JWST Reveals Varied Origins Between Jupiter's Irregular Satellites (2501.16484v1)

Abstract: We report observations of eight Jovian irregular satellites with JWST's NIRSpec instrument: Himalia, Elara, Pasiphae, Sinope, Lysithea, Carme, Ananke, and Themisto. Irregular satellite families, which are presumed to have formed via collisions, contain various Trojan-like and C-type-asteroid-like surfaces. We sample the three largest members of the Himalia satellite family, detecting the presence of complexed CO$_2$ and a unique absorption band from $\sim2.7-3.6\ \mu m$ whose character correlates with satellite size. The two largest irregular satellites, Himalia family members Himalia and Elara, contain ammoniated phyllosilicates that are not seen in the meteorite inventory. We propose that the Himalia parent body was heterogeneous and formed with materials similar to Ceres-like ammonium-bearing asteroids. Several small ($D\sim 10km$) irregular satellites closely track the colors and absorption bands of ``red'' Jovian Trojans, demonstrating that these compositions are retained amongst the products of collisions that occurred after Jovian capture. We report the first detection of aqueous alteration products in the retrograde satellite swarm, finding Ananke's 3 micron band to closely match phyllosilicates seen in C2 chondrites. Notably, objects with OH absorption features similar to the Trojan asteroid Eurybates are found in both the retrograde Pasiphae family and the prograde Himalia family, confounding a simple link between such materials and a single surface type. The irregular satellites appear consistent with some materials that experienced alteration from liquid water and others that did not. Consequently, Jupiter may have captured bodies that formed from different initial compositions, or bodies that experienced different levels of heating, driving differential alteration processes.

• The paper employs JWST NIRSpec to uncover significant compositional diversity and signs of aqueous alteration on Jupiter's irregular satellites.
• It identifies ammoniated phyllosilicates on Himalia and Elara, linking them to Ceres-like materials and distinct aqueous processes.
• Findings support Jupiter's capture of bodies from different solar regions, offering new insights into the planet's migrational and compositional history.

Analysis of Jupiter's Irregular Satellites Through JWST Observations

The paper titled "JWST Reveals Varied Origins Between Jupiter's Irregular Satellites" provides an extensive analysis of the compositional diversity of eight irregular satellites of Jupiter using JWST's Near Infrared Spectrograph (NIRSpec). The research focuses on the largest members of the Himalia group, potential compositional linkage among them, and the differentiation of surface materials among captured satellites.

Key Findings

1. Compositional Diversity and Aqueous Alteration: The paper reveals significant variation in the composition of Jupiter’s irregular satellites, reflecting complex origins. Himalia and Elara contain ammoniated phyllosilicates not common in the meteorite inventory, indicating a similarity to Ceres-like ammonium-bearing asteroids. These satellites exhibit significant signs of aqueous alteration.
2. Presence of Ammoniated Phyllosilicates: The detection of ammoniated clays particularly in Himalia and Elara suggests formation from materials comparable to those that formed Ceres. Himalia's surface shows another unique absorption band between 2.7-3.6 μm, correlated with its size, suggesting distinct levels or processes of aqueous alteration.
3. Surface Features Across Satellites: Smaller irregular satellites retain characteristic features akin to ‘red’ Jovian Trojans, indicating these compositions survived post-capture collisional processes. The satellite Ananke, within the retrograde population, also demonstrates a 3 μm band akin to phyllosilicates in C2 chondrites, suggesting affection by aqueous processes post-capture.
4. Complex Origins of Composition: The research supports the hypothesis that Jupiter captured bodies with varied compositions, ranging from those formed in different environments within the primordial Kuiper belt to aqueously altered ones. The spectra indicate that some satellites might have captured material from beyond the primordial asteroid and cometary regions near Jupiter.
5. Implications for Solar System History: The paper infers that irregular satellites are remnants from bodies that interacted with Jupiter over its history, proposing these could be a mix of primitive bodies once residing further from the sun than Jupiter. Such heterogeneity suggests a complex migrational history of these small bodies across the Solar System.

Implications

• Theoretical Implications: These findings support models of Jupiter’s migration and capture of outer solar system bodies. They correlate with theories suggesting the varied solar system formation environments where these satellites could have originated.
• Future Exploration and Research: By identifying specific mineralogies and compositions, this research lays the groundwork for further exploratory missions and cross-comparison with outer solar system bodies, facilitating a deeper understanding of early solar system dynamics and material exchange processes.
• Astrobiological Significance: The identification of ammonia and water-related minerals on these satellites has implications for the understanding of volatile delivery to the outer planets and potentially the Galilean moons, which might have seminal implications for life-supporting environments beyond Earth.

In conclusion, the paper delineates an advanced understanding of Jupiter's irregular satellites, using JWST observations to highlight the compositional complexity indicative of their varied histories and origins. These insights contribute significantly to the narrative of planetary formation and evolution in the outer solar system and underscore the potential roles these satellites play in broader astrophysical and astrobiological contexts.