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Lauretta, D. S.

Publications and source records attributed to Lauretta, D. S..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Episodes of Particle Ejection from the Surface of the Active Asteroid (101955) Bennu

Active asteroids are those that show evidence of ongoing mass loss. We report repeated instances of particle ejection from the surface of (101955) Bennu, demonstrating that it is an active asteroid. The ejection events were imaged by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) spacecraft. For the three largest observed events, we estimated the ejected particle velocities and sizes, event times, source regions, and energies. We also determined the trajectories and photometric properties of several gravitationally bound particles that orbited temporarily in the Bennu environment. We consider multiple hypotheses for the mechanisms that lead to particle ejection for the largest events, including rotational disruption, electrostatic lofting, ice sublimation, phyllosilicate dehydration, meteoroid impacts, thermal stress fracturing, and secondary impacts.

Lauretta, D. S.↗
NASA NTRS2019

Overview of the Search for Space Weathering Signals on Bennu: One Rock Type, or Two?

We report on progress in the search for signs of space weathering on Bennu. We provide an overview of the space weathering evidence to date, and summarize relevant findings from several ongoing parallel studies of surface processes and surface properties. We examine trends from these studies in the context of space weathering, and what is known about near-Earth asteroid surface maturation. Because Bennu is covered with blocks, boulders, and rocks of various sizes, our search for space weathering signals has inevitably led to a study of the properties of Bennu’s rocks. Our research question is – do Bennu’s bright and dark rock populations form a maturity continuum due to space weathering, or alternatively, do the bright and dark rocks provide compelling evidence for two distinct rock populations on Bennu? In particular, we present our best estimate of the sub-field-of-view OVIRS (OSIRIS-REx Visible and Infrared Spectrometer) spectral properties of the largest bright boulders and compare them with the darker materials on Bennu’s surface to see if the observed spectral and albedo differences are consistent with space weathering effects, or not.

Clark, B. E.↗
NASA NTRS2019

Space Weathering Maps of (101955) Bennu Using a Radiative Transfer Model

Space weathering is an important process that affects the surfaces of airless bodies, such as (101955) Bennu. The consequences of this process include physical and chemical changes to materials on the surface, which in turn change spectral characteristics, especially in the visible to near infrared wavelengths. These spectral changes are not the same across airless bodies because the changes are dependent on the composition and mineralogy of the surface and even location within the Solar System. The main space weathering products responsible for these spectral changes are submicroscopic particles, which consist of two types, nanophase and microphase particles, and affect visible to near-infrared reflectance spectra differently. Nanophase particles are particles <33 nm in size and occur in agglutinates and within glassy patinas around regolith particles. In contrast, microphase particles are >33 nm in size and are present only within agglutinates. These spectral differences are best illustrated by lunar samples. In lunar soils, the nanophase and microphase particles consist of metallic iron. With increasing abundance of nanophase iron particles in a regolith, its spectrum exhibits a lower overall reflectance in the visible to near infrared, weakened absorption bands, and a reddened continuum slope. In contrast, an increasing abundance of microphase iron only causes decreases in reflectance and not reddening. Because of the spectral differences introduced by these two types of particles, it is possible to model the nanophase and microphase particle abundances of a surface through the radiative transfer technique. Beyond the Moon, the composition of the nanophase and microphase particles can include other phases because the mineralogy of the surfaces of other planetary bodies is different. For example, the nanophase and microphase particles may consist of amorphous carbon (Mercury) and sulfides (Itokawa). The mineralogy of Bennu is consistent with carbonaceous chondrites. From a number of space weathering experiments on CM chondrites, the likely nanophase and microphase mineral phases on Bennu includes iron, magnetite, and sulfides (i.e., pentlandite and troilite). The goal of this work is to input the predicted nanophase and microphase compositions for Bennu into the radiative transfer technique. Next, we use this technique to model the OSIRIS-REx Visible Infrared Spectrometer (OVIRS) so that we can model the nanophase and microphase particle abundances across the surface. This will result in space weathering maps of the surface of Bennu, which are useful for understanding the degree of space weathering across the surface and its relationship to various regions and geological features.

