Earth Matters

According to a new report from the World Meteorological Organization, seasonal weather conditions have not yet played a large role in influencing the spread of the virus that causes COVID-19. Government interventions and human behavior have been much more influential, according to the group of experts in Earth science, medical sciences, and public health.

“We saw waves of infection rise in warm seasons and warm regions in the first year of the pandemic, and there is no evidence that this couldn’t happen again in the coming year,” said Ben Zaitchik, the co-chair of the World Meteorological Organization team and a Johns Hopkins University earth scientist. At the start of the pandemic, there was some speculation that seasonal weather could influence the spread of COVID-19, with the virus spreading more readily in cooler, drier weather and spreading less in warmer, wetter seasons. “At this stage, evidence does not support the use of meteorological and air quality factors as a basis for governments to relax their interventions aimed at reducing transmission.”

NASA Earth Observatory image by Joshua Stevens, using Blue Marble data.

Zaitchik also leads a NASA-funded team assessing the same topic. As we reported in August, that team is using weather reanalysis models and various statistical techniques to look for signals in satellite data and other sources of environmental data. Their goal is to detect potential relationships between environmental conditions (such as temperature, humidity, ultraviolet light, and rainfall) and the spread and severity of COVID-19.

Zaitchik recently published an article in Nature Communications that urges the research community to strive for rigor in designing studies on COVID-19 seasonality and for clarity in communicating findings so as to avoid confusing the public and policymakers with conflicting results. We checked in with Ben in March 2021 for an update on his research as COVID-19 cases were dropping in the United States and other countries.

Earth Observatory: The number of COVID-19 cases has been on quite a roller-coaster ride this year. What are the main drivers of the ups and downs in infection rates?

Zaitchik: It is pretty clear that the primary driver is still human behavior. When we stay home and stay socially distant, there is less transmission. That explains the biggest swings we’ve seen in the case curve in the United States and in other countries. As we see vaccines roll out in some countries, along with accumulating infections, we are likely also seeing the beginnings of herd immunity playing a role.

Some examples of the proposed mechanisms for how meteorological and air quality factors may affect the COVID-19 (SARS-CoV-2) virus. Credit: World Meteorological Organization

EO: We saw a surge of cases in the United States in the early part of winter and then a drop in February. Is that related to the weather?

Zaitchik: There are direct ways that weather might affect virus survival or our immune systems, but the most important effect now is indirect. If weather conditions make it easy for people to stay outside and to avoid crowding, then it is possible the weather can reduce transmission rates; vice versa if people are crowding indoors. That understanding is based on our experience with other upper respiratory viruses; on studies that show the potency of transmission in crowded indoor environments; and to some extent statistical analyses of patterns we have seen in the first year of COVID-19. But that last line of evidence still requires investigation. While the number of cases can sometimes align with seasonal patterns, that is not always the case. It does appear that weather conditions can reinforce case trends, but the impact of weather is still highly uncertain.

EO: Is it fair to say that how people behave in cooler, drier seasonal conditions is probably more important than how the virus reacts to the environment?

Zaitchik: It does appear that virus sensitivities exist. Coronaviruses are less stable at higher temperatures, when exposed to intense sunlight, and under certain humidity conditions. It is just not clear yet whether those sensitivities have mattered appreciably for transmission of COVID-19 so far. In general, those sensitivities suggest there are better chances for the virus to survive and thrive under wintertime conditions, leading to greater transmission potential. But in the end, the main driver of the spread is human behavior.

(NASA Earth Observatory animation by Joshua Stevens, using GEOS-5 data from the Global Modeling and Assimilation Office at NASA GSFC.)

EO: How is your NASA-funded research project on COVID-19 seasonality going? Do you have any results yet?

Zaitchik: We have made a lot of progress on data integration and alignment, which has allowed us to release a consistent and quality-controlled database of COVID cases and hydrometeorological variables that is available to the public via GitHub. We think this is really important for studies of weather and COVID-19 since so many studies have suffered from questionable data or have been unrepeatable. We’ve also begun to understand why there were so many conflicting results in early publications on COVID’s weather sensitivity, and how the contribution of human movement to predictability of transmission rate has changed over time.

