“Researchers capture first ‘image’ of a dark matter web that connects galaxies. Dark matter filaments bridge the space between galaxies in this false colour map. The locations of bright galaxies are shown by the white regions and the presence of a dark matter filament bridging the galaxies is shown in red.”
ELECTRICALLY CHARGED DUST STORMS
Flecks of Extraterrestrial Dust, All Over the Roof
by William J. Broad / March 10, 2017
“His book, “In Search of Stardust: Amazing Micro-Meteorites and Their Terrestrial Imposters,” due out in August, details the secret of his extraordinarily successful hunts. Its 150 pages and 1,500 photomicrographs, or photos taken through a microscope, tell how Mr. Larsen taught himself to distinguish cosmic dust from the minuscule contaminants that arise from roads, shingles, factories, roof tiles, construction sites, home insulation and holiday fireworks. As his book puts it, “To pick out one extraterrestrial particle among billions of others requires knowledge both about what to look for and what to disregard.”
The diminutive flecks to which Mr. Larsen, 58, has devoted himself represent the smallest parts of a cosmic downpour that has lashed the Earth for billions of years. Careful observers of the night sky are familiar with shooting stars — speeding bits of extraterrestrial rock that plunge through the Earth’s atmosphere, often burning up completely. The biggest can strike the ground, some forcefully enough to dig craters. In 2013, a relatively small rock exploded over the Russian city Chelyabinsk, releasing a shock wave that injured hundreds of people, mainly as windows shattered into flying glass.
But all that represents a tiny fraction of the downpour. Scientists say most of the cosmic material is remarkably small — barely the width of a human hair. Known as micrometeorites, they rain down on the planet more or less continuously but have proved remarkably hard to find. Some bits are so small and lightweight that they drift down to the Earth’s surface without melting. The dust consists of tiny remnants from the solar system’s birth, including debris from comets and from ages of smashups among planets and the big rocks known as asteroids. While most of the particles are interplanetary in nature, some contain grains of matter from outside the solar system, or true stardust. Their diversity makes them excellent windows on the cosmos.
“These examples of space dust found on Earth are collected in a new book, “In Search of Stardust: Amazing Micro-Meteorites and Their Terrestrial Imposters,” and were found on buildings, parking lots, sidewalks and park benches.”
Scientists have found micrometeorites mainly in the Antarctic, remote deserts and other places far from civilization’s haze. Starting in the 1940s and 1950s, investigators tried to find them in urban areas but eventually gave up because of the riot of human contaminants. Significantly, it turns out that specialists trying to establish the cosmic origins of the tiny specks have tended to examine their chemical signatures rather than their overall appearance. That left a large opening for Mr. Larsen. Matthew J. Genge, one of the Geology paper’s four authors and a senior lecturer in earth and planetary science at Imperial College, London, used an electron microprobe at the Natural History Museum in London to determine the chemical makeup of Mr. Larsen’s finds and confirm their cosmic origin.
In an interview, he said that, over all, the grains that survive the atmospheric plunge and land on the Earth’s surface add up to more than 4,000 tons annually, or more than 10 tons a day. “He’s done a valuable thing in classifying the contaminants,” Dr. Genge said of Mr. Larsen’s work. “It has wide-reaching implications.” Donald E. Brownlee, an astronomer at the University of Washington who helped establish the field, called Mr. Larsen a true citizen scientist whose work will aid the global hunt for the tiny specks. “Your car is covered with cosmic dust,” Dr. Brownlee said. “We inhale this stuff. We eat it every time we eat lettuce. But normally, it’s incredibly difficult to find.”
Mr. Larsen came to what he calls Project Stardust as a jazz guitarist in Norway, perhaps known best as the founder of Hot Club de Norvège, a string quartet. His group helped spur the global revival of gypsy jazz. As Mr. Larsen tells the story, he was an enthusiastic rock collector as a child but did so well as a musician that he set aside his early scientific ambitions. Then, in 2009, at a country house outside Oslo, he was cleaning an outdoor table when a bright speck caught his eye. “It was blinking in the sunlight,” he recalled. He touched the fleck. “It was angular in some way, kind of metallic but so small — a tiny dot.”
Intrigued, Mr. Larsen suspected it was a cosmic visitor and began to look for more. He collected dust samples from Oslo and cities around the globe, moonlighting as a scientist while vacationing or touring with his jazz group. He took samples from roads, roofs, parking lots and industrial areas Put indelicately, he collected hundreds of pounds of dreck — sludge from drains, gutters and downspouts, the dregs of civilization that most people try to avoid. “Still, I didn’t find a single micrometeorite,” he recalled. “It was very frustrating.”
Mr. Larsen then changed tactics. Rather than looking exclusively for cosmic dust, he taught himself how to classify the dozens of different kinds of earthly contaminants, starting a process of elimination that slowly narrowed the candidates and raised the chances that some tiny fraction of the urban debris might turn out to belong to the cosmos. The breakthrough came two years ago. In London, Dr. Genge studied one of the gathered particles — from Norway, not Timbuktu — and confirmed that it was indeed a traveler from outer space. Mr. Larsen quickly identified hundreds more. “Once I knew what to look for, I found them everywhere,” he said.
In the Geology paper, the scientific team reports the discovery of about 500 micrometeorites — collected mainly from roof gutters in Norway — and tells of the detailed analysis of 48 of the extraterrestrial specks. The team includes two of Dr. Genge’s students, Martin D. Suttle of Imperial College and Matthias Van Ginneken of the Université Libre in Brussels. The team described the cosmic dust as the youngest collected to date, because gutters tend to get cleaned fairly regularly. Also, urban surfaces are recent arrivals in the global landscape compared to polar ice and ancient deserts.
