arXiv subjects

Driss Takir

Publications and source records attributed to Driss Takir.

At least 19 recordsLinked to original sources

arXiv2026

The Polana-Eulalia Complex with JWST NIRSpec: Connections to Bennu, Ryugu, and Outer Solar System Bodies

Carbon rich [C complex] asteroids provide insight into the early Solar System, and families of C complex asteroids serve as robust samples for learning about the internal structure of planetesimals and the materials of the protoplanetary disk. This work investigates the compositions of asteroids within the Polana Eulalia Complex [PEC] through analyses of JWST NIRSpec. Obtained as part of the Spectral Analysis of Main Belt Asteroids in the 3 um Region [SAMBA3] project. NIRSpec observations were conducted for the namesake asteroid of the Eulalia family, [495] Eulalia, as well as three members from the Polana family: [2441] Hibbs, [6712] Hornstein, and [6769] Brokoff. Analyses of the 2.7 um region demonstrate that PEC asteroids exhibit absorptions associated with Mg rich phyllosilicates, in turn underscoring high, though incomplete, degrees of aqueous alteration in the past for both PEC families. Although consistent in regard to composition, [142] Polana and [495] Eulalia show deeper 2.7 um bands than the Polana family asteroids, suggesting slight differences in the degrees of aqueous alteration between large and small PEC asteroids. Minor absorptions from 3.0 to 4.0 um indicate that [495] Eulalia's surface may contain more carbonates than [142] Polana, which potentially highlights slight differences between each family's formation and evolution. Additionally, PEC asteroids also show spectral consistency with Bennu and Ryugu, reinforcing their shared origin in the PEC. Minor absorptions in PEC asteroid spectra also connect to small bodies within and beyond the Main Belt, providing further evidence of outer Solar System formation for the PEC parent bodies.

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arXiv2025

Compositional characterisation of asteroid (84) Klio with JWST

The analysis of the composition of primitive C$-$complex asteroids is essential to understand the distribution of volatiles in the Solar System since its formation. Primitive low-albedo families within the inner main asteroid belt are of particular interest because they are a significant source of carbonaceous near-Earth asteroids, such as Ryugu and Bennu. This study, part of the JWST SAMBA3 project (Spectral Analysis of Main Belt Asteroids in the 3 $μ$m region), report the first spectroscopic analysis of asteroid (84) Klio in the 3 $μ$m region, in order to better constrain its composition. We analysed the infrared (0.97$-$5.10 $μ$m) Spectrum of Klio measured by the NIRSpec instrument on board JWST. We used the NEATM thermal model to extract the reflectance spectrum of the asteroid. Several spectral features were then analysed in the 2.8, 3.4, and 3.9 $μ$m regions by different Gaussian fitting. The Spectrum of Klio shows an absorption band at 2.776 $\pm$ 0.001 $μ$m that we attributed to phyllosilicates. We compared the position and shape of the feature with that observed in primitive materials such as carbonaceous chondrites and returned samples from Ryugu and Bennu. The position and shape of the 2.8 $μ$m band, as well as the presence of a 0.7 $μ$m band in the visible, suggest that Klio's spectrum is similar to certain CM2 meteorites. We observed an absorption band around 3.9 $μ$m, with a depth of $0.020 \pm 0.001$ that could be attributed to carbonates. We could not clearly detect any absorption associated with organics at 3.4 $μ$m.

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arXiv2024

Estimate of water and hydroxyl abundance on asteroid (16) Psyche from JWST data

Our understanding of Solar System evolution is closely tied to interpretations of asteroid composition, particularly the M-class asteroids. These asteroids were initially thought to be the exposed cores of differentiated planetesimals, a hypothesis based on their spectral similarity to iron meteorites. However, recent astronomical observations have revealed hydration on their surface through the detection of 3-$μ$m absorption features associated with OH and potentially H2O. We present evidence of hydration due mainly to OH on asteroid (16) Psyche, the largest M-class asteroid, using data from the James Webb Space Telescope (JWST) spanning 1.1 - 6.63 $μ$m. Our observations include two detections of the full 3-$μ$m feature associated with OH and H2O resembling those found in CY-, CH-, and CB-type carbonaceous chondrites, and no 6-$μ$m feature uniquely associated with H2O across two observations. We observe 3-$μ$m depths of between 4.3 and 6% across two observations, values consistent with hydrogen abundance estimates on other airless bodies of 250 - 400 ppm. We place an upper limit of 39 ppm on the water abundance from the standard deviation around the 6-$μ$m feature region. The presence of hydrated minerals suggests a complex history for Psyche. Exogenous sources of OH-bearing minerals could come from hydrated impactors. Endogenous OH-bearing minerals would indicate a composition more similar to E-or P-class asteroids. If the hydration is endogenous, it supports the theory that Psyche originated beyond the snow line and later migrated to the outer main belt.