Trang, D.↗
NASA NTRS2019

OSIRIS-REx Gravity Field Estimates for Bennu Using Spacecraft and Natural Particle Tracking Data

The current best estimates of Bennu’s gravity field will be presented, based on the independent solutions from four different teams involved on the OSIRIS-REx mission. The discovery of ejected particles about Bennu that may remain in orbit for several days or more provide a unique opportunity to probe the gravity field to higher degree and order than possible by using conventional spacecraft tracking. However, the non-gravitational forces acting on these particles must also be characterized, and their impact on solution accuracy must be assessed. This talk will present the latest results from the mission, incorporating spacecraft tracking from the lowest orbit in which the satellite will be during the mission.

Scheeres, D. J.↗
NASA NTRS2019

OSIRIS‐REx Visible and Near‐Infrared Observations of the Moon

The Origins, Spectral Interpretation, Resource Identification, and Security Regolith Explorer(OSIRISREx) mission observed the The Origins, Spectral Interpretation, Resource Identification, and Security‐Regolith Explorer (OSIRIS‐REx) mission observed the Moon during the spacecraft's Earth gravity assist in 2017. From the spacecraft view, the lunar phase was 42°, and the in‐view hemisphere was dominated by anorthositic highlands terrain. Lunar spectra obtained by the OSIRIS‐REx Visible and InfraRed Spectrometer show evidence of several candidate absorption features. We observe the 2.8‐μm hydration band, confirming the spectral results from other missions, but detected in full‐disk spectra. We also tentatively identify weak spectral features near 0.9 and 1.3 μm, consistent with lunar regolith containing a mixture of plagioclase and orthopyroxene minerals, as expected for highlands terrain.

Simon, A. A.↗
NASA NTRS2019

Craters, Boulders and Regolith of (101955) Bennu Indicative of an Old and Dynamic Surface

Small, kilometre-sized near-Earth asteroids are expected to have young and frequently refreshed surfaces for two reasons: collisional disruptions are frequent in the main asteroid belt where they originate, and thermal or tidal processes act on them once they become near-Earth asteroids. Here we present early measurements of numerous large candidate impact craters on near-Earth asteroid (101955) Bennu by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security- Regolith Explorer) mission, which indicate a surface that is between 100 million and 1 billion years old, predating Bennu's expected duration as a near-Earth asteroid. We also observe many fractured boulders, the morphology of which suggests an influence of impact or thermal processes over a considerable amount of time since the boulders were exposed at the surface. However, the surface also shows signs of more recent mass movement: clusters of boulders at topographic lows, a deficiency of small craters and infill of large craters. The oldest features likely record events from Bennu's time in the main asteroid belt.

near-Earth asteroids; Bennu; OSIRIS-REx↗
NASA NTRS2019

Properties of Rubble-Pile Asteroid (101955) Bennu from OSIRIS-REx Imaging and Thermal Analysis

Establishing the abundance and physical properties of regolith and boulders on asteroids is crucial for understanding the formation and degradation mechanisms at work on their surfaces. Using images and thermal data from NASA's Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft, we show that asteroid (101955) Bennu's surface is globally rough, dense with boulders, and low in albedo. The number of boulders is surprising given Bennu's moderate thermal inertia, suggesting that simple models linking thermal inertia to particle size do not adequately capture the complexity relating these properties. At the same time, we find evidence for a wide range of particle sizes with distinct albedo characteristics. Our findings imply that ages of Bennu's surface particles span from the disruption of the asteroid's parent body (boulders) to recent in situ production (micrometre-scale particles).

DellaGiustina, D. N.↗
NASA NTRS2019

The CAESAR New Frontiers Mission: 1. Expected Nature of the Returned Comet Sample

Comets are time capsules from the birth of our Solar System that record pre-solar history, the initial stages of planet formation, and the sources of prebiotic organics and volatiles for the origin of life. These capsules can only be opened in laboratories on Earth. CAESAR (Comet Astrobiology Exploration Sample Return)’s sample analysis objectives are to understand the nature of Solar System starting materials and how these components came together to form planets and give rise to life. Examination of these comet nucleus surface samples in laboratories around the world will also provide ground truth to remote observations of the innumerable icy bodies of the Solar System.

