The Europa Clipper spacecraft, NASA's probe heading to Jupiter, is predicted to soon fly through the ion tail of the interstellar comet 3I/ATLAS, providing a unique opportunity to directly sample material from a body originating outside our solar system.
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Comet 3I/ATLAS and the Europa Clipper Encounter
The interstellar comet 3I/ATLAS, only the third-known interstellar visitor to pass through our solar system, is nearing its closest approach to the Sun (perihelion). As it does, the heat causes it to release gas and dust, forming two distinct tails:
Dust Tail: The most prominent tail, which follows the comet's orbital trajectory. No spacecraft is currently positioned to sample it.
Ion Tail: Formed from charged particles (ions) ripped from the comet's material and swept away from the Sun by the solar wind. This tail always points directly away from the Sun.
European researchers, using a computer program called Tailcatcher, predicted that the Europa Clipper—currently in cruise mode on its journey to Jupiter—will pass through the comet's ion tail between October 30 and November 6. This is a highly fortuitous alignment.
What Could This Reveal?
If the Europa Clipper can activate its instruments to make the measurements, this fly-through will offer the closest scientists can currently get to a direct sample of an interstellar object. The data could reveal new insights into the comet's composition and, by extension, the star system from which it originated.
"Time Capsule" Material: Comets are often described as "time capsules" because they seal in material from their formation billions of years ago. By studying 3I/ATLAS, scientists can gain insights into a different part of the galaxy.
Compositional Differences: The charged particles collected would be compared to those from comets formed within our own solar system. Cometary ions can be distinguished from the solar wind by their chemical abundances, as they contain significant amounts of heavier species like water-group ions, unlike the Sun's proton and helium-dominated solar wind.
Challenges to a Successful Measurement
Despite the opportunity, a number of factors could prevent Europa Clipper from successfully detecting the charged particles:
Instrument Activation: Europa Clipper is currently in cruise mode, and not all instruments are activated.
Solar Wind Conditions: A successful detection relies on the solar wind flowing in the correct direction and being strong enough to carry the comet's heavier ions all the way out to the spacecraft, which is over 186 million miles (300 million kilometers) from the Sun.
Even if this opportunity is missed, the ability of the Tailcatcher program to predict these alignments increases the chances of future missions, like the European Space Agency's Comet Interceptor, being able to study an interstellar visitor up close.