Microscopic fragments of DNA were found in Ice Age sediment in northern Greenland. Using cutting-edge technology, researchers discovered the fragments are one million years older than the previous record for DNA sampled from a Siberian mammoth bone.
The discovery was made by a team of scientists led by Professor Eske Willerslev and Professor Kurt H. Kjær. Professor Willerslev is a Fellow of St John’s College, University of Cambridge, and Director of the Lundbeck Foundation GeoGenetics Center at the University of Copenhagen where Professor Kjær, a geology expert, is also based.
“A new chapter spanning one million extra years of history has finally been opened and for the first time we can look directly at the DNA of a past ecosystem that far back in time,” so Professor Willerslev commenting the discovery.
“DNA can degrade quickly but we’ve shown that under the right circumstances, we can now go back further in time than anyone could have dared imagine.”
Professor Kjær adds that “the ancient DNA samples were found buried deep in sediment that had built-up over 20,000 years. The sediment was eventually preserved in ice or permafrost and, crucially, not disturbed by humans for two million years.”
The incomplete samples, a few millionths of a millimeter long DNA strings, were taken from the København Formation, a sediment formation almost 100 meters thick deposited in the shallow area of a fjord in Greenland’s northernmost point. The climate in Greenland at the time of sedimentation was between 10 to 17 degrees warmer than today, sustaining an ecosystem with no present-day equivalent, resembling a mix of temperate forest and mixed-grass prairie.
Detective work by 40 researchers from Denmark, the UK, France, Sweden, Norway, the U.S. and Germany, unlocked the secrets of the fragments of DNA. The process was painstaking – first they needed to establish whether there was DNA hidden in the sediment, and if there was, could they successfully detach the DNA from the mineral grains – like clay particles and quartz crystals – to examine it? The answer, eventually, was yes. The researchers compared every single DNA fragment with extensive libraries of DNA collected from present-day animals, plants and microorganisms.
The scientists discovered evidence of animals, plants and microorganisms including reindeer, hares, lemmings, birch and poplar trees. They even found that Mastodon, an Ice Age elephant, roamed as far as Greenland before later becoming extinct. Previously it was thought the range of the species did not extend from its known origins of North and Central America.
Some of the DNA fragments were easy to classify as predecessors to present-day species, others could only be linked at genus level, and some originated from species impossible to place in the DNA libraries of animals, plants and microorganisms still living today.
The findings have opened up a whole new period in DNA detection. Thanks to a new generation of extraction and sequencing equipment, researchers will be able to locate and identify extremely small and damaged fragments of genetic information in sediments considered previously unfit for DNA preservation.
“DNA generally survives best in cold, dry conditions such as those that prevailed during most of the period since the material was deposited at Kap København. Now that we have successfully extracted ancient DNA from clay and quartz, it may be possible that clay may have preserved ancient DNA in warm, humid environments in sites found in Africa,” Professor Willerslev concludes.
The paper “A 2-million-year-old ecosystem in Greenland uncovered by environmental DNA” is published in Nature. Material provided by the by University of Cambridge.
Why I Hunt for Sidewalk Fossils – The New York Times
These oft-overlooked records invite us to imagine what has been and what might be.
A paleontologist once told me that city sidewalks hold snapshots. If I trained my gaze toward my feet, he said, I would find evidence of all kinds of commutes: traces of hopping birds, the soles of humans’ shoes, restless leaves that fell and sank into wet concrete at just the right moment. I might see a smattering of little paw prints zigging, zagging, doubling back, evidence of important rodent business that didn’t often overlap with mine.
These marks are too recent to pass muster with scientific sticklers, but in all respects except age, they are fossils. There are many ways to make one. Some form when a creature is entombed in sediment: Water percolates through, flush with minerals, and over time the mixture infiltrates the bones, where it settles and forms stone. Other fossils are casts, made, for instance, when a shell dissolves and leaves behind a mold that eventually fills with sediment, which hardens into rock. But not all fossils involve remains; some catalog movements. These are the kind that stipple our sidewalks — nascent trace fossils, records of fleeting contact.
Throughout the pandemic, I turned to nature to track time and step outside myself. I photographed the sweetgum tree outside my Brooklyn window, noting when it leafed into a bushy chlorophylled curtain or when it dropped fruit that fell to the ground like unshattered ornaments. Most afternoons of that first lonely spring, I roamed a cemetery. When magnolia blossoms smudged the scene pink, I stood under the canopies until wind splashed the petals against my shoulders.
