Susan Taylor, James H. Lever, Ralph P. Harvey, and May 1997

John Govoni

CRREL REPORT 97-1

Collecting Micrometeorites from the

South Pole Water Well
Abstract: A collector was designed and built to retrieve

micrometeorites from the floor of the South Pole Water

Well. The large volume of firn and ice being melted for

the well and the low component of terrestrial material

in Antarctic ice make the South Pole Water Well an

ideal place to collect micrometeorites. Because the age

of the ice being melted is known, yearly or periodic

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collections provide large numbers of micrometeorites of

known terrestrial age. The collector was designed to pose

no threat to the well’s water quality, to be reliable and

easy to operate, and to collect particles larger than 50

μm. This report details how this collector was built and

tested and documents the rationale behind some of the

design choices. It also includes preliminary findings from

the first deployment.
Susan Taylor, James H. Lever, Ralph P. Harvey, and May 1997

John Govoni

CRREL Report 97-1

Collecting Micrometeorites from the

South Pole Water Well

Prepared for

OFFICE OF THE CHIEF OF ENGINEERS

Approved for public release; distribution is unlimited.

US Army Corps

of Engineers®

Cold Regions Research &

Engineering Laboratory
PREFACE

This report was prepared by Susan Taylor, Research Physical Scientist, Geological Science Division; James Lever, Mechanical Engineer, Ice Engineering Research

Division; and John Govoni, Physical Science Technician, Snow and Ice Division; of

the Research and Engineering Directorate of the U.S. Army Corps of Engineers

Cold Regions Research and Engineering Laboratory; and Ralph Harvey, Senior Research Associate, Department of Geological Sciences, Case Western Reserve University, Cleveland, Ohio.

Funding for this work was provided by the National Science Foundation. The

report was technically reviewed by John Rand and Stephen Ackley of CRREL.

The authors wish to thank the following people who assisted in this study: Robert Forrest, William Birch, and Peter Alekseiunas, who made the components for

the micrometeorite collector at CRREL; Michael Walsh, who suggested the technique for fabricating the collector arm; Dennis Lambert, who turned our ideas into

detailed drawings and added improvements of his own; John Rand, who provided

invaluable information about the well and the wellhouse; the CRREL brainstorming participants—Dr. Thomas Jenkins, Janet Hardy, Dr. Edgar Andreas, Deborah

Diemand, Stephen Flanders, Capt. Jeffrey Wilkinson, John Rand, and Dr. J.-C.

Tatinclaux—for their wonderful and varied suggestions for the collector design;

Dr. Ellen Mosley Thompson, The Ohio State University, who kindly provided unpublished data on particle size distributions obtained from a South Pole core; Peter

Stark, who constructed the wooden well shape on which the collectors were tested;

Thomas Vaughan for his illustrations; and Jesse Stanley, who juggled his basin tests

so that these tests could be run at all hours of day and night. The authors also thank

Ms. Hodgdon’s 8th-grade math class at Lebanon Junior High School, Lebanon, N.H.,

who designed the logo for the project, shown on the cover of this report. Last but

not least, the authors thank Michael Shandrick, who assisted them at the Pole during the marathon drilling session and any other time his help was needed, for his

dedication and good spirit.

The contents of this report are not to be used for advertising or promotional

purposes. Citation of brand names does not constitute an official endorsement or

approval of the use of such commercial products.

ii
iii

CONTENTS

Page

Preface ..................................................................................................................... ii

Introduction ............................................................................................................ 1

South Pole Water Well ........................................................................................... 2

Collector design ..................................................................................................... 4

Technical objectives ....................................................................................... 4

Design requirements and performance criteria ........................................ 4

Preliminary design ........................................................................................ 5

Particulate concentrations expected ........................................................... 6

Pumping requirements and preliminary tests .................................................. 7

Final design ............................................................................................................ 8

Prototype tests and modifications ............................................................... 10

Deployment .................................................................................................... 13

Samples ................................................................................................................... 15

Weathering ...................................................................................................... 18

Flux rates ......................................................................................................... 18

Conclusion .............................................................................................................. 21

Literature cited ....................................................................................................... 22

Appendix A: SPWW dimensions ........................................................................ 25

Appendix B: Summary of collector development tests.................................... 35

Appendix C: Summary of collector deployments in SPWW .......................... 37

Abstract ................................................................................................................... 39

ILLUSTRATIONS

Figure

1. Evolution of the South Pole Water Well .................................................. 3

2. Approximate size and shape of the South Pole Water Well

in December 1995 .................................................................................. 4

3. Original collector concept .......................................................................... 5

4. Number and size distribution of particles >50 μm estimated

for the bottom of the SPWW ............................................................... 6

5. Final collector-arm cross-section .............................................................. 8

6. Major components of the 1.2-m operational collector .............................. 9

7. Schematic of the 1.2-m collector in the SPWW ....................................... 10

8. 2.5-m operational collector suspended from the cable on a winch ..... 11

9. Slot width measured along the 1.2-m collector prior to

deployment ............................................................................................ 13

10. Work space at the SPWW, consisting of a winch room directly

over the access hole and an adjoining laboratory ............................ 14

11. Hot-water drill used to drill second access hole to the SPWW ............ 14

12. Map of the bottom of the SPWW showing the plateau area

and pocket no. 1 .................................................................................... 15

13. An assortment of spherules from the SPWW ......................................... 16

14. Sediment retrieved from the well ............................................................. 17

15. Backscattered electron photomicrographs of selected SPWW

micrometeorites ..................................................................................... 19

16. Ternary diagram illustrating where the analyzed SPWW

spherules plot in relation to the Deep Sea and Greenland

spherules ................................................................................................ 20

17. Weight percent Al/Si and Ca/Al plot of the SPWW spherules

as compared to DSS and chondritic value ........................................ 20

18. Photomicrograph showing a glass rind around a stony

spherule .................................................................................................. 21
TABLES

Page

Table

1. Other wells built in polar regions ............................................................. 2

2. Summary of quantitative collection efficiency tests .............................. 11

3. Size range and weight of the pocket and plateau samples ................... 17

4. Types of extraterrestrial particles in the pocket sample ........................ 18

5. Comparison of SPWW spherule types with those found in

Greenland and in the Deep Sea collection......................................... 20

iv
INTRODUCTION

Micrometeorites are the dominant mass contribution to the present-day Earth and add one hundred tons of material to the Earth each day

(Brownlee 1981, Love and Brownlee 1993). Although ubiquitous in terrestrial environments,

relatively little of this material has been collected

because micrometeorites occur in low concentrations and generally weather rapidly. To collect micrometeorites one needs to find deposits where

they are concentrated. Like meteorites, micrometeorites range from unaltered primordial materials to those that have seen extensive differentiation and alteration deep within a parent body.

They represent collision-produced fragments of

asteroids as well as materials of cometary origin

(Brownlee et al. 1993). Some of these small particles are thought to contain exotic materials, including interstellar grains and fragments of solar

system materials that have no counterparts among

meteorite collections (Bradley et al. 1989, Brownlee

et al. 1993).

In this paper we use the word micrometeorite

as a generic term referring to all types of terrestrially collected extraterrestrial debris with sizes <1

cm. Cosmic spherules refer to spherical and/or

rounded particles that have been totally or partially melted by atmospheric entry. The term interplanetary dust particle (IDP) refers to the small

(<50 μm) extraterrestrial particles collected in the

stratosphere.

More than a century ago a few magnetic cosmic spherules were found in deep-sea sediments

collected by members of the H.M.S. Challenger expedition (Murray and Renard 1876). Both iron and

silicate spherules were found, and it was thought,

especially of the iron spherules, which contained

nickel in chondritic proportions, that they were of

meteoritic origin. The presence of wustite in these

spherules, a high-temperature iron oxide found in

meteorite fusion crusts, also suggested an extraterrestrial origin for iron spherules (Marvin and

Einaudi 1967). The extraterrestrial origin of the

silicate spherules, which are composed of olivine,

interstitial glass, and magnetite, was more difficult to prove. Major element analysis showed that

they had chondritic ratios of magnesium, silicon,

and iron (Blanchard et al. 1978), but it required

trace chemical analyses to show their extraterrestrial origin (Ganapathy et al. 1978).

Cosmic spherules are distinctive-looking particles and have been found in many terrestrial environments. They have been found in the swamps

of Siberia (Krinov 1959), in desert sands

(Fredriksson and Gowdy 1963), in beach sand

(Marvin and Einaudi 1967), in deep sea sediments

(Brownlee 1979), in lithified abyssal sediments

exposed on land (Czajkowski et al. 1983, Jehanno

et al. 1988, Taylor and Brownlee 1991), in Greenland’s cryoconite and melt-water drainage basins

(Maurette et al. 1986, 1987; Robin et al. 1990), and

in Antarctic morainal sediments (Hagen 1988,

Koeberl and Hagen 1989), aeolian debris (Harvey

and Maurette 1991, Hagen et al. 1992), and ice cores

(Yiou and Raisbeck 1990, Hagen et al. 1992).

Unmelted micrometeorites have also been

sought and found. Interplanetary dust particles

(IDPs) were collected in the stratosphere

(Brownlee et al. 1977) and are routinely collected

by NASA using U-2 high-flying aircraft. Larger

unmelted micrometeorites were found in

Greenland ice (Maurette et al. 1987), and many

micrometeorites, primarily <100 μm in size, were

found upon melting and sieving 100 tons of Antarctic blue ice (Maurette et al. 1991).

The South Pole Water Well (SPWW) is a 24-mdiameter by 15-m-deep melt pool 100 m below the

snow surface; it supplies potable water to the

Amundsen–Scott South Pole Station. Because of

the large volume of ice melted, the well is the largest source of micrometeorites yet discovered. The

compressed-snow polar ice preserves a record of

melted and unmelted micrometeorites in an environment low in terrestrial debris, and the well provides the concentrating mechanism necessary for

collecting these particles. The large pool volume

and low water-injection rate produce low circulation velocities that cannot entrain micrometeorites

melted out of the ice. These particles should, therefore, form a lag deposit on the well bottom. Based

on this assumption, we built a collector to retrieve

micrometeorites larger than 50 μm from the bottom of the well. We deployed the collector in DeCollecting Micrometeorites from the South Pole Water Well

SUSAN TAYLOR, JAMES H. LEVER, RALPH P. HARVEY, AND JOHN GOVONI

1
cember 1995 and did indeed recover large numbers of micrometeorites.

The SPWW represents a uniquely valuable

source of micrometeorites. The age of the ice being melted is known as a function of depth

(Kuivinen et al. 1982), making it possible to date

the depositional age of the particles recovered.

