Global Sea Temperatures As High As Never In Last 800,000 Years

The sea surface temperatures (SST) of the last interglacial, some 129,000 to 116,000 years ago, were similar to temperatures we are approaching nowadays. The Eemian was one of the warmest interglacial periods, short pulses of rapid warming during the longer ice ages, in the last 800,000 years. Sea level was 19 to 29ft higher as today as large portions of the polar ice melted. Until now the correlating sea temperatures were debated. A now published paper analyzed 104 previous publications dealing with sea surface temperatures in the past and as recorded in marine sediments. The temperatures were compared to modern reference periods spanning from 1870-1889 and 1995-2014.
 

At the beginning of the Eemian, 129,000 years ago,  SST were similar to the 1870-1889 period. 4,000 years later the temperature rose by 0.5°C with values similar to the second modern reference period from 1995-2004. The results suggest that most models underestimated the rate of modern sea surface temperatures rise in response to man-made climate change and that SST will still significantly rise in the future. With higher temperatures also the ice will melt as happened during the Eemian. A sea level rise of at least 19 to 29ft will significantly impact coasts all over the planet.

In the Dolomites during the Eemian temperatures were so high that vegetation could be found 3,200ft higher than today, this cave with cave bear remains was at the time probably surrounded by a forest, providing sustainment to the bears.

The true treasure of the North

GOLD! GOLD! GOLD! found in the Klondike river in the Yukon territory, Alaska. The news spread like wildfire, fueling the last great gold-rush of the United States in 1896-99.
 

Fig.1." The Prisoner of White Agony Creek" (2008).

Also French businessman Loicq de Lobel decided in 1898 to try his luck in the new world. Even if not directly interested in searching for gold, he hoped to make a living by selling equipment to the prospectors. So the family de Lobel, his wife and four children, following the famous Chilkoot Trail ventured into the northern wilderness, first by feet and later by boat. To distract herself from the perils of the voyage, de Loicq´s wife, which name is not recorded, botanized along the way. She collected for the very first time specimens of the endemic lady's-slipper orchid, Astralagus, bearberry, Epilobium, arnica and a blue-flowering bellflower.

 “… everywhere there were nice flowers, at our arrival at Glenora we found lots of flowering plants...”
 

The de Lobel family lived for a time in the Yukon territory, then moved to the Aleuten Islands, to finally return to France. The Klondike Gold Rush ended as suddenly as it began, only few found great riches and fortune. However the collected plants by the de Lobel became known as “Klondike River Herbarium” and represents still today a unique botanic treasure.

Bibliography:

THINARD, F. (2013): Das Herbarium der Entdecker - Humboldt, Darwin & Co. - botanische Forscher und ihre Reisen. Haupt-Verlag: 168

Clash of the Titans: The Science behind the Iceberg that sank the Titanic

The tragedy of the “unsinkable” Titanic – lost in the cold water of the Atlantic – became part of history and pop culture, but the story of the main culprit that caused the disaster is mostly forgotten and only vague descriptions and some photos exists of the supposed iceberg(s). One famous photography taken from board of the cable ship “Minia“, one of the first ships to reach the area in search for debris and bodies, shows a tabular iceberg, an unusual shape for icebergs in the northern Atlantic. The crew found debris and bodies floating in the vicinity and the captain assured that this was the only iceberg near the point of the collision. However most surviving Titanic testimonies described later the infamous iceberg with a prominent peak or even two.

Fig.1. The moment of the collision according to the sailor Frederick Fleet - one of the two men on duty as lookout in the night of the disaster (after EATON & HAAS 1986).

Fig.2. Journalist Colin Campbell, a passenger of the "Carpathia" - the first ship to approach the scene of the disaster the next morning and save the surviving passengers of the Titanic - described the iceberg for the "New York Tribune" (after EATON & HAAS 1986).

Fig.3. One of the many icebergs photographed in the morning of April 15, 1912. The passengers on the ship “Prinz Adalbert”, still unaware of the disaster of the previous night, reported later to have noted a “red smear” at the waterline of the white iceberg.

Fig.4. Photography of an iceberg from the cable ship "Minia", one of the first ships to reach the area in search for debris and bodies. The crew found debris and bodies floating in the vicinity of the depicted iceberg and the captain assured that this was the only iceberg near the scene of the collision (after Titanic & Nautical Resource Center).

Fig.5. Another iceberg, photographed five days later from board of the German ship “Bremen”, claimed to be the Titanic iceberg based on the vicinity to the location of the disaster and the description of the iceberg according to survivors. An "authentic" photography of the iceberg that sank theTitanic was worth a lot of money for the eager press, this also explain why so many photographs of icebergs were taken at the time.

Fig.6. Photography taken from board of the ship “Birma” of the same iceberg as seen by the passengers of the “Carpathia” (see also Fig.2.) – the first ship to approach the scene of the disaster and save the surviving passengers of the Titanic – and published at the time in the “Daily Sketch”. This iceberg has in fact some remarkable similarities to the iceberg as described by survivors of the disaster.  
Despite the question if one of the photos shows really the culprit iceberg, the remarkably number of spotted icebergs emphasizes the notion that in 1912 a quite impressive number of these white titans reached such southern latitudes.

