User:Mu301/Earth-impact

See Earth-impact events

Comments
C--- C C              The flux of near-Earth objects colliding with Earth C C--- C      Abstract: C C      1. Given the kinetic energy of an impacting object, C              calculate how often such an object collides with Earth. C              If 1 or more per year, print total number per year. C              If less than 1 per year, print interval in years. C C      2. Also calculate the range of uncertainty. C C      3. Estimate diameter based on given energy and rough C              assumptions of mean impact velocity and bulk density. C--- C      Equations: C C      N = number of objects colliding per year C C      log (N) = a0 - b0 * log (E) C C              E = kinetic energy in kilotons (TNT) C              a0 = 0.5677  +/- 0.015 C              b0 = 0.90    +/- 0.03 C C              1 kt == 1 kiloton (TNT equivalent) = 4.185E12 Joules C C C      log (N) = c0 - d0 * log (D) C C              D = diameter in meters C              c0 = 1.568  +/- 0.03 C              d0 = 2.70   +/- 0.08 C C              Calculations based on diameter assume: C C              1. bulk density of 3,000 kg / m^3 (2,600 to 3,400) C              2. mean impact velocity of 20.3 km / s (RMS) C C      Both equations are from the paper in Nature, cited below. C C      The second form of the equation (based on diameter) is far less C      accurate due to the added assumptions for density and velocity. C--- C      General Notes: C C      As can be seen from the computed uncertainty range the C      equation is most accurate for input from 100 ton to 25 kt. C      This is the range for which satellites can observe impacts. C C      The equation can be extrapolated to higher and lower energies, C      but the uncertainty range increases. The program allows input C      of E from 0.01 ton to 10 Gt (for which there is a decent fit to C       published estimates which are based on other evidence.) C C      However, the estimated flux for objects with E > 1 Gt does C      deviate significantly from the equation. The most probable C      impact interval falls outside the uncertainty range somewhere C      between 1 - 10 Gt. For instance, table 5 in the Icarus C      paper (cited below) includes the following data: C C              Energy (Mt)       interval (years)      Diameter (m) C                 1,000         63,000  +/-   8,000     277  +/-  7 C                10,000        241,000  +/-  30,000     597  +/- 15 C               100,000        925,000  +/- 121,000    1287  +/- 33 C C      Calculating the range of uncertainty makes use of MIN1 & MAX1 C      due to the critical region near N = 1. C C      Output should be reformatted to give fewer significant digits... C--- C      References: C C      "The flux of small near-Earth objects colliding with the Earth" C      Brown, P.; Spalding, R. E.; ReVelle, D. O.; Tagliaferri, E.; C      Worden, S. P.  Nature, Volume 420, Issue 6913, pp. 294-296. C C      "From Magnitudes to Diameters: The Albedo Distribution of Near C       Earth Objects and the Earth Collision Hazard" C      Morbidelli, A.; Jedicke, R.; Bottke, W. F.; Michel, P.; C      Tedesco, E. F.  Icarus, Volume 158, Issue 2, p. 329-342. C--- C      Related Info: C C      Asteroids with diameter smaller than 50 - 100 meters C      usually detonate in the atmosphere. C C      On June 6, 2002 a bolide detonated above the Mediterranean C      Sea with an estimated energy of 25.77 (+/- 2.16) kt. C C      A Feb. 1, 1994 bolide was perhaps several tens of kilotons. C C      The 1908 Tunguska impact in Siberia is estimated at ~10 Mt. C C       The Chicxulub crater impact is estimated at ~1E8 Mt. C       Such impacts might occur at intervals of tens to hundreds C      of million years. C---