The Asteroid Impact & Deflection Assessment (AIDA) mission will be the first space experiment to demonstrate asteroid impact hazard mitigation by using a kinetic impactor to deflect an asteroid. AIDA ...is an international cooperation, consisting of two mission elements: the NASA Double Asteroid Redirection Test (DART) mission and the ESA Asteroid Impact Mission (AIM) rendezvous mission. The primary goals of AIDA are (i) to test our ability to perform a spacecraft impact on a potentially hazardous near-Earth asteroid and (ii) to measure and characterize the deflection caused by the impact. The AIDA target will be the binary near-Earth asteroid (65803) Didymos, with the deflection experiment to occur in late September, 2022. The DART impact on the secondary member of the binary at ~7km/s is expected to alter the binary orbit period by about 4 minutes, assuming a simple transfer of momentum to the target, and this period change will be measured by Earth-based observatories. The AIM spacecraft will characterize the asteroid target and monitor results of the impact in situ at Didymos. The DART mission is a full-scale kinetic impact to deflect a 150m diameter asteroid, with known impactor conditions and with target physical properties characterized by the AIM mission. Predictions for the momentum transfer efficiency of kinetic impacts are given for several possible target types of different porosities, using Housen and Holsapple (2011) crater scaling model for impact ejecta mass and velocity distributions. Results are compared to numerical simulation results using the Smoothed Particle Hydrodynamics code of Jutzi and Michel (2014) with good agreement. The model also predicts that the ejecta from the DART impact may make Didymos into an active asteroid, forming an ejecta coma that may be observable from Earth-based telescopes. The measurements from AIDA of the momentum transfer from the DART impact, the crater size and morphology, and the evolution of an ejecta coma will substantially advance understanding of impact processes on asteroids.
•AIDA will be the first space mission to demonstrate asteroid impact hazard mitigation.•AIDA will use a kinetic impactor to deflect an asteroid and measure the deflection.•AIDA is an international cooperation between ESA and NASA.•AIDA will study asteroid strength, surface physical properties and internal structure.
Understanding the nature and origin of the asteroid population in Earth's vicinity (near-Earth asteroids, and its subset of potentially hazardous asteroids) is a matter of both scientific interest ...and practical importance. It is generally expected that the compositions of the asteroids that are most likely to hit Earth should reflect those of the most common meteorites. Here we report that most near-Earth asteroids (including the potentially hazardous subset) have spectral properties quantitatively similar to the class of meteorites known as LL chondrites. The prominent Flora family in the inner part of the asteroid belt shares the same spectral properties, suggesting that it is a dominant source of near-Earth asteroids. The observed similarity of near-Earth asteroids to LL chondrites is, however, surprising, as this meteorite class is relatively rare (∼8 per cent of all meteorite falls). One possible explanation is the role of a size-dependent process, such as the Yarkovsky effect, in transporting material from the main belt.
Context. (65) Cybele is the most representative member of a population of primitive asteroids in the outer edge of the main belt, the Cybele asteroids. Recent dynamical models suggest that a ...significant fraction of them originated in the primordial transneptunian disk, so the study of the physical properties of these asteroids is potentially a useful test of these models. Aims. Our aim is to obtain information on the surface composition of this asteroid. In particular we want to obtain information on the composition and properties of the regolith and the possible presence of ices and organic materials. Methods. We present 2–4 μm and 5–14 μm spectroscopy of (65) Cybele obtained with the NASA IRTF telescope and Spitzer Space Telescope respectively. We compare the results with spectra of Trojan asteroids and asteroid (24) Themis. We analyze the 2–4 μm spectrum using scattering models and we apply thermal models to the 5–14 μm data. Results. The 2–4 μm spectrum of (65) Cybele presents an absorption band centered at ~3.1 μm and more weaker bands in the 3.2–3.6 μm region, very similar to those observed in (24) Themis. No hydrated silicates are detected. From the spectrum in the 5–14 μm region an effective diameter D = 290 ± 5 km, a beaming paramete η = 0.967 ± 0.014, and a geometric visible albedo pV = 0.05 ± 0.01 are derived using the NEATM thermal model. The emisivity spectrum in the 5–14 μm range exhibits an emission plateau at about 9 to 12 μm with an spectral contrast of ~5%. This emission is similar to that of Trojan asteroids and active comets and may be due to small silicate grains being imbedded in a relatively transparent matrix, or to a very under-dense (fairy-castle) surface structure. The lower amplitude of the silicate emission in Cybele’s spectrum with respect to that of Trojan asteroids could be attributed to larger dust particles and/or a slightly denser structure. Conclusions. The surface of (65) Cybele is covered by a fine anhydrous silicate grains mantle, with a small amount of water ice and complex organic solids. This is similar to comet surface where non-equilibrium phases coexist. The presence of water-ice and anhydrous silicates is indicative that hydration did not happened or is incomplete, suggesting that the temperatures were always sufficiently low.
