Stable isotope systematics of surface water bodies in the Himalayan and Trans-Himalayan (Kashmir) region

Stable hydrogen (δD) and oxygen (δ 18O) isotope ratios of the headwaters of the Indus and its tributaries, surface ice in glaciers, saline and fresh water lakes and thermal springs in the Himalayan and Trans-Himalayan (Kashmir) region are reported. The δD−δ18 relationship for the river samples shows a slope of 9.12±0.29 which agrees well with the estimate of 8.99±0.33 based on a simple Rayleigh fractionation model. The unique signature of a higher deuterium excess (d) of the 'Western Disturbance' is preserved in these samples. An altitude effect of −0.9 per mil/km is observed in the δ18O of Indus waters. At a lower altitude (Beas) the altitude effect is almost double, indicating that the altitude effect decreases with elevation in this region

Clues to multiple exposure history of some meteorites

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Secular variations in the abundances of heavy nuclei in cosmic rays

The ratios of fluxes of heavy cosmic-ray nuclei [(30 ≤ Z ≤ 40)/(20 > Z ≤ 28), where Z is the atomic number ∫, based on studies of meteorites and lunar samples, show little variation with time, distance in the solar system (1 to 3 astronomical units), or kinetic energy (30 to 2000 megaelectron volts per nucleon). Samples exposed for time intervals of 103 to 108 years show that the variations in the flux of 30 ≤ Z ≤ 40 nuclei relative to that of the iron group nuclei (20 < Z ≤ 28) have remained within the range of (1.3 ± 0.6) × 10-3 during the last billions of years, thus indicating a remarkable similarity in the elemental composition of sources responsible for these nuclei in the cosmic radiation

On the variation of cosmic ray composition in the past

The fossil-track technique is used to determine the abundance of cosmic-ray nuclei with atomic number of at least 30 (VVH group) relative to the iron group in a number of lunar samples and meteorites. This study was undertaken to obtain information about time variations, energy dependences, and spatial variations in the flux of heavy galactic cosmic rays. It is found that for kinetic energies of at least 0.1 GeV/n, variations of the VVH abundance in galactic cosmic rays have remained within a very narrow range, suggesting that the sources of these particles are very similar in their heavy-element abundances. The VVH abundances in the lunar samples and meteorites are also found to exhibit little variation with time or distance from the sun, indicating that these nuclei are probably produced by the same process of nucleosynthesis

Solar proton fluxes during the last million years

The solar flare proton fluxes, averaged over different periods of time, have been determined from Al-26 measured in five selected lunar rocks. The time of exposure of these rocks, ranging from 0.5 to 3.8 million years, were deduced from track profiles due to galactic-cosmic-ray heavy nuclei and from rare-gas data. The observed production rates of Al-26 in all the rocks is in close agreement, implying little variation in average solar flare proton intensity during the past 0.5-, 1-, and 1.5-million-year periods. If the fluxes of solar flare protons and thermal radiation are related, these data exclude any significant changes in solar luminosity during the Pleistocene

The surface radioactivity of lunar rocks-implications to solar activity in the past

A nondestructive beta-gamma coincidence technique was used to measure the radioactivity of lunar rocks both at and near the top surface. The surface of the Apollo 16 rock 61016 has a four times higher positron emitter concentration than does the rock at a depth corresponding to 4 g/sq cm. The activity is attributed to the solar-flare-produced radionuclide Al-26. The surface exposure age and the erosion rate for 61016 were estimated from track density profile and microcrater size distribution studies. The Al-26 depth profile (corrected for surface erosion) indicates an average solar-flare activity during the last 1.5 m.y. which can best be represented by a stated exponential rigidity spectrum

Radioactivity and morphology of Luna 24 samples

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The Torino, H6, meteorite shower

A meteorite shower fell at Torino, Italy on May 18, 1988. Petrographic studies indicate that the stone is an H6 chondrite having features of moderate to severe shock. Chemical analyses of the meteorite are reported. Cosmic ray produced 3He, 21Ne and 126Xe yield an exposure age of about 48 Ma. The cosmic ray track densities in three fragments range between 1.8 to 5 × 105 cm2 suggesting about 99% mass ablation in the atmosphere. Twelve radioisotopes with half lives ranging between 5.6 days to 7.3 × 105 years have been measured with high precision. Marginal signals were observed for several short-lived nuclides and upper limits were obtained for the activity levels of eight radionuclides, some of which have not been hitherto detected in fresh falls. The data are generally consistent with the nuclide production by galactic cosmic rays when modulation due to the solar cycle is taken into consideration