A meteorite worth its salt

The "Zag" meteorite fell to Earth in 1988

By BBC News Online science editor Dr David Whitehouse

Salt crystals found within the "Zag" meteorite may be among the oldest materials found in the Solar System according to British scientists.

The age of the salt crystals could force a reappraisal of the timescale for the origin of our Solar System.

Salt crystals from the birth of the planets

It is possible that hospitable conditions for life might have arisen earlier than previously thought. The researchers report their findings in journal Science.

Using radioisotope dating, scientists at the University of Manchester and the Natural History Museum in London, have determined that the salt crystals probably formed within about two million years of the solar system's birth.

If this is correct, it means that the dust, gas, and ice swirling around the new-born Sun clumped together into rocky fragments far more quickly than researchers had assumed.

These fragments were the parent bodies for meteorites like Zag and are believed to be the building blocks for asteroids and planets as well.

Radioactive decay

Dr James Whitby and colleagues suggest that Zag's parent body grew rapidly into a rocky mass containing water and radioactive elements. The elements decay produced enough heat to melt any ice within the rock and caused the liquid to evaporate altogether.

The salt crystals were formed during the evaporation process, similar to the way salt forms when sea water evaporates on Earth.

The Zag meteorite, which fell in Morocco in 1988, was the second meteorite found to contain salt crystals. Like those in the Monahans meteorite the crystals contained microscopic droplets of water, the key ingredient for life.

Accurate dating of salt crystals in the Monahans meteorite suggest that the crystals might be some of the oldest materials in the Solar System, but the dating method used is less precise than the one used by Whitby and his colleagues.

It is estimated that the salt crystals in the Zag meteorite formed about two million years after the birth of the Solar System some 4.57 billion years ago. It suggests that that liquid water was expelled its parent body soon after it had been formed.

Until the discovery of salt in Monahans and Zag, the oldest materials in the Solar System were thought to be chondrules, glassy spheres that make up much of the mass of primitive meteorites.