Solar composition from the Genesis Discovery Mission

Abstract

Science results from the Genesis Mission illustrate the major advantages of sample return missions. (i) Important results not otherwise obtainable except by analysis in terrestrial laboratories: the isotopic compositions of O, N, and noble gases differ in the Sun from other inner solar system objects. The N isotopic composition is the same as that of Jupiter. Genesis has resolved discrepancies in the noble gas data from solar wind implanted in lunar soils.(ii) The most advanced analytical instruments have been applied to Genesis samples, including some developed specifically for the mission. (iii) The N isotope result has been replicated with four different instruments. T he Sun has obvious importance to the understanding of the physics of the solar system, but it is of equal major importance to the composition of planetary materials, i.e., the research area known as cosmochemistry. The link between solar and planetary matter is that they have a common origin in the original cloud of gas and dust from which the solar system formed 4.57 × 10 9 years ago. Our gas-dust cloud is the first step in what cosmochemists regard, at least implicitly, as a "Standard Model" for the origin of planetary materials. The formation of the Sun by gravitational collapse of the cloud occurs by the flow of material through an equatorial disk, the "solar nebula," onto the Sun, a process now directly observable in star-forming regions. The Standard Model regards elemental (the relative amounts of different elements) and isotopic (the relative amounts of the isotopes of individual elements) compositions of the solar nebula as homogeneous, at least on large scales relative to the size of individual dust grains. The planetary objects (planets, moons, asteroids, etc

Accurate analysis of shallowly implanted solar wind ions by SIMS backside depth profiling

“…NASA Discovery Mission V, Genesis, collected solar wind in space, 1.5 million km sunward from Earth, for a period of 2.3 years and returned this sample for laboratory analysis (Burnett et al, 2003;Burnett and Team, 2011;Reisenfeld et al, 2013). The solar wind can serve as a proxy for the composition of the Sun and, thus, average of composition of the solar nebula (Marty et al, 2011;McKeegan et al, 2011), provided that fractionation processes occurring during the formation of the solar wind (e.g., Heber et al, 2012a) can be understood and quantitatively modeled.…”

Hayabusa2: Scientific importance of samples returned from C-type near-Earth asteroid (162173) 1999 JU3

“…It is also noteworthy that Westphal et al (2014) recently reported seven contemporary interstellar grains captured by the Stardust Interstellar Dust Collector, which are the first returned interstellar dust particles. Solar-wind particles, captured by the GENESIS spacecraft (2001)(2002)(2003)(2004) (Burnett et al, 2011;Burnett, 2013), provided new interesting information on the oxygen isotopic composition of the Sun (McKeegan et al, 2011). The oxygen isotopic composition of the Sun is close to that of CAIs, which is the oldest refractory rocky components with 16 O-enriched isotopic compositions (e.g., MacPherson, 2014), but is different from most of inner solar system bodies, including the Earth.…”

Cosmochemistry: Understanding the Solar System through analysis of extraterrestrial materials

“…This finding revolutionized our understanding of the Solar System. (ii) Next followed the discovery (9) of excesses of 26 Mg that formed by the in situ decay of 26 Al, a rare isotope of aluminum that has a half-life of about 0.71 my. The short half-life mandates that the 26 Al was formed very shortly before the Solar System formed, probably as a result of a nearby supernova.…”

“…(ii) Next followed the discovery (9) of excesses of 26 Mg that formed by the in situ decay of 26 Al, a rare isotope of aluminum that has a half-life of about 0.71 my. The short half-life mandates that the 26 Al was formed very shortly before the Solar System formed, probably as a result of a nearby supernova. Finally, a few CAIs were found to have isotopic anomalies in other elements that are not the result of radioactive decay and must be traces of nucleosynthetic processes within evolved stars that, again, predated formation of our solar system.…”

“…A review by Thiemens (23, 24) discusses some of the major issues, and an entire monograph (25) has been dedicated to oxygen in the Solar System. As discussed in the work by Burnett et al (26), measurements of the oxygen isotopic composition of the solar wind have revealed that more, rather than fewer, issues remain to be addressed in the unraveling of the meteoritic oxygen isotopic record. A recent paper by Krot et al (20) discussed the possible linkage between the oxygen isotopic character of calcium aluminum inclusions and processes by which oxygen isotopes were partitioned between dust and gas in the early Solar System.…”