Nine requirements for the origin of Earth's life:Not at the hydrothermal vent,but in a nuclear geyser system

The origin of life on Earth remains enigmatic with diverse models and debates.Here we discuss essential requirements for the first emergence of life on our planet and propose the following nine requirements:(1)an energy source(ionizing radiation and thermal energy);(2)a supply of nutrients(P.K.REE.etc.);(3)a supply of life-constituting major elements;(4)a high concentration of reduced gases such as CH_4,HCN and NH_3;(5)dry-wet cycles to create membranes and polymerize RNA;(6)a non-toxic aqueous environment;(7)Na-poor water;(8)highly diversified environments,and(9)cyclic conditions,such as dayto-night,hot-to-cold etc.Based on these nine requirements,we evaluate previously proposed locations for the origin of Earth's life,including:(1)Darwin's "warm little pond",leading to a "prebiotic soup" for life;(2)panspermia or Neo-panspermia(succession model of panspermia);(3)transportation from/through Mars;(4)a deepsea hydrothermal system;(5)an on-land subduct ion-zone hot spring,and(6)a geyser systems driven by a natural nuclear reactor.We conclude that location(6)is the most ideal candidate for the o rigin point for Earth's life because of its efficiency in continuously supplying both the energy and the necessary materials for life,thereby maintaining the essential "cradle" for its initial development.We also emphasize that falsifiable working hypothesis provides an important tool to evaluate one of the biggest mysteries of the universe-the origin of life.     

Primary production and community respiration in a warm streamer associated with Kuroshio warm core ring in spring

Daily rates of gross primary production, net community production and community respiration were determined in spring of 1997 at two stations in a warm streamer off Sanriku, Japan fromin vitro changes in dissolved oxygen. The phytoplankton community was composed of chlorophytes, cryptophytes and prymnesiophytes as determined by biomarker pigment analysis. Gross production, integrated from the surface to its 1% light level was 52.5 and 80.4 mmol O₂ m⁻²d⁻¹. The difference in gross production is ascribed to variations in photosynthetic activity of the population. Community respiration was 17.4 and 49.5 mmol O₂ m⁻²d⁻¹, and positive net community production was found within the euphotic zone. The contribution of autotrophic and heterotrophic respiration to community respiration was estimated on the basis of the observed respiration and the phytoplankton composition. Heterotrophic respiration was calculated to be highly variable and the observed difference in community respiration was due to heterotrophic respiration. Heterotrophic respiration was considered to play an important role in the rapid mineralization of organic materials.     

A time-series study of particulate matter export in the North Pacific Subtropical Gyre based on Th : U disequilibrium

Depth profiles of total ²³⁴Th (dissolved+particulate) were collected at Station ALOHA (22°45N, 158°00W) in the North Pacific Subtropical Gyre during 9 cruises from April 1999 to March 2000. Samples were collected and processed by a new 2 L technique that enables more detailed depth resolution then previous ²³⁴Th studies. Significant zones of particle export (²³⁴Th deficiency) and particle remineralization (²³⁴Th excess) were measured both temporally and with depth. ²³⁴Th derived particulate carbon (PC) and nitrogen (PN) fluxes were determined with steady-state and non-steady-state models and PC/²³⁴Th and PN/²³⁴Th ratios measured with both in situ pumps and free-drifting particle interceptor traps deployed at 150 m. ²³⁴Th based export estimates of 4.0±2.3 mmol C m⁻² d⁻¹ and 0.53±0.19 mmol N m⁻² d⁻¹, were approximately 60% higher than those measured in PIT style sediment traps from the same time period, 2.4±0.2 mmol C m⁻² d⁻¹ and 0.32±0.08 mmol N m⁻² d⁻¹. Most of this difference is attributable to two large export events that occurred during October and December 1999, when traps undercollected for ²³⁴Th by a factor of 2 to 4. ²³⁴Th export (ThE) ratios based on ²³⁴Th derived PC flux/¹⁴C based primary production ranged from 4% to 22% (average=8.8%). Our results confirm the recent estimates of C export by Emerson et al. (Nature 389 (1997) 951) and Sonnerup et al. (Deep-Sea Research I 46 (1999) 777) and indicate that C export from the oligotrophic ocean must be considered when discussing C sequestration in global climate change.     

