US–Indian space mission maps extreme subsidence in Mexico City | Hacker News Reader

US–Indian space mission maps extreme subsidence in Mexico City

phys.org

223 pointsleopoldj73 comments

Like the article hints at, some of the particular strengths of this new measurement:

- frequent revisit, so can track even sub-monthly changes

- the L-band radar is at a wavelength (24cm) that penetrates vegetation canopy, removing a confounder from the measurement

- excellent spatial resolution that is relevant to urban scenes

The data volume is exceptionally high and required a lot of engineering effort. All radars are demanding, but this one was a new high-water mark.

(https://www.earthdata.nasa.gov/news/now-that-nisar-launched-...)

> but this one was a new high-water mark.

Pun fully intended, I'm sure.

I wouldn't trust that graphic at the top of the article to be very accurate. It has an obvious acquisition footprint that was not resolved in processing. Those WNW-ESE stripes should've been resolved before publishing by ground-truthing the stripes using benchmarks established inside the mapped area so that the end result wouldn't suggest higher/lower subsidence along tracks than seen on parallel offset from tracks. That's just sloppy.

The striping can have multiple sources so they need to study why there is an obvious footprint and then make the appropriate corrections.

So, perhaps a dumb question, but the article mentions that 14 steps have been added to the base of the Angel of Independence monument, and the Wikipedia article mentions the same things:

> Originally, nine steps led to the base, but due to the sinking of the ground, an ongoing problem in Mexico City, fourteen more steps have been added.

So why didn't the monument itself also sink? Does it have piles going down to bedrock or something?

Angels don't sink, they rise! :)

Depending of what stories you want to reference with this: Lucifer, Belial, Beelzebub all did not 'rise'.

Surely The Angel Of Independence must ascend, no? :)

I don't know the actual Christian theology, but at least in modern popular interpretations, Lucifer is the Angel of Independence, so that would suggest no!

Probably depends on your frame of reference. Since we don't know where they started or where they are today it seems plausible that, relative to our own positions they may indeed have appeared to rise even though the text references state that they descended. We have no idea whether we might go up to heaven and down to hell or just across to them. We do know that everything in our universe is in motion and has been for a long time so it could be true that today we have to rise to get to both places if in fact either of them exist at all.

Useless trivia, but lucifer means “light bringer” in Latin (translation from the Greek phosphoros).

Also known as the morning star, also known as Venus.

There’s also the nocturnal / sunset aspect of Venus, noctifer/hesperus, so the evening star.

It all ebbs and flows so I guess everyone is right:)

(Also this not a uniquely Roman or Greek invention ofc)

One man's useless trivia is another man's ideas for a project name :).

Also from wikipedia: ... "The commission determined that the foundations of the monument were poorly planned, so it was decided to demolish the structure."

So yes, it has an engineered foundation, a double-engineered foundation. The roads around it almost certainly do not. So it is plausible that the monument is not sinking as quickly.

thousands of wooden piles to create a foundation with the first one even failing and the foundation being reconstructed

http://www.mexicomaxico.org/ParisMex/resumen.htm

"Objective:

NISAR is the first of its kind mission, jointly developed by ISRO and NASA. It is an L and S-band, global, microwave imaging mission, with capability to acquire fully polarimetric and interferometric data.

The unique dual-band Synthetic Aperture Radar of NISAR employs advanced, novel SweepSAR technique, which provides high resolution and large swath imagery. NISAR will image the global land and ice-covered surfaces, including islands, sea-ice and selected oceans every 12 days.

NISAR mission’s primary objectives are to study land & ice deformation, land ecosystems, and oceanic regions in areas of common interest to the US and Indian science communities.

NISAR mission will help to measure the woody biomass and its changes track changes in the extent of active crops understand the changes in wetlands’ extent map Greenland’s & Antarctica’s ice sheets, dynamics of sea ice and mountain glaciers characterize land surface deformation related to seismicity, volcanism, landslides, and subsidence & uplift associated with changes in subsurface aquifers, hydrocarbon reservoirs, etc.

