Comets tend to have two tails. One is known as the dust tail, and it tends to be more curved, while the other, known as the ion or plasma tail, is straighter, pointing away from the Sun. The tails can also be long, with ion tails often extending for hundreds of millions of kilometers. We have not seen the ion tail for interstellar comet 3I/ATLAS, but if it’s there, two spacecraft might soon cross it. The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.

The spacecraft in question are NASA’s Europa Clipper , going to the eponymous icy moon of Jupiter, and the European Space Agency’s Hera , which is travelling to the binary asteroid Didymos and Dimorphos, the site of the first-ever planetary defense demonstration when the DART mission purp

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