Our former binary Sun is suggested to have spiraled in and merged in a luminous red nova (LRN) at 4,567 Ma, creating the r-process radionuclides of the early solar system (aluminum-26, iron-60 et al.) and its helium-burning stable-isotope enrichment (carbon-12 and oxygen-16 et al.).
Carbonaceous chondrite anhydrous minerals (CCAM), including CAI and chondrules, plot with a 1 slope toward the lower left corner of the graph 3-isotope oxygen graph (δ17O vs. δ18O), with a 1 slope representing complete mixing due to rapid condensation from a vapor phase. (The anhydrous modifier is significant since any subsequent aqueous alteration, forming hydrous minerals, would occur slowly, allowing mass fractionation which would move the altered material off the 1 slope line.) By comparison, complete fractionation of oxygen isotopes plot as a 1/2 slope, since 17O – 16O = 1 unit of atomic weight and 18O – 16O = 2 units of atomic weight. The terrestrial fractionation line (TFL) plots with a slope of .52, nominally 1/2. The low cooling rate from a molten magma state on Earth and the similarly slow rate of authigenic precipitation from an aqueous state provides a significant opportunity for chemical reactions to occur within the temperature window in which mass fractionation is significant. So the 1 slope of CCAM merely represents complete mixing while the 1/2 slope of the terrestrial fractionation line (TFL) merely represents complete fractionation.
When comparing completely fractionated materials such as terrestrial basalt and Mars meteorite basalt, it can be convenient to force force the nominal 1/2 slope (.52 slope for the TFL) to zero, making it a horizontal line, with the conversion:
∆17O = δ17O – .52 δ18O
∆17O vs. δ18O plots the TFL horizontally with igneous Mars rock on a horizontal rock above.
The degree of 16O enrichment can be be obscured by isotope fractionation when only δ17O (17O/16O) or δ18O (18O/16O) are measured isolation, but the measurement of all three oxygen isotopes and their graphing on a 3-isotope oxygen plot will cause mass-dependent fractionation to wash out, by aligning along a ‘fractionation line’ which is 16O-enrichment dependent. Comparing δ17O or ∆17O to δ18O on a 3-isotope oxygen plot, however, is generally reserved for meteorites, since continental Earth rock is assumedly terrestrial, but if the continental tectonic plates are aqueously and thermally differentiated planetesimal cores from two separate reservoirs (presolar protoplanetary and variably-enriched secondary debris disk) then comparison of all three isotopes becomes significant.
Plotting sufficient terrestrial basalt samples along side Mars meteorite basalt samples shows the two materials lie near fractionation lines, regardless of the extent of mass-dependent fractionation of individual samples. If only that were the end of the story, but ordinary chondrites plot above suggested presolar Mars which makes no sense if they condensed from the secondary debris-disk created by the spiral-in merger of our former binary-Sun at 4,567 Ma and thus were enriched in 16O. Without subsequent aqueous alteration, ordinary chondrites would plot below the TFL due to their suggested greater 16O contamination than Earth rock.
Secondary aqueous alteration may be responsible for forming secondary magnetite with high ∆17O, which raise ordinary chondrites above assumedly presolar Mars on the 3-isotope oxygen plot. “The maximum fractionation between magnetite and liquid H2O is -13.6‰ at 390 K . In the UOC parent asteroid, H2O probably existed as a gaseous phase when magnetite formed. The maximum fractionation between magnetite and gaseous H2O is -10.5‰ at 500 K .” (Choi et al., 1997, Magnetite in unequilibrated ordinary chondrites: evidence for an 17O-rich reservoir in the solar nebula) But rather than a “17O-rich reservoir”, if the mechanism had been a matter of mass-dependent fractionation of gaseous H2O in the crust followed by the escape of the 17O-depleted remainder into interplanetary space, would not the result be the same?
During thermal differentiation of ordinary chondrites, if the temperature had reached the boiling point of water, the lightest-weight H2O molecules containing 16O would be the first to sublime or boil, and the least likely to condense or deposit (the opposite of sublimation), and the fastest to diffuse outward in a vapor phase. And outward mass-dependent fractionation may have been the result of repeated episodes of sublimation and deposition during the warming phase of thermal differentiation of ordinary chondrites which progressively expelled water ice from the core, then the mantle and finally the crust, increasing the degree of fractionation with each cycle. Then oxidation into magnetite selected the most mobile of the remaining oxygen isotopes, preferentially incorporating 17O into magnetite.