The icebergs encountered in the North Atlantic originate mainly from the western coasts of Greenland, where ice streams deliver large quantities of ice in the fjords which lead to the Baffin Bay. Every year ten-thousand of small and large pieces of ice drop from the front of the glaciers and are pushed by the West Greenland Current slowly to northern latitudes, far away from ship routes. Following first the coast of Greenland this current is diverted by the Canadian coast to the south, forming the Labrador Current that circumnavigates Newfoundland and delivers the iceberg to the warm Gulf Stream. A more than 5.000km long journey full of obstacles and incessant erosion by the sun, the water and the waves. Only estimated 1 to 2% of large icebergs will, after a period of 1-3 years, reach latitude 45°N, crossing one of the most important route for ships of the entire Atlantic Ocean.

Fig.7. Schematic map of marine currents (blue= cold; red = hot) around Greenland, probable region of origin (West Greenland) and hypothetical route of the iceberg that hit the Titanic.

Apparently in 1912 icebergs were spotted remarkably often in this region and various hypotheses tried to explain this “anomaly”.  The years before 1912 were characterized by mild winters in Europe and possibly the northern Atlantic. It was therefore speculated that the (relative) warm temperatures increased the melting rate and activity of the calving glaciers on Greenland. 
Also a strengthened Labrador Current, pushing cold water and icebergs much more to the south, was proposed to explain the ice field that in the cold night 100 years ago forced various ships to stop along the Atlantic route. 
Both  hypotheses are based on the recorded values of Sea Surface Temperature (see this diagram by the Woods Hole Oceanographic Institution), which show an alternation of a warm and cold period  in 1900-1920.
A recent hypothesis – promoted by NG – proposes that an exceptional high tide prevented much of the larger icebergs to run, as normally would happen, on ground along the coasts of Baffin Bay. However considering that this tide occurred just some months before (January 1912) and the average velocity of an iceberg is low (0,7km/h~0,6mph), the Titanic iceberg had to take a straight course to arrive in time for his rendezvous with history – April 14, 1912.

Based on iceberg counts along the shores of Labrador and later in the Atlantic, also the year 1912 don’t seem to be necessarily such an anomalous event, but the disaster raised considerably the interest (and maybe perception) of the public for icebergs.

Fig.8. Iceberg counts (estimated before 1912) at 48°N, data compiled from the International Ice Patrol Iceberg Database.

In the days after the disaster bypassing ships encountered and photographed various icebergs. Some eyewitnesses claim to have noted red paint on some of them; however there is no conclusive evidence that one of these spotted white giants is really the iceberg that sank the Titanic. At least some weeks later the culprit iceberg, captured by the warm water of the Gulf Stream, melted and disappeared forever into the Atlantic Ocean.

Bibliography:

EATON, J.P. & HAAS, C.A. (1986): Titanic Triumph and Tragedy. Haynes Publishing: 352
SOUTH, C. et al. (2006): The Iceberg That Sank the Titanic. The Natural World documentary film – BBC

The Geology of Star Trek: II. It is not Life as we know or understand it!

It may surprise that there is no exact definition of what “life” is -  it is often described as a system in thermodynamic disequilibrium with it´s own environment and therefore forced to actively seek, incorporate and transform matter and energy. Part of the acquired energy and matter is used by this system to create copies of itself and so to survive it´s own death.

Some of these properties are however shared also by inorganic entities, like the order, growth or twinning of crystals, and a virus can´t grow or replicate without infecting a living cell.
 

"It is not life as we know or understand it!", Mister Spock in the episode „Operation Annihilate” and still from the episode “The Devil in the Dark”

Living bacteria were found in boreholes in 5.278 m depth, on the bottom of oceans, acid and toxic lakes, in hot springs with temperatures of 115°C and in rocks of Antarctica, thriving at -50°C.  Part of this success is explained by the molecular structure of these life forms, as carbon-based molecules are stable in a wide range of temperatures and in acid or basic solutions. 

Mister Spock is well aware of this fact:
 

“Life as we know it, is universally based on some combination of carbon compounds.”
 

However when the crew of the Enterprise is contacted in the episode “The Devil in the Dark” by the miners on Janus VI, supposedly attacked by an unstoppable “monster”, soon this fact is questioned. The creature can´t be tracked by the sensors of the Enterprise, nor by the tricorder and seems immune to direct hits with the phasers.
 

“But what if life exists, based on other element. For instance silicon.”
 

McCoy disagrees with Spock´s deduction, noting that it is a physiological impossibility, however Kirk agrees as it may improbable, but not impossible. Already in 1891 the German astrophysicist Julius Schreiner argued that silicon (Si) could replace carbon in molecules supporting complex chemical reactions and therefore a hypothetical metabolism. Three years later science-fiction author H.G. Wells speculated in an article of popular science about such life forms:
 

“One is startled towards fantastic imaginings by such a suggestion: visions of silicon - aluminium organisms – why not silicon-aluminium men at once? – wandering through an atmosphere of gaseous sulphur, let us say, by the shores of a sea of liquid iron some thousand degrees or so above the temperature of a blast furnace.”
 