Although the SPWW does not allow horizontal

(stratigraphic) control on a fine scale as do traditional cores, the large numbers of extraterrestrial

particles from different time periods should allow

a statistically significant study of the recent variation of cosmic dust flux at the Earth’s surface. The

first year’s collection is an integrated sample of

micrometeorites that fell to Earth between 1100

and 1500 A.D. As melting occurs predominantly

in a downward (older ice) direction at a known

rate, later collections will be integrated samples

from known depths, and thus known ages. More

specifically, the well deepens approximately 10 m

each year (equivalent to 100 years of deposition)

and will melt ice that dates from 400 to 1500 A.D.

during its life. By sampling all, or a known percentage, of the well bottom and repeating the collection on an annual basis, the flux rate and any

variation in either rate or composition of micrometeorites can be determined on a 100-year time scale.

SOUTH POLE WATER WELL

In 1955 Henri Bader suggested building ‘water

wells’ at glacier camps after observing the size and

shape of sewage disposal pits (Clark 1965). Schmitt

Table 1. Other wells built in polar regions.

Date Type Location Additional information

1959 Water wella Camp Century, Greenland Rodriguez assembles components and first

well is made. Well reached 171.5 ft. Observer

lowered into the well after most of the water

had been pumped out (Schmitt and Rodriguez

1960).

1960 Water wella Camp Century, Greenland Original well is restarted, producing a 244-ft

symmetrical, bell-shaped cavity (Schmitt and

Rodriguez 1963).

1960–1963 Waste heat Camp Century, Greenland Made from waste heat from a nuclear reactor

storageb (Clark 1965).

1960–1961 Water well Tuto, Greenland Russell (1965).

1964 Water wellc Camp Century, Greenland Second utility well created.

1972 Water well South Pole, Antarctica Operated 3 months (Williams 1974).

1977–78 Drilling water Ross Ice Shelf, Antarctica

1990–91 Water welld South Pole, Antarctica Drilled by John Rand and John Govoni. Mined

for micrometeorites in December 1995.

1994–95 Drilling water South Pole, Antarctica Amanda Project, PICO

2
and Rodriguez (1960) were the first to build a meltpocket water well in ice, and subsequent polar

wells have been called Rodriguez or Rod wells (see

Table 1 for a list of such wells). Researchers have

searched for cosmic spherules and extraterrestrial

materials in polar wells (e.g., Langway 1963,

McCorkell et al. 1970). McCorkell and his colleagues filtered 200,000 liters of water pumped

from a meter from the well floor at the Camp Century well in Greenland. They found no excess 26Al,

an extraterrestrial marker, on their 3-μm filters. The

micrometeorites had probably formed a lag deposit on the well floor, but the pump intake was

too high on the well bottom to entrain the particles.

The SPWW is a Rodriguez well constructed

during the 1992–93 austral summer. A hot-water

drill was used to melt a 30-cm-diameter hole into

the snow to a depth of 60–70 m. The drill was then

lowered more slowly to create a large pool or reservoir of water. The surface wellhouse, which contains the equipment for drilling and operating the

well, consists of two stacked 4.6 × 2.1 × 2.4 m shipping containers (millvans). The wellhead is in the

lower container, about 2.5 m below the present

snow surface. The 30-cm-diam. wellhead and neck

accommodate the electrical cable connected to the

submersible pump, emergency heat trace, and two

insulated hoses (one carrying water to the surface

and one returning warm water to the well). Because contamination of the well by fuel was a

major concern, a low-temperature EPDM (ethylene propylene dienemonomer) mat surrounds the

wellhead and extends out 7 m.

The SPWW was certified as a source of potable

water in early 1994. On 26 February 1994, the pool

was about 16 m deep and 22 m in diameter, and

the well bottom was 101 m below the wellhouse

(103.5 m below the snow surface, Appendix A).

Before consumption began, however, an electrical

fire in the pump cable on 1 March 1994 forced a 9-

month shutdown. During the shutdown, a 4-mthick ice layer formed on the pool surface and 6–

11 m of freezeback occurred on the walls and bottom. The well was restarted in December 1994 by

drilling through the ice layer and recirculating

warm water as before. By March 1995, the well

had melted below the prefire level and released

any particles trapped during the freezeback. Figure 1 shows the approximate well geometry before and after the fire and at the time of deployment in December 1995. It also shows the corresponding age of the ice (and the depositional age

of the micrometeorites).

The SPWW has supplied potable water since

Start Consumption

30 Jan 95

Volume Consumed

1,600 m3 to end

Dec 95

1000 A.D. 101.2 m

86.6 m

90.2 m

D ~ 22 m

26 Feb 94

Before Fire on 

1 Mar 94

Freezeback Before

Restart on 30 Nov 94

106.5 m

Pump

Pool Volume ~ 4,000 m3

1500 A.D.

4 m Ice She

10 cm Ice Cover

60

70

80 

90

100 

110

Depth (m)

Pool Volume ~5,000 m3

82.6 m

Figure 1. Evolution of the South Pole Water Well.

3
January 1995. The reservoir has reached a relatively stable size of about 24 m diameter and 16 m

depth and contains about 5,000 m3 of water (based

on water consumption and depth data, Appendix

A). The present consumption rate is about 2,000

m3 (about 2 million liters) per year. The pump

draws water from about 1 m below the water surface. About 10% of the water is consumed and the

rest is heated, using waste heat from the station,

and returned to the well.

The flow rate of returning water is about 1

L s–1, and it is discharged 3 m below the water

surface through a nozzle designed to produce a

uniform, 90° cone-shaped jet. Peak discharge velocity 1 m away from the nozzle should be less

than 1 mm s–1, and no remnants of the jet

should persist at the well bottom. Rather, the

jet and heat input probably establish large-scale

circulation cells in the pool. It seems very unlikely

that circulation velocities at the well bottom would

be adequate to entrain the micrometeorites of

interest.

The effort required to model the flow distribution in the SPWW was beyond the scope of our

work. However, we estimated the velocities

needed to transport micrometeorites and assessed

whether such velocities were likely to be present.

To initiate movement of a 50-μm particle with a

density of 2.5 g cm–3 (stony or glassy micrometeorites), flow velocity along the well bottom would

need to exceed about 6 cm s–1 (ASCE 1975). The

micrometeorites of interest are generally larger or

more dense and hence would have higher thresholds. It seems unlikely that bottom velocities

would exceed threshold values, given that velocities 1 m from the nozzle are substantially lower.

We therefore thought that micrometeorites would

form a lag deposit on the well bottom as they are

melted out of the ice.

Originally we had planned to deploy the collector during an annual maintenance period when

the well’s pump and hoses were removed for servicing.* However, space in the well house is very

limited, complicating collector deployment, and

our collection time would have been restricted to

a few hours. For these reasons we drilled a second access hole, about 2 m from the central

hole, and had a separate work area constructed

(Fig. 2).

COLLECTOR DESIGN

Technical objectives

Our technical objectives were (a) to collect essentially all of the micrometeorites from a large,

known area of the well bottom, and (b) to be capable of returning to the same area of the well

bottom annually. Assuming that the micrometeorites form a lag deposit, meeting these technical

objectives would allow us to calculate flux rates

and document any temporal changes in the composition of the particles (i.e., meet the scientific

objectives).

Design requirements and performance criteria

The nature of the SPWW imposes strict requirements on the collector design. The collector must

not degrade water quality under any circumstances. It must fit down a 30-cm-diam. well neck

and survive a cold soak at –50°C during its descent to the well pool. It must operate remotely in

about 20 m of water at a distance of 200 m below

the snow surface.

In addition, we specified several performance

criteria to help guide our design selections. The

collector should collect essentially all particles in

Surface

Winch Room

Lab Wellhouse

2.5 m

60 m 

70 m

80 m

90 m

100 m

110 m 24 m

EPDM 

Protective

Mat

1500 A.D.

1000 A.D.

Camera

and Lamp

Water Level

Collector

Figure 2. Approximate size and shape of the South Pole

Water Well in December 1995.

*J.H. Rand, 1996, Ice Engineering Division, CRREL, personal communication.

4
the size range 50–1000 μm without bias to composition (e.g., toward magnetic particles). Its collection efficiency should be high (and we should

measure it). It should cause no physical or chemical changes to the particles. Its design should minimize handling losses after collection. It should give

reliable performance and be adaptable to unknown bottom surface conditions. In addition, its

design should minimize the possibility of it becoming stuck in the well.

Preliminary design

We had a brainstorming session to gather preliminary collector concepts. After reviewing these

ideas, we selected a concept that involved downhole suctioning and filtering of the particles by a

mobile collector controlled from the surface. Figure 3 shows this concept as originally envisioned.

It utilizes the unconstrained, vertical dimension

of the well neck to maximize the filter capacity and

the area swept out by the collector in a single pass.

A pump develops a high-speed flow to suction

particles through a slot along the underside of a

long, flexible arm containing a filter. The filter arm

would be formed from a flexible, drinking-watersafe plastic to allow it to conform to the curved

well bottom. We could drive the long arm around

in a circle and measure its rotation to determine

the area swept. Separate filter chambers distributed along the arm would reveal information

about the radial distribution of particles. Alternatively, we could independently operate a drive

motor at either end of a shorter version of the collector to maneuver it over undulating well-bottom topography. An underwater video camera

would help maneuver the collector and document

the area swept.

This concept contains many advantages over

alternatives considered. Suctioning particles by entraining them in a water stream should avoid any

compositional bias in the collection (assuming that

the water flow is high enough to entrain the heaviest particles of interest). Down-hole filtering

avoids the need to pump water and particles to

the surface, saving pumping requirements and

avoiding particle damage and losses within the

piping system. Indeed, our design minimizes particle damage and losses by incorporating the filter immediately downstream of the intake slot.

Further development of this concept required

basic data on the number of particles expected (to

determine filter capacity), the flow velocity needed

to entrain the particles of interest, and the pumping losses expected (to size the pump). We also

investigated several fabrication options to incorporate a filter into the collector arm.

Figure 3. Original collector concept (layout and filter arm cross-section).

5
Particulate concentrations expected

We determined the filter mesh size and required

area using information on the size distribution and

amounts of particulates in Antarctic ice and estimates of extraterrestrial particle concentrations in

Greenland and Antarctic ice.

The number of particulates in Antarctic ice <30

μm have been determined using Coulter counters

(unpublished data from E.M. Thompson) and by

counting the number of particles from photomicrographs taken using a scanning electron microscope (Higashi et al. 1990). The number of particles

is very high: 20,000 particles/mL of water for sizes

less than 1 μm, and about 7000 particles/mL of

water in the 1–30-μm size range (unpublished data

from E.M. Thompson). These particles are overwhelmingly terrestrial in origin. Thus, to avoid

clogging our filter with terrestrial particles, we

chose a filter fabric with a 53-μm opening. This

should limit our collection to particles larger than

about 50 μm unless the filter plugs significantly.

These larger particles are easy to handle and analyze.