Lauretta, D. S.↗
NASA NTRS2019

A Preliminary Look at Space Weathering on 101955 Bennu: A Radiative Tranfer Modeling Perspective

The surfaces of airless bodies, such as 101955 Bennu, are vulnerable to micrometeoroids, high-energy particles, and solar wind particles. As a result, material on the surface of these bodies experience physical and chemical changes that are collectively known as space weathering. Space weathering processes result in the production of sub-micronsized particles called submicroscopic particles. There are two types of submicroscopic particles, nanophase (<33 nm in size) and microphase particles (>33 nm in size). Studies of lunar samples show that nanophase particles occur within the glassy rims that surround grains and agglutinates. In contrast, microphase iron particles occur only within agglutinates. Another important difference between these two particles is that nanophase and microphase particles affect visible to near-infrared reflectance spectra differently. From lunar samples, the presence of nanophase particles in a regolith causes the regolith’s reflectance spectrum to darken and redden, whereas the presence of microphase particles in a regolith causes it to only darken. In addition, the reflectance spectra of submicroscopic particle-bearing regolith exhibit weakened absorptions and spectral features. Lantz et al. (2018) found that these particles also affect spectral curvature [8]. By taking advantage of these spectral characteristics, with global spectral data, it is possible to model the nanophase and microphase particle abundances across a planetary surface resulting in the production of global space weathering maps.

Trang, D.↗
NASA NTRS2019

Deviation of the Shape of Bennu from Rotational Figures of Stability

Images of asteroid (101955) Bennu acquired by the OSIRIS-­REx mission reveal a rocky world covered in rubble; Shape deviates from hydrostatic surface; Internal friction and/or cohesion even if no tensile strength; Understanding the deviation of the surface from idealized shape may help constrain mechanical properties of the interior; Geologic evolution of Bennu is driven by downslope migration of surface material and rubble; May be caused by YORP-induced spin-up, re-­accumulation, impact-induced seismic shaking, thermal stresses, or tidal disruption by close encounters to larger bodies.

Roberts, J. H.↗
NASA NTRS2018

The OSIRIS-REx Spacecraft and the Touch-and-Go Sample Acquisition Mechanism (TAGSAM)

The Origins, Spectral-Interpretation, Resource-Identification, Security and Regolith- Explorer (OSIRIS-REx) spacecraft supports all aspects of the mission science objectives, from extensive remote sensing at the asteroid Bennu, to sample collection and return to Earth. In general, the success of planetary missions requires the collection, return, and analysis of data, which in turn depends on the successful operation of instruments and the host spacecraft. In the case of OSIRIS-REx, a sample-return mission, the spacecraft must also support the acquisition, safe stowage, and return of the sample. The target asteroid is Bennu, a B-class near-Earth asteroid roughly 500 m diameter. The Lockheed Martin-designed and developed OSIRIS-REx spacecraft draws significant heritage from previous missions and features the Touch-and-Go-Sample-Acquisition-Mechanism, or TAGSAM, to collect sample from the surface of Bennu. Lockheed Martin developed TAGSAM as a novel, simple way to collect samples on planetary bodies. During short contact with the asteroid surface, TAGSAM releases curation-grade nitrogen gas, mobilizing the surface regolith into a collection chamber. The contact surface of TAGSAM includes "contact pads", which are present to collect surface grains that have been subject to space weathering. Extensive 1-g laboratory testing, "reduced-gravity" testing (via parabolic flights on an airplane), and analysis demonstrate that TAGSAM will collect asteroid material in nominal conditions, and a variety of off-nominal conditions, such as the presence of large obstacles under the TAGSAM sampling head, or failure in the sampling gas firing. TAGSAM, and the spacecraft support of the instruments, are central to the success of the mission.

Spacecraft↗
NASA NTRS2018

The CAESAR New Frontiers Mission: Comet Surface Sample Acquisition and Preservation

NASA recently selected the Comet Astrobiology Exploration Sample Return (CAESAR) mission for Phase A study in the New Frontiers Program. This mission will acquire and return to Earth for laboratory analysis at least 80 g of surface material from the nucleus of comet 67P/Churyumov-Gerasimenko (hereafter 67P). CAESAR will characterize the surface region sampled, preserve the sample in a pristine state, and return evolved volatiles by capturing them in a separate gas reservoir. The system protects both volatile and non-volatile components from contamination or alteration thatwould hamper their scientific analysis. Laboratory analyses of comet samples provide unparalleled knowledge about the presolar history through the initial stages of planet formation to the origin of life.

