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NASA NTRS2016

Strata-1: An International Space Station Experiment into Fundamental Regolith Processes in Microgravity

The Strata-1 experiment will study the evolution of asteroidal regolith through long-duration exposure of simulant materials to the microgravity environment on the International Space Station (ISS). Many asteroids feature low bulk densities, which implies high values of porosity and a mechanical structure composed of loosely bound particles, (i.e. the "rubble pile" model), a prime example of a granular medium. Even the higher-density, mechanically coherent asteroids feature a significant surface layer of loose regolith. These bodies are subjected to a variety of forces and will evolve in response to very small perturbations such as micrometeoroid impacts, planetary flybys, and the YORP effect. Our understanding of this dynamical evolution and the inter-particle forces involved would benefit from long-term observations of granular materials exposed to small vibrations in microgravity. A detailed understanding of asteroid mechanical evolution is needed in order to predict the surface characteristics of as-of-yet unvisited bodies, to understand the larger context of samples collected by missions such as OSIRIS-REx and Hayabusa 1 and 2, and to mitigate risks for both manned and unmanned missions to asteroidal bodies. Understanding regolith dynamics will inform designs of how to land and set anchors, safely sample/move material on asteroidal surfaces, process large volumes of material for in situ resource utilization (ISRU) purposes, and, in general, predict behavior of large and small particles on disturbed asteroid surfaces.

Fries, M.↗
NASA NTRS2014

Investigating the Geological History of Asteroid 101955 Bennu Through Remote Sensing and Returned Sample Analyses

The NASA New Frontiers Mission OSRIS-REx will return surface regolith samples from near-Earth asteroid 101955 Bennu in September 2023. This target is classified as a B-type asteroid and is spectrally similar to CI and CM chondrite meteorites [1]. The returned samples are thus expected to contain primitive ancient Solar System materials that formed in planetary, nebular, interstellar, and circumstellar environments. Laboratory studies of primitive astromaterials have yielded detailed constraints on the origins, properties, and evolutionary histories of a wide range of Solar System bodies. Yet, the parent bodies of meteorites and cosmic dust are generally unknown, genetic and evolutionary relationships among asteroids and comets are unsettled, and links between laboratory and remote observations remain tenuous. The OSIRIS-REx mission will offer the opportunity to coordinate detailed laboratory analyses of asteroidal materials with known and well characterized geological context from which the samples originated. A primary goal of the OSIRIS-REx mission will be to provide detailed constraints on the origin and geological and dynamical history of Bennu through coordinated analytical studies of the returned samples. These microanalytical studies will be placed in geological context through an extensive orbital remote sensing campaign that will characterize the global geological features and chemical diversity of Bennu. The first views of the asteroid surface and of the returned samples will undoubtedly bring remarkable surprises. However, a wealth of laboratory studies of meteorites and spacecraft encounters with primitive bodies provides a useful framework to formulate priority scientific questions and effective analytical approaches well before the samples are returned. Here we summarize our approach to unraveling the geological history of Bennu through returned sample analyses.

Messenger, S.↗
NASA NTRS2004

Photon momentum transfer plane for asteroid, meteoroid, and comet orbit shaping

A spacecraft docks with a spinning and/or rotating asteroid, meteoroid, comet, or other space object, utilizing a tether shaped in a loop and utilizing subvehicles appropriately to control loop instabilities. The loop is positioned about a portion of the asteroid and retracted thereby docking the spacecraft to the asteroid, meteoroid, comet, or other space object. A deployable rigidized, photon momentum transfer plane of sufficient thickness may then be inflated and filled with foam. This plane has a reflective surface that assists in generating a larger momentum from impinging photons. This plane may also be moved relative to the spacecraft to alter the forces acting on it, and thus on the asteroid, meteoroid, comet, or other space object to which it is attached. In general, these forces may be utilized, over time, to alter the orbits of asteroids, meteoroids, comets, or other space objects. Sensors and communication equipment may be utilized to allow remote operation of the rigidized, photon momentum transfer plane and tether.

Campbell, Jonathan W.↗
NASA NTRS2016

The Strata-1 Regolith Dynamics Experiment: Class 1E Science on ISS

The Strata-1 experiment studies the evolution of small body regolith through long-duration exposure of simulant materials to the microgravity environment on the International Space Station (ISS). This study will record segregation and mechanical dynamics of regolith simulants in a microgravity and vibration environment similar to that experienced by regolith on small Solar System bodies. Strata-1 will help us understand regolith dynamics and will inform design and procedures for landing and setting anchors, safely sampling and moving material on asteroidal surfaces, processing large volumes of material for in situ resource utilization (ISRU) purposes, and, in general, predicting the behavior of large and small particles on disturbed asteroid surfaces. This experiment is providing new insights into small body surface evolution.

