Leveraging advancements in micro-scale technology, we propose a fleet of autonomous, low-cost, small solar sails for interplanetary exploration. The Berkeley Low-cost Interplanetary Solar Sail (BLISS) project aims to utilize small-scale technologies to create a fleet of tiny interplanetary femto-spacecraft for rapid, low-cost exploration of the inner solar system. This paper describes the hardware required to build a nearly 10 g spacecraft using a 1 m$^2$ solar sail steered by micro-electromechanical systems (MEMS) inchworm actuators. The trajectory control to a NEO, here 101955 Bennu, is detailed along with the low-level actuation control of the solar sail and the specifications of proposed onboard communication and computation. Two other applications are also shortly considered: sample return from dozens of Jupiter-family comets and interstellar comet rendezvous and imaging. The paper concludes by discussing the fundamental scaling limits and future directions for steerable autonomous miniature solar sails with onboard custom computers and sensors.

A literature compilation of 1136 low-Ca pyroxene compositions from chondrules from 12 primitive type 2-3 carbonaceous, ordinary and enstatite chondrite groups define unique regions on an Al2O3 and Cr2O3 diagram when compared to low-Ca pyroxenes from equilibrated type 4-6 chondrites. Measured compositions of 100 low-Ca pyroxenes from comet Wild 2 and a giant cluster IDP of probable cometary origin are similar to each other and fall in the type 2-3 chondrite chondrule region suggesting that most of the pyroxenes likely formed in the solar nebula like conventional chondrules. The data imply that most low Ca-pyroxenes from comet Wild 2 and the giant cluster IDP formed from igneous crystallization processes and did not experience significant thermal metamorphism, indicating that the low-Ca pyroxenes were unlikely incorporated into large parent bodies prior to accretion in their respective comet bodies. An intriguing group of nine low-Ca pyroxenes from comet Wild 2 with low Cr and Al that fall where type 4-6 chondrites are located are interpreted as products of condensation. The compositional data combined with previously measured oxygen isotopes on 17 low-Ca pyroxenes support earlier conclusions that comet samples have links with carbonaceous, ordinary, and possibly enstatite chondrite groups. Our results provide additional evidence that comets accreted materials from multiple chondrule reservoirs throughout the solar nebula.

We measured oxygen isotope ratios of 16 silicate fragments from seven aerogel tracks (turnip-like type B tracks 77, 149, 172, 191, and 220; carrot-like type A tracks 22 and 175) of the comet 81P/Wild 2 collector from NASA’s Stardust mission using secondary ion mass spectrometry. Thirteen were prepared by ultramicrotomy; three from track 220 were prepared by sputtering resin blocks using a SIMS Kohler beam, a new procedure aiming to mine as many cometary particles encased in aerogel/resin as possible. Combining new and literature results, we recognized that most silicate fragments of individual type B tracks have diverse mineralogy but consistent mass-independent fractionation of oxygen isotopes (Δ17O = δ17O − 0.52 × δ18O) or display negative Δ17O–Mg# relationship like CR chondrules. These observations suggest that their impactors are loosely bound aggregates of unequilibrated materials originating mainly from similar protoplanetary disk regions, resembling the cluster IDP U2-20-GCA. Furthermore, silicate fragments from type A track 22 have almost identical mineralogy and Δ17O values, confirming that its impactor is a single chondrule-like fragment. The terminal particle of type A track 175 is pure forsterite with Δ17O of ∼–23‰.Six iron-rich fragments of this study have positive oxygen isotope ratios (Δ17O∼+2‰) and ordinary chondrite chondrule-like olivine compositions. Together with five similar fragments in the literature, a unique population (Mg# ≤86) of Wild 2 fragments that resemble chondrules from the inner solar system (O-E-R) chondrites or the outer solar system CH-CB chondrites was identified. The remaining 16O-poor Wild 2 fragments are Mg# ≥79 silicates with Δ17O∼–2‰ and a small amount of Mg# ≤79 silicates with Δ17O∼0‰, which are most consistent with CR chondrite chondrules. Thus, we conclude that in addition to the possible major source of CR chondrite chondrule-like materials, the inner solar system or CH-CB chondrule-like materials are a minor component of comet Wild 2, like the cluster IDP U2-20-GCA.

