From: firstname.lastname@example.org (JamesOberg)
Subject: Mars Gullies: Clathrates, NOT Liquid Water???
Date: 24 Jun 2000 20:08:27 GMT
I was traveling this week to DC to get a national magazine award re best news
story of 1999 in a group of about 500 professional society magazines (my Dec
1999 SPECTRUM piece on "Why the Mars Probe Went Off Course", on my home page,
got the silver medal). I also dropped in at NASA in DC for the press
The "flows" are real enough, and a hundred or more sites have been detected in
the last few months. The occur preferentially north or south of 30deg latitude
(where ice is stable in the permafrost), some in clusters, and they tend to be
on the pole-facing (i.e., colder) side of slopes. There's no correlation with
If they are caused by outbursts of liquid water, then most of what was already
thought to have been known about water in the martian regolith is wrong. The
scientists were quite candid that the distribution of these features doesn't
fit any pattern they expected.
There does seem to be a connection with specific layers in the regolith. One
layer in particular, in one cluster, is cut by several different features,
including crater walls and canyon walls, and it "bleeds" into these strange
gulley-apron flows consistently.
Dr. Mike Carr offered an alternative explanation to liquid water, that the
flows were gas-entrained processes from natural exposure of water/CO2 ice
clathrates, which will flash to vapor on release from overloading regolith,
caused by wind erosion over many many many millions of years. These episodic
gas eruptions can carry dirt, can erode channels, and can leave debris aprons
just like water erosion can.
If that model is correct, there is no liquid H2O involved.
The problem with that hypothesis is the freshlooking channels and aprons, and
especially the top of the channels where stark contrast variations suggest not
very long exposures to martian dust storms, which tend to blur out surface
contrasts within a short (years to centuries) period.
The problem with THIS problem is that if the freshness of these aprons is
believed, then why have they ALL happened recently (i.e., where are the OLDER
aprons?)? Malin did hint he had located what might be a few old (i.e., eroded)
gulleys and channels but that was still uncertain.
This is a mystery worthy of Mars, and nobody is claiming it proves AN-Y-THING
except that the planet continues to surprise us (which is why we keep exploring
it) and that unusual phenomena of unknown cause are shared with the world
science community as soon as they are identified and characterized in a