Fries, Marc↗
NASA NTRS2000

Stratospheric Sampling and In Situ Atmospheric Chemical Element Analysis During Meteor Showers: A Resource Study

Resources studies for asteroidal mining evaluation have depended historically on remote sensing analysis for chemical elements. During the November 1998 Leonids meteor shower, a stratospheric balloon and various low-density capture media were used to sample fragments from Comet Tempel-Tuttle debris during a peak Earth crossing. The analysis not only demonstrates how potential sampling strategies may improve the projections for metals or rare elements in astromining, but also benchmarks materials during low temperature (-60 F), high dessication environments as seen during atmospheric exposure. The results indicate high aluminum, magnesium and iron content for various sampled particles recovered, but generalization to the sporadic meteors expected from asteroidal sources will require future improvements in larger sampling volumes before a broad-use strategy for chemical analysis can be described. A repeat of the experimental procedure is planned for the November 1999 Leonids' shower, and various improvements for atmospheric sampling will be discussed.

Noever, David A.↗
NASA NTRS1999

The Number of Kilometer-Sized Near-Earth Asteroids

In recent years, astronomers have focused their attention upon the near-Earth asteroids (NEAs), which are small (less than 10km), generally rocky solar-system bodies with orbits approaching Earth.

ateroids NEA NEO Near-Earth asteroid↗
NASA NTRS1982

A bibliography of planetary geology principal investigators and their associates, 1981 - 1982

Over 800 publications submitted by researchers supported through NASA's Planetary Geology Program are cited and an author/editor index is provided. Entries are listed under the following subjects: (1) general interest topics; (2) solar system, comets, asteroids, and small bodies; (3) geologic mapping, geomorphology, and stratigraphy; (4) structure, tectonics, geologic and geophysical evolution; (5) impact craters: morphology, density, and geologic studies; (6) volcanism; (7) fluvial, mass wasting, and periglacial processes; (8) Eolian studies; (9) regolith, volatile, atmosphere, and climate; (10) remote sensing, radar, and photometry; and (11) cartography, photogrammetry, geodesy, and altimetry.

Plescia, J. B.↗
NASA NTRS1994

The origin and role of dust in the early solar system

Dust was the primary building material of the solar nebula planetesimals that accumulated to form minor planets, solid planets, and the cores of giant planets. Collected interplanetary dust particle (IDP) samples probably contain preserved samples of nebular dust that formed over a wide range of radial distance. There are two general source regions of IDP's, the asteroid belt and the short-period comets. The collected asteroid particles are likely to be rather representative samples of material that accreted into planetesimals in the 2.2 to 3.3 AU region. The comet samples are likely to be representative samples of grains that accreted in the Kuiper belt region between 20 AU and some hundreds of AU. Many of the solar system effects on grains should have been more pronounced or even restricted to the less than 5 AU region where the asteroids were formed. A major goal of IDP research is to try to identify typical asteroidal and cometary IDP's and to study their properties. If successful this will provide fundamental insight into both the initial solids in the solar nebula and materials modified by a variety of important nebular processes.

Brownlee, Don E.↗
NASA NTRS2024

Tarda and Tagish Lake: Samples From The Same Outer Solar System Asteroid and Implications for D- and P-Type Asteroids

We report a comprehensive study of the ungrouped type 2 carbonaceous chondrite, Tarda, which fell in Morocco in 2020. This meteorite exhibits substantial similarities to Tagish Lake, Wisconsin Range 91600, and Meteorite Hills 00432, which are generally considered to have originated from a D-type asteroid(s). We constrain the compositions and petrologies of the materials present in a potential sample of a D-type asteroid by reporting the petrography, bulk chemical compositions, bulk H, C, N, Cr, and Ti isotopic compositions, reflectance spectra, and in situ chemical compositions of metals, sulfides, carbonates, and FeO-poor and FeO-rich chondrule silicates of Tarda. We also present new data for Tagish Lake. We then compare Tarda with the other Tagish Lake-like meteorites. Tarda and Tagish Lake appear to be from the same parent body, as demonstrated by their similar petrologies (modal abundances, chondrule sizes), mineral compositions, bulk chemical and isotopic compositions, and reflectance spectra. While the two other Tagish Lake-like meteorites, Wisconsin Range 91600 and Meteorite Hills 00432, show some affinities to Tagish Lake and Tarda, they also share similar characteristics to the Mighei-like carbonaceous (CM) chondrites, warranting further study. Similarities in reflectance spectra suggest that P-type asteroids 65 Cybele and 76 Freia are potential parent bodies of Tarda and the Tagish Lake-like meteorites, or at least have similar surface materials. Since upcoming spacecraft missions will spectrally survey D-type, P-type, and C-type Trojan asteroids (NASA's Lucy) and spectrally study and return samples from Mars' moon Phobos (JAXA's Martian Moons eXploration mission), which is spectrally similar to D-type asteroids, these meteorites are of substantial scientific interest. Furthermore, since Tarda closely spectrally matches P-type asteroids (but compositionally matches the D-type asteroid like Tagish Lake meteorite), P-type and D-type asteroids may represent fragments of the same or similar parent bodies.

