Hypervelocity impacts on the early Earth during the heavy bombardment period are expected to lead unique chemical reactions, which have never been driven on the mean reaction fields on the Earth. The quantitative determinations of injection fluxes of various chemical species on the surface environment is necessary to understand how the chemical evolutions had proceed on the early Earth. We also expect that signatures of such impacts might be fixed in impact-related stratifications as unique geochemical products, such as the spherule beds. We are developing a new experimental system to explore the nature of impact-induced chemical reactions using a two-stage light gas gun. The new system allows us to investigate the final gas products in an open system after hypervelocity impacts at ranged from 1 km/s to 7 km/s. We will present the experimental results with water ice and calcite targets at the conference. We can accelerate any projectile with 2 mm in diameter and shoot onto targets with any chemical compositions and can measure final gas products with the proposed method.

This abstract present the previous results of bulk minor and trace element analyses obtained on five type 3 ordinary chondrites (3 LL3, 2 L3). The data obtained for two brecciated type ordinary chondrite are also presented. All these data are obtained on ICP-MS.

Oxygen and sulfur isotope ratios were measured for sulfate ion in monthly precipitation at 6 sampling points in Chugoku district. Three groups are identified from oxygen and sulfur isotope ratios of nss sulfate ion. They are group A (high sulfur isotope ratio group in winter, which is affected by coal combustion in China), group B (low sulfur isotope ratio group in summer, which is mainly affected by oil combustion in Japan), and group C (medium sulfur isotope ratio and high oxygen isotope ratio group in spring). nss-Sr isotope ratio of group C is highest among three groups, which indicates group C is affected by dissolved component of yellow sand. It suggests that sulfate ion in group C is also affected by dissolved component of yellow sand. Measurement of oxygen isotope ratio of yellow sand is necessary to prove this hypothesis.

It has been reported that amino acids can be formed easily from strongly-reducing atmosphere by various energy sources such as spark discharges since 1950s. Primitive Earth atmosphere is, however, assumed to have been only mildly-reducing. We examined possible formation of amino acids from a mixture of CO₂, CH₄, N₂ and H₂O of various mixing ratios by spark discharges, proton irradiation, or UV irradiation. If partial pressure of CH₄ was 10% or less, amino acids were not formed by spark discharges, but amino acids could be formed by proton irradiation even if the partial pressure of CH₄ was as low as 0.5%. It was difficult to form amino acids from mildly-reducing gas atmospheres by solar UV only, but the solar UV flux was much larger than other possible energy sources on the primitive Earth. We are planning to examine possible formation of amino acids by synergy of solar UV and other energy sources like cosmic rays.

We evaluate the effects of gamma-ray from decay of aluminium-26 as an energy source for the formation of organic matter, specially amino acids during aqueous alteration in early planetesimals. We report experiments of gamma-ray irradiation to solutions containing formaldehyde and ammonia. The results suggest that amino acid precursors were formed by the gamma-ray irradiation to the formaldehyde and ammonia water solutions, and the reaction mechanisms could be different from those of heating.