, and asteroids out of their trajectories en route to impact with small, rocky planets.

Many larger planets have been found close to their stars. However, those aren't as useful for learning about the architecture of our own solar system, where the giant planets including Saturn, Uranus and Neptune are all farther from the sun. Big planets far from their stars have, until now, been harder to find.

A study recently accepted for publication in the Astronomical Journal details how Kane's team found success in a novel approach combining traditional detection methods with the latest technologies.

One popular method of searching for exoplanets -- planets in other solar systems -- involves monitoring stars for "wobble," in which a star moves toward and away from Earth. The wobble is likely caused by the gravitational pull a nearby planet is exerting on it. When a star wobbles, it's a clue there may be an exoplanet nearby.

When the planet is far from its star, the gravitational pull is weaker, making the wobble smaller and harder to detect. The other problem with using the wobble detection method, Kane said, is that it just takes a long time. Earth only takes a year to orbit the sun. Jupiter takes 12, Saturn takes 30, and Neptune takes an astonishing 164 years.

The larger exoplanets also take many years to circle their stars, which means observing a complete orbit could engulf an astronomer's entire career. To accelerate the process, Kane and his team combined the wobble method with direct imaging. This way, if the team thought a planet might be causing wobble, they could confirm it by sight.

Obtaining a direct image of a planet quadrillions of miles away is no simple task. It requires the largest possible telescope, one that is at least 32 feet long and highly sensitive. Even from this distance, the light of the stars can overexpose the image, obscuring the target planets.

The team overcame this challenge by learning to recognize and eliminate the patterns in their images created by starlight. Removing the starlight allowed Kane's team to see what remained.

"Direct imaging has come a long way both in terms of understanding the patterns we find, and in terms of the instruments used to create the images, which are much higher resolution than they've ever been," Kane said. "You see this every time a new smartphone is released -- the camera detectors are always being improved and that's true in astronomy as well."

In this project, the team applied the combination of wobble and imaging method to 20 stars. In addition to the two being orbited by giant Jupiter-like planets that had not been previously discovered, the team also detected a third, previously observed star with a giant planet in its system.

Going forward, the team will continue to monitor 10 of the stars where planetary companions could not be ruled out. In addition, Kane is planning a new project to measure how long it takes these exoplanets to complete rotations toward and away from their stars, which cannot currently be measured.

Kane's team is international, with members at the Australian Astronomical Observatory, University of Southern Queensland, University of New South Wales and Macquarie University in Australia, as well as at the University of Hertfordshire in the United Kingdom. They are also spread across the U.S. at the National Optical Astronomy Observatory in Tucson, AZ, Southern Connecticut State University, NASA Ames Research Center and Stanford University in California and the Carnegie Institution of Washington in D.C.

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66-million-year-old deathbed linked to dinosaur-killing meteor

Fossilized fish piled one atop another, suggesting that they were flung ashore and died stranded together on a sand bar after the wave from the seiche withdrew.

The beginning of the end started with violent shaking that raised giant waves in the waters of an inland sea in what is now North Dakota.

Then, tiny glass beads began to fall like birdshot from the heavens. The rain of glass was so heavy it may have set fire to much of the vegetation on land. In the water, fish struggled to breathe as the beads clogged their gills.

The heaving sea turned into a 30-foot wall of water when it reached the mouth of a river, tossing hundreds, if not thousands, of fresh-water fish -- sturgeon and paddlefish -- onto a sand bar and temporarily reversing the flow of the river. Stranded by the receding water, the fish were pelted by glass beads up to 5 millimeters in diameter, some burying themselves inches deep in the mud. The torrent of rocks, like fine sand, and small glass beads continued for another 10 to 20 minutes before a second large wave inundated the shore and covered the fish with gravel, sand and fine sediment, sealing them from the world for 66 million years.

This unique, fossilized graveyard -- fish stacked one atop another and mixed in with burned tree trunks, conifer branches, dead mammals, mosasaur bones, insects, the partial carcass of a Triceratops, marine microorganisms called dinoflagellates and snail-like marine cephalopods called ammonites -- was unearthed by paleontologist Robert DePalma over the past six years in the Hell Creek Formation, not far from Bowman, North Dakota. The evidence confirms a suspicion that nagged at DePalma in his first digging season during the summer of 2013 -- that this was a killing field laid down soon after the asteroid impact that eventually led to the extinction of all ground-dwelling dinosaurs. The impact at the end of the Cretaceous Period, the so-called K-T boundary, exterminated 75 percent of life on Earth.

"This is the first mass death assemblage of large organisms anyone has found associated with the K-T boundary," said DePalma, curator of paleontology at the Palm Beach Museum of Natural History in Florida and a doctoral student at the University of Kansas. "At no other K-T boundary section on Earth can you find such a collection consisting of a large number of species representing different ages of organisms and different stages of life, all of which died at the same time, on the same day."

In a paper to appear next week in the journal Proceedings of the National Academy of Sciences, he and his American and European colleagues, including two University of California, Berkeley, geologists, describe the site, dubbed Tanis, and the evidence connecting it with the asteroid or comet strike off Mexico's Yucatan Peninsula 66 million years ago. That impact created a huge crater, called Chicxulub, in the ocean floor and sent vaporized rock and cubic miles of asteroid dust into the atmosphere. The cloud eventually enveloped Earth, setting the stage for Earth's last mass extinction.

"It's like a museum of the end of the Cretaceous in a layer a meter-and-a-half thick," said Mark Richards, a UC Berkeley professor emeritus of earth and planetary science who is now provost and professor of earth and space sciences at the University of Washington.

Richards and Walter Alvarez, a UC Berkeley Professor of the Graduate School who 40 years ago first hypothesized that a comet or asteroid impact caused the mass extinction, were called in by DePalma and Dutch scientist Jan Smit to consult on the rain of glass beads and the tsunami-like waves that buried and preserved the fish. The beads, called tektites, formed in the atmosphere from rock melted by the impact.

Tsunami vs. seiche

Richards and Alvarez determined that the fish could not have been stranded and then buried by a typical tsunami, a single wave that would have reached this previously unknown arm of the Western Interior Seaway no less than 10 to 12 hours after the impact 3,000 kilometers away, if it didn't peter out before then. Their reasoning: The tektites would have rained down within 45 minutes to an hour of the impact, unable to create mudholes if the seabed had not already been exposed.