Control of oxygen fugacity during high-temperature phase equilibrium experiments is required to simulate the conditions that exist in natural systems. At high pressures, oxygen fugacity may be imposed using solid buffer equilibria via the classic "double capsule " technique. This design becomes untenable, however, at temperatures above the melting points of commonly used noble metal capsule materials and/or where buffer assemblages may alloy with the capsule or contaminate the sample. Here we introduce and test a modified double capsule approach that includes a solid metal-oxide buffer in close proximity to but separate from the sample of interest. Buffers used include (in order of most oxidized to reduced) Ni-NiO, Co-CoO, W-WO3, Fe-FeO, Mo-MoO2, Cr-Cr2O3, V-V2O3, Ta-Ta2O5, and Nb-NbO. At a fixed temperature, these buffers span a wide range-up to 10 log f(O2) units. To demonstrate the buffering capacity of this double capsule approach, secondary redox equilibria and V-doped CaO-MgO-Al2O3-SiO2 system glasses were studied in experiments using the double capsule geometry. The secondary equilibria provide an independent verification of the oxygen fugacity established in the double capsule environment. The glasses proved difficult to interpret, and our results provide guidance to future efforts to utilize the glass oxybarometer at reducing conditions. Application of this modified double capsule technique to studies of V valence in MgAl2O4 spinels led to the recognition of several factors that will affect V valence in this system: temperature of equilibration, duration of experiment, and spinel bulk composition. We have synthesized V-bearing MgAl2O4 spinel at the reduced conditions of the Cr-Cr2O3, (IW-3.51), Ta-Ta2O5, (IW-5.37), and Nb-NbO buffers (IW-5.44). This spinel exhibits a very small V3+ pre-edge peak consistent with its reduced nature. The absence of evidence for V2+ suggests that MgAl2O4 spinel excludes V2+ due to the preference of V for octahedral sites. This finding is supported by DFT calculations for spinels of variable composition, and in agreement with some other indirect evidence for preference for V3+ in aluminous spinels (Bosi et al. 2016,; Paque et al. 2013,).

NASA's Stardust mission utilized a sample collector composed of aerogel and aluminum foil to return cometary and interstellar particles to Earth. Analysis of the aluminum foil begins with locating craters produced by hypervelocity impacts of cometary and interstellar dust. Interstellar dust craters are typically less than one micrometer in size and are sparsely distributed, making them difficult to find. In this paper, we describe a convolutional neural network based on the VGG16 architecture that achieves high specificity and sensitivity in locating impact craters in the Stardust interstellar collector foils. We evaluate its implications for current and future analyses of Stardust samples.

We advocate for the realization of volatile sample return from various destinations including: small bodies, the Moon, Mars, ocean worlds/satellites, and plumes. As part of recent mission studies (e.g., Comet Astrobiology Exploration SAmple Return (CAESAR) and Mars Sample Return), new concepts, technologies, and protocols have been considered for specific environments and cost. Here we provide a plan for volatile sample collection and identify the associated challenges with the environment, transit/storage, Earth re-entry, and curation. Laboratory and theoretical simulations are proposed to verify sample integrity during each mission phase. Sample collection mechanisms are evaluated for a given environment with consideration for alteration. Transport and curation are essential for sample return to maximize the science investment and ensure pristine samples for analysis upon return and after years of preservation. All aspects of a volatile sample return mission are driven by the science motivation: isotope fractionation, noble gases, organics and prebiotic species; plus planetary protection considerations for collection and for the sample. The science value of sample return missions has been clearly demonstrated by previous sample return programs and missions. Sample return of volatile material is key to understanding (exo)planet formation, evolution, and habitability. Returning planetary volatiles poses unique and potentially severe technical challenges. These include preventing changes to samples between (and including) collection and analyses, and meeting planetary protection requirements.

