Glass formed millions of years ago in the impact of an asteroid with Earth preserved biological material of ancient plants. The material also preserved samples of the ancient climate. This has provided investigators valuable information about conditions on Earth eons ago.
The meteorite was discovered in Argentina, where two asteroid impacts occurred, the first nine million years ago, and the second six million years later. Pete Schultz of Brown University led a study of ancient plant material caught in the glass. This process is able to preserve material lost in the process of fossilization.
"While fossilization typically occurs over an extended time period as minerals slowly replace organic matter and the host rock [transforms] under pressure, the process documented here is instantaneous," Shultz and his team wrote in the article detailing the discovery.
Some of the biological samples preserved in the glass were pieces of leaves, as large as four-tenths of an inch across. Schultz was able to identify structures in the plant material at a wide range of magnifications.
When the asteroids hit, the heat from the blast engulfed the plants with molten glass reaching 2,700 degrees Fahrenheit. Water on the outside of the leaves may have protected the inner structure long enough to be entombed in the material.
"It turns out the composition of the plant material is very similar to the composition of the impact glass itself. It was very rapidly transferred from one thing to the other, likely due to the rapid and high heat that boiled off that plant material and replaced it with glass," Shultz told the BBC.
Loess, a sediment that covers large stretches of land in the area the asteroid was found, is similar to the wind-blown landscape of Mars. This material may have assisted in the preservation of the remains.
Asteroids have played a major role in the evolution of life on Earth. By studying these pristine samples of ancient life, Shultz and his team believe they may gain a better understanding of these changes.
The impact three million years ago coincides with the disappearance of 35 genera of animals.
Discovery of these ancient remains also suggests that similar processes may have taken place on Mars, preserving ancient biological material and information on the climate.
"Impact glass may be where the 4 billion-year-old signs of life are hiding. On Mars they're probably not going to come out screaming in the form of a plant, but we may find traces of organic compounds, which would be really exciting," Schultz said.
Investigation of organic material trapped inside volcanic glass was published in the journal Geology.