Scientists have discovered evidence of a rare element that may have been present during the formation of the solar system. They've found curium in a meteorite which may just end a 35-year-old debate on the possible presence of the element.
"Curium is an elusive element," said Francois Tissot, the study's lead author. "It is one of the heaviest-known elements, yet it does not occur naturally because all of its isotopes are radioactive and decay rapidly on a geological time scale."
With that said, the researchers found evidence of curium in an unusual ceramic inclusion that they called "Curious Marie," taken from a carbonaceous meteorite. Curium became incorporated into the inclusion when it condensed from the gaseous cloud that formed the sun early in the history of the solar system.
On Earth today, curium exists only when manufactured in laboratories, or as a byproduct of nuclear explosions. With that said, curium would have likely been present early in our solar system as a byproduct of massive star explosions that occurred before the solar system was born.
"The possible presence of curium in the early solar system has long been exciting to cosmochemists, because they can often use radioactive elements as chronometers to date the relative ages of meteorites and planets," said Nicolas Dauphas of the University of Chicago, co-author of the new study.
Finding hard evidence of curium, though, is another matter entirely. In this case, the researchers identified and targeted a special kind of meteoritic inclusion rich in calcium and aluminum. These CAIs (calcium, aluminum-rich inclusions) are known to have a low abundance of uranium and likely to have high curium abundance. One of these inclusions, Curious Marie, contained an extremely low amount of uranium.
"It is in this very sample that we were able to resolve an unprecedented excess of 235U," said Tissot. "All natural samples have a similar isotopic composition of uranium, but the uranium in Curious Marie has six percent more 235U, a finding that can only be explained by live 247Cm in the early solar system."
The findings reveal a bit more about the composition of our early solar system. Not only that, but they definitively show that curium was present.