EO: How has your thinking changed about the potential seasonality of COVID-19 since the beginning of the pandemic?

Zaitchik: It hasn’t really changed much. Going into this, epidemiologists anticipated that we might see something like a cold weather peak in transmission just because so many other upper respiratory viruses do that. But we also knew that our instincts on seasonality come from endemic diseases like influenza, and that there is plenty of evidence from previous epidemics that viruses can spread even when the weather is unfavorable. That we are seeing some evidence of seasonality — but with lots of unexplained variability — is reasonably consistent with what epidemiologists expected.

Particles of SARS-CoV-2 virus particles on a dying cell. Image credit: NIAID.

EO: Americans are most familiar with how the pandemic has progressed in this country, while satellites excel at showing a global perspective. What are you seeing and learning from global data?

Zaitchik: The global perspective is really important. From a weather and COVID-19 perspective, we have seen interesting hemispheric patterns. For instance, there is some evidence that Southern Hemisphere countries experienced a peak in their winter, while Northern Hemisphere cases rose as our winter settled in. But there are also exceptions to that pattern, like the summertime peak in the US or the consistently low case counts in east Asian countries. Looking at the environment across countries and climate zones, we see a complicated, multi-scale set of patterns that we need to decipher. The global perspective is powerful because it has the potential to yield some general insights. It is also powerful because it can correct some too-simple narratives that have emerged from looking at one country at a time.

It is that time of year again…Tournament Earth is back! This time, the theme is astronaut photography. For more than 20 years, astronauts have been shooting stunning photos of Earth from the International Space Station that highlight the planet’s beauty, complexity, and vulnerabilities.

So which are the most unforgettable photographs of Earth taken from the space station? Over the next five weeks (March 8-April 13), you can help decide.

The first round has already begun. Cast your vote here:

While you wait for the Round 1 results, download the bracket here and challenge your friends. After you fill out that bracket, post your predictions in the comment thread for which four photos will make the semifinals and which one will be crowned champion. We can’t offer prize money or a trip to the Moon, but bragging rights are forever if you can guess the eventual champion.

Also, bookmark this space. We will provide updates later in the tournament and highlight some of your predictions, commentary, and insights lower in the post. Just remember to use the hashtag #TournamentEarth and tag @NASAEarth on social media (we’re on Twitter, Facebook and Instagram) or we might not see your post.

If you are curious about the team behind the photos you see in Tournament Earth, check out our Picturing Earth video series.

Happy voting!

What a Lake in Turkey Can Tell Us about Mars

February 17th, 2021 by Kasha Patel

Underwater microbialites on the eastern edge of Lake Salda. Photo credit: Bradley Garczynski

On February 18, 2021, the Perseverance rover is scheduled to make a historic landing in Jezero Crater on Mars. The rover will survey the area and collect rock samples to send back to Earth. Even though no human has set foot inside the crater, researchers have some ideas of what to expect thanks to a similar landscape on Earth: Lake Salda.

You might not think a lake in southwestern Turkey has much in common with an impact crater on Mars, but the two basins contain similar mineralogy and geology. In fact, Lake Salda is the only known lake on Earth that contains carbonate minerals and depositional features (deltas) similar to those found at Jezero Crater, which is thought to have once contained a lake.

Lake Salda in 2020 (left) and Jezero Crater in 2017 (right). Photo credit: NASA

Briony Horgan, a planetary scientist at Purdue University and member of the Perseverance science team, and colleagues from the Istanbul Technical University traveled to Lake Salda in the summer of 2019 to study the shorelines and surrounding area. They aimed to get a better understanding of the microbial and geological processes at Lake Salda to help guide the search for life at Jezero.

Below are photographs taken by Horgan’s graduate student Bradley Garczynski at Lake Salda showing some features that the Perseverance team hopes to find at Jezero Crater.

Variety of Rocks

The shoreline and surrounding bedrock around Lake Salda contain sediments of different origins. The photo below shows beach sediments along the northeastern edge of the lake.

Northeastern shore of Lake Salda. Photo credit: Bradley Garczynski

The darker-toned sediments were eroded from the steep exposures of the surrounding bedrock. The light-toned sediments are made up of the carbonate mineral hydromagnesite. You can also see the shallow carbonate bench (one to two meters thick) that extends about 40 meters offshore before steeply dropping off to deeper water.

