Abstract
Experimental work has shown that craters with distinct morphologies within certainboundaries are formed when impacts occur on a loose layer sitting over a coherent
substrate. These distinctive crater morphologies have also been identified on the
Moon as a result of impact events on the regolith which overlays a bedrock. Most
of the regolith depth studies in the literature are for surfaces aged 3 Gy and older.
I chose to study regions aged between 1.33 Gy and 3.88 Gy. I measured small
flat-floored and concentric craters (<150 m) from across various mare terrains on
the lunar globe. To measure regolith depths, I adopted the crater morphology
method based on the work by Oberbeck and Quaide. I found median regolith depths
between 1.6 m to 5.0 m across my study sites. Previous researchers have shown that
their results agree with the hypothesis that lunar regolith depth will increase with
time as the surface is exposed to meteorite bombardment, as such older surfaces will
have deeper regolith. If the assertion that regolith depth correlates with age were
correct, then I would expect very young surfaces to exhibit thinner regolith than in
older areas. instead I did not observe a significantly thinner regolith in younger
regions. My measure of thickness of the regolith did not have any correlation
with the age of the surface. I studied the relationship between crater morphology
and regolith depth to assess morphology progression as regolith depth increases. I
have determined that a new crater morphology, the "hummocky" crater, should be
included in the crater progression. I found hummocky craters that could not be
classified as either flat-floored or concentric due to the difference in their morphology.
I propose a new crater morphology progression as normal to flat-floored to concentric
to hummocky.