Smithsonian

Contributions

TO

Astrophysics

Volume 8

SMITHSONIAN

Smithsonian

Contributions to Astrophysics

Volume 8, Number 8

THE HENBURY METEORITE CRATERS

by Paul W. Hodge

SMITHSONIAN INSTITUTION

fFashington, D.C.

1965
PiibUcatioiis of the Astrophysical Observatory

This series, Smithsonian Contrihulinns to Astrophysics, was inaugurated

in 1956 to provide a proper communication for the results of research con- ducted at the Astrophysical Observatory of the Smithsonian Institution.

Its purpose is the "increase and diffusion of knowledge" in the field of astrophysics, with particular emphasis on problems of the sun. earth, and the

solar sy.stem. Its pages are open to a limited nunilirr of papers by other

investigators with whom we have common interests. Another series is Annals of the Astrophysical Observatory. Il was started

in 1900 by the Observatory's first director, Samuel P. Langley, and has been

published about every 10 years since that date. These quarto volumes, some

of which are still available, record the history of the Observatory's researches and activities. Many technical papers and volumes emanating from the Astrophysical

Observatory have appeared in the Smithsonian Miscellaneous Collections. Among these are Smithsonian Physical Tables, Smithsonian Meteorological

Tables, and World Weather Records. Additional information concerning these publications may be secured from

the Editorial and Pulilications Division, Smithsonian Institution, Wasiiington, D.C. Fred L. Whipple, Director, Astrophysical Observatory,

Smithsonian Institution. Cambridge, Mass.
The Henbury Meteorite Craters

Paul W. Hodge

Among tlie many terrestrial craters now- recognized as having been caused by meteoritic

inipai't, the remarkable group of craters near

the Henbury Homestead in central Australia is

of special interest. In size, shape, and degree

of erosion they illustrate almost all the features

of known meteorite craters. Because there is

so little published information on the Henbury

crat.ers, I attempted, while carrying out a study

of meteoritic delms in the soil around them, to obtain a series of useful photographs of the

craters and surrounding region. The publication of sonu> of these photographs in the present

form is desirable for three reasons. First, the

increased interest in the general subject of meteorite craters has captured a large new audience wiio may find these photographs useful;

second, the photographs may be used in connection with past pictures, such as the unpublished set made by Bedford in 1931, and future

photographs to establish the amount and rate of erosion in order to estimate the age of the

craters; third, the rapidly increasing number of

visitors to the craters makes it advisable that a permanent record of tlieir present condition be

made. Approximately 50 groups now visit the

location of the craters each year; most of these

are local people or tourists. The fast-growing

tourist industry in the area suggests that tour buses may soon bring much larger numbers of

visitors. Such a situation may result in the

accidental alteration of some of the features of

the craters.

Location

The Henbury meteorite craters are located in the heart of arid central Australia at latitude

1 Smithsonian Astrophysical Observatory; regularly at the Berkeley Astronomical Department, University of California.

24°:35' S and longitude 13:3°10' E. They lie just north of a low linear range of hdls. Their

geological environment has been described by

Alderman (1932). At present they are best

reached by driving 80 miles from the city of

Alice Springs toward Adelaide, turning left opposite the Henbury Station airstrip, and continuing on a crude track f(U- 6 miles. The immediate

area around the craters has recently been set aside as a government reserve.

History of scientific work

1031, May.—Acting on reports of local residents

that meteorites were to be found in tlie vicinity

of 3 to 5 craters near Henbury, A. R. Alderman

(1932) carried out the first scientiiic studj^ of the

Henbury meteorite craters. He discovered,

mapped, and described 13 craters, which ranged

in size from 9 to 200 meters. In addition to making rough measurements of the diameters,

depths, and all heights of the ciaters, Alderman

also combed the entire area for meteorites and

meteoritic fragments. He found apjH-o.ximatelj^

800 pieces of meteoritic material, whose weights

ranged from a few grams to 24 kilograms. He

bored one of the craters (no. 5) to a deptli of 8

feet and found no evidence for a large meteorite

there. 1931, June. —Following Dr. Alderman's expedition, R. Bedford of the Kysincutta Museum

organized a party consisting of himself, his brother W. Bedford, and B. Duggin, to explore

the craters. On their first visit Bedford's group

concentrated on finding meteoritic fragments on

the ground surrounding the craters. A total of

550 meteorites was collected; they ranged in weight from 3 grams to 77.5 kilograms, totaling

