The Hamburg Meteorite Fall: Fireball trajectory, orbit and dynamics

Abstract

The Hamburg (H4) meteorite fell on January 17, 2018 at 01:08 UT approximately 10km North of Ann Arbor, Michigan. More than two dozen fragments totaling under one kilogram were recovered, primarily from frozen lake surfaces. The fireball initial velocity was 15.83 $\pm$ 0.05 km/s, based on four independent records showing the fireball above 50 km altitude. The radiant had a zenith angle of 66.1 $\pm$ 0.29 degs and an azimuth of 121.56 $\pm$ 1.2 degs. The resulting low inclination ($<$ 1 deg) Apollo-type orbit has a large aphelion distance and Tisserand value relative to Jupiter (Tj) of $\sim$ 3. Two major flares dominant the energy deposition profile, centred at 24.1 and 21.7 km altitude respectively under dynamic pressures of 5-7 MPa. Our preferred total energy for the Hamburg fireball is 2 to 7 T TNT (8.4 to 28 x 10$^9$ J), which corresponds to a likely initial mass in the range of 60 to 225 kg or diameter between 0.3 to 0.5 m. Based on the model of Granvik et al (2018), the meteorite originated in an escape route from the mid-outer asteroid belt. Hamburg is the 14th known H-chondrite with an instrumentally-derived pre-atmospheric orbit, half of which have small ($<$5 deg) inclinations making connection with (6) Hebe problematic. A definitive parent body consistent with all 14 known H-chondrite orbits remains elusive