The jarosite group minerals have received increasing attention since the discovery of jarosite on the martian surface by the Mars Exploration Rover Opportunity. Given that jarosite can incorporate foreign ions within its structure, we have investigated the use of jarosite as an indicator of aqueous and biological processes on Earth and Mars. The use of laser desorption Fourier transform mass spectrometry has revealed the presence of organic matter in several jarosite samples from various locations worldwide. One of the ions from the natural jarosites has been attributed to glycine because it was systematically observed in combinations of glycine with synthetic ammonium and potassium jarosites, Na(2)SO(4) and K(2)SO(4). The ability to observe these organic signatures in jarosite samples with an in situ instrumental technique, such as the one employed in this study, furthers the goals of planetary geologists to determine whether signs of life (e.g., the presence of biomolecules or biomolecule precursors) can be detected in the rock record of terrestrial and extraterrestrial samples.

Microbial communities in water from Baltimore Harbor and from the mainstem of Chesapeake Bay were examined for sensitivity to mercuric chloride, monomethyl mercury, stannic chloride, and tributyltin chloride. Acute toxicity was determined by measuring the effects of [3H]thymidine incorporation, [14C]glutamate incorporation and respiration, and viability as compared with those of controls. Minimum inhibitory concentrations were low for all metals (monomethyl mercury, <0.05 ,ug liter-1; mercuric chloride, <1 ,ug liter-1; tributyltin chloride, <5 ,ug liter-) except stannic chloride (5 mg liter-'). In some cases, mercuric chloride and monomethyl mercury were equally toxic at comparable concentrations. The Chesapeake Bay community appeared to be slightly more sensitive to metal stress than the Baltimore Harbor community, but this was not true for all treatments or assays. For culturable bacteria the opposite result was found. Thymidine incorporation and glutamate metabolism were much more sensitive indicators of metal toxicity than was viability. To our knowledge, this is the first use of the thymidine incorporation method for ecotoxicology studies. We found it the easiest and fastest of the three methods; it is at least equal in sensitivity to metabolic measurements, and it likely measures the effects on the greater portion of the natural community.

Identification of mineral-associated biosignatures is of significance for retrieving biochemical information from geological records here on Earth and for detecting signs of life on other planets, such as Mars. An investigation using laser desorption Fourier transform mass spectrometry was conducted to determine whether geomatrix-assisted laser desorption/ionization (GALDI) can be used to detect amino acids (e.g., histidine, threonine, and cysteine) and small proteins (e.g., gramicidin S) associated with mineral phases and whether the geomatrix impacts detection. Iron oxide (Fe 2 O 3 ) and sodium chloride (NaCl) were investigated as clean chemical analogues of hematite and halite, respectively, which have both been detected on the surface of Mars. Samples were prepared by 2 methods: (1) application of analyte solution to the geomatrix surface with subsequent drying; and (2) physical mixing of analyte and geomatrix. Amino acids incorporated within NaCl by physical mixing yielded a better signal-to-noise ratio than those that were applied to the surface of a NaCl pellet. The composition of the geomatrix had an influence on the detection of biomolecules. Peaks corresponding to the cation-attached biomolecular ions were observed for the NaCl prepared samples. However, no biomolecular ion species were observed in samples using Fe 2 O 3 as geomatrix. Instead, only minor peaks that may correspond to ions derived from fragments of the biomolecules were obtained.

[1] An experiment was designed to observe water flow in a simple analogue fractured rock network. The fracture network was modeled by the gaps between an array of limestone blocks, whose permutations generated different realizations of the network. Three out of five of these realizations displayed flow convergence, in contrast to that predicted by porous continuum models. Such convergence occurs because fracture intersections act as capillary barriers that integrate or focus flow within the network.

tion, 1995 through 1997(Faybishenko et al., 1998, and the Hell's Half Acre BasaltThe behavior of unsaturated flow was investigated in a laboratory Infiltration tests, 1997 through 2000 (Wood and Podgormodel. A constant and uniform supply of chemically equilibrated ney, 1999;Podgorney et al., 2000;Wood et al., 2000b). water was introduced to the upper surface of three artificial fractures These tests were conducted at the 100-, 10-, and 1-m in a surrogate fracture network consisting of a thin wall of uncemented limestone blocks. Water was collected from the lower boundary via scales, respectively. Due to the very different behavior fiberglass wicks placed at the bottom of each artificial fracture. Eight observed at these different scales, it can be concluded experiments were conducted to evaluate the repeatability of flow that fractured basalt vadose zone must be conceptualunder nearly identical conditions and to characterize general patterns ized at a hierarchy of scales (Faybishenko et al., 2001). in flow behavior. Collected data revealed that flow generally con-Although the hierarchy of scales approach describes verged to a single fracture in the bottom row of blocks. Periods of behavior of a fractured basalt vadose zone at multiple pathway switching were observed to be more common than periods scales of observation, it fails to provide a means for with steady, constant flow pathways. We noted the importance of scaling between scales of observation and does not defracture intersections for integrating uniform flow and discharging a scribe the unit processes generating flow dynamics ob-"fluid cascade," where water advances rapidly to the next capillary served during field testing. barrier creating a stop and start advance of water through the network. Under very similar initial moisture and boundary conditions, flow in Common to this conceptualization, and indeed to the system was less repeatable than expected. The results of this other studies conducted on a wide variety of fractured simple experiment suggest that the interaction of multiple fracture rock types, is the suggestion that at large spatial scales intersections in a network creates flow behavior not generally recogand relatively short temporal scales, fracture networks nized in popular conceptual and numerical models, (i.e., convergence can facilitate the deep penetration of dissolved contamiof flow, pathway switching, and fluid cascades).