Bright bolides in Jupiter in 2020-2024: Improving estimations of impact rates on the Jupiter System

Jupiter is the largest and most massive planet in the Solar System. Because of its active and changing colored atmosphere, it is also the most popular target for amateur astronomers devoted to obtaining planetary images at high spatial resolution. Since 2010 several amateur astronomers have discovered intense flashes of light occurring in Jupiter’s atmosphere. These bright flashes are produced by the collision of objects of 5-35 m in diameter that impact Jupiter’s atmosphere at velocities higher than 60 km/s and release energies of the order of 10^15-10^16 Joules [1-3]. These energies are comparable to the energy released by larger impacts on the Earth, such as the Chelyabinsk impact in 2013. When observed from a distant point these bolides produce enough light to shine briefly for about 1-3 seconds as stars of apparent magnitude 3-7 that become observable with small telescopes. Up to December 2023, 13 such impacts flashes have been observed by amateur astronomers. One of the brightest impacts was discovered by a research team at Kyoto University devoted to search for such impacts [3-4]. This detection included observations in different filters that allowed to constrain a brightness temperature of about 8300 K. Additionally, a smaller impact flash created by an object of 1-4 m was observed by the Juno spacecraft in 2020 [5], providing a spectrum in the UV which results also in high brightness temperatures of 9600 K. These measurements of temperatures are very important, because calibrated light curves of impacts discovered by amateur astronomers require brightness temperatures to disentangle the luminous energy produced in the object, which allows to retrieve estimates of the mass of the objects. In recent years, several observers have been able to observe these impacts simultaneously using a variety of equipment sensitive to different spectral ranges, which agrees with these brightness temperature estimates.

Here we report on the characteristics of 3 impacts detected in 2020-2021 and 4 impacts observed in 2023, two of them observed on consecutive nights on December 28 and 29. Part of the enhanced frequency of these observations corresponds to the global collaboration DeTeCt (http://www.astrosurf.com/planetessaf/doc/project_detect.php), in which more than 250 individual observers monitor the planet frequently with an automatic detection software. This software alerts observers in case of positive detections and also provide statistics of the negative detections obtained. The DeTeCt collaboration has analyzed more than 343,000 video observations of the planet that together represent data equivalent to a full year of continuous observations. From this analysis we update our previous estimate [2] of the current impact rate in the Jupiter system. The new estimate does not differ significantly from our previous estimate of 10-60 bolide impacts in Jupiter for objects in the size range of 10-20 m in diameter. We explore the influence of these objects in the chemistry of the planet’s upper atmosphere and we examine the potential of the JUICE missions to observe fresh craters in Ganymede in its in-depth exploration of this Galilean moon in the 2030s.

References: [1] Hueso, Weslley et al. First Earth-based detection of a superbolide on Jupiter. The Astrophysical Journal Letters, 721(2), L129 (2010).  [2] Hueso, Delcroix et al. Small impacts on the giant planet Jupiter, Astronomy & Astrophysics 617, A68 (2018). [3] Arimatsu et al. Detection of an Extremely Large Impact Flash on Jupiter by High-cadence Multiwavelength Observations The Astrophysical Journal Letters, Volume 933, Issue 1, id.L5, 9 pp. (2022). [4] Arimatsu et al. Cloud reflection modelling for impact flashes on Jupiter. A new constraint on the bulk properties of the impact objects, Astronomy & Astrophysics, 677, id. A165 (2023). [5] Giles et al. Detection of a Bolide in Jupiter's Atmosphere With Juno UVS, Geophysical Research Letters, 48, id. e91797 (2021).