146 kilograms. The results of the expedition were never published, except as an addendum to Alderman's paper, wTitten by Spencer.

199
200 SMITHSONIAN CONTRIBUTIONS TO ASTROPHYSICS

1932. —In the following year the Bedfords

returned to the Henbury craters planning to search for large meteorites by digging in the

centers of the craters themselves. The}' exca- vated four of the craters (nos. 10, 11, and 13 of Dr. Alderman's list) and a nearby probable

crater not included in Alderman's study. In

crater no. 13 several pieces of nieteoritic iron,

totaling appro.ximately 80 kilograms, were

found at a depth of 2 meters below the floor. 1937.—Five years later, .1. M. Rayner (1939)

and his associates carried out a magnetic survey

of the Henbury craters. Magnetic traverses across 12 of the craters (all but no. 9 of Alderman's list) produced the definite result that no

large magnetic anomalies exist in the region

and therefore that no large meteoritic body can

be intact under the surface except at inipnibably great depths. Within the cratei's 1(1 small local anomalies were discovered, the most

conspicuous being in craters nos. 5, 12, and 13. The geophysical results strongly suggest that

these anomalies might be caused by small masses of meteoritic iron buried at shallow

depths in the crater area. The cause of the

anomaly in crater 5 was found to be an 18- kilogram meteorite. The causes of the anomalies in craters 12 and 13 apparently remain

there. Rayner found 16 other small anomalies,

half of them falling near the crater walls and the

other half falling at considerable distances from

the craters. These may indicate the existence

of pieces of meteoritic material buried at shallow depths.

1962.~The geologist C. H. Chao visited the

Henbiuy craters and looked for shatter cones and other indications of impact. The results have not yet been published.

1963.—Meteoriticists E. P. Henderson and

Brian Mason carried out a search for meteorites

at the Henbmy craters; their results have not

yet been published.

1963. —A very detailed geological map, as

well as a topographical study, of the main

craters (nos. 6,7, and 8) was constructed after a prolonged studj' of the craters by D. J. Milton.

The results are not yet published.

1963.—The author carried out a soil sm-vev

of the ground surrounding the craters in an attempt to establish the distribution of microscopic meteoritic material around the craters and to estimate the total mass of the original

meteorites. Results of this recent researcli

will be published later in these Contributions.

The craters Table 1 lists all craters that have been either

definitely or tentatively identified and gives

data regarding tliem. In addition to the 13 craters described by Alderman there is a f(uuteenth, excavated by Bedford and not

described in previous literature, and a fifteenth

iiliject, tentatively identified, as a result of my

inspection on the ground and from the air, as a new small crater. I ha\c measured the

diametei's of all craters by means of aerial photographs. The heights of the rims given

in the table are those estimated oil her by

Alderman (1932) or bv mvself.

T.ABLE 1. -Diincn.'siuH.s of the craters

Ilenhunj meteorite

Crater
HEXBURY METEORITE CRATERS 201

Acknowledgments

I am indebted to A. R. Hogg, .1. M. Kayiier, and

T. Quinlan for generously making arrangements

and providing for my visit to the craters. I am

especially grateful to geologist Donald Woolley

who took me to the craters and helped me

considerabl3' in the work there.

References

.\lderman, a. R.

1932. The Meteorite Craters at Heiibury, Central

Australia. Mineralogical Magazine, vol. 23, pp. 19-32. Ravner, J. ISI. 1939. Examination of the Henbury Meteorite Craters by the Methods of Applied Geophysics.

