Biggest Space Discoveries in 2025: From New Comets and Black Holes to Sign of Life on Mars

2025 was an exciting year for astronomy, with reports of new exoplanets close to our Sun, an interstellar comet travelling through our Solar System, and claims of extinct life on Mars, among other things. Unusual "leopard spots" on Martian rocks were identified by researchers as potential biosignatures of extinct microorganisms. Comet 3I/ATLAS, meanwhile, is now only the third known interstellar space object. Strong new observatories went online. Here is a summary of some of the most remarkable cosmic discoveries of 2025.

Strange visitors and new neighbours

As reported in numerous news reports, astronomers had a blockbuster second half of 2025. They spotted Comet 3I/ATLAS — only the third known interstellar object – racing through our Solar System at a record speed. Meanwhile, surveys of nearby stars turned up new worlds. In March, astronomers confirmed four small planets orbiting Barnard's Star (largest, approximately one-third Earth's mass). By August, observations with the James Webb Space Telescope yielded strong evidence of a Saturn-mass planet around Alpha Centauri A. These findings greatly expanded the inventory of nearby planets.

Cosmic mysteries and new horizons

One surprise came from Mars: Perseverance images revealed ‘leopard spots' on a rock in Jezero Crater that may be fossil clues to ancient microbes. At the other extreme, astronomers reported an ultra-massive black hole weighing 36 billion times the Sun at the heart of a distant galaxy – far heavier than our Milky Way's. Finally, the Vera C. Rubin Observatory in Chile achieved first light and captured stunning images of galaxies and nebulae, promising a deluge of future discoveries.