Dune Gallery

The November 2012 issue of National Geographic features an article, “Sailing the Dunes,” about aerial trips over sandy deserts. The author, George Steinmetz, has flown in light aircraft in high winds—a dangerous combination. Yet the same winds that make the flying so dangerous also sculpt some of the world’s most beautiful landscapes. Several of the places mentioned in the article have also been covered by the Earth Observatory. Here is a sampling of some of those places, plus some additional dune-rich landscapes.

The Sahara Desert spans northern Africa, covering about 9.4 million square kilometers (3.6 million square miles). Within the Sahara are multiple sand seas, or ergs — big, windswept landscapes of shifting sands. The ergs can be as photogenic as they are forbidding.

Issaouane Erg in Algeria holds multiple crescent-shaped (barchan) dunes and star dunes. Winds blowing mostly from one direction create barchan dunes while variable winds create star dunes. Low-angled sunlight highlights the varied dune shapes in this region. Story: Issaouane Erg, Algeria

Besides barchan dunes and star dunes, Issaouane Erg is also home to mega-dunes. Mega-dunes likely take hundreds of thousands of years to form, and may have started their formation when the Sahara—once a more hospitable place—began to dry. In between the big dunes, winds have swept sand away from the desert surface altogether, revealing gray-beige mud and salts. Story: Dune Types in the Issaouane Erg, Eastern Algeria

The flat areas between dunes are known as dune streets, and they are unmistakable in Algeria’s Erg Oriental. In between the streets, star dunes sit atop linear dunes. Story: Erg Oriental, Algeria

Nearly sand-free basins also separate complex dunes in the Marzuq Sand Sea of southwestern Libya. The big sand masses are known as “draa” dunes, Arabic for “arm.” Extending from some of the draa dunes are snakelike linear dunes. Story: Sand Dunes, Marzuq Sand Sea, Southwest Libya

Dunes form in arid conditions, but conditions can change. The manmade Toshka Lakes of Egypt flooded old dune landscapes. Depending on lake levels and the underlying topography, some dunes are completely flooded while the crests of others poke above the water surface. Story: Toshka Lakes, Egypt

Although it covers an area much smaller than the Sahara Desert, the Arabian Peninsula’s Empty Quarter, also known as Rub’ al Khali, holds half as much sand as the entire Sahara. Salt flats—sebkhas or sabkhas—separate the towering dunes. Story: Empty Quarter

Though it lacks the massive sand seas of the Sahara and the Arabian Peninsula, the United States sports some impressive dune fields of its own. White Sands National Monument holds gleaming white sands formed from gypsum. These brilliant white dunes occur at the northern edge of the Chihuahuan Desert, which extends across the U.S.-Mexico border. Story: White Sands National Monument

The Algodones Dunes of southeastern California lack the snowy look of White Sands, but make up for it by hosting a complex assortment of dune formations. Smaller dunes sit on top of giant crescent-shaped dunes. Wind does not act alone in shaping this landscape; water flows off the Cargo Muchacho Mountains to the east, making its way into the dune field and sustaining some plant life. Story: The Algodones Dunes

Some of the world’s most complex dune formations occur in the Badain Jaran Desert of Inner Mongolia. Small lakes dot flat areas in between dunes, which have been characterized as “complex reversing mega-dunes developed from compound barchanoid mega-dunes.” Story: Elevation Map of the Badain Jaran Desert

And sometimes a single desert can host completely different landscapes. Identified by satellite data as the hottest place on Earth, Iran’s Lut Desert contains two completely different landscapes. The central portion is home to wind-sculpted linear ridges known as yardangs. The southeastern part of the desert hosts dunes that soar to 300 meters (1,000 feet) alternating with salt pans. Story: Diverse Terrain of Iran’s Dasht-e Lut

Note that due to the angle of sunlight, some of these images produce an optical illusion known as relief inversion.

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Crane Glacier Terminus Retreat

On October 25, 2012, we published a set of images that shows how the Hektoria and Green glaciers on the Antarctic Peninsula have continued thinning since the Larsen-B ice shelf’s collapse in 2002.  Though those two glaciers have been some of the fastest changing in recent years, they aren’t the only Larsen-B tributary glaciers that have lost ice over the last decade.

In all, the 15 glaciers that flow into the ice shelf have lost more than 10 gigatons (one gigaton equals one billion tons) of mass per year, according to research published in the Journal of Glaciology. Some of the most dramatic changes have occurred at Crane, the longest of the Larsen B tributary glaciers. Since the collapse of the ice shelf, Crane Glacier has retreated by more than 12 kilometers (7 miles).

