NASA’s Europa Clipper spacecraft made valuable observations of the interstellar comet 3I/ATLAS. The comet became the third officially recognized interstellar object to enter the solar system in July.
The UVS instrument provided a unique perspective on interstellar comets at a time when observations from Mars or Earth were impractical or impossible.
“This opportunity to observe another target on its way to Jupiter was completely unexpected, so we’re excited,” said Dr. Curt Retherford of the Southwest Research Institute, principal investigator for Europa-UVS.
“Our observations provide a unique and nuanced view of comet 3I/ATLAS.”
What makes Europa Clipper’s observations unique?
Within a week of the comet’s discovery, analysts at NASA’s Jet Propulsion Laboratory (JPL) determined the comet’s trajectory through the solar system.
The Europa Clipper team quickly realized that the spacecraft could observe 3I/ATLAS in November, when observations from Earth were mostly hampered by the position of the Sun and observations from Mars were best.
During this time, Europa Clipper bridged the gap between Mars-based observations from late September and subsequent Earth-based observations.
Because the comet’s orbit passes between the Europa Clipper and the Sun, its favorable location allowed the UVS team to observe the comet from a unique perspective. Comets have a dust tail that follows them and a plasma tail that points away from the Sun.
Instruments aboard the JUICE mission reveal more details about an interstellar comet
Europa-UVS’s unusual sunward perspective provided a unique downstream view of the comet’s two tails, primarily from “behind” the tail, looking back toward the comet’s core and coma (the cloud of gas that surrounds the comet).
Additional data from the SwRI-led UVS instrument aboard ESA’s Jupiter Ice Moons Explorer (JUICE) complements these insights and simultaneously provides a more general anti-solar view of 3I/ATLAS.
Dr. Thomas Greathouse, co-principal investigator for Europa-UVS, commented: “We hope that this new perspective, and observations from assets on Earth and other spacecraft, will help us understand the shape of the tail more completely.”
discover the composition of comets
Europa-UVS detected signatures associated with oxygen, hydrogen, and dust, supporting the preponderance of data showing that comet 3I/ATLAS experienced high outgassing activity in the period immediately following its closest approach to the Sun.
“Europa-UVS is particularly good at measuring fundamental transitions from atoms and molecules,” Retherford said. “You can see gas being ejected from the comet and water molecules splitting into hydrogen and oxygen atoms.”
This capability will enable Europa Clipper to measure and analyze these atomic species with high precision, providing a deeper understanding of cometary processes and composition.
Why is this information important?
“Understanding the composition of interstellar comets and how these gases are likely to be ejected may provide a clearer picture of their origins and how they evolved during their journey from other parts of the galaxy to our solar system,” explained Dr. Tracy Becker, co-principal investigator of Europa-UVS.
“What chemical processes are occurring and how can we figure out the origin of comets in that star system? Were those processes similar to the way we believe the solar system formed? Those are big questions,” she concluded.
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