African climate is generally considered to have evolved towards progressively drier conditions over the past few million years, with increased variability as glacial–interglacial change intensified worldwide.
Palaeoclimate records derived mainly from northern Africa exhibit a 100,000-year (eccentricity) cycle overprinted on a pronounced 20,000-year (precession) beat, driven by orbital forcing of summer insolation, global ice volume and long-lived atmospheric greenhouse gases4.
Here we present a 1.3-million-year-long climate history from the Lake Malawi basin (10°–14° S in eastern Africa), which displays strong 100,000-year (eccentricity) cycles of temperature and rainfall following the Mid-Pleistocene Transition around 900,000 years ago.
Interglacial periods were relatively warm and moist, while ice ages were cool and dry. The Malawi record shows limited evidence for precessional variability, which we attribute to the opposing effects of austral summer insolation and the temporal/spatial pattern of sea surface temperature in the Indian Ocean.
The temperature history of the Malawi basin, at least for the past 500,000 years, strongly resembles past changes in atmospheric carbon dioxide and terrigenous dust flux in the tropical Pacific Ocean, but not in global ice volume. Climate in this sector of eastern Africa (unlike northern Africa) evolved from a predominantly arid environment with high-frequency variability to generally wetter conditions with more prolonged wet and dry intervals.
The Transantarctic Mountains are the most remote mountain belt on Earth, an utterly pristine wilderness of ice and rock rising to majestic heights and extending for 1,500 miles. In this book, Edmund Stump is the first to show us this continental-scale mountain system in all its stunning beauty and desolation, and the first to provide a comprehensive, fully illustrated history of the region's discovery and exploration.
The author not only has conducted extensive research in the Transantarctic Mountains during his forty-year career as a geologist but has also systematically photographed the entire region. Selecting the best of the best of his more than 8,000 photographs, he presents nothing less than the first atlas of these mountains. In addition, he examines the original firsthand accounts of the heroic Antarctic explorations of James Clark Ross (who discovered the mountain range in the early 1840s), Robert Falcon Scott, Ernest Shackleton, Roald Amundsen, Richard Byrd, and scientists participating in the International Geophysical Year (1957–1958). From these records, Stump is now able to trace the actual routes of the early explorers with unprecedented accuracy. With maps old and new, stunning photographs never before published, and tales of intrepid explorers, this book takes the armchair traveler on an expedition to the Antarctic wilderness that few have ever seen.
“An Empire of Ice reflects exhaustive digging and reaches well beyond the standard source materials. . . . Larson provides enough fresh perspective that even devotees of polar literature will learn things.”—Jennifer Kingson, New York Times Book Review (Jennifer Kingson New York Times Book Review)
Awarded an Honorable Mention in the 2011 National Outdoor Book Awards (National Outdoor Book Award Honorable Mention National Outdoor Book Foundation)
“A far more interesting and richer account than we have had thus far. . . . Larson has written a fascinating book, one sure to force a rethinking of the Scott-Amundsen race as well as reconsiderations that will include science as a driving force in Antarctic and indeed polar exploration.” —Vassiliki Betty Smocovitis, Science Magazine (Vassiliki Betty Smocovitis Science Magazine)
"The author provides an undeniably exciting account without overpowering the reader with too much detail. Fans of these explorers, science heads, and armchair travelers will find this a worthwhile and thrilling read."—Mike Rogers, Library Journal (Mike Rogers Library Journal)
“Pulitzer Prize–winning historian Larson sheds new light on the famous three-way race to the South Pole….A satisfying tale of adventure and exploration.”—Kirkus Reviews
"...Fortunately, because the Sun is much brighter than the typical star, the one planet with a pleasant climate – Earth – lies so far away that it spins freely, so most latitudes enjoy a short (24-hour) cycle of day and night. However, solar tides have dramatically slowed the spins of Mercury and Venus. Mercury spins once every 58.65 days – exactly two-thirds of its 88-day-long year. As a result, the day is so hot that it could melt lead and the night is colder than on Saturn.
