arXiv subjects

Theodore Kareta

Publications and source records attributed to Theodore Kareta.

At least 19 recordsLinked to original sources

arXiv2026

The Highly Unusual Behavior and Chemical Composition of Interstellar Comet 2I/Borisov

We report on imaging, spectroscopy, and narrowband photometry of interstellar comet 2I/Borisov obtained at Lowell Observatory from 2019 September 13 to December 16. We measured chemical composition on four nights before perihelion, from October 4 to November 25 (2.466 to 2.028 au), with CN detections on all nights. Our measurements from October 27 represent the earliest reported detections of C$_2$ and C$_3$, where C$_2$-to-CN and C$_3$-to-CN log production rate ratios were $-$0.7 and $-$1.3, respectively. Both ratios increased by nearly 4$\times$ to $-$0.3 and $-$0.9 by November 25, an extremely large increase with heliocentric distance that is unprecedented in the Lowell Observatory comet database. We additionally observed OH and NH on November 25, with a derived H$_2$O production rate of 4.5$\times $10$^{26}$ mol s$^{-1}$ and very high log production rate ratios for CN-to-OH ($-$2.0) and NH-to-OH ($-$1.7). Monitoring from broadband $R$ images from September 13 to December 16 suggests dust ($A(0^{\circ})f\rho$) production peaked around October 19, 50 days before its December 8 perihelion passage. Narrowband images from October 4 and 27 reveal a nearly symmetric CN distribution in Borisov's coma, suggesting activity over its entire sunward hemisphere and possibly its entire nucleus. Our results, combined with those from others, reveal a chemical composition and behavior with heliocentric distance unlike any other comet we have observed.

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arXiv2026

JWST Characterization of Earth Quasi-Satellite (469219) Kamo`oalewa

Near-Earth asteroid (469219) Kamo`oalewa is a uniquely stable quasi-satellite of the Earth and a target of the Tianwen-2 spacecraft mission. Here we report observations taken with JWST's NIRSpec instrument in integral field unit (IFU) mode in February 2026. The JWST reflectance spectrum is notably less red (more neutral) from $1.0-2.5$ $\mu m$ than previous ground-based spectrophotometric observations. New observations made with LBT in April 2026, observed and processed similarly to the 2021 observations, find $zJ$ colors in agreement with JWST. Kamo`oalewa's infrared colors appear more similar to S, V, or E-type silicate asteroids and unlike the reddened, space-weathered lunar-like silicates suggested by previous observations. In agreement with the ground-based spectrum, we detect a faint silicate absorption feature at $0.93\pm 0.01$ $\mu m$. We do not detect a 2.0 $\mu m$ silicate absorption. Models of Kamo`oalewa's faint thermal emission (beginning near 4.5 $\mu m$) find a mean diameter of $D=18\pm2\mathrm{m}$ and best-fit visible albedo $p_V = 0.59^{+0.25}_{-0.17}$, with models as low as $p_V = 0.36$ providing adequate model fits. This combination of color, albedo, and absorption bands is similar to oldhamite-bearing enstatite-rich compositions. Kamo`oalewa's brightness variations over the course of the JWST program provides independent confirmation of its rotation period of 27.9 minutes, with an axis ratio $\sim1.4$ ($D\sim15-21$ m).

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arXiv2026

Dust On, Dust Off: HST Observations of the Newly Dormant Jupiter Co-orbital Comet P/2023 V6 (PANSTARRS)

As the Centaurs of the Outer Solar System have become better studied, their relationship with the Jupiter Family Comets and their connection to the primordial protoplanetary disk has come under deeper scrutiny: which properties of the comets observed closer to the Sun are original, and which were modified significantly en route during their Centaur phase? The active Jupiter co-orbital comet P/2019 LD2 (ATLAS) attracted significant attention after its discovery when it was realized that the object would transition between a Centaur and JFC orbit in 2063, the first time this change can be observed and monitored in real time. In this study, we present new ground-based and Hubble Space Telescope imaging of the single other Jupiter co-orbital comet, P/2023 V6 (PANSTARRS), throughout late 2024 and early 2025. V6 was not detected in ground-based imaging after early October, and deep imaging with HST taken in early December is consistent with a $m_V = 28.06 \pm 0.03$ point source at its expected location. This both implies that the object ceased activity sometime in late 2024, and is thus in a different thermal state than LD2 despite both having large active fractions, and that V6's diameter is approximately $D\sim340$ meters. This is likely the smallest object directly observed by HST beyond the Main Belt, and certainly the smallest Centaur yet discovered, highlighting the ability to detect active sub-km objects beyond Jupiter with current surveys and potentially probing smaller sizes with LSST.