We estimated the fraction of extraterrestrial to

terrestrial particles in Antarctic ice larger than 50

μm using data from Maurette et al. (1991). They

melted 100 tons of Antarctic ice and recovered

about 10 grams of particulate material. This material included 9000 micrometeorites 50 to 100 μm

in diameter, 6500 micrometeorites 100 to 400 μm

in diameter, and 9 micrometeorites larger than 400

μm. Assuming an average density of 2.5 g cm–3,

and taking 75 μm as the average diameter for the

50- to 100-μm-sized particles, 250 μm for the 100-

to 400-μm particles, and 400 μm as the diameter

for particles larger than 400 μm, we estimate that

0.15 g of the 10 g recovered, or about 1.5%, was

extraterrestrial.

Maurette et al. (1987) estimated the micrometeorite flux rate falling on Greenland ice as 6.3 ×

10–6 g m–2 yr–1 for the 50–300-μm size range. Love

and Brownlee (1993) measured the micrometeorite flux rate in space, using the Long Duration Effects Facility, as 40 (±20) × 106 kg yr–1, or 1.2 ×

10–4 to 3.9 × 10–5 g m–2 yr–1. The difference between the LDEF and the Greenland values suggests that 5 to 15% of the particles survive atmospheric passage. Figure 4 shows the size distribution of micrometeorites expected at the SPWW

based on the Greenland flux rate. Our original estimate for the diameter of the SPWW was 15 m

and that 10 m of downward melting (100 years of

deposition) would occur each year. Thus, we expected that yearly collection could yield 0.11 grams

of micrometeorites, or about 105 particles larger

than 50 μm based on the flux rate of Maurette et

al. (1987). However, we expected the first collection in 1995–96 to have three to four times this

amount of material because of the larger ice volume melted to create and operate the well prior to

our deployment.

We also expected the operation of the SPWW

to add particulates to the well. To determine an

approximate count, we asked John Rand to filter

8 L of water from the SPWW through a cellulose

nitrate membrane filter with a 5-μm pore size. We

examined the filter both optically and with a scanning electron microscope. Eleven percent of the

surface area of the filter yielded 15 fibers and 568

particles, most in the 5–10-μm size range. Forty5

3

2

1

0

4

105

104

103

102

106

50 100 150 200 250 300

Mean Particle Diameter (μm)

Number of Particles

Flux Rate (10–6 gm-2 yr-1)

Flux Rate (Maurette et al. 1987)

No. of Particles in First Year

No. of Particles Released in 1 Year

Figure 4. Number and size distribution of particles >50 μm estimated for

the bottom of the SPWW.

6
four particles were larger than 50 μm. A random

sampling of these particles using an SEM/EDX

found a copper sulfate grain, an alumino silicate

with some CuS on its surface, a fibrous particle

(probably plastic) with some mineral fragments

adhered, a very platey alumino silicate that contained Mg, Ca, and Fe, possibly a clay, several plastic pieces, and four particles containing Fe, Ni, Cr,

Pb, Al, Si, and a trace of S. Most of these particles

probably come from the heat exchanger, pump,

and hoses used to operate the well. Assuming that

the number of particles found in the 8-L sample is

representative of what would be found in 2000 m3

(the amount of water melted during one year of

operation), that all these particles were from the

well equipment, and that they settle to the bottom

and are collected by our device, 108 terrestrial particles would be added to our collection, or about

1000 terrestrial particles for each extraterrestrial

particle larger than 50 μm. Annual collection

would thus yield a total of about 100 g of material.

The 8-L sample also revealed the presence of

submicron particles of iron oxide in the well water. The white, cellulose nitrate membrane filter

turned a bright orangish color after filtration, and

energy-dispersive X-ray analyses of the filter

showed only the presence of iron. The rust is

thought to be from the heat exchangers or pump

used for the well. Until January 1994, the water in

the SPWW was acidic (pH 4.8), very soft,* and corrosive to metals. NSF has neutralized the water

(pH 6.9) by running it through a limestone bed.

This measure may diminish the formation of iron

oxide. In addition, a fire retardant (Ansul dust,

similar to baking soda) was used during the 1994

well fire. Particles of this fire retardant, soot, and

melted insulation could also have reached the well

pool, although most should have deposited along

the well neck.

PUMPING REQUIREMENTS AND

PRELIMINARY TESTS

Our collector design allowed for almost 1 m2

of 30-cm-wide filter fabric inside a 3-m-long filter

arm using a single fold of the filter to create a

pouch. We obtained a polyester filter consisting

of 53-μm mesh openings and 108 openings/m2.

Thus, 1 m2 of this filter should trap the expected

108 particles before plugging. Design guidance

suggested using a pressure drop of 34 kPa (5 lb

in.–2) across the filter to determine pumping requirements. We expected that this loss would

dominate all pumping losses.

We estimated the required pumping rate from

the velocity needed to entrain 1-mm-diameter

sand particles in water (ASCE 1975). The average

velocity in the intake slot must exceed the particle

fall velocity of about 10 cm/s to carry these particles into the filter. In addition, the friction velocity between the filter arm and the ice surface must

exceed the threshold value to initiate particle

movement of about 3 cm s–1. This requires that

the average flow exceed about 15 cm s–1, if we assume that the gap between the filter arm and the

ice surface is about 1 mm. Both conditions are met

if the average velocity exceeds 30 cm s–1 in a 1-

mm-wide intake slot (or 15 cm s–1 in a 2-mm-wide

intake slot). We selected a compact, submersible

pump that could deliver 1.6 L s–1 at 34 kPa or about

50 cm/s through a 1-mm-wide × 3-m-long intake

slot. Near zero pressure, the pump delivers about

3 L s–1 (100 cm/s through a 1-mm-wide × 3-mlong intake slot).

We expected that the high-pressure drop

through the filter and the narrow intake slot would

establish relatively uniform intake velocities along

the slot. Nevertheless, we conducted flow tests on

a 30-cm-long × 13-cm-wide model of the filter arm

(front-slot version, Fig. 3) to verify particle pickup

and assess the velocity distribution. This model

contained pressure taps that allowed us to measure the pressure drop across the intake, the filter,

and the plenum areas at three cross-sections along

the collector. We also measured the total flow rate.

For these tests, we prepared mixtures of simulated

extraterrestrial particles consisting of stainless steel

and glass spheres and silica sand, covering a size

range of 50–420 μm.

We found no appreciable plugging of the filter

(negligible increase in pressure drop across filter,

negligible decrease in flow rate) even after collecting 68 g of material. The maximum pressure drop

across the 53-μm filter was 4.2 kPa, and the corresponding minimum flow rate was 0.31 L s–1 (representing 100 cm s–1 through the 1-mm-wide × 30-

cm-long intake slot). The collector model easily

suctioned up particles lying several millimeters in

front of the intake. However, because the flow

velocity drops quickly inside the collector, the collected particles were deposited on the bottom of

the filter pouch downstream of the slot rather than

evenly plugging the fabric.

*H. Mahar, 1996, National Science Foundation, personal

communication.

7
These tests also revealed several disadvantages

of our original, front-slot design: (a) filter installation was awkward, (b) it would be difficult to control the slot width if the arm was made from flexible plastic, and (c) the flow-collecting plenum

channel downstream of the filter needed to be

larger to reduce the pressure drop (and hence

maintain a more uniform intake velocity distribution) along the collector arm.

For these reasons, we modified the collectorarm design to produce a central intake slot and a

flow plenum channel along each side (Fig. 5). The

arm can be fabricated from a machined and folded

piece of low-density polyethylene (LDPE). O-rings

secure the sides of the filter fabric adjacent to the

intake slot, and folding results in a filter pouch.

End caps with O-rings seal the filter pouch and

prevent flow leakage. Aluminum ribs spaced

along the arm maintain the geometry of the arm

and slot and prevent collapse of the plastic under

suction. Although this design draws flow equally

from both directions under the collector, resulting

in lower velocities along the ice surface, we felt

the manufacturing, assembly, and flow-distribution advantages outweighed this disadvantage.

We conducted flow tests on a 30-cm-long × 18-

cm-wide model of the central-slot collector arm.

This model developed better flow distribution, as

evidenced by a lower pressure drop through the

filter and negligible pressure drop along the plenum channels. It also easily suctioned up the test

particles. No appreciable plugging of the filter occurred even though it collected almost 200 g of

material, and the resulting minimum flow rate was

0.33 L s–1. It was also much easier to install and

remove filters with this model. With careful machining, a relatively uniform intake slot was

formed by folding and securing the two sides of

the arm.

An important modification resulted from these

tests. We found that particles could escape back

through the intake slot when we pulled the collector out of the water and the pump lost suction.

To prevent this “backflushing” of particles, we

installed a thin strip of 1-μm filter fabric (later

replaced with a strip of thin LDPE) to serve as a

flow check valve. This solved the backflushing

problem.

FINAL DESIGN

We constructed two fully operational collectors

based on the central-slot design. We initially built

a 1.2-m-long prototype to assess the design’s

maneuverability and collection efficiency on iced

surfaces. This prototype also provided us with a

shorter, more maneuverable collector to use in the

SPWW as an alternative to the 3-m-long device

originally planned.

Figure 6 shows the basic features of the 1.2-m

collector. The filter arm consists of a single machined and folded sheet of LDPE with the same

internal layout as the 30-cm-long model (Fig. 5).

This arm is quite flexible, allowing the collector to

conform to a surface curvature of about 2 m radius (30 cm rise over 1.2 m). The LDPE also exhibits low friction on wet ice. A central, waterproof

aluminum housing contains the pump and drive

motors and all electrical connections; the externally

mounted pump housing is also aluminum. O-rings

seal the removable end plates and motor shafts.

Traction is via heavy, stainless steel, spiked wheels

driven by DC gear motors through articulated aluFolded LDPE

Flow Channel

to Pump

O–Ring

2 mm Intake Slot

Thin LDPE Strip

(check valve to prevent

back–flushing)

Filter Fabric

(53 μm mesh)

Aluminum Rib

Figure 5. Final collector-arm cross-section.

8
minum shafts. The manufacturer rated these motors for a continuous duty torque of 4.6 N·m. At

each end of the arm, heavy aluminum assemblies

guide the motor shafts and help the collector conform to surface curvature. In addition, one of these

end assemblies contains an internal flow passage

(manifold) to connect the pump to the two plenum chambers along the arm.

An electromechanical cable connects to the central housing via a waterproof connector. This custom-made, LDPE-jacketed cable contains 19 electrical conductors to operate the collector, underwater video camera, and lights at the SPWW. It

also contains an internal Kevlar braided jacket,

with a rated breaking strength of 4500 N, to act as

a strength member. Mechanical attachments at the

housing and end assembly transfer the weight of

the collector to the cable. This 17-mm-diam. cable

is quite flexible and can bend to a minimum radius of 30 cm at –50°C. All collector and cable components were accepted for use in the SPWW. Figure 7 shows a schematic of the 1.2-m collector,

cable, camera, and lights in the SPWW.

