A team of scientists has discovered molecules essential for life in material from certain kinds of asteroids and comets that have fallen to Earth.
In January 2000, a large meteoroid exploded in the atmosphere over northern British Columbia, Canada, and rained fragments across the frozen surface of Tagish Lake. Because many people witnessed the fireball, pieces were collected within days and kept preserved in their frozen state. This ensured that there was very little contamination from terrestrial life.
"The Tagish Lake meteorite fell on a frozen lake in the middle of winter and was collected in a way to make it the best preserved meteorite in the world," Dr. Christopher Herd of the University of Alberta, Edmonton, Canada, lead author of a paper about the analysis of the meteorite fragments, said.
Dr. Michael Callahan of NASA’s Goddard Space Flight Center in Greenbelt, Md., a co-author on the paper, added: "The first Tagish Lake samples, the ones we used in our study that were collected within days of the fall, are the closest we have to an asteroid sample return mission in terms of cleanliness."
The Tagish Lake meteorites are rich in carbon, and like other meteorites of this type, the team discovered the fragments contained an assortment of organic matter including amino acids, which are the building blocks of proteins.Proteins are used by life to build structures like hair and nails, and to speed up or regulate chemical reactions. What’s new is that the team found different pieces had greatly differing amounts of amino acids.
"We see that some pieces have 10 to 100 times the amount of specific amino acids than other pieces," Dr. Daniel Glavin of NASA Goddard, also a co-author on the Science paper said."We’ve never seen this kind of variability from a single parent asteroid before.Only one other meteorite fall, called Almahata Sitta, matches Tagish Lake in terms of diversity, but it came from an asteroid that appears to be a mash-up of many different asteroids," he explained.
The findings have been published June 10 in the Journal Science.