NASA Captures Rare Interstellar Comet Observations

NASA's Europa Clipper spacecraft has captured important new data on the interstellar comet 3I/ATLAS using its Southwest Research Institute-led Ultraviolet Spectrograph, or UVS. In July, 3I/ATLAS became the third officially confirmed interstellar object known to enter our solar system.

The UVS instrument was able to observe the comet during a window when viewing from Mars and Earth was difficult or not possible. Dr. Kurt Retherford, the principal investigator for Europa-UVS, expressed excitement over the unexpected opportunity to view another target on the way to Jupiter.

The Europa Clipper, which launched in 2024, is set to reach the Jovian system in 2030, where it will orbit Jupiter and carry out 49 close flybys of the moon Europa. Less than a week after the comet was discovered, analysts at NASA's Jet Propulsion Laboratory mapped its path through the solar system, which allowed the Europa Clipper team to plan observations during a period with limited visibility from Earth and Mars.

Positioned between Europa Clipper and the Sun, the spacecraft had a unique vantage point to capture a downstream view of both tails of the comet. Comets typically exhibit a dust tail and a plasma tail, and this vantage point allowed for a 'behind-the-tails' perspective toward the comet's nucleus and coma.

Simultaneously, observations from the SwRI-led UVS instrument aboard the European Space Agency's Jupiter Icy Moons Explorer will provide an anti-sunward view, enhancing the scientific understanding of the tails' geometries.

Dr. Thomas Greathouse, co-deputy principal investigator of Europa-UVS, highlighted the hope of gaining a more complete understanding of the tails' structures. The Europa-UVS identified signatures of oxygen, hydrogen, and dust, supporting observations of high outgassing activity shortly after the comet's closest approach to the Sun.

Dr. Retherford noted that the UVS instrument is adept at measuring fundamental transitions from atoms and molecules. This capability allows for the observation of gases emitted from the comet, including water molecules breaking apart into hydrogen and oxygen atoms.

Dr. Tracy Becker, co-deputy principal investigator of Europa-UVS, stated that understanding the composition of the comet and the gases emitted can provide insights into its origin and evolutionary processes during its journey from elsewhere in the galaxy to our solar system.

This work raises significant questions regarding the comet's chemical processes and evolutionary history compared to those believed to have shaped our solar system. NASA's Jet Propulsion Laboratory manages the Europa Clipper mission for NASA's Science Mission Directorate in Washington, D.C., and the mission was developed in partnership with the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.