SAHARAN BIOFABRIC: A BIOMARKER FOR PLANETARY SOILS?

Extremely friable, finely fenestrate biofabric reforms episodically in sandy Saharan biomantles immediately after rare rainfall events. (Biofabric is soil fabric produced by biodynamic processes.) The lifeform types and numbers involved in producing Saharan biofabric are unknown and cryptic, but a gram of typical humid mid-latitude biofabric is estimated to contain such enormous numbers and diversities of lifeforms as: bacteria (10^8-9), actinomycetes (10^5-8); fungi (10^5-6); micro-algae (10^3-6); protozoa (10^3-5); nematodes (10^1-2); other invertebrates (10^3-5). Such lifeform numbers are greater per gram than there are people on Earth. Saharan soil lifeforms are narrowly adapted to long periods of drought, often covering many decades, during which no sign of surface life meets the eye. When rain falls, and the soil wets, long dormant organisms spring into life, as observed in January, 1978, weeks after a rare rainfall on 16-17 December, 1977. Our observations were made below the Kiseiba Escarpment in the western Kiseiba-Dungul Depression, south-central Egypt. In 1996 multiple backhoe pits were dug on this surface. The soils in each pit were destratified to bedrock (1-2 m depth), except for a thin (1-8 cm) stratified, episodically mobile surficial sand layer. The soils thus constitute whole soil biomantles, entirely bioturbated and destratified. In January 1998, two years after the pits were dug, the soils were reexamined. Backhoe spoils were initially heaped into conical piles, whereupon the extreme fragility and friability of the soil, plus the mechanical disturbance of excavation, caused most of the sandy soil to be destructured into loose single grains. However, a few fist-sized chunks of the biofabric fortuitously remained intact on most every spoil-pile, each exposed to 2 years of dry, gentle, micro-sculpting by wind. The result was a rare view into extremely friable and delicately fenestrate biofabric composed of miniature biopores, micro-inosculate biochannels, sediment-ingested micropellets, and organism-rearranged grains, expressed three dimensionally as 100 per cent ‘fossil' biofabric. Insofar as biofabric is a signature aspect of all Earth's soils, might minimalist versions, produced perhaps by minimalist lifeforms, be biomarkers in the soils of planets that bear, or once bore, life?