This visualization, based on an image captured by the Advanced Land Imager (ALI) instrument on the Earth Observing-1 (EO-1) satellite, shows the location of the terminus in April 2002, February 2003, and February 2006. Since 2006, the terminus has stayed in the same general position. The image was acquired on February 24, 2012.  For another view of Crane glacier’s retreating terminus, please see this image.

NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using EO-1 ALI data provided courtesy of the NASA EO-1 team.

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NASA Release: Suomi NPP Captures Night View of U.S. Before Hurricane Sandy’s Landfall

The following is a cross-post of a news release written by our colleagues Rob Gutro and Laura Betz in NASA public affairs and Suomi NPP outreach…

As Hurricane Sandy made a historic landfall on the New Jersey coast during the night of October 29, the Visible Infrared Imaging Radiometer Suite (VIIRS) on NASA/NOAA’s Suomi National Polar-orbiting Partnership (Suomi NPP) satellite captured this nighttime view of the storm. This image, provided by University of Wisconsin-Madison, is a composite of several satellite passes over North America taken 18 hours before Sandy’s landfall.

The storm was captured by a special “day-night band,” which detects light in a range of wavelengths from green to near-infrared and uses filtering techniques to observe dim signals such as auroras, airglow, gas flares, city lights, fires and reflected moonlight. City lights in the south and mid-section of the United States are visible in the image.

William Straka, associate researcher at Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin-Madison, explains that since there was a full moon there was the maximum illumination of the clouds.

“You can see that Sandy is pulling energy both from Canada as well as off in the eastern part of the Atlantic,” Straka said. “Typically forecasters use only the infrared bands at night to look at the structure of the storm. However, using images from the new day/night band sensor in addition to the thermal channels can provide a more complete and unique view of hurricanes at night.”

VIIRS is one of five instruments onboard Suomi NPP. The mission is the result of a partnership between NASA, the National Oceanic and Atmospheric Administration, and the U.S. Department of Defense.

On Monday, Oct. 29, around 8 p.m. EDT, Hurricane Sandy made landfall 5 miles (10 km) south of Atlantic City, N.J., near 39 degrees 24 minutes north latitude and 74 degrees 30 minutes west longitude. At the time of landfall, Sandy’s maximum sustained winds were near 80 mph (130 kph) and it was moving to the west-northwest at 23 mph (37 kph). According to the National Hurricane Center, hurricane-force winds extended outward to 175 miles (280 km) from the center, and tropical-storm-force winds extended 485 miles (780 km). Sandy’s minimum central pressure at the time of landfall was 946 millibars or 27.93 inches.

Suomi NPP was launched on Oct. 28, 2011, from Vandenberg Air Force Base, Calif. One year later, the satellite has orbited Earth more than 5,000 times and returned images and data that provide critical weather and climate measurements of complex Earth systems. Suomi NPP observes nearly every location on Earth’s surface twice every 24 hours, once in daylight and once at night. NPP flies 512 miles (824 kilometers) above the surface in a polar orbit, circling the planet about 14 times a day. NPP sends its data once an orbit to the ground station in Svalbard, Norway, and continuously to local, direct-broadcast users.

For storm history, images, and video of Hurricane Sandy, please visit the following websites:

http://www.nnvl.noaa.gov

http://www.nasa.gov/mission_pages/hurricanes/archives/2012/h2012_Sandy.html

http://cimss.ssec.wisc.edu/goes/blog/

http://earthobservatory.nasa.gov/NaturalHazards/event.php?id=79504

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A view of Sandy from the TRMM satellite

 Check our Hurricane Sandy event page, our YouTube page, and NASA’s Hurricane Resource page for the latest storm images from NASA.

NASA hurricane researcher Owen Kelley prepared this image and caption.

The day before Hurricane Sandy’s center was forecast to make landfall in New Jersey, the radar on the Tropical Rainfall Measuring Mission (TRMM) satellite observed the hurricane’s center.

At 2:20 EDT on Sunday October 28, Hurricane Sandy was a marginal category 1 hurricane and its eyewall was modest, as TRMM reveals, which gives us hints about its possible future strength.

The eyewall was somewhat compact with its 40 km diameter; the eyewall contained only relatively light precipitation; and none of Sandy’s eyewall storm cells managed to burst through, or even reach, the tropopause, which has about a 10 km height at mid-latitudes. Evidence of the weak updrafts in the eyewall comes from the fact that the TRMM radar’s reflectivity stayed under 40 dBZ, a commonly cited signal strength at which updrafts can be vigorous enough to form hail and to lift smaller ice particles up through the tropopause and into the stratosphere.