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arXiv2024

Origin of Asteroid (101955) Bennu and its Connection to the New Polana Family

The asteroid (142) Polana is classified as a B-type asteroid located in the inner Main Belt. This asteroid is the parent of the New Polana family, which has been proposed to be the likely source of primitive near-Earth asteroids such as the B-type asteroid (101955) Bennu. To investigate the compositional correlation between Polana and Bennu at the 3-micron band and their aqueous alteration histories, we analyzed the spectra of Polana in the ~2.0-4.0-micron spectral range using the NASA Infrared Telescope Facility in Hawaii. Our findings indicate that Polana does not exhibit discernable 3-micron hydrated mineral absorption (within 2 sigma), which is in contrast to asteroid Bennu. Bennu displayed a significant 3-micron absorption feature similar to CM- and CI-type carbonaceous chondrites. This suggests two possibilities: either Bennu did not originate from the New Polana family parented by asteroid Polana or the interior of Bennu's parent body was not homogenous, with diverse levels of aqueous alteration. Several explanations support the latter possibility, including heating due to shock waves and pressure, which could have caused the current dehydrated state of Bennu's parent body.

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arXiv2023

Late Accretion of Ceres-like Asteroids and Their Implantation into the Outer Main Belt

Low-albedo asteroids preserve a record of the primordial solar system planetesimals and the conditions in which the solar nebula was active. However, the origin and evolution of these asteroids are not well-constrained. Here we measured visible and near-infrared (0.5 - 4.0 microns) spectra of low-albedo asteroids in the mid-outer main belt. We show that numerous large (d > 100 km) and dark (geometric albedo < 0.09) asteroids exterior to the dwarf planet Ceres' orbit share the same spectral features, and presumably compositions, as Ceres. We also developed a thermal evolution model that demonstrates that these Ceres-like asteroids have highly-porous interiors, accreted relatively late at 1.5 - 3.5 Myr after the formation of calcium-aluminum-rich inclusions, and experienced maximum interior temperatures of < 900 K. Ceres-like asteroids are localized in a confined heliocentric region between 3.0 - 3.4 au but were likely implanted from more distant regions of the solar system during the giant planet's dynamical instability.

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arXiv2022

Spectral evolution of dark asteroid surfaces induced by space weathering over a decade

The surface of airless bodies like asteroids in the Solar System are known to be affected by space weathering. Experiments simulating space weathering are essential for studying the effects of this process on meteorite samples, but the problem is that the time spent to reproduce space weathering in these experiments is billions of times shorter than the actual phenomenon. In December 2010, the T-type asteroid 596 Scheila underwent a collision with a few-tens-of-meters impactor. A decade later, there is an opportunity to study how the surface layer of this asteroid is being altered by space weathering after the impact. To do so, we performed visible spectrophotometric and near-infrared spectroscopic observations of 596 Scheila. The acquired spectrum is consistent with those observed shortly after the 2010 impact event within the observational uncertainty range. This indicates that the surface color of dark asteroids is not noticeably changed by space weathering over a 10-year period. This study is the first to investigate color changes due to space weathering on an actual asteroid surface in the Solar System. Considering that fresh layers are regularly created on asteroid surfaces by collisions, we suggest a genetic link between D/T-type and dark (low albedo) X-complex asteroids and very red objects such as 269 Justitia, 732 Tjilaki (and 203 Pompeja). New observations show that 203 Pompeja has a X-type-like surface, with some local surface areas exhibiting a very red spectrum.

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arXiv2020

Near-infrared observations of active asteroid (3200) Phaethon reveal no evidence for hydration

Asteroid (3200) Phaethon is an active near-Earth asteroid and the parent body of the Geminid Meteor Shower. Because of its small perihelion distance, Phaethon's surface reaches temperatures sufficient to destabilize hydrated materials. We conducted rotationally resolved spectroscopic observations of this asteroid, mostly covering the northern hemisphere and the equatorial region, beyond 2.5-micron to search for evidence of hydration on its surface. Here we show that the observed part of Phaethon does not exhibit the 3-micron hydrated mineral absorption (within 2-sigma). These observations suggest that Phaethon's modern activity is not due to volatile sublimation or devolatilization of phyllosilicates on its surface. It is possible that the observed part of Phaethon was originally hydrated and has since lost volatiles from its surface via dehydration, supporting its connection to the Pallas family, or it was formed from anhydrous material.

