When you buy through links on our articles, Future and its syndication partners may earn a commission.A closeup of “leopard spots” on Mars seen by the Perseverance rover. | Credit: NASA/JPL-Caltech/MSSS2025 was an exciting year for astronomical discoveries. Scientists got the best evidence yet for past life on Mars, discovered an interstellar comet zooming through our solar system, found clues of possible nearby exoplanets, and much more. Here are eight of the most spectacular space stories from the past 12 months.1. A new interstellar cometThe highlight from the second half of 2025 was undoubtedly Comet 3I/ATLAS, which is only the third interstellar object to have been discovered cruising through our solar system.AdvertisementAdvertisementAdvertisementAdvertisementThe Chilean component of the Asteroid Terrestrial-impact Last Alert System spotted the interstellar interloper sneaking among the stars of the constellation Sagittarius on July 1, and it quickly became apparent that its trajectory was severely hyperbolic. Rather than orbiting the sun like comets native to our solar system do, it was just passing through — and it was moving faster than any comet ever seen. Its abnormally high velocity of 36 miles per second (58 kilometers per second) told us that the speedy object, which became known as 3I/ATLAS, had probably been wandering interstellar space and receiving gravitational nudges from nearby stars since before our solar system even existed.By September, 3I/ATLAS was moving behind the sun, making it impossible for Earth-based telescopes to track its movements until it reappeared in mid-November. Instead, NASA and the European Space Agency turned to their fleets of spacecraft that had better views of the comet during solar conjunction.So far, we’ve learned that 3I/ATLAS is a comet and that all of its features have been seen on comets before. Its chemistry is broadly similar to the solar system’s own comets, which is a profound discovery in its own right. There are a few differences, though — specifically, a slightly higher carbon-dioxide-to-water ratio, and a little more nickel than iron, which reflect the chemical composition of its star system of origin.Besides a regular comet’s tail, 3I/ATLAS has also sp …
