Solar System Ratio Research Articles

12CO+ and 13CO+ fluorescence models for measuring the 12C/13C isotopic ratio in comets

Context. CO is an abundant species in comets, creating CO+ ion with emission lines that can be observed in the optical spectral range. A good modeling of its fluorescence spectrum is important for a better measurement of the CO+ abundance. Such a species, if abundant enough, can also be used to measure the 12C/13C isotopic ratio. Aims. This study uses the opportunity of a high CO content observed in the comet C/2016 R2 (PanSTARRS), which created bright CO+ emission lines in the optical range, to build and test a new fluorescence model of this species and to measure the 12C/13C isotopic ratio in this chemical species for the first time with ground-based observations. Methods. Thanks to laboratory data and theoretical works available in the scientific literature, we developed a new fluorescence model both for 12CO+ and 13CO+ ions. The 13CO+ model can be used for coadding faint emission lines and to obtain a sufficient signal-to-noise ratio to detect this isotopologue. Results. Our fluorescence model provides a good modeling of the 12CO+ emission lines, allowing us to publish revised fluorescence efficiencies. Based on similar transition probabilities for 12CO+ and 13CO+, we derive a 12C/13C isotopic ratio of 73±20 for CO+ in comet C/2016 R2. This value is in agreement with the Solar System ratio of 89±2 within the error bars, but is also consistent with the 12C/13C ratio in local interstellar medium (68±15).

Galactic Interstellar Sulfur Isotopes: A Radial 32S/34S Gradient?

Abstract We present observations of 12C32S, 12C34S, 13C32S, and 12C33S J = 2−1 lines toward a large sample of massive star-forming regions by using the Arizona Radio Observatory 12 m telescope and the IRAM 30 m. Taking new measurements of the carbon 12C/13C ratio, the 32S/34S isotope ratio was determined from the integrated 13C32S/12C34S line intensity ratios for our sample. Our analysis shows a 32S/34S gradient from the inner Galaxy out to a galactocentric distance of 12 kpc. An unweighted least-squares fit to our data yields 32S/34S = (1.56 ± 0.17)D GC + (6.75 ± 1.22) with a correlation coefficient of 0.77. Errors represent 1σ standard deviations. Testing this result by (a) excluding the Galactic center region, (b) excluding all sources with C34S opacities >0.25, (c) combining our data and old data from previous study, and (d) using different sets of carbon isotope ratios leads to the conclusion that the observed 32S/34S gradient is not an artifact but persists irrespective of the choice of sample and carbon isotope data. A gradient with rising 32S/34S values as a function of galactocentric radius implies that the solar system ratio should be larger than that of the local interstellar medium. With the new carbon isotope ratios, we indeed obtain a local 32S/34S isotope ratio about 10% below the solar system one, as expected in the case of decreasing 32S/34S ratios with time and increased amounts of stellar processing. However, taking older carbon isotope ratios based on a lesser amount of data, such a decrease is not seen. No systematic variation of 34S/33S ratios along galactocentric distance was found. The average value is 5.9 ± 1.5, the error denoting the standard deviation of an individual measurement.

The presolar grain inventory of fine‐grained chondrule rims in the Mighei‐type (CM) chondrites

AbstractWe investigated the inventory of presolar silicate, oxide, and silicon carbide (SiC) grains of fine‐grained chondrule rims in six Mighei‐type (CM) carbonaceous chondrites (Banten, Jbilet Winselwan, Maribo, Murchison, Murray and Yamato 791198), and the CM‐related carbonaceous chondrite Sutter's Mill. Sixteen O‐anomalous grains (nine silicates, six oxides) were detected, corresponding to a combined matrix‐normalized abundance of ~18 ppm, together with 21 presolar SiC grains (~42 ppm). Twelve of the O‐rich grains are enriched in 17O, and could originate from low‐mass asymptotic giant branch stars. One grain is enriched in 17O and significantly depleted in 18O, indicative of additional cool bottom processing or hot bottom burning in its stellar parent, and three grains are of likely core‐collapse supernova origin showing enhanced 18O/16O ratios relative to the solar system ratio. We find a presolar silicate/oxide ratio of 1.5, significantly lower than the ratios typically observed for chondritic meteorites. This may indicate a higher degree of aqueous alteration in the studied meteorites, or hint at a heterogeneous distribution of presolar silicates and oxides in the solar nebula. Nevertheless, the low O‐anomalous grain abundance is consistent with aqueous alteration occurring in the protosolar nebula and/or on the respective parent bodies. Six O‐rich presolar grains were studied by Auger Electron Spectroscopy, revealing two Fe‐rich silicates, one forsterite‐like Mg‐rich silicate, two Al‐oxides with spinel‐like compositions, and one Fe‐(Mg‐)oxide. Scanning electron and transmission electron microscopic investigation of a relatively large silicate grain (490 nm × 735 nm) revealed that it was crystalline åkermanite (Ca2Mg[Si2O7]) or a an åkermanite‐diopside (MgCaSi2O6) intergrowth.

