Chasing the 'Black Holes' of the Ocean

According to researchers from ETH Zurich and the University of Miami, some of the largest ocean eddies on Earth are mathematically equivalent to the mysterious black holes of space. These eddies are so tightly shielded by circular water paths that nothing caught up in them escapes.

The mild winters experienced in Northern Europe are thanks to the Gulf Stream, which makes up part of those ocean currents spanning the globe that impact on the climate. However, our climate is also influenced by huge eddies of over 150 kilometres in diameter that rotate and drift across the ocean. Their number is reportedly on the rise in the Southern Ocean, increasing the northward transport of warm and salty water. Intriguingly, this could moderate the negative impact of melting sea ice in a warming climate.

However, scientists have been unable to quantify this impact so far, because the exact boundaries of these swirling water bodies have remained undetectable. George Haller, Professor of Nonlinear Dynamics at ETH Zurich, and Francisco Beron-Vera, Research Professor of Oceanography at the University of Miami, have now come up with a solution to this problem. In a paper just published in the Journal of Fluid Mechanics, they develop a new mathematical technique to find water-transporting eddies with coherent boundaries.

The challenge in finding such eddies is to pinpoint coherent water islands in a turbulent ocean. The rotating and drifting fluid motion appears chaotic to the observer both inside and outside an eddy. Haller and Beron-Vera were able to restore order in this chaos by isolating coherent water islands from a sequence of satellite observations. To their surprise, such coherent eddies turned out to be mathematically equivalent to black holes.

No escape from the vortex

Black holes are objects in space with a mass so great that they attract everything that comes within a certain distance of them. Nothing that comes too close can escape, not even light. But at a critical distance, a light beam no longer spirals into the black hole. Rather, it dramatically bends and comes back to its original position, forming a circular orbit. A barrier surface formed by closed light orbits is called a photon sphere in Einstein's theory of relativity.

Haller and Beron-Vera discovered similar closed barriers around select ocean eddies. In these barriers, fluid particles move around in closed loops -- similar to the path of light in a photon sphere. And as in a black hole, nothing can escape from the inside of these loops, not even water.

It is precisely these barriers that help to identify coherent ocean eddies in the vast amount of observational data available. According to Haller, the very fact that such coherent water orbits exist amidst complex ocean currents is surprising.

 

Eddies as water taxis

Because black-hole-type ocean eddies are stable, they function in the same way as a transportation vehicle -- not only for micro-organisms such as plankton or foreign bodies like plastic waste or oil, but also for water with a heat and salt content that can differ from the surrounding water. Haller and Beron-Vera have verified this observation for the Agulhas Rings, a group of ocean eddies that emerge regularly in the Southern Ocean off the southern tip of Africa and transport warm, salty water northwest. The researchers identified seven Agulhas Rings of the black-hole type, which transported the same body of water without leaking for almost a year.

Haller points out that similar coherent vortices exist in other complex flows outside of the ocean. In this sense, many whirlwinds are likely to be similar to black holes as well. Even the Great Red Spot -- a stationary storm -- on the planet Jupiter could just be the most spectacular example of a black-hole type vortex . "Mathematicians have been trying to understand such peculiarly coherent vortices in turbulent flows for a very long time," explains Haller.

Notably, the first person to describe ocean eddies as coherent water islands may well have been the American writer, Edgar Allan Poe. In his story "A Descent into the Maelstrom," he envisioned a stable belt of foam around a maelstrom. This served as inspiration for Haller and Beron-Vera, who went on to find these belts -- the oceanic equivalent to photon spheres -- using sophisticated mathematical formulas. Their results are expected to help in resolving a number of oceanic puzzles, ranging from climate-related questions to the spread of environmental pollution patterns.

Eddy in the Gulf of Mexico

Just after the publication of Haller's and Beron-Vera's results, Josefina Olascoaga, also a Professor of Oceanography in Miami, tested their new mathematical method. She unexpectedly found a large, black-hole type eddy in the Gulf of Mexico.  Olascoaga now uses her finding to assess the coherent transport of contamination from a possible future oil spill.

 Source:Science Daily

R.S

Controlling Wettability: 'Sticky Tape' for Water Droplets Mimics Rose Petal

A new nanostructured material with applications that could include reducing condensation in airplane cabins and enabling certain medical tests without the need for high tech laboratories has been developed by researchers at the University of Sydney.

