Delivery of complex organic molecules to the system of Jupiter

Abstract

Complex organic molecules are key markers of molecular diversity, and their formation conditions in protoplanetary disks remain an active area of research. These molecules have been detected on a variety of celestial bodies, including icy moons, and may play a crucial role in shaping the current composition of the Galilean moons. Experimental studies suggest that their formation could result from UV irradiation or thermal processing of NH3:CO2 ices. In this context, we investigate the formation of complex organic molecules in the protosolar nebula and their subsequent transport to the Jupiter system region. Lagrangian transport and irradiation simulations of 500 individual particles are performed using a two-dimensional disk evolution model. Based on experiments with UV irradiation and thermal processing of CO2:NH3 ice, this model allows us to estimate the estimate the potential for the formation of complex organic molecules through these processes. Almost none of the particles released at a local temperature of 20 K (corresponding to ~12 AU from the Sun) reach the location of the system of Jupiter. However, when released at a local temperature of 80 K (~7 AU), approximately 45% of the centimetric particles and 30% of the micrometric particles can form complex organic molecules via thermal processing, subsequently reaching the location of the system of Jupiter within 300 kyr. Assuming that the Galilean moons formed in a cold circumplanetary disk around Jupiter, the nitrogen-bearing species potentially present in their interiors could have originated from the formation of complex organic molecules in the protosolar nebula.

Figures (5)

• Figure 1: Experimental conditions and results adapted from bossa_carbamic_2008, which serve as the foundation for our study. The figure depicts the products formed during the processing of NH$_3$:CO$_2$ ices, highlighting reactions driven by thermal processing (in red) and UV irradiation (in blue). Chemical pathways are influenced by the temperature condition $T > 80$ K and an accumulated irradiation dose $F_\mathrm{acc} > 4.32 \times 10^{19}$ photons.cm$^{-2}$. The percentages represent the relative abundances of the newly formed molecules.
• Figure 2: Two-dimensional temperature map of the disk after 280 kyr of evolution. The averaged trajectories of particles over this period, plotted along the $r$ and $z$ axes, are shown in white. The panels present the trajectories of particles with sizes of 1 cm and 1 $\mu$m, released at initial disk temperatures of 20 K (panels a and b) and 80 K (panels c and d). Green triangles indicate the initial positions of the particles, while green crosses mark their final positions. In each panel, the detailed trajectory of an individual particle is highlighted within the square on the right.
• Figure 3: Trajectories and irradiation conditions of selected individual particles, 1 cm (left column) and 1 $\mu$m (right column), released at 7 AU, with a PSN temperature of 80 K, during 290 and 280 kyr of PSN evolution, respectively. The particles were selected from those that succeeded in forming COMs and delivering them to Jupiter's orbit. The gray solid line shows the average accumulated irradiation, temperature, and trajectories of these particles, and the gray dotted line shows the corresponding standard deviation. Light and dark blue lines represent the accumulated irradiation, temperature, and radial trajectories of the particles that end up farthest and closest to the Sun, respectively. Top panels: Irradiation accumulated by these particles along their trajectory through the disk. Middle panels: Temperature encountered by the same particles, with temperature ranges for COM formation and destruction indicated by dashed horizontal lines, based on experimental data bossa_carbamic_2008. Bottom panels: Radial trajectories of the same particles, with the location of the Jupiter system marked by the horizontal line.
• Figure 4: Same as Fig. \ref{['fig:80K_COMs_trajectory']}, but for particles released at 12 AU (PSN temperature = 20 K), with simulation durations of 550 kyr (left) and 570 kyr (right). In this case, $\sim$2% of the 500 simulated particles of 1 $\mu$m form COMs and reach the formation region of the Galilean moons, while none of the 1 cm particles do. Thus, the left panel shows all the 1 cm particles released at 20 K.
• Figure 5: Radial trajectories of 1 cm (top panels) and 1 $\mu$m (bottom panels) particles released at 20 K (left) and 80 K (right). The mean trajectory is shown as a solid blue line, with the corresponding 1-$\sigma$ and 2-$\sigma$ dispersions represented by dashed and dotted blue lines, respectively. The median trajectory is shown in orange, while the green dotted lines indicate the innermost and outermost trajectories relative to the star.