In November, as a piece of orbital debris threatened the International Space Station (ISS), the crew of seven astronauts prepared for potential impact. A Russian spacecraft docked to the ISS ignited its engines for a brief five-minute burst, nudging the station's path and steering the massive laboratory to safety. Had the ISS not altered its course, the debris could have come within a close 2.5 miles (4 kilometers) of its flight path, as stated by NASA.

A collision could have been catastrophic, potentially causing depressurization and forcing the astronauts to make an emergency return to Earth. This near-miss is not an isolated incident; the ISS has had to perform such evasive maneuvers numerous times since its first occupation in November 2000. The risk of collisions is escalating annually due to the increasing number of objects in Earth's orbit. Space traffic experts have long warned about the growing congestion in space.

Collisions, explosions, and weapons tests have resulted in thousands of trackable pieces of debris, with possibly millions more that are beyond the reach of current detection technology. The risks are not just to astronauts but also to satellites and space-based technologies that are integral to our daily lives, including GPS, broadband, high-speed internet, and television services.

Dr. Vishnu Reddy, a planetary sciences professor at the University of Arizona, noted, "The number of objects we've launched into space in the last four years has increased exponentially, leading us towards a situation we've always feared." This situation is known as the Kessler Syndrome, a hypothetical scenario named after American astrophysicist Donald J. Kessler.

His 1978 paper outlined a chain reaction where space debris triggers a cascade of collisions, eventually clogging Earth's orbit with so much junk that satellites become inoperable and space exploration grinds to a halt. While opinions vary on the current risk level and the point of no return for space congestion, there is a general consensus among scientists and space traffic experts that space traffic is a grave issue that urgently needs to be addressed.

Since the beginning of spaceflight in 1957, there have been over 650 fragmentation events, including accidental satellite collisions, unexpected spacecraft explosions, and debris-spreading weapons tests from various nations. The last major accidental collision occurred in 2009 when a defunct Russian satellite collided with an active U.S. communications satellite, creating nearly 2,000 pieces of debris larger than 4 inches (10 centimeters) and thousands of smaller fragments. Smaller-scale events are also frequent, with one recent incident involving a U.S. Air Force weather satellite breaking apart and creating over 50 new pieces of debris.

For satellite managers, space congestion is a nightmare, with operators often receiving multiple daily alerts about potential collisions. Space situational awareness, which involves tracking potential close encounters between objects, is limited by the ability to track objects larger than a tennis ball. Smaller debris, which can still pose significant threats due to their high orbital velocities, often goes undetected.

The cascading effect of collisions in space is unclear, with different regions of Earth's orbit having varying levels of congestion and risk. Low-Earth orbit, which is the most crowded, is home to crewed space stations and numerous satellite constellations. A series of explosions in this region could endanger astronauts, halt launches, and destroy satellite technology.

However, there is a natural cleaning mechanism in low-Earth orbit, with objects at an altitude of around 300 miles (500 kilometers) naturally falling back to Earth or disintegrating in the atmosphere within about 25 years. This suggests that debris in this region is unlikely to threaten long-term space access. The situation is more dire at higher orbits, where debris can persist for centuries or even millennia. This is particularly concerning for geosynchronous orbit, which hosts high-value communications satellites.

The movie "Gravity" depicted the Kessler Syndrome, but while the film's events unfolded over 90 minutes, a real-life scenario would likely take years or even decades to develop. The number of objects tracked by the U.S. military has increased from about 23,000 to 47,000 since the film's release. Predicting the start of a ripple effect is challenging due to the lack of precise data on object locations and the influence of space weather on orbital trajectories.

The size and shape of space debris are also unknowns, making it difficult to model a Kessler Syndrome effect accurately. Scientists debate whether the phenomenon is already underway, with some suggesting that even if all rocket launches ceased, space collisions would still increase the number of objects in orbit. The term Kessler Syndrome itself is considered unhelpful by some, as it is not a clear or crisp concept.

What experts agree on is that the situation in orbit is problematic, and none believe that disaster can be certainly avoided. More likely, space debris will continue to proliferate, with potential economic damage in the process. Dr. Nilton Renno of the University of Michigan likens space debris to plastic in the oceans, emphasizing that space is a finite resource that requires careful management to prevent significant damage.

Preventing the proliferation of debris in Earth's orbit involves two main considerations: cleanup technology and regulation. Efforts like the European Space Agency's Drag Augmentation Deorbiting Subsystem (ADEO) are in development to remove debris from orbit, but these methods are experimental and costly. Regulation is another key area, with ongoing efforts to establish international guidelines and national laws to prevent irresponsible behavior in space.

The United Nations' Pact for the Future is a step in this direction, but it lacks enforcement mechanisms. Individual nations, particularly the United States, are urged to take a leadership role in adopting laws for space stakeholders to mitigate the growing threat of space debris.