Earth Matters

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.

Microbialites

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.

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

Progreso

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

Yucalpetén

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.

Assessing Locust Damage from the Ground

April 16th, 2020 by Kasha Patel


East Africa is experiencing one of its worst locust outbreaks in decades. The voracious insects are devouring thousands of hectares of farmland and forests, and threatening food security for millions across the region, which is already vulnerable to food shortages.

Locusts swarm a field in Elgeyo Marakwet County in Kenya. Photo credit: Gentrix Machenje

To help manage outbreaks, NASA scientists are developing tools to track locust breeding grounds and to assess crop damage. We previously reported on the satellite data used in these assessments, but researchers are also using ground-based observations from several local organizations and government offices. Such information is used to validate estimates of crop conditions made from satellite imagery and included in international crop forecasts.

“Our ground partners give monthly updates on crop conditions and major events like flooding and disease outbreaks,” said Catherine Nakalembe, a food security researcher with NASA SERVIR and NASA Harvest. “They help provide critical ground information when the remote sensing data are not sufficient.”

The following photos, taken by people in Uganda and Kenya, show some of the effects of the locust outbreak on farms.

Elgeyo Marakwet County, Kenya

Kenya is experiencing its worst locust outbreak in 70 years. The image at the top of this page and the one below shows locusts (yellow) swarming a field in March 2020.

Photo credit: Gentrix Machenje


The images were taken by Gentrix Machenje. Machenje is a county officer who works with NASA SERVIR and provides information for Kenya’s National Crop Monitor.


Karamoja, Uganda

The photos below were taken in early April 2020 in the Karamoja region of northeast Uganda. Officials believe the locusts hatched from eggs laid a few weeks ago.

Photo credit: Evans Noble Opiolo


The images were taken by Evans Noble Opiolo, an agricultural officer in the Nakapiripirit District who also contributes to a Disaster Risk Financing Project for Uganda’s Office of the Prime Minister. Such officers are reporting on locust locations and are often present when ground-control operations, such as pesticide spraying, are in progress.

Photo credit: Evans Noble Opiolo
Photo credit: Evans Noble Opiolo

To learn more about NASA’s response to the 2020 locust outbreaks, read our recent article.

Building Roads in the Congo Rainforest

November 27th, 2019 by Kasha Patel
A former private logging road in the Northern Republic of Congo is now being converted to a public road. Photo credit: Fritz Kleinschroth

In a recent article, we described a study of how road networks in the Congo Basin have changed over the past 15 years and how they have affected deforestation rates. Those networks have grown significantly, but not all roads lead to long-term forest destruction. By closing roads when they are no longer needed, people can help avoid permanent damage to the forest.

Though the researchers conducted much of their research via remote sensing and computer work, they also made several trips into the Congo Basin. Their photos shed more light on some of the economic activities in the rainforest.

Riparian forest in the Republic of Congo. Photo credit: Nadine Laporte

The Congo Basin is covered by tropical rainforests and swamps and is famous for its rich biodiversity. At two million square kilometers (1.2 million square miles), the Congo rainforest is the second largest in the world and about the size of Mexico. The image above shows a forested area near a stream in the Republic of Congo.

As road networks have expanded, the roads are bringing people deeper into the jungle and closer to wildlife. In general, forest roads lead to more human activity and to unregulated or destructive events, such as poaching, mining, or illegal logging. The image below demonstrates how roads are encroaching on wildlife habitats.

Gorilla by a roadside in Republic of Congo. Photo credit: Fritz Kleinschroth

The majority of new roads are built for selective logging activities, which is one of the main economic activities in the rainforest. Companies practice selective logging where only the most valuable tree species are cut, which usually results in cutting one tree per hectare on average. In order to harvest this timber though, the companies must build roads, usually unpaved, that allow the trucks and tractors to drive deep into the forest. The photos below show scenes of timber extraction and a timber yard.

Timber extraction in Republic of Congo. Photo credit: Fritz Kleinschroth

Timber yard of a logging company in Cameroon. Photo credit: Fritz Kleinschroth

Sometimes roads are used by farmers to reach further into the forest and establish small-scale agricultural plots. The image below shows a small landholder in a forest near Mbandaka in the Democratic Republic of Congo. The woman is carrying a basket of manioc (cassava). She is also holding a maranthaceae leaf, which is commonly used for wrapping and cooking on a fire.

Photo credit: Scott Goetz

In the recent study, the researchers found that deforestation rates were highest around older, open roads. Specifically, the highest rates were found in the Democratic Republic of Congo due to agriculture and a high population density.

Researchers showed deforestation rates were the lowest around abandoned or closed roads. Abandoned roads reduce human traffic and allow vegetation to grow over the dirt path. The image below shows an abandoned road in the Republic of Congo that is overgrown with regenerating trees and plants. These plant species pictured are popular for gorillas to feed on and can help restore the gorillas’ natural habitat.

Photo credit: Fritz Kleinschroth

Abandoned roads were most commonly found inside logging concession areas. After a logging company was no longer using the road, the road was often closed or abandoned. Sometimes the road can be closed off by simply using a log to prevent vehicles from entering, as shown below.

