Readers were quick to name the Caspian Sea as the location featured in our April 2016 puzzler. It took just a bit longer to puzzle out what caused the curious lines that crisscross the image. Are they gouges on the seafloor produced by trawling? Or are they are related to the movement of marine animals? Those are good guesses, but it turns out that the real culprit is ice.

Ice’s impact on the area becomes evident when you look back in time. The puzzler image (top) was acquired in springtime, on April 16, 2016; it shows open water in the vicinity of the Caspian Sea’s Tyuleniy Archipelago. On January 17, 2016, (second image) the same area is covered with fragmented ice.

Ice cover in some areas is easily deformed, rising upward and downward into hummocks. The keels of these hummocks can extend down through the shallow water to the seafloor. As wind and currents push the ice around, the keels drag along the seafloor like a rake to produce the gouges. Read more about the phenomenon in our April 23, 2016, image of the day.



Go even farther back in time and you see that the phenomenon is not new. “These scratches were found on the aerial photographs as early as the fifties of the last century,” said Stanislav Ogorodov, a scientist at Lomonosov Moscow State University. “They were published in the Russian-language scientific literature and unambiguously interpreted as ice gouges.” The image above shows ice gouges photographed from aircraft in 1954 and is described in this 2015 paper.

A number of readers suspected early on that the gouge marks had icy origins. James Varghese and Rachel were the first to comment on the blog and correctly describe the location and phenomenon. On Facebook, Jaouhar Mosbahi was the first to post a correct description. And Rodney Forster contributed insight in a twitter conversation with @NASAOceans, where the image was first released.

Santiago Gassó: Following the Patagonian Dust Trail

April 21st, 2016 by Elizabeth Jarrell
Conversations with Goddard - Santiago Gasso

Santiago Gasso. (Credit: NASA/W.Hrybrk)

Earth Matters occasionally publishes interviews with earth scientists from around NASA. Here we feature Santiago Gassó, research associate at Goddard Space Flight Center in Maryland.

What is most interesting about your role at Goddard?
I am a physicist and work in atmospheric science, with a specialty in remote sensing. I use data from satellites to look at Earth’s atmosphere, and I focus on natural and manmade aerosols, which are very small particulate matter.

I am part of the science team for the Ozone Monitoring Instrument (OMI) on the Aura satellite. Launched in 2004, OMI is an instrument designed to survey pollutants such as sulfur dioxide or aerosols in the atmosphere. I am part of the team that develops algorithms based on this data.



These scanning electron microscope images (not at the same scale) show the wide variety of aerosol shapes. From left to right: volcanic ash, pollen, sea salt, and soot. (Micrographs courtesy USGS, UMBC (Chere Petty), and Arizona State University (Peter Buseck).) The top strip of photos shows desert dust, volatile organic compounds from vegetation, smoke from forest fires, and volcanic ash. All are natural sources of aerosols. (Photographs copyright (left to right) Western Sahara Project, Jonathan Jessup, Vox, and Ludie Cochrane.)

Where are you from?
I was born in Buenos Aires, a city as dense as New York. I got a master’s degree in physics from the University of Buenos Aires. Because I wanted to live abroad, I came to the U.S. to get a doctorate in geophysics, specializing in atmospheric sciences at the University of Washington. I came to NASA Goddard because I wanted to learn radiative transfer theory from the people who designed and created the satellites that I used for my Ph.D. thesis. Radiative transfer is the study of propagation of electromagnetic energy. It provides the framework and, most importantly, the equations that most satellite retrieval algorithms use.

What is your main scientific work?
My main objective is to use algorithms to determine how much radiation has been absorbed by atmospheric aerosols. The study of absorption by aerosols is important because it can change the temperature profile of the atmosphere. For example, a thick cloud of smoke can increase the ambient temperature by absorbing solar energy and returning that energy to the environment as heat.

What are some of your other scientific interests?
I also like to spend time looking at satellite images for phenomena that are overlooked. For example, I am very interested in dust from glaciers and other high-latitude deserts. Dust plumes coming off Greenland’s and Alaska’s coasts can be clearly seen in satellite images.


The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured this image of dust from the Copper River Delta being blown over the Gulf of Alaska on October 28, 2014. Read more here.

I am curious about measuring particulate mass concentration based on these images. The implication is that, unlike the more tropical sources of dust like the Sahara Desert, the high-latitude sources are near and upwind of ocean ecosystems with known deficiencies in certain nutrients. It is widely believed that the dust plumes are supplying nutrients, such as iron and phosphorous, that would otherwise not be available in these marine ecosystems. However, we have not yet proven this idea.