Introduction: X-ray absorption spectra (XAS) of the interstellar medium (ISM) can tell us about what phases are present in the ISM including atomic species, chemical species, and dust. Bright extraterrestrial X-ray sources generate continuum X-ray energy which can be absorbed on its path to Earth orbit where the Chandra (NASA) or XMM-Newton (ESA) Xray telescopes can record the absorption spectrum of several edges. The focus of our recent research has been the Fe-L absorption edge at 710 eV [1]. However, to interpret the spectra, we need to compare them against experimental spectra of sensible phases measured at synchrotron facilities. An issue arises in that many possible interstellar phases (e.g. FeH or Fe2) are difficult to prepare or measure in a terrestrial environment. Therefore, we are using theoretical chemistry to simulate spectra as a complement to our existing synchrotron measurements. What is Observable in ISM Spectra? Interstellar X-ray spectra are noisier and have a lower energy resolution compared to spectra acquired at terrestrial synchrotrons. In addition they can have systematics caused by physics occurring at the X-ray origin (in our case, typically a black-hole/neutron star accretion disk and/or jet). Black hole binary systems generate X-rays from their accretion disks, from a corona of energetic electrons near the disk or at the base of the jet. This can lead to different continuum components, fluorescence lines from ionized atoms, and absorption features. We can use machine learning to select only observations that contain the minimum confounding factors [2], but even then we should expect a spectrum with an energy resolution of ≥ 1 eV, considering uncertainty caused by noise in the signal. With this in mind, we are interested in simulating primarily the positions of the Fe-L3 peak, the Fe-L2 peak, and the amplitude ratio between the two (branching ratio). As our models gain sophistication, we may evolve to consider factors such as peak width or skew. Our present work has indicated that the ISM spectra are closest to Fe metal but differ in two important ways. 1) The Fe-L edge seems to be shifted to lower energies than expected for Fe metal. 2) The intensity of the Fe-L3 line is weaker than expected for typical Fe-L branching ratios. These factors are a current focus of our investigation. We present more detail on this in a sister abstract [3]. Methods: We want to simulate a range of phases including atomic Fe, simple Fe-bearing molecules (e.g. FeH), larger species such as polycyclic aromatic hydrocarbons (PAHs) containing Fe, Fe clusters (e.g. Fe2) and other species. Exact quantum mechanical approaches such as multiplet theory become computationally intractable for large molecules and nanoparticles. As such, we are willing to sacrifice some spectral quality for speed so long as the resulting spectra still contain the information necessary to discriminate phases in the ISM. We use Density Functional Theory (DFT) to obtain the ground state electronic structure of each phase, and then we Figure 1: Experimental Fe(CO)5(g) spectrum taken from [11] compared to a theoretical spectrum computed using DFT/ROCIS (see text). The L3:L2 branching ratio of the theoretical spectrum is 1.7 whereas the L3:L2 branching ratio of the experimental spectrum is 1.8. Note that the theoretical spectrum has been convolved with a 0.5 eV gaussian, and dual sigmoids were removed from the experimental spectrum before integrating the peak areas.

BY CONVOLUTIONAL NEURAL NETWORKS. Logan Jaeger, Anna L. Butterworth, Zack Gainsforth, Robert Lettieri, Augusto Ardizzone, Michael Capraro, Mark Burchell, Penny J. Wozniakiewicz, Ryan C. Ogliore, Bradley T. De Gregorio, Rhonda M. Stroud, Andrew J. Westphal , Space Sciences Laboratory, University of California, Berkeley, CA 94720, Centre for Astrophysics and Planetary Science, University of Kent, Canterbury CT2 7NH, UK, Washington University, St. Louis, MO, 63130, Materials Science and Technology Division, Code 6366, US Naval Research Laboratory, Washington, DC 20375 .