Biokinetics of yttrium and comparison with its geochemical twin holmium

The transition metal yttrium (Y, atomic number 39) is chemically similar to elements in the lanthanide family (atomic numbers 57–71) and is found with the lanthanides in rare earth ores. Yttrium and the lanthanide holmium are referred to as geochemical twins because they generally show little fractionation from metamorphic or weathering processes, due to their closely similar chemical properties and nearly identical ionic radii. Extensive measurements on rocks, soils, and meteorites indicate that the Y/Ho mass concentration ratio rarely falls far from the so-called chondritic or solar system ratio of ∼26. This paper presents a new biokinetic model for yttrium in adult humans and examines whether yttrium and holmium may be biological as well as geochemical twins, considering model-based comparisons of their systemic behaviours in adult humans and model-free comparisons of their concentration ratios in human tissues and various types of vegetation. It appears that yttrium and holmium behave similarly in the human body and that their concentration ratios tend to cluster near the chondritic value in human tissues as well as plants, but the comparative information is too limited and imprecise to determine whether they are extremely close biological analogues.

Parsec-scale Variations in the 7Li i/6Li i Isotope Ratio Toward IC 348 and the Perseus OB 2 Association* †

Abstract Measurements of the lithium isotopic ratio in the diffuse interstellar medium from high-resolution spectra of the Li i λ6708 resonance doublet have now been reported for a number of lines of sight. The majority of the results for the 7Li/6Li ratio are similar to the solar system ratio of 12.2, but the line of sight toward o Per, a star near the star-forming region IC 348, gave a ratio of about two, the expected value for gas exposed to spallation and fusion reactions driven by cosmic rays. To examine the association of IC 348 with cosmic rays more closely, we measured the lithium isotopic ratio for lines of sight to three stars within a few parsecs of o Per. One star, HD 281159, has 7Li/6Li ≃ 2 confirming production by cosmic rays. The lithium isotopic ratio toward o Per and HD 281159 together with published analyses of the chemistry of interstellar diatomic molecules suggest that the superbubble surrounding IC 348 is the source of the cosmic rays.

Assessment of Solar Water Heating In Cyprus: Utility, Development and Policy

The main objective of this study is to assess solar water heaters’ utility, development and policy in Cyprus. The study reviews the relevance of solar water heaters in Cyprus from users’ perspective. Cyprus has the highest per capital solar water heater system ratio in the world with no solar water heating systems policy in place currently. Data were collected from some local manufacturer/sellers of the system and residents of one thousand (1,000) housing units that utilize solar water heating systems interviewed on the system’s usefulness and viability in the long and short term. SPSS is deployed in analyzing the data collected and a policy that will further enhance the development of solar water heaters is proposed. In Cyprus, solar water heater are of the thermo-syphon type and consist of two flat-plate solar collectors having an absorber area between 160 X 80 cm for locally manufactured products and 190 x 90 cm for imported ones. It is estimated that the number of systems installed in Cyprus exceeds 80,000 units for residential buildings. From the results, eight out of every ten houses has solar water heaters installed and about 50% of houses without solar water heating systems have plans of installing the system soon. Most of the hot water produced by the system are used for bathing and it is noteworthy to mention that over 80% of the respondents interviewed agrees that the system is worth investing in. A comprehensive report of all the findings from this study is properly presented in the paper.