Using data from NASA’s Mars Reconnaissance Orbiter, researchers detected a mixture of watershed minerals and possibly carbonate along the western margins of Jezero Crater, which scientists believe to be the shoreline of an ancient lake. Horgan and colleagues are interested to learn if these deposits are similar to those at Lake Salda.


Researchers are especially interested in the lighter sediments around Lake Salda because they could help inform the search for biosignatures — evidence of past or present life — at Jezero Crater.

The hydromagnesite sediments around Lake Salda are thought to have eroded from large mounds called “microbialites”—rocks formed with the help of microbes. Hydromagnesite sediments may be similar to carbonate minerals detected at Jezero. The photo below shows an exposed island made up of large mounds of old microbialites at Lake Salda.

Exposed island of old microbialites at Lake Salda. Photo credit: Bradley Garczynski

These structures themselves are good indicators that microbes were once active, so researchers will be looking for signs of these in rocks at the Martian crater.

The images below show an older microbialite at Lake Salda that grew on the surface of a rock along the shore of an alluvial fan delta (left) and an underwater image of a modern microbialite at around one meter deep (right). The yellow-green film on the surface is made up of microbial communities that aid in the precipitation of hydromagnesite.

Older microbialite (left) and modern microbialite (right). Photo credit: Bradley Garczynski

Rock deposits in deltas

The delta near Jezero Crater adds to the evidence that it once contained a lake. Similarly, Lake Salda contains alluvial fans full of rock deposits eroded and washed down from the surrounding bedrock (shown below). By studying how stones settled in Lake Salda’s alluvial fans, the team can learn more about the depositional processes at Jezero.

Alluvial fan at Lake Salda. Photo credit: Bradley Garczynski

The image below shows an outcrop of sediment deposited by an ancient stream when the water levels were much higher around Lake Salda. The different layers represent different periods of deposition and include various grain types and sizes. The Perseverance rover will look for similar deposits at Jezero to learn more about its geologic history.

Outcrop of sediments at Lake Salda. Photo credit: Bradley Garczynski

The image below shows a terrace deposit on the southwest peninsula of the lake.

Terrace deposits at Lake Salda. Photo credit: Bradley Garczynski

Groundwater seeps

Groundwater springs at Lake Salda (shown below) play an important role in altering the lake chemistry and influencing the environment for microbes.

Groundwater spring on the southwest peninsula of Lake Salda. Photo credit: Bradley Garczynski

The image below shows a mud-dominated shoreline on the northeastern edge of Lake Salda. The mud is likely due to a nearby groundwater seep. The darker features just offshore are modern microbialites actively accreting in this muddy embayment.

It is unknown what role groundwater may have played at Jezero. Studying analog environments like Lake Salda helps provide researchers better context while looking for evidence of past groundwater at Jezero and further advance the search for potential biosignatures.

Muddy shoreline in northeastern Lake Salda. Photo credit: Bradley Garczynski

With these observations from Lake Salda, Horgan and her colleagues have been able to better focus their research questions. If microbes existed in the ancient Jezero lake, where did they live and build microbial structures? Where are the best places to search for past evidence of them: near groundwater springs? Near the delta? Or farther away in quiescent shorelines or muddy embayment?

The quest to answer these questions begins this month. Watch the Perseverance landing on February 18, 2021, at 11:15 a.m. PST / 2:15 p.m. EST live here.

Read more about the similarities between Lake Salda and Jezero Crater here.

Special thanks to Bradley Garczynski for helping provide the image descriptions.

EO February 2021 Puzzler

February 16th, 2021 by Andi Brinn Thomas
EO’s February 2021 Puzzler

Every month on Earth Matters, we offer a puzzling satellite image. The February 2021 puzzler is above. Your challenge is to use the comments section to tell us what we are looking at, where it is, and why it is interesting.

How to answer. You can use a few words or several paragraphs. You might simply tell us the location, 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 feature. If you think something is interesting or noteworthy, tell us about it.