"The newly discovered material uses raspberry particles -- so-called because of their appearance -- which can trap tiny water droplets and prevent them from rolling off surfaces, even when that surface is turned upside down," said Dr Andrew Telford from the University's School of Chemistry and lead author of the research recently published in the journal, Chemistry of Materials.

The ability to immobilise very small droplets on a surface is, according to Dr Telford, a significant achievement with innumerable potential applications.

Raspberry particles mimic the surface structure of some rose petals.

"Water droplets bead up in a spherical shape on top of rose petals," Dr Telford said. "This is a sign the flower is highly water repellent."

The reasons for this are complex and largely due to the special structure of the rose petal's surface. The research team replicated the rose petal by assembling raspberry particles in the lab using spherical micro- and nanoparticles.

The result is that water droplets bead up when placed on films of the raspberry particles and they're not able to drip down from it, even when turned upside down.

"Raspberry particle films can be described as sticky tape for water droplets," Dr Telford said.

This could be useful in preventing condensation issues in airplane cabins. It could also help rapidly process simple medical tests on free-standing droplets, with the potential for very high turnover of tests with inexpensive equipment and in remote areas.

Other exciting applications are under study: if we use this nanotechnology to control how a surface is structured we can influence how it will interact with water.

"This means we will be able to design a surface that does whatever you need it to do.

"We could also design a surface that stays dry forever, never needs cleaning or able to repel bacteria or even prevent mould and fungi growth.

"We could then tweak the same structure by changing its composition so it forces water to spread very quickly.

"This could be used on quick-dry walls and roofs which would also help to cool down houses. 

"This can only be achieved with a very clear understanding of the science behind the chemical properties and construction of the surface," he said.

Source:Science Daily

Sh/Kh

Dating of Beads Sets New Timeline for Early Humans

An international team of researchers led by Oxford University have new dating evidence indicating when the earliest fully modern humans arrived in the Near East, the region known as the Middle East today. They have obtained the radiocarbon dates of marine shell beads found at Ksar Akil, a key archaeological site in Lebanon, which allowed them to calculate that the oldest human fossil from the same sequence of archaeological layers is 42,400-41,700 years old. This is significant because the age of the earliest fossils, directly and indirectly dated, of modern humans found in Europe is roughly similar. This latest discovery throws up intriguing new possibilities about the routes taken by the earliest modern humans out of Africa, says the study published online by the journal PLOS ONE.

The research team radiocarbon dated 20 marine shells from the top 15 metres of archaeological layers at Ksar Akil, north of Beirut. The shells were perforated, which indicates they were used as beads for body or clothes decoration by modern humans. Neanderthals, who were living in the same region before them, were not making such beads. The study confirms that the shell beads are only linked to the parts of the sequence assigned to modern humans and shows that through direct radiocarbon dating they are between 41,000-35,000 years old.

The Middle East has always been regarded as a key region in prehistory for scholars speculating on the routes taken by early humans out of Africa because it lies at the crossroads of three continents -- Africa, Asia and Europe. It was widely believed that at some point after 45,000 years ago early modern humans arrived in Europe, taking routes out of Africa through the Near East, and, from there, along the Mediterranean rim or along the River Danube. However, this dating evidence suggests populations of early modern humans arrived in Europe and the Near East at roughly the same time, sparking a new debate about where the first populations of early humans travelled from in their expansion towards Europe and which alternative routes they may have taken.

In Ksar Akil, the Lebanese rockshelter, several human remains were found in the original excavations made 75 years ago. Unfortunately since then, the most complete skeleton of a young girl, thought to be about 7-9 years of age buried at the back of the rock shelter, has been lost. Lost also are the fragments of a second individual, found next to the buried girl. However, the team was able to calculate the age of the lost fossil at 40,800-39,200 years ago, taking into account its location in the sequence of archaeological layers in relation to the marine shell beads.

Another fossil of a recently rediscovered fragment of the upper jaw of a woman, now located in a museum in Beirut, had insufficient collagen to be dated by radiocarbon methods. A method using statistical modelling was used to date by association the jaw fragment at 42,400-41,700 years old. 

Ksar Akil is one of the most important Palaeolithic sites in Eurasia. It consists of a 23 metre deep sequence of archaeological layers that lay undisturbed for thousands of years until a team of American Jesuit priests excavated the rockshelter in 1937-38, and again after the end of the WWII, in 1947-48. The cave layers were found to contain the human fossils and hundreds of shell beads, as well as thousands of stone tools and broken bones of hunted and consumed animals.

