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Comparison between hot and cold deserts



Introduction

"From a report presented by Shima and Shima to The Meteoritical Society in 1973. Their analyses showed that nine meteorites collected in 1969 by Japanese glacial geologists from a small (9 x 5 km) area of the Yamato Mts. icefields were not shower fragments but samples of four different stony meteorites. This unprecedented discovery gave rise to the concept that, under special circumstances, meteorites from diverse falls may be frozen into the ice and exposed on stranding surfaces-expanses of ice temporarily trapped behind mountain barriers and worn down by wind ablation.

1973 marks the beginning of Antarctic expeditions for meteorites recovery

"By 1994, twenty-one years after the Shimas surprised meteoriticists with their report, more than 15,000 meteorite fragments, possibly representing about 1,500 individual meteorites, have been collected from the cold Antarctic deserts by parties from Japan, the U.S.A., and Europe.
Marvin U. B.
(A Historical Outline of Meteorite Discoveries in Australia and Antarctica, 1994)



Today we can estimate at 2,000 the number of individual meteorites collected in Antarctica for twenty-seven years, an average of 74 meteorites per year.




Finds comparison

For a one year period : Met. Bull. N°84

Antarctica

On the last Meteoritical Bulletins N°84 & 85 :
62% of the finds are LL5
710 LL5 fragments recovered,
710 new numbers.
(probably paired)

Sahara

During our October 1999 expedition :
more than 2000 CO3 fragments
were recovered,
only one meteorite numbered

- Dar al Gani 749 -

All the recovered fragments are individually numbered.

All the fragments are gathered
under that same number

74 kg
listed for Antarctica continent

167 kg
listed for Dar al Gani area,
only 80 x 50 km (50 x 30 mi)
not including the 150 kg CO3 recovered







"Fragmentation due to weathering and abrasion processes such as frost wedging, salt production, wind abrasion, chemical exsolution, and biological actions also contribute to the number of specimens ultimately found on a stranding surface. The vast majority of meteorites from Antarctica exhibit significant weathering features, even those found still enclosed in ice, due to exposure to saltating snow and ice particles, long duration freeze-thaw cycles, and evaporite formation."
Harvey R. P.
(Moving Targets: The Effect of Supply, Wind Movement and Search Losses on Antarctic Meteorite Size Distributions, 1994)


"While the masses of most meteorites from Antarctica, Roosevelt County, and the Nullarbor Plain are on order of 10-100 g, meteorites found in the Sahara are generally larger. Most meteorites are weighing between 100 and 1000 g."
(Geiger T., Bischoff A., 1994)



Right image :
New meteorite from Dar al Gani,
waiting classification
white veins are metal, gemlike yellow
inclusions, grey-black matrix
without chondrules.
(SaharaMet expedition 2000)
- Full image -



Dar Al Gani

From 1995, date of the first systematic prospecting on Dar Al Gani by anonymous finder teams, more than 1000 individual meteorites have been recovered on this small Libyan plateau, including 4 Mars rocks, two lunar meteorites, and numerous other rare ones (some varieties totally unknown before).






The plateau of Dar Al Gani (120 km x 60 km) with 1000 meteorites collected to date (including sometimes more than 2000 fragments as for DaG 749) and its significant potential of small meteorites, sizes lower than 100 g, has a potential which can be directly compared with the whole Antarctica continent, also bringing access to other information, such as the ellipses of falls.

Viewing the immense surface area of the Sahara, other spots exist, isolated or on vast zones like Hammada Al Hamra, which confer to the whole Sahara a primordial position with regards to the search for meteorites in the coming years.