Instead, they argue, seismic waves likely arrived within 10 minutes of the impact from what would have been the equivalent of a magnitude 10 or 11 earthquake, creating a seiche (pronounced saysh), a standing wave, in the inland sea that is similar to water sloshing in a bathtub during an earthquake. Though large earthquakes often generate seiches in enclosed bodies of water, they're seldom noticed, Richards said. The 2011 Tohoku quake in Japan, a magnitude 9.0, created six-foot-high seiches 30 minutes later in a Norwegian fjord 8,000 kilometers away.

"The seismic waves start arising within nine to 10 minutes of the impact, so they had a chance to get the water sloshing before all the spherules (small spheres) had fallen out of the sky," Richards said. "These spherules coming in cratered the surface, making funnels -- you can see the deformed layers in what used to be soft mud -- and then rubble covered the spherules. No one has seen these funnels before."

The tektites would have come in on a ballistic trajectory from space, reaching terminal velocities of between 100 and 200 miles per hour, according to Alvarez, who estimated their travel time decades ago.

"You can imagine standing there being pelted by these glass spherules. They could have killed you," Richards said. Many believe that the rain of debris was so intense that the energy ignited wildfires over the entire American continent, if not around the world.

"Tsunamis from the Chicxulub impact are certainly well-documented, but no one knew how far something like that would go into an inland sea," DePalma said. "When Mark came aboard, he discovered a remarkable artifact -- that the incoming seismic waves from the impact site would have arrived at just about the same time as the atmospheric travel time of the ejecta. That was our big breakthrough."

At least two huge seiches inundated the land, perhaps 20 minutes apart, leaving six feet of deposits covering the fossils. Overlaying this is a layer of clay rich in iridium, a metal rare on Earth, but common in asteroids and comets. This layer is known as the K-T, or K-Pg boundary, marking the end of the Cretaceous Period and the beginning of the Tertiary Period, or Paleogene.

Iridium

In 1979, Alvarez and his father, Nobelist Luis Alvarez of UC Berkeley, were the first to recognize the significance of iridium that is found in 66 million-year-old rock layers around the world. They proposed that a comet or asteroid impact was responsible for both the iridium at the K-T boundary and the mass extinction.

The impact would have melted the bedrock under the seafloor and pulverized the asteroid, sending dust and melted rock into the stratosphere, where winds would have carried them around the planet and blotted out the sun for months, if not years. Debris would have rained down from the sky: not only tektites, but also rock debris from the continental crust, including shocked quartz, whose crystal structure was deformed by the impact.

The iridium-rich dust from the pulverized meteor would have been the last to fall out of the atmosphere after the impact, capping off the Cretaceous.

"When we proposed the impact hypothesis to explain the great extinction, it was based just on finding an anomalous concentration of iridium -- the fingerprint of an asteroid or comet," said Alvarez. "Since then, the evidence has gradually built up. But it never crossed my mind that we would find a deathbed like this."

Key confirmation of the meteor hypothesis was the discovery of a buried impact crater, Chicxulub, in the Caribbean and off the coast of the Yucatan in Mexico, that was dated to exactly the age of the extinction. Shocked quartz and glass spherules were also found in K-Pg layers worldwide. The new discovery at Tanis is the first time the debris produced in the impact was found along with animals killed in the immediate aftermath of the impact.

"And now we have this magnificent and completely unexpected site that Robert DePalma is excavating in North Dakota, which is so rich in detailed information about what happened as a result of the impact," Alvarez said. "For me, it is very exciting and gratifying!"

Tektites

Jan Smit, a retired professor of sedimentary geology from Vrije Universiteit in Amsterdam in The Netherlands who is considered the world expert on tektites from the impact, joined DePalma to analyze and date the tektites from the Tanis site. Many were found in near perfect condition embedded in amber, which at the time was pliable pine pitch.

"I went to the site in 2015 and, in front of my eyes, he (DePalma) uncovered a charred log or tree trunk about four meters long which was covered in amber, which acted as sort of an aerogel and caught the tektites when they were coming down," Smit said. "It was a major discovery, because the resin, the amber, covered the tektites completely, and they are the most unaltered tektites I have seen so far, not 1 percent of alteration. We dated them, and they came out to be exactly from the K-T boundary."

The tektites in the fishes' gills are also a first.

"Paddlefish swim through the water with their mouths open, gaping, and in this net, they catch tiny particles, food particles, in their gill rakers, and then they swallow, like a whale shark or a baleen whale," Smit said. "They also caught tektites. That by itself is an amazing fact. That means that the first direct victims of the impact are these accumulations of fishes."

Smit also noted that the buried body of a Triceratops and a duck-billed hadrosaur proves beyond a doubt that dinosaurs were still alive at the time of the impact.

"We have an amazing array of discoveries which will prove in the future to be even more valuable," Smit said. "We have fantastic deposits that need to be studied from all different viewpoints. And I think we can unravel the sequence of incoming ejecta from the Chicxulub impact in great detail, which we would never have been able to do with all the other deposits around the Gulf of Mexico."

Read more at Science Daily

A one-two punch may have helped deck the dinosaurs

Colored and black points mark the global distribution of mid-ocean ridges, with ages of 66 million years ago created at spreading rates above and below 35 millimeters a year, respectively. Colors indicate the maximum gravity anomaly within 2 degrees.

The debate goes on: What killed off the dinosaurs?

New University of Oregon research has identified gravity-related fluctuations dating to 66 million years ago along deep ocean ridges that point to a "one-two punch" from the big meteor that struck off Mexico's Yucatan peninsula, possibly triggering a worldwide release of volcanic magma that could have helped seal the dinosaurs' fate.

"We found evidence for a previously unknown period of globally heighted volcanic activity during the mass-extinction event," said former UO doctoral student Joseph Byrnes.

The study by Byrnes and Leif Karlstrom, a professor in the UO's Department of Earth Sciences, was published Feb. 7 in Science Advances. It details a record of volcanism preserved along the mid-ocean ridges, which mark the oceanic boundaries of tectonic plates. The evidence comes from changes in the strength of gravity above the seafloor.

