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31/ATLAS and NASA have become the focus of intense scientific scrutiny after new tracking data revealed that the rare interstellar comet is accelerating and subtly changing course in ways that standard gravitational models cannot fully explain.  As 31/ATLAS races through the inner solar system and prepares to head back into deep space, NASA scientists say the object has turned into a real-time experiment in comet physics, interstellar materials, and planetary defense.

NASA Detects a Puzzling Acceleration

According to NASA’s latest tracking data, interstellar comet 3I/ATLAS—formally classified as Comet 31/ATLAS in some coverage—has picked up speed after passing its closest point to the Sun. The increase is not trivial. Measurements show the comet’s velocity climbed to roughly 244,000 kilometers per hour, with some analyses translating that figure to about 152,000 miles per hour as it continued outbound. What caught scientists off guard is that gravity alone does not appear to explain the change. NASA’s databases show that after perihelion, the comet not only sped up but also diverted slightly from its predicted path, forcing astronomers to refine their models. The agency describes the effect as a small but measurable non-gravitational acceleration—steady, persistent, and scientifically significant.

What Makes 31/ATLAS Different From Ordinary Comets

From the moment it was discovered, 31/ATLAS stood apart from familiar comets that originate in the Sun’s distant Oort Cloud. This object arrived on a hyperbolic trajectory, meaning it is not bound to the Sun’s gravity and will never return once it leaves the solar system. As NASA explains in its 3I/ATLAS Facts and FAQs, the “3I” designation marks it as only the third known interstellar object ever detected passing through our neighborhood, following 1I/ʻOumuamua in 2017 and 2I/Borisov in 2019. Unlike long-period comets, which follow looping elliptical paths, 31/ATLAS came from the broader Milky Way and is now heading back there—making every observation a once-in-a-lifetime opportunity.

NASA’s Leading Explanation: Solar-Driven Outgassing

Despite speculation swirling online, NASA researchers say the most likely explanation for the comet’s acceleration is well understood in principle: outgassing. As 31/ATLAS swung close to the Sun, intense heat warmed its surface, causing frozen gases to vaporize and blast outward in jets. Those jets act like tiny thrusters, producing a continuous push that adds speed and nudges the comet off a purely gravitational track.