ODU GEOLOGIST'S DISCOVERY OFFERS INSIGHT INTO EARLY LIFE ON EARTH

Nora Noffke, assistant professor in the Department of Ocean, Earth and Atmospheric Sciences at Old Dominion University recently published her discovery of fossil bacteria found in 2.9 billion year-old-rocks from Earth's oldest marine environments. Noffke's discovery opens a new window to understanding early life on Earth and detecting extraterrestrial life on Mars. Her report, "Earth's Earliest Microbial Mats in a Siliciclastic Marine Environment," was published in the international journal Geology of the Geological Society of America, which is highly ranked.

Last summer, Noffke discovered in sandstones characteristic 'microbially induced sedimentary structures' (MISS) that have been caused by bacteria colonizing the seafloor of an ancient ocean. "Before my study, most geologists concentrated on carbonate marine rocks to analyze bacterial structures that are preserved abundantly within them," said Noffke. "It was clear to me that we must find fossil bacteria in marine sandstones of the same ages as well, although the structures must look differently."

"The oldest life forms probably developed around 3.8 billion years ago," she continued. "Whereas those life forms are recorded only as carbon isotopes, the somewhat younger rocks contain characteristic sedimentary structures caused by bacterial activities. Although the bacterial cells themselves are long gone, these structures remained and now are well visible in the rocks."

Noffke traveled to South Africa last summer where she analyzed sandstones exposed in road and river cuts. "The trick to finding the MISS is to search in a past marine environment, where the former hydraulic conditions permitted the growth of microbial mats," she said. In addition to finding the sedimentary structures, Noffke found a few well-preserved fossil bacterial filaments, which is very rare.

"Early Earth of Archean age had no oxygen in the atmosphere. We believe that the 2.9 billion year old MISS record the presence of former cyanobacteria, which like plants today, use sunlight to produce organic material. This photosynthesis by cyanobacteria caused the first production of oxygen already in the oldest period of the Earth's history," she said.