Impact risk from the circumsolar dust ring on Venus’s orbit

Context . A circumsolar dust ring on Venus’s orbit was discovered following observations by the Helios spacecraft and then confirmed thanks to observations by STEREO and the Parker Solar Probe. The impact risk it poses needs to be evaluated for any spacecraft crossing the ring. Aims . This study aims to provide a basic model of the dust ring in terms of the distribution of particles (including size distribution) and the density of the ring and orbits and to deduce a first estimation of the impact risk to spacecraft crossing the ring. This impact risk is based on impact flux as well as the direction and speed of impacting particles. Methods . We seek to describe the orbits of dust particles in the ring. We explored two ways to generate initial conditions of particles in the ring: one that involves many assumptions and another that is more reliable. We integrated the second set of orbits for 6000 years and studied their evolution. We then selected particles still inside the ring after this integration and used the orbits to compute the impact risk for a spacecraft chosen as an example, BepiColombo. Results . We demonstrate that the dust ring will persist over the next 6000 years, extending radially and perpendicularly to the Venus orbital plane because of close encounters with Venus and because of non-gravitational forces. We show that particles tend to accumulate at Venus’s orbit, but along its orbit, the variations in density are negligible. We computed the number of particles we expect to find in the ring for radii between 2 μm and 2 cm (i.e. for masses between 10 −2 kg and 10 −14 kg). The size distribution of these particles is based on the interplanetary dust model IMEM2. Using the particles still inside the ring at the end of the integration, we computed the impact flux on BepiColombo due to the ring and show that it is of a similar level as the interplanetary dust background. Even though the impact flux is not negligible, it is low enough to be considered a very minor threat to spacecraft following an orbit similar to BepiColombo. Finally, we computed the velocity and direction of particles impacting BepiColombo and show that these results are not concerning. Conclusions . We thus conclude that the dust ring is not a major threat to spacecraft following trajectories similar to BepiColombo. This model should be updated in the future with any new data on the ring, as such data are severely lacking at the moment.