Introduction: Comparison of the initial chemistry of the solar nebula with the chemical diversity that we observe today in the solar system in principle can inform our understanding of chemical processing in the early solar system. Previously, we measured the oxidation state of Fe in the interstellar medium [1], using Chandra x-ray observations of the bright x-ray source Cyg X-1, combined with a library of Fe L-edge spectra of standards acquired by synchrotron-based soft x-ray spectroscopy at the Advanced Light Source (Lawrence Berkeley National Laboratory). Extinction spectra, observed astronomically, cannot be compared directly to absorption spectra measured in the laboratory, so theoretical extinction spectra were derived from absorption spectra via the KramersKronig relation and various assumptions about particle size distribution (e.g., [2]). We concluded that the observations are most consistent with Fe dominated by Fe metal. Having developed the technique, we are now expanding the effort to survey the oxidation state of Fe in the ISM along lines of sight to numerous x-ray binaries, which serve as quasi-continuum light sources, and to expand our effort to observations by XMM-Newton. XMM has a larger collecting power than Chandra, but poorer energy resolution. Here we present a highstatistics XMM observation of Cyg X-1 to compare to the Chandra observation along the same line of sight, and to explore the adequacy of our standards library to fit high-statistics data. Methods: We combined multiple spectra of Cyg X-1 taken by the Reflection Grating Spectrometer (RGS) on the XMM-Newton space telescope. We downloaded all fluxed spectra for Cyg X-1 from the XMM-Newton Science Archive but removed observations that have significant contamination from undesirable x-ray phenomena such as overlapping fluorescence lines [4]. We also calculated the orbital phase of the black hole relative to the companion star and chose only those spectra that did not place the black hole in the shadow of the star’s atmosphere since we are interested in the composition of the ISM, not the stellar wind. Analyses: We fit the spectrum using the same technique and code that we used for analysis of Chandra data reported in [1]. We did not include any assumed gas component in the analysis. We first fit the observations to a combination of metal, sulfide and silicate standards (Fig. 1), as in the Chandra analysis. The best fit was consistent with metal composition (Fig. 2). This conclusion is similar to our previous 600 620 640 660 680 700 720 740 760 780 800 energy (eV) 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

ABSTRACT We assess whether chondrules, once-molten mm-sized spheres filling the oldest meteorites, could have formed from super-km s−1 collisions between planetesimals in the solar nebula. High-velocity collisions release hot and dense clouds of silicate vapour which entrain and heat chondrule precursors. Thermal histories of CB chondrules are reproduced for colliding bodies ∼10–100 km in radius. The slower cooling rates of non-CB, porphyritic chondrules point to colliders with radii ≳ 500 km. How chondrules, collisionally dispersed into the nebula, agglomerated into meteorite parent bodies remains a mystery. The same orbital eccentricities and inclinations that enable energetic collisions prevent planetesimals from re-accreting chondrules efficiently and without damage; thus the sedimentary laminations of the CB/CH chondrite Isheyevo are hard to explain by direct fallback of collisional ejecta. At the same time, planetesimal surfaces may be littered with the shattered remains of chondrules. The micron-sized igneous particles recovered from comet 81P/Wild-2 may have originated from in-situ collisions and subsequent accretion in the proto-Kuiper belt, obviating the need to transport igneous solids across the nebula. Asteroid sample returns from Hayabusa2 and OSIRIS-REx may similarly contain chondrule fragments.

Interplanetary and interstellar dust as windows into solar system origins and evolution.1We can explore in situ the building blocks of the planets by measuring the trajectories and compositions of thousands of dust particles from comets and our interstellar neighborhood, a f e f d .