The findings of the UO's National Science Foundation-supported study, Karlstrom said, point to a pulse of accelerated worldwide volcanic activity that includes enhanced eruptions at India's Deccan Traps after the Chicxulub impact. The Deccan Traps, in west-central India, formed during a period of massive eruptions that poured out layers of molten rock thousands of feet deep, creating one of the largest volcanic features on Earth.

The Deccan Traps region has been in and out of the dinosaur debate. Rare volcanic events at such a scale are known to cause catastrophic disturbances to Earth's climate, and, when they occur, they are often linked to mass extinctions. Huge volcanic events can eject so much ash and gas into the atmosphere that few plants survive, disrupting the food chain and causing animals to go extinct.

Since evidence of the meteor strike near present-day Chicxulub, Mexico, surfaced in the 1980s, scientists have debated whether the meteor or the Deccan Traps eruptions drove the extinction event that killed off all nonavian dinosaurs.

Progressively improving dating methods indicate that the Deccan Traps volcanoes already were active when the meteor struck. Resulting seismic waves moving through the planet from the meteor strike, Karlstrom said, probably fueled an acceleration of those eruptions.

"Our work suggests a connection between these exceedingly rare and catastrophic events, distributed over the entire planet," Karlstrom said. "The meteorite's impact may have influenced volcanic eruptions that were already going on, making for a one-two punch."

That idea gained strength in 2015 when researchers at the University of California, Berkeley, proposed that the two events might be connected. That team, which included Karlstrom, suggested that the meteorite may have modulated distant volcanism by generating powerful seismic waves that produced shaking worldwide.

Similar to the impacts that normal tectonic earthquakes sometimes have on wells and streams, Karlstrom said, the study proposed that seismic shaking liberated magma stored in the mantle beneath the Deccan Traps and caused the largest eruptions there.

The new findings at the UO extend this eruption-triggering in India to ocean basins worldwide.

Byrnes, now a postdoctoral researcher at the University of Minnesota, analyzed publicly available global data sets on free-air gravity, ocean floor topography and tectonic spreading rates.

In his analyses, he divided the seafloor into 1-million-year-old groupings, constructing a record back to 100 million years ago. At about 66 million years, he found evidence for a "short-lived pulse of marine magmatism" along ancient ocean ridges. This pulse is suggested by a spike in the rate of the occurrence of free-air gravity anomalies seen in the data set.

Read more at Science Daily

Why meteroids explode before they reach Earth

Our atmosphere is a better shield from meteoroids than researchers thought, according to a new paper published in Meteoritics & Planetary Science.

When a meteor comes hurtling toward Earth, the high-pressure air in front of it seeps into its pores and cracks, pushing the body of the meteor apart and causing it to explode.

"There's a big gradient between high-pressure air in front of the meteor and the vacuum of air behind it," said Jay Melosh, a professor of Earth, Atmospheric and Planetary Sciences at Purdue University and co-author of the paper. "If the air can move through the passages in the meteorite, it can easily get inside and blow off pieces."

Researchers knew that meteoroids often blew up before they reach Earth's surface, but they didn't know why. Melosh's team looked to the 2013 Chelyabinsk event, when a meteoroid exploded over Chelyabinsk, Russia, to explain the phenomenon.

The explosion came as a surprise and brought in energy comparable to a small nuclear weapon. When it entered Earth's atmosphere, it created a bright fire ball. Minutes later, a shock wave blasted out nearby windows, injuring hundreds of people.

The meteoroid weighed around 10,000 tons, but only about 2,000 tons of debris were recovered, which meant something happened in the upper atmosphere that caused it to disintegrate. To solve the puzzle, the researchers used a unique computer code that allows both solid material from the meteor body and air to exist in any part of the calculation.

"I've been looking for something like this for a while," Melosh said. "Most of the computer codes we use for simulating impacts can tolerate multiple materials in a cell, but they average everything together. Different materials in the cell use their individual identity, which is not appropriate for this kind of calculation."

This new code allowed the researchers to push air into the meteoroid and let it percolate, which lowered the strength of the meteoroid significantly, even if it had been moderately strong to begin with.

While this mechanism may protect Earth's inhabitants from small meteoroids, large ones likely won't be bothered by it, he said. Iron meteoroids are much smaller and denser, and even relatively small ones tend to reach the surface.

From Science Daily

Small collisions make big impact on Mercury's thin atmosphere

Scientists used models along with earlier findings from the MESSENGER mission to shed light on how certain types of comets influence the micrometeoroids that preferentially impact Mercury on the dawn side of the planet. Here, data from the Mercury Atmosphere and Surface Composition Spectrometer, or MASCS, instrument is overlain on the mosaic from the Mercury Dual Imaging System, or MDIS.

Mercury, our smallest planetary neighbor, has very little to call an atmosphere, but it does have a strange weather pattern: morning micro-meteor showers.

Recent modeling along with previously published results from NASA's MESSENGER spacecraft -- short for Mercury Surface, Space Environment, Geochemistry and Ranging, a mission that observed Mercury from 2011 to 2015 -- has shed new light on how certain types of comets influence the lopsided bombardment of Mercury's surface by tiny dust particles called micrometeoroids. This study also gave new insight into how these micrometeoroid showers can shape Mercury's very thin atmosphere, called an exosphere.

The research, led by Petr Pokorný, Menelaos Sarantos and Diego Janches of NASA's Goddard Space Flight Center in Greenbelt, Maryland, simulated the variations in meteoroid impacts, revealing surprising patterns in the time of day impacts occur. These findings were reported in the Astrophysical Journal Letters on June 19, 2017.

"Observations by MESSENGER indicated that dust must predominantly arrive at Mercury from specific directions, so we set out to prove this with models," Pokorný said. This is the first such simulation of meteoroid impacts on Mercury. "We simulated meteoroids in the solar system, particularly those originating from comets, and let them evolve over time."

Earlier findings based on data from MESSENGER's Ultraviolet and Visible Spectrometer revealed the effect of meteoroid impacts on Mercury's surface throughout the planet's day. The presence of magnesium and calcium in the exosphere is higher at Mercury's dawn -- indicating that meteoroid impacts are more frequent on whatever part of the planet is experiencing dawn at a given time.