In theory, silicon could form polymers and complex compounds together with metals or elements like boron, nitrogen, phosphorus and sulfur (in fact almost all known minerals involve silicon). Such molecules could work also in other liquids than water, liquids like liquid nitrogen, methane, ammonium, various alcohols and even acid solutions.
 

The Horta, as the mysterious native life form of Janus VI refers to itself, defends itself and digs tunnels in solid rock using a strong acid. It´s curious to note that certain acids, like sulfuric and hydrocyanic acid could act as solutions for an extraterrestrial metabolism.
 

However silicon as replacement to carbon has also it´s disadvantages. Complex silicon compounds are unstable and ineffective under terrestrial conditions. McCoy notes this, claiming that silicon life would not survive in the artificial (?) human environment created on Janus VI. But as it seems the creature called Horta comes from within the planet, where may suitable conditions exist. Silicon life forms may could exist in oxygen-free or poor  (as oxygen would oxides the silicon molecules), dry and very cold environments.  Such for humans highly prohibitive conditions would also reduce the metabolism and reproduction rate of this hypothetical life form, may we would not even realize that it is alive. In the Star Trek episode the Horta is the last of it´s kind, only the eggs – appearing to us like inanimate silicon-concretions - survive, however needing thousands of years to develop and be finally ready to hatch.
 

One of the great strengths of Star Trek was to pose both ethic as intriguing scientific questions, may some will be answered by future generations, when they one day may really encounter life, but not as we know it ... I find that a fascinating vision for the future!
 

Bibliography:
 

FOURESTIER, J. de (2005): The Mineralogy of Star Trek. Axis, Vol.1(3): 1 - 24
PICKOVER, C.A.(1999): The Science Of Aliens. Basic Books: 240
SHOSTAK, B. (2012): Life in the Universe. Addison-Wesley Publisher: 544
SCHULZ-MAKUCH, D. & IRWIN, L.N. (2006): The prospect of alien life in exotic forms on other worlds. Naturwissenschaften. Vol.93: 155-172

Men Of Rock & The Big Freeze

How the Study of Plants revealed the Variability of Climate

The news of the resuscitated "Ice Age plant", regenerated from 30.000 year old tissue conserved in permafrost, is an intriguing discovery that will help to better understand the evolution of ecosystems during one of the most dramatic epochs of earth history - the Pleistocene-Holocene transition some 10.000 years ago, characterized by strong climatic oscillations from glacial to interglacial conditions.

Already the study of fossil plants played an important role in the reconstruction of the environment and the climate of this period.  The German explorer Alexander von Humboldt (1769-1859) was one of the first naturalists to scientifically discuss the distribution of plants related to environmental factors like temperature, rainfall, latitude, height and soil - one of the most famous results of this work is the depiction of the vegetation belts of the Andes.

Fig.1. Vegetation zonation in the Andes, from the "Berghaus-Atlas", a supplement to Humboldt´s work "Kosmos", published in 1645-1862.

Based on these observations it became clear that the fossil remains of plants can be used to reconstruct the environmental factors during the lifetime of these plants.
In 1876 the Norwegian botanist Axel Gudbrand Blytt (1843-1898) published a book on his observations about the distribution of the Ice Age flora on the Scandinavian Peninsula. He recognized various plant communities - defined as Arctic, Subarctic, Boreal, Atlantic, Subboreal and Subatlantic - and suggested, based also on layers of peat where he observed the same plant communities in a certain order, that these communities were the results of various climate driven migrations waves on the peninsula. For Blytt especially the change of dry and wet periods controlled the distribution and migration of plants. These supposed changes could also explain the discoveries of layers with tree stumps in peats all over Europe, grown there when the climate was more favourable for trees. 

Fig.2. Blytt´s map of the distribution of plant communities in Norway, from BLYTT 1876.

The Swedish geologist Lennart von Post (1884-1951) used particular plant remains to infer past climatic oscillations. Flowering plants produce pollen grains covered by a chemically very stable substance named Sporopollenin, therefore pollen grains usually are well preserved in soils and sediments. The structures, like spikes or pores, on the surface of pollen grains are species-specific and can be used to determine from which plant-species the pollen was produced. Von Post counted and identified many hundred of pollen grains found in specific depth-intervals of sediment cores and plotted the relative percentage of every species in a diagram. He found that there was a succession of different plants; cold periods during an Ice Age were dominated by pollen from trees adapted to cold and humid conditions, like birch or pine. During warmer periods the pollen of these species disappeared and new tree species, like oak and fir, appeared in the pollen diagram. When the landscape finally became occupied by humans the amount of tree pollen decreases, as the forest is replaced with fields of grass or crop and the pollen of these plants dominate in the sediment core. 

The study of pollen, or palynology, is still today an important tool that helps to reconstruct local environment and climatic changes, the stratigraphy of recent deposits, human impact on the landscape, the rise and fall of civilizations and is even used to solve criminal cases.