The prize. We cannot offer prize money or a trip to Mars, but we can promise you credit and glory. Well, maybe just credit. A few days 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 first person to correctly identify the image at the bottom of this blog post. We also may recognize readers who offer the most interesting tidbits of information about the geological, meteorological, or human processes that have shaped the landscape. Please include your preferred name or alias with your comment. If you work for or attend an institution that you would like to recognize, please mention that as well.

Recent winners. If you’ve won the puzzler in the past few months, or if you work in geospatial imaging, please hold your answer for at least a day to give less experienced readers a chance.

Releasing Comments. Savvy readers have solved some puzzlers after a few minutes. To give more people a chance, we may wait 24 to 48 hours before posting comments. Good luck!

A Checkup for Carbon

February 11th, 2021 by Adam Voiland

Every year, a group of scientists affiliated with the Global Carbon Project give Earth something like an annual checkup. Among the key questions they address: how much carbon is stored in the atmosphere, the ocean, and the land? And how much of that carbon has moved from one reservoir to another through fossil fuel burning, deforestation, reforestation, and uptake by the ocean each year?

All of the latest findings—including the data for 2020, a year like few others—are available here, including links to dozens of interesting charts and a peer-reviewed science paper. Ben Poulter, a NASA scientist and member of the Global Carbon Project team, summarized the findings this way: “The economic effects of COVID-19 caused fossil fuel emissions to decrease by 7 percent in 2020, but we continued to see atmospheric CO2 concentrations increase, by 2.5 ppm, or about 5.3 PgC. This means that the remaining carbon budget to avoid 1.5 or 2 degrees warming continues to shrink, and that we need to continue to monitor the land, ocean, and atmosphere to understand where fossil fuel CO2 ends up.”

Below are 10 key findings from the most recent report. (Note: the Global Carbon Project team synthesizes a broad range of data, some of which requires time-consuming processing, quality-control, and analysis. While they do report some 2020 numbers, the most recent full year of data available for others is 2019.)

  1. Due to COVID-19 economic impacts, global fossil CO2 emissions declined by approximately 2.4 billion metric tons in 2020, a record drop. Fossil CO2 emissions declined by 11 percent in the European Union, by 12 percent in the United States, by 9 percent in India, and 2 percent in China.

  2. The global atmospheric CO2 concentration rose by 2.5 parts per million (ppm) in 2020 to reach 412 ppm averaged over the year. That puts it 48 percent above pre-industrial levels, 16 percent above 1990 levels, and 3 percent above 2015 levels.

  3. The growth rate in atmospheric CO2 concentration in 2020 was near the 2019 growth rate, despite slightly lower anthropogenic emissions.

  4. The land and oceans combined to absorb more than half of the CO2 emitted to the atmosphere (54 percent in 2020). While this can slow global warming, it leads to ocean acidification.

  5. Total CO2 emissions from human activities (fossil CO2 burning and land-use change) were around 40 billion metric tons in 2020. That compares to 43 billion tons in 2019.

  6. The growth of forests on abandoned farmland removed nearly 11 billion metric tons of CO2 in 2020. However, deforestation caused the equivalent of 16 billion tons of CO2 emissions.

  7. Land-use change emissions rose in 2020, predominantly in tropical regions. These emissions came from several areas, particularly Latin America, Sub-Saharan Africa, and Southeast Asia.

  8. Many economic sectors that produce fossil fuel carbon emissions returned to pre-COVID levels by the end of 2020, including the residential and power sectors. One exception was ground transportation, where declines persisted throughout 2020.

  9. Countries have a broad range of per capita emissions reflecting their national circumstances. The United States has the highest per capita emissions.

  10. Five years since the adoption of the Paris Agreement, growth in global fossil CO2 emissions have begun to falter. For the decade prior to 2020 (2010-2019), fossil CO2 emissions were decreasing significantly in 24 countries with growing economies.

The Global Carbon Budget is produced by more than 80 researchers working from universities and research institutions in 15 countries. Observations from several NASA satellites, sensors, aircraft, and models were among the sources of information used to formulate the 2020 budget. Sources of information supported by NASA included: the MODIS sensors on Aqua and Terra satellites, the Global Fire Emissions Database (GFED), the LPJ land surface carbon exchange model, Landsat, the LUHv2 land-cover change model, the CASA land surface carbon exchange model, ODIAC fossil fuel emissions data, the MERRA-2 reanalysis, the Cooperative Global Atmospheric Data Integration Project, and OCO-2.

