Soon you may see an eerie spectacle on clear summer nights if you are located at latitudes between 50° and 70° north and south of the equator: Noctilucent Clouds.
These ghostly apparitions are a delight to see and are quite rare. It is incredibly difficult to predict exactly when they will appear, but we do know they should begin to appear soon.
The season for Noctilucent Clouds (Noctilucent = Latin for “Night Shining”) starts early June and continues into late July. They are seen just after dusk, or before dawn and an apparition can last around an hour.
These mysterious clouds, with their bizarre tenuous wispy shapes reminiscent of ripples in sand or the changing surface of a pool of water, spread like a glowing web across the northern sky. Colours can range from brilliant whites, with tinges of blue, pink and orange.
Formed by tiny ice crystals, they are the highest clouds in the Earth’s atmosphere, located in the mesosphere at altitudes of around 76 to 85 kilometers (47 to 53 miles) almost at the edge of space.
They are normally too faint to be seen, and are visible only when illuminated by sunlight from below the horizon, while the lower layers of the atmosphere are in the Earth’s shadow. Noctilucent clouds are not fully understood and are a recently discovered meteorological phenomenon, only being recorded for about 120 years.
Noctilucent clouds can only form under very restrictive conditions, and their occurrence can be used as a guide to changes in the upper atmosphere. Since their relatively recent classification, the occurrence of noctilucent clouds appears to be increasing in frequency, brightness and extent.
There is evidence that the relatively recent appearance of noctilucent clouds and their gradual increase, may be linked to climate change. Another recent theory is that some of these bright displays come from particulates and water vapour in the atmosphere left over from Space Shuttle launches.
How can you see them? Over the next couple of months look north during dusk and dawn and try and spot this mysterious and elusive phenomenon. They are best seen when the sun is between 6 and 16 degrees below the horizon, and seem to occur more frequently in the Northern hemisphere than the Southern.
Good luck!
Noctilucent clouds over Blair, Nebraska, USA. Credit: Mike Hollingshead
Mercury Astronaut Scott Carpenter speaks in tribute to Alan B. Shepard, first American in Space. Carpenter spoke at the First-Day-of-Issue Stamp dedication ceremony at NASA’s Kennedy Space Center on May 4, 2011. Credit: Ken Kremer
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KENNEDY SPACE CENTER – 50 Years ago this week, Alan B. Shepard became the first American to be launched into space. Shepard blasted off on May 5, 1961 from Cape Canaveral, Florida. NASA and the US Postal Service honored Shepard’s historic achievement today (May 4) at an Official First-Day-of-Issue dedication ceremony at NASA’s Kennedy Space Center in Florida.
Alan Shepard was one of the seven Project Mercury astronauts – who will be collectively known for all eternity as – “The Original 7”.
The US Postal Service simultaneously released two new 44 cent Forever Stamps at today’s commemoration, which bookend two historic space achievements – Shepard’s inaugural manned spaceflight aboard the Mercury capsule and NASA’s unmanned MESSENGER mission which recently became the first probe from Earth to achieve orbit about the Planet Mercury.
Alan Shepard and MESSENGER First-Day-of-Issue Stamp dedication ceremony at NASA’s Kennedy Space Center on May 4, 2011. Alan Shepard is the only American astronaut to be honored with his image on a US postal stamp. Credit: Ken Kremer
Fellow Mercury Astronaut Scott Carpenter attended the ceremony and unveiled the stamps along with Steve Masse, United States Postal Service Vice President of Finance at the Rocket Garden at the KSC Visitor Complex.
Mercury Astronaut Scott Carpenter poses in front of a Mercury Atlas rocket at the Rocket Garden at KSC. Carpenter was propelled to space by the Atlas rocket as the 2nd American to orbit the Earth on May 24, 1962. Credit: Ken Kremer
“Today we celebrate the 50th anniversary of many, many important issues, among them is the first steps from the home planet that were taken by the family of man,” said Carpenter.