But placed in context, the TRMM-observed properties of Hurricane Sandy’s eyewall are evidence of remarkable vigor. Most hurricanes
only have well-formed and compact eyewalls at category 3 strength or higher.  Sandy was not only barely a category 1 hurricane, but
Sandy was also experiencing strong wind shear, Sandy was going over ocean typically too cold to form hurricanes, and Sandy had been limping along as a marginal hurricane for several days.

With infrared satellite observations (as in the background of the images show), one can speculate about what the sort of convective storms are developing under the hurricane’s cloud tops, but Sandy was sneaking up the East Coast too far out at sea for land-based radars to provide definitive observations of the rain regions inside of the hurricane’s clouds. The radar on the TRMM satellite provided this missing information during this overflight of Hurricane Sandy.

The TRMM satellite also showed that the super-sized rainband that extended to the west and north of the center did contain vigorous
storm cells, as indicated by the red regions of radar reflectivity in excess of 40 dBZ. This rainband is expected to lash the coast well before the hurricane’s center make landfall.  Even further west, at the upper left corner of the image, one can see two small storm cells.  These storm cells are the southern-most tip of the independent weather system that is coming across the United States and that is expected to merge and possibly reinvigorate the remnants of Hurricane Sandy after Sandy makes landfall.

TRMM is a joint mission between NASA and JAXA, the Japan Space Exploration Agency.  Some of the questions about hurricanes left unanswered by the TRMM satellite will be explored by the Global Precipitation Measuring (GPM) satellite scheduled for launch in 2014.  For more information, visit http://pmm.gsfc.nasa.gov.

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Keeping track of changing landscapes

When you look at a parcel of Earth’s surface at a moment in time, it can be hard to grasp the story behind the image. It’s a snapshot, a fleeting glimpse. Does it always look like that?  Am I seeing this place on a normal day, an abnormal day, an everyday? Where’s the motion, the action, the dynamics?

For instance, take a look at this collection of lakes amidst the barren, salt-crusted landscape of central Asia.

The size of these freshwater lakes is compelling…tens to hundreds of kilometers long…oases of green and blue amidst the tans of the desert. These “inland seas” are impressive. That is, until you look at that same region a decade earlier (below)…or forty years earlier.

Through the lens of time, the planet comes to life. The color of the landscape changes, waters rise and fall, ice advances and retreats. The planet has vital signs. Earth Observatory’s World of Change series offers some visual vital signs for 23 different landscapes and locales on Earth, with images updated across seasons to decades, depending on the length of the satellite record.

Our newest updates include 2012 images for the Aral Sea (sampled above) and for the Hobet Mine, a mountaintop coal-mining operation in West Virginia.

What do you think we should show in future installments of World of Change?  (Keep in mind that it has to be something we can see or measure via satellite.)

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Which do you prefer: active fires or burn scars?

The Pole Creek fire is hardly breaking news. As of October 20, 2012, authorities announced that the blaze was 100 percent contained. In early October, when we first published this image that the Terra satellite acquired in September, the fire was still burning wildly and sending up smoke plumes that shrouded the Three Sisters and the surrounding communities in a heavy layer of smoke.

A few weeks later, on October 5, a different instrument on a different satellite—the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 satellite—acquired a false-color view of the fire (below). Rather than smoke billowing from an actively burning fire, the image features the burn scar left behind.

In ideal circumstances, we publish images of a fire while it is actively burning and also after the fact. But, in some cases, either because the satellites don’t acquire usable images or because we simply don’t have time to post them, we end up showing one view or the other.

There’s no shortage of fires we could show. (To get a sense of this, take a look at this map of global fire activity to see the constant presence of wildfires on our planet.) If we wanted, we could show only active fires with smoke, only burn scars, or any combination of the two and still have far more images than we could possibly post.

But which view do you prefer?  And how late is too late? If a fire has been under control for day or weeks are you still interested in seeing the event or the scars that it left behind?

And what about other types of natural disasters like storms or volcanic eruptions?  If a storm has already broken up, if a volcanic ash plume has dissipated, if a hurricane has no chance of making landfall…are you still interested in seeing it, or does it just feel like old news?

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Well…how did I get here?

As part of Earth Science Week, various NASA scientists and staff have been writing and talking about what it is like to work in science. One of those staff members is our colleague, Jefferson Beck, a documentary producer turned NASA science communicator…

So I’m flying at 1,500 feet above a giant crack in the Pine Island Glacier. By “giant” I mean up to 800 feet across, deeper than the Statue of Liberty, and 18 miles long.  I’m in a NASA DC-8 aircraft with Operation IceBridge, the first airborne mission to take detailed measurements of such a massive calving event in progress.  If this chunk of the Antarctic ice shelf splits off and floats away as one big piece, it will be the size of New York City. 