Pd–Ag chronology of volatile depletion, crystallization and shock in the Muonionalusta IVA iron meteorite and implications for its parent body

Muonionalusta, a Group IVA iron meteorite, was analyzed for its 107Pd–107Ag isotope systematics by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) in order to better constrain the initial Solar System abundance of 107Pd and to provide high resolution chronology of the evolution of its parent body. Six metal samples from Muonionalusta yield Ag abundances between 0.1012 and 1.461ng/g, 107Ag/109Ag between 1.131 and 1.805, with 108Pd/109Ag ratios of 2201 to 52,300. The metal Pd/Ag and Ag isotopic data are correlated with a slope corresponding to a 107Pd/108Pd of (2.15±0.30)×10−5. If the Pd–Ag and Pb–Pb isotope systems closed at the same time in Muonionalusta, i.e., 2–3Ma after CAI formation, then an initial Solar System ratio of 107Pd/108Pd=(2.8±0.5)×10−5 can be inferred. One troilite sample contains 8.478ng/g Ag and has a 107Ag/109Ag ratio of 1.0833; its Pd concentration is 205.2ng/g corresponding to a low 108Pd/109Ag of 13.56. The Pd–Ag results for this troilite plot near the extrapolation of the line passing through the metal points and define an initial 107Ag/109Ag that is substantially higher than chondritic, indicating that Muonionalusta formed from a precursor with high Pd/Ag. Pd and Ag concentrations in Muonionalusta metal suggest fractional crystallization from a source having Pd/Ag>4500, but the initial Ag isotopic composition for Muonionalusta troilite limits the duration of the high Pd/Ag to an interval of ≤0.6Ma before cooling to closure of the Pd–Ag system. This result suggests that depletion of Ag and other volatile elements occurred shortly before accretion and cooling of the IVA parent body, and may have been associated with violent disruption of a progenitor to the IVA parent. Another troilite sample, its chromite inclusions and adjacent metal were isotopically homogenized locally after 107Pd had decayed, possibly by a later episode of shock >50Ma after Solar System formation.

HINTS FOR NEUTRINO-PROCESS BORON IN PRESOLAR SILICON CARBIDE GRAINS FROM SUPERNOVAE

We have studied more than 1000 presolar silicon carbide (SiC) grains from the Murchison CM2 chondrite for Cand Si-isotopic compositions. Twelve SiC X grains, characterized by strong enrichments in 28 Si and believed to originate from Type II Supernovae (SNeII), were also measured for Li- and B-isotopic compositions. None of these grains show resolvable isotope anomalies in Li or B. For the seven X grains without Li and B contributions from nearby or attached SiC grains of distinct origins we find on average 7 Li/ 6 Li = 11.83 ± 0.29 (solar system: 12.06) and 11 B/ 10 B = 4.68 ± 0.31 (solar system: 4.03). The average 7 Li/ 6 Li is compatible with the solar system ratio and the lithium in the X grains is likely largely dominated by contaminating Li of laboratory or meteoritic origin. Also, most of the boron in X grains appears to be contamination but the small 11 B excess of ∼16%, significant at the 2σ level, can be considered a hint for the presence of boron produced by the neutrino process in the parent SNeII. Despite this finding, a quantitative comparison of the B isotope and abundance data of X grains with model predictions reveals deficiencies in our current understanding of the details of B production in SNeII as well as on B chemistry and condensation in SNII ejecta.

ISOTOPIC TITANIUM ABUNDANCES IN LOCAL M DWARFS

Relative abundances of the five stable isotopes of titanium (^46Ti to ^50Ti) are measured for 11 M dwarfs belonging to the thin disk (four stars), thick disk (three stars), the halo (one star), and either the thick or the thin disk (three stars). Over the metallicity range of the sample (-1<[Fe/H]<0), the isotopic ratios are approximately constant to the solar system ratios. There is no discernible difference between the isotopic ratios for thin and thick disk stars. Isotopic ratios are in fair accord with recent calculations of Galactic chemical evolution despite the fact that such calculations underpredict [Ti/Fe] by about 0.4 dex at all metallicities.

Co-Production of Light p-, s- and r-Process Isotopes in the High-Entropy Wind of Type II Supernovae

AbstractWe have performed large-scale nucleosynthesis calculations within the high-entropy-wind (HEW) scenario of Type II supernovae. The primary aim was to constrain the conditions for the production of the classical ‘p-only’ isotopes of the light trans-Fe elements. We find, however, that for electron fractions in the range 0.458 ≤ Ye ≤ 0.478, sizeable abundances of p-, s- and r-process nuclei between 64Zn and 98Ru are coproduced in the HEW at low entropies (S ≤ 100) by a primary charged-particle process after an α-rich freezeout. With the above Ye–S correlation, most of the predicted isotopic abundance ratios within a given element, e.g. 64Zn(p)/70Zn(r) or 92Mo(p)/94Mo(p), as well as of neighboring elements, e.g. 70Ge(s + p)/74Se(p) or 74Se(p)/78Kr(p) agree with the observed Solar-System ratios. Taking the Mo isotopic chain as a particularly challenging example, we show that our HEW model can account for the production of all 7 stable isotopes, from ‘p-only’ 92Mo, via ‘s-only’ 96Mo up to ‘r-only’ 100Mo. Furthermore, our model is able to reproduce the isotopic composition of Mo in presolar SiC X-grains.

