[meteorite-list] Mars Impact Bench - On Beyond Erosion

From: Jonathan Abel <abelcompany_at_meteoritecentral.com>
Date: Fri, 7 Oct 2011 11:09:05 -0700
Message-ID: <04FEC3D388484FDB8A0CAD4D0D9BDF92_at_userdbdeb94d02>

Ron Baalke --

Your posts are among the reasons I enjoy this group so much! THANKS!!

I was immediately fascinated by your first image (link below) and mused
on the colossal forces that created a Mars impact crater 6 miles across.
And that bench -- hmmm...here's a layman's take...and I invite being
corrected by the group, whose passions and professions deal with these
spectacular studies.

On our way to Ruben's famous Holbrook Hunt we again stopped at Arizona's
amazing Meteor Crater and I recall driving up over a similar "bench".
Not as well developed or as obvious...and I know conditions, events and
timelines were very different on the two planets, but if you relate
Earth's best preserved and first proven meteor crater to the Mars
crater, I am nagged by the notion that the Mars bench was a by-product
of much more than erosion.

The explanation I was given at the crater for that "embryonic" bench on
Earth was that the heavier/more consolidated bedrock was lifted in what
I'll call "splash" forces and turned upside down. Thus the layered
strata was inverted...creating what must be an artifact of many impacts
- the oldest and harder crusty stuff is on top on the crater rim...and
our impact is geologically youthful - less that 50K years old, so solid
rock erosion can't be a big factor here...but do you agree we have the
makings of a bench?

Earth --- Meteor Crater Slide Show:
http://www.meteorcrater.com/Photo-Gallery

Mars --- Ron's Link - Crater with Surrounding Bench in Sinus Meridiani:
http://hirise.lpl.arizona.edu/ESP_023382_1845

On Mars, the impact seems to have given rise to a similar geology as the
ancient hard-top sandstone pinnacles of Monument Valley -- good old
Earth-logical erosion would add to the severity of the Mars bench over
time...but only after a really good boost, eh?

What a sight that would be! To see the mixture of extreme forces at the
center of an impact act together to pry up the crust (possibly even set
some on edge); massive quakes and hot, explosive winds would maybe sift
by weight (like in a gold pan), melt solid rock (leaving an edge that
didn't melt) and there might even be a draining back into the crater of
melted or granulated stone (leaving a visible rim like high-tide at the
beach). And I'm probably missing other integral forces that would help
create a bench "on beyond erosion".
  
Thanks,

Jonathan
Received on Fri 07 Oct 2011 02:09:05 PM PDT