We also constructed a 2.4-m-long, central-slot

collector (Fig. 8). We chose this length for the filter

arm because the longest sheet of LDPE available

to us was 2.4 m. This collector utilizes similar components but is completely independent of the 1.2-

m collector. It possesses two waterproof housings,

each fitted with a pump and drive motor. Both aluminum end assemblies contain internal manifolds

to connect the pumps to the plenum chambers in

the arm. We can replace one drive wheel and motor with a 90° gear box and rotation transducer to

measure the rotation of the arm around a pivot

point. The same electromechanical cable operates

either collector. Many of the individual components are interchangeable between the 1.2-m and

2.4-m collectors, providing a level of redundancy;

we also purchased numerous spare parts, including a second electromechanical cable.

The underwater video camera consisted of a

high-resolution color camera and a zoom lens

mounted inside an aluminum pressure housing

(rated to 1000-m water depth). A thermostatically

controlled heater ensured normal camera operation at –50°C. Two independently operated 500-

W waterproof lamps provided illumination, with

one projecting sideways from the collector and one

projecting downward from the camera. Waterproof connectors connected the camera and lamps

to the electromechanical cable. This equipment

was operated through a video control unit and a

video monitor at the surface.

The video system provides the visual feedback

needed to maneuver the collector. We control the

rotation speed and direction of drive motors using two DC power supplies at the surface. Current limiters ensure operation of the motors below their continuous-duty torque ratings. A simple

rectifier and switch are sufficient to operate the

collector pumps. We can monitor the current

drawn by the pumps to determine the approximate flow rate.

A reversible, constant-speed winch raises and

lowers the collector via the electromechanical

cable. A set of slip rings provide electrical connections between the rotating cable and the stationary surface equipment. The cable passes over a 76-

cm-diam. sheave mounted on top of a 3.6-m high

Figure 6. Major components of the 1.2-m operational collector.

9
tower and then connects to the collector (Fig. 8).

The tower allows the collector to hang vertically

before descending through the well neck; it also

allows the cable to warm slightly during ascent

before bending over the sheave. The winch, tower

assembly, and video and collector control equipment fit inside the winch room located directly

above the second access hole to the SPWW

(Fig. 2).

Prototype tests and modifications

Validating the performance of our particle collection system prior to its first use at the South

Pole was an essential step in our design plan. We

arrived at the final collector designs through a series of laboratory tests, primarily using the 1.2-m

collector prototype. The goals of these tests were

to assess the collector’s maneuverability and collection efficiency on submerged, iced surfaces and

to make modifications as warranted before building the 2.4-m collector. We used two main test facilities: a 1.5 m × 1.5 m × 0.3-m-deep tank with a

cold plate on its bottom to grow a flat layer of ice,

and a 2.5-m-wide × 6-m-long × 3.6-m-high iced

ramp with a curved parabolic profile that approximated published shapes for earlier Rodriguez

wells (Schmitt and Rodriguez 1963, Russell 1965,

Williams 1974, Lunardini and Rand 1995). We

Figure 7. Schematic of the 1.2-m collector in the SPWW.

Center of Well

Camera and Lamp

Collector

Overall Length......120 cm

Maximum Height........23 cm

Width........20 cm

Central Plateau

Particulate

Concentrations 30-60 cm

 1-1.5 m 4-5 m

30-60 cm

10
could submerge the iced ramp in a 9-m-wide ×

37-m-long × 2.4-m-deep refrigerated basin. This

provided the most realistic simulation of the collector’s operation in the SPWW; however, we were

unable to conduct quantitative collection-efficiency tests with this arrangement.

We quickly found that collector maneuverability was very good on both the flat and curved iced

surfaces. The heavy spiked wheels provided excellent traction, and motor torque was adequate

for the collector to climb up the ramp to a location

with a 45° downward slope. Pump suction did not

affect collector mobility.

We conducted four quantitative collection efficiency tests, all using the 1.2-m collector in the 1.5-

m iced tank. In all four cases, we used a 53-μm

polyester filter and a 5-cm-wide strip of LDPE as

a check valve. We again used mixtures of stainless

steel, glass spheres, and silica sand to simulate

micrometeorites in a size range 60–400 μm. We

weighed the particulates added to the tank before

testing and the particulates recovered from the

collector filter after testing to determine the overall collection efficiency. Table 2 summarizes the

results of these tests.

The ice surface formed on the cold plate was

quite flat across the tank (with only 3- to 5-cm-wide

strips of thinner ice along the tank walls) and generally very smooth (with only a few isolated depressions 1–2 mm deep and 1–2 cm wide, made as

we added water to fill the tank). We tested the collector on this smooth ice during the first, and half

of the second and third, collection-efficiency tests.

For half of the second and third tests and all of the

fourth test, we roughened the ice with a water jet

to create numerous depressions 2–10 mm deep and

1–2 cm wide.

The collector suctioned test particles very well

from smooth ice surfaces, collecting almost all the

particles in a single pass. Particles remaining after

the first pass were usually concentrated in the local depressions. Each additional pass would retrieve some particles from the depressions, but the

collector would not generally clean them entirely.

Nevertheless, the first three tests all yielded collection efficiencies over 99% (Table 2) despite the

presence of intentionally roughened ice during half

of the second and third tests. Interestingly, the collector achieved these high collection efficiencies

despite leaving clearly visible patches of particles,

mostly concentrated in the depressions but also in

Figure 8. 2.5-m operational collector suspended from

the cable on a winch.

Table 2. Summary of quantitative collection efficiency tests. All tests were conducted in 1.5-m iced tank.

Material Material

added recovered Percent

Date (g) (g) recovered Remarks

29 Jun 390.1 387 99.21 Smooth ice, multiple passes

30 Jun 100.1 99.54 99.44 Smooth ice surface 50 g, rough ice 50 g

6 Jul 100.0 99.46 99.46 Smooth ice surface 50 g, rough ice 50 g

10 Jul 231.51 206.38 89.15 Rough ice surface

11
lower concentrations on the flat ice. For example,

the second test left only 0.6 g of the 100.1 g of particles added, yet particle patches were clearly visible.

The collector had much more difficulty collecting particles from the extensively roughened ice

surface made for the fourth collection efficiency

test. It achieved a collection efficiency of only about

89%. Some of the remaining particles, however,

were frozen onto the bottoms of the depressions,

suggesting that the test technique may have affected the recovery. Nevertheless, we did not know

what the SPWW bottom roughness would be like,

and we wanted to develop a method to retrieve

particles easily from rough ice.

We made several minor modifications to the collector during the collection-efficiency tests based

on the observed performance. The first test revealed that the flat-bottomed collector could press

particles into very flat ice and be unable to collect

them. We subsequently tested the collector with

1.5-mm-diam. Teflon-coated wires wrapped

around the filter arm at the locations of the internal ribs. We tested these “runners” during the second and third tests and found that the collector

did not press the particles into flat ice and it

achieved good collection efficiency. However, the

collector could retrieve particles better from deep

depressions without these runners. We still

brought a quantity of this wire to the SPWW for

use if the well-bottom ice appeared to be very

smooth (we did not use it).

We also developed (but again did not use in the

SPWW) a method to retrieve particles from rough

ice. This involved attaching an 8-cm-wide strip of

thin LDPE (the same material used for the check

valve) to the underside of the collector arm adjacent to the slot. This external flap would seal itself

to the ice surface when the pump was on. Flow

could only bypass the flap though deep depressions, effectively cleaning these depressions of

particles, or by entering the slot from the other side

of the collector, essentially doubling flow velocities. We tested this arrangement in a separate collection efficiency test on very rough ice. It picked

up particles extremely well, even from 1-cm-deep

depressions, and left the ice visibly clean after a

single pass. Unfortunately, the shipping deadline

prevented us from conducting a quantitative

collection efficiency test, but the visual evidence

from the test conducted suggests that it would

have been greater that 99%.

We routinely measured flow rates through the

1.2-m collector during the collection efficiency

tests. The flow rate was consistently 2.1 L s–1,

independent of ice conditions, the presence of runners, and the amount of material collected (up to

a maximum of 212 g preceding a flow measurement). Unlike the 30-cm-long model, however, it

was difficult to achieve a uniform slot width along

the 1.2-m-long prototype. For the first two collection efficiency tests, the slot width averaged about

1 mm, but varied between about 0.5 and 1.5 mm.

This yielded an average gap velocity of about 170

cm s–1, much higher than that needed for particle

pickup. Because we were concerned that the narrow slot sections corresponded to areas of poor

particle pickup, we attempted to machine the slot

to a uniform width of 2 mm. We achieved an average slot width of 1.64 mm (Fig. 9), but local variations ranged from just under 1 mm to 2.8 mm. This

yielded gap velocities that ranged from 64 to 190

cm/s and averaged 125 cm s–1 (assuming a uniformly distributed total flow of 2.1 L s–1), well exceeding the target minimum of 10 cm/s. This velocity distribution did not appear to affect overall

collection efficiency (the collector recovered over

99% of the particles deployed on combined smooth

and rough ice during the third test), and we no

longer saw any correlation between narrow slot

width and poor particle pickup. We made no further changes to the slot prior to field deployment.

We also conducted particle-collection tests using the 1.2-m collector in the iced ramp, submerged

in the refrigerated basin. Although these tests were

qualitative, visual evidence indicated good collection efficiency where the collector contacted the

surface. However, the collector left particle patches

on the ramp in areas where it did not conform well

to the surface shape. We therefore added weight

inside the waterproof housing to allow the collector to conform to more severe surface curvature.

The modifications resulting from these tests on

the 1.2-m collector were essentially options to improve collection efficiency on very smooth, rough,

or curved ice and did not affect the basic design.

Thus, we constructed the 2.4-m collector essentially as designed (see Appendix B for a summary

of the collector development tests).

We tested the 2.4-m collector only on the iced,

submerged ramp. The collector was quite maneuverable and could sweep across a region with a

45° upward slope. However, as with the 1.2-m collector, we added extra weight near the center of

the collector to help it conform to the ramp and

thereby improve its collection efficiency (documented visually). The spiked wheels could slip or

cut through the ice at the steeper ascent angles, so

12
to increase traction we manufactured longer drive

shafts that could accept a double set of heavy,

spiked wheels. These same long shafts and the

spare wheels also fit the 1.2-m collector (optionally to increase its traction).

In addition to these tests on the assembled collectors, we cold-soaked individual components

(silicone hoses, LDPE filter arm, O-rings, etc.) at

–65°C in a liquid-nitrogen-cooled chamber

(Tantillo 1993) to check their flexibility and durability. We also suspended each collector from our

tower and sheave to ensure that they hung true.