I am also beginning to work with astrobiologists to implement or adapt astrobiology remote sensing techniques to study aerosols in the Earth’s atmosphere. This is a new, exciting area for me.

What is your biggest discovery?
About 10 years ago, while looking at dust plumes coming off the Patagonia desert of South America, I ran into a very cloudy area with highly distinctive tracks in the clouds. It turns out that I discovered the equivalent of tracks of smoke from ship engines—except these tracks were generated by volcanoes. The tracks were formed in clouds moving over very weak volcanic eruptions. Rather than a full eruption, these traces are made from volcanic belches. When these aerosols reach the cloud deck above the volcano, they change the properties of the clouds slightly. Just like pollution entering a cloud, the volcanic aerosols induce a change in droplet size that results in a change in amount of radiation reflected by the cloud. This is change is what is detected by the satellite.

I found all this just by chasing dust from Patagonia. I just wanted to know how far this dust would go.


Clouds that form around volcanic emissions are made up of many small droplets instead of fewer larger droplets. Since these clouds present more surfaces for light to bounce off of, they are brighter than other marine clouds. Bright volcano clouds are similar to ship tracks, which from around sulfate aerosols in ship exhaust. The top image illustrates the impact of small-scale volcanic eruptions on clouds. The image was captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite on April 27, 2006. The lower image, calculated from the MODIS data, shows the average size of particles at the top of the clouds. Read more about the images here.

Please tell us about your field work in Patagonia.
I have been to Patagonia twice. Both times, I was working with a partner to install equipment that measures dust at the ground—the same dust that we see from space.

Patagonia is a desert in the southern end of Argentina. It is cold, dry, and sparsely populated. Patagonia lies next to a fantastic mountain range, the Andes, that is twice as tall as the Rockies.

How have your Patagonian studies evolved?
I was the first person to report observations from space of dust storms in Patagonia. I was the first one to study the entire transport of these dust storms using satellites and modeling tools.

 The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured this natural-color image on May 12. The dust blew out of the Patagonian Desert, and many of the plumes arose from sediments around a shallow lake.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured this natural-color image of dust blowing out of the Patagonian Desert.

This work put me in touch with a diverse group of scientists–including geochemists, paleoclimatologists, and geomorphologists–who are all interested in the presence and impact of dust at high latitudes. We formed a network called the High Latitude Dust and Climate Network, and we are hosting a symposiumin Iceland two years from now.

It is interesting to see how different scientists view time. The satellite data I use is based on many photos per minute. My time reference is very fast. In contrast, some of the paleoclimatologists, who drill cores into the ice, view tens of thousands of years in a single inch. They think in terms of thousands of years.

How did your training make you able to find things no one else sees?
This skill comes from my Ph.D. thesis on measuring how atmospheric particles capture water and grow to become cloud drops. I was one of my adviser’s first Ph.D. students, and he did not have much money to buy new equipment. So we had to use observations or data already analyzed by other groups. As a result, I was always getting leftover data that had already been mined. The easy things that one could say about them had already been discovered and reported. So I had to sharpen my skills to discover phenomena and effects that had been overlooked by others.

What motivates your scientific research?
I am always curious about understanding physical concepts and how different phenomena integrate. For example, I want to understand how dust interacts with ocean biology. Another example is how the ocean interacts with the atmosphere by supplying aerosols.

What else do you do to satisfy your curiosity?
I make it a point to attend seminars outside my field. Presently, I am very interested in planetary exploration, so I go to many lectures. It is super fun, and I learn things that I can apply to my own research. I also read papers from outside my field so that I can learn about other areas.

Why did you choose your profession?
I wanted to be a biologist. I became a physicist because it was easier for me to understand equations than to memorize facts. Mathematics makes sense to me.

Who is the most inspiring person you have worked with at Goddard?
One of my thesis advisers was the Yoram Kauffman. He was a very intelligent and generous scientist–brilliant actually. He was very good at inspiring and encouraging others to explore their instincts, to ask why and then find out the answer. Yoram is the one who inspired me to follow up on the volcano discovery. When I first showed him the faint traces, he was so excited that he said that he could see the image on the front page of Science magazine. Coming from him, that meant everything to me. Unfortunately, he died about two months later.

What do you do in your spare time?
On weekends, I spend most of my time with my wife and two kids. Every spare minute during the week, I get onto my laptop and look at new satellite images, much to my wife’s chagrin.

This piece was adapted from an article originally published by Goddard Space Flight Center. 