Solar tides have also slowed the spin of Venus, which revolves around the Sun every 225 days and rotates every 243 days. The slight mismatch arises, scientists believe, because winds in its thick atmosphere, whose surface pressure is 93 times the that of the Earth, rub against the planet's surface and alter its spin.
Leconte and his colleagues wondered what would happen if a planet with a thinner atmosphere, like that of the Earth, revolved close to an orange- or red-dwarf star. To their surprise, the calculations indicate that, in many cases, such a world can still rotate freely. For example, a planet orbiting a red-dwarf star that is 60% as massive as the Sun does not suffer tidal locking, even if it is only a third as far from the star as Earth is from the Sun. That distance puts the planet in the red-dwarf's habitable zone, where temperatures are pleasant and liquid water can exist. And if the planet's atmosphere is 10 times thicker than that of the Earth, the planet can be even closer and still rotate freely.
Locked yet lively
What are the implications for habitability? "It's a tricky question," Leconte says. On the one hand, the climate of a freely spinning planet can mimic Earth's. On the other hand, the day side of a tidally locked planet could also support life, because previous studies have found that an atmosphere can ferry heat to the night side, so that the air does not freeze and disappear...."
At 5:36 p.m. on March 27, 1964, a magnitude 9.2. earthquake – the second most powerful in world history – struck the young state of Alaska. The violent shaking, followed by massive tsunamis, devastated the southern half of the state and killed more than 130 people. A day later, George Plafker, a geologist with the U.S. Geological Survey, arrived to investigate. His fascinating scientific detective work in the months that followed helped confirm the then-controversial theory of plate tectonics.
In a compelling tale about the almost unimaginable brute force of nature, New York Times science journalist Henry Fountain combines history and science to bring the quake and its aftermath to life in vivid detail. With deep, on-the-ground reporting from Alaska, often in the company of George Plafker, Fountain shows how the earthquake left its mark on the land and its people -- and on science.
5 years ago: The Ragged Edge of the World: Encounters at the Frontier Where Modernity, Wildlands and Indigenous Peoples Meet by Eugene Linden.
"A pioneering work of environmental journalism that vividly depicts the people, animals and landscapes on the front lines of change's inexorable march.
A species nearing extinction, a tribe losing centuries of knowledge, a tract of forest facing the first incursion of humans-how can we even begin to assess the cost of losing so much of our natural and cultural legacy?
For forty years, environmental journalist and author Eugene Linden has traveled to the very sites where tradition, wildlands and the various forces of modernity collide. In The Ragged Edge of the World, he takes us from pygmy forests to the Antarctic to the world's most pristine rainforest in the Congo to tell the story of the harm taking place-and the successful preservation efforts-in the world's last wild places.
The Ragged Edge of the World is a critical favorite, and was an editors' pick on Oprah.com."
Ten Thousand Years from Tomorrow. Francois Sarrazin, Sorbonne Universités, UPMC Univ Paris 06, Muséum National d'Histoire Naturelle
Evolution in the Anthropocene Science 26 Feb 2016: Vol. 351, Issue 6276, pp. 922-923
“Most current conservation strategies focus on the immediate social, cultural, and economic values of ecological diversity, functions, and services (1). For example, the Intergovernmental Platform on Biodiversity and Ecosystem Services (2) mostly addresses the utilitarian management of biodiversity from local to global scales. However, besides urgent diagnosis and actions (3, 4), processes that occur over evolutionary time scales are equally important for biodiversity conservation. Strategizing for conservation of nature at such long time scales will help to preserve the function—and associated services—of the natural world, as well as providing opportunities for it to evolve. This approach will foster a long-term, sustainable interaction that promotes both the persistence of nature and the wellbeing of humans.
“Considering the evolutionary trajectories of nonhumans beyond human interest may also constitute a major evolutionary transition (5). It would be the first case in the history of life on Earth where a species cares for the evolution of other species beyond its own fitness and well-being.
“We must understand why the universe began in an incredibly special state, so well ordered that 14 billion years later, the universe still has not reached maximum disorder. Penrose is at his best when he explains this deep and beautiful mystery, and the book may be worth reading for this chapter alone.” —Science
Proto-Solar System's Magnetic Field. Ken Croswell, @sciencemagazine.