Spacecraft Configuration

The Spacecraft is built around ISRO’s I-3K Structure. It carries two major Payloads viz., L & S- Band Synthetic Aperture Radar (SAR).

The S-band Radar system, data handling & high- speed downlink system, the spacecraft and the launch system are developed by ISRO. The L-band Radar system, high speed downlink system, the Solid-State Recorder, GPS receiver, the 9m Boom hoisting the 12m reflector are delivered by NASA.

Further, ISRO takes care of the satellite commanding and operations, NASA will provide the orbit maneuver plan and RADAR operations plan.

NISAR mission will be aided with ground station support of both ISRO and NASA for downloading of the acquired images, which after the necessary processing will be disseminated to the user community

The data acquired through S-band and L-band SAR from a single platform will help the scientists to understand the changes happening to Planet Earth."

https://www.isro.gov.in/Mission_GSLVF16_NISAR_Home.html

Nice; thanks for the link which lists the essential technical details.

This is a great example of how two premier research organizations from different countries can cooperate together for everybody's benefit.

ISRO on International Cooperation - https://www.isro.gov.in/InternationalCoOperation.html

The amount of subsidence is quite dramatic, up to 25 cm per year!

What are the practical consequences of this today, and what is being done to remedy this?

They are clearly not doing enough to remedy this; The only real solucion is to stop pumping the ground water, like I believe Japan did.

Miami has a similar issue, doesn't it?

so does Jakarta and few other cities in the world.

Due to construction not ground water problem. Mostly building load and construction induced.

> What are the practical consequences of this today

Infrastructure degradation. Think overpass collapses or metro rail lines being misaligned.

> what is being done to remedy this

Not enough. CDMX faces the issue of multiple political entities with varying power making management difficult.

A lot of the subsidence happens in informal settlements [0] due to a mixture of political populism (no one would dare demolish an informal settlement and piss off voters).

Beijing used to have a similar issue, but a mixture of hukou, mass evictions, and mass demolitions helped alleviate the issue.

[0] - https://penniur.upenn.edu/uploads/media/02_Gutierrez.pdf

We can also see it play out in other countries, that had solar water pumping for the last ten years, like afghanistan. In the end stage- its water wars with neighbours like Pakistan or Iran.

Just as a fun fact, here are some images of the extent of subsidence (due to groundwater pumping for agriculture) in the California Central Valley: https://www.usgs.gov/centers/land-subsidence-in-california/m...

Note in particular the last one, which is a classic. Roads, buildings, and all underground infrastructure is affected. As well as anyone else who uses that groundwater, as well as future users - because come groundwater reservoirs do not recover, the compaction is permanent.

The San Joaqin Valley picture is astounding!

https://www.usgs.gov/media/images/land-subsidence-san-joaqui...

I don't even see how buildings can survive that actually... (unless it's happening very evenly)

Cloudflare: verification rejected. Accessing from Japan.

Thank you very much, Cloudlare.

same in Australia

same in india

From India, verification passed through

From India as well. Verification passed

Same in Vietnam. Just refresh the page. It’ll get you through.

Same in United States. Sigh.

Rejected in the US with a google fiber IP.

just reload. I got the same message, accessing from US, goes away on refresh.

For the uninitiated, ISRO -> Indian Space Research Organization

The way that this article is written reads like American propaganda. This is already being done, and has been done for a long time, including at the same or better temporal and spatial resolution. NISAR is genuinely cool, do I don't know why they felt the need to write this way. The new capabilities are mainly being able to do this in highly vegetated areas. In urban areas, like mexico city, this is literally 'intro to SAR' stuff.

Do you have any sources or even hints of sources that I could search for to back up the claim that this has been done for a long time?

For example this: https://www.sciencedirect.com/science/article/abs/pii/S00344...

Search for 'land subsidence insar mexico'

"Do you have any sources or even hints of sources"

I've been doing this as an amateur geologist for almost 2 decades using Google Earth and various data layers I can find on the internet.

NISAR is a realization of InSAR and SweepSAR techniques but done with dual radar frequencies with higher-frequency monitoring and precision.