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arXiv2026

JWST and Gemini Observations of the Active Centaur 450P/LONEOS: Nucleus and Coma Characterizations

Between 2019 and 2024, we used the Gemini-N and JWST observatories to conduct a detailed case study of the active Centaur 450P/LONEOS, whose orbit was significantly altered by a close Saturn encounter in 1992. Gemini-N GMOS optical images likely captured the first views of 450P's inactive nucleus, indicating a relatively small radius of $R_N = 1.8\pm0.5$ km and a surface color of $g' - i' = 1.15\pm0.09$. This places 450P on the red end of the neutral/gray Centaur population and may indicate comparatively limited solar-driven surface processing relative to other known active Centaurs. A coma developed as 450P changed its heliocentric distance, $R_H$, from 7.83 au to 7.24 au, with an estimated low dust production rate of $\sim$4-8 kg s$^{-1}$. JWST NIRSpec IFU Prism-mode spectra revealed an elongated dust morphology and a symmetric $CO_2$ gas distribution in the coma but no $H_2O$ or CO emission features, with production rates of $Q_{CO_2} = (6.99\pm0.07)\times10^{24}$ molec. s$^{-1}$, $Q_{H_2O} \leq 1.2\times10^{24}$ molec. s$^{-1}$, and $Q_{CO} \leq 5.2\times10^{24}$ molec. s$^{-1}$. Absorption features at 2.0 and 3.0 $\mu$m indicate the presence of water ice, and a subtle 3.1 $\mu$m feature is consistent with crystalline water ice in larger grains. A Hapke-style model dominated by large ($D_{eff.} = 5.9$ $\mu$m) dust grains with a volumetric ice fraction of $f_{ice} = 33\%$ fits the spectrum. A thermal model incorporating 450P's orbital history since $\sim$1500 CE aligns with the observed onset of activity driven by $CO_2$ outgassing from amorphous water ice crystallization between 140-160 K.

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arXiv2026

Emerging Diversity Among the Main-Belt Comets: Insights from JWST and Ground-Based Observations of 457P/Lemmon-PANSTARRS

We present JWST NIRSpec and NIRCam observations of 457P/Lemmon-PANSTARRS, a main-belt comet that displayed activity around its 2020 perihelion and that was observed to regain activity during its 2024 perihelion by a ground-based observing campaign. The previous successful measurements of water production from two main-belt comets by the JWST NIRSpec instrument confirmed the hypothesis that H2O reservoirs are responsible for activity in dynamically stable main-belt comets. However, the main-belt comets observed with JWST thus far, 238P/Read and 358P/PANSTARRS, occupy orbits in the outer main-belt, with main-belt comets with smaller semi-major axes not yet sensitively tested for H2O. We find that despite clearly displaying dust activity in both ground-based and JWST imaging over a broad period, there were no corresponding H2O, CO, CO2, or CH3OH emissions within sensitive upper limits; notable given 457P is the first main-belt comet with a semi-major axis within the 5:2 mean-motion resonance with Jupiter. We show that we were sensitive to production rates of gas predicted by the dust/gas ratios of 238P and 358P, and hypothesize that 457P may be more depleted than its companions; Q(H2O) must be less than 2x10^24 molecules/s, or 0.035 kg/s. Further surveying of main-belt comets across the parameter space of semi-major axis and eccentricity will shed light on whether 457P represents an edge member of a spectrum or a distinct subclass of main-belt comets.

