"The Pampas region of Argentina is covered with thick layers of windblown sediment called loess."
Washington, April 19 - Whenever an asteroid or a comet hit the earth in the past, the impact melted tonnes of soil and rock, some of which formed glass as it cooled. Now, a thrilling discovery has found that these impact glasses stored the signatures of ancient life at the time of the impact.
Several such impact glasses have been unearthed from the soil of eastern Argentina, south of Buenos Aires.
These impact glasses are 6,000 to 9 million years old.
One of those impacts, dated to around three million years ago, coincides with the disappearance of 35 animal species as reported earlier, said Pete Schultz, a geologist from Brown University in Rhode Island who led the study.
The discovery also suggests that impact glasses could be a good place to look for signs of ancient life on Mars.
We know these were major impacts because of how far the glass is distributed and how big the chunks are. These glasses are present in different layers of sediment throughout an area about the size of Texas, Schultz noted.
These impact glasses preserve plant morphology from macro features all the way down to the micron scale. It is really remarkable, Schultz added.
The glass samples contain centimetre-size leaf fragments, including intact structures like papillae, tiny bumps that line leaf surfaces.
Chemical analysis of the samples also revealed the presence of organic hydrocarbons, the chemical signatures of living matter.
To understand how these structures and compounds could have been preserved, the lab experiments showed that plant material was preserved when the samples were quickly heated to above 1,500 degrees celsius - at the time of the asteroid or comet impact.
The soil conditions in Argentina that contributed to the preservation of samples in this study are not unlike soils found on Mars.
The Pampas region of Argentina is covered with thick layers of windblown sediment called loess.
Much of the surface of Mars is covered in a loess-like dust, and the same mechanism that preserved the Argentine samples could also work on Mars, Schultz said in the study published in the journal Geology Magazine.