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Earth Matters

On top of all the great science they make possible, satellites often produce imagery that is simply beautiful.

This image of Turnabout Glacier on Canada’s Ellesmere Island is a case in point. It shows a classic piedmont glacier that looks almost like pancake batter spilling over a frozen landscape. Piedmont glaciers form when steep valley glaciers spill out into relatively flat plains. Unchained from the constraints of the terrain, the ice flows freely in all directions.

Image Credit: NASA Earth Observatory/ASTER/Jesse Allen

The Advanced Spaceborne Thermal Emissions and Reflection Radiometer (ASTER) instrument on NASA’s Terra satellite acquired an image of the glacier and its surroundings on July 26, 2009. The summertime image shows the glacier free of overlying snow from the previous winter. Banding in the surface of the ice shows different years in which the ice was laid down on the glacier.

Image Credit: NASA Earth Observatory/ASTER/Jesse Allen

In the wider view, you can see glaciers drain out of ice caps between mountain peaks and ridgelines. Many features, including Turnabout, were first formally cataloged in 1957 and 1958 as part of the first International Geophysical Year (IGY). This area is so far north and the weather so cold much of the year that there has been little in the way of human footprints on the landscape. Hence, features had no official names within the scientific community before the IGY.

Humans have, though, made one visible impact on this image. The line on the top left is a contrail from a plane. Contrails form when water-rich exhaust from jet engines freezes into tiny ice crystals at high altitude.

Compare Turnabout to Eugène Glacier in the wider view. Both are classic piedmont glaciers, but Turnabout exits the mountain pass into the Hazen Plain with some obstacles that cause it to twist and turn before ending and draining into the Turnabout River. Eugène Glacier has no such obstacles and spreads out more evenly.

This false-color image was made by combining observations of near infrared, red, and green light. Red indicates vegetation; the chlorophyll in plants reflects much more strongly in the near infrared than other wavelengths.

Earth Observatory is Part of the New Google Earth

April 25th, 2017 by Kevin Ward

On April 18, I had the opportunity to participate in the launch of the newest version of Google Earth, which now includes some collaboration with the NASA Earth Observatory. The Google Earth team even used two image collections from EO to highlight some of the functionality of their new product.


Google Earth landing pages

Image Credit: Google Earth screenshot of NASA Earth Observatory imagery.

The first is Reading the ABCs from Space, which is a republishing of our planetary-scale scavenger hunt (which was partly built with assistance from our letter-hunting readers). The second collection is Scenes from Space, a curated selection of recent EO Images of the Day. The Scenes from Space collection will continue to be updated monthly by the Google Earth content team.

This launch event provided us with the opportunity to meet with media and other potential users of the 14,000 images and stories that have been produced by the Earth Observatory team since our establishment in 1999. We syndicate our content through a variety of different feed formats, and the Google Earth team will be utilizing those feeds to keep their NASA Earth content up to date.

Google Earth press event

Image Credit: NASA/Jamie Favors

We hope that other users can use these feeds for their various applications, and if you are one of those users, please let us know what we can do to help you. The vast majority of our imagery and all of our stories are freely available without any license restrictions (though we hope that you will provide proper credit). Perhaps you might even consider the Earth Observatory as a resource for the upcoming NASA Space Apps Challenge.

Google Earth event badge

Image Credit: NASA Earth Observatory/Kevin Ward

Petermann Glacier’s New Crack

April 24th, 2017 by Kathryn Hansen

In early April, remote sensing scientist Stef Lhermitte examined Sentinel-2 satellite images and saw a new crack developing on Greenland’s Petermann Glacier. About two weeks later, Landsat 8 also got a look (top image). Read more about that image here.

But the space-based view is not the only evidence of a new crack in the large glacier. NASA’s Operation IceBridge has been making science flights in the area this month, and scientists got a first-hand look. Kelly Brunt, a glaciologist at NASA’s Goddard Space Flight Center, snapped the photograph above from a window of a P-3 Orion research plane on April 14. The new crack is the feature running diagonal from the bottom-left of the photo toward the center.

