The parallel, curved mountain ridges of the Sierra Madre Oriental are a striking feature of the landscape of northeastern Mexico. The spot where these folds meet against Mexico’s second-largest metropolitan area caught the attention of an astronaut aboard the International Space Station, who took this photo on August 26, 2026.
Monterrey, the capital of the state of Nuevo León, is an industrial center that supports heavy industries such as hardware stores and steel mills, as well as manufacturing facilities for products ranging from textiles to processed foods, glass and plastics. The metropolitan area is home to 5.3 million people, according to the 2020 census. And while the city has seen overall population growth since 1990, the number of people living within a 5-kilometer (3-mile) radius of the city center has declined, researchers have found, a trajectory shared with many of Mexico’s metropolitan areas.
In the case of Monterrey, urban expansion collides with unforgiving terrain. Along the southern edge of the city, layers of limestone, deposited in the late Mesozoic era and then folded between 80 and 50 million years ago, form the Sierra Madre Oriental. Over millions of years, the weaker rock layers have eroded, leaving behind the distinct ridges that link Monterrey today.
The Santa Catarina River runs through the mountains and reaches the semi-arid alluvial plain where the city is located. Due to the dry environment, the river carries little or no water most of the time. But its canal is crucial for collecting runoff from summer rains and serves as an important natural area for plant and animal life within the city.
The river crosses the urban center of Monterrey and between several protuberances of rock folded into the shape of islands. One of these is the Sierra Las Mitras, a state nature reserve established in 2000. The mountain ridge rises approximately 1,500 meters (4,900 ft) above the city and provides a refuge for wildlife. As conditions become colder and wetter with higher elevations, the vegetation transitions from cacti and thorn bushes on the lower rocky slopes to oak and pine forests higher up on the ridges. Cerro de la Silla (Monte Silla or Saddle Hill) is another prominent element of the landscape, which contrasts with the built environment.
Near the city limit with the Sierra Madre Oriental is the University of Monterrey, home of the NASA Space Apps Challenge. This annual hackathon will take place in November 2026 in person and virtually at sites around the world. Participating teams use data from NASA and partner agencies to address challenges in fields such as software development, astrophysics, space exploration and agriculture.
Astronaut photograph ISS075-E-70481 was acquired on August 26, 2026 with a Nikon Z9 digital camera with a focal length of 400 millimeters. It is provided by the ISS Crew Earth Observation Facility and the Earth Sciences and Remote Sensing Unit at NASA Johnson Space Center. The image was taken by an Expedition 75 crew member. The image was cropped and enhanced to improve contrast and lens artifacts were removed. The International Space Station Program supports the laboratory as part of the ISS National Laboratory to help astronauts take photographs of Earth that will be of great value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at NASA/JSC Gateway to Astronaut Photography of Earth. Story by Lindsey Doermann.
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