The Asteroid Impact and Deflection Assessment (AIDA) mission will be the first space experiment to demonstrate asteroid impact hazard mitigation by using a kinetic impactor to deflect an asteroid. ...AIDA is an international cooperation entering Phase A study at NASA and ESA, consisting of two mission elements: the NASA Double Asteroid Redirection Test (DART) mission and the ESA Asteroid Impact Mission (AIM) rendezvous mission. The primary goals of AIDA are (i) to test our ability to perform a spacecraft impact on a potentially hazardous near-Earth asteroid and (ii) to measure and characterize the deflection caused by the impact. The AIDA target will be the binary asteroid (65803) Didymos, with the deflection experiment to occur in October, 2022. The DART impact on the secondary member of the binary at ~6km/s will alter the binary orbit period, which can be measured by Earth-based observatories. The AIM spacecraft will characterize the asteroid target and monitor results of the impact in situ at Didymos. AIDA will return fundamental new information on the mechanical response and impact cratering process at real asteroid scales, and consequently on the collisional evolution of asteroids with implications for planetary defense, human spaceflight, and near-Earth object science and resource utilization. AIDA will return unique information on an asteroid׳s strength, surface physical properties and internal structure. Supporting Earth-based optical and radar observations, numerical simulation studies and laboratory experiments will be an integral part of AIDA.
•AIDA will be the first space mission to demonstrate asteroid impact hazard mitigation.•AIDA will use a kinetic impactor to deflect an asteroid and measure the deflection.•AIDA is an international cooperation between ESA and NASA.•AIDA will study asteroid strength, surface physical properties and internal structure.
We present observational evidence that carbonates and iron-rich clays are present on the surface of Ceres. These components are also present in CI chondrites and provide a means of explaining the ...unusual spectrum of this object as well as providing potential insight into its evolution.
•Spectra for more than 1000 near-Earth objects (NEOs) are presented and analyzed.•NEOs originate from specific regions in the main asteroid belt, according to type.•Meteorites linked to NEO classes ...show specific escape regions from the main belt.•Distinct spectral trends are found for surface alteration by radiation and impacts.•Altered surfaces become refreshed by planetary encounters and other processes.
Advancing technology in near-infrared instrumentation and dedicated planetary telescope facilities have enabled nearly two decades of reconnoitering the spectral properties for near-Earth objects (NEOs). We report measured spectral properties for more than 1000 NEOs, representing >5% of the currently discovered population. Thermal flux detected below 2.5 µm allows us to make albedo estimates for nearly 50 objects, including two comets. Additional spectral data are reported for more than 350 Mars-crossing asteroids. Most of these measurements were achieved through a collaboration between researchers at the Massachusetts Institute of Technology and the University of Hawaii, with full cooperation of the NASA Infrared Telescope Facility (IRTF) on Mauna Kea. We call this project the MIT-Hawaii Near-Earth Object Spectroscopic Survey (MITHNEOS; myth-neos). While MITHNEOS has continuously released all spectral data for immediate use by the scientific community, our objectives for this paper are to: (1) detail the methods and limits of the survey data, (2) formally present a compilation of results including their taxonomic classification within a single internally consistent framework, (3) perform a preliminary analysis on the overall population characteristics with a concentration toward deducing key physical processes and identifying their source region for escaping the main belt. Augmenting our newly published measurements are the previously published results from the broad NEO community, including many results graciously shared by colleagues prior to formal publication. With this collective data set, we find the near-Earth population matches the diversity of the main-belt, with all main-belt taxonomic classes represented in our sample. Potentially hazardous asteroids (PHAs) as well as the subset of mission accessible asteroids (ΔV ≤ 7 km/s) both appear to be a representative mix of the overall NEO population, consistent with strong dynamical mixing for the population that interacts most closely with Earth. Mars crossers, however, are less diverse and appear to more closely match the inner belt population from where they have more recently diffused. The fractional distributions of major taxonomic classes (60% S, 20% C, 20% other) appear remarkably constant over two orders of magnitude in size (10 km to 100 m), which is eight orders of magnitude in mass, though we note unaccounted bias effects enter into our statistics below about 500 m. Given the range of surface ages, including possible refreshment by planetary encounters, we are able to identify a very specific space weathering vector tracing the transition from Q- to Sq- to S-types that follows the natural dispersion for asteroid spectra mapped into principal component space. We also are able to interpret a shock darkening vector that may account for some objects having featureless spectra. Space weathering effects for C-types are complex; these results are described separately by Lantz, Binzel, DeMeo. (2018, Icarus 302, 10–17). Independent correlation of dynamical models with taxonomic classes map the escape zones for NEOs to main-belt regions consistent with well established heliocentric compositional gradients. We push beyond taxonomy to interpret our visible plus near-infrared spectra in terms of the olivine and pyroxene mineralogy consistent with the H, L, and LL classes of ordinary chondrites meteorites. Correlating meteorite interpretations with dynamical escape region models shows a preference for LL chondrites to arrive from the ν6 resonance and H chondrites to have a preferential signature from the mid-belt region (3:1 resonance). L chondrites show some preference toward the outer belt, but not at a significant level. We define a Space Weathering Parameter as a continuous variable and find evidence for step-wise changes in space weathering properties across different planet crossing zones in the inner solar system. Overall we hypothesize the relative roles of planetary encounters, YORP spin-up, and thermal cycling across the inner solar system.
