Glacial Meteorite Searches

1. Glacial Meteorite Searches Rhett Deobald March 3, 2006

2. Meteorites A meteorite is a small extraterrestrial body that impacts the Earth�s surface. Meteorites represent samples from planetary objects, such as asteroids There are four principal types of meteorites: 1. Chrondrites � contain chrondrules 85% of all meteorites found on the surface of the Earth are chrondrites A meteorite is a small extraterrestrial body that impacts the Earth�s surface (Norton, 1998) While still in space it is know as a meteoroid, and a meteor is the phenomena seen when it burns up as it enters the atmosphere. Meteorites represent samples from planetary objects, such as asteroids However in the last 25 years Lunar and Martian meteorites have been found Meteorites range in size from microscopic to 60 tons (largest found on earth.) There are four principal types of meteorites: 1.����� Chrondrites � contain chrondrules (mm sized molten droplets from the solar nebula) 85% of all meteorites found on the surface of the Earth are chrondrites There are three basic groups of primitive chondrites representing these variations are the carbonaceous chondrites, enstatite chondrites, and unequilibrated ordinary chondrites. A meteorite is a small extraterrestrial body that impacts the Earth�s surface (Norton, 1998) While still in space it is know as a meteoroid, and a meteor is the phenomena seen when it burns up as it enters the atmosphere. Meteorites represent samples from planetary objects, such as asteroids However in the last 25 years Lunar and Martian meteorites have been found Meteorites range in size from microscopic to 60 tons (largest found on earth.) There are four principal types of meteorites: 1.����� Chrondrites � contain chrondrules (mm sized molten droplets from the solar nebula) 85% of all meteorites found on the surface of the Earth are chrondrites There are three basic groups of primitive chondrites representing these variations are the carbonaceous chondrites, enstatite chondrites, and unequilibrated ordinary chondrites.

3. 2. Achrondrites � crust of planets 3. Iron meteorites � cores of planets 4. Stony-iron meteorites � mantle of planets 2.����� Achrondrites � crust of planets 3.����� Iron Meteorties � cores of planets 4.����� Stony-iron meteorites � mantle of planets Data from the Meteor Observation and Recovery Project, a Canadian study, showed that approximately 24,000 meteorites land somewhere on earth every year. However, most meteorites that fall on the continents are usually lost because of high sedimentation or weathering rates. 2.����� Achrondrites � crust of planets 3.����� Iron Meteorties � cores of planets 4.����� Stony-iron meteorites � mantle of planets Data from the Meteor Observation and Recovery Project, a Canadian study, showed that approximately 24,000 meteorites land somewhere on earth every year. However, most meteorites that fall on the continents are usually lost because of high sedimentation or weathering rates.

4. Approximately 24,000 meteorites land somewhere on Earth every year. 70% are lost in the ocean 30% are distributed over the land Equals one meteorite per 10,000 square miles Terrestrial meteorites are usually never found due to high rates of weathering or sedimentation Data from the Meteor Observation and Recovery Project, a Canadian study, showed that approximately 24,000 meteorites land somewhere on earth every year. Of these, approximately 70% land in the ocean leaving 30% distributed over the land. This equates to one meteorite per 10,000 square miles per year. However, most meteorites that fall on the continents are usually lost because of high sedimentation or weathering rates.Data from the Meteor Observation and Recovery Project, a Canadian study, showed that approximately 24,000 meteorites land somewhere on earth every year. Of these, approximately 70% land in the ocean leaving 30% distributed over the land. This equates to one meteorite per 10,000 square miles per year. However, most meteorites that fall on the continents are usually lost because of high sedimentation or weathering rates.