April Puzzler

April 18th, 2016 by Kathryn Hansen


Every month on Earth Matters, we offer a puzzling satellite image. The April 2016 puzzler is above. Your challenge is to use the comments section to tell us what part of the world we are looking at, when the image was acquired, what the image shows, 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, 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. In the credits, we’ll acknowledge the person who was first to correctly ID the image. We’ll also recognize people 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!

Update: The answer is posted here.


No, that is not a photograph of the death star orbiting Earth. It is the winner of NASA Earth Observatory’s 2016 Tournament Earth—the Dark Side and the Bright Side. The image shows the fully illuminated far side of the Moon that is not visible from Earth.

The images were acquired by the Earth Polychromatic Imaging Camera (EPIC) on the DSCOVR satellite, which orbits about 1.6 million kilometers (1 million miles) from Earth. EPIC maintains a constant view of the fully illuminated Earth as it rotates. About twice a year the camera captures images of the Moon and Earth together as the orbit of DSCOVR crosses the orbital plane of the Moon.

Screen Shot 2016-04-04 at 4.45.40 PM

The Moon faced some stiff competition on its journey to the championship. In the course of the tournament, it faced a trio of hurricanes over the Pacific, the electric eye of Cyclone Bansi, an underwater volcano, and the wrath of Mount St. Helens. The final round came down to a slugfest between the Moon and an impressionistic bloom in the Baltic Sea caused by a profusion of cyanobacteria. When the voting was over, the Dark Side/Bright Side finished with 59 percent of the vote.

While we aren’t aware of any homecoming parades to honor the 2016 champion, watching the video above (or listening to all of Pink Floyd’s Dark Side of the Moon) seems like a fitting way to celebrate. The images in the movie below were taken over the course of five hours on July 16, 2015. The North Pole is toward the upper left, reflecting the orbital tilt of Earth from the vantage point of the spacecraft. The far side of the Moon was first observed in 1959, when the Soviet Luna 3 spacecraft returned the first images. Since then, several missions by NASA and other space agencies have imaged the lunar far side.



This month we posed a special seasonal challenge: We asked you to join us for a remote-sensing-themed egg hunt by identifying colorful, oval-shaped lakes and ponds around the planet. Well, as one reader points out, we “asked for it.” Hueva identified a lake in Canada so egg-like that it actually goes by the name “Egg Lake.” And to top it off, Goose Lake is immediately to its north.

The traditional challenge—identify the feature in this satellite image and its location—sent some on a wild goose chase. That’s due, in part, to the fact that there’s certainly more than one way to form an egg-shaped lake. As Viacheslav Zgonnik noted:

“These places are seepages of natural molecular hydrogen (H2). We tested many of them on different continents. Check our the most recent article about Carolina bays – egg-like structures in North Carolina, USA.”

The March puzzler was also puzzling because this lake shape is not unusual—oval lakes show up all over the planet. Michael G commented on the blog:

“Located in northern Alaska, USA. There are hundreds of such lakes, they are increasing in size and number. They are thought to form as a result of climate change (warming) that is especially noticeable in the arctic. The shape of the lakes appear to all orient themselves in the direction of permafrost thawing but the dynamics of this are unknown. Recent theories includes slumping of the permafrost as is thaws through the entire thickness of the layer, instead of just the upper layer. The lakes are among the fastest growing lakes on record, increasing in a linear (hence egg shape) direction at about 3m a year, towards the northeast.”

Excellent guesses! This particular image, however, shows a series of saline lakes in Western Australia. Congratulations to David E. Ways and Owen Earley, who were the first to post correct guesses to the blog and to Facebook, respectively. Paulie also guessed correctly, adding that “this area is a “biodiversity hotspot, mixed in with established intensive agriculture.”

The false-color puzzler image was acquired on October 21, 2015, with the Operational Land Imager (OLI) on Landsat 8. To see what the scene looks like in natural-color, and to learn more about these lakes and the reason behind their various colors, read our March 26, 2016, Image of the Day.

The identity of our puzzler has been revealed, but there’s still time to hunt eggs. Continue sending us the latitude and longitude of your favorite colorful, egg-shaped lake by submitting it as a comment on this blog post. We will include the most interesting lakes sent in by readers in a special image gallery that we will publish later this spring.


NASA’s Earth Observatory brings you a new view of Earth from above every single day. Many of these images are more than just pretty pictures; scientists use satellite-based information to figure out how the planet works and to better understand how and why it is changing on a global scale. But to get a full picture, the view from space isn’t enough. You also need granular observations that can only be gathered from the ground. And that’s the job of many NASA researchers who embark on expeditions each year, traversing land, air, ice, and sea.

