3I/ATLAS, an interstellar comet, will pass Earth at its closest on December 19, 2025, at a distance of about 1.8 astronomical units (270 million kilometers or 168 million miles), which means it will not come very close to Earth. Its closest approach to the Sun (perihelion) will be on October 29, 2025, at a distance of 1.36 AU, between the orbits of Earth and Mars. It will pass closer to Mars around October 3, 2025, at about 0.19 AU (30 million kilometers), but not near Earth. The comet poses no threat to Earth during this passage.