I was lucky, of course, to be simply scared and lonely — not dead, not intubated, not choosing between peril and paycheck. But time was slippery, and I felt stuck in my own brain, a foggy, trembling ecosystem I had no interest in studying. By early 2022, I was cocooned in my partner’s Morningside Heights apartment. On weekend mornings, we shuffled around the neighborhood, and each volunteered to notice something new: a startling mushroom, the pale bellies of pigeons waterfalling down a facade before flocking skyward. I became fixated on sidewalk fossils. Fossil-finding outings were a relief — an invitation to crouch, touch, lose myself in evidence of skittering and scrabbling, tethering myself to a past and a future.
Once I started noticing these impressions, it was fun to imagine myself as a paleontologist of the urban present.
Because sidewalk fossils are essentially the same color as the surrounding concrete, they’re most visible when light rakes across them; a fossil that’s elusive at noon might announce itself at dawn or dusk. So I timed a second daily walk for the hour when the light fled. Late afternoons introduced me to tiny forked footprints that marked the scene of, perhaps, an avian skirmish. There were others: a dog’s paws, three-quarters of a shoe. Though ichnologists, who study trace fossils, might discount leaves, I marveled at those too: most of a London plane and a ginkgo, with its corrugated fan. Across from a closed-up snack cart, I knelt until the cold concrete prickled my knees. I wriggled out of my mitten and traced a leaf’s sharp, diagonal veins, its saw-toothed sides.
When scientists encounter a fossil, they often try to puzzle out an explanation of how it got there. Maybe an animal was stranded or washed off its feet or chased by predators. Once I started noticing these impressions, it was fun to imagine myself as a paleontologist of the urban present. A bonanza of bird feet made me wonder if someone had sprinkled seeds or dropped a bagel. How long ago? What kind? When a leaf didn’t seem to match any of the nearby trees, I wondered if it was an interloper, blown in from blocks away or if it testified to an ecological eviction — a tree yanked out and replaced with another species or swapped for sidewalk. The fossils fastened my attention to something tangible but also invited it to wander and to think about city streets as collages of past and present, about how our nonhuman neighbors are architects, too. How we all shed traces of ourselves, whether we know it or not.
Of course, there is more significant proof of the past. Mammoths sometimes turn up in farmers’ fields, their tusks curved like scythes abandoned in the dirt. Parades of dinosaur footprints still march along the banks or beds of some prehistoric rivers and seas. Those are awesome, showy and obvious. I line up to see them; I happily gawk. But it was a tiny thrill to encounter evidence of the past that was subtle and recent, proof that others were out there. The sidewalk fossils felt intimate — the paleontological equivalent of a raft of letters secreted away beneath a floorboard.
Only they’re not actually rare. When sidewalks are repaired, birds and other animals ignore attempts to keep them pristine. Leaves do whatever the wind demands. These fossils are easy to find, and we’re lucky to have them. When I was lingering in the worst parts of my brain, sidewalk fossils dislodged me. Unlike the many fossils that represent stillness, the moment when an animal died and the place it remained unless humans carved it free, sidewalk fossils are often peeks into lives that continued. The birds flew somewhere; the dogs, I hope, went on to wag over many sticks and smells. As the sun sank and I trudged home, the fossils — these little flukes, these interesting accidents — were reminders of small, exhilarating life.
Jessica Leigh Hester is a science journalist whose first book is “Sewer” (Bloomsbury Academic, 2022).
Green comet expected to be visible for first time in 50 millennia – Al Jazeera English
Comet C/2022 E3 (ZTF) is visible with binoculars, telescopes and in some areas, the naked eye – and it will grow brighter.
A green-hued comet is expected to be the most visible to stargazers on Wednesday as it shoots past Earth and the sun for the first time in about 50,000 years.
Discovered less than a year ago, the dirty snowball last passed near Earth during Neanderthal times, according to NASA.
The cosmic visitor will swing by our planet within 42 million kilometres (26 million miles) Wednesday before speeding away again, unlikely to return for millions of years.
This harmless comet already is visible in a clear northern night sky with binoculars and small telescopes, and possibly the naked eye in the darkest corners of the Northern Hemisphere.
It’s expected to brighten as it draws closer and rises higher over the horizon through the end of January, and is best seen in the predawn hours. By February 10, it will be near Mars, a good landmark.
Stargazers in the Southern Hemisphere will have to wait until next month for a glimpse.
Finding a remote location to avoid light pollution in populated areas is key to catching a nice view of the comet as it journeys past our planet heading away from the sun and back toward the solar system’s outer reaches.
While plenty of comets have graced the sky over the past year, “this one seems probably a little bit bigger and therefore a little bit brighter and it’s coming a little bit closer to the Earth’s orbit,” said NASA’s comet-and asteroid-tracking expert, Paul Chodas.
