Solar wind and other gases in the regoliths of the Pesyanoe parent object and the moon

Abstract

We report new data from Pesyanoe-90,1 (dark lithology) on the isotopic signature of solar wind (SW) Xe as recorded in this enstatite achondrite which represents a soil-breccia of an asteroidal regolith. The low temperature (≤800°C) steps define the Pesyanoe-S xenon component, which is isotopically consistent with SW Xe reported for the lunar regolith. This implies that the SW Xe isotopic signature was the same at two distinct solar system locations and, importantly, also at different times of solar irradiation. Further, we compare the calculated average solar wind "SW-Xe" signature to Chass-S Xe, the indigenous Xe observed in SNC (Mars) meteorites. Again, a close agreement between these compositions is observed, which implies that a mass-dependent differential fractionation of Xe between SW-Xe and Chass-S Xe is <1.5‰ per amu. We also observe fractionated (Pesyanoe-F) Xe and Ar components in higher temperature steps and we document a fission component due to extinct 244 Pu. Interestingly, the Pesyanoe-F Xe component is revealed only at the highest temperatures (>1200°C). The Pesyanoe-F gas reveals Xe isotopic signatures that are consistent with lunar solar energetic particles (SEP) data and may indicate a distinct solar energetic particle radiation as was inferred for the moon. However, we cannot rule out fractionation processes due to parent body processes. We note that ratios 36 Ar/ 38 Ar ≤5 are also consistent with SEP data. Calculated abundances of the fission component correlate well with radiogenic 40 Ar concentrations, revealing rather constant 244 Pu/K ratios in Pesyanoe, and separates thereof, and indicate that both components were retained. We identify a nitrogen component (δ 15 N = 44‰) of non-solar origin with an isotopic signature distinct from indigenous N (δ 15 N = −33‰). While large excesses at 128 Xe and 129 Xe are observed in the lunar regolith samples, these excesses in Pesyanoe are small. On the other hand, significant 126 Xe isotopic excesses, comparable to relative excesses observed in lunar soils and breccias, are prominent in the intermediate temperature steps of Pesyanoe-90,1.

Solar Wind and Solar System Matter After Mission Genesis

“…Reported ratios 86 Kr/ 84 Kr = 0.303 ± 0.001 and 129 Xe/ 132 Xe = 1.06 ± 0.01, at this time the only values available from Genesis, are consistent with solar data as observed in early etch steps in lunar ilmenite samples (Wieler and Baur, 1994). Martian interior samples (SNC meteorites) also contain a solar type Xe-S component (Ott, 1988;Mathew and Marti, 2001), while SW-implanted Xe components were observed in gas-rich meteorites like Pesyanoe (Marti, 1969;Mathew and Marti, 2003). Minor solar components were observed in 'subsolar' gases in E-chondrites (Crabb and Anders, 1981;Busemann et al, 2003).…”

Galactic cosmic ray‐produced 129Xe and 131Xe excesses in troilites of the Cape York iron meteorite

“…Estimated temperatures of the wire coil during troilite decomposition are <700 °C to 400 °C, as determined by the position within the external furnace. The Xe separation and clean-up procedures in the static-mode mass spectrometric analyses were reported earlier (Mathew and Marti 2003). The Xe mass discrimination was determined and sensitivities monitored by air standard pipettes, and uncertainties in the corrections were propagated in the data (Table 1).…”

Regolith history of the aubritic meteorite parent body revealed by neutron capture effects on Sm and Gd isotopes

“…The relatively frequent occurrence of solar wind (SW) gases in aubrites (Lorenzetti et al, 2003), the discovery of unusual FeO-rich clasts of unknown origin in Pesyanoe (Ivanova et al, 2002;Mathew and Marti, 2003) and of chondritic inclusions in Cumberland Falls (CF) (Mason, 1962) are several reasons to believe that the grains of aubrites had different histories in the regolith of a parent body. Early work on exposure ages (Eberhardt et al, 1965) indicated a cluster of cosmic-ray exposure (CRE) ages near 40 Ma, but such a cluster has been questioned in recent more comprehensive studies (Lorenzetti et al, 2003).…”

“…Large variations of 21 Ne c between the light and dark phases studied by Mü ller and Zähringer (1966) are inconsistent with shielding effects during space irradiation and generate discrepancies in CRE ages (Lorenzetti et al, 2003), but may represent a record of preirradiation of the regolith before compaction into the meteorite. Furthermore, Xe and N isotopic data in the dark portion of the Pesyanoe meteorite suggested the possibility of evolutionary processes before compaction of the meteoritic matter (Mathew and Marti, 2003).…”