Purple salt from outer space. It may sound like a horror film, but it could actually hold the key to understanding how life formed on Earth, and whether it exists anywhere else in the Universe.
In 1998, two rocks zoomed through the Earth's atmosphere. One plopped down in Monahans, Texas, near some boys playing basketball. The other landed in Morocco, in a town called Zag.
Earth is no stranger to meteorites; the planet is pelted by meteorites every day. But upon review by scientists from NASA and other institutions, the Zag and Monahans meteorites turned out to have something special: water.
When cracked open, the meteorites exhibit a purple area, which turned out to be ordinary table salt, sodium chloride. Cosmic rays had turned the area purple. Upon closer inspection, scientists found droplets of salty water in the purple.
Water from another planet
It was the first time scientists had access to water that had not originated on Earth.
Water is the key ingredient to life, and impacts the development of planets. It composes our oceans and affects volcanic bursts. Finding water was a major victory for meteorite researchers. But just how old was the water?
Preliminary dating of the Zag meteorite showed that liquid water had formed within 100 million years after the formation of the solar system, around 4.5 billion years ago.
"You have at least the potential for the evolution of life."
But new dating suggests that the salt crystals and brine formed just two million years after the solar system's birth. The results are published in the June 9 issue of the journal Science.
The researchers, from the University of Manchester and the Natural History Museum in London, used a type of radioactive dating that gives more precise results than the technique previously used.
Life supporting conditions
The new dating raises the possibility that the conditions capable of supporting life existed in the solar system earlier than previously thought.
"There is this old idea," said Dr. James Whitby, one of the researchers at the University of Manchester, "that life on Earth may have been seeded from somewhere else. People suggested Mars or a comet. In this case, you've got at least some meteorite parent bodies that have liquid water on them, long before there would have been water on Earth. It gives you an alternative environment in which life could have evolved on Earth."
The technique involved studying the proportion of xenon and iodine isotopes extracted from a tiny piece the rock. Iodine-129 is a radioactive element that decays into xenon-129 in fixed time known by scientists. By studying the proportion of the isotopes, the researchers were able to pinpoint the age of the salt crystals and water.
Same parent asteroid
Zag and Monahans are of the most common type of meteorite that hits Earth, called chondrites. Scientists believe both came from the same parent asteroid.
The existence of water on the meteorites suggests that water, or evidence of water, may be present on many more meteorites that fall on Earth. If this is the case, water may not be as rare in the solar system as many scientists suggest. And the presence of water on meteorites and asteroids in the solar system would have helped to create the right kind of environment for life to develop outside of Earth.
"You have at least the potential for the evolution of life," Whitby said.
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