March 16, 2000
A meteorite that exploded over a remote area of northwest Canada in January may offer “a new window into the universe before the solar system was created,” said a NASA scientist who has begun analyzing some of the meteorite fragments.
The very primitive composition and pristine condition of the 4.5-billion-year-old meteorite “offers us a snapshot of the original composition of the entire solar system before the planets formed,” said Dr. Michael Zolensky, a cosmic mineralogist at NASA’s Johnson Space Center (JSC) in Houston. “It tells us what the initial materials were like that went into making up the Earth, the Moon and the Sun.” The age of the solar system is about 4.5 billion years.
“These meteorite fragments are of immense scientific value and interest,” said Dr. Richard Herd, Curator of National Collections for the Geological Survey of Canada. “This rare find potentially will contribute to a better understanding of the nature of the universe.” He added that finding previously undetected compounds in the fragments will have implications for both planetary and biological sciences worldwide.
The scientists described the fragments -- lumps of crumbly rock with scorched, pitted surfaces -- as resembling partly used charcoal briquettes: black, porous, fairly light and still smelling of sulfur.
Several factors combined to make this meteorite a cosmic bonanza for scientists. First, it is a carbonaceous chondrite, a rare type of meteorite that contains many forms of carbon and organics, basic building blocks of life. Carbonaceous chondrites, which comprise only about 2 percent of meteorites known to have fallen to Earth, are typically difficult to recover because they easily break down during entry into Earth's atmosphere and during weathering on the ground.
Zolensky said the last time a carbonaceous chondrite like this fell to Earth and was recovered was 31 years ago. “This is probably the only time in my career this will happen,” he said.
The location and timing of the fireball also contributed to the scientific value of the samples. The fragments are part of a meteor that blew apart in a fireball over a remote area of the Yukon Territory the morning of Jan. 18, 2000. The resulting sonic booms startled residents as far away as British Columbia and Alaska. The frozen, snow-covered ground of the remote Yukon provided near-ideal conditions for preservation, Herd said.
The finder, a local resident who has requested anonymity, collected the fragments in clean plastic bags and kept them continuously frozen. These are the only freshly fallen meteorite fragments recovered and transferred to a laboratory without thawing. Keeping the fragments continuously frozen minimized the potential loss of organics and other volatile compounds in the fragments.
About 2 pounds of meteorite fragments have been recovered so far. Of those, Zolensky has about a pound of fragments provided by the Canadian government and the University of Calgary. The finder loaned them to the university and to the National Meteorite Collection of the Geological Survey of Canada, Natural Resources Canada (NRCan) in Ottawa, which provided the still-frozen samples to JSC for study and analysis. NASA is working closely with NRCan scientists and is providing results of the analysis to them. “We are very sensitive to the fact that these are Canadian meteorites,” Zolensky said. Any future studies will be done in cooperation with scientists worldwide.
Scientific analysis of the fragments has just begun. Tests have been limited to two non-destructive examinations: making a thin section to analyze the mineralogy of the fragments, and measuring induced radioactivity. Tests for induced radioactivity, which are being carried out by Dr. David Lindstrom of JSC, measure the object’s exposure to space radiation. This can be used to determine the size of the original meteoroid in space, estimates of which range up to 50 feet in diameter, with a mass of more than 55 tons.
The next step in the study of the fragments will be baseline analyses of the organics in the meteorite. This would require the destruction of some samples, and negotiations are under way with the finder for permission to do such tests.
“The nice thing about having a sample like this is, you don’t really know what you’re going to find or where it’s going to lead,” Zolensky said. “You can tuck samples away for the future when new questions come along that people can’t even think up now.”
|| Samples of three carbonaceous chondrite meteorites that fell to
Earth. Carbonaceous chondrites contain many of the building blocks
of life. Left: Allende meteorite fell on Mexico in 1969. Center:
Sample of Yukon meteor that exploded over Yukon Territory, Canada,
on Jan. 18, 2000. Right: Murchison meteorite sample, which fell
to Earth in Australia in 1969. Samples of the Yukon meteorite are
being analyzed at NASA's Johnson Space Center at the request of
the Geological Survey of Canada, Natural Resources Canada, which
has borrowed them from the finder.
|| Fragment of the Yukon meteor that exploded over the Yukon Territory
in northwestern Canada in January 2000. The fragment is sealed in
a nitrogen-filled bag to protect it from contamination. Samples
of the meteorite are being analyzed at NASA's Johnson Space Center
at the request of the Geological Survey of Canada, Natural Resources
Canada, which is borrowing them from the finder.
|| Dr. Michael Zolensky, a NASA cosmic mineralogist, with a fragment
of the Yukon meteorite. The meteor exploded over the Yukon Territory
on Jan. 18, 2000, and a local resident collected several fragments
for analysis. Samples of the meteorite are being analyzed at NASA's
Johnson Space Center at the request of the Geological Survey of
Canada, Natural Resources Canada, which is borrowing them from the