This dawn-dusk asymmetry is created by a combination of Mercury's long day, in comparison to its year, and the fact that many meteroids in the solar system travel around the Sun in the direction opposite the planets. Because Mercury rotates so slowly -- once every 58 Earth days, compared to a Mercury year, a complete trip around the Sun, lasting only 88 Earth days -- the part of the planet at dawn spends a disproportionately long time in the path of one of the solar system's primary populations of micrometeoroids. This population, called retrograde meteoroids, orbits the Sun in the direction opposite the planets and comprises pieces from disintegrated long-period comets. These retrograde meteroids are traveling against the flow of planetary traffic in our solar system, so their collisions with planets -- Mercury, in this case -- hit much harder than if they were traveling in the same direction.

These harder collisions helped the team further key in on the source of the micrometeoroids pummeling Mercury's surface. Meteroids that originally came from asteroids wouldn't be moving fast enough to create the observed impacts. Only meteoroids created from two certain types of comets -- Jupiter-family and Halley-type -- had the speed necessary to match the obseravations.

"The velocity of cometary meteoroids, like Halley-type, can exceed 224,000 miles per hour," Pokorný said. "Meteoroids from asteroids only impact Mercury at a fraction of that speed."

Jupiter-family comets, which are primarily influenced by our largest planet's gravity, have a relatively short orbit of less than 20 years. These comets are thought to be small pieces of objects originating in the Kuiper Belt, where Pluto orbits. The other contributor, Halley-type comets, have a longer orbit lasting upwards of 200 years. They come from the Oort Cloud, the most distant objects of our solar system -- more than a thousand times farther from the Sun than Earth.

Read more at Science Daily

Ancient Space Dust Washes Up in Rooftop Gutters

Through dogged determination, Jon Larsen has become driven to find space particles, which date back to when our sun was a baby, in the urban sediment that collects in the guttering of building rooftops. And, after he convinced a British planetary scientist to study his findings, years of work have finally paid off.

In 2011, Larsen reached out to Matthew Genge, of Imperial College London, with his plan to find dust particles in this seemingly unlikely place. Though distinguishing space particles from the zoo of man-made dust particles in a city environment was considered too difficult, the hurdle didn't deter Larsen.

"It was an amateur scientist, a chap called Jon Larsen who's actually quite a well-known jazz musician in Norway, who got interested in this and started collecting all the debris that ends up in the gutter," Genge told Seeker. After going through the debris found in the roof guttering from buildings in Oslo, Paris and Berlin, Larsen would send photos of interesting particles he'd find to Genge and, despite his pessimism that Larsen would ever uncover this unlikely quarry, he eventually struck gold.

Now, with Genge's assistance, the pair have identified hundreds of particles that fell from space and have origins dating back to the birth of the solar system. Larsen documents his micrometeorite discoveries as part of Project Stardust.

"Imagine somebody who has been sending you pictures every other week of something, and every time you look at them, you're like 'no, no, no, that's not it' and then after 5 years they send you a picture and it actually is the thing that you're looking for... that was the moment I went 'oh, my God! I should pay more attention to this guy!'" Genge added.

"He's put in so much work. He went through 300 kilograms [660 lb] of sediment from gutters. That's pretty incredible."

As described in research published in the journal Geology, the duo identified 500 particles of dust that originate from asteroids and comets. But finding these cosmic artifacts in the dirt was just the beginning; their research has revealed some profound science about the space dust that is falling onto our heads right at this moment and could add another layer to our understanding about the building blocks of planets.

Our solar system is filled with dust from collisions between asteroids and venting from comets. The most visible sign of this dust encountering Earth are the meteor showers that light up the upper atmosphere as Earth orbits though one of the many dusty trails left behind these interplanetary vagabonds. However, the tiny particles that rain through the atmosphere as "shooting stars" burn up completely, leaving only a bright flash in their wake. Their journey comes to an abrupt end as a blaze of super-heated glory.

"These particles [in gutter sediment] are almost definitely not coming from meteor showers as that dust comes in too fast — it comes in at maybe 30 kilometers per second [67,000 miles per hour] — and it completely evaporates in the Earth's atmosphere," said Genges.

The gutter particles are thought to enter the atmosphere at a speed of around 12 kilometers per second (27,000 miles per hour) where atmospheric heating does inevitably heat up the particles, but the dust survives the fall. Judging by their size of around 0.3 millimeters, these are likely the fastest dust particles to survive the hot atmospheric entry, noted Genges. Through analysis of the 500 specimens, the researchers found there to be a mix of particles that originate from asteroids and others that originate from comets.

"We have found dust particles that we think come from comets and they are subtly different from those that come from asteroids ... they are carbon rich. Whereas the ones from asteroids look similar to the material from meteorites, that are also from asteroids," he added.

Separating the cosmic particles from plain old gutter dirt is no easy task, but the researchers used an important trait found in these space particles to their advantage — they contain minerals that make them magnetic. So, by magnetically separating the dirt under the microscope, these particles could be found.

"These [particles] are very similar to the cosmic dust from deep sea sediments," said Genges. "The main difference is that these are very young. Because they've been largely collected from roofs on commercial buildings, those buildings have their gutters cleaned at least every 3-5 years, so we know these [particles] have landed on Earth at least in the last 5 years. Whereas the particles found on the seabed are up to 50,000 years old. These are a sample of what's landing on Earth, practically today."

As this dust has fallen to Earth within the last 5 years, the researchers could even deduce how the solar system dust falling on Earth has changed over the last million years. The dust found in city gutters contains fewer crystals than the dust that has been found in million-year-old ice Antarctica, for example, but the particles are remarkably similar to cosmic dust that fell onto Earth in medieval times.

According to an Imperial College London press release, the researchers think that the changes in dust particle structure could be down to very small orbital changes in the solar system's planets over millions of years. The slight gravitational disturbances likely change the trajectory of the interplanetary dust, causing it to hit the Earth's atmosphere at different speeds and angles. These slight changes can therefore influence how much heating is caused by atmospheric entry which, in turn, influences the size of the particles that make it to the ground and influence the shape of the crystals inside the microscopic grains.