The OB association origin of galactic cosmic rays

The isotopic abundances of neon, iron, and a number of other species in the galactic cosmic rays have been measured using the Cosmic Ray Isotope Spectrometer (CRIS) aboard the NASA Advanced Composition Explorer (ACE) spacecraft. We compare our data to results from two-component Wolf–Rayet (WR) models. The largest deviations of galactic cosmic ray (GCR) isotope ratios from solar-system ratios predicted by these models are 12C/16O, 22Ne/20Ne, and 58Fe/56Fe. Our measured abundance ratios show good agreement with the model predictions. All of our measured isotopic ratios are consistent with a GCR source consisting of ∼20% of WR material mixed with ∼80% material with solar-system composition. Since WR stars are evolutionary products of OB stars, and most OB stars exist in OB associations, the good agreement of our data with these models strongly suggests that OB associations are the most probable source of at least a substantial fraction of GCRs. In previous work we have shown that the primary 59Ni (which is radioactive and decays only by electron-capture) synthesized in supernovae has decayed prior to being accelerated to GCRs, indicating a time interval between nucleosynthesis and acceleration of >105 yr. In this paper we describe a scenario that should allow most of the 59Ni to decay in the OB association environment and conclude that OB associations are the likely source of most GCRs.

OB Associations, Wolf–Rayet Stars, and the Origin of Galactic Cosmic Rays

We have measured the isotopic abundances of neon and a number of other species in the galactic cosmic rays (GCRs) using the Cosmic Ray Isotope Spectrometer (CRIS) aboard the ACE spacecraft. Our data are compared to recent results from two-component (Wolf–Rayet material plus solar-like mixtures) Wolf–Rayet (WR) models. The three largest deviations of galactic cosmic ray isotope ratios from solar-system ratios predicted by these models, 12C/16O, 22Ne/20Ne, and 58Fe/56Fe, are very close to those observed. All of the isotopic ratios that we have measured are consistent with a GCR source consisting of ∼20% of WR material mixed with ∼80% material with solar-system composition. Since WR stars are evolutionary products of OB stars, and most OB stars exist in OB associations that form superbubbles, the good agreement of our data with WR models suggests that OB associations within superbubbles are the likely source of at least a substantial fraction of GCRs. In previous work it has been shown that the primary 59Ni (which decays only by electron-capture) in GCRs has decayed, indicating a time interval between nucleosynthesis and acceleration of >105 y. It has been suggested that in the OB association environment, ejecta from supernovae might be accelerated by the high velocity WR winds on a time scale that is short compared to the half-life of 59Ni. Thus the 59Ni might not have time to decay and this would cast doubt upon the OB association origin of cosmic rays. In this paper we suggest a scenario that should allow much of the 59Ni to decay in the OB association environment and conclude that the hypothesis of the OB association origin of cosmic rays appears to be viable.

Superbubbles, Wolf-Rayet stars, and the origin of galactic cosmic rays

The abundances of neon and several other isotopic ratios in the galactic cosmic rays (GCRs) have been measured using data from the Cosmic Ray Isotope Spectrometer (CRIS) aboard the Advanced Composition Explorer (ACE). We have derived the 22Ne/20Ne ratio at the cosmic-ray source using the measured 21Ne, 19F, and 17O abundances as ‘‘tracers’’ of secondary isotope production. Using this approach, the 22Ne/20Ne abundance ratio obtained for the cosmic-ray source is 0.387 ± 0.007 (stat.) ± 0.022 (syst.). This corresponds to an enhancement by a factor of 5.3±0.3 over the 22Ne/20Ne ratio in the solar wind. We compare our data for neon and refractory isotope ratios, and data from other experiments, with recent results from two-component Wolf- Rayet (WR) models. The three largest deviations of GCR isotope ratios from solarsystem ratios predicted by these models, 12C/16O, 22Ne/20Ne, and 58Fe/56Fe, are present in the GCRs. In fact, all of the isotope ratios that we have measured are consistent with a GCR source consisting of about 80% material with solar-system composition and about 20% of WR material. Since WR stars are evolutionary products of O and B stars, and most OB stars exist in OB associations that form superbubbles, the good agreement of these data with WR models suggests that superbubbles are the likely source of at least a substantial fraction of GCRs.

