Parts Of Mexico City Are Sinking by More Than Two Centimeters Per Month, NASA Radar Shows

According to pre-Hispanic legend, the Aztecs, the Indigenous people who ruled central Mesoamerica until the Spanish arrived in 1521, were told by one of their gods to search for an omen — an eagle devouring a snake perched on a cactus — and to settle where they found it.

The sign is believed to have appeared at Lake Texcoco, where the Aztecs established their capital city, Tenochtitlán. Centuries later, the Spanish built Mexico City over the same lakebed.

Because Mexico City was built on a former lakebed, it is no surprise the capital has been sinking for decades. But new satellite imagery released by NASA shows the metropolis is descending far faster than previously believed.

As reported by The Associated Press, Mexico City, the second-largest city in terms of population in Latin America behind Sao Paulo, is sinking by nearly 10 inches a year, making it one of the world's fastest subsiding cities.

According to the outlet, extensive groundwater pumping and urban development have dramatically shrunk the aquifer, meaning that Mexico City has been sinking for more than a century, leaving many monuments and older buildings visibly tilted to the side. The contracting aquifer has also contributed to a chronic water crisis that is only expected to worsen.

And according to NASA's images, Mexico City is sinking at such a fast pace that the damage can be spotted from space.

The NISAR satellite, the NASA-ISRO Synthetic Aperture Radar mission, has detected that areas of Mexico City, including the capital's international airport and the Valley of Chalco, have been sinking more than 2 centimeters per month between October and January of this year.

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

NISAR can track real-time changes to the Earth's surface and is a joint mission between NASA and the Indian Space Research Organization.

The agency noted that Mexico City's sinking problem was first documented in 1925. By the 1990s and 2000s, some parts of the metropolitan area were subsiding by about 35 centimeters per year, damaging infrastructure such as the city's metro system.

NISAR scientist Paul Rosen told The Associated Press that by capturing detailed images of the Earth from space, the mission is also uncovering things that cannot be seen from the surface.

"It's basically documentation of all of these changes within a city," Rosen said. "You can see the full magnitude of the problem."

Over time, the team hopes to zoom in further on specific areas and eventually produce measurements at a building-by-building scale, the outlet reported.

Researchers say the technology could be used around the world to monitor natural disasters, shifting fault lines and the effects of climate change in regions such as Antarctica.

Rosen added that it could also strengthen early warning systems, potentially helping authorities issue evacuation orders ahead of events such as volcanic eruptions.