[meteorite-list] Hydrogen Geysers And Metallic Iron Could Explain Puzzling Hollows on Mercury

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 1 Nov 2011 09:39:52 -0700 (PDT)
Message-ID: <201111011639.pA1GdqjL003484_at_zagami.jpl.nasa.gov>

http://www.technologyreview.com/blog/arxiv/27296/

Hydrogen Geysers And Metallic Iron Could Explain Puzzling Hollows
on Mercury

The strange features spotted by the MESSENGER spacecraft may be caused
by hydrogen venting from the planet's interior, says planetary geologist

Technology Review
October 31, 2011

You can be forgiven for thinking that the Solar System's innermost
planet is a perennial disappointment. Mercury has always appeared a
dead, crater-scarred ball of rock with little of interest for the
discerning astronomer.

And yet, last week the planet surprised everybody by presenting
planetary geologists with a conundrum. The MESSENGER spacecraft,
currently in orbit about Mercury, sent back images of strange features
on the surface that defy explanation.

The pictures have generated more than a little fuss. The hollows are
irregularly shaped, shallow, rimless depressions which have have formed
in craters, indicating that they must be relatively recent additions to
the landscape. They are also strangely bright, indicating that they are
covered in a highly reflective material.

That means the surface of Mercury must be active in some way. The
question is: how?

Today, Marvin Herndon, an independent scientist based in San Diego,
gives us his idea. He points out that if, during the planet's formation,
the pressures and temperatures were high enough for iron to become
liquid, then it ought to have absorbed large amounts of hydrogen.

As the liquid solidifies, this hydrogen would be released and escape
through the surface of the planet. The result would be hydrogen geysers
that erupt from time to time on the planet's surface.

These hydrogen geysers could certainly have caused the rimless
depressions that MESSENGER sees, says Herndon, a self-proclaimed
maverick in the world of planetary geology.

What's more, hydrogen would react with various substances as it passes
through the planet's crust. One possible reaction is the reduction of
iron sulphide to metallic iron. Iron sulphide is common on the surface
of Mercury.

It is this light dusting of metallic iron that gives the depressions
their high reflectivity, says Herndon.

Interesting idea.

Ref: arxiv.org/abs/1110.5796 <http://arxiv.org/abs/1110.5796>:
Explanation for Observed Evidence of Geologically Recent
Volatile-Related Activity on Mercury's Surface
Received on Tue 01 Nov 2011 12:39:52 PM PDT