New radar view from space revealed how fast Mexico City is sinking
Mexico City, one of the world's largest metropolises, has once again become one of the most striking examples of a problem that unfolds slowly but leaves deep and very concrete consequences for everyday life, infrastructure, and long-term urban planning. The latest data from the NISAR satellite, a joint mission of the American space agency NASA and the Indian Space Research Organisation ISRO, showed that some parts of the Mexican capital and its wider urban zone are sinking by more than two centimeters per month. These are preliminary measurements collected between October 25, 2025, and January 17, 2026, during the dry season, when the effect of groundwater pumping is especially important for understanding ground movement. Although a few centimeters in one month may seem like a small change, in a city that has been dealing with this process for more than a century, such movements add up to serious damage to roads, water pipes, building foundations, sewers, and transport infrastructure.
NISAR is one of the most advanced radar systems ever sent into orbit to observe Earth. Its importance lies in the fact that it does not depend on daylight, visibility, or clouds, but uses synthetic aperture radar to precisely measure changes on the planet's surface. For Mexico City, this means that ground movement can be monitored from space consistently, over a large spatial extent, and without interruptions that would otherwise occur because of weather conditions or dense urban construction. The first views of ground movement in this region are therefore not only local news, but also an indicator of the broader potential of a mission that in the coming years could substantially improve monitoring of land subsidence, landslides, glaciers, forest changes, and the consequences of extracting water, oil, or gas from the subsurface.
A city built on a former lake and a depleted aquifer
The cause of Mexico City's pronounced subsidence is neither new nor simple. A large part of the city was built on the area of a former lake system in the Valley of Mexico, on soft sediments and clays that behave differently from stable bedrock foundations. As the city grew, the need for water increased, and the underground aquifer became one of the key sources of supply. Long-term groundwater pumping reduces pressure in the pores of the sediment, causing soil layers to gradually compact. When such compaction occurs in old lake deposits, surface lowering can be considerable and uneven, which particularly affects networks of pipes, tracks, roads, and old buildings.
The problem was recorded in Mexico City as early as 1925, when it was documented by an engineer, and since then it has developed into one of the world's best-known examples of urban subsidence. In some periods, especially during the 1990s and 2000s, parts of the metropolitan area were sinking by approximately 35 centimeters per year. Such changes are not evenly distributed: while some parts of the city move more slowly, others sink faster, creating height differences between neighboring zones and additionally increasing the risk of structural cracking. In practice, this means that infrastructure is exposed not only to gradual sinking, but also to stresses that arise when the ground beneath it moves at different speeds.
Water infrastructure is especially sensitive, because the rupture of water-supply and sewage pipes further worsens the already complex picture of water management. In a city that relies on underground reserves, damage to the network can increase water losses, and the need for additional pumping can then again contribute to subsidence. Such a vicious circle cannot be solved only by observation from space, but precise data on where the ground is sinking fastest allow authorities, engineers, and scientists to better determine priorities for repair and planning.
What NISAR showed in the first measurements
According to an analysis published by NASA's Jet Propulsion Laboratory, the new data show zones in Mexico City and the surrounding area that sank by up to several centimeters per month between late October 2025 and mid-January 2026. In the published view, the areas with the greatest lowering are marked in dark blue, while the yellow and red shades at this early stage of analysis are probably associated with remaining noise in the data, which is expected to decrease as the satellite collects longer time series. Among the recognizable landmarks in the view, Benito Juárez International Airport stands out in the central part of the image, while Lake Nabor Carrillo is visible northeast of the urban center.
The value of these data lies not only in confirming that Mexico City is still sinking, because that has been known for decades, but in the speed and reliability with which NISAR can produce an image of changes on the ground. The mission was launched on July 30, 2025, from the Satish Dhawan Space Centre in Sriharikota, on the southeastern coast of India, and was developed as the first major joint NASA and ISRO satellite mission for Earth observation. The satellite carries two synthetic aperture radars, in the L-band and S-band, which allows it to observe the surface at different wavelengths and under different conditions. NASA provided the L-band radar and the large antenna reflector, while ISRO provided the spacecraft platform, the S-band radar, and launch services.
NASA official Craig Ferguson assessed that images like this confirm that NISAR's measurements match expectations. He especially emphasized the importance of the long-wavelength L-band radar, because it can help monitor land subsidence in more challenging and densely vegetated areas, including coastal communities where the consequences of land sinking and sea-level rise can overlap. That dimension is important because subsidence does not occur only in Mexico City, but in numerous urban, agricultural, and coastal areas where people intensively use underground resources.