Tarda↗
NASA NTRS1989

Global environmental effects of impact-generated aerosols: Results from a general circulation model

Interception of sunlight by the high altitude worldwide dust cloud generated by impact of a large asteroid or comet would lead to substantial land surface cooling, according to the three-dimensional atmospheric general circulation model (GCM). This result is qualitatively similar to conclusions drawn from an earlier study that employed a one-dimensional atmospheric model, but in the GCM simulation the heat capacity of the oceans, not included in the one-dimensional model, substantially mitigates land surface cooling. On the other hand, the low heat capacity of the GCM's land surface allows temperatures to drop more rapidly in the initial stages of cooling than in the one-dimensional model study. GCM-simulated climatic changes in the scenario of asteroid/comet winter are more severe than in nuclear winter because the assumed aerosol amount is large enough to intercept all sunlight falling on earth. Impacts of smaller objects could also lead to dramatic, though of course less severe, climatic changes, according to the GCM. An asteroid or comet impact would not lead to anything approaching complete global freezing, but quite reasonable to assume that impacts would dramatically alter the climate in at least a patchy sense.

Covey, Curt↗
NASA NTRS2004

Identifying the Parent Body of the Tagish Lake Meteorite and Characterizing its Internal Heating History and Surface Processes

This short (1-year) funded research encompassed laboratory measurements of the Tagish Lake meteorite samples, experiments of simulated space weathering on them, and comparison with D, T, and P asteroids in reflectance spectrum. In spite of its limited funding and period, we have performed said experiments here at Brown University and at University of Tokyo. Some of the major results were reported at the Lunar and Planetary Science Conference held in Houston in March, 2004. The Tagish Lake meteorite shows a unique visible reflectance spectrum identical to that of the D and T type asteroids. After the present heating experiments at even the lowest temperature of 100 C, the characteristic spectral slope of the Tagish Lake meteorite sample increased. On the other hand, after irradiating its pellet sample with pulse laser, the slope decreased. As the result, the Tagish Lake meteorite and its processed samples have come to cover a wide range of visible reflectance spectra in slope from the C-type asteroids to some extreme T/D-type asteroids, including the P-type asteroids in between. Therefore, logically speaking, our initial affirmation that the Tagish Lake meteorite must have come from one of the D-type asteroids can be wrong if such a meteoritic material is hidden under a space-weathered surface regolith of a C-type asteroid. However, such a case is likely to have a small probability in general. Other major hits of this research includes the first spectral fitting of the P-type asteroids using reflectance spectra derived from the present research. This topic needs more experiments and analysis to be addressed uniquely, and thus further efforts will be proposed.

Hiroi, Takahiro↗
NASA NTRS1986

Studies of asteroids and comets

About 3000 accurate positions of asteroids and comets were measured concentrating particularly on close-Earth approachers, but also targeting asteroids in need for follow-up observations because of unusual orbital characteristics or poor observational history. In 1985, 36 of the discoveries were numbered. Very accurate + or - 0.1 arcsec?) positional measurements were made of P/Halley on four nights in November and December 1985 in support of Giotto mission navigation. The asteroid orbit files were maintained, and ephemeris data for observational planning were supplied to colleagues worldwide. Considerable progress was made in understanding how information on asteroid shapes, surface albedo variegation, and rotational states can be derived from lightcurve and phase curve data. The analytical formulation was completed of a new asteroid magnitude system for the International Astronomical Union; the system was adopted at the New Delhi General Assembly by IAU Commission 20. Photographic photometry of about 10000 images of faint asteroids observed during the course of the United Kingdom Schmidt-CalTech Asteroid Survey in 1981 was continued, completing the microdensitometric scanning and all process of software development for data handling.