Bibliography:

BLYTT, A. (1876): Essay on the Immigration of the Norwegian Flora during Alternating Rainy and Dry Periods. Alb. Cammermeyer, Christiana, Oslo, Norway: 89
HILGEN, F.J. (2010): Astronomical dating in the 19th century. Earth-Science Reviews 98: 65-80
POST, V. L. (1944): The Prospect for Pollen Analysis in the Study of the Earth´s Climate History. New Phytologist Vol. 45: 198-203

At the Mountains of Madness

December 14, was the 100 years anniversary of the first expedition to reach the geographic South Pole in the middle of the continent of Antarctica. Until then only segments of the coasts were known and partially mapped.  

Fig.1. The dog Chris inspecting a grammophone during the Scott Expedition in Antarctica  (photo by Herbert George Ponting, 1911).

It is no wonder that such an unknown land influenced the imagination of many writers and later film directors. 

"At the Mountains of Madness" is a science-fiction/horror story by the American writer H. P. Lovecraft (1890-1937), written in February/March 1931 and originally published in three parts in the February, March and April 1936 issues of the pulp-magazine "Astounding Stories" (also one of the first pulp- and horror fiction magazines ever to be published).
The story is written in a first-person perspective by geologist William Dyer, a professor from Miskatonic University, which led a geological expedition to Antarctica in "1930".
The expedition discovers first strange fossils, eons of years older then all other signs of life on our planet, and finally a mountain range, much higher and darker then ever imagined. But after a carefully investigation along the borders of the mountains and the discovery of even more strange fossils, contact get lost with a part of the team and the narrator makes his way to discover what happened at the Mountains of Madness.
Lovecraft incorporates in his story many scientific observations made at the time, especially the discovery of fossils. Little was known about the geology of Antarctica; rock exposures comprise only 1-3% of the land area and are limited to isolated coastal regions and to the peaks of the Transantarctic Mountains, crossed for the first time by the Ernest Shackleton-expedition in 1908. Only in 1928-1930 the Richard Evelyn Byrd-expedition collected the first fossils.
Still today sites with fossils are rare spots; from Antarctica we know some dinosaur species, synapsid species, a plesiosaur, Eocene mammals and a terror bird - however plant remains are by far the most common fossils and especially these plants proofed that Antarctica was once a tropical paradise.
Lovecraft describes the fictional discovery of a cave that acted as sediment trap for millions of years:

"Washed down from unknown jungles of Mesozoic tree ferns and fungi, and forests of Tertiary cycads, fan palms, and primitive angiosperms, this osseous medley contained representatives of more Cretaceous, Eocene, and other animal species than the greatest paleontologist could have counted or classified in a year."

Also other authors located a tropical Lost World near the Antarctic continent. Edgar Rice Burroughs (1875-1950) published in 1918 the first part of a science-fiction book in the "Blue Book Magazine": "The Land That Time Forgot". Here a primordial world populated by tropical forests and of course dinosaurs is located on the island of Caprona, a land mass near Antarctica, first reported by the (fictitious) Italian explorer Caproni in 1721. The tale inspired two movies: "The Land That Time Forgot"(1975) and "The People That Time Forgot"(1977).

Fig.3. Cover art for first combined edition (1924) of The Land That Time Forgot.

It Came From the Ice!

“I am forced into speech because men of science have refused to follow my advice without knowing why. It is altogether against my will that I tell my reasons for opposing this contemplated invasion of the antarctic - with its vast fossil hunt and its wholesale boring and melting of the ancient ice caps. And I am the more reluctant because my warning may be in vain.”
"At the Mountains of Madness" (1931/1936) by H. P. Lovecraft (1890-1937)

One of the most classic monster of movies is without doubt the "mummy", mostly of Egyptian origin and with human shape (despite the fact that thousands of Egyptian mummies of various animals are known). Still today we are fascinated by the effort put into the preservation of a body, the ultimate victory above decay, corruption and finally death himself.
But there are not only artificial mummies, nature offers various methods to create "natural mummies". Corpses can be preserved in bog deposits - to acid for decomposing organism -  or tar pits - to poorly oxygenated - or permafrost - to cold for an effective decomposition of organic matter.

Natural mummies discovered in permafrost of ice age mammals offers a broad spectrum for research: taxonomic relations and dispersal history can be studied trough the ancient DNA, the structure of soft tissue can be observed in detail, paleo diet can be inferred by the gut contents and faeces, on some carcasses the circumstances of death can be observed - some animals show injuries, pathological deformations or tissue changes and parasites.
In the Siberian permafrost the best preserved specimens are those of mammoths, especially young and small individuals like the 40.000 years old mammoth calfs "Dima" (discovered in 1977) and "Lyuba" (2007); one of the oldest specimens is the 50.000 years old male "Khroma" (2009). 

The carcass of Khroma, partially eaten by modern scavengers, was discovered in July 2009 by a local hunter on the banks of the river Khroma. A preliminary study showed that in the carcass fossil germs were preserved, most probably anthracis, which can cause anthrax and black lung disease.  To prevent any possible contamination of involved researchers it was decided to sterilize the specimen. The still frozen carcass was therefore bombarded with a massive dose of Gamma-rays in a laboratory in Grenoble. 
Bacteria can theoretically survive long periods when frozen. In 2007 an international research team announced the discovery of 500.000 years old bacteria with intact and active DNA-sequence in samples of permafrost.

