After a week or so of cataloging all the unnamed craters alongside the named craters I already cataloged, as well as re-inducting several more craters I previously discarded and even obtaining a number of brand new candidates, I — at last! — have some cool new results!  **and another .ppt file of craters & results to show for it….


My Mercurian crater count now is the highest it’s ever been, at 36 (19 named & 17 unnamed).  The smallest crater is now an unnamed crater @ 19.93 x 63.58 with a diameter of only 16 km (the largest is still Abedin @ 116 km wide).  I even have a melt flow crater now (see below)!

Area west of 19.6 x 81.29, note the darker material (via MODE).

As for the results:  “Figure 3” of Neish et al. (2017) shows how craters whose exterior melt deposits tend to coincide with their rim crest low dominate the Lunar complex craters studied, while on Venus the majority of the craters studied had their melt deposits found around 90* or greater from the low.  As for Mercury, analyzing the 36 craters using JMARS has yielded the preliminary result of possessing a large number of craters in the “coincide” area (like the Moon) but also a large number in the “>90*” category (like Venus).  This implies that Mercury lies intermediate to the Moon & Venus, when it comes to impact melt emplacement.

As hypothesized!  Yay!

So… what does this mean?  Well, my initial hypothesis here is that there could be two factors at play here:  First, although Mercury has higher topography (averaged over its entire surface) than Venus it may actually have slightly lower topography than the Moon; thus, unless the Mercurian crater in question is found in a high-topography area a crater’s melt will tend to emplace more like it does on Venus — that said, there is still high topography, hence the large “coincide” value.  Second, because complex craters on Mercury tend to be deeper than those on Venus yet shallower than those on the Moon it could be a matter, in some cases, of the structure of the crater itself; deeper craters on Mercury (w.r.t. crater size) may deposit melt more similarly to craters on the Moon, while shallower craters may deposit more like on Venus — where impactor direction is more important (something I’ll have to check, eventually, for Mercury by looking at the ejecta patterns about rayed craters…).

Analysis of my Mercurian craters in JMARS is a first step, to see what I’d find.  Now, the real analysis begins with downloading MDIS + MLA files for each crater and compiling them all using ArcMap.  That’ll keep me busy for a couple weeks, I think!