Deployment

We sent two fully operational collectors to the

South Pole with the means to make modifications

to each should the well-bottom conditions be different from our expectations. We also shipped a

winch, tower, and sheave, two 200-m electromechanical cables, a video camera, monitor, and recorder, spare pumps, filter fabric, and motors and

various tools that we needed for assembly and

repair of the collector in Antarctica. The operation

of all these components was checked before shipping. The collectors and cables were disinfected

using a 1:60 solution of Clorox® to water and were

wrapped in plastic to stay clean during transit.

At the Pole, personnel from Antarctic Support

Associates (ASA) assisted us in many ways. Their

main task was to build the surface facilities that

would provide us access to the SPWW and create

an adjoining work space. They first dug a pit

(about 3 m × 3 m × 3 m) in the snow adjacent to

the existing wellhouse and down to the EPDM

liner. We then cut a 30-cm square opening in the

liner, and ASA constructed and installed an EPDMlined wooden chimney over the opening. We

sealed the chimney to the opening. This process

ensured continuity of the EPDM liner around our

access hole and work area. ASA then carefully

backfilled the pit with snow and constructed our

work space. This work space consisted of a winch

room directly over the chimney and an adjoining

laboratory (Fig. 10).

We used a hot-water drill (Fig. 11) to make the

second access hole to the SPWW; ASA also assisted

with the drilling. Water from the well was heated

in boilers located in the wellhouse and fed into

the 30-cm-diam. cylindrical drill via a neoprene

rubber hose. This hot water discharged through a

90°-cone nozzle to melt the ice as the drill descended. A water pump positioned inside the drill

pumped water from down-hole to the surface via

a return hose. The drill was lowered using a winch

and stainless steel cable. The hoses were attached

to the cable with stainless clamps and cloth ties.

The cable was guided into the hole using a sheave

suspended from a spring scale. The scale allowed

us to determine whether the drill was suspended

in air, was on ice, or was in water; this set the drilling rate. Drilling took about 36 hours, longer than

expected, but yielded a vertical, wavy-walled access hole with a minimum clearance of 30 cm in

diameter.

Prior to collector deployment, we lowered the

video camera to examine the hole and inspect

the well-bottom topography. We noticed that an

ice cover had formed on the well pool and that

the access hole through it had refrozen (we would

need to break through this ice cover before each

0

3

2

1

0

40

80

120

160

200

0 20 40 60 80 100 120

Distance (cm) from Pump End

Slot Width (mm)

Gap Velocity (cm s-1)

Slot Width (mm)

Average Slot Width (mm)

Average Gap Velocity (cm s-1)

Gap Velocity (cm s-1)

Figure 9. Slot width measured along the 1.2-m collector prior to

deployment. Also shown is the corresponding gap velocity, assuming a uniform distribution of 2.1 L s–1 total flow.

13
collector deployment). More importantly, the camera revealed that the well bottom contained isolated dark pockets of particulates and that

these pockets coincided with sculptured features

in the ice that were arcuate and half a meter

deep. We decided to deploy the 1.2-m

collector because it could more easily negotiate

the sculpted topography than could the 2.4-m

collector.

We successfully deployed and retrieved the 1.2-

m collector six times and obtained five separate

collections (one filter deployed twice) totaling

about 200 g of material. Appendix C lists the deployments and shows the collector configuration

for each. The collector provided a scale upon

which to judge the well-bottom topography. It was

much more complicated than we expected based

on published shapes of earlier Rodriguez wells

(Schmitt and Rodriguez 1963, Russell 1965, Williams 1974, Lunardini and Rand 1995). It consisted

of a gently curved central plateau (about 18 m2)

sculptured at its periphery into fairly steep arcuate dips that were 0.3–0.6 m below the plateau and

1–3 m wide; these dips led to smaller plateaus (1–

3 m2) (Fig. 12). Farther away from the center, the

bottom rose steeply and the sculptured features

appeared to be more severe (either deeper or at

Figure 10. Work space at the SPWW, consisting of a winch room directly over the access hole and an

adjoining laboratory.

Figure 11. Hot-water drill used to drill second access

hole to the SPWW.

14
shorter length scales). Associated with most sculptured features were dark pockets of particulates.

Particles on the plateau areas were visible but not

concentrated into pockets. Local surface roughness

was quite smooth (perhaps 1-mm depressions over

1–5 mm scales). For this reason, we did not use

the Teflon-wire runners or external LDPE flap

(developed for very smooth or rough ice, respectively).

The collector maneuvered easily over the central plateau, and we devoted one collection (no. 3)

exclusively to the plateau. Movement onto the adjoining dips and plateaus was possible with some

practice, and we collected from five of these (about

10 m2 total), including three particle pockets. We

collected as much as 50 g of material at once

without appreciably reducing pumping efficiency.

Plateau areas suctioned were visibly clean, and

gently curved dark areas changed from black to

white with a single pass. This indicated high-efficiency particle pickup, based on our laboratory experience.

Good contact between the collector bottom and

the ice surface was the most serious limit to collection efficiency in severely curved areas, and we

maneuvered the collector slowly across the associated pockets to maintain good surface contact.

This technique worked well but was very timeconsuming. During some deployments, the field

of view of the video camera limited our ability to

maneuver the collector. We tried several techniques, unsuccessfully, to orient the camera to follow the collector.

The spiked wheels, often doubled on each end,

provided extremely good traction on the ice. The

allowable motor torque, rather than traction,

generally limited collector maneuverability on

steep sections, although collector stability was also

a factor. We normally worked around these limitations quite successfully, and could have substantially increased the area suctioned within the performance capabilities of the 1.2-m collector. Unfortunately, after about two hours of maneuvering during a deployment, the drive motors failed.

Post-deployment inspection revealed that shearing of gear teeth in each motor’s gearbox caused

the failures. This repeatedly occurred, despite

readouts from the drive-motor power supplies that

indicated operation at about half of the continuous-duty torque rating provided by the motor

manufacturer. After all four motors had failed once

(by deployment no. 4), we continued to run the

collector by interchanging gears between gearboxes; this provided us with about two hours of

operation before motor failure for deployments 5

and 6.

We had planned to dedicate deployment no. 4

to repeat suctioning of the central plateau. This

would have allowed us to calculate in-situ collection efficiency. Unfortunately, one drive motor

failed at the start of that deployment, and we only

covered about one third of the central plateau.

Upon retrieval of the collector, we found very little

material in the filter bag and decided to reuse it

for the next deployment to save time. Although

not quantitative, the results of deployment no. 4

and the visually apparent cleaning of particles

from the ice suggests a high in-situ collection efficiency.

SAMPLES

After each deployment except no. 4, we brought

the collector to the laboratory space and removed

the polyester filter from the filter arm. The white

flexible fabric allowed us to see particles and easily remove them by backflushing the filter. We

backflushed each of the two samples we processed

into a large HDPE funnel, using well water that

we pressurized in an HDPE hand sprayer. Each

sample, one from a pocket, the other from the plateau, was then wet-sieved into stainless steel sieves

Plateau

Pocket 1

Pocket 5 and 6

Collector

Figure 12. Map of the bottom of the SPWW showing

the plateau area and pocket no. 1.

15
yielding 50–106-μm, 106–250-μm, 250–425-μm,

and >425-μm size fractions. Using a binocular

microscope, spheres were separated from these

two samples by hand picking (Fig. 13). These two

samples were processed in the field to assess the

collector’s performance and to determine the type

and amount of materials recovered. The remaining three samples were placed in bags, sealed, and

shipped to CRREL for later analysis.

Other than well water, no solvents were used

in the separation process. We collected aliquots of

everything the particles may have come in contact with (drilling water, water, and residue left

after backflushing and sieving a collection). We

also exposed a section of clean filter to the

wellhouse environment, as suggested by Michael

Zolensky. These samples can be analyzed if any

unexpected contaminants are found in the particles.

About 200 g of material were recovered from

the well bottom. Most of the material was terrestrial (Fig. 14), predominantly rust grains injected

into the well and originating either from the heat

exchanger or from the non-stainless steel components within the pump. There were also wood

fragments, paint chips, wire, and aluminum flakes.

Our initial examination of the collected sediment focused predominantly on spherical particles. Although not all spherical particles are extraterrestrial (there were copper spheres formed

when pipes were soldered and dark, nonmagnetic

“glue balls” thought to have formed during the

fire), spheres can be rapidly separated with an ordinary binocular microscope. Those that are “cosmic” can then be separated by their several unique

properties. Previous studies have shown that cosmic spherules have distinctive mineralogy, bulk

chemistry, internal and surface textures, and are

usually moderately magnetic (Brownlee 1981).

Here we used their abundance as a measure of the

amount of extraterrestrial material in our samples.

All 6.01 g of the 250–425-μm size fraction of

pocket collection no. 1 and all 3.5 g of the 250–

425-μm size fraction of the plateau collection were

examined. Table 3 lists the number of cosmic

spherules found in these two fractions. Assuming

an average particle weight of 3.5 × 10–5 g/particle

(300 μm diam., 2.5 g cm–3) gives a weight of 7.9 ×

10–3 g for the pocket collection and 4.4 × 10–3 g for

the plateau collection, or about one part per thousand melted meteoritic material. In addition to the

250–425-μm size fractions, 0.56 g of the 23.8 g of

the 106–250 μm and 0.15 g of the 12.67 g of the 53–

106 μm were also examined for the pocket collecFigure 13. An assortment of spherules from the SPWW. The large sphere in the upper left

corner is a copper contaminant (×40).

300 μm

16
Figure 14. ‘Sediment’ retrieved from the well (×10).

Table 3. Size range and weight of the pocket and plateau samples.

Pocket Plateau

Size range Weight No. of cosmic Flux Weight No. of cosmic Flux

(μm) (g) spherules (g m2 yr–1) (g) spherules (g m2 yr–1)

>425 6.4 5.4

250–425 6.0 224 7 × 10–6 3.5 126 6 × 10–7

106–250 23.8 5.1

53–106 12.7 2.9

Total 48.9 16.9

Area covered 5 m2 17 m2

17
tion. If the subsamples are representative of the

entire size fraction, then there are 2 × 10–3 g g–1 of

material in the 106–250-μm size fraction.

The types of cosmic spherules found in the

SPWW were assessed by mounting particles from

the 250–425-μm and 106–250-μm size fraction

in epoxy, sectioning them, and examining them

using the Cameca SX-50 electron microprobe at

the University of Tennessee, Knoxville. We found

the full range of cosmic spherule morphologies

(Table 4).

Photomicrographs of SPWW particles are presented in Figure 15a–h. Glass spherules are composed of mafic glass and represent particles that

have been fully melted, devolatilized, and rapidly

quenched during atmospheric entry (Fig. 15a).