The scenario of a still living pathogen or parasite inside a frozen and preserved body of an ice age mammal is also the main storyline of a TV-horror-production of 2009, named appropriately "The Thaw" (strangely the title for the German release is the exact opposite - "Frozen"). In a remote region of the Canadian tundra a carcass of mammoth (Mammuthus primigenius?) is discovered in a melting glacier. 
(P.S. prehistoric monsters entrapped in ice have a long tradition - see for example "The Beast from 20,000 Fathoms" in 1953, "Godzilla" in 1954 and "Dinosaurus!" in 1960)

This is a common misconception, the natural mummies discovered until now were preserved all in permafrost soil, which contains local ice lenses of secondary genesis. This ice maybe plays an important role in the desiccation and preservation of the carcass, as moisture migrates from the body to the ice.
Anyway - the warming of the Canadian Arctic due anthropogenic climate change not only releases dead mammoths from the melting underground, but also a deadly and living pathogen - a parasite in from of an arthropod (a - bug - as noobs call it) that needs body heat. To survive inside its host the parasite weakens the immune system (as some real parasites do) - this behaviour would finally cause the death of the host, if the flesh-eating bugs (arthropods) didn't also multiply so fast that they eat their victim from inside.

The movie uses a environmental cause (the disease is released due the warming of the planet caused by our actions) as premise, most of it is however clearly inspired (or copied) from the movie "The Thing" (1982), even if there the parasite - first hiding and then exactly copying its host-  is an alien lifeform.




The Thaw doesn't really explain the origin of the parasite, but it seems almost certain that it is of terrestrial origin and also so deadly that it caused the extinction of the entire Pleistocene megafauna. The idea of an unidentified hyperdisease killing animals was proposed in 1997 after the first epidemics of Ebola in 1976-1979 and 1994-1996. Main vector of the presumed pathogen was Homo sapiens, infecting mammoths and other large mammals during his travels around Siberia and North America. In 2006 a research on the pathological malformations of bones from American Mastodon (Mammut americanum) and bison bones suggested that the animals suffered from an infection of tuberculosis. A relatively large number of geographically and temporal separated individuals showed those malformations.
A recent example how dangerous pathogens can be for an isolated population was observed on the Christmas Islands in the Indian Ocean. In 1899 human colonization and introduced black rats (Rattus rattus) brought a unicellular parasitic protist (Trypanosoma) onto the islands. The endemic rat species (Rattus macleari) was not immune against the introduced parasite and the population suffered a rapid decline - in 1904 the species was considered extinct. However this is an example on a very confined space, involving a single species - it remains unclear how a single pathogen could wipe out so many species in such a short time on almost the entire planet.

Last but not least: a strange movie combines somehow The Thing with mammoths. In the TV-horror "Mammoth" (2006) an alien lifeform assimilates a partially frozen woolly mammoth exposed in a museum. The mammoth-alien-zombie goes on a rampage - killing people by adsorbing their life energy... until stopped by the Men in Black...



Bibliography:

JOHNSON, S.S. et al. (2007): Ancient bacteria show evidence of DNA repair. PNAS Vol. 104 (36): 14401-14405
ROTHSCHILD, B.M. & LAUB, R. (2006): Hyperdisease in the late Pleistocene: validation of an early 20th century hypothesis. Naturwissenschaften 93:557-564
WYATT, K.B.; CAMPOS, P.F.; GILBERT, M.T.P.; KOLOKOTRONIS, S.-O.; HYNES, W.H., et al. (2008): Historical Mammal Extinction on Christmas Island (Indian Ocean) Correlates with Introduced Infectious Disease. PLoS ONE 3(11): 1-9

The discovery of the periglacial realm

The term periglacial was introduced by the Polish geologist Walery von Lozinsk in 1910 and 1911 to describe the particular mechanical weathering he had observed in sandstones of the Gorgany Range in the southern Carpathian Mountains - today the reactions of the permafrost to changing temperatures is one of the major fields of research. Read more about the periglacial realm on the American Scientific Blog.

The Younger Dryas impact hypothesis

The cause(s) that led to the extinction of most of the larger mammals that roamed the Pleistocene world are still today unknown. Many different hypotheses were proposed, from human overkill to climate change, but more unusual was an idea largely publicized in 2007.

Geophysical studies presented in spring 2007 suggested that perhaps an extraterrestrial bolide vaporized in the Earth's atmosphere caused the extinction of the North American Megafauna some 13.000 years ago.
In 2009 this hypothesis seemed to be further confirmed by subsequent findings. This and other interdisciplinary research presented various sedimentological features found in peat layers at nine excavated sites of the North American continent and one site in Belgium and thought to be associated with impacts of meteorites on earth.