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arXiv2019

3-micron Reflectance Spectroscopy of Carbonaceous Chondrites under Asteroid-like Conditions

We measured 3-micron reflectance spectra of 21 meteorites that represent all carbonaceous chondrite types available in terrestrial meteorite collections. The measurements were conducted at the Laboratory for Spectroscopy under Planetary Environmental Conditions (LabSPEC) at the Johns Hopkins University Applied Physics Laboratory (JHU APL) under vacuum and thermally-desiccated conditions (asteroid-like conditions). This is the most comprehensive 3-micron dataset of carbonaceous chondrites ever acquired in environments similar to the ones experienced by asteroids. The 3-micron reflectance spectra are extremely important for direct comparisons with and appropriate interpretations of reflectance data from ground-based telescopic and spacecraft observations of asteroids. We found good agreement between 3-μm spectral characteristics of carbonaceous chondrites and carbonaceous chondrite classifications. The 3-μm band is diverse, indicative of varying composition, thus suggesting that these carbonaceous chondrites experienced distinct parent body aqueous alteration and metamorphism environments.

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arXiv2018

Rotationally-Resolved Spectroscopic Characterization of near-Earth object (3200) Phaethon

(3200) Phaethon is a compelling object as it has an asteroidal appearance and spectrum, produces a weak dust tail during perihelion at just 0.14 AU, and is the parent body of the Geminid Meteor Shower. A better understanding of the physical properties of Phaethon is needed to understand the nature of its current and previous activity, relationship to potential source populations, and to plan for the upcoming flyby of the DESTINY+ spacecraft of Phaethon in the 2020s. We performed rotationally-resolved spectroscopy of Phaethon at visible and near-infrared wavelengths (0.4-2.5 microns) in 2007 and 2017, respectively, to better understand its surface properties. The visible and near-infrared observations both spanned nearly a full rotation or more and were under similar observing geometries, covering the whole surface with the exception of the north pole. The visible wavelengths show blue slopes with only minor slope variations and no absorption features. The NIR data is minimally varying and concave upwards, from very blue to blue-neutral with increasing wavelength. We fit the short-wavelength tail of Phaethon's thermal emission and retrieve an average visible albedo of pv = 0.08 +/- 0.01, which is lower than previous measurements but plausible in light of the recent larger radar-measured diameter of Phaethon. We retrieve an average infrared beaming parameter of Phaethon of eta = 1.70 +/- 0.05, which is similar to previous results. We discuss the implications of Phaethon's visible and near-infrared spectrum as well as the lower albedo on its origin, source population, and evolutionary history.

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arXiv2018

Asteroid Ryugu Before the Hayabusa2 Encounter

Asteroid (162173) Ryugu is the target object of Hayabusa2, an asteroid exploration and sample return mission led by Japan Aerospace Exploration Agency (JAXA). Ground-based observations indicate that Ryugu is a C-type near-Earth asteroid with a diameter of less than 1 km, but the knowledge of its detailed properties is still very limited. This paper summarizes our best understanding of the physical and dynamical properties of Ryugu based on remote sensing and theoretical modeling. This information is used to construct a design reference model of the asteroid that is used for formulation of mission operations plans in advance of asteroid arrival. Particular attention is given to the surface properties of Ryugu that are relevant to sample acquisition. This reference model helps readers to appropriately interpret the data that will be directly obtained by Hayabusa2 and promotes scientific studies not only for Ryugu itself and other small bodies but also for the Solar System evolution that small bodies shed light on.

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arXiv2017

Ground-based Characterization of Hayabusa2 Mission Target Asteroid 162173 Ryugu: Constraining Mineralogical Composition in Preparation for Spacecraft Operations