Read more at Discovery News

Perseid Meteor 'Outburst' Could Be Awesome

All predictions suggest there's going to be a spectacular meteor shower, so get outside and look up!

It's that time of the year when dust from Comet Swift-Tuttle rains down on our atmosphere, producing the famous Perseid Meteor Shower.

The shower, which peaks around Aug. 12 every year, rarely disappoints and is known to generate its fair share of bright meteors, colloquially known as "shooting stars." The Perseids are a favorite among amateur astronomers, particularly in the Northern Hemisphere as the warmer nights and (if you're lucky) clear summer skies allow comfortable and extended viewing sessions.

Also, as with every meteor shower, no specialist equipment is needed. You just need a comfortable spot, warm clothes (yes, even in the summer, as sitting and lying still for long periods can sap body heat) and patience.

But this year holds some extra excitement -- there's going to be an outburst... probably.

As a comet orbits the sun, it deposits ice and dust particles as a trail through interplanetary space called a meteor stream. You can imagine these streams as the contrail produced by aircraft; meteor streams trace out the paths the comets have taken during their various orbital circuits. Every year at around this time, the Earth passes into Comet Swift-Tuttle's dusty trail.

Over the tens to hundreds to thousands of years after being deposited in space, these meteor streams are influenced by the gravities of the planets (particularly Jupiter) and it just so happens that this year, three different meteor streams are coinciding as Earth orbits through them.

"This year Jupiter's influence has moved the 1079, 1479, and 1862 streams closer to Earth, so all forecasters are projecting a Perseid outburst with double double normal rates on the night of August 11-12," Bill Cooke, Head of NASA's Meteoroid Environment Office, told EarthSky.org.

So what does this mean for us? It could mean that we see up to 200 meteors per hour. But these are meteors and just because there's a statistically higher chance of seeing more meteors than usual, it's by no means a sure bet. Still, the models strongly suggest there will be an outburst, so don't miss it -- get outside and watch for those streaks of light.

Though the peak is likely to be observed from the night of Aug. 11 to the pre-dawn morning of Aug. 12, it's worth taking a look tonight (Aug. 10) as activity will be picking up. Just go outside, look for the Perseid "radiant" (the location in the sky the meteors appear to originate), which is the constellation of Perseus and get comfortable.

Want to find out more about the Perseids and chat with astronomy amateurs and professionals? Be sure to follow #MeteorWatch on Twitter and across other social media platforms to join in!

"The Perseid Meteor Shower will be at its most active over the next few days and I will be doing my yearly #MeteorWatch for it," Adrian West (@VirtualAstro), astronomer and organizer of the MeteorWatch.org website, told Discovery News. "I'm trying my best to make astronomy more popular and accessible and the Perseids are always a winner."

Read more at Discovery News

Look Up! Perseid Meteors Could be Supercharged

The Perseids are here: The dazzling meteor shower's peak of activity is Aug. 12, but you can already see its streaks of light peppering the sky.

Skywatchers are particularly excited about this year's Perseids. Though the meteor shower is an annual event, the Perseids are in outburst this year. That means that rather than 80 meteors per hour, we might see 150 to 200 per hour, according to NASA meteor expert Bill Cooke.

"Next, we move into the August Perseids, which is perhaps the most popular meteor shower of all," Cooke told Space.com in our summer meteor shower guide. "This year, they will be in what we call 'outburst' — their rates will double, because we're running into more material left behind by Comet Swift-Tuttle." [Perseid Meteor Shower 2016: When & How to See It]

The Perseid meteor shower occurs when Earth moves through the trail of dust and debris left by Comet Swift-Tuttle as it orbits the sun; the debris hits Earth's atmosphere and burns up, creating the white-hot streaks we see in the sky. Most of the pieces of debris, which move at 37 miles per second (59 kilometers per second), are about the size of a grain of sand, NASA has said.

Earth is passing through a particularly dense clump of debris this year — the source of the outburst — caused by the influence of Jupiter's gravity on Swift-Tuttle's trail. The number of meteors is increasing as Earth penetrates the heart of the debris, and it will diminish again once it passes through (after the peak).

The moon will be full six days after the meteor shower's peak, which might wash out the vivid streaks across the sky. So it might be a good idea to look earlier on, before the peak, to see the brightest streaks and fireballs, and to go to the darkest location you can, Cooke said. All of the meteors will appear to stream away from the constellation Perseus — that apparent source is called the shower's radiant — but will materialize all across the sky.

You don't need a telescope to see the meteors. In fact, because telescopes narrow your field of view, it's much easier to watch a meteor shower with the naked eye, just looking up at the entire sky. It will take around 30 minutes in the dark night for your eyes to adjust, and Cooke suggested to plan for a few hours outdoors, taking in the views. The Perseids will appear most clearly in the Northern Hemisphere after 10 p.m. local time, and the meteor rate will increase each night all the way until dawn.

Read more at Discovery News

Glass Beads in Australia Point to Huge Asteroid Hit

Australian scientists have found evidence of a huge asteroid they say slammed into Earth some 3.46 billion years ago — making it the second oldest known to have hit the planet and larger than the one blamed for wiping out the dinosaurs.

Andrew Glikson, from the Australian National University’s Planetary Institute, said that while the asteroid would have been massive, the exact location of where it hit was not known.

“The impact would have triggered earthquakes orders of magnitude greater than terrestrial earthquakes, it would have caused huge tsunamis and would have made cliffs crumble,” he said in a statement.

“Material from the impact would have spread worldwide.”

Speaking to AFP on Wednesday, Glikson said he and Arthur Hickman from the Geological Survey of Western Australia had found tiny glass beads called spherules, which are formed by vaporized material from an asteroid’s impact, in Australia’s remote northwest.

They were discovered in a sediment layer originally on the ocean floor and which had been preserved between two volcanic layers. It dates from 3.46 billion years ago.

“It is the second oldest known,” Glikson said of the asteroid, which was estimated to have been at least 20 kilometers (12 miles) across and to have created a crater hundreds of kilometers wide.