Fig.1. Profiles of sites in North America with proposed sedimentological evidences for an impact event some 12.900 years ago. The diagrams show the concentration of magnetic particles, microspheres, particles of coal and glass and some elements rare in the earth's crust but common in meteorites (such as iridium, chromium and nickel). The highest values are apparently found in a distinct single thin layer, after FIRESTONE et al. 2007.

1) An increased concentration of iridium, a rare element in earth's crust but common in meteorites.

2) Metallic particles and grains, also carbon microspheres concentrated in a thin layer, interpreted as remains of the impacted meteorite and the recrystallized molten rocks of the bolide and crust.

Fig.2. and 3. The metallic micrometeorites with a diameter between 100 to 150 µm found in one of the profiles (Blackwater Draw) showed a high content of titanium and nickel typical for extraterrestrial material (FIRESTONE et al. 2007), also shown the carbon microspheres interpretated as the remains of the molten and recrystallized bolide.

3) A particular and rare modification of carbon - Lonsdaleite - in shape of microscopic nanodiamonds with a hexagonal crystalline structure formed only under very high pressure as experienced during an impact.

4) Another exotic modification of carbon, the Buckminsterfullerene or buckyballs, a modification of carbon that supposedly can be created only under great heat conditions.

5) Dark layers of peat or sediments rich in organic matter were interpreted as the remains of burned vegetation by megafires ignited by the heat of the impact.

6) Recovered Pleistocene bones of mammoth and bison showed features that were interpreted as direct effects of the explosion - small, 2 to 3 mm in diameter, holes in the bones with a burned halo and penetrated magnetic particles with a high content of iron and nickel of unusual isotopic composition.

To explain the lack of the most compelling evidence - the impact crater- it was suggested that the bolide exploded above or on the Laurentide ice shield, leaving behind no visible trace.
7) An alternative suggestion positioned a debris field in the Carolina Bay area along the south-eastern coast of the United States. The Carolina Bays include thousands of circular to elliptical depressions across the coastal plain of still unknown origin (some authors suggested even spawning fish).

The most intriguing conclusion of the Younger Dryas impact hypothesis: The heat released and the shock waves of the impact caused the extinction of the North American Megafauna and the annihilation of the Clovis-culture possibly in two ways, by directly killing animals and igniting large scale firestorms and in a second moment by the partial melting of the ice shield of North America and Greenland. The large amounts of fresh water released in the Atlantic Ocean caused an arrestment or a slowdown of the warm Gulf Stream, starting a 1.500 years long climatic reversal recognized especially in Europe as Younger Dryas stadial (12.900-11.600 cal BP), an important phase of cooling recognized in glacier advances and vegetation shift.

Fig.4. The isotopic values as proxy of climate recovered in ice cores from Greenland show a distinct phase of climatic reversal between 12.900 and 11.600 years ago. The sudden beginning of this period named Younger Dryas stadial is still poorly understand, the influence of changing patterns of the marine currents in the Atlantic at the end of the Pleistocene are the most suggested and likely triggers of such an abrupt climate change (Greenland Ice Core Chronology 2005 released 10. March 2006).

The hypothesis experienced a positive and large attention in the popular media but got mixed reception from earth scientists during it´s official presentation in May 2007 at the congress of the American Geophysical Union.
The meteorite idea was however not completely new and already published in 2001 and in 2006 even in a own book - however with some pseudoscientific implications like glacial landscapes with drumlins or the North American Great Lakes as the direct results of the impact.

Also focusing only on the research published in 2007 soon problems arouse. For example the methods used to identify some of the most compelling impact evidence, like the nanodiamonds, were questioned because the results of the analyses were explainable also by other, more earthly, materials.
More important - the impact hypothesis could only explain a local decline and extinction event for the American continent in a very short interval, maybe in few decades or centuries. However dated fossils seem not to support a unique and sudden extinction as proposed by this and many other catastrophist hypotheses. In a survey on 4.532 archaeological sites in Europe and Siberia and 1.177 dated remains of mammoth and mastodons in Europe, Siberia and North America the dates scatter between 45.000 to 12.000 years.
Estimating the development of the population of single species there seems to be various phases of increase and decline in numbers of individuals. The woolly mammoth for example reaches a population maximum some 16.000 to 15.500 years ago, this phase is followed by a slow decline 14.500 to 13.500 years ago, however isolated populations survived on islands and in northern regions of Asia even until historic times.

Apart of these general critics in 2011 a paper By PINTER et al. focused explicit on the single evidences as presented in 2007 and subsequent years and concluded that most of the claims can not be reproduced and the few reproduced evidences are not unequivocally related to an impact of an extraterrestrial bolide:

1) The iridium concentration was not measured in the bulk sediment but on single fragments or spherules thought to be of impact origin - this could falsify the apparent peak in the stratigraphic column. On some studied sites the concentration of iridium in the supposed Dryas interval was also surprisingly low. Despite the methodological error, these contradicting results are imputable to diagenetic alteration of the sediments and the iridium concentration is more likely of terrestrial origin.
More notable subsequent research failed to reproduce the single iridium peak.

2) Some of the carbon spherules resulted to be fungal spores or coprolites of arthropods. Subsequent research could not reproduce a peak or concentration of micrometeorites in a single layer, but the particles resulted to be distributed homogenous in the stratigraphic column, as more likely explained by the common background sedimentation from the interplanetary space occurring during geological times.

