Phobos inches toward Mars—potentially forming a temporary ring in tens of millions of years

Mars’s inner moon Phobos is spiraling inward at about 1.8 centimeters per year due to tidal interactions; models suggest the moon’s weak interior could break apart in roughly 20–40 million years, spreading material into a temporary ring around Mars that might last from 1 million to 100 million years before debris either falls to the planet or disperses. Whether Phobos stays intact depends on its internal strength, with a stronger, more coherent interior potentially surviving closer to Mars while weaker material would disintegrate sooner.