NASA’s Jupiter Probe Could Snag First-Ever Sample From an Interstellar Comet

As interstellar comet 3I/ATLAS hurtles through the inner solar system, scientists are using every tool in their arsenal to learn as much about it as possible. Soon, they may have a once-in-a-lifetime opportunity to sample material directly from the comet’s ion tail.

Two European researchers have determined that NASA’s Europa Clipper probe could pass through 3I/ATLAS’s ion tail in a matter of weeks. Their findings, which have yet to undergo peer review and are currently available on the preprint server arXiv, indicate that the probe has a chance of intercepting the stream of charged particles between October 30 and November 6.

Such an event would provide a rare opportunity to sample material from a comet that hails from beyond our solar system. “We have virtually no data on the interior of interstellar comets and the star systems that formed them,†co-author Samuel Gran, a postdoctoral researcher at the Finnish Meteorological Institute, told Space.com.

“Sampling the tail in this way is the closest we can currently get to a direct sample of such an object, and thus a different part of the galaxy,†he said.

A serendipitous alignment

3I/ATLAS’s tail has been growing since astronomers first discovered the comet in early June. That’s because it’s been streaking toward the Sun, causing its icy core to heat up and release more gas and dust.

Meanwhile, Europa Clipper is on its way to Europa, the fourth largest of Jupiter’s 95 moons. This probe is designed to conduct a detailed study of Europa to determine whether there are places below its icy surface that could support life. To that end, it’s equipped with several instruments that could also prove useful for analyzing 3I/ATLAS’s ion tail.

This stream of charged particles blows directly away from the Sun, propelled by solar wind. Grant and his colleague Geraint Jones, a project scientist at the European Space Agency and principal investigator of the Comet Interceptor mission, used their “Tailcatcher†computer program to predict the likelihood of Europa Clipper crossing the ion tail.

According to their calculations, the probe could intercept some “packets†of solar wind carrying charged particles from 3I/ATLAS’s tail. Still, there are several variables that could stand in the way of detecting them.

A long shot with a big payoff

The instruments Europa Clipper would need to use are currently inactive as it cruises toward Jupiter. Amid a government shutdown, it’s not clear whether NASA will be able to boot them up in time. Secondly, the solar wind would have to blow in the right direction at the right strength to avoid missing the probe entirely or failing to deliver the heavier ions to it.

3I/ATLAS will reach perihelion—its closest approach to the Sun—on October 29. That means its tail will be broadest the day before the crossing window opens. This could increase the chances of Europa Clipper detecting some of the comet’s ions, but again, several other pieces of the puzzle will need to fall into place as well.

If the probe does manage to encounter 3I/ATLAS’s ion tail, this would be “the first direct immersion in material from an interstellar object†for any spacecraft, according to Grant and Jones. Even if Europa Clipper can’t directly measure the ions themselves, magnetic field draping and shock signatures could reveal the presence and structure of the ion tail, they say.