Although Shepards suborbital flight aboard the one man “Freedom 7” Mercury capsule lasted barely 15½ minutes, the flight ignited America’s Moon landing effort and propelled American Astronaut Neil Armstrong to become the first human to set foot on the moon on July 20, 1969 during the Apollo 11 mission – one of the crowning technological achievements of the 20th Century.
The success of “Freedom 7” emboldened President John F. Kennedy to declare that America “should commit itself to achieving the goal, before this decade is out, of landing a man on the moon and returning him safely to the Earth,” just three weeks later on May 20.
“That was largely a response to Alan’s success,” Carpenter told the crowd of assembled officials, journalists and visitors. Also on hand for the stamp dedication was Shepard’s daughter Laura Shepard Churchly; Charles Bolden, NASA Administrator and former shuttle astronaut; Bob Cabana, KSC Director and former shuttle astronaut; and Jim Adams, NASA deputy director, Planetary Science.
“A decision was made not to put 44 cents on the stamp, but it is forever,” Carpenter emphasized. “It is appropriate to the time we should honor and remember Alan B Shepard and Freedom 7.”
Alan Shepard display at the Kennedy Space Center Visitor Complex. Credit: Ken Kremer
Shepard’s tiny capsule measured just six feet by six feet, reached a maximum speed of 5,100 MPH, roughly eight times the speed of sound, and a zenith of 116 miles above the Earth. Freedom 7 was bolted atop a Redstone rocket that generated only 78,000 pounds of thrust, followed a ballistic arc and landed 300 miles down range in the ocean.
“These stamps, which will go out by the millions across this country, are a testament to the thousands of NASA men and women who shared dreams of human spaceflight and enlarging our knowledge of the universe,” said Bolden.
Shepard’s flight and MESSENGER both blasted off from launch pads quite close to one another at Cape Canaveral Air Force Station which is adjacent to the Kennedy Space Center.
Mercury Astronaut Scott Carpenter is applauded at tribute to Alan B. Shepard, first American in Space ceremony at the Rocket Garden at KSC on May 4, 2011. Credit: Ken Kremer
On Thursday May 5, watch for my on site coverage of NASA’s special ceremony marking the 50th Anniversary of Shepard’s milestone “Freedom 7” mission – and an interview with Scott Carpenter.
Shepard’s mission came barely three weeks after Cosmonaut Yuri Gagarin became the first human to orbit the Earth. The bold flights of these brave Cosmonauts and Astronauts – backed by a few insightful political leaders – began the Era of Human Spaceflight. As the shuttle program winds to a close, the future of US Human Spaceflight is very uncertain.
Read my related articles about Yuri Gagarin and the 50th Anniversary of Human Spaceflight:
Australia and Asia region of Earth's geoid. Credits: ESA/HPF/DLR, anaglyph by Nathanial Burton-Bradford.
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Grab your red/cyan 3-D glasses and take a look at these marvelous new anaglyphs created by Nathanial Burton-Bradford from the latest data from GOCE satellite, showing Earth’s gravity field – or geoid. The geoid is essentially a map of the shape our world would be its surface were covered by water and if gravity were the only thing shaping this global ocean’s surface. These exaggerated views (the surface in the images of the geoid is amplified by a factor 7,000) show the most accurate model of how gravity varies across the planet. Nathanial was able to obtain high-resolution video from Dr. Rune Floberghagen of the GOCE team from which he extracted appropriate frames in order to construct hi-res anaglyph images of numerous longitudes across the globe.
In our previous article about GOCE (Gravity Field and Steady-State Ocean Circulation Explorer), we showed the entire globe and how it looks like a spinning potato. Nathanial’s anaglyphs show close-ups of various parts of the globe. Above is Australia and Asia. Take a trip around the GOCE geoid 3-D world below. Remember, use the red/cyan 3-D glasses to get the full effect!
GOCE view of South America. Credits: ESA/HPF/DLR, anaglyph by Nathanial Burton-Bradford.