CAESAR↗
NASA NTRS2018

The OSIRIS-REx Visible and InfraRed Spectrometer (OVIRS): Spectral Maps of the Asteroid Bennu

The OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) is a point spectrometer covering the spectral range of 0.4 to 4.3 microns (25,000-2300 cm−1). Its primary purpose is to map the surface composition of the asteroid Bennu, the target asteroid of the OSIRIS-REx asteroid sample return mission. The information it returns will help guide the selection of the sample site. It will also provide global context for the sample and high spatial resolution spectra that can be related to spatially unresolved terrestrial observations of asteroids. It is a compact, low-mass (17.8 kg), power efficient (8.8 W average), and robust instrument with the sensitivity needed to detect a 5% spectral absorption feature on a very dark surface (3% reflectance) in the inner solar system (0.89-1.35 AU). It, in combination with the other instruments on the OSIRIS-REx Mission, will provide an unprecedented view of an asteroid's surface.

Reuter, D. C.↗
NASA NTRS2017

OSIRIS-REx Contamination Control Strategy and Implementation

OSIRIS-REx will return pristine samples of carbonaceous asteroid Bennu. This article describes how pristine was defined based on expectations of Bennu and on a realistic understanding of what is achievable with a constrained schedule and budget, and how that definition flowed to requirements and implementation. To return a pristine sample, the OSIRIS-REx spacecraft sampling hardware was maintained at level 100 A/2 and less than 180 ng/cm(exp 2) of amino acids and hydrazine on the sampler head through precision cleaning, control of materials, and vigilance. Contamination is further characterized via witness material exposed to the spacecraft assembly and testing environment as well as in space. This characterization provided knowledge of the expected background and will be used in conjunction with archived spacecraft components for comparison with the samples when they are delivered to Earth for analysis. Most of all, the cleanliness of the OSIRIS-REx spacecraft was achieved through communication among scientists, engineers, managers, and technicians.

OSIRIS-RE↗
NASA NTRS2017

OSIRIS-REx Contamination Control Strategy and Implementation

OSIRIS-REx will return pristine samples of carbonaceous asteroid Bennu. This manuscript describes how pristine was defined based on expectations of Bennu and on a realistic understanding of what is achievable with a constrained schedule and budget, and how that definition flowed to requirements and implementation. To return a pristine sample, the OSIRIS-REx spacecraft sampling hardware was maintained at Level 100 A/2 and less than 180 nanograms per square centimeter of amino acids and hydrazine on the sampler head through precision cleaning, control of materials, and vigilance. Contamination is further characterized via witness material exposed to the spacecraft assembly and testing environment as well as in space. This characterization provided knowledge of the expected background and will be used in conjunction with archived spacecraft components for comparison with the samples when they are delivered to Earth for analysis. Most of all, the cleanliness of the OSIRIS-REx spacecraft was achieved through communication between scientists, engineers, managers, and technicians.

Dworkin, J. P.↗
NASA NTRS2017

Spectral Characterization of Analog Samples in Anticipation of OSIRIS-REx's Arrival at Bennu

NASA's Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission successfully launched on September 8th, 2016. During its rendezvous with near-Earth asteroid (101955) Bennu beginning in 2018, OSIRIS-REx will characterize the asteroid's physical, mineralogical, and chemical properties in an effort to globally map the properties of Bennu, a primitive carbonaceous asteroid, and choose a sampling location]. In preparation for these observations, analog samples were spectrally characterized across visible, near- and thermal-infrared wavelengths and were used in initial tests on mineral-phase-detection and abundance-determination software algorithms.

Donaldson Hanna, K. L.↗
NASA NTRS2017

Lessons Learned from Preparing OSIRIS-REx Spectral Analog Samples for Bennu

NASA's OSIRIS-REx sample return mission launched on September 8th, 2016 to rendezvous with B-type asteroid (101955) Bennu in 2018. Type C and B asteroids have been linked to carbonaceous chondrites because of their similar visible - to - near infrared (VIS-NIR) spectral properties [e.g., 1,2]. The OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) and the Thermal Emission Spectrometer (OTES) will make spectroscopic observations of Bennu during the encounter. Constraining the presence or absence of hydrous minerals (e.g., Ca-carbonate, phyllosilicates) and organic molecules will be key to characterizing Bennu [3] prior to sample site selection. The goal of this study was to develop a suite of analog and meteorite samples and obtain their spectral properties over the wavelength ranges of OVIRS (0.4- 4.3 micrometer) and OTES (5.0-50 micrometer). These spectral data were used to validate the mission science-data processing system. We discuss the reasoning behind the study and share lessons learned.

Schrader, D. L.↗