Four rock samples (Samples 187-1162A-3R-1 [Piece 3, 10-14 cm], 187-1162A-5R-1 [Piece 19, 99-102 cm], 187-1162B-2R-1 [Piece 1, 1-5 cm], and 187-1162B-6R-1 [Piece 25, 133-136 cm]) were collected at Site 1162 to characterize the microbial community inhabiting this environment (Table T2). All samples were breccia fragments. To sterilize them, the outer surfaces of the rocks were quickly flamed with an acetylene torch, and enrichment cultures and samples for DNA analysis and electron microscope studies were prepared (see "Igneous Rocks" in "Microbiology" in the "Explanatory Notes" chapter).
Fluorescent microsphere tests were carried out for four rock cores to evaluate the extent of contamination caused by drilling fluid (see "Tracer Test" in "Microbiology" in the "Explanatory Notes" chapter and Table T2). Pieces of rock from each core were rinsed in nanopure water, and the collected water was filtered. Thin sections were used to examine the extent of contamination inside some samples. Filters and thin sections were examined under a fluorescence microscope for the presence of microspheres. Microspheres were detected on all four filters; in the thin sections, microspheres were located both inside fractures and on thin-section surfaces. The microspheres on the polished surfaces were most often found close to fractures or to thin-section (i.e., piece) margins and may have been relocated by polishing. Thirty-seven microspheres were observed in thin sections from Core 187-1162A-2R, two from Core 187-1162B-2R, and 45 from Core 187-1162B-11R. Core 187-1162B-11R had a very low recovery; therefore, no thin sections were made.