[meteorite-list] Asteroid, Meteorite Impacts Can Preserve Biodata for Millions of Years

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 4 Nov 2015 13:37:40 -0800 (PST)
Message-ID: <201511042137.tA4LbeVB025416_at_zagami.jpl.nasa.gov>

http://www.sci-news.com/geology/science-asteroid-meteorite-impacts-biodata-01867.html

Asteroid, Meteorite Impacts Can Preserve Biodata for Millions of Years
Sci-News.com
Apr 18, 2014

In two separate studies, geologists led by Dr Haley Sapers from the University
of Western Ontario and Dr Pete Schultz of Brown University have found
floral, microbial and organic matter in glass created by ancient asteroid,
comet and meteorite impacts. Such glass samples could provide a snapshot
of environmental conditions at the time of those impacts and could be
a good place to look for signs of ancient life on Mars.

[Image]
This image shows microbial trace fossils in 15 million-year-old impact
glass from the Ries Impact Structure, Germany. Image credit: H.M Sapers
et al.

In the first study, published in the journal Geology, Dr Schultz with
colleagues found fragments of leaves and preserved organic compounds lodged
inside glass created by a several ancient impacts in Argentina.

"The soil of eastern Argentina, south of Buenos Aires, is rife with impact
glass created by at least seven different impacts that occurred between
6,000 and 9 million years ago," Dr Schultz explained.

"One of those impacts, dated to around 3 million years ago, coincides
with the disappearance of 35 animal genera."

"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," he said.

Within glass associated with two of those impacts - one from 3 million
years ago and one from 9 million years ago - the team found exquisitely
preserved plant matter.

"These glasses preserve plant morphology from macro features all the way
down to the micron scale. It's really remarkable," Dr Schultz said.

The glass samples contain centimeter-size leaf fragments, including intact
structures like papillae, tiny bumps that line leaf surfaces. Bundles
of vein-like structures found in several samples are very similar to modern
pampas grass, a species common to that region of Argentina.

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 scientists tried to replicate that preservation in the lab.

They mixed pulverized impact glass with fragments of pampas grass leaves
and heated the mixture at various temperatures for various amounts of
time. The experiments showed that plant material was preserved when the
samples were quickly heated to above 1,500 degrees Celsius.

"It appears that water in the exterior layers of the leaves insulates
the inside layers, allowing them to stay intact. The outside of the leaves
takes it for the interior. It's a little like deep frying. The outside
fries up quickly but the inside takes much longer to cook," Dr Schultz
explained.

In the second study, published also in the journal Geology, Dr Sapers
and her colleagues discovered microbes preserved in impact glass.

They analyzed tubular features in hydrothermally altered impact glass
from the Ries Impact Structure, Germany, that are remarkably similar to
the bioalteration textures observed in volcanic glasses.

Mineral-forming processes cannot easily explain the distribution and shapes
of the Ries tubular features; therefore, they suggest the tubules formed
by microbes etching their way through the impact glass as they excreted
organic acids.

A meteorite impact into a water-rich target such as Earth or Mars has
the potential to generate a post-impact hydrothermal system.

Impact structures, especially post-impact hydrothermal systems, represent
an understudied habitat with potential relevance to early life and the
evolution of early life on Earth.

Understanding the biological significance of impact products such as impact
glass on Earth will better inform the search for evidence of life and
past life on other terrestrial planets such as Mars.
Received on Wed 04 Nov 2015 04:37:40 PM PST