[Rockhounds] 3.5 billion-year-old rock structures are one of the oldest signs of life on Earth

[Kreigh Tomaszewski]

Layered rocks in Western Australia are some of Earth's earliest known life,
according to a new study.

The fossils in question are stromatolites, layered rocks that are formed by
the excretions of photosynthetic microbes. The oldest stromatolites that
scientists agree were made by living organisms date back 3.43 billion
years, but there are older specimens, too. In the Dresser Formation of
Western Australia, stromatolites dating back 3.48 billion years have been
found.

However, billions of years have wiped away traces of organic matter in
these older stromatolites, raising questions about whether they were really
formed by microbes or whether they might have been made by other geological
processes.

The new study's verdict: It was ancient life.

"We were able to find certain specific microstructures within particular
layers of these rocks that are strongly indicative of biological
processes," said *Keyron Hickman-Lewis*
<https://nhm.academia.edu/KeyronHickmanLewis>(opens in new tab), a
paleontologist at the Natural History Museum in London, who led the
research.

The findings could have implications for the search for life on *Mars*
<https://www.livescience.com/facts-about-mars>, Hickman-Lewis told Live
Science. The stromatolites in the Dresser Formation are encrusted in iron
oxide from the reaction of iron with oxygen in the atmosphere. Mars'
surface is similarly oxidized — thus the rusty orange color — but its rocks
could hold similar structures left behind by ancient Martian life,
Hickman-Lewis said.


https://www.livescience.com/oldest-stromatolites-australia