"Earth and its planetary neighbors arose in a magnetic field strong enough to sculpt the disk of gas and dust that spawned our solar system and set the stage for a planet capable of developing life. That's the implication of new work that uses a meteorite to deduce the strength of the magnetic field around the young sun.
"Planets arise in so-called protoplanetary disks, which orbit young stars but disperse after a few million years as material from the disk both falls into the star and gets pushed away. What causes this transfer of mass? Some researchers suspect magnetic forces do the job, but no one has ever measured a protoplanetary disk's magnetic intensity....
"Was the ancient magnetic field just the right strength to mold the sun's protoplanetary disk into a solar system containing a world of the right size at the right orbital distance to develop life? "I don't think we understand the processes well enough to really make that connection directly," Wilner says, "but it surely wouldn't surprise me if there were differences" in the properties of the sun's planets had the magnetic field been stronger or weaker."...
Ten thousand years ago, giant ice islands in America. @sidperkins @sciencemagazine
“…As the last ice age waned and climate warmed, immense lakes of glacial meltwater that accumulated behind natural ice dams occasionally burst forth from the mouth of Canada’s Hudson Bay and the Gulf of St. Lawrence. When those iceberg-laden outburst floods—some of them carrying more than 1 million cubic meters of water per second and lasting several months—reached the open sea, they took a right turn and flowed south along the coast as far as the Florida Keys, a new study suggests. The torrent-driven icebergs, some of them hundreds of meters thick, plowed troughs in the sea floor all along the continental shelf (like those found in 170- to 380-meter-deep waters off the coast of South Carolina; one such berm-edged trough extends from lower left to top center of the image). Sea levels have risen more than 100 meters since most of these troughs were formed, which has helped preserve them from surface waves that could roil and smooth seafloor sediments.
Unknown comets at the edge of the system. Bob Zimmerman, BehindtheBlack.com
Using data from the WISE space telescope, astronomers have found that there are more comets lurking in the far reaches of the solar system than they had predicted.
Scientists found that there are about seven times more long-period comets measuring at least 0.6 miles (1 kilometer) across than had been predicted previously. They also found that long-period comets are on average up to twice as large as “Jupiter family comets,” whose orbits are shaped by Jupiter’s gravity and have periods of less than 20 years. Researchers also observed that in eight months, three to five times as many long-period comets passed by the Sun than had been predicted.
These are comets whose orbits never allow them to come close to the inner solar system, which allows them to remain puffy and large.
Wind is an ever-present force. From a gentle breeze to a cold arctic blast, it is constantly shaping the landscape and the weather. But where does wind come from.
Simply put, wind is the motion of the air around us, generated by differences in pressure in the Earth's atmosphere. Air is a fluid, and just like water, it obeys the laws of fluid dynamics. It will seek to flow from a region of higher pressure to one of lower pressure, says Chris Maier, a meteorologist with the National Oceanic and Atmospheric Administration’s National Weather Service.
Earth's air-filled atmosphere is constantly but unevenly pressurized, with highs and lows at various places caused by the uneven heating of Earth’s surface by the sun. The air at the North or South Pole is colder and denser, while the air at the Equator is warmer and rises more easily. The colder, more highly pressurized polar air is constantly trying to move down to the Equator to replace the warm, rising air.
Read more: SMITHSONIAN
The very concept of the Anthropocene suggests that humans are actively shaping the planet in ways that will resonate through geologic time. But how has the planet—in this case, geography—shaped human societies since the days of our earliest ancestors.
In this week's episode of Generation Anthropocene, producer Mike Osborne talks with Ian Morris, a professor in the Stanford Archaeology Center and author of the 2010 book Why the West Rules—For Now. Morris developed a social development index to try to quantify the way societies and cultures have grown and changed with time. The index is based on four key factors: urbanization, information technology, war-making capacity and energy capture per capita, or how much food, water and other natural resources each person consumes.
Read more: SMITHSONIAN
Photo: Artist's conception of the surface of Proxima Centauri b. The Alpha Centauri binary system can be seen in the background, to the upper right of Proxima
ESO/M. Kornmesser - https://www.eso.org/public/images/eso1629a/
This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB also appears in the image to the upper-right of Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface.)