Technical details from ISRO - https://www.isro.gov.in/Mission_GSLVF16_NISAR_Home.html

In parts of Central Valley CA, there's been over 30 ft / 9m of subsidence from ground water extraction over several decades. (30 cm/y) Lone pipes and drains that previously sat at ground level tower over the land.

I get that the article is primarily about the satellite capabilities, but it's rather annoying it doesn't mention what the future impact of the subsidence might be.

I think that it’s quite responsible not to speculate on something they’re not an expert on.

It’s exactly the sort of news bite that catastrophists glom onto.

This is responsible journalism.

They could just call a geologist and ask, or cite some published works on the topic. It's not responsible, it's lazy.

This is a phys.org "article". They're usually just rehashed press releases, and this one is particularly bad - it's literally just the NASA press release with the last 2 paragraphs chopped off. https://www.nasa.gov/missions/nisar/us-indian-space-mission-...

> I think that it’s quite responsible not to speculate on something they’re not an expert on.

"Recent satellite maps show Mexico City getting closer to hell at alarming rate"

Nor does it say how much subsidence the satellite documented.

There's this under the picture.

> New data from NISAR shows where Mexico City and its environs subsided by up to a few centimeters per month (shown in blue) between Oct. 25, 2025, and Jan. 17, 2026

The labels on the map were also confusing, and at first because of the relative positioning of the texts identifying the airport and the angel I thought up was East and not North, although a closer inspection made things clearer (and yes, up is North).

It breaks water lines which increases the water problem even faster. On one side because its expensive to fix and on the other side because small leaks lead to massive water losses you don't find fast or easy.

Also broken mains lead to sinkholes: https://www.bbc.com/news/videos/cj9zex1r3kjo

There are also abandoned mines under parts of the city which also contributes to hazardous conditions.

I really can't believe that an issue discovered in 1925 still isn't solved. A kind of issue which wont take a Nobel prize to be solved. This is sad.

What solution? The earth is constantly moving and churning. The article states the city is built on an aquifer.

Mexico City was built on top of a lake that was dried to facilitate the expansion of the city.

> What solution

The nobel prize winner hopefully figures that out

Many, many problems have good practical solutions that are politically impossible to implement.

All due to some kind of game-theoretic "dilemma", like a coordination problem, collective action problem, prisoner's dilemma, principal-agent problem, tragedy of the commons.

Mexico City’s water stress is complicated by the fact that it sits 2240 meters above sea level on a giant plateau surrounded by mountains, so the normal solution of pumping water from somewhere else is a lot more expensive.

For those unfamiliar, why is this an issue?

A lot of regions in the city rely on gravity to move water out of them. Floods have both increased in quantity and magnitude in recent years. If the city keeps sinking, more water will move in instead of out. Some areas of the city might become perma-flooded in a decade or two.

This is a very serious situation with no obvious solution to it.

Uh, you know, from the original source - Nasa (2 points, 2 days ago) https://news.ycombinator.com/item?id=47970672

Real shame this re-report made the SCP

Excessive groundwater extraction and urban development could be reasons for this. But these are common practice in almost all of the modern world, so why is this only showing up in Mexico City.

There must be other contributing factors too.

Mexico city was built on top a dried lake. It is really fascinating stuff, I would highly recommend to look it up. Ancient farming technology, floating islands, any nerd is gonna love it.

You can see evidence of subsidence in the rest of the developed world as well: SAR interferometry is sensitive enough to pick up the minimal amount of building movement from building Crossrail in London. It's just this article focuses on Mexico City, where it's dramatic

Mexico City (Tenochtitlan) used to be a city build on a lake, partly on an island, partly on some kind of static rafts / floatting gardens (chinampas).

It’s not only Mexico City. This is happening in Jakarta, the Central Valley of California, Beijing, really anywhere with excessive groundwater extraction.

It is just most people pay attention to CDMX because it is a very large 20M+ city with a lot of American and European tourists, and it is happening quickly to the point where you can see it with the naked eye.

Reply on news.ycombinator.com