We present new visible and near-infrared spectroscopic measurements for 252 near-Earth (NEO) and Mars-crossing (MC) objects observed from 1994 through 2002 as a complement to the Small Main-Belt ...Asteroid Spectroscopic Survey (SMASS,
http://smass.mit.edu/). Combined with previously published SMASS results, we have an internally consistent data set of more than 400 of these objects for investigating trends related to size, orbits, and dynamical history. These data also provide the basis for producing a bias-corrected estimate for the total NEO population (Stuart and Binzel, 2004, Icarus 170, 295–311). We find 25 of the 26 Bus (1999, PhD thesis) taxonomic types are represented, with nearly 90% of the objects falling within the broad S-, Q-, X-, and C-complexes. Rare A- and E-types are more common in the MC than NEO population (about 5% compared to <1%) and may be direct evidence of slow diffusion into MC orbits from the Flora and Hungaria regions, respectively. A possible family of MC objects (C-types) may reside at the edge of the 5:2 jovian resonance. Distinct signatures are revealed for the relative contributions of different taxonomic types to the NEO population through different source regions. E-types show an origin signature from the inner belt, C-types from the mid to outer belt, and P-types from the outer belt. S- and Q-types have effectively identical main-belt source region profiles, as would be expected if they have related origins. A lack of V-types among Mars-crossers suggests entry into NEO space via rapid transport through the
ν6 and 3:1 resonances from low eccentricity main-belt orbits, consistent with a Vesta origin. D-types show the strongest signature from Jupiter family comets (JFC), with a strong JFC component also seen among the X-types. A distinct taxonomic difference is found with respect to the jovian Tisserand parameter
T, where C-, D-, and X-type (most likely low albedo P-class) objects predominate for
T⩽3. These objects, which may be extinct comets, comprise 4% of our observed sample, but their low albedos makes this magnitude limited fraction under-representative of the true value. With our taxonomy statistics providing a strong component to the diameter limited bias correction analysis of Stuart (2003, PhD thesis), we estimate 10–18% of the NEO population above any given diameter may be extinct comets, taking into account asteroids scattered into
T<3 orbits and comets scattered into
T>3 orbits. In terms of possible space weathering effects, we see a size-dependent transition from ordinary chondrite-like (Q-type) objects to S-type asteroids over the size range of 0.1 to 5 km, where the transition is effectively complete at 5 km. A match between the average surface age of 5 km asteroids and the rate of space weathering could constrain models for both processes. However, space weathering may proceed at a very rapid rate compared with collisional timescales. In this case, the presence or absence of a regolith may be the determining factor for whether or not an object appears “space weathered.” Thus 0.1 to 5 km appears to be a critical size range for understanding the processes, timescales, and conditions under which a regolith conducive to space weathering is generated, retained, and refreshed.
•We investigated the distribution of surface constituents on the uranian satellites.•CO2 ice abundance is greatest on the trailing hemispheres of moons closest to Uranus.•Spectral modeling indicates ...that CO2 ice is pure and isolated from other species.•H2O ice bands are stronger on the leading hemispheres of the uranian satellites.•Our results suggest that the uranian moons’ surfaces are compositionally stratified.