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arXiv2026

Characterization of the Volatile Properties of 133P/Elst-Pizarro and Other Main-Belt Comets with JWST and Ground-Based Observations

We report results from an analysis of the volatile composition and evolution of main-belt comet (MBC) 133P/Elst-Pizarro using JWST NIRSpec and NIRCam observations and ground-based observations during its 2024 active apparition, and also assess the body of JWST MBC observations acquired to date. Using NIRSpec, we measure water vapor outgassing rates at two points in 133P's orbit, finding Q(H2O)=(1.9+/-0.6)x10^25 molecules/s on UT 2024 June 12 (at a true anomaly of nu=8 deg and heliocentric distance of rh=2.674 au), and Q(H2O)=(1.4+/-0.4)x10^25 molecules/s on UT 2024 October 14 (at nu=37.4 deg and rh=2.747 au). These measurements nominally represent a decline of ~25% in Q(H2O) between the visits, although they are also consistent with no change within uncertainties. We do not detect CO, CO2, or CH3OH, placing 133P's hypervolatile depletion (Q(CO2)/Q(H_2O)<0.009) at a similar level found for previously observed MBCs. We find log(Afrho/Q(H2O)) values for the three MBCs for which water vapor outgassing has been successfully detected that are consistent within uncertainties with an average value of log(Afrho/Q(H2O))=-24.6+/-0.2. Lastly, we find no clear correlations of water production rates with nucleus size, semimajor axis, or heliocentric distance among MBCs observed by JWST so far, but would particularly encourage future JWST observations of additional MBCs interior to the 5A:2J MMR with Jupiter and at high inclinations, as well as multiple observations of MBCs during single active apparitions to further investigate areas of interest identified from the current sample of JWST-observed MBCs.

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arXiv2026

NEO Colors from The Mission Accessible Near-Earth Object Survey (MANOS)

We present spectro-photometric griz colors for 189 near-Earth objects (NEOs) collected by the Mission Accessible Near-Earth Object Survey (MANOS). Data acquisition involved non-simultaneous multi-band exposures, thus particular attention was given to the influence of rotational lightcurves on the derived colors. We show that colors measured without accounting for lightcurve variations can significantly influence results for individual objects and potentially have systematic offsets for ensemble studies. Color-based taxonomic classifications were used to investigate the distribution of spectral types. Our results were combined with other visible wavelength surveys to highlight a previously reported change in the observed taxonomic distribution of NEOs as a function of size, namely a decrease in S complex and an increase in X complex objects with increasing absolute magnitude. Plausibility arguments are given to suggest that Main Belt source region, thermal modification, discovery bias, tidal resurfacing, regolith grain size, and impact shock darkening are unlikely explanations for this size-dependent trend. Consistent with recent NEO population models and work on the connection between meteorites and young asteroid families in the Main Belt, this trend is best explained by a compositional gradient in the NEO population. In particular, the observed abundance of S complex or ordinary chondrite-like NEOs decreases by a factor of two from ~65% of the population at km-scales down to a third at sizes <50m. This result has implications for understanding the initial pre-impact population of meteorite parent bodies prior to atmospheric filtering. Furthermore, this will have implications for probabilistic impact risk assessment models.

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arXiv2025

Catastrophic disruption of asteroid 2023 CX1 and implications for planetary defense

Mitigation of the threat from airbursting asteroids requires an understanding of the potential risk they pose for the ground. How asteroids release their kinetic energy in the atmosphere is not well understood due to the rarity of significant impacts. Ordinary chondrites, in particular L chondrites, represent a frequent type of Earth-impacting asteroids. Here, we present the first comprehensive, space-to-lab characterization of an L chondrite impact. Small asteroid 2023 CX1 was detected in space and predicted to impact over Normandy, France, on 13 February 2023. Observations from multiple independent sensors and reduction techniques revealed an unusual but potentially high-risk fragmentation behavior. The nearly spherical 650 $\pm$ 160 kg (72 $\pm$ 6 cm diameter) asteroid catastrophically fragmented around 28 km altitude, releasing 98% of its total energy in a concentrated region of the atmosphere. The resulting shockwave was spherical, not cylindrical, and released more energy closer to the ground. This type of fragmentation increases the risk of significant damage at ground level. These results warrant consideration for a planetary defense strategy for cases where a >3-4 MPa dynamic pressure is expected, including planning for evacuation of areas beneath anticipated disruption locations.

