[meteorite-list] Mars glaciers

[Gerald Flaherty]

Thanks Darren,
I would imagine that Louis Agazssi(sorry for the spelling) would roll over 
in his grave if we didn't tentatively accept these findings until we get our 
feet on Martian soil(regolith?)(dust?)(rock?)
Jerry
----- Original Message ----- 
From: "Darren Garrison" <cynapse at charter.net>
To: <meteorite-list at meteoritecentral.com>
Sent: Friday, March 18, 2005 12:43 PM
Subject: [meteorite-list] Mars glaciers


http://www.innovations-report.com/html/reports/physics_astronomy/report-41996.html



‘Hourglass’ shaped craters filled traces of glacier

This image, taken by the High Resolution Stereo Camera (HRSC) on board ESA’s 
Mars Express
spacecraft, shows flow features most likely formed by glaciers or ‘block’ 
glaciers.

This unusual ‘hourglass’-shaped structure is located in Promethei Terra at 
the eastern rim of the
Hellas Basin, at about latitude 38º South and longitude 104º East. A 
so-called ‘block’ glacier, an
ice stream with a large amount of scree (small rocks of assorted sizes), 
flowed from a flank of the
massif into a bowl-shaped impact crater (left), nine kilometres wide, which 
has been filled nearly
to the rim. The block glacier then flowed into a 17 kilometre wide crater, 
500 metres below, taking
advantage of downward slope.

The Martian surface at mid latitudes and even near the equator was being 
shaped by glaciers until a
few million years ago. Today, water ice could still exist at shallow depths 
as ‘fossil’ remnants of
these glaciers.

Numerous concentric ridges are visible and appear similar to ‘end moraines’ 
(hills of scree that
form as an extending glacier pushes material ahead and remain after its 
retreat). Furthermore, there
are parallel stripe-like structures that are interpreted as middle moraines, 
displaying the flow
direction of these glaciers. In locations where glaciers creep over steep 
terrain, cracks are
visible. Similarly in terrestrial glaciers, cracks are formed when tensile 
stress within the ice
increases due to greater slope and uneven terrain.

Further glacial features include elongated grooves, extending several 
kilometres, and elongated
hills observed on the surface of mountain ridges some distance from 
potentially glaciated areas.
These hills could be analogous to so-called ‘drumlins’, structures formed 
beneath ice by glacial
flow resulting in compression and accumulation of abraded material. On 
Earth, drumlins appear in
formerly glaciated regions such as Germany’s Bavarian alpine uplands. These 
glacial structures are
seen in a consistent spatial context, confirming the belief that scientists 
are really seeing former
glaciers on Mars.

Of particular interest is the age of these glacially shaped surfaces, which 
seem to be fairly intact
over a wide area of the formerly glaciated terrain. Typical evidence for a 
significant loss of ice
volume, such as ‘kettle holes’ present in ice-free regions of Iceland, are 
almost entirely missing.
The statistical analysis of the number of craters formed by meteorite 
impacts used for age
determination also shows that part of the surface with its present-day 
glacial characteristics was
formed only a few million years ago. In planetology, this age range is 
considered extremely young.

In these latitudes, ice on the surface of Mars is not stable over a long 
period of time due to the
extremely thin atmosphere. In theory it is cold enough to allow for the 
existence of glaciers at the
equator – summer day temperatures rise to a maximum of 20° C while night and 
winter time
temperatures often drop below minus 50° C. But under the prevailing 
atmospheric pressure, ice would
sublimate (transform directly from solid to gaseous state), and then escape 
from the atmosphere into
outer space.

Therefore, glaciers must have formed until a few million years ago, in a 
time that was warmer and
possibly also had a thicker atmosphere, and then became inactive or 
retreated due to the lack of
continued supply of ice. Since then, they have been protected from 
sublimation by a thin dust layer.
On Mars, dust is almost ubiquitous and would explain why ‘fossil’ ice 
present at depths of only a
few metres could not be detected by other instruments such as spectrometers.

If these conclusions prove to be true, the results would indicate a climate 
change on Mars within
the last million years. Such a dramatic climate change has been discussed 
for some years by Mars
researchers. It could have been caused by a shift in the polar axis of the 
planet over millions of
years – a phenomenon long known to scientists. Martian climate history is 
one of the main areas that
ESA’s Mars Express can help to decipher.



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