The January 7, 2015, superbolide over Romania and structural diversity of meter-sized asteroids

Abstract

Superbolides, i.e. extremely bright meteors produced by entries of meter-sized bodies into terrestrial atmosphere, are rare events. We present here detailed analysis of a superbolide, which occurred over Romania on January 7, 2015. The trajectory, velocity, and orbit were determined using two all-sky photographs from a station of the European Fireball Network (EN) in Slovakia and five casual video records from Romania, which were carefully calibrated. Bolide light curve was measured by EN radiometers. We found that the entry speed was 27.76 ± 0.19 km s −1 , significantly lower than reported by US Government sensors. The orbit was asteroidal with low inclination and aphelion inside Jupiter's orbit. The atmospheric behavior was, however, not typical for an asteroidal body. The peak brightness of absolute magnitude of −21 was reached at a quite large height of 42.8 km and the brightness then decreased quickly. The bolide almost disappeared at a height of 38.7 km, leaving just a stationary luminous trail visible for several seconds. Only one small fragment continued until the height of 36 km. Brief meteorite searches were unsuccessful. The modeling of the light curve revealed that the body of initial mass of about 4500 kg remained almost intact until the dynamic pressure reached 0.9 MPa but it was then quickly disintegrated into many tiny fragments and dust under 1-3 MPa. A comparison was made with three other superbolides for which we have radiometric light curves: ordinary chondrite fall Košice, carbonaceous chondrite fall Maribo, and cometary Taurid bolide of October 31, 2015. The Romanian superbolide was not similar to any of these and represents probably a new type of material with intrinsic strength of about 1 MPa.

Small impacts on the giant planet Jupiter

“…The two flashes are readily apparent when examining the video observation frame by frame and can be related to fragmentations of the impact object. The same types of features with similar timescales are observed on light curves of superbolides on Earth (see, e.g., Figure 3 in Borovička et al 2017 and the extended figure 2 in Borovička et al 2013). This might therefore be the first case for fragmentation of Jupiter bolides and suggests that observations of future impacts should involve a fast frame rate of at least 30 fps to observe these characteristics.…”

The Žďár nad Sázavou meteorite fall: Fireball trajectory, photometry, dynamics, fragmentation, orbit, and meteorite recovery

“…The mass of the largest surviving fragment is plotted as a function of increasing dynamic pressure. Borovi cka et al (2017) presented the same graph also for some large nonchondritic meteoroids. Note that the lowest plotted mass is not identical with the mass of the largest expected meteorite.…”

“…Borovička et al. () presented the same graph also for some large nonchondritic meteoroids. Note that the lowest plotted mass is not identical with the mass of the largest expected meteorite.…”

Observation of metre-scale impactors by the Desert Fireball Network

“…7). The worst USG estimates are for the Buzzard Coulee meteorite (18.1 km s −1 calculated by Milley (2010) compared to 12.9 km s −1 USG), and the Romanian bolide (27.8 km s −1 calculated by Borovička et al (2017) compared to 35.7 km s −1 USG). These were underestimated by 28%, and overestimated by 28%, respectively.…”