How the NISAR satellite is revealing Mexico City’s sinking

Cities often seem fixed in place. Streets, towers and monuments suggest permanence. Yet some urban areas are constantly shifting in ways that are easy to miss from one day to the next.

Mexico City is a clear example. The land beneath the capital is steadily subsiding, and a new satellite is now showing that motion more clearly than at any point before.

From hundreds of kilometres above the planet, researchers can measure subtle vertical changes with high precision. The results back up a problem that has been recognised for years, while also showing just how rapid and extensive the sinking has become.

Subtle city sinking revealed

Mexico City has been sinking for more than a century. It is not a dramatic, sudden collapse, but a slow process that progresses bit by bit.

As the years pass, the consequences become hard to ignore: road surfaces split, buildings lean, and essential services are repeatedly strained by the shifting ground.

The latest observations indicate that some neighbourhoods are dropping by more than about 13 millimetres per month. Over long periods, that monthly loss accumulates quickly.

Built on fragile ground

The city is built on the sediments of an ancient lakebed. Centuries ago, this basin held water; today, soft deposits remain below the surface.

These materials compress readily when loaded.

With roughly 20 million people across the region, water demand is enormous. Pumping groundwater removes support from below, leaving voids. As those spaces collapse, the sediments compact and the surface sinks.

Heavy urban expansion

Present-day Mexico City is extremely heavy. High-rise buildings, major roads and dense residential development push down on ground that is already prone to compression, worsening subsidence.

Together, groundwater extraction and the weight of the built environment drive a persistent downward trend. The movement is not triggered by a single factor, but by the interaction of human pressure and natural ground conditions.

Problem known for decades

Engineers were already documenting the issue by 1925. Even at that stage, parts of the city were visibly subsiding, and the pace increased over time.

By the late 20th century, some districts were dropping by about 35 centimetres each year (around 14 inches per year). That created major difficulties, particularly for transport infrastructure such as the Metro.

Rails can drift out of alignment and tunnels can change shape. Upkeep becomes an ongoing task, and the city is forced to adjust repeatedly.

A significant advance arrived with the launch of the NISAR satellite in July 2025. The mission is a partnership between NASA and ISRO.

Using early passes over Mexico City between October 2025 and January 2026, NISAR gathered initial measurements that scientists converted into a detailed map of motion, pinpointing the areas where the ground is sinking most quickly.

NISAR advanced radar technology

Rather than using visible light, NISAR employs L-band synthetic aperture radar, enabling it to collect data through cloud cover, vegetation and darkness.

“Images like this confirm that NISAR’s measurements align with expectations,” said Craig Ferguson, deputy project manager at NASA Headquarters in Washington.

“NISAR’s long-wavelength L-band radar will make it possible to detect and track land subsidence in more challenging and densely vegetated regions such as coastal communities where they may have the compounding effects of both land subsidence and sea level rise.”

This capability also makes the system more dependable than many earlier approaches.

Tracking Mexico City ground movement with NISAR

The satellite revisits the same locations several times each month, which helps it pick up even small shifts in elevation.

The new imagery highlights prominent reference points. Benito Juarez International Airport sits close to the centre of the assessment.

Lake Nabor Carrillo also shows up distinctly in the dataset. Landmarks like these allow scientists to compare how different parts of the city move over time.

A monument tells all

One of the clearest examples of subsidence can be seen at the Angel of Independence. Built in 1910, it originally sat level with the surrounding streets.

Over the years, 14 steps were added at its base-not to increase the monument’s height, but to maintain access as the nearby ground level fell.

The structure itself did not move upward. Instead, the city around it moved downward.

Global implications ahead

Mexico City is not unique. Many urban centres built on compressible ground face comparable threats. Coastal zones, river deltas and agricultural regions are particularly exposed.

“Mexico City is a well-known hot spot when it comes to subsidence, and images like this are just the beginning for NISAR,” said David Bekaert, a project manager at the Flemish Institute for Technological Research and a member of the NISAR science team.

“We’re going to see an influx of new discoveries from all over the world, given the unique sensing capabilities of NISAR and its consistent global coverage.”

That points to the likelihood that other, less visible problems will soon be detected.

A shared space mission

NISAR is also a notable example of collaboration between the United States and India. The satellite was launched from Satish Dhawan Space Centre in India.

NASA supplied the L-band radar and antenna system. ISRO provided the spacecraft and included an S-band radar.

The partnership brings together specialist strengths from both organisations.

Two radars show how city may sink

NISAR operates with two radar instruments at different wavelengths, providing a more rounded view of changes at Earth’s surface.

It maps land and ice on a 12-day cycle. A large reflector about 12 metres wide collects detailed returns, making it the biggest radar reflector NASA has ever flown in space.

Understanding future risks

For Mexico City, these measurements are immediately useful. They enable planners to pinpoint areas at greatest risk and to make more informed choices about repairs and future development.

NISAR will continue monitoring locations around the world as well. As additional observations are gathered, scientists will develop a more complete picture of how the ground rises and falls.

The assumption that the land beneath our feet is always stable does not apply everywhere, and NISAR is making that increasingly evident.