Why radar measurement is crucial for sinking cities
Synthetic aperture radar enables the comparison of repeated images of the same area and the measurement of very small changes in the distance between the satellite and the ground. Such a technique, known as interferometric SAR, has been used for years to monitor earthquakes, volcanoes, landslides, and subsidence. But NISAR brings an important upgrade because it is designed for systematic global observation of land and ice surfaces, with regular repeat observations. According to NASA's mission overview, NISAR collects observations of land and ice-covered areas every 12 days from ascending and descending orbits, with an average revisit time of approximately six days during the planned three-year baseline mission.
For rapidly changing cities, this is a major difference compared with occasional measurements or local geodetic campaigns. Field measurements are still necessary, but they cannot always cover an entire metropolis, especially when changes occur across hundreds of square kilometers. Satellite radar can reveal patterns that would remain disconnected from a ground-level perspective: one zone may be sinking because of intensive water pumping, another because of the weight of new infrastructure, and a third because of a combination of geological substrate and old urban-planning decisions. When these data are compared with maps of water supply, metro lines, roads, buildings, and population density, the result is a risk-assessment tool that is more useful than the general fact that a city is sinking.
In the case of Mexico City, the issue is not only scientific. The metropolitan area has about 20 million inhabitants and complex infrastructure, including one of the largest rapid transit systems in the Americas. Uneven subsidence can affect tracks, tunnels, bridges, stations, and accompanying drainage systems. In the long term, the problem also becomes an urban-planning issue: if certain areas are sinking faster than others, planning new buildings, roads, and public facilities must take into account not only the current condition of the ground, but also the likely change in the coming years.
The symbolism of the Angel of Independence and the visible consequences of slow ground movement
One of Mexico City's best-known symbols, the Angel of Independence on Paseo de la Reforma avenue, is often cited as a visible reminder of long-term subsidence. The monument was erected in 1910 to mark the centenary of Mexican independence, is about 36 meters high, and over time 14 steps were added to its base because the surrounding ground was gradually sinking. Such an example has a strong public effect because it turns an abstract process, which is otherwise measured in millimeters or centimeters, into a sight that can be recognized in the city itself.
But symbolic examples must not obscure the fact that the most expensive consequences are often less visible. Cracks in buildings, shifts in road surfaces, damage to underground installations, and changes in the slope of drainage systems can develop gradually, until they become costly infrastructure problems. Studies of Mexico City have already shown that the combination of groundwater pumping and infrastructure loading can significantly contribute to overall subsidence, with local conditions determining the scale and speed of the process. In other words, there is no single solution that would work equally in all parts of the city.
NISAR's measurements can therefore be seen as part of a broader transition toward data-based risk management. If the fastest changes can be reliably monitored from month to month, public services can more quickly identify critical corridors, vulnerable settlements, or parts of infrastructure where additional inspections are needed. This does not mean that a satellite can replace political decisions about water, urbanization, and infrastructure maintenance, but it can reduce the room for guesswork and postpone fewer interventions based on outdated assessments.
A global mission with local consequences
NISAR was conceived as a global mission, but the example of Mexico City shows well how space technology gains a very earthly application. The satellite should help monitor natural disasters, ecosystem conditions, crops, glaciers, ice sheets, and changes in Earth's surface. Its large antenna reflector, about 12 meters in diameter, is the largest radar antenna reflector NASA has so far sent into space, and precisely this construction enables the collection of large amounts of data over wide areas. Since radar can operate day and night, through clouds, and in different weather conditions, the mission is especially important for regions where optical satellites often have limited usability.
David Bekaert, a member of the NISAR science team from the Flemish Institute for Technological Research, described Mexico City as a well-known hotspot of subsidence, but also emphasized that images like these are only the beginning for the new mission. In his assessment, the sensor's unique capabilities and consistent global coverage should bring a range of new discoveries from different parts of the world. This is especially important for areas where land sinking occurs together with other risks, for example sea-level rise, floods, urban expansion, or droughts that increase pressure on groundwater.
For Mexico City, the new data do not change the basic diagnosis, but they increase the precision with which it can be monitored. For decades, the city has faced the consequences of the historical decision to develop a large urban agglomeration on a drained lakebed and to meet a significant part of its water needs from underground sources. In such circumstances, every new subsidence map is not only a scientific image, but a warning about the cost of long-term reliance on an aquifer that cannot be depleted indefinitely without consequences. NISAR now makes it possible to see that cost more clearly, more regularly, and in a way that can be compared over time.
Sources:- NASA Jet Propulsion Laboratory – report on NISAR's mapping of land subsidence in Mexico City (link)- NASA Science – overview of the NISAR mission and its scientific goals (link)- NASA Science – technical overview of the mission and frequency of observations of Earth's surface (link)- ISRO – official page of the NISAR mission and launch data (link)- Springer / Natural Hazards – scientific paper on the risks of land subsidence and faulting in Mexico City (link)
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