5. Timeline of Antarctic Expeditions Previous to 1969 and the Japanese discovery of nine meteorites, only four other specimens had been found in Antarctica. The first Antarctic meteorite ever found was a 1 kg chrondrite, which was discovered during an Australian expedition in 1912. (Cassidy, 2003) Two more meteorites were found in 1961 by Russian and U.S. Geological mapping expeditions and another in 1964 by the USGS. Even though the third meteorite found was an extremely rare type (pallasite), it was not until the Japanese expedition of 1969 that scientists began realizing what an important place Antarctica was for collecting meteorites. That same year Japanese glaciologists discovered 9 meteorites in a 50 km2 area of ice around the Yamato Mountains of east Antarctica. o������ Out of these nine, four different types of meteorites were identified which can only be interpreted as four separate falls. Thus suggesting that meteorites are concentrated on the Antarctic ice. (Yoshida et al., 1971) Five years later, during December �74 and January �75, a Japanese field team recovered 663 meteorites at the Yamato Mountains. Convinced that Antarctica was good place to collect and study meteorites, NASA and the National Science Foundation (NSF), with the help of William Cassidy (a professor from the University of Pittsburgh), set up a project known as the Antarctic Search for Meteorites (ANSMET) Since �76 ANSMET has sent expeditions in search of meteorites, and have joined with Japan, China and a mix of European Countries to recover approximately 35,000 meteorites. Previous to 1969 and the Japanese discovery of nine meteorites, only four other specimens had been found in Antarctica. The first Antarctic meteorite ever found was a 1 kg chrondrite, which was discovered during an Australian expedition in 1912. (Cassidy, 2003) Two more meteorites were found in 1961 by Russian and U.S. Geological mapping expeditions and another in 1964 by the USGS. Even though the third meteorite found was an extremely rare type (pallasite), it was not until the Japanese expedition of 1969 that scientists began realizing what an important place Antarctica was for collecting meteorites. That same year Japanese glaciologists discovered 9 meteorites in a 50 km2 area of ice around the Yamato Mountains of east Antarctica. o������ Out of these nine, four different types of meteorites were identified which can only be interpreted as four separate falls. Thus suggesting that meteorites are concentrated on the Antarctic ice. (Yoshida et al., 1971) Five years later, during December �74 and January �75, a Japanese field team recovered 663 meteorites at the Yamato Mountains. Convinced that Antarctica was good place to collect and study meteorites, NASA and the National Science Foundation (NSF), with the help of William Cassidy (a professor from the University of Pittsburgh), set up a project known as the Antarctic Search for Meteorites (ANSMET) Since �76 ANSMET has sent expeditions in search of meteorites, and have joined with Japan, China and a mix of European Countries to recover approximately 35,000 meteorites.

6. Expeditions Teams of 6 � 8 people Field season is November to January Carry out systematic searches near stranding sites Sample is given an ID, collected in sterile bag and sent frozen to labs Expeditions to Antarctica occur between November and January, during the austral summer. A team of 6 to 8 people is assembled and set out for Christchurch, NZ where they gather supplies and receive training. They then catch a cargo plane and head for one of the three main stations - McMurdo, Palmer or Amundsen-Scott Station. The team travels to and from the study areas in small planes, helicopters or by snowmobile. Once at the area of interest they construct a self-sufficient, temporary camp from which they conduct their research. The team searches exposed blue ice in a series of parallel transects either on snowmobile or by foot with consideration given to spacing between team members. To minimize the risk of missing specimens, transects are arranged to ensure significant overlap while minimizing exposure to crosswinds. It is important to note that many meteorite stranding surfaces require several years to search due to their size. Once a sample is located, it is assigned an ID number, a position is taken by GPS, and a note is made about size, classification, and distinguishable features. The sample is then collected in a sterile teflon bag to avoid contamination such as oxidization. While the field season is in progress, these samples are carefully inventoried and kept frozen. Upon return to the station, the meteorites are transferred to special shipping containers and sent, still frozen, to the Antarctic Meteorite Curation Facility at the Johnson Space Center in Houston, Texas. Expeditions to Antarctica occur between November and January, during the austral summer. A team of 6 to 8 people is assembled and set out for Christchurch, NZ where they gather supplies and receive training. They then catch a cargo plane and head for one of the three main stations - McMurdo, Palmer or Amundsen-Scott Station. The team travels to and from the study areas in small planes, helicopters or by snowmobile. Once at the area of interest they construct a self-sufficient, temporary camp from which they conduct their research. The team searches exposed blue ice in a series of parallel transects either on snowmobile or by foot with consideration given to spacing between team members. To minimize the risk of missing specimens, transects are arranged to ensure significant overlap while minimizing exposure to crosswinds. It is important to note that many meteorite stranding surfaces require several years to search due to their size. Once a sample is located, it is assigned an ID number, a position is taken by GPS, and a note is made about size, classification, and distinguishable features. The sample is then collected in a sterile teflon bag to avoid contamination such as oxidization. While the field season is in progress, these samples are carefully inventoried and kept frozen. Upon return to the station, the meteorites are transferred to special shipping containers and sent, still frozen, to the Antarctic Meteorite Curation Facility at the Johnson Space Center in Houston, Texas.

7. Why Search Glaciers and Ice Caps? 1. Obstruction to ice flow 2. Exposed blue ice in an accumulation zone 3. Altitude 4. Persistence of conditions Obstruction to ice flow � the flow of the East Antarctic Ice sheet toward the sea is blocked by the Transantarctic Mountains, producing localized areas where inflow is minimized and outflow may cease altogether. Exposed blue ice in an accumulation zone - blue ice is present in the meteorite stranding areas because specific local loss mechanisms such as sublimation and wind scouring dominate over the supply of precipitation. Altitude � At high altitudes conditions are dry and cold, supporting high sublimation rates, limited existence of liquid water, and slow specimen sinking rates. Ice fields located high on the ice sheet are also directly exposed to strong katabatic winds that bring in cold, dry air from the center of the ice sheet, removing snow accumulations and further encouraging sublimation. Ablation rates have been as high as 10 centimeters per year Persistence of conditions � It is only when sustained sublimation, slow ice flow, and stable environmental conditions combine in a favorable way for long periods of time (thousands of years or more) does a concentration of meteorites build up. Obstruction to ice flow � the flow of the East Antarctic Ice sheet toward the sea is blocked by the Transantarctic Mountains, producing localized areas where inflow is minimized and outflow may cease altogether. Exposed blue ice in an accumulation zone - blue ice is present in the meteorite stranding areas because specific local loss mechanisms such as sublimation and wind scouring dominate over the supply of precipitation. Altitude � At high altitudes conditions are dry and cold, supporting high sublimation rates, limited existence of liquid water, and slow specimen sinking rates. Ice fields located high on the ice sheet are also directly exposed to strong katabatic winds that bring in cold, dry air from the center of the ice sheet, removing snow accumulations and further encouraging sublimation. Ablation rates have been as high as 10 centimeters per year Persistence of conditions � It is only when sustained sublimation, slow ice flow, and stable environmental conditions combine in a favorable way for long periods of time (thousands of years or more) does a concentration of meteorites build up.