The mystery of the origin of Proxima b. Ken Croswell @nature
“…The habitability of planets like Proxima b—in the sense of sustaining an atmosphere and liquid water on its surface—is a matter of intense debate. The most common arguments against habitability are tidal locking, strong stellar magnetic fields, strong flares and high ultraviolet and X-ray fluxes; but none of these have been proved definitive. Tidal locking does not preclude a stable atmosphere via global atmospheric circulation and heat redistribution21. The average global magnetic flux density of Proxima is 600 ± 150 G (ref. 22), which is quite large compared with that of the Sun (1 G). However, several studies have shown that planetary magnetic fields in tidally locked planets can be strong enough to prevent atmospheric erosion by stellar magnetic fields23 and flares24. Because of its close orbit to Proxima, Proxima b suffers from X-ray fluxes that are approximately 400 times that experienced by Earth, but studies of similar systems indicate that atmospheric losses can be relatively small25. Further characterization of such planets can also inform us about the origin and evolution of terrestrial planets. For example, the formation of Proxima b from in situ disk material is implausible because disk models for small stars would contain less than 1M⊕ of solids within a distance of 1 AU. There are three possibilities: the planet migrated in via type I migration26; planetary embryos migrated in and coalesced at the current planet’s orbit; or pebbles/small planetesimals migrated via aerodynamic drag27 and later coagulated into a larger body. Although migrated planets and embryos that originate beyond the ice-line would be rich in volatiles, pebble migration would produce much drier worlds. A warm terrestrial planet orbiting Proxima offers the opportunity to attempt further characterization via transits (ongoing searches), by direct imaging and high-resolution spectroscopy in the next decades28, and possibly robotic exploration in the coming centuries29…”
Curiosity rescued by engineering magicians. Bob Zimmerman, BehindtheBblack.com
Improved software uploaded to Curiosity to extend wheel life.
Engineers have designed and uploaded new software to Curiosity to better protect and use the rover’s wheels as it travels over rough terrain.
The software, referred to as traction control, adjusts the speed of Curiosity’s wheels depending on the rocks it’s climbing. After 18 months of testing at NASA’s Jet Propulsion Laboratory in Pasadena, California, the software was uploaded to the rover on Mars in March. Mars Science Laboratory’s mission management approved it for use on June 8, after extensive testing at JPL and multiple tests on Mars.
The timing is important, because Curiosity is about to move into terrain that looks far rougher than the ground it has so far traversed.
(Photo: English: This artists concept contrasts our familiar Earth with the exceptionally strange planet known as 55 Cancri e. While it is only about twice the size of the Earth, NASA's Spitzer Space Telescope has gathered surprising new details about this supersized and superheated world.
Astronomers first discovered 55 Cancri e in 2004, and continued investigation of the exoplanet has shown it to be a truly bizarre place. The world revolves around its sun-like star in the shortest time period of all known exoplanets just 17 hours and 40 minutes. (In other words, a year on 55 Cancri e lasts less than 18 hours.) The exoplanet orbits about 26 times closer to its star than Mercury, the most Sun-kissed planet in our solar system. Such proximity means that 55 Cancri e's surface roasts at a minimum of 3,200 degrees Fahrenheit (1,760 degrees Celsius).
The new observations with Spitzer reveal 55 Cancri e to have a mass 7.8 times and a radius just over twice that of Earth. Those properties place 55 Cancri e in the "super-Earth" class of exoplanets, a few dozen of which have been found. However, what makes this world so remarkable is the resulting low density derived from these measurements. The Spitzer results suggest that about a fifth of the planet's mass must be made of light elements and compounds, including water. In the intense heat of 55 Cancri e's terribly close sun, those light materials would exist in a "supercritical" state, between that of a liquid and a gas, and might sizzle out of the planet's surface.
Only a handful of known super-Earths, however, cross the face of their stars as viewed from our vantage point in the cosmos. At just 40 light years away, 55 Cancri e stands as the smallest transiting super-Earth in our stellar neighborhood. In fact, 55 Cancri is so bright and close that it can be seen with the naked eye on a clear, dark night.
