Do mass satellite launches have potential impacts on Earth's atmosphere and ozone layer?

Hey, that's an excellent question, and it's on many people's minds. Simply put, the answer is: There are potential impacts, and this is precisely an area that scientists are currently very focused on and actively researching.

This issue needs to be looked at from two angles: how satellites get up there, and how they come down.

1. Launch Phase: What Do Rockets "Spew Out"?

Launching satellites into space requires powerful rockets. Rocket fuel combustion produces various exhaust gases, similar to car emissions, but with a more complex composition and a more direct impact.

• Black Carbon (Soot): Especially rockets using solid fuel produce a large amount of tiny black carbon particles. These particles are directly deposited into the stratosphere, tens of kilometers high (where the ozone layer is located). Unlike dust on the ground, they don't easily fall back down and remain suspended at high altitudes.

  • Drawback One: Atmospheric Heating. Dark substances absorb heat. These black carbon particles absorb sunlight, locally "warming" the stratosphere, which could disrupt atmospheric circulation.
  • Drawback Two: Ozone Depletion. More critically, the surface of these particles provides an excellent "breeding ground" for chemical reactions, accelerating reactions that deplete ozone.

• Chlorine: Similarly, some solid fuels (like those used by space shuttles) contain chlorine. Once released into the stratosphere, this substance is a "super weapon" against ozone; a single chlorine atom can destroy thousands of ozone molecules.

• Alumina: Solid rocket boosters produce large amounts of alumina particles upon combustion. Similar to black carbon, these small particles also provide sites for ozone-depleting chemical reactions.

Previously, launch frequencies were low, only a few dozen times a year, giving the atmosphere enough time to "self-heal." However, projects like Starlink now launch dozens of satellites at once, with dozens or even hundreds of launches per year. This is like new "wounds" appearing before old ones have healed, making the cumulative effect a cause for concern.

2. Re-entry Phase: What Do Satellites "Burn Up" Into?

Satellites also have a lifespan, typically 5 to 7 years. After their lifespan, most low-Earth orbit satellites are deorbited and burn up in the atmosphere, appearing like a shooting star.

Previously, we thought burning up meant they were gone, problem solved. However, recent research shows it's not that simple.

• Metal Particles: Satellites are primarily made of metals like aluminum alloys. When they burn up in the atmosphere at altitudes of 80-120 kilometers, these metals don't "disappear" but turn into extremely tiny metal oxide particles (e.g., aluminum oxide), which then remain in the upper atmosphere like dust for a long time.

• Potential Risks: Scientists have detected an increasing concentration of these metal particles in the stratosphere. These remnants from "artificial meteor showers" falling from the sky, like the particles produced during rocket launches, could also act as catalysts for ozone depletion. Imagine tens of thousands of satellites operating simultaneously in the future, with thousands deorbiting and burning up each year. This is equivalent to continuously "sprinkling metal powder" into the ozone layer.

In Summary

To use an analogy:

• Launches are like large trucks diligently transporting a pile of "small trash" (black carbon, alumina particles) upstairs (to the stratosphere).
• Re-entry is like people upstairs constantly throwing old appliances (decommissioned satellites) out the window, which shatter mid-air into finer "dust."

Whether "transported up" or "falling down," both processes are adding foreign substances to the stratosphere, a "room" that should ideally be clean.

The core issue lies in the "quantity." A single launch or a single satellite re-entry has a negligible impact. However, when constellations comprise thousands of satellites, rapidly iterating and updating every few years, the cumulative effect of this continuous "pollution" could have a significant impact on our fragile ozone layer and upper atmospheric environment.

Currently, this remains a cutting-edge scientific question, and scientists are urgently "catching up" with research to determine the exact extent of the impact. Nevertheless, this undoubtedly serves as a reminder: while enjoying the convenience brought by satellite internet, we must also consider its environmental cost.