The interstellar comet 3I/ATLAS has recently passed its closest point to the Sun, unveiling intriguing chemical signatures, including nickel vapor and water. This rare celestial visitor offers scientists a unique opportunity to explore the chemical makeup of a body from another star system.
3I/ATLAS reached its perihelion on October 29, 2025, coming within approximately 1.356 astronomical units from the Sun. This close encounter activated the comet, causing its tail to become more pronounced and structured, as observed by facilities such as the Gemini South Observatory. The intense heat from the Sun vaporizes the comet”s ice and dust, leading to these observable changes.
However, the real excitement stems from the spectroscopic measurements conducted on the comet”s coma. These analyses revealed the presence of nickel vapor, a finding that is rare among comets in our Solar System, which typically contain lighter compounds and abundant water ice. The detection of a heavier element like nickel suggests that 3I/ATLAS may have originated in a star system with a different elemental composition than that of our own.
In addition to nickel, measurements also identified cyanogen (CN) gas, further indicating that 3I/ATLAS represents a pristine sample of material from a foreign planetary system. This supports theories regarding planetary formation around stars outside our Solar System.
The comet is also proving to be a significant source of water. The Neil Gehrels Swift Observatory detected hydroxyl radicals (OH), confirming that 3I/ATLAS is actively releasing water ice. Interestingly, this activity is occurring even at considerable distances from the Sun, reinforcing the notion that the comet exhibits dynamic behavior rather than being a mere inert rock.
NASA has assured that 3I/ATLAS poses no threat to Earth, as it will pass by at a safe distance. The comet”s trajectory indicates it is on a one-way trip, with an eccentric orbit suggesting it is not gravitationally bound to the Sun. After this singular encounter, it will exit our Solar System.
Visibility of the comet from Earth is limited, but scientists are preparing for two important observation opportunities. On November 3, 2025, spacecraft positioned near Mars and Venus will observe the comet from approximately 97 million kilometers away. The final chance for observation will be on December 19, 2025, when 3I/ATLAS will make its closest approach to Earth at roughly 1.8 astronomical units.
These observations are crucial, as they provide a rare glimpse into materials from another star system, aiding scientists in refining their understanding of planetary formation processes beyond our Solar System.