GOCE view of the US and Mexico. Credits: ESA/HPF/DLR, anaglyph by Nathanial Burton-Bradford.GOCE view of Europe. Credits: ESA/HPF/DLR, anaglyph by Nathanial Burton-Bradford.GOCE view of Africa.. Credits: ESA/HPF/DLR, anaglyph by Nathanial Burton-Bradford.GOCE global view, 145 East Longitude. Credits: ESA/HPF/DLR, anaglyph by Nathanial Burton-Bradford.GOCE global view, 140 West Longitude. Credits: ESA/HPF/DLR, anaglyph by Nathanial Burton-Bradford.
The legacy of Yuri Gagarin and Vostok1 honored by Opportunity Mars Rover at Vostok Crater and Gagarin Rock. Photos: Roscosmos/NASA/JPL Poster: Ken Kremer
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50 Years ago, the dream of human spaceflight opened with the courageous blastoff of Cosmonaut Yuri Gagarin inside the Vostok 1 spacecraft on April 12, 1961. Gagarin was the first person to orbit the Earth. Less than a month later on May 5. 1961, Astronaut Alan Shepard bravely set forth on America’s first human spaceflight – Freedom 7.
Barely three weeks afterward on May 25, 1961, these momentous events of the early Space Age led directly to Project Apollo and the historic announcement by President Kennedy that the United States “would land a man on the moon” by the end of the 1960’s.
In honor of Yuri Gagarin, NASA’s Opportunity Mars Rover explored a small and highly eroded crater dubbed “Vostok Crater” in 2005 during its journey in the Meridian Planum region on the Martian surface. Along the edge of the crater, researchers commanded Opportunity to use the Rock Abrasion Tool (RAT), to drill into a rock dubbed “Gagarin” on Sols 401 and 402 in March 2005.
Opportunity landed on Mars on Jan. 24, 2004 for a planned 90 sol mission. By the time that Opportunity arrived at Vostok Crater, she had already lasted more than 4 times longer than expected and found that water existed on ancient Mars.
Opportunity is still alive today on Sol 2571, more than 28 times beyond its design lifetime !
Opportunity used its rock abrasion tool (RAT) on a rock named "Gagarin" during Sols 401 and 402 on Mars (March 10 and 11, 2005). This false-color image shows the circular mark created where the tool exposed the interior of the rock Gagarin at a target called "Yuri." The circle is about 4.5 centimeters (1.8 inches) in diameter. Gagarin is at the edge of a highly eroded, small crater that was named "Vostok" for the spacecraft that carried Cosmonaut Yuri Gagarin in the first human spaceflight, on April 12, 1961. This image combines exposures taken through three different filters by Opportunity's panoramic camera on Sol 405 (March 14, 2005). Credit: NASA/JPL-Caltech/Cornell Univ./ASU
Scientists are using the data gathered from “Gagarin Rock” and other locations explored by Opportunity to help elucidate the history of the past flow of liquid water on the red planet and determine whether the wet environmental conditions could ever have supported martian microbial life – past or present.
“The 50th anniversary of mankind’s first fledgling foray into the cosmos should serve as an important reminder of the spirit of adventure and exploration that has propelled mankind throughout history,” said Mars rover science team member James Rice of NASA Goddard Space Flight Center, Greenbelt, Md, in a statement. “We are a species of explorers; it is encoded into our very DNA.”
“Half a century ago Yuri Gagarin was lofted into a totally unknown, remote and hostile environment and in doing so opened up a new limitless frontier of possibilities for mankind,” Rice added. “A mere 23 days later another brave human, Alan Shepard, climbed aboard a rocket and ventured into the starry abyss. Their courage and vision continue to inspire and lead us into the unknown. Hopefully, one day in the not too distant future it will lead humanity on a voyage to Mars.”
Many people, including myself, were inspired by the Space Race to become scientists and engineers and hope that continues for the next generation of students today.
Read more about Yuri Gagarin and Opportunity in my related stories:
Opportunity used its rock abrasion tool on a rock named "Gagarin" during the 401st and 402nd Martian days, or sols, of the rover's work on Mars (March 10 and 11, 2005). This image, taken by Opportunity's navigation camera on Sol 405 (March 14, 2005), shows the circular mark left on the rock. The circle is about 4.5 centimeters (1.8 inches) in diameter. At the end of the rover's arm, the tool turret is positioned with the rock abrasion tool pointing upward in this image. The abrasion target on the rock Gagarin was informally named "Yuri." Credit: NASA/JPL-Caltech Opportunity Traverse Map during 7 year long journey across Mars.
