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In this study we use microsampling techniques to explore diagenetic processes in carbonates. These processes are important as they can affect the accuracy of U series chronometry. Fission track maps of deep-sea scleractinian corals show a threefold difference between the minimum and maximum [U] in modern corals, which is reduced to a factor of 2 in fossil corals. We use micromilling and MC-ICP-MS to make detailed analyses of the [U] and δ234Uinitial distributions in corals from 218 ka to modern. Within each fossil coral we observe a large range of δ234Uinitial values, with high δ234Uinitial values typically associated with low [U]. A simple model shows that this observation is best explained by preferential movement of alpha-decay produced 234U atoms (alpha-recoil diffusion). Open-system addition of 234U may occur when alpha-recoil diffusion is coupled with a high [U] surface layer, such as organic material. This process can result in large, whole-coral δ234Uinitial elevations with little effect on the final age. The diagenetic pathways that we model are relevant to both shallow-water and deep-sea scleractinian corals since both exhibit primary [U] heterogeneity and may be subject to U addition.

The Genesis spacecraft, launched on 8 August 2001 from Cape Canaveral, Florida, will be the first spacecraft ever to return from interplanetary space. The fifth in NASAs line of low-cost, Discovery-class missions, its goal is to collect samples of solar wind and return them to Earth for detailed isotopic and elemental analysis. The spacecraft is to collect solar wind for over 2 years, while circling the L1 point 1.5 million km Sunward of the Earth, before heading back for a capsule-style re-entry in September 2004. After parachute deployments mid-air helicopter recovery will be used to avoid a hard landing. The mission has been in development over 10 years, and its cost, including development, mission operations, and initial sample analysis, is approximately $209 million.

The Genesis Discovery mission, to be launched in January 2001, will expose ultrapure materials to the solar wind for about 2 years and then return this sample to Earth for isotopic and chemical analysis in terrestrial laboratories. Sample return missions use the best available instrumentation to achieve mission science goals. To complete the Genesis science objectives, advanced instrumentation that surpasses present laboratory sample analysis capabilities is required. Advanced Analytical Instrumentation Facilities (AAIFs) will be created for the mission to ensure that the best analytical instruments are used. This approach also enables broad participation by NASA scientists in solar wind sample return analysis.