“What’s interesting here is that the crack originated in the center of the glacier, not along the edges,” Brunt said. “When John Sonntag and I were looking for the new crack during the flight, we were looking for something substantial emanating from the edge. This totally surprised me!”

Most cracks start along a glacier’s edge, where a huge amount of strain is produced as the glacier slides along the walls of a fjord. That is especially true for Petermann—a narrow glacier that has previously rifted along the edges of its floating shelf.

Cracks that make their way across an ice shelf can eventually release icebergs. Petermann has launched two huge icebergs since 2010, so scientists are watching for additional retreat. It remains to be seen whether this crack will result in an iceberg. If the crack continues to lengthen, it could potentially meet the older rift at the edge of the glacier, visible near the top-center of the photo.

View more images of the rift and other icy phenomenon here.

An Optimistic View For Earth Day

April 21st, 2017 by Adam Voiland

By removing natural and stray light sources, researchers have provided a clearer picture of the human footprint on Earth. Learn more about this image. (NASA Earth Observatory image by Joshua Stevens, using Suomi NPP VIIRS data from Miguel Román, NASA GSFC.)

As we arrive at Earth Day 2017, reporting on Earth science can sometimes feel like a gloomy affair. Global temperatures are at record highs. Arctic sea ice is in pretty bad shape. Bleaching events are taking a toll on coral reefs. And as an interesting article in EOS recently noted, humanity is affecting the very shape of Earth’s surface in unprecedented ways.

“We have altered flood patterns, created barriers to runoff and erosion, funneled sedimentation into specific areas, flattened mountains, piled hills, dredged land from the sea, and even triggered seismic activity,” the authors wrote. (Read our stories about land reclamation in China, mining in Canada, gas and oil infrastructure in Texas, the growing Wax Lake Delta in Louisiana, and the retreat of the Aral Sea to see changes of this nature.)

In spite of the challenges in a changing world, there are reasons to be optimistic. The world has come together to confront global problems before. Levels of protective ozone are stabilizing because of the Montreal Protocol. In the United States and Europe, better technology and regulations have led to drastic reductions in air pollutants such as sulfur dioxide and nitrogen dioxide. There are signs that efforts to clean up the Chesapeake Bay are making a difference.

NASA’s operating Earth science missions as of March 31, 2017. (Image Credit: NASA’s Earth Observing Project Science Office.)

Some of the environmental challenges we face are daunting and can seem intractable, but there are some good reasons to feel reassured by the tools and expertise that the scientific community brings to the table. Americans live in a country where the number of deaths due to hurricanes, landslides, floods, droughts, tornadoes, blizzards, and other weather hazards have plummeted over the past century, and that is largely due to better understanding and to appropriate hazards warning systems that Earth scientists have developed.

Computers and instruments that used to take up whole rooms now fit snugly onto autonomous aircraft, satellites, and robots. At this moment, 1,459 satellites orbit Earth—including 19 that are part of the NASA fleet keeping a watchful eye on this dynamic, fragile planet. The authors of the EOS article note that a unified, global, high-resolution 3-D map of the human fingerprint on Earth is within reach due to the remarkable lidar instruments, aerial photogrammetry, and satellite observations that are now available.


NASA invites people around the world to help us celebrate Earth Day 2017 by “adopting” one of 64,000 individual pieces of Earth as seen from space. Learn more. (Image Credit: NASA)

To get a sense of the sophistication and breadth of the information satellites now collect, just navigate to your home town with NASA’s Worldview browser or take a look at the Earth Observations (NEO) data archive. You will find information on everything from plant health to particulate aerosol levels to fires to city lights.

As you look, keep in mind that NASA isn’t just collecting that data for data’s sake. The Applied Sciences program is focused on making that data useful to citizens, resource managers, and civic planners in ways that make life better here on Earth. So if you plan to celebrate Earth Day by cleaning up trash in your neighborhood or adopting a piece of the planet with NASA, rest assured that you are not alone in working to make the planet just a little bit more livable.


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On April 4, 2017, archaeologist Mark Walters tweeted an intriguing set of satellite images of a dark smear on the Larsen C Ice Shelf. Was it volcanic ash from a recently active volcanic vent, he wondered?