Cryptocrystalline spherules are predominantly

glassy particles with crystallites too small to be

individually recognized, surrounded by an ironrich glass (Fig. 15b). Barred olivine spherules are

particles that have also been fully melted but that

were less rapidly quenched, allowing olivine and

magnetite crystallites to form (Fig. 15c). Relic-grainbearing spherules are particles that did not fully

melt before quenching and retain “meteoritic”

minerals, surrounded by an iron-rich glassy rim

(Fig. 15d). Volatile-rich spherules are vessiculated

particles showing regular to irregular cavities and

lots of relic olivine, metal, or sulfide grains; they

represent particles quenched quickly after initial

heating, before full devolatilization could occur

(Fig. 15e). The G-type are high-iron spherules and

contain magnetite dendrites in a glass matrix (Fig.

15f). Iron spherules (I-type) are wholly metallic (Fig.

15g) and show meteoritic siderophile concentrations. Unmelted IDP-like particles have compact,

irregular texture, with iron-rich rims around dispersed voids and relic olivine grains (Fig. 15h).

When compared to the other large collections

of cosmic spherules—the Deep Sea spheres

(Brownlee 1979) and the Greenland spherules

(Maurette et al. 1987)—the SPWW materials are

most similar to particles collected in Greenland

(Table 5). The main difference is the higher proportion of glassy spheres and the lower percentage of unmelted materials in the SPWW collection.

However, the fraction of unmelted micrometeorites in the SPWW will increase as we systematically look for them. The major differences between

the SPWW spherules and those found in deep-sea

sediments are the increase in glass spherules found

and the paucity of iron and G-type spherules. This

is true both for magnetically and nonmagnetically

collected deep-sea spheres (Taylor and Brownlee

1991).

Twenty spherules from the pocket sample were

analyzed using a Zeiss DSM962 at Dartmouth

College. When plotted on a MgO, SiO2, and FeO

ternary diagram (Fig. 16) or on a Ca/Si vs. Al/Si

plot (Fig. 17), the SPWW spherules lie within the

field found for other collections.

Although detailed examinations of nonspherical particles have not yet taken place, the

presence of one relatively large, unmelted particle

in one of our mounts suggests a significant

unmelted ET component. Unmelted particles have

been found by previous studies of particles retrieved from melted Antarctic snow and ice. Further studies will incorporate a detailed examination of the nonspherical particles in the sediment.

Weathering

The barred olivine spherules show various degrees of weathering with preferential removal of

Fe-rich glass interstitial to Mg-rich olivine bars.

Some stony spherules retain a glassy rim (Fig. 18),

while others show 10–20-μm grooves at their margins and occasionally significant removal of glass

in their interiors. The one G-type spherule has a

highly weathered core (Fig. 15f), and the iron

spherule has lost the interstitial nickel-rich phase

near its periphery (Fig. 15g). The weathering is

probably caused by the acidic water in which the

particles were immersed for up to 4 years. How

weathering has affected unmelted particles in not

yet known.

Flux rates

A terrestrial flux rate for meteoritic material 50–

300 μm was obtained from Greenland ice

(Maurette et al. 1987). To make this flux calculation, Maurette and his colleagues estimated the

concentration of sediment in mature cryoconite

Table 4. Types of extraterrestrial particles in the

pocket sample, 106–425 μm.

Glass 14

Cryptocrystalline 11

Barred olivine 51

Relic grain-bearing 7

Volatile-rich 3

High iron (G-type) 1

Iron 1

IDP-like 1

Total 88

18
Figure 15. Backscattered electron

photomicrographs of selected

SPWW micrometeorites that include: a) a glassy spherule showing a bright network of convection borders; b) a cryptocrystalline to fine-grained spherule; c)

a barred olivine spherule; d) a

spherule containing several relic

grains and small distributed

FeNi patches; e) a volatile-rich

spherule showing large irregular internal cavities; f) a G-type

spherule containing magnetite

dendrites in iron-rich glass; g) a

metallic FeNi particle showing

small ameoboidal domains and

meteoritic composition; h) an

IDP-like particle showing a Mgrich phyllosilicate matrix, distributed relic FeNi metal and

sulfide grains, and Fe staining

at the rim and surrounding interior voids.

a b

c d

e f

g h

19
1

0.1

0.01

0.01 0.1 1

Al/Si

Ca/Si

Figure 17. Weight percent Al/Si and Ca/

Al plot of the SPWW spherules as compared to DSS and chondritic value.

Figure 16. Ternary diagram illustrating where the analyzed SPWW

spherules plot in relation to the Deep

Sea and Greenland spherules.

Table 5. Comparison of SPWW spherule types with those found in Greenland and in the Deep Sea

collection.

Relic Crypto- Barred

No. of Unmelted grains Glass crystalline olivine G-type Iron

spheres

examined (%)

SPWW 88 5 8 16 12 57 1 1

Greenland 92 18 10 5 9 55 1 1

Deep Sea spheres 778 5 9 1 2 52 5 26

 (magnetically

 collected)

Deep Sea spheres 146 6 10 1 5 44 7 27

 (nonmagnetically

 collected)

Greenland and 

Deep Sea Spheres

South Pole Water Well Spherules

Pyroxene

Olivine

SiO2

MgO FeO

20
deposits on the ice surface, estimated the age of

the ice melted to form the deposits using an ice

flow model, and assumed that all particles deposited had been collected. We have calculated a terrestrial flux rate for melted micrometeorites larger

than 250 μm for the pocket (7 × 10–6 g m–2 yr–1)

and the plateau (6 × 10–7 g m–2 yr–1) collections;

the latter is the same value found by Maurette et

al. (1987) for their 250–300-μm size fraction. We

know the volume of firn and ice melted to 10%

and the age of the ice to 50 years (the uncertainty

is due to the topography at the bottom of the well),

and the area cleaned was determined from the

video. Since we collected from 7% of the well bottom, the accuracy of our flux measurement will

depend on the movement of particles along the

bottom.

From the video footage we estimate that we collected from an area of 30 m2, or about 7% of the

well bottom. The pockets preferentially contain

iron-oxide grains derived from the water-supply

system; the circulating flow can easily concentrate

this injected material. The order-of-magnitudelarger flux estimate for the pocket as compared

with the plateau, however, suggests that the well

circulation is also concentrating micrometeorites

into the pockets. This is despite the relatively small

flow rate (about 1 L s–1) discharged about 13 m

above the bottom and no trace of particle transport even with the collector nearby to act as a local disturbance. Perhaps the compressed air entrapped in the ice releases bubbles into the water

as the well melts downward, and this agitation

helps to entrain the micrometeorites.

It is not clear whether or not the particles are

being removed from the plateau into the pockets;

the micrometeorites in the pockets may come from

the well sides. If micrometeorites are not being

moved from the plateau area, repeat collections

of the plateau could provide information on flux

rates and on any temporal changes in the type and

number of micrometeorites. Detailed analysis of

the separate collections from the central plateau

and the isolated pockets will reveal the degree of

micrometeorite concentration possible by the circulating flow.

CONCLUSION

We have successfully recovered extraterrestrial

materials from a polar well. This is thought to be

one of the largest and best preserved collection of

micrometeorites, and it is the best dated. This collection will allow us to calculate flux measurements of cosmic dust larger than 50 μm and will

Figure 18. Photomicrograph showing a glass rind around a stony spherule.

21
give us an understanding of the breadth of

materials present in the solar system in this size

range.

Our collector worked well despite the severe

well topography. We learned that a 2.5-m collector is too long and is not needed for the conditions we encountered; that available motor torque

(rather than traction) limited the collector’s mobility over the well bottom; and that visual feedback is essential to negotiate the well’s complex

topography (our camera lacked the ability to track

the collector more than 5 m away from the center). We hope to install more powerful motors and

a pan/tilt camera to overcome these problems and

thus to increase the collection area and operational efficiency. However, the more severe topography away from the center of the well dictates

the need for a second, smaller, and more agile

collector.

The complex bottom topography in the SPWW

precluded our suctioning the entire bottom. We

suctioned a gently curved, central plateau (about

18 m2) and three surrounding pockets (about 12

m2 total) and should be able to return to these areas annually to determine flux rates. From the five

collections, we retrieved approximately 200 g of

material. Microscopic examination of the 250 to

425-μm size fraction from two of the five collections suggests that one of every 1000 particles in

this size fraction is a melted micrometeorite. Not

counted are the unmelted micrometeorites present.

We think the flux value for the plateau of 6 × 10–7

g m–2 yr–1 is a minimum. The circlation velocities

seem too low to add particles to the plateau, and

we did not include unmelted particles in this estimate. With unmelted micrometeorites included,

the flux rate we calculate for the SPWW will be

higher than that found by Maurette et al. (1987) in

Greenland.

The particles retrieved will be analyzed and

compared with other cosmic dust collections to determine differences in composition and weathering patterns. Because of the large number of particles recovered, it is likely that very large IDPlike micrometeorites, extremely rare in other collections, will be found. In addition, identification

of the terrestrial components (pollen, diatoms, ash,

etc.) from these samples would allow a statistically

significant study of circum-Antarctic wind circulation during these time periods.

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23
APPENDIX A: SPWW DIMENSIONS

Table A1 contains measured well dimensions from the SPWW log book and measured water consumption from weekly South Pole situation reports (sitreps). Bottom depth (D) is the distance from the wellhouse floor to the bottom of the well;

water level (L) is the distance from the wellhouse floor to the top of the water pool;

pool depth (H) is the difference between bottom depth and water level (H = D – L);

dQ/dt is the water volume consumed from the well during the one-week reporting

interval; and Q is the cumulative volume of water consumed during the life of the

well. Figure A1 plots these data as functions of time. Interestingly, the dimensions

vary nearly linearly with time shortly after initial startup and after the restart necessitated by the 1994 fire. Note that freezing of the pool caused a 4-m-thick ice

cover to form between 82.6–86.6 m depth.

Several “draw-down” tests were conducted during the history of the well to

determine its radius (R): a known volume of water was withdrawn from the well

and the drop in water level was measured. However, after consumption began,

withdrawals of about 5 m3 would only yield water-level drops of about 1 ±0.5 cm,

producing large uncertainty in the estimated pool radii. Indeed, the 14 draw-down

tests conducted in March/April 1995 yielded an average radius of 13.1 m with a

standard deviation of 2.4 m. However, because dQ/dt was recorded from the onset

of consumption, we may use these data in a water-balance formula to compute

pool radius.

Figure A2 shows a schematic of the well pool and the resulting changes in dimensions as the pool deepens. The pool volume, initially Vp, increases to Vp + dVp.