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arXiv2025

Near-Discovery Observations of Interstellar Comet 3I/ATLAS with the NASA Infrared Telescope Facility

Interstellar Objects are comets and asteroids that formed around other stars but were ejected before they could accrete into exoplanets. They therefore represent a rare opportunity to compare the building blocks of planets in the Solar System to those in other stellar systems. The third Interstellar Object, 3I/ATLAS, is the newest, brightest, potentially largest, and fastest member of this population. We report observations of 3I/ATLAS taken on 2025 July 3 and 4 with the NASA Infrared Telescope Facility just days after its discovery. In r'-band imaging with 'Opihi, we see no obvious lightcurve variability and derive a g'-i' color of 0.98+/-0.03 which is consistent in spectral slope to other near-discovery observations. We obtained the first near-infrared (NIR) reflectance spectrum of 3I/ATLAS with SpeX. The visible color and NIR spectrum show a linear, red visible slope, a somewhat less red slope between 0.7 and 1.1 $\mu{m}$, and a neutral or slightly blue slope at longer wavelengths. Challenges in modeling the reflectivity of 3I may indicate that this comet has a complex grain size distribution, grain compositions unlike Solar system comets, or both. Like 2I/Borisov, there are no obvious signatures of water ice in the coma of 3I/ATLAS. Observations closer to perihelion will help elucidate whether 3I has less water than anticipated or whether the Interstellar Objects might retain and release their ices somewhat differently than Solar System comets do.

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arXiv2025

Discovery and Preliminary Characterization of a Third Interstellar Object: 3I/ATLAS

We report initial observations aimed at the characterization of a third interstellar object. This object, 3I/ATLAS or C/2025 N1 (ATLAS), was discovered on 2025 July 1 UT and has an orbital eccentricity of $e\sim6.1$, perihelion of $q\sim 1.36$ au, inclination of $\sim175^\circ$, and hyperbolic velocity of $V_\infty\sim 58$ km s$^{-1}$. We report deep stacked images obtained using the Canada-France-Hawaii Telescope and the Very Large Telescope that resolve a compact coma. Using images obtained from several smaller ground-based telescopes, we find minimal light curve variation for the object over a $\sim4$ day time span. The visible/near-infrared spectral slope of the object is 17.1$\pm$0.2 %/100 nm, comparable to other interstellar objects and primitive solar system small bodies (comets and D-type asteroids). 3I/ATLAS will be observable through early September 2025, then unobservable by Earth-based observatories near perihelion due to low solar elongation. It will be observable again from the ground in late November 2025. Although this limitation unfortunately prohibits detailed Earth-based observations at perihelion when the activity of 3I/ATLAS is likely to peak, spacecraft at Mars could be used to make valuable observations at this time.

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arXiv2025

Activity-Induced Near-Infrared Variability at 29P/Schwassmann-Wachmann 1, 2017-2022

29P/Schwassmann-Wachmann 1 (SW1) is both the first-discovered active Centaur and the most outburst-prone comet known. The nature of SW1's many outbursts, which regularly brighten the comet by five magnitudes or more, and what processes power them has been of particular interest since SW1's discovery in the 1920s. In this paper, we present and model four epochs of low-resolution near-infrared spectroscopy of SW1 taken with the NASA Infrared Telescope Facility and Lowell Discovery Telescope between 2017 and 2022. This dataset includes one large outburst, two periods of low activity ("quiescence" or "quiescent activity"), and one mid-sized outburst a few days after one of the quiescent observations. The two quiescent epochs appear similar in both spectral slope and modeled grain size distributions, but the two outbursts are significantly different. We propose that the two can be reconciled if smaller dust grains are accelerated more than larger ones, such that observations closer to the onset of an outburst are more sensitive to the finer-grained dust on the outside of the expanding cloud of material. These outbursts can thus appear very rapid but there is still a period in which the dust and gas are well-coupled. We find no strong evidence of water ice absorption in any of our spectra, suggesting that the areal abundance of ice-dominated grains is less than one percent. We conclude with a discussion of future modeling and monitoring efforts which might be able to further advance our understanding of this object's complicated activity patterns.