Report of the Australian and New Zealand

Assn. for the Advancement of Science, vol. 24, pp. 72-78.

Abstract

Renewed interest in the Henbury Meteorite Craters has instigated several recent scientific studies of these unique

objects. This paper summarizes the published and luipublished research that has lieen carried out so far and presents

a table of dimensions newly derived, primarily from aerial photographs. .\ probable new crater is described, and a new map of crater outlines and locations is given. Sixteen photographs record the present condition of the crater system and form a photographic atlas of the craters and their surroundings.
202 SMITHSONIAN CONTRIBUTIONS TO ASTROPHYSICS

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Figure 1.—Outline map of the Henbury meteorite craters, derived from aerial photographs. The tops of the rims and

the outer perimeters of the floors are both indicated. Crater numbers are those assigned by .\lderman (1932), except

for crater IS, which was found after Alderman's study. Dotted lines indicate the area over which roclc debris from

the explosions can be traced on aerial photographs. Dashed lines trace the location of the rays emanating from crater .3 (see Rayner, 19.>9).
HENBURY METEORITE CRATERS 203

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Figure 2.-Henburv craters as showir on the aerial photographs of the Division of National Mapping,

Canberra, Australia (reproduced through the courtesy of the Division).
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Figure 3

Figure 4

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Figure 5

FiGL-RE 3. —Aerial photograph taken from a ligJit plane from approximately 1000 feet above the Henbury

craters, showing craters 6, 7, 8, and 9 from the south.

Figure 4. —Aerial photograph, taken as above, showing (from left to right) craters 1, 2, .i, 4, 5, 7. and 11 from the southwest.

Figure 5. —Aerial photograph, taken as above, showing craters 10, 11, 12, and 15.

205

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Figure 6

Figure 7
Figure 6. —The three main craters as seen from the ridge to the south. The inconspicuous rim of the

largest crater (no. 7) extends from the left edge of the photograph almost to its right edge. Crater 6, the water crater, is conspicuous because of the large number of trees growing within it. Crater 8 is

to its right.

Figure 7. —Interior of the largest crater (no. 7), looking north from its southeast rim. The gentle slope

of its walls shows considerable erosion. The walls rise approximately 50 feet above the floor.

Figure 8. —Floor of crater 6, the water crater, consisting at the time of the photograph of a flat, drj- mud area serrated by cattle footprints. This photograph looks east from the floor toward the common

rim of craters 6 and 8.

207

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Figure

Figure 9. —Inconspicuousness of the craters is illustrated in this photograph of craters 3 and 5, taken from the northeast, near the main crater. Crater 3 is visible only because of the trees extending

out of it.

Figure 10. —Interior and south walls i)f crater .\ taken from its north rim, showing that although the

wall is quite high, the rim does not e.xtend conspicuously above the surrounding area.

Figure II. —Crater .' from its east rim, demonstrating the considerable erosion of the south wall.

209
Figure 12

Figure 1 3
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Figure 12. —Floor of crater 4 from its north rim. The scale of the photograph can be gauged from the

figure standing near the base of the south wall.

Figure l.i.—Crater 4 from its floor near the south wall, lookine toward the west i

Figure 14. —Crater 5 from its almost imperceptible east rim. Erosion has so reduced this rim that this crater is now one of the more inconspicuous; it is noticeable primarily because of the fine sediments

covering its floor and because of its trees.

211
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Figure 15
Fiuute i;

Figure 15.—Crater 10 photographed from the north. Bedford excavated this small crater in 19.i2.

Figure 16.—Crater 11 from the east. This inconspicuous crater, witli no walls, was also excavated by

Bedford.

Figure 17. —Crater 12 from the west. Because this crater is on the side of a moderately steep slope,

its walls vary from almost no height at the south (right) to 4 meters on the north side (left).

213