NASA has a long history of field campaigns large and small. But 2016 is a particularly busy year as eight major new campaigns get under way. If you like acronyms, you’ll love this list:

  • Oceans Melting Greenland (OMG)
  • Korea U.S.-Air Quality (KORUS-AQ)
  • North Atlantic Aerosols and Marine Ecosystems Study (NAAMES)
  • Arctic Boreal Vulnerability Experiment (ABoVE)
  • COral Reef Airborne Laboratory (CORAL)
  • Atmospheric Tomography (ATom)
  • Atmospheric Carbon and Transport – America (ACT-America)
  • Observations of Clouds above Aerosols and their Interactions (ORACLES)

Watch the video below for an armchair tour and brief explanation of each campaign.

So what on Earth is OMG? Scientists are now in the field to help get to the bottom of sea level rise. Namely, how much is ocean warming contributing to ice loss from below, where glaciers meet the water? Data collected during flights around the island’s perimeter will help find out. Read more about the OMG campaign here, and follow writers in the field with each campaign here.

Also currently under way is the Arctic Boreal Vulnerability Experiment (ABoVE). This campaign covers 2.5 million square miles of tundra, mountains, permafrost, lakes, and forests in Alaska and Northwestern Canada. Scientists use satellites and aircraft study this formidable terrain as it changes in a warming climate. But remote sensing by itself is not enough to understand the whole picture, so teams of researchers are on location to gather more data. Follow their journey here, as told directly by scientists in the field.

Stay tuned as the rest of the campaigns ramp up. It’s been an icy adventure so far. But later this year, scientists with CORAL will assess the condition of threatened coral-based ecosystems in Hawaii, and scientists with KORUS-AQ will study air quality in South Korea. If you want to learn more about those campaigns now, take a look at the story we published about CORAL  or the story we did about KORUS-AQ in March.


Every month on Earth Matters, we offer a puzzling satellite image and ask you to tell us what part of the world we are looking at, when the image was acquired, what the image shows, and why the scene is interesting.

However, this March we have a special challenge with a seasonal theme (at least in the Northern Hemisphere, where spring has sprung). Join us for a remote-sensing-themed egg hunt. And by “eggs,” we mean colorful, oval-shaped lakes and ponds somewhat like those pictured above.

The first part of the challenge is to guess the location of the lakes in the image above, just like we do with our puzzler images most months. The second part is to find other colorful egg-like lakes that you think we’ll like.

When you find a good candidate, send us a screenshot and the latitude and longitude of the lake by submitting it as a comment on this blog post. We will include the most interesting lakes sent in by readers in a special image gallery that we will publish later this spring.

Some other guidance and suggestions:

+Search tools. You can use any tools you like to search for colorful lakes. Google Maps, Worldview, Visible Earth, the Earth Observatory archives, and the Gateway to Astronaut Photography may be useful.

+Make sure your lakes are reasonably large. We’ll be using Landsat (30 meters per pixel) or MODIS (250 meters per pixel) data to make the final images. If you have to zoom all the way in on Goggle Maps to see your lake, you are viewing commercial satellite imagery that has a resolution of a few meters per pixels or less. Lakes should have diameters of at least a few hundred meters to show up well in Landsat imagery.

+The more unusual the color, the better. Submitting a lake with a “normal” color is fine, but it will have a smaller chance of making the cut for our final gallery.

+Earth, please. Our focus will be on lakes on Earth. You are more than welcome to share egg-like features you spot on other planets with us, but they won’t make our final gallery.

+It’s a #SpaceEggHunt. Tag your social media posts about this with #SpaceEggHunt. In addition to the blog, we’ll monitor that hashtag for submissions.

+Explain the color. Tell us why you think the lake has such an unusual color as part of your comment. While part of the goal here is to have fun and hunt for lake eggs to celebrate spring, the final gallery will delve more deeply into the science behind lake color and how that can be useful for scientists.

+The prize. We can’t offer prize money, 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. If you find makes the final gallery, your name will be mentioned.

 Good luck and happy hunting!

February Puzzler Answer: Deforestation in Argentina

March 20th, 2016 by Adam Voiland


It took Gavin McMorrow a mere 30 minutes to solve our February puzzler. As he pointed out, the rectangular patterns were cleared forest areas in Argentina’s Salta province. (Learn more about the area in our February 27, 2016, Image of the Day). McMorrow even recognized this was an Operational Land Imager (OLI) image from Landsat 8. Nicely done, Gavin.