This melts additional ice volume,

dV dV R dL i p = +π 2 , (A1)

so the incremental water created is

dV dV dV R dL w pi p p == + γγ π ( ) 2 , (A2)

where γp is the average ice specific gravity along the pool walls. The increase in

pool volume then equals this increase in water created less any water volume consumed. That is,

 

dV dV R dL dQ p pp = + γ π ( ) 2 – . (A3)

Rearranging eq A3 yields an expression for water consumption in terms of changes

in pool volume:

 

dQ R dL dV = γπ γ p pp ( ) 2 – – 1 . (A4)

To use eq A4, we must assume an average shape for the pool. Lunardini and Rand

(1995) assumed that the well would develop a paraboloid-shaped pool. However,

shape data for previous Rodriguez wells (Rodriguez 1963, Russell 1965, Williams

1974, Lunardini and Rand 1995) and observed geometry from our 1995 deployments in the SPWW suggest that an ellipsoidal pool shape would also be a good

approximation. For either case,

V RH p = α 2 where α

π = 2 for a paraboloid

α

π = 2

3 for an ellipsoid (A5)

24
Table A1. SPWW dimensions and water consumption from startup to the end of 1995 collector

deployments.

Bottom Water Pool Estimated

depth level depth dQ/dt Q radius

Date Comments (m) (m) (m) (m3/week) (m3) (m)

1 12/8/92 startup 54.3

2 12/9/92 64.3 59.5 4.9 3.4

3 12/10/92 meas. D=2.7 m 67.1 61.2 5.9 4.1

4 12/11/92 meas. D=3.1 m 68.9 62.3 6.6 4.6

5 12/12/92 meas. D=3.2 m 69.7 62.9 6.8 4.8

6 12/19/92 74.1 65.7 8.4 5.9

7 12/26/92 77.0 67.6 9.4 6.6

8 1/29/93 83.8 73.4 10.3 7.2

9 2/1/93 84.1 73.8 10.3 7.2

10 2/13/93 74.8

11 3/14/93 87.5 76.5 11.0 7.7

12 4/10/93 89.3 78.3 11.0 7.7

13 4/24/93 89.9 79.0 11.0 7.7

14 5/1/93 90.2 79.0 11.3 7.9

15 5/8/93 90.5 79.0 11.6 8.1

16 5/15/93 90.9 79.3 11.6 8.1

17 5/22/93 91.2 79.6 11.6 8.1

18 5/29/93 91.5 79.6 11.9 8.3

19 6/5/93 91.8 80.2 11.6 8.1

20 6/12/93 92.4 80.5 11.9 8.3

21 6/19/93 92.5 80.5 12.0 8.4

22 6/26/93 93.0 80.8 12.2 8.5

23 7/3/93 93.3 80.8 12.5 8.8

24 7/10/93 93.9 81.3 12.7 8.9

25 7/17/93 94.2 81.4 12.8 9.0

26 7/24/93 94.4 81.6 12.8 9.0

27 7/31/93 94.8 82.0 12.8 9.0

28 8/7/93 95.1 82.0 13.1 9.2

29 8/14/93 95.4 82.2 13.3 9.3

30 8/21/93 95.6 82.2 13.4 9.4

31 8/28/93 96.2 82.3 13.9 9.7

32 9/4/93 96.6 82.6 14.0 9.8

33 9/4/93 96.6 82.6 14.0 9.8

34 9/11/93 96.6 82.3 14.3 10.0

35 9/18/93 97.0 82.3 14.6 10.2

36 9/25/93 97.3 82.6 14.6 10.2

37 10/3/93 97.4 82.9 14.5 10.1

38 10/9/93 97.6 83.1 14.5 10.1

39 10/16/93 97.6 83.1 14.5 10.1

40 10/23/93 98.2 83.2 14.9 10.5

41 11/3/93 98.3 83.4 14.9 10.5

42 11/6/93 98.6 83.7 14.9 10.5

43 11/13/93 98.8 83.8 14.9 10.5

44 11/20/93 98.9 84.0 14.9 10.5

45 11/27/93 99.1 84.1 14.9 10.5

46 12/4/93 99.2 84.1 15.1 10.6

47 12/11/93 99.4 84.1 15.2 10.7

48 12/18/93 99.5 84.3 15.2 10.7

49 12/25/93 99.5 84.3 15.2 10.7

50 1/1/94 99.8 84.5 15.4 10.8

51 1/8/94 100.0 84.6 15.4 10.8

52 1/15/94 100.2 84.8 15.4 10.8

53 1/22/94 100.3 84.9 15.4 10.8

54 1/29/94 100.5 84.9 15.5 10.9

55 2/4/94 100.6 85.1 15.5 10.9

56 2/12/94 100.8 85.2 15.5 10.9

57 2/19/94 100.9 85.2 15.7 11.0

58 2/26/94 101.2 85.4 15.9 11.1

59 3/1/94 fire-shut down

60

61

62 11/26/94 repair ongoing

63 11/30/94 shelf to 86.6 m 90.2 82.6 7.6 0.2

64 12/2/94 restart well 90.2

25
Table A1 (Cont’d).

Bottom Water Pool Estimated

depth level depth dQ/dt Q radius

Date Comments (m) (m) (m) (m3/week) (m3) (m)

65 12/3/94 90.2 83.5 6.7 4.7

66 12/3/94 83.4

67 12/4/94 83.4

68 12/6/94 83.6

69 12/7/94 83.8

70 12/11/94 98.6 83.7 14.8 10.4

71 12/16/94 98.8 84.5 14.2 9.9

72 12/24/94 99.0 84.6 14.4 10.1

73 12/31/94 99.5 84.8 14.8 10.3

74 1/4/95 99.7 85.0 14.7 10.3

75 1/7/95 water samples 99.8 85.0 14.7 10.3

76 1/14/95 100.0 85.1 14.8 10.4

77 1/21/95 100.2 85.2 14.9 10.5

78 1/28/95 100.3 85.2 15.1 10.6

79 1/30/95 start consumption 100.5 0.000 10.7

80 2/2/95 100.7 85.5 15.2 32.32 32.320 10.7

81 2/11/95 100.9 85.6 15.3 43.24 75.560 10.7

82 2/18/95 101.4 85.8 15.6 27.30 102.86 10.8

83 2/22/95 pump failed

84 2/25/95 pump replaced 23.33 126.20

85 3/4/95 101.4 85.9 15.5 4.98 131.18 10.9

86 3/11/95 101.5 86.0 15.5 25.47 156.65 10.9

87 3/18/95 101.6 86.1 15.5 24.82 181.48 10.9

88 3/24/95 101.8 86.2 15.6 25.05 206.52 11.0

89 4/1/95 ave. R=13.1±2.4 102.0 86.3 15.6 26.33 232.86 11.1

90 4/8/95 102.1 86.5 15.6 24.04 256.90 11.2

91 4/15/95 102.4 86.6 15.8 25.41 282.30 11.3

92 4/22/95 102.5 86.7 15.9 27.90 310.20 11.4

93 4/28/95 102.7 86.8 15.8 29.53 339.73 11.5

94 5/6/95 102.8 87.0 15.8 25.62 365.35 11.5

95 5/13/95 102.9 87.1 15.8 27.36 392.71 11.6

96 5/20/95 103.0 87.2 15.9 26.04 418.75 11.7

97 5/27/95 103.2 87.3 15.9 26.66 445.41 11.7

98 6/2/95 103.4 87.4 15.9 30.33 475.74 11.8

99 6/9/95 103.4 87.6 15.9 33.48 509.22 11.8

100 6/16/95 103.5 87.8 15.7 30.20 539.42 11.9

101 6/24/95 103.7 87.8 15.9 25.14 564.57 11.9

102 7/1/95 103.7 87.9 15.9 30.71 595.28 11.9

103 7/11/95 103.8 87.9 15.9 26.56 621.83 12.0

104 7/15/95 redrilled hole 26.59 648.43

105 7/22/95 pump repaired 103.9 88.1 15.8 27.89 676.32 12.0

106 7/28/95 104.0 87.9 16.1 28.20 704.52 12.0

107 8/5/95 104.0 88.3 15.7 29.73 734.25 12.0

108 8/11/95 104.1 88.1 16.0 28.01 762.26 12.1

109 8/18/95 104.2 88.4 15.8 29.68 791.94 12.1

110 8/26/95 104.4 88.5 15.9 27.94 819.88 12.1

111 9/1/95 104.5 88.6 15.9 27.28 847.16 12.1

112 9/9/95 104.6 88.7 15.9 26.95 874.11 12.1

113 9/16/95 104.8 88.8 15.9 31.24 905.35 12.1

114 9/23/95 104.8 88.9 15.9 31.31 936.66 12.1

115 9/30/95 104.8 89.1 15.7 30.43 967.09 12.1

116 10/7/95 104.9 89.1 15.8 28.74 995.84 12.1

117 10/14/95 105.0 89.2 15.8 30.28 1026.1 12.1

118 10/21/95 30.74 1056.9

119 10/28/95 37.37 1094.2

120 11/4/95 pump replaced 105.2 89.3 15.9 45.42 1139.6 12.1

121 11/10/95 105.5 89.3 16.2 60.14 1199.8 12.1

122 11/17/95 we arrive 105.5 89.7 15.8 60.41 1260.2 12.1

123 11/24/95 105.8 89.9 15.9 49.72 1309.9 12.0

124 12/1/95 105.9 90.0 16.0 53.25 1363.2 12.0

125 12/8/95 2nd hole done 106.1 90.2 15.9 55.41 1418.6 12.0

126 12/15/95 2 collections 106.2 90.3 15.9 58.89 1477.5 11.9

127 12/22/95 106.3 90.5 15.9 59.10 1536.6 11.9

128 12/29/95 6 collections 106.5 90.6 15.9 65.86 1602.4 11.9

26
Assuming that the shape factor α is approximately constant as the well develops,

the change in pool volume becomes

dV HRdR R dH p = + 2 2 α α (A6)

Inserting eq A6 into eq A4 yields

 

dQ R dL HRdR R dH = γπ γ α α p p ( )( ) + 2 2 – – 1 2 . (A7)

Because water consumption, water levels, and pool depths were measured, we

may use eq A7 to determine pool radius throughout well development. Note that

the specific gravity of ice increases approximately linearly with depth over the pool

depths of interest (Kuivinen et al. 1982):

 

γ p p = + 0 68 0 0028 60 .. – ( ) D , (A8)

where Dp is the average pool depth in meters.

Measurement uncertainties in dL and dH and slight timing differences between

these measurements and those for dQ can yield unrealistic values of R if eq A7 is

31 Dec 92 31 Dec 93 31 Dec 94 31 Dec 95

100

0 0

Dimensions (ft)

Total Well Production Q(m3)

Total Consumption (m3)

Bottom Depth (m) 

Water Level (m) 

Pool Depth (m)

120

80

60

40

20 400

800

1200

1600

2000

Fire Shut-down 

Initial Water Surface

Final Water Surface

Final Pool Shape

Initial Pool Shape

dL

R dR

H

dD

D

L

Figure A1. Measured SPWW dimensions and water consumption.

Figure A2. Schematic of well pool, showing changes in dimensions as the pool deepens. Dimensions (m)

27
solved for each set of values in Table A1. Instead, we generated polynomial curves

that give very good fits to the data and reduce the influence of uncertainties in

these measurements.