Bowell, E. L. G.↗
NASA NTRS1989

Global environmental effects of impact-generated aerosols: Results from a general circulation model, revision 1

Interception of sunlight by the high altitude worldwide dust cloud generated by impact of a large asteroid or comet would lead to substantial land surface cooling, according to our three-dimensional atmospheric general circulation model (GCM). This result is qualitatively similar to conclusions drawn from an earlier study that employed a one-dimensional atmospheric model, but in the GCM simulation the heat capacity of the oceans substantially mitigates land surface cooling, an effect that one-dimensional models cannot quantify. On the other hand, the low heat capacity of the GCM's land surface allows temperatures to drop more rapidly in the initial stage of cooling than in the one-dimensional model study. These two differences between three-dimensional and one-dimensional model simulations were noted previously in studies of nuclear winter; GCM-simulated climatic changes in the Alvarez-inspired scenario of asteroid/comet winter, however, are more severe than in nuclear winter because the assumed aerosol amount is large enough to intercept all sunlight falling on earth. Impacts of smaller objects could also lead to dramatic, though less severe, climatic changes, according to our GCM. Our conclusion is that it is difficult to imagine an asteroid or comet impact leading to anything approaching complete global freezing, but quite reasonable to assume that impacts at the Alvarez level, or even smaller, dramatically alter the climate in at least a patchy sense.

Covey, Curt↗
NASA NTRS1994

Ultraviolet spectra and geometric albedos of 45 asteroids

Spectral reflectances and geometic albedos between 2300 and 3250 A are determined for 45 asteroids from data acquired by the International Ultraviolet Explorer satellite. The geometric albedos are consistently low, ranging from approximately 0.02 for C-type asteroids to approximately 0.08 for M-type asteroids. An exception is the single E-type asteroid (44 Nysa) with a geometric albedo of 0.3 at 2950 A. We find that the three major asteroid taxonomic classes persist into the UV. The taxonomic classes are distinguished primarily by their albedos, but S types are generally redder than C or M types. The first ultraviolet phase curved of asteroids are presented.

Roettger, E. E.↗
NASA NTRS1962

Fossil Glasses Produced by Impact of Meteorites, Asteroids and Possibly Comets with the Planet Earth

In recent times one of the most intriguing mysteries of geology bas been the occurrence of aerodynamically-shaped glasses on five continents of the earth. These glasses under discussion are obviously not of fulgurite origin. Recent research indicates that these glasses known as tektites are ~he result of meteorite, asteroid, or possibly comet impact. Impact glasses, in general, differ from volcanic glasses in that they are lower in water content, have lower gallium and germanium contents, and are not necessarily in magmatically unstable continental areas.

Cohen, A. J.↗
NASA NTRS1993

A method to determine asteroid poles

The determination of spin axis and shape is well known to be of fundamental importance for studies about the rotational and physical properties of asteroids. In particular, knowledge that the pole coordinate distribution is random or not could indicate the probable non-Maxwellian distribution of asteroid spin axes, while the distribution in terms of size and shape could place important constraints on the theories about the collisional history of some individual asteroids, of asteroid families, and of the asteroid population as a whole. Many kinds of methods have been developed to determine pole coordinates. An EA method is presented, from which it is possible to obtain the solution with no trial poles, but with a simultaneous least square fit on both the E and A part. Results for rotational and shape parameters were obtained for 18 asteroids: the values of the obtained parameters are generally in close agreement with those of others.

Deangelis, G.↗
NASA NTRS1994

Some considerations on velocity vector accuracy in dust trajectory analysis

The relative contributions of comets and asteroids to the reservoir of dust in the interplanetary medium is not known. There are direct observations of dust released from comets and there is evidence to associate the IRAS dust bands with possible collisions of asteroids in the main belt. A means to sorting out the parent sources has been proposed in the establishment of a dust collector in orbit about the Earth. In order to characterize the orbits of particles as they crossed the Earth's orbits, a study of the long-time dust orbital evolution was undertaken. We have considered various parameters associated with these dust orbits to see if one may in a general way discriminate between particles evolved from comets and asteroids.

Jackson, A. A.↗
NASA NTRS2010

Zero Secular Torque on Asteroids from Impinging Solar Photons in the YORP Effect: A Simple Proof

YORP torques, where "YORP" stands for "Yarokovsky-O'Keefe-Radzievskii-Paddack." arise mainly from sun light reflected off a Solar System object and the infrared radiation emi tted by it. We show here, through the most elementary demonstration that we Can devise, that secular torques from impinging solar photons are generally negligible and thus cause little secular evolution of an asteroid's obliquity or spin rate.

Rubincam, David Perry↗