3) The supposed nanodiamonds resulted by further and more detailed investigations to be amorphous to polycrystalline carbon aggregates as produced during common wildfires, the presence of the particular carbon modification Lonsdaleite could not unequivocally proven in the sediments.

4) The presence of buckyballs was questioned because of methodological problems already in the original research and later investigations could not reproduce the results. Despite the dubious presence of the fullerenes, it is known that small amounts of this carbon modification can be produced by common wildfires, so even if buckyballs will be found, these are not unequivocally evidence of an impact.

5) Sediments rich of organic matter are not necessary produced by wildfires; common depositional environments like swamps can also produce thick layers with encoaled plant remains. Some proposed impact-related dark layers, supposedly rich of organic matter, resulted even to be coloured not by organic remains but by minerals. There is today no unequivocally evidence that the layers are connected to any wildfires after an impact.

6) Some of the bones with the supposed fragments of the bolide resulted to be older by nearly 20.000 years than the previously specified impact date. The fragments in the bones were not reanalyzed after the first claims and doubts arouse of the proposed origin.
It seems unlikely that such minuscule and fragile particles could penetrate earth's atmosphere and still impact on such a hard material as are the bones. In alternative it is well possible that the discovered particles are more likely diagenetic iron concentrations.

7) The explanation of the Carolina Bays as debris field is not supported by any discovery of extraterrestrial material in the area; also relative dating efforts showed that these depressions were formed probably during a long time interval. So if these features still remain mysterious an impact origin seems the most unlikely cause of origin.
Even radiocarbon ages achieved by the impact supporters showed significant fluctuations in the ages of formation, ranging from 6.500 to 700 years ago. This lead to the excuse that "the impacting object was ejected by a recent near-Earth supernova in which case carbon [was] enriched" modifying the radiocarbon age of the sediments.
Realizing the improbability and problems of such claims the Carolina Bays were rejected as evidence by most impact proponents.

The Younger Dryas Impact Hypothesis was adopted mainly by non earth-sciences related researchers and especially the mass media, who dedicated to the scenario even various TV-shows. Even if it was stated that some of the results were preliminary, it is still surprising how catastrophic theories are accepted uncritically by popular media.
However three years later it seems that most of the proposed evidence for the Younger Dryas Impact Hypothesis could not be reproduced by other teams and were evidence is available there are terrestrial, non impact related, interpretations possible.

Bibliography:

BECKER (2007): Abstract: The End Pleistocene Extinction Event - What Caused It? Eos Trans. AGU, Abstract PP41A-03
BECKER (2007): Ice Age Impact. mp3 (4MB). (Interview by the Canadian Broadcast)
FIRESTONE, R.B.; WEST, A.; KENNETT, J.P.; BECKER, L.; BUNCH, T.E. et al. (2007): Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling. Proceedings of the National Academy of Sciences of the United States of America 104(41): 16016-16021
KENNETT, D.J.; KENNETT, J.P.; WEST, A.; WEST, G.J.; BUNCH, T.E. et al . (2009): Shock-synthesized hexagonal diamonds in Younger Dryas boundary sediments. Proceedings of the National Academy of Sciences of the United States of America 106: 12623-12638
KERR, R.A. (2007): Mammoth-Killer Impact Gets Mixed Reception From Earth Scientists. Science 316: 1264-1265
KERR, R.A. (2008): PLANETARY IMPACTS: Did the Mammoth Slayer Leave a Diamond Calling Card? Science Vol.323 : 26
LEVY, S. (2006): Clashing with Titans. BioScience Vol. 56(4) : 292-298
PINTER, N.; SCOTT, A.C.; DAULTON, T.L.; PODOLL, A.; KOEBERL, C.; ANDERSON, R.S.; ISHMAN, S.E. (2011): The Younger Dryas impact hypothesis: A requiem. Earth Science Reviews. Article in Press
UGAN, A. & BYERS, D. (2007): Geographic and temporal trends in proboscidean and human radiocarbon histories during the late Pleistocene. Quaternary Science Reviews.26: 3017-3440

Online Resources:

MORRISON, D. (2010): Did a Cosmic Impact Kill the Mammoths? (Accessed on 23.04.2011)

15 April, 1912: The Iceberg That Sank the Titanic

In the night of April 14, 1912 the passenger liner "R.M.S. Titanic" collided with an iceberg, two hours later (2:20, April 15)  the ship sank, estimated 1490 to 1517 passengers died in the cold water of the Atlantic.

The story of the ship became part of history and pop culture, but the story of the iceberg that caused the disaster is less understand or known and only vague descriptions and some photos exists of the supposed iceberg(s).

Fig.1. The moment of the collision according to the sailor Frederick Fleet - one of the two men on duty as lookout in the night of April 14 (after EATON & HAAS 1986).

