Containing the secrets?

Millimeter- to centimeter-sized inclusions found in chondrite meteorites represent the oldest solids from our solar system and the building blocks for the planets. A new study led by researchers at the Centre for Star and Planet Formation applied new analytical methods to these inclusions to establish a revised chronology for the first 3 million years of the early solar system that is shorter in duration from existing estimates by up to 2 million years. Given that this revised chronology is similar to the time scales of formation of other planetary systems as observed by astronomers, the study concludes that these first solids are formed by processes common to planetary disks throughout the galaxy. In turn, this predicts the widespread occurrence of Earth-like planets. The results and conclusions of the new study are published in the journal Science.

Cosmic sediments hold keys to our solar system’s formation: Chondrite meteorites contain inclusions – so-called calcium-aluminum-rich inclusions (CAIs) and chondrules – that formed as free-floating objects within the protoplanetary disk during the formative stages of our solar system. As such, they offer the only available direct information about the conditions, timing and tempo of the processes related to the critical early stages our solar system’s formation and whether it is the product of ordinary or unique circumstances. CAIs formed as fine-grained condensates from a gas in high-temperature environments whereas chondrules mainly represent dust aggregates that were flash heated in lower temperature environments.

A revised chronology: Using new and refined analytical methods based on the radioactive decay of uranium to lead, we have determined the most precise, assumption-free absolute age for CAIs, and therefore the solar system, of 4567.30±0.16 My. Using the same method, we find that chondrules formed contemporaneously with CAIs and continue to form for only another 3 million years. This revised timescale is more consistent with the timing inferred by astronomers observing other protoplanetary disks. As such, we infer that the high temperature events recorded by CAIs and chondrules in our solar system relate to generic events intrinsic to the natural evolution of any protoplanetary disk, most likely shock waves related to bursts of material being episodically accreted from the envelope to the protoplanetary disk. Given the generic nature of this process, the paper concludes that our solar system was formed by ordinary and predictable circumstances, which, in turn, predicts the widespread occurrence of Earth-like planets in the Universe.



For more information:

Associate Professor James N. Connelly 28 51 99 62,
Professor Martin Bizzarro 28 51 99 82,