Help Us Choose the Best Photos

February 6th, 2021 by Mike Carlowicz

For more than 20 years, astronauts have been shooting photographs of Earth from the International Space Station. Before that, they looked down from Mercury, Gemini, Apollo, Skylab, the Space Shuttles, and MIR. They have brought us unique views of our home planet in all of its wonder, beauty, and ferocity. They have also made some interesting and timely science observations along the way.

More than 1,000 of those photos have been published here on NASA Earth Observatory. We would like you to help us choose the best in our archives. In early March, we will launch Tournament Earth: Astronaut Photography, and we want you to be part of the selection committee.

From now through February 19, 2021, search our archives and point out the best photos shot by the astronauts. Post the URLs of your favorite photos in the comments section below.

Please choose images from these collections:

EO Astronaut Photography Collection

Visible Earth: Astronaut Photography

Please note that there are 30+ pages of images to scroll through — an internet rabbit hole of incredible beauty.

In March 2021, we will include some of your selections in Tournament Earth, a head-to-head contest to vote for the best of the best from our archives. Each week, readers will pick from pairs of images as we narrow down the field from 32 nominees to one champion. The Tournament Earth champion will be announced in early April.

So get browsing and get choosing. Then post your favorite URLs in the comments section by February 19.

If you want to learn more about how and why astronauts shoot photos of our planet — and the special training involved — check out our video series “Picturing Earth.”
Astronaut Photography in Focus

Window on the World

Behind the Scenes

What in the World Are Moon Trees?

February 2nd, 2021 by Brian Campbell, NASA Wallops and GLOBE

Trees connect us scientifically, environmentally, and culturally. We all know that trees are vital to our planet’s health. As trees grow, they absorb carbon from the atmosphere, playing a vital role in Earth’s global carbon cycle and helping to regulate Earth’s carbon budget.

But before you read any further, look around…especially if you are outside. Most of you can look in any direction and see a tree. You might wonder about a few things like: “What type of tree is that?” or “Why is that tree so tall or short?” or “How old is that tree?” or even “Was that tree planted by someone, or did the wind blow a seed to where the tree is now standing?”

Or what if you don’t see any trees? What does that signify about the environment? Did nature make it that way, or did humans? All of these are great questions that can help us understand and connect with the environment.

A Moon Tree that stood outside of Kennedy Space Center.

A few trees on Earth also connect us to the Moon. Have you ever heard of “Moon Trees?”

“Moon Trees” never actually grew on the Moon, but their seeds were taken into lunar orbit 50 years ago this week. The NASA Moon Trees history website explains:

Apollo 14 launched in the late afternoon of January 31, 1971, on what was to be our third trip to the lunar surface. Five days later, Alan Shepard and Edgar Mitchell walked on the Moon while Stuart Roosa, a former U.S. Forest Service smoke jumper, orbited above in the command module. Packed in small containers in Roosa’s personal kit were hundreds of tree seeds, part of a joint NASA/USFS project. Upon return to Earth, the seeds were germinated by the Forest Service. Known as the “Moon Trees,” the resulting seedlings were planted throughout the United States (often as part of the nation’s bicentennial in 1976) and the world. They stand as a tribute to astronaut Roosa and the Apollo program.

The logo for the NASA/U.S. Forest Service Moon Tree program.

Among the Moon Trees that were eventually planted around the United States and the world were sycamores, Loblolly pines, redwoods, sweetgums, and Douglas firs. Though it is unlikely the Moon Tree seeds were changed much by their brief lunar orbit, it is still a wonder that they made it into space and back, and that many of the trees are growing and thriving today.

So, where can you find them? The NASA Moon Trees site has a list, and there is also an article and photographs from our friends at National Geographic. UC Davis data scientist Michele M. Tobias created the map below. You can also learn more about the trees from our colleagues at Marshall Space Flight Center.

Map copyright Dr. Michele M. Tobias.

Perhaps you might see some Moon Trees in person in the next year or two. If you do, consider making tree height observations using the tree tools on the NASA GLOBE Observer app. When completing your observation, let us know in the app.

