Collisional Lifetimes and Impact Statistics of Near-Earth Asteroids

Asteroid-Meteoroid Complexes

“…For 1566 with De=1 km orbiting at R h ∼1.08 AU, Equation (8.4) gives τ Y ≈ 2 Myr. This is two orders of magnitude smaller than the collisional lifetime of 1-km near-Earth asteroids (Bottke et al, 1994), suggesting that YORP torque spin-up is plausible. Asteroids rotating faster than the spin-barrier cannot be held together by self-gravitation only, but require cohesive strength (e.g.…”

Number of Near-Earth Objects and Formation of Lunar Craters over the Last Billion Years

“…If the curve from the paper by Granvik et al (2018, Fig. 26) is moved up according to the probability pE ≈ 10 -8 that an ECO larger than 1 km across will impact the Earth in a year, which was obtained by Bottke et al (1994), Dvorak and Pilat-Lohinger (1999), Ipatov (2000Ipatov ( , 2001 and Mather (2004a, 2004b), (i.e., the characteristic time interval preceding a collision of an ECO with the Earth is assumed to be TE ≈ 100 Ma), then the resulting curve will be much more consistent with the current data on the probabilities of bolide infalls (Brown et al, 2013) and the expected frequency of infalls of Tunguskatype objects onto the Earth than the curve in the cited figure.…”

“…These estimates of pE are 2-5 times smaller than those based on the consideration of orbits of large ECOs observed. The latter were made by Bottke et al (1994) and Dvorak and Pilat-Lohinger (1999), who used the algorithms close to that of Wetherill (1967), and by Ipatov (2000Ipatov ( , 2001 and Mather (2004a, 2004b), who used quite a different algorithm to calculate the probabilities of collisions between bodies and planets. The probability that an ECO will impact the Earth in a year is pE = 1/TE, where TE is the characteristic time from the current moment to a collision of the ECO with the Earth.…”

“…The number of ECOs known even in 2001 (particularly, those considered by Mather (2004a, 2004b)) exceeded the presently known number of ECOs with diameters not smaller than 1 km, while the consideration of more ECOs reduced TE only slightly. In the papers by Bottke et al (1994), Dvorak and Pilat-Lohinger (1999), Ipatov (2000Ipatov ( , 2001 and Mather (2004a, 2004b), the collision probabilities of the observed ECOs with the Earth were calculated (with known values of the semimajor axes, eccentricities, and orbit inclinations of these ECOs) and the average of this probability for a year 1/TE was determined. The value of pE obtained in those papers was close to 10 -8 .…”

“…In the other sections, the data used in this comparison are discussed, specifically, the dependences of the crater diameters on the impactor sizes. The number of known Copernican craters and the data of the models were compared for several estimates of the collision probabilities of ECOs with the Earth (Werner and Ivanov, 2015;Emel'yanenko and Naroenkov, 2015;Granvik et al, 2018;Bottke et al, 1994;Dvorak and Pilat-Lohinger, 1999;Ipatov, 2000;Ipatov and Mather, 2004a). The ratio of the collision probabilities of near-Earth objects (NEOs) with the Earth to those with the Moon was assumed at 22 (Le Feuvre and Wieczorek, 2011).…”