Map shows the long journey of Opportunity spanning the Meridiani Planum region from landing in Jan 2004 to recent stop at Santa Maria crater. Opportunity explored Vostok Crater in March 2005, about 1 year after landing as indicted by marker in yellow. Credit: NASA/JPL/Cornell Marco Di Lorenzo, Kenneth Kremer
This set of images by the Ozone Monitoring Instrument (OMI) on NASA’s Aura satellite shows March 19, 2010 on the left, and the right shows the same date in 2011. March 2010 had relatively high ozone, while March 2011 has low levels. NASA image by Rob Simmon, with data courtesy of Ozone Hole Watch.
In the past, massive ozone loss over Antarctica has grabbed the headlines. But this year, measurements by several different sources show record levels of stratospheric ozone loss over the Arctic. Scientists say the main reason for the record ozone loss this year is that unusually cold stratospheric temperatures, which have endured later into the season than usual. Scientists say the unusual loss is not catastrophic, but something that needs to be monitored.
The World Meteorological Organization cautioned that people who live in northerly latitudes could get sunburned easier, noting that ozone-depleted air masses extended from the north pole to southern Scandinavia.
The record low temperatures were caused by unusually strong winds, known as the polar vortex, which isolated the atmospheric mass over the North Pole and prevented it from mixing with air in the mid-latitudes.
This has allowed for the formation of polar stratospheric clouds, and the catalytic chemical destruction of ozone molecules occurs on the surface of these clouds which form at 18-25 kilometers height when temperatures drop below -78 C.
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This created conditions similar to those that occur every southern hemisphere winter over the Antarctic.
Measurements by ESA’s Envisat satellite, the Ozone Monitoring Instrument (OMI) on NASA’s Aura satellite, and France’s MetOp satellite, as well as observations made since January from the ground and from balloons show all show that 40% of ozone molecules have been destroyed over the Arctic.
Ozone is a protective atmospheric layer found at around 25 km altitude that acts as a sunlight filter shielding life on Earth from harmful ultraviolet rays, which can increase the risk of skin cancer and cataracts in humans and harm marine life.
Stratospheric temperatures in the Arctic usually do vary widely from winter to winter. Last year, temperatures and ozone above the Arctic were very high. The last unusually low stratospheric temperatures over the North Pole were recorded in 1997.
“This depletion is not necessarily a big surprise,” said Paul Newman, an atmospheric scientist and ozone expert at NASA’s Goddard Space Flight Center. “The ozone layer remains vulnerable to large depletions because total stratospheric chlorine levels are still high, in spite of the regulation of ozone-depleting substances by the Montreal Protocol. Chlorine levels are declining slowly because ozone-depleting substances have extremely long lifetimes.”
Ozone “holes” do not form consistently over the North Pole like they do in Antarctica. “Last winter, we had very high lower stratospheric temperatures and ozone levels were very high; this year is just the opposite,” Newman said. “The real question is: Why is this year so dynamically quiet and cold in the stratosphere? That’s a big question with no good answer.”
Scientists will be watching in coming months for possible increases in the intensity of ultraviolet radiation (UV) in the Arctic and mid-latitudes, since ozone is Earth’s natural sunscreen. “We need to wait and see if this will actually happen,” Newman said. “It’s something to look at but it is not catastrophic.”
Scientists are also investigating why the 2011 and 1997 Arctic winters were so cold and whether these random events are statistically linked to global climate change. “In a changing climate, it is expected that on average stratospheric temperatures cool, which means more chemical ozone depletion will occur,” said Mark Weber from the University of Bremen.
Experts say that on a global scale, the ozone layer is still on a long-term course for recovery. But for decades to come, there remains a risk of major ozone losses on yearly or regional scales.
