Webb reads the ice of a visitor from another star — and it looks familiar

Only three objects from beyond our solar system have ever been caught passing through it. Using the James Webb Space Telescope, a Southwest Research Institute-led team has now read the ice streaming off the third one, comet 3I/ATLAS. The grains are tiny — about a micron or smaller, a mix of water ice and dust — and the surprise is how familiar they look: their fingerprints resemble the icy worlds beyond Neptune in our own system. Lead author Dr Silvia Protopapa explains that as the comet warms, gas escaping from inside carries these grains out, and each grain holds clues to the conditions where the comet was born, around another star. The building blocks of planets, it seems, may follow similar recipes in very different kitchens.