Study on the fate of petroleum-derived polycyclic aromatic hydrocarbons (PAHs) and the effect of chemical dispersant using an enclosed ecosystem,mesocosm

Polycyclic Aromatic Hydrocarbons (PAHs) are one of the components found in oil and are of interest because some are toxic. We studied the environmental fate of PAHs and the effects of chemical dispersants using experimental 500 l mesocosm tanks that mimic natural ecosystems. The tanks were filled with seawater spiked with the water-soluble fraction of heavy residual oil. Water samples and settling particles in the tanks were collected periodically and 38 PAH compounds were analyzed by gas chromatography-mass spectrometry (GC-MS). Low molecular weight (LMW) PAHs with less than three benzene rings disappeared rapidly, mostly within 2 days. On the other hand, high molecular weight (HMW) PAHs with more than four benzene rings remained in the water column for a longer time, up to 9 days. Also, significant portions (10-94%) of HMW PAHs settled to the bottom and were caught in the sediment trap. The addition of chemical dispersant accelerated dissolution and biodegradation of PAHs, especially HMW PAHs. The dispersant amplified the amounts of PAHs found in the water column. The amplification was the greater for the more hydrophobic PAHs, with an enrichment factor of up to six times. The increased PAHs resulting from dispersant use overwhelmed the normal degradation and, as a result, higher concentrations of PAHs were observed in water column throughout the experimental period. We conclude that the addition of the dispersant could increase the concentration of water column PAHs and thus increase the exposure and potential toxicity for organisms in the natural environment. By making more hydrocarbon material available to the water column, the application of dispersant reduced the settling of PAHs. For the tank with dispersant, only 6% of chrysene initially introduced was detected in the sediment trap whereas 70% was found in the trap in the tank without dispersant.     

Navigation message demodulation for GPS receiver on-board spinning rockets

We describe a demodulation scheme for the navigation message of GPS receivers on spin-stabilized rockets. Doppler frequencies due to fast and complex dynamics, in particular high-rate spin, cause errors in carrier frequency tracking. The effects of such errors on navigation message demodulation are described through theoretical analysis and numerical simulation. A demodulation scheme that includes a frequency estimator is proposed to account for frequency tracking errors. It is demonstrated that demodulation performance is degraded 5 dB due to frequency uncertainty. Simulation results showed that a demodulator which includes maximum likelihood (ML) frequency estimator achieves near-optimal symbol error rate under these conditions. Demodulation with ML estimator achieves a bit error rate below 10^?5 for a C/N ₀?=?35 dB–Hz, for spin rates below 2.7?Hz, and a rocket radius smaller than 1 m. For the cases in which computational capabilities of the on-board GPS receiver is insufficient to implement the demodulator with ML estimator, frequency estimation methods with low complexity were also tested through numerical simulation. The proposed Kay and Quinn-Fernandes combination achieves a bit error rate below 10^?5 for a C/N ₀?=?37 dB–Hz while requiring 1/10 of processing time.     

Dissolved and particulate trace metals in meltwater from the Rhône glacier

Glacial meltwater and sediment at the source of the River Rhône have been analyzed to determine: 1. the partitioning of Al, Cd, Co, Cu, Cr. Fe, Mn, Ni, Pb and Zn between the water and particulate phase. 2. the particle size ranges which affect the dissolved trace metal ion composition of the meltwater and 3. the availability (potential release) of the ten trace metal ions from the sediment. Greater than 80% of the total Cd, Cu, Mn, Ni and Zn were found to be in operationally-defined (0.4 μm) dissolved forms. Fe and Al in the meltwater are primarily associated with particles in the size range 0.4–8 μm, while Cd. Cu, Mn, Ni and Zn occur with particles smaller than 0.1 μm. For the sediment, Cu, Ni and Pb were significantly present as exchangeable forms; only Cu, Ni, Pb and Zn were determined as organicallybound forms.     

Correlation between Expansion Rate of the Coronal Magnetic Field and Solar Wind Speed in a Solar Activity Cycle

Thirteen synoptic maps of expansion rate of the coronal magnetic field (CMF; RBR) calculated by the so-called ‘potential model’ are constructed for 13 Carrington rotations from the maximum phase of solar activity cycle 22 through the maximum phase of cycle 23. Similar 13 synoptic maps of solar wind speed (SWS) estimated by interplanetary scintillation observations are constructed for the same 13 Carrington rotations as the ones for the RBR. The correlation diagrams between the RBR and the SWS are plotted with the data of these 13 synoptic maps. It is found that the correlation is negative and high in this time period. It is further found that the linear correlation is improved if the data are classified into two groups by the magnitude of radial component of photospheric magnetic field, |B^pho_r|; group 1, 0.0 G ≦ |B_r^pho| < 17.8 G and group 2, 17.8 G ≦ |B_r^pho|. There exists a strong negative correlation between the RBR and the SWS for the group 1 in contrast with a weak negative correlation for the group 2. Group 1 has a double peak in the density distribution of data points in the correlation diagram; a sharp peak for high-speed solar wind and a low peak for low-speed solar wind. These two peaks are located just on the axis of maximum variance of data points in the correlation diagram. This result suggests that the solar wind consists of two major components and both the high-speed and the low-speed winds emanating from weak photospheric magnetic regions are accelerated by the same mechanism in the course of solar activity cycle. It is also pointed out that the SWS can be estimated by the RBR of group 1 with an empirical formula obtained in this paper during the entire solar activity cycle.     