As the video producer assigned to this mission, I’m trying to make the most out of the few moments where the scenery isn’t just impressive, but truly stunning.  My stomach is tight with excitement and worry that I’ll miss the best shots.  I have one camera set up recording a time-lapse out one window, and I’m holding another camera against another window. I’m bracing myself with a ratty piece of foam against the fuselage and trying to find a clear spot among the window’s many scratches as the plane bounces along.  The Crack looms large for a while, then quickly fades from sight and gets lost in the whiteness.

After we finish our flight lines, we bank out over the razor-sharp edge where the ancient Antarctic ice meets the dark water.  We start to gain altitude for the long flight back to Punta Arenas, Chile, a port city on the Strait of Magellan.  As we climb, I think about how few people have gotten to see the frozen continent from this perspective.  Then I look around at the amazingly talented group of people on board, and think: “how did I wind up here?”

You’d think that most people who work at NASA are numerical geniuses who spent their high school years building robots and answering math problems for fun.  And we do have people like that.  We also have people who could rebuild an engine when they were 14 and people who had their pilot’s license at 17.

But for me, high school was many things and the path was not always clear.  High school was cross country and track, the school newspaper, reading lots of science fiction, smudging my way through art classes, dropping an essay-writing class to have double-lunch with my girlfriend, struggling a bit with math, and really enjoying most of my science courses.

My continuing issues with math — and, as it turned out, chemistry — didn’t stop me from becoming a biology major in college. There I focused on ecology and natural history.  After that, my plan was to become a biologist, so for a while I ended up in Alaska standing in frozen streams and counting wild salmon.  I loved being in the field and I loved the natural world, but slowly the idea of being a research scientist began to fade.

Not knowing what to do next, I went back home to Ohio.  I couch-surfed for a while before landing a job as a reporter for a small-town newspaper.  Then I helped build a local bike trail, did some reporting for radio, and then got involved with non-profit community-building work.  For a while, I was a bouncer in a bar one night a week.  Finally, I landed in filmmaking.  I took some film classes, worked on a couple of indie features, and made some little films of my own.

It all kind of looks like a jumbled mess, doesn’t it?  It doesn’t make you think, “well, here’s a guy who is destined for NASA.”  It’s what career-minded people call “lateral moves,” jumping sideways from one career track to another without much advancement – the kinds of moves that make some parents scratch their heads and start to worry.

But all that experience led me to finally apply to a grad school program in science and nature filmmaking at Montana State University.  I got accepted, and later got my job at NASA, because I was able to tell a story – a true story – using the skills I had gained from all those lateral moves.  I could write, manage a project, understand scientists, recognize news, work in the field, dig deep and endure adversity [claiming this one from my 10 years running cross country and track], and make a video.

So my take home message is this:  If you’re one of those focused people who know exactly what they want to do and head straight for it, fantastic.  One day you’ll be flying the plane I’m riding in, designing one of our satellites, or sending us to Mars.  And I’ll be grateful for your skills.  But if your career path wanders, don’t worry.  If you keep learning as you go, one day it will make for a very interesting true story.

This month I’m heading back to Chile, and back to flying at 1,500 feet over the Antarctic ice, and maybe even back to the Pine Island Glacier, which finally seems ready to give up its New York City-sized chunk of ice.   Wherever we fly, it will be exciting.  And difficult, and beautiful, and scientifically valuable.  There will be a lot of true stories out there, and I’ll do my best to bring them home.

Watch Jefferson’s video: Flying through the Rift: An update on the crack in the Pine Island Glacier.

Learn more about other Earth Explorers like Jefferson on the NASA Earth Science Week website.

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Earth Science Week 2012 at NASA

October 14–20 is Earth Science Week. This annual celebration started in 1998, established by the American Geosciences Institute to help children, students, and the general public understand how geoscientists collect information about our planet.

In 2012, the theme is “Discovering Careers in the Earth Sciences” and involves activities by NASA, the U.S. Geological Survey, the National Park Service, and multiple professional associations. Online resources for Earth Science Week include tools for teachers, students, and the media. Highlights of Earth Science Week 2012 include National Fossil Day on October 17, Female Geoscientist Day on October 18, and Geologic Map Day on October 19.