This makes it larger than the giant asteroid that collided with Earth some 66 million years ago and is widely blamed for the demise of the dinosaurs. That asteroid is estimated to have measured around 15 kilometers wide.

Tests on the beads found in Western Australia found levels of elements such as platinum, nickel and chromium corresponding with those found in asteroids, according to the scientists’ paper in Precambrian Research.

Glikson said while the find was evidence of the second oldest asteroid to hit Earth, there may have been other similar impacts that have yet to be discovered because asteroid craters from the period have been obliterated by volcanic activity and tectonic movements.

Read more at Discovery News

Jupiter Got Smashed by a Speeding Space Rock

Jupiter just took one for the team.

The gas giant appears to have experienced a pretty significant impact event and the flash of the extraterrestrial meteor was caught by amateur astronomers who just happened to be videoing Jupiter and its moons.

As the biggest and most massive planet in the solar system, the gas giant king isn’t unfamiliar with being hit by errant space rocks — Jupiter’s gravitational field is an interplanetary vacuum of sorts and is often viewed as the inner solar system’s protector. (Or is Jupiter a little more evil than that? We’re not entirely sure.) Any asteroid or comet that strays too close will be ripped to shreds and pulled into Jupiter’s unforgiving thick atmosphere at high speed.

According to Bad Astronomer Phil Plait, this latest Jupiter impact was reported by two amateur astronomers located in Austria and Ireland who saw the suspect flash on Jupiter’s limb at approximately the same time. It is unknown whether the flash was caused by an asteroid or a comet.

Having just one observer see the meteor would be interesting, but that would leave some ambiguity as to whether the flash was caused by a physical impact or a glitch in the observer’s camera CCD or some optical aberration in the telescope lens. But to have two observers seeing the event at the same time in the same place of Jupiter’s atmosphere is more than just chance. With more than one observer, the likelihood is pretty high that an asteroid or comet slammed into Jupiter on March 17.

See for yourself:

This footage was captured by “Gerrit” who is located in Mödling, Austria. The amateur astronomer only realized they had captured the flash after reviewing the video 10 days later. At the same time, John Mckeon, who was observing Jupiter from near Dublin, Ireland, also reported seeing the bright flash:

Videoing Jupiter isn’t an uncommon astronomical technique. Although on any given night you wouldn’t expect to see much action from the massive planet, the individual frames of a video are processed by astronomical imaging software and the individual frames are stacked to produce a high-resolution final image. This technique is used to remove the haze and turbulence caused by atmospheric effects. But very occasionally, these videos can capture the odd transient event, like a meteor flash.

Although seeing a bright flash across millions of miles of interplanetary space may give the impression that Jupiter was hit by something pretty big, as Plait mentions in his blog, the impactor wasn’t likely more than a few tens of meters wide. As Jupiter has a more powerful gravitational field than Earth, objects will hit the Jovian atmosphere around five-times faster than they hit Earth’s atmosphere. Greater velocity means more energy, so (from the kinetic energy equation E=1/2mv2) we’d expect an object hitting Jupiter to be carrying 25 times more energy than a comparable object hitting Earth’s atmosphere. This means 25 times more energy will be released on impact, producing a way bigger flash.

If you’re experiencing a little deja vu right now, you’re right, this certainly isn’t the first time amateur astronomers have witnessed Jupiter flashing.

In 2009, a significant impact was witnessed by amateur astronomer Anthony Wesley in Australia that, after some detective work, was found to be an asteroid impact. Then in 2010, Wesley was again looking in the right place at the right time to spot another large impact and confirmed by Philippines-based amateur astronomer Christopher Go.

Read more at Discovery News

Meteorites Peppered With Ancient Supernova Dust

Microscopic dust grains extracted from meteorites that landed on Earth had ancient and explosive origins, scientists have discovered.

The dust grains — also known as presolar grains, since they're older than Earth's sun — were likely spewed out by stars that blew up hundreds of millions of years before Earth's solar system formed. And in a new analysis of data collected from these tiny particles, researchers have come closer to pinpointing the type of stellar blast that produced the dust, 5 billion years ago.

To trace the origins of the stardust's subatomic "fingerprints," scientists built computer models simulating the explosive conditions that could have produced them, to test whether the dust grains' point of origin might have been an exploding white dwarf star in a double-star system.

Ancient Grains

This study adds to decades of analysis devoted to puzzling out the age and origins of these presolar grains, according to study co-author Christopher Wrede.

Wrede, an assistant professor of physics at Michigan State University, told Live Science in an email that researchers look at the grains' isotopes — variations of an element that have different numbers of neutrons. About a dozen grains held a great deal of the isotope silicon-30, which has been linked to a certain type of stellar explosion called a classical nova.

Classical novas — stellar eruptions that happen in a binary, or paired, star system — are different from supernovas, Wrede said, in that they are a type of explosion that can happen over and over again. The smaller star in a pair, a white dwarf, steals fuel from its larger neighbor, heating up its own surface and eventually blasting dust and gas into space.

"After a classical nova, the white dwarf can continue to siphon fuel from the companion and ignite again," Wrede said. "In a supernova, the entire star explodes, so it can only happen once."

Going Nuclear

When Earth's solar system was forming, collisions heated and mixed the building blocks of dust and gas, cooking them uniformly so that they shared many of the same isotopes. Grains with unusual isotopes — like silicon-30, which is rare on Earth — stand out, Wrede explained. "This tells us that they must have been produced prior to the formation of the solar system," dating back around 5 billion years, Wrede said.

Read more at Discovery News

Medium-Sized Asteroid Hit Could Unleash Ice Age

A strike by a medium-size asteroid could change Earth’s climate dramatically for a few years, making life difficult for people around the world, a new study suggests.

Such an impact on land (as opposed to at sea) could cause average global temperatures to plunge to ice age levels and lead to steep drops in precipitation and plant productivity, among other effects, researchers said.

“These would not be pleasant times,” Charles Bardeen, of the National Center for Atmospheric Research in Boulder, Colorado, said in December during a presentation at the annual fall meeting of the American Geophysical Union (AGU) in San Francisco.

