By John Fernando Muñoz | 2026-06-17

Mexico City's Angel of Independence monument has stood on Paseo de la Reforma since 1910, when it was built to commemorate the nation's centennial.

Yet most visitors do not realize that 14 steps have been added to the base of the iconic marble and bronze landmark over the decades.

The monument, whose column stands roughly 35 meters tall, did not grow -- the ground around it sank.

That slow, imperceptible descent is now being monitored from an altitude of 747 km. And in late April, NASA and the Indian Space Research Organization (ISRO) published the most precise measurements of the sinking ground to date.

The data is not encouraging. But it may be exactly what Mexico City, a metropolis of more than 22 million, needs in order to address the problem.

Mapping ground movement

The NASA-ISRO Synthetic Aperture Radar (NISAR) satellite was launched on July 30, 2025, from India's Satish Dhawan Space Center as a joint project between the two space agencies.

One of the most powerful radar systems ever launched into space, it has been tasked with mapping ground movement beneath Mexico City, which is one of the fastest-sinking capitals in the world.

Between October 25, 2025, and January 17, 2026, during Mexico City's dry season, NISAR mapped land subsidence across the entire metropolitan area.

Some parts of the region were found to be sinking at a rate of more than two centimeters per month, a rate that, in the worst-affected zones, exceeds 24 centimeters of annual descent.

Like the Angel of Independence, Benito Juárez International Airport sits inside one of the most critical zones, shown in the darkest tones on the map.

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

"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."

Mexico City is sinking

Mexico City's land subsidence problem dates back to 1325, when the Mexica (Aztecs) founded their capital, Tenochtitlan, on an island in Lake Texcoco.

After the Spanish conquest, the lake was drained and the city expanded across its soft clay sediments. Those sediments have been compacting ever since.

Today, Mexico City is trapped in a dangerous loop. As groundwater is pumped from beneath it, the ground sinks, with some areas dropping faster than others.

According to experts from the National Autonomous University of Mexico, these conditions crack buildings and damage water pipelines, among other damage.

Water losses caused by damaged pipelines prompt the city to pump even more groundwater from the underground aquifer, exacerbating the problem.

The sinking is not uniform, and that is precisely what makes it so destructive. One city block can drop several centimeters faster than the one next to it, and that differential movement is what fractures infrastructure.

In May 2021, an elevated section of the metro near the Olivos station on Line 12 collapsed onto the road as a train passed over it, killing 26 people.

The post-collapse analysis found that differential displacements between the columns supporting the overpass may have been a decisive factor.

A peer-reviewed study published in Scientific Reports in 2024 found that land subsidence rates along Mexico City's metro network reach 500 millimeters per year at certain points.

US-India partnership

NISAR is the first satellite to simultaneously carry two synthetic aperture radar instruments at different wavelengths. NASA's L-band radar uses a 24-centimeter wavelength that penetrates cloud cover, vegetation and darkness.

The S-band instrument, supplied by ISRO's Space Applications Center, uses a shorter wavelength more sensitive to agriculture and grassland ecosystems.

Together, they allow scientists to detect subtle changes in the Earth's surface that would be invisible to conventional optical satellites.

NISAR features a deployable radar antenna reflector roughly 12 meters wide, the largest NASA has ever sent into space, and monitors Earth twice every 12 days.

It cost $1.5 billion to build, making it the most expensive Earth-observation satellite in history.

"NISAR's long wavelength L-band radar will make it possible to detect and track land subsidence in more challenging and densely vegetated regions," said Craig Ferguson, deputy project manager at NASA headquarters in Washington.

Practical value for Mexico

Mexican media covered the findings extensively, with detailed reports published within days of the NASA announcement, and in a consistent tone: the NISAR data confirms, with fresh precision, what many already suspected.

NISAR's near-real-time monitoring capability opens an opportunity to design more effective policies to address issues surrounding the city's land subsidence.

The solution, however, ultimately depends on sustainable water management and urban planning adapted to a ground that will not stop moving.

Urban planning, covering housing policy, infrastructure repair, drainage improvements, and airport operations, depends on the premise of stable ground.

In some areas, those assumptions require constant updating.

NISAR offers precisely the tool to carry that out on a regular, automated basis, without field surveys and without waiting for the next collapse to reveal where damage has been quietly accumulating.