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A comet approaching the sun from the outer solar system might sweep a trail of dust particles over the planet Venus when it swings into the inner reaches of our planetary neighbourhood this December.

On 18 December, Comet will zip past Venus at what is, in astronomical terms, a hair鈥檚-breadth distance of just 4.3 million kilometres. As Venus continues on its orbital path, it will move through a swathe of space close to where the comet was about 72 hours earlier.

Computer modelling suggests this region could contain dusty material that has been thrown off C/2021 A1 as it moves through space and that could now be getting swept along in the icy object鈥檚 wake.

鈥淭his is the closest comet encounter to Venus on record in at least the last 50 years or so,鈥� says at the California Institute of Technology, who has led a study of the event by a group of researchers in the US.

Although no one knows for sure if there really are dust particles travelling in the darkness behind the comet, any that are in the right place will rain down on Venus, creating meteors in the planet鈥檚 skies. If rarer, exceptionally bright meteors called bolides materialise, it may be possible for Earth-based telescopes to image those fireballs as flashes on Venus鈥檚 nightside.

That would be a challenging observation, however, says Zhang, as there is a narrow observing window and researchers would have to contend with interference from the light scattered off the pearly-white cloud tops on Venus鈥檚 dayside, which would be partially in view from Earth.

Another option is Japan鈥檚 Akatsuki spacecraft, which is orbiting Venus, although its instruments might not be sensitive enough to pick up signs of any meteors that do occur.

On Earth, we may get to glimpse C/2021 A1 in the December night skies, perhaps as a fuzzy dot of light among the stars.

鈥淭he comet will be observable from the northern hemisphere toward the end of the year and, according to current predictions, [it] might be visible to the naked eye,鈥� says , a comet researcher at the University of Edinburgh, UK. 鈥淚t won鈥檛 be exceptionally bright though.鈥�

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