Have you ever visited and seen a Moon Tree? Tell us about it below.

The Marvels of Banks Island

January 27th, 2021 by Kathryn Hansen/NASA Earth Observatory, and Robie Macdonald/University of Manitoba/Dept. of Fisheries and Oceans

On July 18, 2015, the Operational Land Imager (OLI) on Landsat 8 acquired this natural-color image of Banks Island. 

In a typical year, perhaps a dozen people visit Auluvik National Park in Canada’s Northwest Territories. Luckily, one of those visitors brought back some outstanding photos.  

In November 2020, we highlighted a few compelling features around the Thomsen River estuary on Banks Island, including lines of sea ice tracing the shoreline and the braided pattern of the river. But there’s so much more to explore across this remote lowland tundra and river valley. 

Robie Macdonald, a scientist at the University of Manitoba, shared some photos that he shot while doing fieldwork in the region between 2014 and 2016. The purpose of that project, led by Matt Alkire of the University of Washington, was to collect geochemical measurements from small rivers across the Canadian Arctic Archipelago. 

“I really do love working in these places,” Macdonald said. “Once the aircraft has landed, one is bathed in a tremendous silence broken only by waves breaking on shingle. Then you have this incredible tundra spreading out toward the hills that define the river floodplain.” 

Here are ten of Macdonald’s favorite photographs.  

1. Ponds and Oxbows

“Numerous ponds of all sizes populate the drainage basins of Banks Island, and you can see several clusters of them in the satellite image (top), especially along the small river to the west of the Thomsen. This photograph provides a closer look at one such pond cluster. In the image, you can also see textbook oxbows, which have become the setting for more ponds.”

2. Permafrost Polygons

“During breeding season, it seems like almost every pond on Banks Island has its own population of snow geese (visible in this photo). You can also see old permafrost polygons that are now submerged within the pond. Polygons are widespread features of the permafrost in soil-rich locations and are produced over time by freeze-thaw cycles of the surface active layer. Permafrost thaw is widely impacting these regions, leading to feedbacks in the carbon system (CO2, CH4).”

3. Vibrant Vegetation

Photo by Robie Macdonald/University of Manitoba

“Perhaps the most surprising characteristic of the valley bottoms in this ‘Arctic desert’ is the vibrant color of the vegetation: yellows, greens, and reds mark a dense ground cover that can be seen on the satellite image as areas with a yellowish-brownish cast.”

4. Sediment Ripples

“As a result of the strong sediment supply, the large embayment at the Thomsen River mouth has been practically filled with sediment. The shallow water reveals itself in the satellite image by the lighter-greenish tone compared to water out in the channel north of Banks Island.  More evidence of the ample sediment supply can be seen in beautiful displays of sand/silt ripples in the lower river between the islands. In the satellite image (top), the ripples are almost visible as grey zones between the islands before the river enters the open bay.”

5. Ice Shoves

“When walking on these islands near the river mouth, you can see evidence of bank erosion and ‘ice shoves.’ These are produced when wind forces newly formed ice to ride up over the river bank and gouge out the top layer of the silty material that makes up these islands.  Unfortunately, ice shoves are too small to show on the satellite image.” 

6. Vulnerable Permafrost

“Global warming and the extensive loss of sea-ice cover in late summer have helped accelerate coastal erosion and permafrost slumping. This image shows a section of coastline just to the east of the Thomsen River mouth that consists of a lot of frozen ice. This sort of permafrost is especially vulnerable to the changing temperature regime.” 

7. Erosion and Slumping

Photo by Robie Macdonald/University of Manitoba.

“Thaw slumps are also a sign of the permafrost warming. These can be seen just barely in the satellite image as small dark regions along cliff faces–both facing the ocean and within the river drainage basins. Erosion and slumping expose ancient organic carbon to the air and the hydrosphere, thus providing an extensive positive feedback to climate warming.” 

8. Bergy Bits

“Lines of bergy bits has collected along a thin shore margin at the point where the sea bottom rapidly deepens below ice keel depths, likely at approximately 2-4 meters. Although the grounded ice bits are continually melting, they are resupplied by more ice chunks shed from the permanent pack out in the channel. Two turbid plumes supplied by a river to the west of the Thomsen easily pass through the necklace of ice.”

