[meteorite-list] Two New Images from MESSENGER's First FlybyofMercury

From: lebofsky at lpl.arizona.edu <lebofsky_at_meteoritecentral.com>
Date: Thu, 17 Jan 2008 09:38:31 -0700 (MST)
Message-ID: <1443.128.196.250.86.1200587911.squirrel_at_timber.lpl.arizona.edu>

Hi Again:

A little bit more on space weathering (wish I had the time to read up on
the latest or at least talk to friends who know more than me on the
subject).

Over long periods of time, when you remelt the material on a surface, you
get very small particles with the iron dispersed within it (nanophase
iron). This darkens and reddens the surface (you get rid of the bright
rays).

Space weathering is caused by solar wind and micrometeorite impacts (very
small glassy particles and vapor covering of existing particles). On
Mercury, there is a weak magnetic field, so this protects much of the
surface from the solar wind. However, because of its location the
micrometeorites create about 20 times as much glassy material as on the
Moon which would enhance weathering on Mercury over the Moon.

Since Mercury is reddish in color, this supports the idea that weathering
is occuring on Mercury. However, all of the evidence points to very little
iron in the surface material of Mercury relative to the Moon. So, is there
enough iron to allow for weathering of the surface? Even with the higher
micrometeorite flux, will weathering occur fast on Mercury than on the
Moon? I think that are some of the questions that are now being addressed
with the latest images of Mercury.

Larry
Received on Thu 17 Jan 2008 11:38:31 AM PST