The tweet — and especially a bright, red spot in an infrared image (lower right in the screenshot) — generated interest among folks who follow Earth science, Antarctica, and volcanoes. New volcanic activity in this area would be surprising and newsworthy. While there is some evidence of volcanic activity near this part of the Larsen Ice Shelf, the most recent reports date back to 1980.

Some remote sensing experts who saw the images were skeptical. “I looked through about four months of satellite images before/after and never saw anything that resembled a plume. Think it’s dust on ice,” tweeted Erik Klemetti, an associate professor at Denison University and author of Wired’s Eruptions blog.

Later, CNRS scientist Simon Gascoin weighed in, noting that the underlying geology in that area was sedimentary rock—a sign that volcanic activity wasn’t likely. Then he shared even stronger evidence against the idea of volcanic activity.

In an email, I asked Gascoin to clarify what he meant by “no gain rescaling” and why his image from the Sentinel Playground looked so different in comparison to the image from Land Viewer.

His reply: “Mark Walters used the Land Viewer, I just checked and found out that the ‘contrast stretching‘ is computed on each RGB band separately. Hence you can get strange results, especially in cases where a single rock island is surrounded by snow and ice which have a very distinct reflectance signature.”

In other words, Gascoin is saying that the image-processing algorithm that drives the Land Viewer browser amplified the reflectance signal from the dust in a way that made it appear stronger in the infrared than it actually was. Sentinel Playground uses a different image processing approach (adjusting the contrast of the image “bands” all at once rather than individually) to avoid the problem.

Satellite instruments carry many sensors that are each tuned to a narrow range, or “band,” of wavelengths (just red or green light, for instance). This chart shows how the bands of sensors on the Sentinel-2, Landsat 7, and Landsat 8 satellites compare. To make a satellite image, three different bands are represented in tones of red, green, or blue. A false-color image uses at least one non-visible wavelength, though that band is still represented in red, green, or blue. Read this story to learn more about how observations made in the infrared are displayed in false-color images.

Meanwhile, experts from the Smithsonian’s Global Volcanism Program had arrived at a similar conclusion. “It seems unlikely that this is an eruption for a few reasons,” emailed Benjamin Andrews. “First, Table Nunatak is formed of Cretaceous rocks, with no evidence of recent activity. Second, it is located pretty far from any other volcanoes, and there doesn’t appear to be a good tectonic explanation for current magmatism at Table Nunatak.”

So, the mystery appears to be solved. As interesting as it would have been, there is no new volcanic activity happening in this part of Larsen C.

Bigger isn’t necessarily better—at least where satellites are concerned. Modern “CubeSat” satellites are smaller and more numerous than ever.

The CubeSat takes its name from its dimensions; it is made up of multiples of 10×10×11 centimeter cubic units. A basic CubeSat weighs roughly 3 pounds (1.3 kilograms) and looks a good deal like a portable speaker.

Image by NASA Ames.


Early satellites started out small, too. Launched in 1957, Sputnik weighed around 184 pounds (83 kilograms). America’s first satellite, Explorer I, weighed just under 31 lbs (14 kg). Then, as the desire for more sensors grew, so did the size of satellites. The first American weather satellite, TIROS I, was a hefty 270 lbs (122 kg). But recent years have seen a reversal of this trend.

Explorer I. Image by NASA.

Like modern cell phones, satellites have benefited from more compact and more powerful computing technology. (A 1980s cell phone was an expensive, brick-sized gadget that could only place phone calls and store a couple dozen numbers.) Satellites, too, have sprouted new cameras and sensors. Take the IPEX CubeSat developed by NASA’s Jet Propulsion Laboratory (45 seconds into the video below); it can track features like forest fires, volcanic eruptions, and algae blooms.


A satellite today can be a “hitchhiker,” aboard a larger mission, as the video below mentions. Or, a CubeSat can be launched from the International Space Station.

Because they are smaller, CubeSats tend to cost less, so research organizations can deploy more of them. That means more spatial coverage for monitoring the Earth. Where researchers once relied on two or three larger satellites to keep an eye on weather over the Pacific Ocean, now, handfuls of smaller satellites can help with the job.

