Southpaws, unite: The solar system is made more of leftie amino-acid molecules than rightie ones, according to a new study.
Amino acids, the building blocks that make up proteins, come in right- and left-handed forms like a pair of gloves. On Earth, there are more left-handed amino acids in nature than right-handed ones, even though amino acids made in the laboratory come in equal amounts of both types.
University of Oklahoma geochemist Michael Engel has studied the amino acids in a meteorite named Murchison, which fell in Australia in 1969. Fifteen years ago, Engel suggested that the Murchison rock contained an excess of left-handed amino acids. But many scientists thought those extra leftie molecules were simply Earthly contaminants.
Now, Engel and Stephen Macko of the University of Virginia in Charlottesville have re-examined the Murchison amino acids. By comparing forms of nitrogen in the meteorite, the researchers again found extra leftie amino acids -- over 30 to 50 percent more lefties than righties, in some cases.
Thus, the Murchison meteorite shows that the left-handed excess of amino acids may be spread throughout the solar system, the researchers wrote last week in Nature. So it may be more difficult to distinguish between life that originated on Earth and life that originated elsewhere in the solar system, added planetary scientist Christopher Chyba of the University of Arizona in Tucson.