On July 1, 2025, the Asteroid Terrestrial-Impact Last Alert System (ATLAS) in Chile detected a newly arrived comet into our solar system. This comet has been designated 3I/ATLAS, marking it as the third interstellar object that humanity has observed traversing our solar system. The earlier two interstellar entities identified were 1I/’Oumuamua (recognized in 2017) and 2I/BORISOV (identified in 2019). It appears that 3I/ATLAS shares similarities with 2I/BORISOV in terms of its icy makeup. Beyond this, little is known about this new interstellar arrival. Scientists are hurrying to study 3I/ATLAS and gather as much information as possible, as its current path and velocity suggest it will exit our solar system by year’s end.
Its closest approach to our sun is anticipated in late October 2025, at which point solar heat will likely cause some of its ice to vaporize, potentially resulting in a prominent cometary tail rich in vapor and dust. Presently, this comet features a faint coma, which is the surrounding cloud of gas and dust enveloping its nucleus. However, this situation may alter as it nears the sun. An additional intriguing detail is that 3I/ATLAS will cross Mars’ orbit, leaving us uncertain about the outcome of that encounter.
The concern surrounding the fact that ATLAS was the first to identify this comet has raised some alarms. The Asteroid Terrestrial-Impact Last Alert System is inherently defensive, developed to detect and alert us about comets, asteroids, or other celestial objects that might collide with Earth. Nonetheless, NASA confirms that this interstellar object will most likely not come close enough to our planet to pose any risk.
### What NASA has to say
The ATLAS observatory in Chile forms part of NASA’s early warning system, focused on identifying and characterizing all near-Earth objects (NEOs), with a specific emphasis on asteroids and comets that could potentially impact our planet. ATLAS operates a network of wide-field telescopes that continuously scan the night sky above Earth. While primarily structured for planetary defense against hazardous space objects, ATLAS can also identify non-threatening yet scientifically intriguing celestial entities. The telescopes involved in this defensive initiative are stationed across various observatories worldwide (including locations in South Africa, California, and Chile), offering comprehensive global coverage of the night sky.
Naturally, upon the initial discovery of 3I/ATLAS, the immediate focus was on determining its trajectory and speed. It was established that this comet travels at a velocity of 137,000 miles per hour (61 km/s), with the nearest point of approach to Earth being 1.8 astronomical units (170 million miles, or 270 million kilometers) away. NASA has ultimately determined that 3I/ATLAS presents no danger to our planet.
With that in mind, the most fascinating established fact about this interstellar traveler is its age. Based on its current trajectory, scientists have concluded that 3I/ATLAS originated from a region of the Milky Way that predates our solar system; thus, it could potentially be older than 4.6 billion years. The estimation suggests that 3I/ATLAS is approximately 7 billion years old, making it the oldest comet recorded by humans to date.
### Could it be an alien probe?
Despite the limited knowledge surrounding 3I/ATLAS, several captivating theories exist regarding this interstellar visitor. Astrophysicist Abraham Loeb from Harvard, along with colleagues from the UK’s Initiative for Interstellar Studies, Adam Hibbert and Adam Crowl, theorize that this interstellar object might not be a comet but rather an alien probe sent from a distant location to survey Earth and its vicinity.
This isn’t the first occasion on which Loeb has proposed such an idea. In 2017, when Oumuamua was discovered, he suggested it could be an alien probe owing to its atypical shape, acceleration, reflectivity, and absence of trailing gases. While he hasn’t presented specific details regarding 3I/ATLAS, Loeb cautions that any interstellar object warrants investigation as a potential piece of alien technology.
Currently, there is no proof that 3I/ATLAS is anything other than an interstellar comet journeying through our solar system. The detection by ATLAS was fortunate, as it’s believed millions of similar objects traverse near or through our system without detection. Nevertheless, scientists like Loeb might not be entirely misguided; 3I/ATLAS is a distinctive interstellar comet, and it deserves closer scrutiny.
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