It turns out he is no newcomer to space geography quizzes. In fact, if you follow him on Twitter or Instagram, you’ll find McMorrow is actually somewhat of a space geography connoisseur. McMorrow participated regularly in the #SpaceGeo and #EarthArt quizzes that astronaut Scott Kelly organized while he was on the International Space Station.

He’s also been helping Center of Geographic Sciences geographer Dave MacLean (@DaveAtCOGS) catalog the locations of the photographs that astronauts on the station tweet out from orbit. In some cases, astronauts aren’t sure of the feature they just photographed, and it takes time for all the images to be archived in the official database.

To see what I mean, check out MacLean’s map of Scott Kelly’s Year in Space. You can even choose to see maps for just the tweets tagged as #SpaceGeo or #EarthArt. Also helpful, MacLean (and helpers like McMorrow) track down high-resolution versions of the photos when they can. In the tweet below, for instance, McMorrow is alerting astronaut Tim Peake that an image of snow-covered mountains that Peake tweeted was a shot of mountains in Glacier National Park.

And, oh yes, in his spare time, McMorrow is solving Planet Labs geo-detective quizzes.

For a guy who enjoys space geography this much, should I mention we have a job opening?

Ground Photos: Sand Mining at Poyang Lake

March 17th, 2016 by Adam Voiland

Our March 17, 2016, Image of the Day offered a satellite perspective on how sand mining has changed the coastline of Poyang Lake, the largest freshwater lake in China.  The photographs below provide a view of sand mining from the ground. James Burnham, an ecologist with the University of Wisconsin and the International Crane Foundation, took the photos while conducting field research on wintering waterbirds at Poyang Lake. “Sand mining has compromised the ecological integrity of the lake by contributing to less predictable seasonal water fluctuations and to a series of recent low water events,” he said. “This is a lake that hosts 98 percent of the endangered Siberian Cranes and Oriental White Storks, as well as a significant number of over a dozen other endangered waterbirds in the winter.”


Barges full of sand. Photo Credit: James Burnham, University of Wisconsin/International Crane Foundation.


Sand dredging boat. Photo Credit: James Burnham, University of Wisconsin/International Crane Foundation.

Siberian Crane unison call at Mei Xi Hu in Poyang Lake Nature Reserve. Photo Credit: James Burnham, University of Wisconsin/International Crane Foundation.

Siberian Crane family group at Mei Xi Hu, PLNR

Siberian Crane family group at Mei Xi Hu in the Poyang Lake Nature Reserve. Photo Credit: James Burnham, University of Wisconsin/International Crane Foundation.

Happy Anniversary, GRACE!

March 17th, 2016 by Adam Voiland and Holli Riebeek

Fourteen years ago, a rocket launched a pair of satellites known as the Gravity Recovery and Climate Experiment (GRACE) from the Plesetsk Cosmodrome in Russia. Though just 487 kilograms (1,074 pounds) each, the satellites have produced out-sized scientific advances. As we noted in 2012, few hydrologists believed the satellites would be able to detect—no less measure—changes in groundwater when they launched. As the map below shows, scientists working with GRACE data have shown otherwise.


This map shows how water supplies have changed between 2003 and 2012. GRACE measures subtle shifts in gravity from month to month. Variations in land topography or ocean tides change the distribution of Earth’s mass; the addition or subtraction of water also changes the gravity field. During that period, groundwater supplies decreased in California’s Central Valley and in the Southern High Plains (Texas and Oklahoma)—places that rely on ground water to irrigate crops. Eastern Texas, Alabama, and the Mid-Atlantic states also saw a decrease in ground water supplies because of long-term drought. The flood-prone Upper Missouri basin, on the other hand, stored more water over the decade.

GRACE has observed a number of significant changes in the water cycle. For instance, the mission revealed losses in ice mass on Greenland (where the loss is dramatic), Alaska, and Antarctica. The gravity measurements revealed how much the melting glaciers are contributing to sea level rise by recording both ice lost from land and the mass gained in the ocean. The image below shows changes in the Antarctic ice sheet between 2003 and 2010 as measured by GRACE.


GRACE measured changes in the Antarctic ice sheet from December 2003 through 2010. Red areas lost mass, while blue regions gained mass. (NASA map adapted from Luthke et al., 2012.)

As seen in the set of maps below, GRACE-based measurements can also be combined with ground-based measurements to map water at the surface, in the root zone, and as groundwater.


These maps compare conditions during the week of August 20, 2012, to the long-term average from 1948 to the present. For example, dark red regions represent dry conditions that should occur only 2 percent of the time (once every 50 years).

Thank you, GRACE! Here’s to many more years of observations. You can learn more about the mission here. Launch and clean room photos available here.