The flare-star phase of the Sun following its binary spiral-in stellar merger may be recorded in the 3 million year period of chondrule formation by super-intense solar-flare melting of debris-disk dust accretions, spiraling in toward the Sun by Poynting–Robertson drag.
If stellar-merger nucleosynthesis enriched the Sun in the stable isotopes 12C, 16O, and 20Ne by helium burning, then the stellar-merger core temperatures may have been in the neighborhood of 100-200 million Kelvins, with r-process nucleosynthesis forming the neutron-rich short-lived radionuclides (SRs) of our early solar system:
7Be, 10Be, 14C, 22Na, 26Al, 36Cl, 41Ca, 44Ti, 53Mn, 54Mn, 60Fe, 63Ni, 91Nb, 92Nb, 107Pd, 129I, 146Sm, 182Hf and 244Pu.
The high velocities necessary to create spallation nuclides in LRNe may have been observed in LRN PTF10fqs from a spiral arm of Messier 99. The breadth of the Ca II emission line may indicate two divergent flows, a high-velocity polar flow (~ 10,000 km/s) and a high-volume, but slower equatorial flow. (Kasliwal, Kulkarni et al. 2011) Some of the SRs may have been created by spallation in the high-velocity polar outflow of the LRNe, particularly 7Be and 10Be, since beryllium is known to be consumed rather than produced within stars.
The solar wind is ~40% poorer in 15N than earth’s atmosphere, as discovered by the Genesis mission. (Marty, Chaussidon, Wiens et al. 2011) The same mission discovered that the Sun is depleted in deuterium, 17O and 18O by ~7% compared to all rocky materials in the inner solar system. (McKeegan, Kallio, Heber et al. 2011) “[T]he 13C/12C ratio of the Earth and meteorites may be considerably enriched in 13C compared to the ratio observed in the solar wind.” (Nuth, J. A. et al., 2011)
The most apparent deficit in the Sun and in debris-disk material, however, may be the δ15N differences between presolar protoplanetary comets and CAIs condensed from solar-merger polar jets from the core, with canonical 26Al.
Most oxygen isotopes variations are only a few per mill (‰), but δ15N departures from terrestrial values are often measured in hundreds of per mille (tens of percent), with a solar difference of δ15N = -386 ‰ and cometary difference of δ15N ≈+800 ‰ for CN and HCN (Chaussidon et al. 2003). So 15N destruction must have been particularly efficient by way of two mechanisms, 15N(p,α)12C and 15N(p,γ)16O, known as the CN and the NO cycles respectively (Caciolli et al. 2011).
Deuterium will also have been destroyed in the solar merger, dramatically lowering the D/H ratio in the Sun and in debris-disk condensates, but the 2:1 difference in mass between H and D often makes fractionation more significant than the degree of depletion, making the D/H ratio a poor measure of the reservoir depletion.
Caciolli, A. et al., 2011, Revision of the 15N(p,γ)16O reaction rate and oxygen abundance in H–burning zones, Astron.Astrophys. 533 (2011) A66 arXiv:1107.4514 [astro-ph.SR].
Choi, B. -G.; McKeegan, K. D.; Krot, A. N.; Wasson, J. T.. 1997, Magnetite in unequilibrated ordinary chondrites: evidence for an 17O-rich reservoir in the solar nebula, Conference Paper, 28th Annual Lunar and Planetary Science Conference, p. 227.
Marty, B.; Chaussidon, M.; Furi E.; Hashizume, K.; Podosek, F.; Wieler, R.; and Zimmermann L., 2003, Nitrogen isotopes in lunar soils: a record of contributions to planetary surfaces in the inner solar system, Ecole Nationale Supérieure de Géologie 54501 Vandoeuvre-lès-Nancy Cedex France Space Science Reviews (Impact Factor: 5.87). 04/2003; 106(1):175-196.