Fig.2. One of the many icebergs suspected of having sank the Titanic photographed in the morning of April 15, from board of the ship "Prinz Adalbert". The eyewitnesses still unaware of the disaster of the previous night reported a "red smear" at the waterline of the white giant still visible and therefore supposedly less than 12 hours old. The (contradicting) dimension of the iceberg given were 30 meter height and 100 meter width (photo from Wikipedia).

Fig.3. Another iceberg photographed April 20, from the German steamer "Bremen" claimed to be the Titanic iceberg based on the vicinity to the location of the disaster and the description of the iceberg according to eyewitnesses reports of Titanic survivors (photo from Wikipedia).

Fig.4. Photography of an iceberg from the cable ship "Minia", one of the first ships to reach the area in search for debris and bodies. The crew found debris and bodies floating in the vicinity of the depicted iceberg and the captain assured that this was the only iceberg near the scene of the collision (after Titanic & Nautical Resource Center).
 Fig.5. Journalist Colin Campbell, a passenger of the "Carpathia" - the first ship to approach the scene of the disaster and save the surviving passengers of the Titanic - described the iceberg for the New York Tribune (after EATON & HAAS 1986).

Fig.6. Photography from the ship "Birma" of the same iceberg as described by Campbell. This iceberg has some remarkable similarities to the iceberg as described and drawn by survivors of the Titanic (see the first figure with the drawing by Fleet).
Despite the question if one of the photos shows the culprit iceberg, the remarkably number of spotted icebergs emphasizes the notion that in 1912 an exceptional number of these white giants reached such southern latitudes (after EATON & HAAS 1986).

The icebergs from the North Atlantic originate mainly from the western coasts of Greenland, where ice streams deliver large quantities of ice in the fjord-systems which leads to the Baffin sea. Still today this region is the most important origin of icebergs on the northern hemisphere, thousands of junks of ice per year drop from the front of the glaciers and if large enough will one or three years later reach the North Atlantic.

Ironically it was in 1909, three years before the disaster, that the construction works for the Titanic begun in the dockyard of Harland & Wolff Ltd. in Belfast (Ireland).

When the large iceberg reached the cold open sea of the Baffin Bay the West Greenland Current pushed it first slowly to northern realms following the coast of Greenland, then along the Canadian coast the voyage to the south begun.
Finally offshore of Newfoundland the iceberg was captured by the "warm", but fast Gulf Stream and pushed in south-western direction. Only one percent of all icebergs reach such southern latitudes, in 1912 however icebergs were spotted remarkably often in this area, maybe as a result of previous mild winters and strong activity of the calving glaciers (discussed also in this post on "The Science behind the Iceberg that sank the Titanic").

 Fig.7. Schematic diagram of marine currents (blue= cold; red = hot) around Greenland and the hypothetical region of origin (West Greenland) and route of the iceberg that collided with the Titanic.

The construction of the Titanic proceeded with astonishing rate; the ship was launched to the sea on May 31, 1911 and her outfitting was completed by March 31,  1912.
The ship began its maiden voyage from Southampton, and after a stop in the French Cherbourg and the Irish Queenstown, it set out the final route for New York City on April 10, 1912.

Four days later the Titanic encountered the anonymous iceberg. In the following days bypassing ships at the site of the disaster encountered and photographed various icebergs, some eyewitnesses claim to have spotted red paint on some of them, however there is no conclusive evidence that the culprit iceberg was spotted - and there will never be - at least two to three weeks later the iceberg that sank the Titanic would be melted and disappeared forever into the Atlantic Ocean.

Bibliography:

EATON, J.P. & HAAS, C.A. (1986): Titanic Triumph and Tragedy. Haynes Publishing: 352 
SOUTH, C. (2006): The Iceberg That Sank the Titanic. The Natural World documentary film – BBC

Blue Marble: 22.000 years of changing earth

"Within a few millennia our ice may be gone, but if we shall have paid a fearful price for its going. Ice at its maximum extent is disastrous, but no ice is worse. The best stage is the halfway one, where we are this blessed moment, but like others it too unstable and will not stay put. We know where we are and which way we are going, but which way we shall be going a little later we do not know."
William Jackson Humphreys (1862-1949), meteorological Physicist.

The project Blue Marble 3000 is a simulation by Adrian Meyer and Karl Rege from the Zurich University of Applied Sciences of the environment changes experienced by earth from the last Ice Age some 21.000 years ago in the past to the Anthropocene some 1.000 years in the future. The simulation is based mostly on freely accessible data of temperature, vegetation, satellite photos and topography:

10.000 to 8.000 years ago the melting ice caps frees huge amounts of water and a dramatic rise of the global sea level follows, in Europe the northern plains of the Mammoth tundra became inundated and the British islands are separated from the European mainland.
6.000 years ago nearly all of the continents of Europe and North America became free of the ice.
By changing atmospheric current patterns more moisture arrives to North Africa, the Sahara is a vast savannah with periodic large lakes until 4.000 years ago, then again a shift in the currents transform this rich environment in one of the largest deserts on earth today.
These environments remains stable for nearly further 4.000 years, then an acceleration of the retreat of the ice caps is visible. The temporal scale changes now from 500 years steps to 50 years steps to emphasize a new epoch - the Anthropocene has begun.