NASA is not the only organization that builds CubeSats. The space agency has delivered little satellites made by private companies, college students, and even grade school students.

To learn more, watch the video below. Or read more here.


On This Date: The Bingham Canyon Landslide

April 10th, 2017 by Adam Voiland

NASA/EO-1/ALI/Jesse Allen and Robert Simmon. More info about this image here.

Four years ago today, one of the largest non-volcanic landslides in U.S. history began high on the northern wall of Utah’s Bingham Canyon mine. During two main bursts of activity that day, several million cubic meters of rock and soil careened deep into the mine’s pit.

This was a case where science and the right preparation saved lives. The company that runs the mine had installed an interferometric radar system months before the slide, and it prevented miners from being blindsided. With the radar system in place, mine operators detected changes in the stability of the pit’s walls well before the landslide occurred. When the slope finally gave way, all the workers in the pit had already been evacuated. Not one person was injured.

The image above was acquired by the Advanced Land Imager (ALI) on the Earth Observing-1 satellite on May 2, 2013. For more detailed and recent images of the mine pit, see the montage below. Photos A, B, and C — from Rio Tinto Kennecott — show an overview of the pit, the source area, and slide debris in the immediate aftermath of the event. D is an aerial image from the state government of Utah that shows the mine nine months before the landslide. E is part of the ALI satellite image above. F is a second aerial image taken in February 2014. By then, much of the debris had been removed and a new access road had been built.

The montage was originally published in March 2017 by the Journal of Geophysical Research as part of a study authored by Jeffrey Moore of Lawrence Livermore National Laboratory. The University of Utah wrote about the research in a recent blog post:

On April 10, at 9:30 p.m. and again at 11:05 p.m., the slope gave way and thundered down into the pit, filling in part of what had been the largest man-made excavation in the world. Later analysis estimated that the landslide was at the time the largest non-volcanic slide in recorded North American history. Now, University of Utah geoscientists have revisited the slide with a combined analysis of aerial photos, computer modeling, and seismic data to pick apart the details. The total volume of rock that fell during the slide was 52 million cubic meters, they report, enough to cover Central Park with 50 feet of rock and dirt. The slide occurred in two main phases, but researchers used infrasound recordings and seismic data to discover 11 additional landslides that occurred between the two main events. Modeling and further seismic analysis revealed the average speeds at which the hillsides fell: 81 miles per hour for the first main slide and 92 mph for the second, with peak speeds well over 150 mph.

The interferometric radar system is not the only safety technology in place at Bingham Canyon. Drones, GPS, and trained experts keep a vigilant eye out for signs of landslides at this mine. Technology and tactics like this  mean landslides cause very few injuries and deaths in the United States even though significant landslide potential exists in many parts of the country. As we recently reported, many other parts of the world (notably Africa and South America) are not nearly so fortunate.

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April Puzzler

April 10th, 2017 by Kathryn Hansen

Every month on Earth Matters, we offer a puzzling satellite image. The April 2017 puzzler is above. The challenge this month, however, is slightly different. Use the comments section to tell us not only WHERE we are looking, but WHAT we are looking at. As usual, we welcome ideas about when the image was acquired, and why the scene is interesting.

How to answer. Your answer can be a few words or several paragraphs. (Try to keep it shorter than 200 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 spectral bands were used to create it, or what is compelling about some obscure speck in the far corner of an image. If you think something is interesting or noteworthy, tell us about it.

The prize. We can’t offer prize money or a trip to Mars, but we can promise you credit and glory. Well, maybe just credit. Roughly one week after a puzzler image appears on this blog, we will post an annotated and captioned version as our Image of the Day. After we post the answer, we will acknowledge the person who was first to correctly ID the image at the bottom of this blog post. We may also recognize certain readers who offer the most interesting tidbits of information about the geological, meteorological, or human processes that have played a role in molding the landscape. Please include your preferred name or alias with your comment. If you work for or attend 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 or work in geospatial imaging, please sit on your hands for at least a day to give others a chance to play.