Short-term climate change

Bardeen and his colleagues modeled what would happen to Earth’s climate if a 0.6-mile-wide (1 kilometer) space rock plowed into one of the planet’s landmasses. Such an impact would probably gouge out a crater about 9 miles (15 km) wide, throw huge amounts of dust into the atmosphere and trigger large-scale fires that lofted lots of soot into the air, provided the strike didn’t occur in a desert area with little vegetation, Bardeen said.

The material lofted after this hypothetical asteroid strike would stay in the atmosphere for a long time — about six years in the case of dust and 10 years for soot, according to the researchers’ results for the “worst-case scenario” (which assumed widespread fires).

These particles would warm in the sun, heating the stratosphere significantly and speeding up chemical reactions that destroy ozone, which protects Earth from harmful ultraviolet (UV) radiation. Indeed, atmospheric ozone would be temporarily reduced by 55 percent, causing the surface UV index to top 20 in the tropics for several years. (According to the U.S. Environmental Protection Agency, a UV index of 11 or above denotes “extreme risk of harm from unprotected sun exposure.”)

The atmospheric soot and dust would also reduce the amount of sunlight hitting Earth’s surface by up to 70 percent for the first year or two, Bardeen said. As a result, average global surface temperatures would cool by 14.5 degrees Fahrenheit (8 degrees Celsius), “which is about the equivalent of the ice ages,” Bardeen said during his AGU presentation.

The bulk of this temperature drop would occur on land, he added. But effects would be felt in the oceans as well; sea-ice cover would increase, and water has a high thermal inertia, so changes in ocean temperature would last for a relatively long time. For example, the team’s models suggest that the top layers of the ocean would still be about 0.9 degrees F (0.5 degrees C) cooler than normal 15 years after the asteroid impact.

The global cooling would also lead to a drop in precipitation of about 50 percent around the world, Bardeen said.

“This is due to the lost heating and the lost temperature, so we lose convection; we don’t have as many fronts,” he said.

The decrease in sunlight, rain and snow would lead to a roughly 50 percent drop in plant productivity — not good news for farmers and the people who depend on them (which is to say, everyone in the world). Crops in North America, Europe and northern Asia would be especially hard-hit, while agricultural lands in India, South America and Africa would not be affected as much, Bardeen said.

So, the overall picture is not pretty. A strike by a 0.6-mile-wide asteroid could cause “a very severe global impact” for several years, Bardeen said.

But a space rock would likely have to be about 10 times bigger to cause a mass extinction, he added. (The asteroid that’s thought to have wiped out the dinosaurs, along with many other species, 65 million years ago was probably about 6 miles, or 10 km, wide.)

Ocean impact?

Bardeen and his team modeled the aftermath of an asteroid strike on land. But it’s more likely that a space rock would come down in water, since oceans cover about 70 percent of Earth’s surface. What would happen then?

A 2010 modeling study by the late Elisabetta Pierazzo and her colleagues looked into this scenario, and determined that the effects on Earth’s protective ozone layer would be dramatic.

An ocean strike by a 0.6-mile-wide asteroid, the team found, would loft enough salty water vapor to destroy huge quantities of ozone, causing the surface UV index to spike temporarily to 56. Such high radiation levels, which have never been experienced in human history, would probably force people to stay inside during the day, Pierazzo said when the study came out.

Read more at Discovery News

Look Up! The Hunt for Leonid Meteors Is On

I recall it well: It was November 1999 and I had wrapped myself up in as many layers as I could and come midnight, I was out under a dark, clear sky with temperatures plummeting. Comfort was my watchword for the night, so I relaxed on a sun lounger, wrapped up and toasty warm in preparation for a long night's observing.

I remember seeing the Milky Way glistening away to the south and the moon was out of sight. The view that greeted me was one that I will remember for the rest of my life.

Unfortunately, this year’s Leonid meteor shower will likely not be as spectacular as the one I saw in 1999 when a meteor erupted overhead every few seconds. The shower peaks every year around Nov. 17 and 18 and is the result of an interaction between the Earth and remnants of the Comet Tempel-Tuttle. The comet travels around the sun and completes an orbit once every 33 years and, as it hurtles around the solar system, it leaves dusty debris along its orbit like a celestial trail of bread crumbs.

When Earth passes through the comet debris, which it does every year, the remnants of Tempel-Tuttle get swept up. If this happens to coincide with a recent passage of the comet then we can encounter storm levels of activity, igniting an impressive meteor display. Sadly, meteor shower forecasts suggest that we'll have to wait until 2032 for the next great display.

This week, instead of hundreds (or even thousands) of meteors per hour, this year's display is expected to peak at around 15 meteors per hour by the early hours of Wednesday (Nov. 18).

To understand why meteor activity tends to intensify during the hours after midnight, imagine a car travelling down a country road when it encounters a swarm of flies. As the car heads through the unsuspecting insects, they all get splatted by the front of the car. In a similar way, as the Earth plows through the stream of meteors, its the forward facing hemisphere of the Earth that gets the best display of splatted meteors. The Earth's spin makes sure that observers located on the forward facing side of the Earth will get the best view, and this happens in the few hours before dawn.

It's not just Nov. 17/18 that meteors from the Leonid display can be seen, they can be spotted any time from around Nov. 6 until the end of the month. To spot them, you need to wrap up warm, find a location far from any city lights and make yourself comfortable. While the peak is expected in the early hours of the 18th, it's a good idea to also keep an eye out on the 17th too as meteors care little for schedules!

You can tell if you have spotted a meteor from the Leonid shower by tracing its path backwards in the sky and seeing if it came from the constellation Leo -- then you will have bagged your first Leonid meteor. It is best not to look directly toward Leo, the best chances of spotting meteors are when you look either side -- just lie back and try to have an uninterrupted view of the sky. Typically, Leonids are fast, travelling through our atmosphere with speeds in excess of 45 miles (70 kilometers) per second!

Read more at Discovery News

Get Ready for Tonight's Perseid Meteor Shower Peak

Tonight is the peak of the annual Perseid meteor shower and whether you have clear or cloudy skies, there are more than a few surprising ways that you can get involved and enjoy a potentially spectacular cosmic light show.

