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Digging Back in Time in the UAE

✇NASA Science
By: Lauren Dauphin
Limestone ridges appear as linear features running north–south with orange-toned desert to the west and a darker-toned mountain range to the east.
Jabal al Fāyah rises from the Rub’ al Khali desert in an image captured by the OLI (Operational Land Imager) on Landsat 8 on October 23, 2025.
NASA Earth Observatory / Lauren Dauphin

About an hour’s drive east of Dubai’s gleaming towers and artificial islands, a quieter, more natural landscape takes shape. At the far northern edge of the Rub’ al Khali, a saffron-colored sand sea laps against the Al-Hajar Mountains. A series of pale ridges rises finlike from the desert plain, with the largest—Jabal al Fāyah—standing 412 meters (1,352 feet) above sea level.  

The Landsat 8 satellite captured this image of the ridges cutting across the Emirate of Sharjah in the northern part of the United Arab Emirates on October 23, 2025. To geologists, the limestone ridges are a reminder of the region’s watery past, signs that this land lay underwater tens of millions of years ago when the sedimentary rock layers were deposited.

Jabal al Fāyah functions as a barrier, trapping windblown sand in dune fields to its west. The weathering of iron-bearing minerals in the sand grains gives the dune fields their orange hue. To the east, the branching channels of overlapping alluvial fans extending from the Al-Hajar Mountains carry gravels and eroded sediments from basalts and other dark mafic rocks. 

The dark rocks to the east—part of the Samail Ophiolite—are known to geologists for being among the world’s largest, best-preserved, and most accessible exposures of ancient oceanic lithosphere, the rigid outer layer of Earth that includes both the crust and upper mantle. Oceanic lithosphere like this is normally subducted and recycled back into the mantle when tectonic plates collide. But in this area, a large section from beneath the Tethys Sea was scraped off and thrust onto the Arabian plate in a process called obduction.  

Development associated with Dubai appears as a light gray zone along the coast of the Persian Gulf with the dark gray Al-Hajar Mountains on the far right side of the image. A ridge lies in the middle of the image in a sandy area.
Dubai lies to the west of the limestone ridges, and the Al-Hajar Mountains lie to the east, in an image acquired by the OLI (Operational Land Imager) on Landsat 8 on October 23, 2025.
NASA Earth Observatory / Lauren Dauphin

The Jabal al Fāyah ridges themselves are made up of marine limestone that was deposited on top of the ophiolite over tens of millions of years spanning the late Cretaceous through the early to mid-Paleocene. Limestone typically forms along continental margins in warm, shallow oceans, often in lagoons and coral reefs, out of the calcium carbonate found in the shells and skeletons of marine life. In many parts of the ridges, coral fragments and marine invertebrate fossils are visible embedded in the rock. A feature called Fossil Rock sits a few kilometers north of Jabal al Fāyah and adjacent to the limestone ridge Jabal Mulayḩah. It contains an abundance of snail, clam, and sea urchin remains. 

For archaeologists, the ridges are at the center of a much more recent tale of human adaptation and survival that has played out in just the past few hundred thousand years. The ridges and parts of the surrounding landscape—inscribed as a UNESCO World Heritage site in 2025—are dotted with dozens of archaeological sites that trace human occupation on the Arabian Peninsula back to between 210,000 and 120,000 years ago, to the Middle Paleolithic. That was a period when waves of anatomically modern humans (Homo sapiens) migrated out of Africa and shared the planet with other groups such as Neanderthals.   

Many of the sites contain stone flakes, blades, scrapers, hand axes, and other stone tools. The archaeological treasure trove offers early evidence of modern humans surviving in a harsh desert environment and raises questions about the routes modern Homo sapiens may have taken on their journey out of Africa.  

Geological evidence indicates that lakes periodically formed on the east side of the ridge, providing critical food and water resources that would have supported early inhabitants in this unforgiving climate. Rocky overhangs along the ridge would have provided shelter from the heat and wind. Some of the sites show evidence of intermittent occupation beginning as early as 210,000 years ago, making this one of the earliest signs of human habitation on the Arabian Peninsula.   

NASA Earth Observatory images by Lauren Dauphin, using Landsat data from the U.S. Geological Survey. Story by Adam Voiland.

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Development associated with Dubai appears as a light gray zone along the coast of the Persian Gulf with the dark gray Al-Hajar Mountains on the far right side of the image. A ridge lies in the middle of the image in a sandy area.

October 23, 2025

JPEG (3.89 MB)

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NASA-Funded Study Shows Wildfire Smoke’s Hidden Ozone Toll

✇NASA
5 Min Read

NASA-Funded Study Shows Wildfire Smoke’s Hidden Ozone Toll

Canadian wildfire smoke carried carbon monoxide — a building block of ground-level ozone — thousands of miles downwind in June 2023.
Credits:
NASA’s Goddard Space Flight Center

Wildfire smoke is stoking a new challenge for cleaner air. A NASA-supported study published Thursday found that, over the last decade, wildfires have worsened ground-level ozone pollution across much of the contiguous United States, creating unhealthy air far from active flames.

