**Effects of Elevation on Ground Impact of Small Asteroids**

**M. Patrick Goda, Jack G. Hills (LANL)**

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
= 15 km/s impacts the ground with velocity
0 if *h* = 0 km, however 18 km/s if *h* = 5 km. Iron
meteoroids of this size ( 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 ( 8 km) to lose
most of their energy, which reduces the effect of *h*. 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
with *h* when 40-60 m for = 0-15
km/s. The radius of the impact crater produced by a meteoroid
of a given type, and *R* increases with *h*. This
dependence on *h* is very small for iron meteoroids with =
0-15 km/s and *R* > 25 m. For stony meteoroids with =
0-15 km/s and *R* = 40-100 m, increases with *h* more
dramatically than for iron meteoroids. As an example, a stony
meteoroid with *R* = 60 m and = 10 km/s produces a crater
= 400 m at *h* = 0 and = 1.6 km at *h* = 5 km. Stony
meteoroids with *R* = 60-80 m and = 0-15 km/s produce
craters at *h* = 5 km with = 0.6-1.6 km larger than craters
produced at *h* = 0. Iron meteoroids exhibit the greatest increase in
if 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 875 m. It is clear that estimates of *R* based
on must take into consideration the effects of *h*.