Date 26 September 2011, 13:20:58
Author NASA/JPL-Caltech/R. Hurt (SSC))
Mystery of the birth of Earth: Where are the Super-Earths? @kbatygin @caltech http://web.gps.caltech.edu/~kbatygin/Home.html
"...Now, for the first time, researchers have seen this scenario unfold. Andrew Vanderburg, an astronomer at the Harvard-Smithsonian Center for Astrophysics, was analyzing data from Kepler, which detects planets when they block the light of their sun. "One of the white dwarfs suddenly popped up with this really intriguing signature," Vanderburg says. As his team reports online today in Nature, the white dwarf, located in the constellation Virgo and named WD 1145+017, has at least one, and probably several, asteroids that are disintegrating. As a debris cloud from each asteroid passes between us and the star, Kepler detects a dimming of the star's light.
"It's fascinating," says astronomer Michael Jura of the University of California, Los Angeles, who was not part of the discovery team. "They've actually caught in the act the process of some asteroid breaking into pieces, being disrupted by the white dwarf host star."
Indeed, the star itself is the asteroids' enemy. Its gravity has torn them asunder, and its light is vaporizing their rock. The asteroids are so close to the star that they revolve in just 4.5 to 4.9 hours; Vanderburg estimates they are roughly the size of Ceres, the largest asteroid between the orbits of Mars and Jupiter...."
The theoretical physicist Krauss, author of several books about physics, including The Physics of Star Trek (1995), admits up front that he is not “sympathetic to the conviction that creation requires a creator.” The book isn’t exclusively an argument against divine creation, or intelligent design, but, rather, an exploration of a tantalizing question: How and why can something—the universe in which we live, for example—spring from nothing? It’s an evolutionary story, really, taking us back to the Big Bang and showing how the universe developed over billions of years into its present form. Sure to be controversial, for Krauss does not shy away from the atheistic implications of a scientifically explainable universe, the book is full of big ideas explained in simple, precise terms, making it accessible to all comers, from career physicists to the lay reader whose knowledge of the field begins and ends with a formula few understand, E=mc². —David Pitt
"In A Universe from Nothing, Lawrence Krauss has written a thrilling introduction to the current state of cosmology—the branch of science that tells us about the deep past and deeper future of everything. As it turns out, everything has a lot to do with nothing—and nothing to do with God. This is a brilliant and disarming book." — Sam Harris, author of The Moral Landscape
"Astronomers at the beginning of the twentieth century were wondering whether there was anything beyond our Milky Way Galaxy. As Lawrence Krauss lucidly explains, astronomers living two trillion years from now, will perhaps be pondering precisely the same question! Beautifully navigating through deep intellectual waters, Krauss presents the most recent ideas on the nature of our cosmos, and of our place within it. A fascinating read." —Mario Livio, author of Is God A Mathematician? and The Golden Ratio
"In this clear and crisply written book, Lawrence Krauss outlines the compelling evidence that our complex cosmos has evolved from a hot, dense state and how this progress has emboldened theorists to develop fascinating speculations about how things really began." —Martin Rees, author of Our Final Hour
“A series of brilliant insights and astonishing discoveries have rocked the Universe in recent years, and Lawrence Krauss has been in the thick of it. With his characteristic verve, and using many clever devices, he’s made that remarkable story remarkably accessible. The climax is a bold scientific answer to the great question of existence: Why is there something rather than nothing.” —Frank Wilczek, Nobel Laureate and Herman Feshbach professor at MIT, author of Th...
Click to set custom HTML
“Preservation of Earth-forming events in the tungsten isotopic composition of modern flood basalts” How much of Earth's compositional variation dates to processes that occurred during planet formation remains an unanswered question. High-precision tungsten isotopic data from rocks from two large igneous provinces, the North Atlantic Igneous Province and the Ontong Java Plateau, reveal preservation to the Phanerozoic of tungsten isotopic heterogeneities in the mantle. These heterogeneities, caused by the decay of hafnium-182 in mantle domains with high hafnium/tungsten ratios, were created during the first ~50 million years of solar system history, indicating that portions of the mantle that formed during Earth’s primary accretionary period have survived to the present.