Please join us for our next UT Grotto Meeting on 6 Feb 7:45 in Painter Hall
rm 2.48, see abstract of our featured presentation this week, below.
In our last meeting we elected new officers:
Chair - Stephen Bryant
Vice Chair - Gary Franklin
Treasurer - Heather Tucek
Congratulations Stephen, Gary and Heather! Please contact Gary Franklin if
you are interested in giving a program for the UT Grotto.
Our featured presentation:
The Soudan Mine as a Mars Analog
by
E. Calvin Alexander, Jr.
Geology & Geophysics Department
University of Minnesota
Minneapolis, MN 55455
The Soudan Iron Mine in northeastern Minnesota mined high grade
hematite from the late 1800s until about 1960 in 2.7 billion year old rocks.
Unlike the huge open pit mines on Minnesota �Iron Range�, the Soudan was an
underground mine working a near vertical ore body. When the mine ceased
operations the bottom, 27th level was 2341ft. below the land surface or 689
feet below sea level. The mine was given to the State of Minnesota and
continues operations as State Historic Park offering mine tours to visitors.
Physicists from the University of Minnesota have conducted experiments in the
mine for several decades. The mine is also a major bat hibernaculum. A
calcium, sodium, magnesium chloride brine about twice as salty as sea water
seeps into the lowest level of the Soudan Mine. That brine is anoxic and has
about 150 ppm of ferrous iron in solution. When those anoxic waters reach the
atmosphere in the mine they begin to adsorb oxygen and, mediated by a
flourishing microbiology, are actively depositing a wide variety of classic
cave formations: flow stones, stalagmites, soda straw stalactites and rimstone
dams. These formations are made of the iron oxides ferrihydrite and goethite
and contain the mineral jarosite � and are spectacularly colored.
Starting with the earliest Mariner flyby missions to Mars,
photographs of surface features apparently produced by liquid water have
increased in number, resolution and credibility. The apparently fundamental
problem that �liquid water is not stable at the current temperature and
pressure of the Martian surface� has been a major obstacle to the scientific
credibility the otherwise obvious presence of water produced features on Mars.
The observation that the current surface temperature and pressure of Mars is
below the triple point of water is valid only for pure water. The triple point
of concentrated brine solutions is well within the observed range of Martin
water vapor pressures and temperatures. Concentrated brines can exist as
stable liquids on significant parts of the Martian surface for significant
fractions of each Martian year.
The �gullies� discovered on Mars by the high resolution MOS
orbiter camera have been confirmed by the higher resolution HiRISE orbiter
images and are now known to occur widely on Mars. In several locations on Mars
the MOS and HiRISE images reveal structures that appear to be rimstone dams
associated with the distal ends of gullies.
The presence of iron oxide rimstone dams growing from the brines
in the Soudan Mine suggest that those brines may be an analog for conditions on
some parts of Mars. It is interesting to note that in the Soudan Mine brines
form a productive environment for several microbiological communities.
Historically, one of the least successful hypotheses in science
is that the Earth has unique properties in the Universe.
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