1914.pdf
Lunar and Planetary Science XXXII (2001)
A SECOND COLLECTION OF MICROMETEORITES FROM THE SOUTH POLE WATER WELL
S. Taylor, J. H. Lever, and J. Govoni, CRREL, 72 Lyme Road, Hanover, NH 03755, staylor@crrel.usace.army.mil.
Introduction: In 1995, we successfully collected
To suction particles from small deep depressions we
both melted and unmelted micrometerorites from the
reconfigured the collector components (Fig. 2) and
bottom of the South Pole drinking water well
attached an intake nozzle directly to the pump and a
(SPWW). Particles were obtained from a 30-m2 area
filter bag to the pump outflow. The filter fabric we
and the age of the ice sampled was approximately
used had a 17-m mesh opening.
1100-1500 AD. We returned to the well in December
2000 with the goal of collecting all of the material
from the bottom before its closure in 2001.
Experimental Methods: We used the same
equipment and general methods we described for our
1995 deployment (Fig.1)[1]. Our collector suctioned
and internally filtered the particles from the ice sur-
face while traversing the well bottom. We controlled
it from the surface via a waterproof electro-
mechanical cable and an underwater video system.
Based on what we knew about the bottom topography
of the well we modified the collector to improve its
ability to climb sloped surfaces and to suction parti-
Fig. 2. Modified collector. Particles are suctioned by
cles from cm-deep depressions in the ice. The former
axe-shaped nozzel (right), go through the pump and
was accomplished by using higher torque motors and
into filter bag. The spiked wheels are not visible.
by lowering the center of gravity of the collector.
Results: The well is now 140 m deep, 35 m be-
low the 1995 level. A depth-to-age relationship ob-
tained from an ice core [2] gives an age of 700-1100
AD for the new interval. The main bottom features
we observed in 1995, a central plateau and sur-
rounding pockets, were preserved. This time, how-
ever, the central plateau was larger and bowl shaped.
Climbing out of the bowl, the collector decended into
narrow particle-filled depression (pockets). We had
difficulty suctioning these areas in 1995.
In 2000, we were able to suction the central pla-
teau and all the surrounding pockets. The 11 de-
ployments yielded about 40 g of material. Hand
sorting of several different samples suggests that
about 1% of the collected material is extraterrestrial.
Only 1/5 as much sediment was collected this time,
indicating that much of the debris from the 1994 wa-
ter pump failure was removed during the 1995 de-
ployment. We have not yet processed the video re-
cord to determine the area suctioned, but we estimate
that we sampled about 40 m2.
As found previously [3], most the micrometeor-
ites appear unweathered. Many of the extraterres-
trial particles are cosmic spherules that have been
partially to totally melted(Fig. 3). There are some
Fig. 1. Plastic 0.3 by 1.2 m collector body (white)
transparent and translucent glass spherules, in addi-
containing filter fabric. Spiked wheels (top one visi-
tion to a few unmelted micrometeorites.
ble) provide mobility; stainless steel central water-
proof housing contains motors and pump.
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