Cosmic‐Ray Neon, Wolf‐Rayet Stars, and the Superbubble Origin of Galactic Cosmic Rays

We report the abundances of neon isotopes in the Galactic cosmic rays (GCRs) using data from the Cosmic Ray Isotope Spectrometer (CRIS) aboard the Advanced Composition Explorer (ACE). These abundances have been measured for seven energy intervals over the energy range of 84 ≤ E/M ≤ 273 MeV nucleon^(-1). We have derived the ^(22)Ne/^(20)Ne ratio at the cosmic-ray source using the measured ^(21)Ne, ^(19)F, and ^(17)O abundances as tracers of secondary production of the neon isotopes. Using this approach, the ^(22)Ne/^(20)Ne abundance ratio that we obtain for the cosmic-ray source is 0.387 ± 0.007(statistical) ± 0.022(systematic). This corresponds to an enhancement by a factor of 5.3 ± 0.3 over the ^(22)Ne/^(20)Ne ratio in the solar wind. This cosmic-ray source ^(22)Ne/^(20)Ne ratio is also significantly larger than that found in anomalous cosmic rays, solar energetic particles, most meteoritic samples of matter, and interplanetary dust particles. We compare our ACE CRIS data for neon and refractory isotope ratios, and data from other experiments, with recent results from two-component Wolf-Rayet (W-R) models. The three largest deviations of GCR isotope ratios from solar system ratios predicted by these models, ^(12)C/^(16)O, ^(22)Ne/^(20)Ne, and ^(58)Fe/^(56)Fe, are indeed present in the GCRs. In fact, all of the isotope ratios that we have measured are consistent with a GCR source consisting of about 80% material with solar system composition and about 20% W-R material. Since W-R stars are evolutionary products of OB stars, and most OB stars exist in OB associations that form superbubbles, the good agreement of these data with W-R models suggests that superbubbles are the likely source of at least a substantial fraction of GCRs.

The superbubble origin for galactic cosmic rays

The source of energy for cosmic-ray acceleration appears to be shock waves driven by supernova (SNe) ejecta. The great majority (80–90%) of SNe (SNII and SNIb) are formed by the core collapse of young, massive O and B stars. However, it has been known for more than forty years that the births of such massive stars in stellar clumps, termed OB associations, are correlated in space and time. The combined ejecta of core-collapse SNe, occurring at the deaths of these massive stars, create low-density (∼5.0 × 10 −3 cm −3) superbubbles that reach dimensions of several hundred pc. The occurrence of correlated SNe in superbubbles affects not just the source of cosmic-ray energy, SNe shock waves, it impinges as well on the elemental and isotopic source abundances of cosmic-ray nuclei. We argue that the well-known anomalous cosmic-ray 22Ne/ 20Ne ratio, a factor of five times the Solar System ratio, results from a mixing of freshly synthesized nucleosynthetic material in supernova active cores of superbubbles. Although diluted by mixing with older, lower metallicity interstellar gas, the mean metallicities in the superbubble, SNe-dominated cores are high ∼3 times the Solar System value.

Nucleosynthesis as a result of multiple delayed detonations in type Ia supernovae

The explosion of a white dwarf of mass 1.36 M ⊙ has been simulated in three dimensions with the aid of a SPH code. The explosion follows the delayed detonation paradigm. In this case the deflagration-detonation transition is induced by the large corrugation of the flame front resulting from Rayleigh-Taylor instability and turbulence. The nucleosynthetic yields have been calculated, showing that some neutronized isotopes such as 54 Fe or 58 Ni are not overproduced with respect to the solar system ratios. The distribution of intermediate-mass elements is also compatible with the spectra of normal SNIa. The exception is, however, the abundance of carbon and oxygen, which are overproduced.