Wildfires have become an increasingly important contributor to ground-level ozone, or smog, across much of the United States, researchers report June 4 in the journal Science. Nationally, fires offset nearly four years’ worth of ozone-control gains, with larger setbacks in the West and Midwest.

Smoke often is associated with the soot, ash, and other fine particles that make the air look hazy. But wildfires also emit gases such as carbon monoxide, which can help form surface ozone in sunlight when other pollutants are present. Surface ozone is an invisible pollutant harmful to human health, plants, and crops. As smoke plumes travel and mix with other pollution, those reactions can drive ozone increases hundreds or even thousands of miles from active fires.

“NASA Earth observations, along with ground monitoring networks, help reveal air quality risks from wildfires that can cross state lines, giving air quality managers better decision-making information as wildfire smoke affects more communities,” said John Haynes, manager of NASA Earth Action’s Health and Air Quality program at the agency’s Headquarters in Washington. “This is a strong example of NASA science serving communities here in the U.S.”

Building a clearer ozone picture

High in the atmosphere, ozone shields Earth from harmful ultraviolet radiation. Near the ground, however, ozone can irritate lungs, worsen asthma and other respiratory diseases, and increase health risks for children, older adults, outdoor workers, and people with existing health conditions.

To track surface ozone changes, researchers turned to deep learning, a form of artificial intelligence that finds patterns across large datasets. They used it to build a first-of-its-kind dataset estimating daily surface ozone from 2003 to 2024 on a kilometer-by-kilometer grid — about 0.6 miles on each side — across the contiguous U.S. The work received support from NASA’s Health and Air Quality program and other NASA grants.

The scientists combined data from about 1,000 ground-based air quality stations with atmospheric model data, weather information, wildfire pollution data, and satellite-derived information, including products from the Visible Infrared Imaging Radiometer Suite (VIIRS) and the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments.

Smoke from Canada’s 2023 wildfires spread across North America. Tan to deep red colors show smoke intensity, estimated from black carbon in NASA’s GEOS-FP model.
NASA’s Scientific Visualization Studio (SVS) and NASA’s Global Modeling Assimilation Office (GMAO)

Their analysis revealed two distinct periods. From 2003 to 2015, U.S. ground-level ozone generally declined as emissions of ozone-forming pollutants decreased. After 2015, however, those gains slowed or reversed in many places. By comparing estimated ozone levels with scenarios that removed wildfire influence, the researchers found that pollution from wildfires was a main factor in that shift.

Without the wildfire contribution, ground-level ozone in the Midwest, for example, would likely have continued to decline. Instead, wildfires erased about 5.3 years’ worth of ozone-control progress since 2015.

“People in the Midwest may think fires burning far away will not affect them,” said the study’s corresponding author Jun Wang, an atmospheric scientist at the University of Iowa in Iowa City. “But once wildfire pollution is in the air, it can move across regions. Pollution from one place can affect air quality in another.”

Measuring the health toll

The study also found that wildfire-driven ozone increased exposure to unhealthy air and likely contributed to premature deaths. Premature deaths associated with long-term wildfire-related ozone exposure in the U.S. increased by an estimated 318 deaths per year after 2013, with the post-2013 average 46% higher than in the previous decade. The researchers calculated premature deaths using average lifespan, ozone exposure estimates, and population density.

The 2023 Canadian wildfires showed how widely those risks can spread, with smoke-driven ozone increases stretching across the Midwest and into parts of the Northeast and South. Overall, from 2022 to 2024, wildfires exposed an additional 43 million people in the U.S. to conditions that did not meet current federal air quality standards for ozone, the researchers estimated.

Capturing that national picture is difficult from ground monitors alone. Ground monitors remain the backbone of U.S. air quality tracking, but they do not cover every community. NASA’s scientifically validated satellite observations and models help researchers and agencies see air quality patterns across states, regions, and fire seasons.

That broader air quality work includes newer missions such as TEMPO (Tropospheric Emissions: Monitoring of Pollution). Launched in 2023, TEMPO is NASA’s first mission to use a space-based spectrometer to provide hourly daytime measurements of air quality over North America. Its view is sharp enough to distinguish pollution patterns, including surface ozone, across areas only a few square miles wide, a major improvement over earlier satellites.

Together, these capabilities help researchers and agencies see smoke-related ozone patterns that might otherwise be harder to detect, especially in rural and remote areas.

The work also points toward a practical use of NASA science during fire season. Wang’s team has used NASA support to develop FireAQ, a decision-support system that brings satellite observations, model forecasts, and fire and aerosol products into weekly briefings with state and local air quality officials. The goal is to help officials see where smoke-related pollution may move next and give communities better information.

About the Author

Emily DeMarco

Emily DeMarco

Writer/Editor (IV), Earth Science Division

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Last Updated
Jun 05, 2026
Contact
Emily DeMarco
Location
Goddard Space Flight Center
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