Geology Reference
In-Depth Information
Figure 5.15. This ~95 km in diameter complex crater shows that
the continuous ejecta deposits (outer boundary marked with
arrows) fall within a distance about half the crater diameter
and that some secondary crater chains (asterisk) occur within the
ejecta deposits (NASA MESSENGER images 108826040 and
108826045).
Figure 5.17. The bright-rayed 80 km in diameter crater Debussy in
the southern hemisphere of Mercury (NASA MESSENGER NAC
131773947, NASA PIA 11371).
Figure 5.18. The asymmetric bright-ray pattern around the 15 km in
diameter Qi Baishi crater (left side) suggests a low-angle impact by
an object traveling from west to east (left to right); the
“
butter
y
”
ejecta pattern around the 13 km in diameter Hovnatanian crater
(lower right) also suggests an oblique impact, but it is not known
whether the object was traveling from north to south, or from south
to north (NASA MESSENGER image, NASA PIA 12039).
process involved in the formation and/or preservation of
bright rays in general.
Statistically, most impacts occur at angles that are not
normal (90°) with respect to planetary surfaces. However, as
discussed in
Section 3.4.3
, differences in crater morphology
and ejecta deposits are seen only when the angle of impact is
Figure 5.16. This 44 km in diameter crater is on the
floor of the
Rembrandt basin; the very low Sun-angle illumination emphasizes
the continuous ejecta and its proximity to the rim (NASA
MESSENGER NAC 131766401M).