In his travels, Mr. Larsen recently visited with Michael E. Zolensky, an extraterrestrial materials scientist in Houston at the Johnson Space Center of the National Aeronautics and Space Administration. They not only talked shop but also went up to the roof of the large building that houses rocks from the Apollo moon program. “It was pretty cool,” Dr. Zolensky said. “The curation building is now a collector of cosmic dust.”
In an interview, Mr. Larsen described his method — sorting through the contaminants in a process of elimination — as “something that anybody can do. It could and should become part of teachings in schools, an aspect of citizen science.” Dr. Brownlee of the University of Washington agreed. He said that, while many schools try to find cosmic dust particles in programs meant to make science classes more inviting and accessible, few if any succeed. “It could help a lot,” he said of Mr. Larsen’s method. “For education, it’s pretty cool.” Dr. Genge of Imperial College said Mr. Larsen’s techniques, if adopted widely, might also open a new lens on the cosmos.
The gravitational pull of the planets, he noted, appear to tug on the dust clouds of the solar system and slowly change their orbits. He said a wave of new terrestrial finds could help scientists better map the clouds, raising more questions for science about the structure of the universe. “I consider my microscope a telescope,” Dr. Genge said. “It can give you a pretty big picture.”
“A 3-D visualization of reconstructed dark matter clump distributions in a distant galaxy cluster, obtained from the Hubble Space Telescope Frontier Fields data. The unseen matter in this map is comprised of a smooth heap of dark matter on which clumps form.”
Team puts dark matter on the map / March 1, 2017
“A Yale-led team has produced one of the highest-resolution maps of dark matter ever created, offering a detailed case for the existence of cold dark matter—sluggish particles that comprise the bulk of matter in the universe. The dark matter map is derived from Hubble Space Telescope Frontier Fields data of a trio of galaxy clusters that act as cosmic magnifying glasses to peer into older, more distant parts of the universe, a phenomenon known as gravitational lensing.
Yale astrophysicist Priyamvada Natarajan led an international team of researchers that analyzed the Hubble images. “With the data of these three lensing clusters we have successfully mapped the granularity of dark matter within the clusters in exquisite detail,” Natarajan said. “We have mapped all of the clumps of dark matter that the data permit us to detect, and have produced the most detailed topological map of the dark matter landscape to date.” Scientists believe dark matter—theorized, unseen particles that neither reflect nor absorb light, but are able to exert gravity—may comprise 80% of the matter in the universe. Dark matter may explain the very nature of how galaxies form and how the universe is structured. Experiments at Yale and elsewhere are attempting to identify the dark matter particle; the leading candidates include axions and neutralinos.
“While we now have a precise cosmic inventory for the amount of dark matter and how it is distributed in the universe, the particle itself remains elusive,” Natarajan said. Dark matter particles are thought to provide the unseen mass that is responsible for gravitational lensing, by bending light from distant galaxies. This light bending produces systematic distortions in the shapes of galaxies viewed through the lens. Natarajan’s group decoded the distortions to create the new dark matter map.
Significantly, the map closely matches computer simulations of dark matter theoretically predicted by the cold dark matter model; cold dark matter moves slowly compared to the speed of light, while hot dark matter moves faster. This agreement with the standard model is notable given that all of the evidence for dark matter thus far is indirect.”
ELECTRIC SAND DUNES
Saturn’s Weirdest Moon Is Full of Electric Sand
by Rae Paoletta / 3/29/17
“A new study from Georgia Tech, published on March 27th in Nature Geoscience, sought to shed light on the massive and mysterious sand dunes engulfing Titan. Through laboratory experiments, the researchers found that under Titan-like atmospheric conditions, sand grains collide and become electrically charged, clumping together and remaining clumped for an incredibly long time. While wind-blown sand on Earth can also become electrically charged, the electrostatic forces are typically ephemeral and much weaker. The team compared the adhesive quality of the sand on Titan to packing peanuts and cats. “If you grabbed piles of grains and built a sand castle on Titan, it would perhaps stay together for weeks due to their electrostatic properties,” Josef Dufek, the Georgia Tech professor who co-led the study, said in a statement. “Any spacecraft that lands in regions of granular material on Titan is going to have a tough time staying clean. Think of putting a cat in a box of packing peanuts.”
To reach this conclusion, the team created a modified pressure vessel and inserted naphthalene and biphenyl grains—hydrocarbon compounds similar in composition to what the sand is probably like on Titan. On Earth, naphthalene and biphenyl are considered toxic and are used moth balls and citrus fruit wrappings, respectively. The team then added Titan-like “wind” by rotating the tube for 20 minutes in pure nitrogen environment, since that’s what the moon’s atmosphere is almost entirely composed of. Overwhelmingly, the sand stuck together, which doesn’t happen on Earth unless you add water to the mix. Speaking of Earth, our sand is mostly silica-based, and didn’t have the same sticky quality when the researchers used it to repeat their experiments.
“Radar imaging from NASA’s Cassini spacecraft shows dunes stretching across the Shangri-La Sand Sea of Saturn’s largest moon, Titan. Research suggests the dunes’ shape and orientation are influenced by powerful electrostatic charges.”
“These non-silicate, granular materials can hold their electrostatic charges for days, weeks, or months at a time under low-gravity conditions,” study co-author George McDonald, said in a statement. The new study offers the latest indication that although Titan looks astonishingly similar to Earth—it’s the only other world in the solar system with surface oceans, for one—many of the processes shaping its surface are truly alien. “Titan’s extreme physical environment requires scientists to think differently about what we’ve learned of Earth’s granular dynamics,” Dufek said. “Landforms are influenced by forces that aren’t intuitive to us because those forces aren’t so important on Earth. Titan is a strange, electrostatically sticky world.”