Nicknamed “dirty snowballs” by astronomers, comets are balls of ice, dust and rocks and wander towards the inner solar system when they’re dislodged from various gravitational forces, becoming more visible as they venture closer to the heat given off by the sun.
Fewer than a dozen comets are discovered each year by observatories around the world.
The green comet was discovered on March 2, 2022 by astronomers using the Zwicky Transient Facility, a wide-field camera at Caltech’s Palomar Observatory in Palomar Mountain, California, the United States. That explains its official, cumbersome name: comet C/2022 E3 (ZTF).
Its greenish, emerald hue reflects the comet’s chemical composition – it is the result of a clash between sunlight and carbon-based molecules in the comet’s coma, the cloud around the nucleus that makes the comet appear fuzzy in the sky.
This comet last passed Earth at a time when Neanderthals still inhabited Eurasia, the human species was expanding its reach beyond Africa, big Ice Age mammals including mammoths and saber-toothed cats roamed the landscape, and northern Africa was a wet, fertile and rainy place.
The comet can provide clues about the primordial solar system because it formed during the solar system’s early stages, according to California Institute of Technology physics professor Thomas Prince.
NASA plans to observe the comet with its James Webb Space Telescope, which could provide clues about the solar system’s formation.
The Virtual Telescope Project at the Bellatrix Astronomical Observatory in Ceccano, Italy will have a live feed accessible here.
The comet — a time capsule from the emerging solar system 4.5 billion years ago — came from what’s known as the Oort cloud well beyond Pluto. This deep-freeze haven for comets is believed to stretch more than one-quarter of the way to the next star.
While comet ZTF originated in our solar system, we can’t be sure it will stay there, NASA’s Chodas said. If it gets booted out of the solar system, it will never return, he added.
But don’t fret if you miss it.
“In the comet business, you just wait for the next one because there are dozens of these,” Chodas said. “And the next one might be bigger, might be brighter, might be closer.”
USask researcher and Nobel laureate Herzberg predicted source of comet's green hue in 1939 – USask News
“It’s important to pay attention to celestial events like this because they are often how we learn about our world,” said Dr. Daryl Janzen (PhD), an astronomy expert and instructor in the Department of Physics and Engineering Physics at USask’s College of Arts and Science. “Science itself was essentially invented because people noticed that the planets follow wandering paths through the stars and wanted to explain that.”
Janzen also co-ordinates public outreach activities for the USask Observatory, which is open for public viewing of celestial objects on the first and third Saturdays of each month.
Like many other comets, Comet 2022 E3 (ZTF) gives off a distinct green colour from its bright head as it arcs across the sky. The puzzle of the exact cause of this green coloration has been solved in recent years, thanks in part to Herzberg.
Herzberg, winner of the Nobel Prize in chemistry in 1971 and a groundbreaking researcher who conducted much of his foundational work at USask from 1935-1945, spent his career studying the structure and geometry of molecules using spectroscopy, the study of the absorption and emission of light and radiation by matter. His studies led to innovative understandings of how molecules and atoms function and interact, and formed the basis of many advancements in astronomy, health, chemistry, and physics.
Herzberg began studying the diatomic molecule, C2, as early as 1937 while he was at USask. C2 is formed because carbon (C) is a relatively unstable element and attempts to stabilize itself by bonding itself with a second carbon molecule. His work eventually evolved into an analysis of how C2 may be of interstellar importance. A prediction Herzberg made in analyzing the spectroscopy of C2 laid the foundations for our current understanding of why colours appear in comet comas—the cloud of dust and gas that surrounds a comet’s head.
According to work published in 1939 in The Astrophysical Journal, Herzberg speculated that the cause of a comet’s green hue could be due to sunlight causing C2 to reach a high level of vibration, which causes the two molecules to break their bond and disassociate. It was thought the ripping apart of these molecules released energy emitted as a green colour.
This prediction remained unconfirmed for almost a century due to the difficulty of testing such a scenario. In December 2021, a University of New South Wales team published a research paper in the Proceedings of the National Academy of Sciences that tested Herzberg’s theory for the first time. Through a lab experiment, the research team showed that C2 molecules disassociate at high vibrational levels and cause a green light to emit from a comet’s coma. This discovery provided scientific proof of what Herzberg suspected back in 1939.
“Comet comas are typically green, and as Herzberg predicted, the colour comes from photo-dissociation of diatomic carbon, which is an abundant molecule in comets,” said Janzen. “This recent study confirmed that C2 has a lifetime of roughly two days until sunlight breaks the molecule apart and emits a green photon. It’s not just the colour, but this short timeframe that explains why the green light comes only from the coma and not the comet’s tail.”
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