Left image :
 New meteorite from Dar al Gani,
heavily schocked achondrite showing numerous fragments.
(SaharaMet expedition 2000)
- Full image -

Left image :
New meteorite from
Dar al Gani,
waiting classification
many gemlike minerals.
(SaharaMet expedition 2000)



Conscious of the interest that represent the hot deserts, the scientific community very early invested itself in such a potential. Regularly expeditions were planed :
  • - Namibia expedition, 1991, three ordinary chondrites
  • - EUROMET Mongolian Expedition to the Gobi Desert, 1993 (0 meteorite)
  • - EUROMET Oman/Saudi Arabia Expedition, 1993 (2 chondrites recovered)
  • - Namibia expedition, 1999, "13 golf size meteorite, best British expedition of the last 20 years
This shows clearly the difficulty for people who were accustomed to collect fragments of meteorites in Antarctica (real black points on white ice) for having the eyes and the feeling to do the same recoveries between the several dark artefacts in desert strewnfields.
  • - SaharaMet, 1998, 2 people, 1 month, 80 kg recovered, 50 meteorites
  • - SaharaMet, 1999, 2 people, 1 month, 265 kg recovered, 87 meteorites
  • - SaharaMet, 2000, 55 kg recovered, 92 meteorites
  • - ...




Cost

Antarctica

Sahara

Half of the meteorite recoveries in Antarctica have been done by ANSMET (Antarctic Search for Meteorite program), funded by the Office of Polar Programs of the National Science Foundation (previsional budget for 2001: $285 million). This activity, made possible through the infrastructure provided by the Foundation's U.S. Antarctic Program, has taken place since 1976, through investments of over $2 million in research project support.

"The annual hunt for Antarctic meteorites is like a bargain-priced space mission that lets scientists explore extraterrestrial worlds without leaving their home planet."
Dr. Neal Lane, Director
NATIONAL SCIENCE FOUNDATION
(On the Announcement Regarding Possible Early Life on Mars, 1996)

No funds




SYDNEY, Australia (AP) -- "An American C-130 Hercules plane landed in a crevasse in Marie Byrd Land, Antarctica, this week, causing unspecified damage to the $25 million plane.
Simon Stephenson of the U.S. National Science Foundation, speaking from Antarctica's McMurdo Base, said today that the Hercules had completed a reconnaissance flight of the ice before attempting to land.
While it was taxiing, one of its skis dropped into a crevasse, which are often covered by thin layers of snow.

October 2000 Expedition, a bronze ring in the gear box suddenly broke on Roland Range Rover. Impossible to continue the trip. After a night of reflection, half a day of work, a new ring fabricated in the nearest local workshop... and $15 expenses, the trip restarts.




The Science

Antarctica

Sahara
"Interest in Antarctic meteorites continues to be high and nothing is foreseen that would abate the world's desire for more meteorites. As of March 1994, over 55 men and women from 45 different institutions in 16 nations have participated as ANSMET field party members.
Harvey R. P.
(Current Research Activities of ANSMET, 1994)
Today, hundreds of documented meteorites with strewnfield data remain to be classified, including achondrites.
But UCLA, Northern Arizona University, French scientists and many laboratories support and are working on NWA plundered meteorites. It seems that such meteorites with field data lost are the wish of the scientific community.
Strange behaviour!


October 2000 finds, waiting a laboratory
(only six are classified today)




Future

Antarctica

Sahara
Potential of the Antarctic, because of the ablation process of the ices, need many years to be renewed.

"We live in a golden age of science, which we hope will continue to unlock the secrets of the unknown for the benefit of all humankind".
Dr. Neal Lane, Director
NATIONAL SCIENCE FOUNDATION
Saharan strewnfields are the result of thousands of years of meteorite falls and particular geological features.

Few competent teams are going further and further in the real desert, taking care of the heritage represented by meteorites. This work will allow to provide future generations with accurate data.

We don't want to see the whole Sahara coming down to a NWA area with data lost and money to smuggling rings.



  • New Saharan achondrites remain unclassified, while in Antarctica small LL5 fragments (0.1 gr) are individually analyzed.
  • The average cost for an Antarctica meteorite is higher than $20,000.
  • If scientists and institutions become aware of Sahara potential, if they stop to favour the erasing of strewnfield data and to help international contraband, if they start to support prospecting teams, Sahara desert will become in the coming years the most important place in the world for meteorites discoveries.



Names, meteorites from Sahara