Scientists with NASA's Astrobiology Institute have discovered
evidence that microbial life emerged on land between 2.6 billion
and 2.7 billion years ago, much earlier than previously thought.
Text based on a NASA/Ames press release. Scientists with NASA's
Astrobiology Institute (NAI) have discovered fossilized remnants
of microbial mats that developed on land between 2.6 billion and
2.7 billion years ago in the Eastern Transvaal district of South
Africa. This significant discovery presents the strongest
evidence to date that life on land occurred at a much earlier
stage in Earth's history than was previously believed by most
scientists. It also suggests that an ozone shield and an oxygen-
rich atmosphere existed on Earth 2.6 billion years ago, both
necessary conditions for life on land to emerge. The results are
reported in the November 30, 2000, issue of Nature magazine.
"This important investigation undertaken by an NAI team feeds
into NASA's strategy of using Earth analogs, particularly
analogs present on e