Releasing Comments. Savvy readers have solved some of our puzzlers after only a few minutes or hours. To give more people a chance to play, we may wait between 24-48 hours before posting the answers we receive in the comment thread.

Good luck!

SMAP! Goes The Memory

April 7th, 2017 by Pola Lem

Scientists have long known that moisture content in the thin, top layers of soil plays an important role in global water processes. Recent findings published in Nature Geoscience show that roughly 14 percent of all rainfall remains in the uppermost soil layer for as long as three days after a storm. According to data from NASA’s Soil Moisture Active Passive mission (SMAP), that’s especially true for Earth’s driest regions.

Soil moisture varied widely in this image, which uses data gathered between May 27–31, 2015. Image by Joshua Stevens/NASA Earth Observatory.

“It’s sitting at a very critical zone at the surface of the land, and plays a disproportionately critical role in the cycling of water,” said Dara Entekhabi, a professor at MIT and author of the study, in a press release. “It plays a significant role in moderating climate on seasonal and annual timescales.”

The top 2 inches (5 centimeters) of surface soil contains a sort of “memory”—even several days after a heavy rainfall, the soil will contain a fraction of that moisture. Such memory can affect weather, farming, the spread of vector-borne diseases and the length of droughts and floods.

For more on SMAP, check out some of these NASA Earth Observatory stories:

+Soil Moisture in the United States
+Soggy Soil in the Eastern United States

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A Climate Model for the History Books

April 5th, 2017 by Adam Voiland

Decades or even centuries from now, when enough time has passed for historians to write definitive accounts of global warming and climate change, two names are likely to make it into history books: Syukuro Manabe and Richard Wetherald.

In the late-1960s, these two scientists from the Geophysical Fluid Dynamics Laboratory developed one of the very first climate models. In 1967, they published results showing that global temperatures would increase by 2.0 degrees Celsius (3.6 degrees Fahrenheit) if the carbon dioxide content of the atmosphere doubled.

The top map shows temperature changes in one of Manabe’s coupled atmosphere–ocean models. It depicts what would happen by the 70th year of a global warming experiment when atmospheric concentrations of carbon dioxide are doubled. The model’s predictions match closely with levels of warming observed in the real world. The lower image shows observed change from a 30-year base period around 1961–1990 and  1991–2015. The map was obtained using the historical surface temperature dataset HadCRUT4. Figure published in Stouffer & Manabe, 2017.

As Ethan Siegel pointed out in Forbes, carbon dioxide content has risen by roughly 50 percent since the pre-industrial era. Observed temperatures, meanwhile, have increased by 1°C (1.8°F). For a pair of scientists working in a time when computer instructions were compiled on printed punch cards and processing was thousands of times slower than today, they created a remarkably accurate model. That is not to say that Manabe claims his 1967 model is perfect. In fact, he is quick to point out that there are some aspects that his and other climate models still get wrong. In an interview with CarbonBrief, he put it this way:

Models have been very effective in predicting climate change, but have not been as effective in predicting its impact on ecosystem[s] and human society. The distinction between the two has not been stated clearly. For this reason, major effort should be made to monitor globally not only climate change, but also its impact on ecosystem[s] through remote sensing from satellites as well as in-situ observation.

There is a great deal of fascinating detail about Manabe and Wetherald’s model and the early history of climate modeling that do not fit into a short blog post. If you want to learn more, this section of Spencer Wirt’s the History of Global Warming is well worth the time. The American Institute of Physics has also posted a Q & A with Manabe that covers his 1967 paper, which is considered one of the most influential in climate science. And in March 2017, Manabe and colleague Ronald Stouffer authored a commentary that was published in Nature Climate Change. The Independent also has a good article about this.

This line plot shows yearly temperature anomalies from 1880 to 2014 as recorded by NASA, NOAA, the Japan Meteorological Agency, and the Met Office Hadley Centre (United Kingdom). Though there are minor variations from year to year, all four records show peaks and valleys in sync with each other. All show rapid warming in the past few decades, and all show the last decade as the warmest. Read more about this chart.