In this GOCE image, gravity is strongest in yellow areas; it is weakest in blue ones. Credit: ESA
Although they aren’t particularly fond of the comparison, scientists from the GOCE satellite team had to admit that new data showing Earth’s gravity field – or geoid — makes our planet look like a rotating potato. After just two years in orbit, ESA’s sleek and sexy GOCE satellite (Gravity Field and Steady-State Ocean Circulation Explorer) has gathered sufficient data to map Earth’s gravity with unrivalled precision. While our world certainly doesn’t look like a spinning tuber, this exaggerated view shows the most accurate model of how gravity varies across the planet.
The geoid is nothing more than how the oceans would vary if there were no other forces besides gravity acting on our planet.
“If we had an homogeneous sphere, it would be a boring sphere,” said GOCE scientist Roland Pail from Technical University in Munich, speaking at the press briefing today. “But due to rotation, you get a flattening of the Earth, and we have topography such as mountains, and irregular mass distribution in Earth’s interior. What we are showing you here, in principle, is the gravity field by any deviations due to inhomogeneous mass distributions on the Earth and the Earth’s interior.”
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While a previous gravity satellite, the Gravity Recovery And Climate Experiment (GRACE) operated for 8 years, most of the new data from GOCE was gathered in about 14 months, and provides data where there was none before.
GOCE is able to sense tiny variations in the pull of gravity over Earth, and the data is used to construct an idealized surface, which traces gravity lumps and bumps, and is the shape the oceans would take without winds, currents, Earth’s rotation and other forces.
By comparing sea level and geoid data, GOCE is revealing data on ocean currents and circulation, sea-level change, ice dynamics, said Rory Bingham, from the University of Newcastle, which helps understand heat transport and the changing climate.
But also of interest is how GOCE data reveals shifting tectonic plates in earthquakes and magma movements under volcanoes. Following the earthquakes in Japan, scientists are looking closely, as the data should reveal a three-dimensional view of what was going on inside the Earth. Even though the motion cannot be observed directly from space, earthquakes create signatures in gravity data, which could be used to understand the processes leading to these natural disasters and ultimately help to predict them.
“Even though these quakes resulted from big movements in the Earth, at the altitude of the satellite the signals are very small. But we should still seem them in the data,” said Dr. Johannes Bouman from the German Geodetic Research Institute.
GOCE in orbit. Credit: ESA
“GOCE will give us dynamic topography and circulation patterns of the oceans with unprecedented quality and resolution,” said professor Reiner Rummel, former Head of the Institute for Astronomical and Physical Geodesy at the Technische Universität München. “I am confident that these results will help improve our understanding of the dynamics of world oceans.”
“You could say that, at its early conception, GOCE was more like science fiction,” said Volker Liebig, Director of ESA’s Earth Observation Program. “GOCE has now clearly demonstrated that it is a state-of-the-art mission.”
Russia's Elektro-L spacecraft captured this view of the Moon over the Red Sea region of the Earth. Credit: NPO Lavochkin
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This stunning picture of the Moon and Earth was taken by Russia’s new Elektro-L spacecraft, a weather-forecasting satellite that launched in January 2011. This is the first major spacecraft developed in post-Soviet Russia, and it is designed to give Russian meteorologists the ability to watch the entire disk of the planet, thanks to the satellite’s position in the geostationary orbit 36,000 kilometers above the equator. The clarity of the images is fantastic, as you can see in another image of just the Earth, below. The Elektro-L is designed to last at least a decade, and will enable local and global weather forecasting, analysis of oceanic conditions, as well as space weather monitoring, such as measurements of solar radiation, properties of Earth’s ionosphere and magnetic field.
On Feb. 26, 2011, at 14:30 Moscow Time, the Elektro-L satellite produced its first breathtaking image of the home planet. Credit: NPO Lavochkin
At 8:30 PM on Saturday 26th March 2011, lights will switch off around the globe for Earth Hour and people will commit to actions that go beyond the hour. We need you…
Earth Hour started in 2007 in Sydney, Australia when 2.2 million individuals and more than 2,000 businesses turned their lights off for one hour to take a stand against climate change. Only a year later and Earth Hour had become a global sustainability movement with more than 50 million people across 35 countries/territories participating. Global landmarks such as the Sydney Harbour Bridge, CN Tower in Toronto, Golden Gate Bridge in San Francisco, and Rome’s Colosseum, all stood in darkness, as symbols of hope for a cause that grows more urgent by the hour.