Asteroids that are targets of spacecraft missions are interesting because they present us with an opportunity to validate ground-based spectral observations. One such object is near-Earth asteroid (NEA) (162173) Ryugu, which is the target of the Japanese Space Agency's (JAXA) Hayabusa2 sample return mission. We observed Ryugu using the 3-m NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii, on July 13, 2016 to constrain the object's surface composition, meteorite analogs, and link to other asteroids in the main belt and NEA populations. We also modeled its photometric properties using archival data. Using the Lommel-Seeliger model we computed the predicted flux for Ryugu at a wide range of viewing geometries as well as albedo quantities such as geometric albedo, phase integral, and spherical Bond albedo. Our computed albedo quantities are consistent with results from Ishiguro et al. (2014). Our spectral analysis has found a near-perfect match between our spectrum of Ryugu and those of NEA (85275) 1994 LY and Mars-crossing asteroid (316720) 1998 BE7, suggesting that their surface regoliths have similar composition. We compared Ryugu's spectrum with that of main belt asteroid (302) Clarissa, the largest asteroid in the Clarissa asteroid family, suggested as a possible source of Ryugu by Campins et al. (2013). We found that the spectrum of Clarissa shows significant differences with our spectrum of Ryugu, but it is similar to the spectrum obtained by Moskovitz et al. (2013). The best possible meteorite analogs for our spectrum of Ryugu are two CM2 carbonaceous chondrites, Mighei and ALH83100.

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arXiv2017

The compositional diversity of non-Vesta basaltic asteroids

We present near-infrared (0.78-2.45 μm) reflectance spectra for nine middle and outer main belt (a > 2.5 AU) basaltic asteroids. Three of these objects are spectrally distinct from all classifications in the Bus-DeMeo system and could represent spectral end members in the existing taxonomy or be representatives of a new spectral type. The remainder of the sample are classified as V- or R- type. All of these asteroids are dynamically detached from the Vesta collisional family, but are too small to be intact differentiated parent bodies, implying that they originated from differentiated planetesimals which have since been destroyed or ejected from the solar system. The 1- and 2-μm band centers of all objects, determined using the Modified Gaussian Model (MGM), were compared to those of 47 Vestoids and fifteen HED meteorites of known composition. The HEDs enabled us to determine formulas relating Band 1 and Band 2 centers to pyroxene ferrosilite (Fs) compositions. Using these formulas we present the most comprehensive compositional analysis to date of middle and outer belt basaltic asteroids. We also conduct a careful error analysis of the MGM-derived band centers for implementation in future analyses. The six outer belt V- and R-type asteroids show more dispersion in parameter space than the Vestoids, reflecting greater compositional diversity than Vesta and its associated bodies. The objects analyzed have Fs numbers which are, on average, between five and ten molar percent lower than those of the Vestoids; however, identification and compositional analysis of additional outer belt basaltic asteroids would help to confirm or refute this result. Given the gradient in oxidation state which existed within the solar nebula, these results tentatively suggest that these objects formed at either a different time or location than 4 Vesta.

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arXiv2017

Detection of Rotational Spectral Variation on the M-type asteroid (16) Psyche

The asteroid (16) Psyche is of scientific interest because it contains ~ 1% of the total mass of the asteroid belt and is thought to be the remnant metallic core of a protoplanet. Radar observations have indicated the significant presence of metal on the surface with a small percentage of silicates. Prior ground-based observations showed rotational variations in the near-infrared (NIR) spectra and radar albedo of this asteroid. However, no comprehensive study that combines multi-wavelength data has been conducted so far. Here we present rotationally resolved NIR spectra (0.7-2.5 microns) of (16) Psyche obtained with the NASA Infrared Telescope Facility. These data have been combined with shape models of the asteroid for each rotation phase. Spectral band parameters extracted from the NIR spectra show that the pyroxene band center varies from ~ 0.92 to 0.94 microns. Band center values were used to calculate the pyroxene chemistry of the asteroid, whose average value was found to be Fs30En65Wo5. Variations in the band depth were also observed, with values ranging from 1.0 to 1.5%. Using a new laboratory spectral calibration we estimated an average orthopyroxene content of 6+/-1%. The mass-deficit region of Psyche, which exhibits the highest radar albedo, also shows the highest value for spectral slope and the minimum band depth. The spectral characteristics of Psyche suggest that its parent body did not have the typical structure expected for a differentiated body or that the sequence of events that led to its current state was more complex than previously thought.

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arXiv2016

Detection of Water and/or Hydroxyl on Asteroid (16) Psyche

In order to search for evidence of hydration on M-type asteroid (16) Psyche, we observed this object in the 3 micron spectral region using the long-wavelength cross-dispersed (LXD: 1.9-4.2 micron) mode of the SpeX spectrograph/imager at the NASA Infrared Telescope Facility (IRTF). Our observations show that Psyche exhibits a 3 micron absorption feature, attributed to water or hydroxyl. The 3 micron absorption feature is consistent with the hydration features found on the surfaces of water-rich asteroids, attributed to OH- and/or H2O-bearing phases (phyllosilicates). The detection of a 3 micron hydration absorption band on Psyche suggests that this asteroid may not be metallic core, or it could be a metallic core that has been impacted by carbonaceous material over the past 4.5 Gyr. Our results also indicate rotational spectral variations, which we suggest reflect heterogeneity in the metal/silicate ratio on the surface of Psyche.