The surfaces of the large uranian satellites are characterized by a mixture of H2O ice and a dark, potentially carbon-rich, constituent, along with CO2 ice. At the mean heliocentric distance of the uranian system, native CO2 ice should be removed on timescales shorter than the age of the Solar System. Consequently, the detected CO2 ice might be actively produced. Analogous to irradiation of icy moons in the Jupiter and Saturn systems, we hypothesize that charged particles caught in Uranus’ magnetic field bombard the surfaces of the uranian satellites, driving a radiolytic CO2 production cycle. To test this hypothesis, we investigated the distribution of CO2 ice by analyzing near-infrared (NIR) spectra of these moons, gathered using the SpeX spectrograph at NASA’s Infrared Telescope Facility (IRTF) (2000–2013). Additionally, we made spectrophotometric measurements using images gathered by the Infrared Array Camera (IRAC) onboard the Spitzer Space Telescope (2003–2005). We find that the detected CO2 ice is primarily on the trailing hemispheres of the satellites closest to Uranus, consistent with other observations of these moons. Our band parameter analysis indicates that the detected CO2 ice is pure and segregated from other constituents. Our spectrophotometric analysis indicates that IRAC is not sensitive to the CO2 ice detected by SpeX, potentially because CO2 is retained beneath a thin surface layer dominated by H2O ice that is opaque to photons over IRAC wavelengths. Thus, our combined SpeX and IRAC analyses suggest that the near-surfaces (i.e., top few 100μm) of the uranian satellites are compositionally stratified. We briefly compare the spectral characteristics of the CO2 ice detected on the uranian moons to icy satellites elsewhere, and we also consider the most likely drivers of the observed distribution of CO2 ice.
“LICIACube – the Light Italian Cubesat for Imaging of Asteroids” is managed by the Italian Space Agency (ASI) and will be part of the NASA DART mission, with the aim of i) documenting the DART ...impact’s effects on the secondary member of the (65803) Didymos binary asteroid system, ii) characterizing the shape of the target, and iii) performing dedicated scientific investigations on it. DART probe will be launched at the end of 2021 and LICIACube will be hosted as piggyback during the interplanetary cruise, then released 10 days before the impact, and autonomously guided along its fly-by trajectory. The LICIACube payload is composed by LEIA, a narrow FoV camera, and LUKE, a wide FoV imager with an RGB Bayer pattern filter, that will collect and transmit to Earth several unique images of the effects of the DART impact on the asteroid, such as the formation and the development of the plume potentially determined by the impact.
LICIACube will be the first deep space mission developed and autonomously managed by an Italian team: the design, integration and test of the CubeSat have been assigned by ASI to the aerospace company Argotec, while the LICIACube Ground Segment has a complex architecture based on the Argotec Mission Control Center, antennas of the NASA Deep Space Network and data archiving and processing, managed at the ASI Space Science Data Center. The LICIACube team includes a wide Italian scientific community, involved in the definition of all the aspects of the mission: trajectory design; mission definition (and real-time orbit determination during operations); impact, plume and imaging simulation and modelling, in preparation of a suitable framework for the analysis and interpretation of in-situ data. The major technological mission challenge, i.e. the autonomous targeting and imaging of such a small body during a fast fly-by, to be accomplished with the limited resources of a CubeSat, is affordable thanks to a strong synergy of all the mentioned teams in support of the engineering tasks.
-LICIACube is the first purely Italian spacecraft operating in deep space.-LICIACube is managed by the Italian Space Agency and will be part of the NASA DART mission.-It will analyze the output of the first kinetic impact test at a realistic scale.-The payload is composed by LEIA, a narrow FoV camera, and LUKE, a wide FoV imager with an RGB Bayer pattern filter.-Aims: documenting the DART impact on Dimorphos; characterizing the target shape; performing scientific investigations.
ABSTRACT
The Hera mission will arrive at the Didymos system to study the efficiency of momentum transfer and to further investigate the binary system in great detail after the Double Asteroid ...Redirection Test (DART) mission impact. We took advantage of two online data bases of meteorites spectra and of recent Didymos spectra taken before and after the DART impact. We performed the first selection based on the comparison of the band centre values of the silicate absorption bands (localized at 1 and 2 μm) between Didymos and the meteorites. The second selection was made defining a four-dimensional space parameter whose dimensions were the band depth and the slope of the two bands, normalized to Didymos values. We introduced a distance measure to find the closest meteorites to Didymos in this space. Finally, we made the last selection based on other criteria, such as the presence of different spectra of the same meteorite, the presence of different spectra from different data bases, and the comparison with the literature. The result of this work is a list of six meteorites that are the most analogous to Didymos system. We also found out that Didymos is most probably mainly composed of L/LL ordinary chondrites, with a preference for the LL sub-type. From our list of meteorites, we were able to estimate the normalized abundance of olivine and pyroxene of Didymos. Finally, a match between Didymos and OC meteorites was also found in the Mid-InfraRed (MIR) range.
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