Before beginning the experiments, the students steril- ized the velvet cloths used to transfer cells from the NAPS to the EPS. The most likely reason that the velvet cloths were stcrilized was to avoid contaminat- ing the; G, EPS WiLh cells that were not from the NAPS. velvet cloths with yeast from the NAPS. velvet cloths with bacteria from the NAPS. ACT-68G 41 GO ON TO THE EXT PAGE. 40000000004 Passage 111 When an asteroid hits ihe surface of a planet or moon, an impact crater ks formed. An ast6roid that hits Earth under .a specific set of conditions (including speed arid anglc), referred to here as Set C, forms a crater with a diameter about 20 times the asteroid's diameter. Figure I shows the energy released by the impact, for a range of asteioid diameters. 100,000,000 10,000,000 1,000,000 100,000 10,000 1,000 100 FiguÉe 2 shows the average amount of time that elapses between consecutive impacts on Earth by asteroids with the same diameter, for a range of asteroid diameters. Figure 3 shows the perc¢nt of the surface of the Moon, Mercury, and Mars that is covered by impact craters, for various ranges of crater diameier, 10 asteroid diameter (km) 1,000,000 500,000 Figure 2 100,000 50,000 Key oon 10,000 5,0 ercury Mars 1,000 100 50. 10 $ 0.2 (J irnpt crater diameter (km) asteroid diameter (km) Fioure 3 Note.. One energy unit - the energy released by the detonation of I million tons of TNT. Figures adapted from Eugene M, Shoemaker and Caiolyn S. Shoemaker, "The Role of Collislons. 1999 by Sky Publishing Corp. Fioure I Aryf.88G 42 GO ON TO THE NEXT 40000000004