There are three periods of interest:

1. From initial startup on 12/8/92 to the fire-induced shutdown on 3/1/94,

2. From restart on 12/2/94 to the start of consumption on 1/30/95, and

3. The period of consumption ending 12/29/95 after our six collector deployments.

Periods 1 and 2

For the first two periods, no consumption occurred. Setting dQ = 0 and using the

substitution x = D – 60, eq A7 becomes

 

dR

dx = cxRx ()() , (A9)

where

 

c x

H x

dL

dx

dH

dx

( )

–

( )

– =





 

 π α 

α

γ

γ

p

p 1

2

 .

The solution of eq A9 is simply

 

R x R c x dx

x

( ) exp ( ) =















 0 ∫

0

 , (A10)

where R0 = R(0).

Figure A3 shows the measured water levels and a third-degree polynomial approximation for L(x) over period 1. Note that H(x) = x + 60 – L(x). Figure A4 shows

the resulting solution for α = 2π/3 and R0 = 15 cm (the radius of the hot-water drill)

plotted as R(L). This curve represents the predicted shape of the well cavity formed

Figure A3. Period 1 (prefire) water level vs. depth and third-degree

polynomial curve fitted to data.

100

0

90

80

70

60

50

10 20 40 50 30

Water Level (m)

X = D–60 (m)

28
during period 1. There are two main problems with these results. First, the predicted radius at the level of the freeze-back ice cover, R(82.6 m) = 16 m, is substantially larger than that estimated from down-hole video images (8 ±2 m). Second,

the observed cavity appeared to flare out at its upper end and become more vertical toward its bottom; that is, it appeared to be bell-shaped. The predicted shape

actually has the opposite trend: it is narrow (with near vertical walls) at its upper

end, and it flares out towards the bottom.

The most likely cause for the poor prediction by eq A10 is that it does not account for water percolation out of the well (dQ ≠ 0 in eq A7). Based on other

Rodriguez wells, Lunardini and Rand (1995) assumed that percolation would cease

at an ice specific gravity greater than 0.72, corresponding to depths below 74 m.

This generally agrees with Williams (1974), who expected that percolation from the

first South Pole Rodriguez well would cease at about 76 m. Modeling the percolation from the well is beyond the present scope of work and would introduce its

own uncertainties. A more satisfactory approach would be to measure the cavity

radius as a function of depth using a device lowered into the well.

Period 2 covers the two-month period after restarting the well on 12/2/94 but

before consumption began on 1/30/95. The well had frozen back about 11 m during the nine-month shut down after the fire. Although percolation would not be

significant during period 2, new ice had not been melted before the start of consumption. That is, there is no need to analyze period 2 to determine the volume of

ice melted that released micrometeorites into the well.

Period 3

During the period of water consumption, the water level was below 85 m, and

we would expect percolation to be zero. Thus, eq A7 may be used to relate changes

in well dimensions to the rate of water consumed. Figure A5 shows the polynomial

curves fitted to L, H, and Q data for period 3 (with x = D – 100.5). Note that dH/dx

Figure A4. Predicted period 1 cavity shape, from eq A10.

40

0

50

60

70

80

90

10 20 40 50 30

Water Level (m)

Radius, R(L) (m)

Ellipsoidal Pool Shape

R(0) = 0.15 m

29
2000

400

0

100

80

60

40

20

0

1600

1200

800

01 2345 6 7

X = D–100.5

Dimensions (m)

Total Consumption (m3)

Q (m3) 

Pool Depth (m)

Water Level (m)

over the period is less than 0.1, so we may treat H as a constant for the period, H =

15.5 m. In addition, solution of eq A7 requires an integration constant. If we assume that changes in well radius become small near the end of the period (i.e., the

well dimensions stabilize) we may solve eq A7 with dR/dx = 0 to obtain an integration constant, R(6 m) = 11.9 m.

Figure A6 shows the resulting prediction for the R(L) obtained by solving eq A7

Figure A5. Period 3 (consumption) dimensions and water consumption, and

polynomial curves fitted to data.

Figure A6. Predicted period 3 cavity shape, from eq A7.

7

85

86

87

88

89

90

91

8 9 10 11 12 13

Water Level (m)

Radius (m)

30
for both ellipsoid and paraboloid pool shapes and averaging the results (radii differences due to pool shape are less than about 30 cm). Note that the predicted radius of 11.1 m at L = 86.3 m agrees with the results of the draw-down tests conducted in March/April 1995, R = 13.1 ±2.4 m.

Composite well shape

We may use the foregoing analyses to compose our best estimate of the well

shape at the end of our collector deployments in December 1995. For the period of

water consumption, eq A7 provides a reasonable estimate for the cavity shape. In

addition, shape data from previous Rodriguez wells and our own video records

from the SPWW indicate that an ellipsoidal pool shape is reasonable for the belowwater portion of the well. Unfortunately, by not accounting for percolation, eq A7

yields an unrealistic shape for the prefire well cavity. Therefore, for period 1 (and

the short period 2) we will estimate cavity shape by using an approximation adopted

by Lunardini and Rand (1995): the ratio of pool radius/depth is approximately

constant. This ratio for period 3 ranges from 0.69 to 0.77 and averages 0.74. We used

Prefire Pool

Pool After Collector

Deployments

Best Estimate Radius

Water Level (m)

Estimated Radius (m)

50

60

70

80

90

100

110

120

130

0 5 10 15 20 25 30 35 40

Minimum Radius

Figure A7. Composite well shape, showing two possible

prefire cavity shapes.

31
its value at the start of consumption, R/H = 0.70, to ensure that the well shape is

continuous at the transition from period 2 to period 3.

Figure A7 shows the resulting composite well shape. Use of R/H = 0.70 for period 1 yields a bell-shaped cavity that is qualitatively consistent with the observed

shape. It predicts a radius of 10 m at the level of the freeze-back ice cover, consistent

with the observed value of 8 ±2 m. However, R/H = 0.70 probably overpredicts the

cavity size near its upper level. Thus, Figure A7 shows a conical wall shape that

should underpredict the prefire cavity size. Figure A7 also shows ellipsoidal pools

as they would have existed immediately before the 1994 fire and just following our

1995 collector deployments.

Ice volume and mass melted

We may use Figure A7 to estimate the volume and mass of ice melted that contributed micrometeorites to the well. The prefire cavity volume ranges between

3,300 m3 and 4,400 m3 for the conical and R/H = 0.70 shapes, respectively. Using

the average value and applying a 20% uncertainty, we estimate the prefire ice volume melted as 3,900 ±800 m3. The period 3 analysis yields a cavity volume of 2,200

m3 with an ellipsoidal pool of 4,700 m3. Assuming ±10% uncertainty, the period 3

ice volume melted is 6,900 ±700 m3. Combining these values yields a total volume

of ice melted as 11,000 ±1,000 m3. Accounting for the variation of density with depth,

we estimate the total ice mass melted as 8,100 ±900 tonnes.

32
APPENDIX B: SUMMARY OF COLLECTOR DEVELOPMENT TESTS.

Collector Mat’l Mat’l

test added recovered Percent Type of

Date facility (g) (g) recovered material Remarks

14 May 1 ft 100 71.07 71.07 Mixture A Fines from aolian

sample were not

recovered, they did

not plug the filter.

16 May 1 ft 200 165.6 82.80 Ss 297–420 μm Particles were

flushed out of

collector by water

draining through slot.

24 May 1 ft 200 191.6 95.80 Ss 200–400 μm Tried polyethylene check valve

30 May 1 ft 100 78.81 78.81 Ss 200–400 μm Check valve not

Bg 75–150 μm tight

29 Jun 4-ft 390.1 387 99.21 Ss 200–400 μm Rough ice,

tank Bg 75–150 μm multiple passes

30 Jun 4-ft 100.1 99.54 99.44 Ss 200–400 μm Smooth ice 50 g,

tank Bg 75–150 μm rough ice 50 g

6 Jul 4-ft 100 99.46 99.46 Ss 200–400 μm Smooth ice 50 g,

tank Bg 75–150 μm rough ice 50 g

10 Jul 4-ft 231.51 206.38 89.15 Mixture B Rough ice surface

tank

23 Aug 4-ft basin Ss 200–400 μm Could see sweep line

Bg 75–150 μm of collector

6 Sep 4-ft tank Outer flap picked up

particles extremely

well.

24 Aug 8-ft basin Needs weight

in center

28 Aug 8-ft basin Bg >400 μm

Ss = Silica sand.

Bg = Black glass.

Mixture A: 50 g Antarctic aeolian dust, 49 g silica sand 297–420 μm, 1 g metal, and glass

spheres 50–400 μm size.

Mixture B: 68 g silica sand 200–400 μm, 20 g black glass 150–425 μm, 8 g stainless steel

spheres 60–125 μm, and 4 g black glass 75–150 μm.

33
4

APPENDIX C: SUMMARY OF COLLECTOR DEPLOYMENTS IN SPWW.

Deployment no./

Date area collected Configuration

14 Dec 1 Single weights on short shaft

 Pocket 1 Small hubs on outside of weights

Small hanging hoop

15 Dec 2 Single weights on short shafts

Pocket Large hub, 6.25 ≤O.D. on

1 & 2 inside of weight on

lower end, outside on

upper end

Small hanging hoop

18 Dec 3 Double weights on both shafts

Plateau Small hubs outside, large inside

only Small hanging hoop

22 Dec 4 Double weight on long (lower)

shaft

Large hanging hoop

Sting motors failed

23 Dec 5 Double weight on long (lower)

Pocket 5 shaft

Large hanging hoop

Sting

25 Dec 6 Double weight on long (lower)

Pocket 6 shaft

Large hanging hoop

Sting

2

3

3

4

5

6

1

34
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May 1997

Collecting Micrometeorites from the South Pole Water Well

Susan Taylor, James H. Lever, Ralph P. Harvey, and John Govoni

U.S. Army Cold Regions Research and Engineering Laboratory

72 Lyme Road

Hanover, New Hampshire 03755-1290

CRREL Report 97-1

Approved for public release; distribution is unlimited.

Available from NTIS, Springfield, Virginia 22161

A collector was designed and built to retrieve micrometeorites from the floor of the South Pole Water Well. The

large volume of firn and ice being melted for the well and the low component of terrestrial material in Antarctic ice

make the South Pole Water Well an ideal place to collect micrometeorites. Because the age of the ice being melted is

known, yearly or periodic collections provide large numbers of micrometeorites of known terrestrial age. The

collector was designed to pose no threat to the well’s water quality, to be reliable and easy to operate, and to collect

particles larger than 50 μm. This report details how this collector was built and tested and documents the rationale

behind some of the design choices. It also includes preliminary findings from the first deployment.

National Science Foundation

Arlington, Virginia 22230

42

UNCLASSIFIED UNCLASSIFIED UNCLASSIFIED UL

Antarctica Micrometeorites Water well

Cosmic dust South Pole