The NASA Stardust Interstellar Dust collection provides our current best sample set for direct laboratory analysis of dust grains from the contemporary interstellar dust stream. While a handful of likely interstellar dust grains were identified within the silica aerogel collection media, interstellar dust also impacted Al foils covering the collector frame. Locating these rare impacts requires labor‐intensive collection and examination of tens of thousands of high‐resolution SEM images. Here, we implement a Python‐based algorithm to dramatically reduce the human time investment needed to locate impact craters. The algorithm employs a circular Hough transform to identify circular features in the foil images, followed by several tests to detect characteristic morphological features of impact craters—a dark center and a bright rim, with inclusion of multi‐core processing capabilities to significantly increase processing speed. For most data sets, the code produced a pool of potential crater candidates in 1–5% of the input images, producing a more manageable subset of images for a human expert to review. We used this code to locate 31 impact craters across 12 Stardust interstellar foils, 25 of which were located on three adjacent foils, I1008W,1, I1009N,1, and I1020W,1. Many impacts on these foils formed shallow, oblique craters, with residue compositions consistent with solar cell glass and orientations consistent with debris ejected from the spacecraft solar cells. The code can be integrated into future searches for Stardust interstellar grain impacts and can be implemented as a general utility for dust impact studies on spacecraft materials.

Existing cell phone technology and recent advances in microelectromechanical systems (MEMS) enable unprecedented capabilities in space.Fleets of thousands of tiny interplanetary spacecraft, navigating using solar sails, will soon enable rapid exploration of the inner Solar System.Return of pristine cometary material is a high NASA priority, as reflected in the Phase A selections from the most recent New Frontiers competition.Here, we describe a mission architecture using miniature interplanetary spacecraft that could rapidly return pristine cometary material from dozens of Jupiter Family Comets (JFCs) at a fraction of the cost of a sample return mission from a single JFC using a more traditional approach.Each spacecraft would weigh approximately ten grams, and would navigate using a solar sail.All of the components of such miniaturized spacecraft have been demonstrated in the laboratory or in commercial applications, but will require investment to qualify for space applications. Importance of pristine cometary sample returnComets contain the building blocks of the solar system, preserved in deep freeze for 4.568 billion years.Study of cometary samples returned by the Stardust mission and collected in the stratosphere has demonstrated that the earliest history of the Solar System is recorded in these tiny samples.In 2006, the NASA Stardust spacecraft returned the first cometary samples to terrestrial laboratories, resulting in > 140 publications and the rewriting our understanding of the earliest history of the solar system.However, neither of the existing collections of cometary materials are pristine, but were modified by the collection methodcapture at 6.1 km/sec in aerogel and Al foil collectors in the case of Stardust, and atmospheric entry at ∼10 km/sec in the case of the stratospheric collection.In particular, the organics and the finest-grained materials, either did not survive or were severely altered.As a result, critically important pieces of the puzzle are missing.Cometary organics are thermally fragile and as a result are poorly understood.The delivery of organics to the prebiotic Earth may have played a key role in making it habitable and in the origin of life [1,2,3].Increasingly sophisticated laboratory techniques, largely enabled by high-resolution synchrotron infrared and soft x-ray microprobes, will enable detailed analysis of organics within their petrographic contexts.BLISS spacecraft could be used to return unaltered organics and fine-grained materials in coma dust samples from dozens of comets, by collecting the samples at m/sec capture speeds, rather than km/sec speeds.Sample return of pristine cometary material was identified as a high priority in the most recent Planetary Decadal Survey, and a comet sample return mission -from a single comet -

Gainsforth, K. Iacovino, T. Erickson, C. E. Jilly-Rehak, R. Rowland, S. Fakra, A.J. Westphal ; Mailcode XI2, NASA Johnson Space Center, Houston, TX 77058; kevin.righter-1@nasa.gov. Space Sciences Laboratory, University of California Berkeley, Berkeley, CA 94720. Jacobs-JETS, ARES NASA Johnson Space Center, 2101 NASA Pkwy., Houston, TX 77058; Dept. of Geological Sciences, Stanford University, Stanford CA 94305; Los Alamos National Laboratory, Mail Stop P952, Los Alamos, NM 87545; Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720,