The earliest European modern fossil, from Romania, dates to between 42,000-38,000 years before the present time, and specialists have estimated the age of Kent's Cavern maxilla from southern England, between 44,000-41,000 years, and that of two milk teeth in southern Italy, at 45,000-43,000 years old. The new dating evidence from Ksar Akil is largely comparable to these ages, if not slightly younger.

The work was led by Dr Katerina Douka of Oxford University, along with Professor Robert Hedges and Professor Tom Higham (Oxford); American Palaeolithic archaeologist Dr Christopher Bergman from URS Corporation, Cincinnati; and Frank P Wesselingh from the Naturalis Biodiversity Center, Leiden, The Netherlands.

Source:Science Daily

R.Sawas

Water Hidden in the Moon May Have Proto-Earth Origin

Water found in ancient Moon rocks might have actually originated from the proto-Earth and even survived the Moon-forming event. Latest research into the amount of water within lunar rocks returned during the Apollo missions is being presented by Jessica Barnes at the European Planetary Science Congress in London on Monday 9th September.

The Moon, including its interior, is believed to be much wetter than was envisaged during the Apollo era. The study by Barnes and colleagues at The Open University, UK, investigated the amount of water present in the mineral apatite, a calcium phosphate mineral found in samples of the ancient lunar crust.

“These are some of the oldest rocks we have from the Moon and are much older than the oldest rocks found on Earth. The antiquity of these rocks make them the most appropriate samples for trying to understand the water content of the Moon soon after it formed about 4.5 billion years ago and for unraveling where in the Solar System that water came from,” Barnes explains.

Barnes and her colleagues have found that the ancient lunar rocks contain appreciable amounts of water locked into the crystal structure of apatite. They also measured the hydrogen isotopic signature of the water in these lunar rocks to identify the potential source(s) for the water.

“The water locked into the mineral apatite in the Moon rocks studied has an isotopic signature very similar to that of the Earth and some carbonaceous chondrite meteorites,” says Barnes. “The remarkable consistency between the hydrogen composition of lunar samples and water-reservoirs of the Earth strongly suggests that there is a common origin for water in the Earth-Moon system.”

Source : Science Daily

N.H.Khider

'World's largest volcano discovered beneath Pacific

 

 

 

Scientists say that they have discovered the single largest volcano in the world, a dead colossus deep beneath the Pacific waves.

A team writing in the journal Nature Geoscience says the 310,000 sq km (119,000 sq mi) Tamu Massif is comparable in size to Mars' vast Olympus Mons volcano - the largest in the Solar System.

The structure topples the previous largest on Earth, Mauna Loa in Hawaii.

The massif lies some 2km below the sea.

It is located on an underwater plateau known as the Shatsky Rise, about 1,600km east of Japan.

It was formed about 145 million years ago when massive lava flows erupted from the centre of the volcano to form a broad, shield-like feature.

The researchers doubted the submerged volcano's peak ever rose above sea level during its lifetime and say it is unlikely to erupt again.

"The bottom line is that we think that Tamu Massif was built in a short (geologically speaking) time of one to several million years and it has been extinct since," co-author William Sager, from the University of Houston, US, told the AFP news agency.

"One interesting angle is that there were lots of oceanic plateaus (that) erupted during the Cretaceous Period (145-65 million years ago) but we don't see them since. Scientists would like to know why."

Prof Sager began studying the structure two decades ago, but it had been unclear whether the massif was one single volcano or many - a kind that exists in dozens of locations around the planet.

While Olympus Mons on Mars has relatively shallow roots, the Tamu Massif extends some 30 km (18 miles) into the Earth's crust.

And other volcanic behemoths could be lurking among the dozen or so large oceanic plateaux around the world, he thought.

"We don't have the data to see inside them and know their structure, but it would not surprise me to find out that there are more like Tamu out there," said Dr Sager.

"Indeed, the biggest oceanic plateau is Ontong Java plateau, near the equator in the Pacific, east of the Solomon Islands. It is much bigger than Tamu - it's the size of France."

The name Tamu comes from Texas A&M University, where Prof Sager previously taught before moving to the University of Houston

Source : BBC

N.H.Khider

 

 

 

Subcategories