In March 2009, hundreds of millions of people took part in the third Earth Hour. Over 4000 cities in 88 countries/territories officially switched off to pledge their support for the planet, making Earth Hour 2009 the world’s largest global climate change initiative.
On Saturday, March 27th, Earth Hour 2010 became the biggest Earth Hour ever. A record 128 countries and territories joined the global display of climate action. Iconic buildings and landmarks from Asia Pacific to Europe and Africa to the Americas switched off. People across the world from all walks of life turned off their lights and came together in celebration and contemplation of the one thing we all have in common – our planet.
Earth Hour 2011 will take place on Saturday 26 March at 8.30PM (local time). This Earth Hour we want you to go beyond the hour, so after the lights go back on think about what else you can do to make a difference. Together our actions add up.
“All over the world individuals, communities, businesses and governments are creating new examples for our common future – new visions for sustainable living and new technologies to realize it,” said UN Secretary General Ban Ki-moon. “Tomorrow, let us join together to celebrate this shared quest to protect the planet and ensure human well-being. Let us use 60 minutes of darkness to help the world see the light.”
Sea ice data through mid- March 2011. Credit: National Snow and Ice Data Center
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Bad news for what is now the beginning of the “melt season” in the Arctic. Right now, the sea ice extent maximum appears to be tied for the lowest ever measured by satellites as the spring begins, according to scientists at the University of Colorado Boulder’s National Snow and Ice Data Center. And because of the trend of how the amount of Arctic sea ice has been spiraling downward in the last decade, some scientists are predicting the Arctic Ocean may be ice free in the summers within the next several decades.
“I’m not surprised by the new data because we’ve seen a downward trend in winter sea ice extent for some time now,” said Walt Meier, a research scienitist with the NSIDC.
The seven lowest maximum Arctic sea ice extents measured by satellites all have occurred in the last seven years, and the from the latest data, the NSIDC research team believes the lowest annual maximum ice extent of 5,650,000 square miles occurred on March 7 of this year.
The maximum ice extent was 463,000 square miles below the 1979-2000 average, an area slightly larger than the states of Texas and California combined. The 2011 measurements were tied with those from 2006 as the lowest maximum sea ice extents measured since satellite record keeping began in 1979.
Virtually all climate scientists believe shrinking Arctic sea ice is tied to warming temperatures in the region caused by an increase in human-produced greenhouse gases being pumped into Earth’s atmosphere.
Meier said the Arctic sea ice functions like an air conditioner for the global climate system by naturally cooling air and water masses, playing a key role in ocean circulation and reflecting solar radiation back into space. In the Arctic summer months, sunlight is absorbed by the growing amounts of open water, raising surface temperatures and causing more ice to melt.
“I think one of the reasons the Arctic sea ice maximum extent is declining is that the autumn ice growth is delayed by warmer temperatures and the ice extent is not able to ‘catch up’ through the winter,” said Meier. “In addition, the clock runs out on the annual ice growth season as temperatures start to rise along with the sun during the spring months.”
Since satellite record keeping began in 1979, the maximum Arctic sea ice extent has occurred as early as Feb. 18 and as late as March 31, with an average date of March 6. Since the researchers determine the maximum sea ice extent using a five-day running average, there is small chance the data could change.
As of March 22, ice extent declined for five straight days. But February and March tend to be quite variable, so there is still a chance that the ice extent could expand again. Ice near the edge is thin and is highly sensitive to weather, scientists say, moving or melting quickly in response to changing winds and temperatures, and it often oscillates near the maximum extent for several days or weeks, as it has done this year.
In early April the NSIDC will issue a formal announcement on the 2011 maximum sea ice extent with a full analysis of the winter ice growth season, including graphics comparing 2011 to the long-term record.
