On the outskirts of Colorado Springs, researchers have uncovered thousands of fossils showing how life on Earth revived in the aftermath of an asteroid impact 66 million years or so ago that killed most dinosaurs and other life on land and sea.
Taken together, the fossil trove documents an era when evolution, in essence, hit the reset button. While countless species vanished forever, some plants and animals rebounded relatively quickly in the first million years after the devastation, including the mammals ancestral to humankind, the scientists said in research published Thursday in Science.
“This is the age of mammals rising from the ashes of the age of dinosaurs,” said paleobotanist Ian Miller at the Denver Museum of Nature & Science who is a project co-leader. “It really informs how our world came to be today.”
Most mammals were wiped out, but the survivors quickly took hold in the new world. The number of diverse mammal species doubled within 100,000 years of the event, the scientists said. Some of the new species were up to three times as large as those alive right after the blast.
At the same time, ferns reclaimed the wasteland. Over 700,000 years or so, that carpet of ground cover was replaced by groves of palms and then by forests of walnut and other trees, which offered new food sources for rapidly evolving mammals, the scientists said.
“What they have here is pretty remarkable,” said paleontologist Michael Novacek, provost of science at the American Museum of Natural History in New York, who wasn’t involved in the project. “It is supportive of the notion that the evolution of modern mammals has something to do with the recovery from the extinction event.”
The find is the latest in a series of discoveries this year that reveal details of a moment long ago when a city-sized asteroid exploded into the sea near present-day Mexico with the force of a million nuclear warheads. The cosmic hammer blow triggered earthquakes, tidal waves, a global rain of red-hot debris and so much dust that it blocked sunlight world-wide for decades, scientific studies say.
Earlier this week, geoscientists who analyzed the chemistry of fossil plankton from the period said that the oceans rapidly became lethally acidic after the impact, perhaps from storms of acid rain generated by the fallout of pulverized sulfur-rich rocks. That may have eradicated half of all marine life, they said.
Their analysis, published in the Proceedings of the National Academy of Sciences on Monday, suggested it took 40,000 years for sea life to begin its recovery.
on land resuscitated itself in the aftermath.
After decades of searching, Dr. Miller and his colleagues found that evidence where they least expected it: on a stretch of gullies, grassland and stream beds in the southwestern corner of the Denver Basin called Corral Bluffs, where archaeologists and paleontologists had been studying the past off and on since the 1930s. In all that time, only a few fossil fragments had been found there from the era of the asteroid impact.
In 2016, the scientists turned their attention to long-ignored balls of sediment called concretions that littered the area. Such rocks sometimes form around a fossil as a core material, the way a pearl takes shape around a grain of sand.
“I remember seeing one really ugly white amorphous blob,” said vertebrate paleontologist Tyler Lyson at the Denver Museum, who was a project co-leader. “I picked it up, cracked it open with my rock hammer and I could see the cross section of a small skull looking back at me. I almost had tears in my eyes. It was pure elation.”
His colleagues quickly cracked open four more concretions, finding mammal skulls inside each one. “We were finding a skull about every 15 minutes once we figured out what to look for,” said Dr. Miller. “It happened that quickly.”
Across 10 square miles or so (27 square kilometers) of the outcrop, they so far have found more than a thousand animal fossils. The scientists also found thousands of plant specimens from the period, including leaves, stumps, branches and entire saplings. All of them date to the time of recovery after the impact.
Dozens of the fossils will be exhibited at the Denver Museum, the scientists said. The project also is the subject of a new Nova documentary produced for WGBH Boston by the Tangled Bank Studios at the Howard Hughes Medical Institute.
“It is going to set the standard going forward,” said early mammal expert Gregory Wilson at the University of Washington in Seattle. “I’ll be using this as a measuring stick, looking at terrestrial recovery from the mass extinction event.”- WSJ
Two weeks ago, we published a photo by Paul Smith of an awesome red sprite over Oklahoma. Red sprites are a type of transient luminous event (TLE), different from the more familiar lightning that takes place in the troposphere, or lowest part of Earth’s atmosphere. A related phenomena are the blue jets, which pulse from the tops of intense thunderstorms and reach up toward the edge of space. In 2015, European Space Agency (ESA) astronaut Andreas Mogensen photograped blue jets from the International Space Station. A subsequent analysis of the video footage by researchers at Denmark’s National Space Institute – published in early 2017 – revealed some amazing results!
In the 18th century, Europe's scientific community was torn between two opposing theories: Descartes' argument that the Earth was spherical, and Newton's contention that it was flattened at the poles. Recognizing that the answer was the key to securely navigating the earth's oceans, France and Spain organized a joint expedition to colonial Peru. Their goal was to measure a degree of latitude at the Equator; by comparing this measurement to one taken back in Europe, they would be able to determine the planet's shape and put an end to the debate. But what seemed a straightforward scientific exercise was almost immediately marred by a series of unforeseen catastrophes: treacherous terrain, deeply suspicious locals, and the voyagers' own hubris. A thrilling tale of adventure, political history, and scientific discovery, Larrie D. Ferreiro's Measure of the Earth recounts the greatest scientific exhibition of the Enlightenment through the eyes of the men who completed it—pioneers who overcame tremendous adversity to traverse the towering Andes Mountains and discern the Earth's true shape. - Amazon
Ice sheets such as those on Greenland and Antarctica today not only respond to changing climate but also can cause climate to change. Their sizes have fluctuated substantially in the past. In particular, Antarctica was effectively ice-free until its ice cover began to expand rapidly at the Eocene-Oligocene boundary around 34 million years ago. Recent research helps to identify the mechanisms that led to this rapid ice sheet growth. http://science.sciencemag.org/content/352/6281/34
Like early explorers mapping the continents of our globe, astronomers are busy charting the spiral structure of our galaxy, the Milky Way. Using infrared images from NASA's Spitzer Space Telescope, scientists have discovered that the Milky Way's elegant spiral structure is dominated by just two arms wrapping off the ends of a central bar of stars. Previously, our galaxy was thought to possess four major arms.
The annotated artist's concept illustrates the new view of the Milky Way. The galaxy's two major arms (Scutum-Centaurus and Perseus) can be seen attached to the ends of a thick central bar, while the two now-demoted minor arms (Norma and Sagittarius) are less distinct and located between the major arms.
SPIRAL GALAXY COMPARATIVE ANALYSIS SLIDESHOW