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 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 activities: 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 that 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.”