From the Global Climate Change Earth Science Week Blog: Explorer Christy Hansen hugs the Russell glacier, part of the Greenland Ice Sheet. Image courtesy Christy Hansen, JPL

NASA plays an active role in the celebration, hosting activities and offering an ESW web site with a blog, an events page, a videos page, and explorer articles. These resources (including several in Spanish) introduce visitors to NASA’s Earth Explorers — scientists, engineers, educators, multimedia producers, and writers — who describe their work, their motivations for studying our planet, and the kinds of challenges they face on a daily basis.

The schedule of NASA-sponsored events includes:

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October Puzzler Answer: Turkish Glaciers

Congratulations to Britton, Dakota Steve, Alev Akyildiz, and Eric Jeffrey for being the first readers to solve the October puzzler. We posted the image on Tuesday afternoon, and by Wednesday morning Britton had worked out that the location was Mount Uludoruk in the southeastern Taurus Mountains. Later on, Dakota Steve added that it must have been taken in the fall, Alex Akyildiz was the first to give the exact coordinates, and Eric Jeffrey added some interesting details about glacial recession.

Many thanks to Mehmet Akif Sarikaya of Fatih University for providing some of the information that went into the caption we published as our Image of the Day for October 13. Among other things, Sarikaya pointed us to a fascinating account that a British solider (Major F.R. Maunsell) read to members of the Royal Geographical Society after a trip to the region.  The account was published in August 1901 by the Geographical Journal.  In addition to Maunsell’s colorful writing, the article included the first known image of one of Uludoruk’s glaciers.

Here are a few excerpts from Maunsell’s description of the topography near the site of his photograph:

…A little south of the main ridge of Geliashin, and forming part of the group, are two masses of rock, one the Tura Dauil (David’s mountain), and facing it across a deep chasm-like valley, the other called Nakhira Shirka, both rising to about 11,000 feet. The north slopes of Geliashin and Suppa Durek are perhaps the grandest, as the ground falls away in a splendid succession of crags and precipices into the head of the valley of Des or Deezan, and the stream-level of the Great Zab, only 12 miles off, but 9270 feet lower. Below the crest a small glacier nestles under Geliashin on the north, giving rise to the Des stream, called in Turkish the Kar Su, or Snow water, and in Syriac, Mia Khwara, or White water…

…On all sides, except a narrow ridge on the south-east, are sheer precipices of several hundred feet, and after three attempts, in each of which I was brought up against lines of huge cliffs, I finally discovered that a steep path to the summit existed on the south-east side, but it was too late then to attempt it. The only guides procurable were very misleading, making any statement, if they thought it would please, and were very difficult to verify. The summit ridges swarm with ibex and moufflon, and many of the giant partridge were also seen. Judging from Galianu, the summit of Geliashin must be at least 1500 feet higher, or 13,500 feet above sea-level…

…From Geliashin a razor-edged ridge of limestone rock runs nearly due west for a few miles, and terminates in a very sharp-pointed peak known as the Suppa Durek, or Lady’s Finger (mentioned by Layard), a prominent landmark in the confused outline of crag and. pinnacle west of Geliashin. A col which gives access by a stair-like path from the Zab valley into Jelu district now intervenes to the west, beyond which runs a rugged watershed range of lesser elevation, but containing the sharp peak of Khisara, quite inaccessible except by the wild goats,and enclosing the rocky gorges of Kiyu and IUri draining to the Zab, and overlooking Jelu and Baz to the south.

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October Puzzler

Every month, NASA Earth Observatory will offer up a puzzling satellite image here on Earth Matters. The fifth puzzler is above. Your challenge is to use the comments section below to tell us what part of the world we’re looking at, when the image was acquired, and what’s happening in the scene.

How to answer. Your answer can be a few words or several paragraphs. (Just try to keep it shorter than 300-400 words). You might simply tell us what part of the world an image shows. Or you can dig deeper and explain what satellite and instrument produced the image, what bands were used to create it, and what’s interesting about the geologic history of some obscure speck of color in the far corner of an image. If you think something is interesting or noteworthy about a scene, tell us about it.

The prize. We can’t offer prize money for being the first to respond or for digging up the most interesting kernels of information. But, we can promise you credit and glory (well, maybe just credit). Roughly one week after a “mystery image” appears on the blog, we will post an annotated and captioned version as our Image of the Day. In the credits, we’ll acknowledge the person who was first to correctly ID an image. We’ll also recognize people who offer the most interesting tidbits of information. Please include your preferred name or alias with your comment. If you work for an institution that you want us to recognize, please mention that as well.

Recent winners. If you’ve won the puzzler in the last few months, please sit on your hands for at least a few days to give others a chance to play.

You can read more about the origins of the satellite puzzler here. Good luck!

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