First things first, assuming you do have clear skies, meteor viewing requires no specialist equipment. All you need to do is to, well, look up. Of course, standing around in the dark looking up for long periods of time isn’t terribly good for your neck, so you can take your observing session up a notch and recline in a comfy chair or even just lie on the floor. It’s a social event! Invite your friends, family and neighbors and make a night of it.

However, although it’s the middle of summer in the Northern Hemisphere, sitting or laying still for long periods of time at night, depending on the weather, can still get chilly, so be sure to keep warm and lay on something soft.

So, Where to Look?

As I said, “up” is a good place to start, and so long as your eyes have adjusted to the dark, you shouldn’t have any problems spotting the Perseid meteors (or “shooting stars”) flash across the sky. But if you want to be even more pro, make sure you know where the constellation of Perseus is in the sky. Perseus can be found in the northeast between the bright star of Capella (that will be rising above the horizon after 11 p.m. local time) and the constellation Cassiopeia. SPACE.com has a handy night sky rendering that can help you track down Perseus.

Why Perseus? Well, that’s the reason why the Perseids are named after this constellation — it just so happens that the meteors from this particular shower at this time of year appear to originate in the general direction of Perseus. This is what is known as a “radiant” and all the other annual meteor showers throughout the year have been named after the constellation they appear to be radiating from. However, it is not necessary to stare directly at Perseus to see tonight’s Perseid meteors, just be aware they will be coming from that direction and sweeping directly overhead.

Now you know what direction they’ll be coming from and you know where to look (hint: “up”), what are the Perseids anyway?

The Perseid meteors are tiny grains of dust that originate from the periodic comet Swift-Tuttle. During the comet’s 133 year trundle around the sun, the ancient icy body has left a trail of dust and ice particles in its wake — much like a cometary contrail — looping around the sun. It just so happens that this trail of comet dirt crosses Earth’s orbit and, at this time in the Earth’s 365 day orbit around the sun, we hit the dust as regular as clockwork.

As Earth passes through the comet’s trail, these particles — called meteoroids — hit our atmosphere at high speed. With high velocity comes high gas pressure in front of each falling dust grain, triggering a phenomenon called “ram pressure.” This process compresses the air in front of the meteor, causing the atmospheric gases to rapidly heat up to over 3,000 degrees Fahrenheit (1,650 degrees Celsius). If the meteoroid is small, it is the ram pressure heating, not atmospheric friction (a common misconception) that vaporizes it, creating a bright, transient meteor and short-lived ionization trail. Bigger meteoroids may generate a bright streak of light as a meteor and then erupt as an even brighter “fireball,” the largest of which may even generate a bang that can be heard on the ground.

Which brings me to my next point…

What if it’s Cloudy?

A meteor’s ionization trail is usually all that remains of the vaporized comet dust that has impacted our atmosphere. Composed of ionized gas (atmospheric gas molecules that have lost or gained electrons), these trails rapidly dissipate, but they can be used to detect the frequency of meteors raining through the upper atmosphere (at around 60 miles in altitude). These ionized gases bounce radio waves back to Earth, a signal anyone with an FM radio set can detect, even if it’s cloudy. Check out astronomer Mark Thompson’s guide on how to do meteor spotting with a radio.

Of course, it’s not just by sight and radio that you can get involved in tonight’s Perseids peak; there’s always the internet.

During every meteor shower, various social media platforms, particularly Twitter, buzz with the #MeteorWatch hashtag. Connected to the UK-based MeteorWatch.org website, you can monitor the skies and report your meteor sightings from wherever in the world. Your meteor report is then logged and plotted on a dynamic map. For instructions on how to get involved, check out the MeteorWatch website.

Also, Slooh.com will be hosting a live online event for the Perseids tonight at 5 p.m. ET/8 p.m. PT, featuring professional astronomers and live feeds from their telescopes.

And of course, NASA will also be in on the action, covering the meteor shower live online with a webcast and expert guides. Many other astronomical and space organizations will be hosting their own events.

So, if you have clear skies tonight, get out there and enjoy the cosmic fireworks. The best time to see the meteors is after midnight in the early hours of Thursday morning (Aug. 13) as, like mosquitoes hitting a car’s windshield, the leading hemisphere of our planet will be rotating into the comet dust cloud at that time.

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Company Aims to Offer On-Demand Meteor Showers

Skywatchers hoping to see a shooting star may soon be able to order them on demand.

A group of Japanese scientists say they have a shooting-star secret formula — an undisclosed chemical mixture packed into tiny, inch-wide balls that the team hopes to eject from a satellite to create on-demand meteor showers, AFP reports.

A Japanese start-up company called ALE is partnering with researchers at multiple universities to create the artificial meteor showers, which will cost around $8,100 per meteor for buyers. The researchers said the manufactured meteors would be bright enough to be visible even in areas with light pollution, like Tokyo, assuming clear weather.

Natural meteor showers occur when dust and debris from space are heated by friction as they pass through Earth’s atmosphere. Meteors often burn up completely before reaching the ground. (If they do strike the Earth, they become known as meteorites.) The artificial meteoroids, which would be launched from a microsatellite 20 inches (50 centimeters) across, would burn up on entry as well, after racing in at 5 miles (about 8 kilometers) per second, according to the piece by AFP reporter Miwa Suzuki.

The cubelike satellite that would release the artificial shooting stars is being developed by ALE in conjunction with the outside researchers. The satellite would orbit the Earth from north to south at an altitude of about 250 to 310 miles (400 to 500 km) for months at a time before falling back to Earth and burning up.

ALE is keeping the chemical makeup of the pellets it would launch secret, but the company revealed that it is considering different chemical compositions to create streaks of different colors.

“Making the sky a screen is this project’s biggest attraction as entertainment,” Lena Okajima, the company’s founder and CEO, told AFP. “It’s a space display.” In case of bad weather, the shooting stars could be called off up to 100 minutes before the planned spectacle.

And while the artificial meteor showers would be beautiful, they could also be valuable to scientists. An aerospace engineer at Tokyo Metropolitan University, Hironori Sahara, told AFP that analyzing the light from a meteor can tell scientists about the temperature, density and movement of the atmosphere at that elevation. Natural meteor showers are unpredictable, but scientists would know exactly where to look to study ALE’s meteors.

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