News in Science

Study puts solar system theory in a spin

Birth of dirt The first solids to form in our solar system appeared at the same time, more than 4.5 billion years ago, according to a new study.

The new findings, by researchers led by Dr James Connelly from the University of Copenhagen, may change our understanding of how the first pieces of 'dirt' in our solar system first formed.

CAIs (calcium-aluminium-rich inclusions) and chondrules are the earliest solids to form in our solar system. Both are found as millimetre- to centimetre-sized grains in meteorites.

Scientists have traditionally used isotopic ratios of aluminium to magnesium to date these most ancient solids, concluding that CAIs were the first solids to condense out of the protoplanetary disk followed millions of years later by chondrules.

The new method developed by Connelly and colleagues uses two new techniques to measure uranium and lead isotopes.

Reporting in the journal Science, Connelly and colleagues dated samples from numerous meteorites, finding chondrules formed 4.567 billion years ago - far earlier than previously thought.

"These data refute the long-held view of an age gap between CAIs and chondrules and, instead, indicate that chondrule formation started contemporaneously with CAIs and lasted about three million years," the authors write.

Controversial finding

Connelly and colleagues say the new time scales are comparable with those observed in distant solar and protoplanetary disks, indicating the processes that formed chondrules and CAIs in our solar system are not unique.

Dr Katie Dyl of Curtin University in Western Australia, says the new techniques used by Connelly and colleagues have only recently been available.

"These are really hard measurements to make," says Dyl. "This new plasma technology allows you to do more and also offers far greater precision."

She says this has allowed them to say something new and different from what everyone else is saying.

"The idea that CAI's and chondrules formed at the same time, goes against one of the basic principles, namely that CAI's formed first before anything else by two to three million years," says Dyl.

"Their claim will cause a lot of discussion"

"If it holds up to scrutiny and other labs find the same thing, then that's a really interesting breakthrough," says Dyl.