9. Sampling Amid an Icy Barrier

“When we were sampling the water in this region, we found this ice barrier to be a bit more of a problem to navigate in our small inflatable boats, but ice along the shore did make it simple to sample sea ice. This image shows Greg Lehn preparing to launch our boat.”

10. A Suitable Landing Spot

Sampling in the Thomson River itself was somewhat simpler, once we had found a suitable place to land the plane. This image shows Greg Lehn scoping out the shore of the Thomsen River near its mouth.” 

A Closer View of 2020 Hurricane Damage

January 19th, 2021 by Kasha Patel

In October 2020, Mexico’s Yucatan Peninsula was doused by three storms: Gamma, Delta, and Eta. The storms came just months after tropical storm Cristobal delivered more than 50 centimeters (20 inches) of rainfall to the region in June. The accumulated rainfall and powerful winds significantly damaged mangrove forests in the region.

Mangrove damage in Dzilam el Bravo (2020)

Scientists from NASA, Wageningen University, and Federal University of Viçosa have been assessing the damage in Central America using satellite data. A team based in the state of Yucatan also caught the action closer to the ground, using drones to capture mangrove changes before and after the 2020 hurricane season.

All photos are provided by Jorge Herrera from the Center for Research and Advanced Studies of the National Polytechnic Institute (CINVESTAV) and his team.

Dzilam el Bravo

The October storms brought powerful winds that uprooted and defoliated mangrove forests near the coastal city of Dzilam el Bravo, located on the northern tip of the Yucatan Peninsula. The images below show changes from 2019 (top) to October 2020 (bottom), after Delta recently passed through the region.

Dzilam el Bravo, 2019

Dzilam el Bravo, 2020


The storms also brought major flooding to other Yucatan regions. Extreme precipitation can affect oxygen concentrations in soils and hinder photosynthesis for mangroves. Large storm surges can also cause physical damage and uproot trees. The images below show a mangrove near the city of Progreso in September 2020 (top image) and in November 2020 (bottom), after suffering from severe flooding.

Progreso, September 2020
Progreso, November 2020


The images below show an area near the Yucalpetén port, a few kilometers west of Progreso. Note the difference in defoliated trees from 2019 (top image) and in 2020 (bottom). In addition to defoliation, mangrove damage can also include the loss of seedlings, roots, and woody material.

Yucalpetén, 2019
Yucalpetén, 2020

The team will continue monitoring these and other sites for at least the next two years as they study mangrove regrowth and recovery through the COastal biodiversity RESilience to increasing extreme events in Central America (CORESCAM) project.

Read how NASA researchers are tracking similar mangrove damage with satellites.

January Puzzler

January 13th, 2021 by Kathryn Hansen

Every month on Earth Matters, we offer a puzzling satellite image. The January 2021 puzzler is above. Your challenge is to use the comments section to tell us what we are looking at, where it is, and why it is interesting.

How to answer. You can use a few words or several paragraphs. You might simply tell us the location, 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 feature. If you think something is interesting or noteworthy, tell us about it.

The prize. We cannot 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 first person to correctly identify the image at the bottom of this blog post. We also may recognize readers who offer the most interesting tidbits of information about the geological, meteorological, or human processes that have shaped the landscape. Please include your preferred name or alias with your comment. If you work for or attend an institution that you would like to recognize, please mention that as well.

Recent winners. If you’ve won the puzzler in the past few months, or if you work in geospatial imaging, please hold your answer for at least a day to give less experienced readers a chance.

Releasing Comments. Savvy readers have solved some puzzlers after a few minutes. To give more people a chance, we may wait 24 to 48 hours before posting comments. Good luck!

UPDATE on January 19 — This puzzler shows a soft-edged cloud hovering over a mountain range in Antarctica. Margaret Obrien was the first to specify the correct continent. The Image of the Day reveals that this is the Eisenhower Range of Antarctica’s Transantarctic Mountains near Terra Nova Bay. Holger Wille was the first to specify that the clouds are likely lenticular cloudsa cloud type that can form when fast moving wind is disturbed by a topographic barrier.