To read the accompanying article, click here: When a Road Leads to Deforestation

Photo credit: Fritz Kleinschroth

NASA GLOBE Fall Data Challenge: What’s Up in Your Sky?

October 4th, 2019 by Joe Atkinson, NASA Langley Research Center

Who knew that being a scientist could be as easy as pointing your phone at the sky? This month, NASA and the GLOBE Program are asking citizen scientists to take out their phones and report what kinds of clouds they see above them.

From October 15 to November 15 citizen scientists young, old, and in-between can submit up to ten cloud observations per day using the GLOBE Observer app or one of GLOBE’s other data entry options (for trained members). Participants with the most observations will receive a personalized thank you from a NASA scientist.

“What excites researchers about GLOBE observations is the ability to see what’s up in the sky from volunteers’ perspectives all over the world,” said Marilé Colón Robles, lead for the GLOBE Clouds Team at NASA’s Langley Research Center. “What our eyes can see is difficult to fully duplicate with instruments. Merging these views is what makes a complete and impactful story.”

“We want to do a data challenge in the fall and see if there are any differences from what was observed during the spring data challenge of 2018,” said Colón Robles. “From thin, high clouds that are hard for satellites to detect to dust storms that impact our daily lives, these observations play an important role in better understanding our atmosphere.”

At NASA, scientists work with a suite of satellite instruments known as the Clouds and the Earth’s Radiant Energy System (CERES). Though they have these highly sensitive instruments, it can sometimes be difficult for scientists to distinguish features such as cirrus clouds from snow cover in their imagery because both are cold and bright from a satellite perspective. By comparing satellite images from a particular area with data submitted by citizen scientists, researchers can differentiate between the two.

Lucky GLOBE observers might make an observation while the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) is overhead. CALIPSO is a joint mission between NASA and the French space agency (CNES) that uses laser pulses to measure clouds and atmospheric aerosols. Citizen scientists who make observations at the same time and place as CALIPSO will receive an emailed satellite comparison of CALIPSO’s measurements showing features such as high clouds, dust, and smoke. Scientists are especially interested in these observations in order to improve their understanding of dust storms. During the challenge, make sure you turn on daily satellite notifications in the app or use this satellite overpass website to see the schedule for your location.

“Last year’s challenge gave researchers special glimpses into cloud types around the world,” said Colón Robles. “Photographs provided by observers gave insight into events such as dust storms and wildfires. Our hope is to once again learn from the community and together study our atmosphere.”

The 2018 data challenge, which took place in the spring, received more than 56,000 cloud observations from more than 15,000 locations in 99 countries and Antarctica.

NASA is a sponsor of GLOBE, an international science and education program that provides students and the public with the opportunity to participate in data collection and the scientific process. NASA GLOBE Observer is a free smartphone app that lets anyone make citizen science observations from the palm of their hand.

Cloud Identification Resources and Tips

Data collection and data entry help

A Bit Less of Excelsior Glacier in Photographs

June 11th, 2019 by Kasha Patel

Excelsior Glacier, June 2019 / Credit: Johnstone Adventure Lodge

In a recent article, we showed satellite imagery of the dramatic retreat of Alaska’s Excelsior Glacier over the past two decades. The glacier has shortened by 30 percent since 1994, primarily due to rising temperatures and calving. What was once ice is now a pool of meltwater called Big Johnstone Lake. Images collected closer to the ground also show dramatic change.

These false-color images show Excelsior Glacier and Big Johnstone Lake on  October 16, 1986 (left) and October 31, 2018 (right), by the Landsat satellites.

In photos taken in 1909 by the U.S. Geological Survey, Excelsior glacier nearly touched the Pacific Ocean, resting on a sliver of forested land. Today, the glacier is separated from the ocean by Big Johnstone Lake, which measures nearly five times the area of New York City’s Central Park.

Excelsior Glacier, 1901 / Credit: U.S.Geological Survey

The following images were taken by staff from the Johnstone Adventure Lodge, which was built near the mouth of the glacier.

The image below shows Excelsior Glacier in 2016 (first) compared to 2018 (second). While the second picture was taken from a farther distance, the absence of icebergs in Big Johnstone Lake stands out.

Excelsior Glacier in 2016 / Credit: Johnstone Adventure Lodge

Excelsior Glacier in 2018 / Credit: Johnstone Adventure Lodge

The following image also shows the complete separation of the glacier into its eastern and western tributaries (as seen in the top 2018 satellite photo). The owners of the lodge have named the right tributary “Roan Glacier.”

Eastern and western tributaries, May 2019 / Credit: Johnstone Adventure Lodge

The following images show changes on Roan Glacier from 2018 to 2019. In 2019, you can see a rogue chunk of ice on right (first image below). According to the owners of the Johnstone Adventure Lodge, the chunk “was certainly not separated in September 2018,” as shown in the second picture.

Roan Glacier in 2019 / Credit: Johnstone Adventure Lodge

Roan Glacier in 2018 / Credit: Johnstone Adventure Lodge

This last image shows 15-20 harbor seals that hang around the glacier. Harbor seals often haul-out on icebergs, so fewer icebergs will likely mean fewer seals as time goes on.

