We consider meteoroids that impact ground at elevations h above mean sea level where h = 0 to 5 km. Meteoroids lose less energy in the atmosphere as h increases, so their ground impact damage is greater. This effect is enhanced if the bolide fragments. As an example, an iron meteoroid of radius R = 10 m and velocity at infinity V_infty = 15 km/s impacts the ground with velocity Vf ~ 0 if h = 0 km, however Vf ~ 18 km/s if h = 5 km. Iron meteoroids of this size (R ~ 10 m) lose most of their energy within 2--3 km after fragmentation. Larger iron meteoroids with R > 25 m require approximately a scale height (H ~ 8 km) to lose most of their energy, which reduces the effect of h. Vf drops by less than 1 km/s if h = 0--5 km for iron meteoroids with R > 25 m. In contrast, stony meteoroids exhibit the greatest difference in Vf with h when R ~ 40--60 m for V_infty = 0--15 km/s. The radius of the impact crater Rc produced by a meteoroid of a given type, V_infty and R increases with h. This dependence on h is very small for iron meteoroids with V_infty = 0--15 km/s and R > 25 m. For stony meteoroids with V_infty = 0--15 km/s and R = 40--100 m, Rc increases with h more dramatically than for iron meteoroids. As an example, a stony meteoroid with R = 60 m and V_infty = 10 km/s produces a crater Rc = 400 m at h = 0 and Rc = 1.6 km at h = 5 km. Stony meteoroids with R = 60--80 m and V_infty = 0--15 km/s produce craters at h = 5 km with Rc = 0.6--1.6 km larger than craters produced at h = 0. Iron meteoroids exhibit the greatest increase in Rc if V_∞ > 10 km/sec and R = 5--10 m. The mean elevation of the continents above sea level is approximately 875 m, but areas such as the Tibetan Plateau and the North American Rocky Mountains have h >> 875 m. It is clear that estimates of R based on Rc must take into consideration the effects of h.
AAS/Division for Planetary Sciences Meeting Abstracts #29
- Pub Date:
- July 1997