Estimation of particulate organic carbon flux in relation to photosynthetic production in a shallow coastal area in the Seto Inland Sea

Sediment trap experiments were carried out three times from 1999 to 2000, in the western part of the Seto Inland Sea (Suo-Sound), Japan. We investigated both the particulate flux and the composition of chemical substances in the sediment trap samples. Based on the results, we discuss the origin of particulate organic carbon (POC) collected by the sediment traps in a coastal area. Moreover, we purposed to estimate the flux of the portion of the POC that is derived from phytoplankton photosynthesis. The fluxes of POC varied between 677 and 3424 mgC m(-2) d(-1). Significant positive correlations between POC and aluminum (Al) fluxes suggested that these components show almost the same behaviour. The mean value of the Al flux was about eight times higher than that of Al burial rates on the sediment surface. Therefore, it seems that the POC flux observed with the sediment traps was considerably overestimated. Moreover, judging from the fact that Al is a typical terriginous element, it seems that most of the POC collected in the sediment traps derived from the re-suspended surface sediment or sediment transported laterally from shallow flanks such as intertidal mudflats. The fluxes of chlorophyll a (Chl a) were independent of the POC fluxes, and a relatively consistent correlation was found between Chl a abundance in the water column and the Chl a flux. Moreover, surface sediment Chl a content was approximately 100 times lower than that of suspended matter. Therefore, resuspension and terriginous contributions to Chl a collected in sediment traps are likely to be negligible. The POC content in the trap samples varied between 22.4 and 70.7 mg g(-1) dry weight. The variations of POC contents were positively correlated with the Chl a contents: POC(mg g(-1))=76.5 x Chl a(mg g(-1)) + 26.0 (r=0.95, p<0.01, n=9). This result shows that POC contents strongly corresponded with phytoplankton and their debris. It was also considered that the fraction of POC derived from phytoplankton primary production could be estimated as Chl a content times a certain factor. In this study, we estimated the flux of the portion of the POC originating from phytoplankton production by multiplying the Chl a fluxes by 76.5 (the mean POC:Chl a ratio in the trap samples). These values varied between 308 and 758 mgC m(-2) d(-1), and accounted for 35.1+/-21.2% of total POC flux. Although the amount of POC that originates from phytoplankton photosynthesis was a small portion of total POC flux, it seems to be a large portion of potential primary production in the water column.     

Shear Strength Development with Burial in Eel River Margin Slope Sediments

As part of the STRATAFORM project, a series of cores were obtained from the Eel River Margin area of Eureka, California. The geotechnical analysis of intact specimens and of reconstituted samples provides some insight on the development of shear strength with burial. The results show the effect of bioturbation in the early part of the lifetime of a sediment. SEDCON tests were used to proposed various relationships which help predict the changes in density, liquidity index, and strength as a function of depth. These relationships are found useful from near the water sediment-interface down to a depth of at least 400 m in the sediment column.     

An overview of the ecosystems of the Barents and Norwegian Seas and their response to climate variability

The principal features of the marine ecosystems in the Barents and Norwegian Seas and some of their responses to climate variations are described. The physical oceanography is dominated by the influx of warm, high-salinity Atlantic Waters from the south and cold, low-salinity waters from the Arctic. Seasonal ice forms in the Barents Sea with maximum coverage typically in March–April. The total mean annual primary production rates are similar in the Barents and Norwegian Seas (80–90 g C m⁻²), although in the Barents, the production is higher in the Atlantic than in the ice covered Arctic Waters. The zooplankton is dominated by Calanus species, C. finmarchicus in the Atlantic Waters of the Norwegian and Barents Seas, and C. glacialis in the Arctic Waters of the Barents Sea. The fish species in the Norwegian Sea are mostly pelagics such as herring (Clupea harengus) and blue whiting (Micromesistius poutassou), while in the Barents Sea there are both pelagics (capelin (Mallotus villosus Müller), herring, and polar cod (Boreogadus saida Lepechin)) and demersals (cod (Gadus morhua L.) and haddock (Melanogrammus aeglefinus)). The latter two species spawn in the Norwegian Sea along the slope edge (haddock) or along the coast (cod) and drift into the Barents Sea. Marine mammals and seabirds, although comprising only a relatively small percentage of the biomass and production in the region, play an important role as consumers of zooplankton and small fish. While top-down control by predators certainly is significant within the two regions, there is also ample evidence of bottom-up control. Climate variability influences the distribution of several fish species, such as cod, herring and blue whiting, with northward shifts during extended warm periods and southward movements during cool periods. Climate-driven increases in primary and secondary production also lead to increased fish production through higher abundance and improved growth rates.