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arXiv2025

JWST sighting of decameter main-belt asteroids and view on meteorite sources

Asteroid discoveries are essential for planetary-defense efforts aiming to prevent impacts with Earth, including the more frequent megaton explosions from decameter impactors. While large asteroids ($\geq$100 km) have remained in the main belt since their formation, small asteroids are commonly transported to the near-Earth object (NEO) population. However, due to the lack of direct observational constraints, their size-frequency distribution--which informs our understanding of the NEOs and the delivery of meteorite samples to Earth--varies significantly among models. Here, we report 138 detections of the smallest asteroids ($\gtrapprox $10 m) ever observed in the main belt, which were enabled by JWST's infrared capabilities covering the asteroids' emission peaks and synthetic tracking techniques. Despite small orbital arcs, we constrain the objects' distances and phase angles using known asteroids as proxies, allowing us to derive sizes via radiometric techniques. Their size-frequency distribution exhibits a break at ${\sim}100$ m (debiased cumulative slopes of $q = -2.66\pm0.60$ and $-0.97\pm0.14$ for diameters smaller and larger than $\sim $100 m, respectively), suggestive of a population driven by collisional cascade. These asteroids were sampled from multiple asteroid families--most likely Nysa, Polana and Massalia--according to the geometry of pointings considered here. Through additional long-stare infrared observations, JWST is poised to serendipitously detect thousands of decameter-scale asteroids across the sky, probing individual asteroid families and the source regions of meteorites "in-situ".

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arXiv2024

On The Lunar Origin of Near-Earth Asteroid 2024 PT5

The Near-Earth Asteroid (NEA) 2024 PT5 is on an Earth-like orbit which remained in Earth's immediate vicinity for several months at the end of 2024. PT5's orbit is challenging to populate with asteroids originating from the Main Belt and is more commonly associated with rocket bodies mistakenly identified as natural objects or with debris ejected from impacts on the Moon. We obtained visible and near-infrared reflectance spectra of PT5 with the Lowell Discovery Telescope and NASA Infrared Telescope Facility on 2024 August 16. The combined reflectance spectrum matches lunar samples but does not match any known asteroid types -- it is pyroxene-rich while asteroids of comparable spectral redness are olivine-rich. Moreover, the amount of solar radiation pressure observed on the PT5 trajectory is orders of magnitude lower than what would be expected for an artificial object. We therefore conclude that 2024 PT5 is ejecta from an impact on the Moon, thus making PT5 the second NEA suggested to be sourced from the surface of the Moon. While one object might be an outlier, two suggest that there is an underlying population to be characterized. Long-term predictions of the position of 2024 PT5 are challenging due to the slow Earth encounters characteristic of objects in these orbits. A population of near-Earth objects which are sourced by the Moon would be important to characterize for understanding how impacts work on our nearest neighbor and for identifying the source regions of asteroids and meteorites from this under-studied population of objects on very Earth-like orbits.

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arXiv2024

Telescope-to-Fireball Characterization of Earth Impactor 2022 WJ1

Comparing how an asteroid appears in space to its ablation behavior during atmospheric passage and finally to the properties of associated meteorites represents the ultimate probe of small near-Earth objects. We present observations from the Lowell Discovery Telescope and from multiple meteor camera networks of 2022 WJ1, an Earth impactor which was disrupted over the North American Great Lakes on 19 November 2022. As far as we are aware, this is only the second time an Earth impactor has been specifically observed in multiple passbands prior to impact to characterize its composition. The orbits derived from telescopic observations submitted to the Minor Planet Center (MPC) and ground-based meteor cameras result in impact trajectories that agree to within 40 meters, but no meteorites have been found as of yet. The telescopic observations suggest a silicate-rich surface, and thus a moderate-to-high albedo, which results in an estimated size for the object of just D = 40 - 60 cm. Modeling the fragmentation of 2022 WJ1 during its fireball phase also suggests an approximate half-meter original size for the object as well as an ordinary chondrite-like strength. These two lines of evidence both support that 2022 WJ1 was likely an S-type condritic object and the smallest asteroid compositionally characterized in space. We discuss how best to combine telescopic and meteor camera datasets, how well these techniques agree, and what can be learned from studies of ultra-small asteroids.