8. Antarctic meteorite sites Areas that have produced significant amounts of meteorites have been in and around the Transantarctic Mountains. The first ANSMET expedition discovered what turned out to be a significant concentration of meteorites at the Allan Hills in southern Victoria Land. Later exploration in this region resulted in the discovery of significant meteorite concentrations on icefields to the west of the Allan Hills, at Reckling Moraine, and Elephant Moraine. Other notable concentrations have been found in the Beardmore region, Thiel Mountains-Patuxent Range region, the Darwin Glacier area and the Pecora Escarpment and the LaPaz Icefields. Areas that have produced significant amounts of meteorites have been in and around the Transantarctic Mountains. The first ANSMET expedition discovered what turned out to be a significant concentration of meteorites at the Allan Hills in southern Victoria Land. Later exploration in this region resulted in the discovery of significant meteorite concentrations on icefields to the west of the Allan Hills, at Reckling Moraine, and Elephant Moraine. Other notable concentrations have been found in the Beardmore region, Thiel Mountains-Patuxent Range region, the Darwin Glacier area and the Pecora Escarpment and the LaPaz Icefields.

9. Importance of Glacial Meteorites New and rare meteorites Better understanding of meteorite types Study the behavior of the Sun New information about the flow of the Antarctic ice sheet A more accurate age of Earth and the Universe Enhanced knowledge of the Moon and Mars Tremendous advances in the understanding of our solar system and planetary processes. Previous to the exploration of glacial meteorites, about 2000 different meteorites had been recovered over the entire land surface of earth. However with the discovery of the Antarctic meteorite deposits and the substantial increase in meteorite inventory, valuable scientific information has be gathered. ����� New and rare types of meteorites have been found. ����� The larger collection of meteorites allows a better understanding of the abundance of meteorite types in the solar system. ����� The old terrestrial age of some meteorites allows a look back into time to see what the abundances were millions of years ago and to study the behavior of the Sun, which implanted particles in these meteorites during their cosmic journey but not after they fell to Earth. ����� The cleanliness of the samples allows studies that previously were difficult or impossible with available samples. ����� New information may be obtained about the flow of ice in the Antarctic ice sheet. ����� A more accurate age of the Earth (4.56 billion years) and the Universe (14.93 billion years) has been calculated. Seven lunar meteorites have been found in Antarctica greatly enhancing our knowledge of the lunar surface. An important group of igneous meteorites have been speculated to have originated from Mars because they contain noble gases identical to the current atmosphere of Mars (measured from the Viking landers). In conclusion, the recovery of large numbers of Antarctic meteorites, which represent an unbiased, long term collection, has provided tremendous advances in the understanding of our solar system and planetary processes. � � Previous to the exploration of glacial meteorites, about 2000 different meteorites had been recovered over the entire land surface of earth. However with the discovery of the Antarctic meteorite deposits and the substantial increase in meteorite inventory, valuable scientific information has be gathered. ����� New and rare types of meteorites have been found. ����� The larger collection of meteorites allows a better understanding of the abundance of meteorite types in the solar system. ����� The old terrestrial age of some meteorites allows a look back into time to see what the abundances were millions of years ago and to study the behavior of the Sun, which implanted particles in these meteorites during their cosmic journey but not after they fell to Earth. ����� The cleanliness of the samples allows studies that previously were difficult or impossible with available samples. ����� New information may be obtained about the flow of ice in the Antarctic ice sheet. ����� A more accurate age of the Earth (4.56 billion years) and the Universe (14.93 billion years) has been calculated. Seven lunar meteorites have been found in Antarctica greatly enhancing our knowledge of the lunar surface. An important group of igneous meteorites have been speculated to have originated from Mars because they contain noble gases identical to the current atmosphere of Mars (measured from the Viking landers). In conclusion, the recovery of large numbers of Antarctic meteorites, which represent an unbiased, long term collection, has provided tremendous advances in the understanding of our solar system and planetary processes. � �

10. The End!