Determination of the abundance of aluminum in the solar wind with SOHO/CELIAS/MTOF

The Al/Mg abundance ratio provides an excellent test case for investigating possible fractionation processes among low First lonization Potential (FIP) elements in the solar wind. Al and Mg are refractory elements; their abundance ratio has been well determined in solar system materials and inferences for the abundance ratio in the solar atmosphere are reliable. Al and Mg are at neighboring masses and have similar charge state properties in the solar corona; hence mass fractionation effects in the solar wind acceleration process and instrumental mass fractionation are minimal. From first observations during two relatively short periods, one recorded in coronal hole associated solar wind, the other in typical interstream solar wind, it is concluded that the solar wind ratio in both regimes is consistent with the solar system ratio. The Al/Mg ratio in interstream solar wind is 0.081±0.012, and in the sample of coronal hole associated solar wind it amounts to 0.076±0.011. A comparison of these results with the solar system ratio of 0.079±0.005 gives no indication for fractionation occurring among low FIP elements in the solar wind.

Carbon Isotope Abundances in Comets

Rotational lines of 13C14N have been identified in high-resolution (λ/Δλ ~ 60,000) echelle spectra of the CN B2Σ+-X2Σ+ (0-0) band in three comets. The 12C/13C abundance ratios determined using a full fluorescence excitation model for comets Levy (C/1990 K1), Austin (C/1989 X1), and Okazaki-Levy-Rudenko (C/1989 XIX) are 90 ± 10, 85 ± 20, and 93 ± 20, respectively, consistent with the solar system ratio, 90. A lower limit for the nitrogen isotope ratio, 12C14N/12C15N 200, found for comet Levy is consistent with previous comet measurements and the solar system value, 272. The mean CN carbon isotope ratio in the five comets measured to date is 12C14N/12C15N = 90 ± 10, and the mean for the three molecular species C2, HCN, and CN measured in nine comets is 101 ± 15. Consistency of the cometary carbon isotope ratios with the bulk solar system value indicates (1) chemical homogeneity in the outer protosolar nebula, (2) minimal isotopic fractionation in the protosolar precursor molecular cloud, and (3) that comets formed coevally with the solar system. The 14% difference between the solar system (90) and the present solar neighborhood interstellar 12C/13C ratio (77 ± 7) may be indicative of significant Galactic 13C enrichment over the past 4.6 Gyr. However, even though models can match to within a factor of 2 the solar system abundances, including the carbon isotope ratio, other evidence suggests that simple homogeneous Galactic evolution models may not be adequate to explain detailed stellar and interstellar abundances in the Galaxy.

The Interstellar Lithium Isotope Ratio Toward Per OB2

We are conducting a survey on the 7Li/6Li ratio in interstellar space in order to seek limits on the variation in this ratio. The analysis is based on the technique we adopted in extracting the 11B/10B ratio. This technique uses a line of comparable strength, from a species likely to occupy the same volume of the interstellar cloud, as a template for separating velocity components within the line profile. For our study of the 7Li/6Li ratio, the K I line at 4044 Å serves as the velocity template. Our initial focus is on the variation in the 7Li/6Li ratio around the star-forming region IC 348. Our high-resolution observations of the Li I lines toward o and ζ Per show remarkably different isotope ratios: 7Li/6Li = 2-4 and 11, respectively, where the Solar System ratio is 12.3 and cosmic ray spallation yields a ratio of about 2. The significance of the very low ratio toward o Per is that it is essentially the value predicted for cosmic rays through spallation reactions. The direction to o Per passes closer to IC 348, a site of massive star formation, than does the line of sight to ζ Per. Furthermore, our analysis of OH column densities (Federman, Weber, &amp; Lambert 1996) showed that the cosmic ray flux through o Per's diffuse clouds is higher than average, presumably reflecting the nearby presence of IC 348.

The11B/10B Ratio of Local Interstellar Diffuse Clouds

The isotopic ratio 11B/10B of gas in diffuse interstellar clouds toward ? Oph, ? Ori, and ? Sco is measured using HST/Goddard High Resolution Spectrograph echelle spectra of the B II 1362 ? line. To within the errors of measurement, the three lines of sight give identical results for a mean value of 11B/10B = 3.4 ? 0.7, a value quite similar to the solar system ratio of 4.05. These results show that the latter value is not highly anomalous and that a ratio higher than 2.5, as predicted for boron produced from spallation reactions controlled by high-energy cosmic rays, most probably requires a general explanation. The observed ratio is consistent with additional boron production either by spallation by low-energy (Orion) cosmic rays or by neutrino-induced spallation of carbon in Type II supernovae. The total abundance of B in the diffuse clouds is a factor of 5 less than the meteoritic value. This depletion of B is consistent with that found for Cu and Ga, two elements with a condensation temperature similar to B.