A once-in-a-lifetime comet flyby is heading toward Mars

Space · Published 9 October 2026 Swipe more like this →

In short: Comet Siding Spring is preparing for an incredibly close encounter with the Red Planet. Passing within 88,000 miles of Mars, this event offers scientists an unprecedented chance to study the comet and observe how its passage might impact the Martian atmosphere.

On October 19, comet C/2013 A1—also known as Siding Spring—will perform a rare flyby of Mars. This proximity is remarkable; the comet will pass within approximately 88,000 miles (139,500 kilometers) of the planet. To contextualise this gap, it is under half the distance from Earth to the moon, and under one-tenth the distance of any recorded comet passing Earth. This celestial event was highlighted during a recent press briefing held at NASA headquarters. Such close approaches are extremely rare for any known comet passing Earth. This upcoming event was discussed by a panel of experts during a briefing held on October 9.

To capture this event, NASA is utilizing a diverse array of assets. This includes the Hubble Space Telescope and various spacecraft currently orbiting or roving on Mars. Researchers hope to use this data to gain new insights into the composition of the comet and the specific effects its presence has on the Martian atmosphere. These observations will rely on both Earth-based and space-based assets. This includes various orbiting and roving missions currently active on the Martian surface.

The opportunity is considered a once-in-a-lifetime event for the scientific community. By observing the interaction between the comet and the Martian environment, astronomers can gather data that would otherwise be impossible to obtain, providing a unique window into the dynamics of our solar system.

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