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arXiv2015

Asteroids and the James Webb Space Telescope

The James Webb Space Telescope (JWST) provides the opportunity for ground-breaking observations of asteroids. It covers wavelength regions that are unavailable from the ground, and does so with unprecedented sensitivity. The main-belt and Trojan asteroids are all observable at some point in the JWST lifetime. We present an overview of the capabilities for JWST and how they apply to the asteroids as well as some short science cases that take advantage of these capabilities.

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arXiv2015

The Physical Characterization of the Potentially-Hazardous Asteroid 2004 BL86: A Fragment of a Differentiated Asteroid

The physical characterization of potentially hazardous asteroids (PHAs) is important for impact hazard assessment and evaluating mitigation options. Close flybys of PHAs provide an opportunity to study their surface photometric and spectral properties that enable identification of their source regions in the main asteroid belt. We observed PHA (357439) 2004 BL86 during a close flyby of the Earth at a distance of 1.2 million km (0.0080 AU) on January 26, 2015, with an array of ground-based telescopes to constrain its photometric and spectral properties. Lightcurve observations showed that the asteroid was a binary and subsequent radar observations confirmed the binary nature and gave a primary diameter of 300 meters and a secondary diameter of 50-100 meters. Our photometric observations were used to derive the phase curve of 2004 BL86 in the V-band. Two different photometric functions were fitted to this phase curve, the IAU H-G model (Bowell et al. 1989) and the Shevchenko model (Shevchenko 1996). From the fit of the H-G function we obtained an absolute magnitude H=19.51+/-0.02 and a slope parameter G=0.34+/-0.02. The Shevchenko function yielded an absolute magnitude of H=19.03+/-0.07 and a phase coefficient b=0.0225+/-0.0006. The phase coefficient was used to calculate the geometric albedo (Ag) using the relationship found by Belskaya and Schevchenko (2000), obtaining a value of Ag=40+/-8% in the V-band. With the geometric albedo and the absolute magnitudes derived from the H-G and the Shevchenko functions we calculated the diameter (D) of 2004 BL86, obtaining D=263+/-26, and D=328+/-35 meters, respectively. 2004 BL86 spectral band parameters and pyroxene chemistry are consistent with non-cumulate eucrite meteorites.

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arXiv2015

Asteroid Photometry

Asteroid photometry has three major applications: providing clues about asteroid surface physical properties and compositions, facilitating photometric corrections, and helping design and plan ground-based and spacecraft observations. The most significant advances in asteroid photometry in the past decade were driven by spacecraft observations that collected spatially resolved imaging and spectroscopy data. In the mean time, laboratory measurements and theoretical developments are revealing controversies regarding the physical interpretations of models and model parameter values. We will review the new developments in asteroid photometry that have occurred over the past decade in the three complementary areas of observations, laboratory work, and theory. Finally we will summarize and discuss the implications of recent findings.

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arXiv2015

Phase Angle Effects on 3-micron Absorption Band on Ceres: Implications for Dawn Mission

Phase angle-induced spectral effects are important to characterize since they affect spectral band parameters such as band depth and band center, and therefore skew mineralogical interpretations of planetary bodies via reflectance spectroscopy. Dwarf planet (1) Ceres is the next target of NASA's Dawn mission, which is expected to arrive in March 2015. The visible and near-infrared mapping spectrometer (VIR) onboard Dawn has the spatial and spectral range to characterize the surface between 0.25-5.0 microns. Ceres has an absorption feature at 3.0 microns due to hydroxyl- and/or water-bearing minerals (e.g. Lebofsky et al. 1981, Rivkin et al. 2003). We analyzed phase angle-induced spectral effects on the 3-micron absorption band on Ceres using spectra measured with the long-wavelength cross-dispersed (LXD: 1.9-4.2 microns) mode of the SpeX spectrograph/imager at the NASA Infrared Telescope Facility (IRTF). Ceres LXD spectra were measured at different phase angles ranging from 0.7o to 22o. We found that the band center slightly increases from 3.06 microns at lower phase angles (0.7o and 6o) to 3.07 microns at higher phase angles (11 o and 22o), the band depth decreases by ~20% from lower phase angles to higher phase angles, and the band area decreases by ~25% from lower phase angles to higher phase angles. Our results will have implications for constraining the abundance of OH on the surface of Ceres from VIR spectral data, which will be acquired by Dawn starting spring 2015.

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