The boundary where Earth’s crust gives way to the unexplored mantle was first detected in 1909, because of a change in the travel of seismic waves. Named the Moho boundary for Andrija Mohorovicic, who listened to those seismic waves, the crust-mantle boundary is a frontier that remains elusive and compelling — harboring tantalizing clues as to the story of Earth’s formation — even as our technologies push into the outer reaches of the solar system and beyond.
The first serious attempts to probe the Moho boundary ran aground in the late 1950s. Now, technology already in use on a Japanese ship, combined with a United States digging program already under way, could finally yield success. Damon Teagle and Benoît Ildefonse have written about the ongoing efforts for an article in the journal Nature, released today.
Teagle is at the University of Southampton’s National Oceanography Centre in the UK, and Ildefonse is at Université Montpellier in France. They are co-chief scientists on an expedition called the IODP Expedition 335, “to obtain for the first time a section of the lower oceanic crust — the material lying just above the mantle,” they write.
The IODP is using the U.S. ship JOIDES Resolution, pictured above, which will drill from April to June this year off the coast of Costa Rica.
“This site is in ocean crust that formed superfast — at more than 20 centimetres a year, much faster than any present day crust formation,” the co-authors write. “That makes the upper crust there much thinner than elsewhere, so it is possible to reach the lower portions without having to drill very deep. Three previous expeditions to Hole 1256D have drilled down to more than 1.5 kilometres below the sea floor, into the transition zone between dikes and gabbros.”
This spring they hope to push it another 400 meters, and recover gabbros from the lower crust, “which will be the deepest types of rock ever extracted from beneath the sea floor,” even though the deepest hole reached 2,111 meters under the eastern Pacific off of Colombia, they write.
Microphotograph of a mantle xenolith, sampled on Rapa Island in French Polynesia. The colourful minerals (seen here under the microscope in cross-polarized light, each grain is about 1 to 5mm large) are olivine, the main constituent of the upper mantle. Credit : Andréa Tommasi (CNRS, Géosciences Montpellier)
Teagle and Ildefonse note that some pieces of the mantle have been thrust up to Earth’s surface during tectonic mountain building, and ejected from volcanoes and sea floor dikes. Those samples have provided clues to the mantle’s composition, but they don’t reveal the variability of the mantle — and all of the samples have been altered by the processes that revealed them.
They say the IODP mission should help to settle many debates, including how crust is formed at mid-ocean ridges, how magma from the mantle is intruded into the lower crust, the geometry and vigor of how sea water can pull heat from the lower oceanic crust and the contribution of the lower crust to marine magnetic anomalies. The project will also provide “further impetus for, and confidence in, deep ocean crust drilling,” write Teagle and Ildefonse — but it will reach a depth far less than what will be needed to actually get at the Moho boundary. It occurs at least 30 kilometers (18 miles) under the continents but just 6 kilometers (3.7 miles) under the seas.
That’s where Chikyu comes in. Launched in 2002, “Chikyu is a giant ship, capable of carrying 10 kilometres of drilling pipes, and is equipped for riser drilling in 2.5 kilometres of water,” the authors write. Although Chikyu wouldn’t yet be able to go the full distance, its design is advanced enough to be the launching pad for such efforts:
“The vessel has a riser system: an outer pipe surrounds the drill string — the steel pipe through which cores are recovered,” the co-authors write. “The drilling mud and cuttings are returned up to the vessel in the space between the two pipes. This helps to recycle the drilling mud, control its physical properties and the pressure within the drill hole and helps to stabilize the borehole walls.”
Teagle and Ildefonse say the ideal drilling program to reach the mantle boundary will happen in one of three places — off the coasts of Hawaii, Baja California and Costa Rica — where the water is the most shallow, over the coldest possible crust. Wherever and however it happens, they write, it will be worth doing:
“Drilling to the mantle is the most challenging endeavour in the history of Earth science. It will provide a legacy of fundamental scientific knowledge, and inspiration and training for the next generation of geoscientists, engineers and technologists.”
Source: Nature. See also the websites for Chikyu and JOIDES.