Seals on iceberg, 2018 / Credit: Johnstone Bay

 

Photo courtesy of Luciano Javier Avila.

Dozens of wildfires blazed along the Atlantic coast of Argentina coast last winter. One of them left behind a massive burn scar near the Valdez Peninsula. When we wrote about the fires last month, we were unable to say with certainty whether the plume rising off the burn scar was airborne ash or dust. A quick recap from our article:

This part of Argentina’s coast is sparsely populated, arid, and covered in scrubby undergrowth. The closest city is Puerto Madryn, more than 30 kilometers (20 miles) from the burn scar. Due to this remoteness, it is difficult to verify the composition of plumes.

At the time, Santiago Gassó, a NASA scientist who studies the global transport of ash and dust, gave us his best guess:

While Gassó believes ash caused this plume, it is possible that finely ground rock and soil dust also could have become dislodged by the fire. Vegetation and roots (which usually hold the soil in place) would have been removed by the fire, making it easier for the strong regional winds to sweep dust off of the land.

Since then, a reader has written to us with more details. Luciano Javier Avila, a biologist with the Patagonian Institute for the Study of Continental Ecosystems, walked around the site just days after the fires and took photos of the burned area. He confirmed that the cloud was, in fact, dust. Strong winds in January and February caused dust plumes visible from Madryn.

The fire highlights the importance of plants in this semi-arid region, according to Avila. Many of the plants which used to grow here are larrea (“jarilla” in Spanish), a desert shrub that flowers in yellow. Without their roots holding the soil together, the wind was able to blow large amounts of fine dust into the air.

Green Ice and Snow

March 21st, 2017 by Kathryn Hansen

You never know where phytoplankton will turn up next. From space, we regularly see colorful blooms of them swirling in the world’s oceans. Inland basins and waterways support them too, such as Florida’s Lake Okeechobee, Washington’s Hood Canal, and North America’s Great Lakes.

Even the waters off the coast of Antarctica can sustain blooms. We recently showed a satellite image in which algae in a harbor near the Ross Sea had turned the sea ice a wild shade of green. As this photograph shows, they also appear to thrive on the snow and ice capping the southern continent.

“I was in Antarctica in February 2013 and saw plenty of algae happily growing in the ice (green, yellow, and red),” said ocean scientist Norman Kuring of NASA’s Goddard Space Flight Center. “I took this photo on Orne Island showing lots of green snow and ice.”

Kuring notes, however, that the type of phytoplankton inhabiting the snow and ice on Orne Island — on the opposite side of the continent, near the Antarctic Peninsula — is probably different from the species that bloomed in the Ross Sea. Direct sampling and analysis is the best way to know for sure, but that’s not always possible, especially in remote regions.

img_5473

Photo by Adam Voiland. Taken from Rodeo Beach in Marin County, California, in the evening on December 14, 2015.

If you have ever stood on a beach before sunset and gawked at a gleaming line of light extending toward the horizon, you have seen a glitter path.

What causes this spectacular optical phenomenon? Glitter paths are made up of many bright points of light reflecting off tiny ripples, waves, and undulations on the water surface and back at a sensor (for instance, a camera or human eye). Together, these points of light make up areas of sunglint. The appearance of glitter paths on water varies depending on the height of the Sun above the horizon, the height of the surface waves, and the position of the observer.

For instance, if the Sun had been directly overhead and above perfectly calm water, I would have seen a circular reflection that looked much like the Sun in the sky. However, when I took this photograph from Rodeo Beach near sunset in December 2015, the reflection appeared as a long elliptical line of light because the Sun was quite low in the sky. Note how much the roughness of the water surface affected the glitter path. Near the shore, where waves had just broken and the water surface was filled with foam, the glitter path was significantly wider than it was in the smoother waters farther off shore.

sunglint

NASA image acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra satellite on the morning of June 22, 2015.

Sunglint is visible from space as well. In the satellite image of California above, which the Terra satellite captured on the morning of June 22, 2015, notice the line of light running over the Pacific Ocean. This line of sunglint traces the track of Terra’s orbit. If the ocean surface had been completely smooth, a sequence of perfect reflections of the Sun would have appeared in a line along the track of the satellite’s orbit. In reality, ocean surfaces are chaotic and often in motion due to the constant churn of waves and winds. As a result, light reflecting off the surface was scattered in many directions. This left the blurred, washed out line of light along the satellite’s orbital track that you see here instead.

You can learn more about sunglint and glitter paths from stories by Darryn Schneider, Atmospheric Optics, Joseph Shaw, Richard Fleet, NASA Earth Observatory, and Earth Science Picture of the Day.

Editor’s Note: Ground to Space is a recurring series of posts on NASA Earth Observatory’s Earth Matters blog that pairs ground photography and satellite imagery of the same feature or phenomenon. If you have a photograph that you think would be a good candidate, please email Adam Voiland.

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.”

Full_barges2_going_north_GanRiver_Poyang

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

SandDredger2

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.