'Rock of ages' offers clues to Earth's formation
(NC&T/UT) "They are bits of space that come to us," said Professor KimTait of geology at U of T and associate curator of mineralogy at the Royal Ontario Museum.
Although the atmosphere usually protects the Earth from all of this rubble flying around, when it doesn't, researchers like Tait rejoice because meteorites carry clues about the distant past. Approximately 30,000 meteorites have been found on Earth and the ROM houses about 2,300 fragments. It is the second largest collection in Canada.
U of T geology professor Gopalan Srinivasan, cross-appointed to astronomy and astrophysics, said meteorites preserve the records of the earliest stages of the formation of the solar system, which is about 4.6 billion years old.
"For the history of earliest stages, from its inception to first 50million years, we find clues to the formation and evolution of various solar system bodies preserved only in meteorites because evolved planets like Earth have recycled their crust," he said, adding that meteorites can also help explain the primary chemical composition of the whole Earth and formation of the Earth-moon system.
"Every meteorite has a story," said Tait. Under her tutelage, U of T master's student Katrina van Drongelen is writing the story of an "unknown meteorite" -- unknown in the sense that the 7.5 kilogram rock has not been studied or classified formally yet.
|The Tagish Lake meteorite. (Photo: U. Toronto)|
Van Drongelen said it is a dream come true to be able to work with the ROM's great collection and supportive people like Tait.
"Initially I wanted to study astronomy, but in university I took a geology course and fell in love with the science. I found out that I could study planetary materials from a geological perspective and was sold.
"When I do my PhD at U of T, I will study a different type of meteorite called a eucrite, which is very old and will be able to tell me about complex processes that occurred near the very beginning of the solar system. This is quite an exciting project."
Tait said the ROM collection is a veritable gold mine for students of geology. The collection of rare meteorites is part of the Teck Suite of Galleries: Earth's Treasures, which opened December 2008.
The collection's real significance lies not in its size, but its quality. According to available data, the ROM collection contains the highest percentage of the rarest types of meteorites. This includes a piece of Mars and a 1.1 kg lunar specimen, the biggest lunar meteorite on display worldwide.
Arguably, the jewel in the crown of the collection is the Tagish Lake meteorite, one of the museum's 15 iconic objects. Tait said it is special for a number of reasons, one of which is the way it was retrieved. "No other meteorite has ever been recovered this way before," she said.
Tagish Lake meteorite fragments were frozen solid in an ice sheet between Northern B.C. and the Yukon and recovered a mere week later by a local resident who used gloves and kept the rocks in a cooler. As a result it is the most pristine meteorite ever found.
Since it fell in winter onto a frozen surface, there is some possibility that it may still contain frozen liquid and gaseous components from outer space. This would be the first time that such gaseous samples were available for study.
The Tagish Lake meteorite is a member of one of the rarest classes of carbon-rich meteorites, which are rich in organic compounds. It contains minerals and carbon-based chemical compounds dating to the beginnings of the solar system -- some may be even pre-solar in origin. Srinivasan said the Tagish Lake sample is "a wonderful piece of meteorite to work with to understand the formation of organic molecules in cold outer reaches of the solar system."
"The Tagish Lake meteorite gives a lot of evidence about the early solar system," he said. "It definitely has some peculiar organic molecules that may give us clues about the organic molecular history of the evolution in the solar nebula and, in a very nebulous way, it may tell us about the evolution of life itself. But those connections are not yet obvious."
Srinivasan's cosmochemistry lab is currently analysing Nd (Neodymium) isotopes to determine the formation of early reservoirs on planetary bodies, which in turn will tell him about the formation of the Earth's crust. The cosmochemistry lab is identified as a node in the Canadian Lunar Research Network and is involved in radiometric and tracer isotope and trace element systematics of lunar materials. The research also provides clues about the Earth.
"A comparative study of particular Nd isotopes in various reservoirs of Earth, moon, Mars and the asteroid 4-Vesta can tell us about details of evolutionary time scales and the nature of growth of the first 'continent-like crustal material' on these planets," he explained.
Space may be a very dangerous place, but both Tait and Srininvasan would agree it has a lot to tell us about how it all began and meteorites hold some of the most important clues.
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