Meteosat observation of the atmospheric entry of 2008 TC$\mathsf{_{3}}$ over Sudan and the associated dust cloud

Abstract

We analyzed serendipitous observations by the Meteosat 8 weather satellite of the fireball caused by the entry of the small asteroid (or large meteoroid) 2008 TC 3 over northern Sudan on October 7, 2008. Meteosat 8 scans the Earth in 5 min cycles. The fireball was captured in the 2:45 UT images in four visible-near infrared channels (0.6-1.6 μm) at a height of 45 km, and in eight mid infrared channels (3.9-13.4 μm) at a height of 33 km. The latter channels also detected at least two dust clouds deposited in the atmosphere at the heights of about 44 and 36 km. The dust deposition was a result of severe atmospheric fragmentation of the asteroid, accompanied by fireball flares, which could be detected in the light scattered by the Earth's surface. The fireball brightness was measured at two random heights, 45 and 37.5 km, where it reached −18.8 and −19.7 mag, respectively. The peak brightness was probably higher than −20 mag. The color temperature of the fireball at 45 km was 3650 ± 100 K. Infrared spectra of the fresh dust clouds were dominated by the 10 μm Si-O band caused by recondensed amorphous silicates. Five minutes later, the dust clouds were detected in absorption of thermal radiation of the Earth. At that time, the silicates were largely crystalline, suggesting silicate smoke temperatures exceeding 1000 K. The total mass of the silicate smoke was estimated to be 3100 ± 600 kg. More mass was probably contained in larger, micron sized, and colder dust particles resulting from incomplete sublimation of the asteroidal material and detected later by Meteosat 8 and 9 in scattered sunlight. Based on the heights of asteroid fragmentations, we guess that the bulk porosity of 2008 TC 3 was of the order of 50%, i.e. higher than the porosity of the recovered meteorite Almahata Sitta.

Impact flux on Jupiter: From superbolides to large-scale collisions

“…Figure 8 shows the fraction of energy emitted in the red and blue wavelength ranges of the June 2010 impact and the total luminous energy of the fireball deconvolved from the system response at each temperature. Comparing both curves, we obtain compatible results for both observations with temperatures ranging over 6500−8500 K. These temperatures encompass those derived for the optical flashes observed by the Galileo spacecraft in Shoemaker-Levy 9 impacts (7800 ± 600 K; Chapman 1996), and they are significantly higher than those derived for bolides entering Earth's atmosphere (3700 ± 100 K for the 2008 TC3 asteroid; Borovička & Charvát 2009). We assume that emission temperatures are not well constrained from this observation and extend the range of possible temperatures for the emission flash from 3500−10 000 K (as the upper limit fixed by numerical simulations later presented).…”

Internal structure and physical properties of the Asteroid 2008 TC3 inferred from a study of the Almahata Sitta meteorites

“…We can deduce that the macroporosity of 2008 TC 3 must have been significant as the asteroid was observed to have low strength and disintegrated early on during its atmospheric entry (Jenniskens et al, 2009;Borovička and Charvát, 2009). However, it was not a completely strengthless body, given its high rotation rate with a period of 100 s (Scheirich et al, 2010).…”

Are some meteoroids rubble piles?

“…The data on the behavior of the body during the atmospheric entry are, unfortunately, scarce. There was a major flare at the height of 37 km and probably other flares at 53, 45, and 32 km (Jenniskens et al 2009, Borovička & Charvát 2009). Fireball flares are evidences of meteoroid fragmentation.…”