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arXiv2024

The population of small near-Earth objects: composition, source regions and rotational properties

The study of small ($<$300 m) near-Earth objects (NEOs) is important because they are more closely related than larger objects to the precursors of meteorites that fall on Earth. Collisions of these bodies with Earth are also more frequent. Although such collisions cannot produce massive extinction events, they can still produce significant local damage. Here we present the results of a photometric and spectroscopic survey of small NEOs, which include near-infrared (NIR) spectra of 84 objects with a mean diameter of 126 m and photometric data of 59 objects with a mean diameter of 87 m. We found that S-complex asteroids are the most abundant among the NEOs, comprising $\sim$66\% of the sample. Most asteroids in the S-complex were found to have compositions consistent with LL-chondrites. Our study revealed the existence of NEOs with spectral characteristics similar to those in the S-complex, but that could be hidden within the C- or X-complex due to their weak absorption bands. We suggest that the presence of metal or shock-darkening could be responsible for the attenuation of the absorption bands. These objects have been grouped into a new subclass within the S-complex called Sx-types. The dynamical modeling showed that 83\% of the NEOs escaped from the $ν_{6}$ resonance, 16\% from the 3:1 and just 1\% from the 5:2 resonance. Lightcurves and rotational periods were derived from the photometric data. No clear trend between the axis ratio and the absolute magnitude or rotational period of the NEOs was found.

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arXiv2024

Jupiter Co-Orbital Comet P/2023 V6 (PANSTARRS): Orbital History and Modern Activity State

The discovery of the transient Jupiter co-orbital comet P/2019 LD2 (ATLAS) drew significant interest. Not only will LD2 transition between being a Centaur and a Jupiter Family Comet (JFC) in 2063, the first time this process can be observed as it happens, it is also very active for its large heliocentric distance. We present observations and orbital integrations of the newly discovered transient Jupiter co-orbital comet P/2023 V6 (PANSTARRS), the second such object known. Despite similar modern orbits, V6 is significantly (15 times) less active than LD2 and most JFCs as determined via Afrho measurements at the same heliocentric distance. We find V6 is co-orbital between 2020 and 2044, twice the duration of LD2, but it will not become a JFC soon. We interpret these differences in activity as evolutionary, with V6 having lost a significant fraction of its near-surface ice compared to LD2 by previously being warmer. While V6's pre-encounter orbit was somewhat warmer than LD2's, future thermal modeling will be needed to understand if this can explain their differences or if a more significant difference further into the past is required. This is more evidence that LD2 is a pristine and ice-rich object, and thus it may display very strong activity when it becomes a JFC. We sue the differences between V6 and LD2 to discuss the interpretation of cometary activity at large heliocentric distances as well as the small end of the crater record of the Galilean Satellites. Continuing observations of both objects are highly encouraged.

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arXiv2023

Photometry of the Didymos system across the DART impact apparition

On 26 September 2022, the Double Asteroid Redirection Test (DART) spacecraft impacted Dimorphos, the satellite of binary near-Earth asteroid (65803) Didymos. This demonstrated the efficacy of a kinetic impactor for planetary defense by changing the orbital period of Dimorphos by 33 minutes (Thomas et al. 2023). Measuring the period change relied heavily on a coordinated campaign of lightcurve photometry designed to detect mutual events (occultations and eclipses) as a direct probe of the satellite's orbital period. A total of 28 telescopes contributed 224 individual lightcurves during the impact apparition from July 2022 to February 2023. We focus here on decomposable lightcurves, i.e. those from which mutual events could be extracted. We describe our process of lightcurve decomposition and use that to release the full data set for future analysis. We leverage these data to place constraints on the post-impact evolution of ejecta. The measured depths of mutual events relative to models showed that the ejecta became optically thin within the first ~1 day after impact, and then faded with a decay time of about 25 days. The bulk magnitude of the system showed that ejecta no longer contributed measurable brightness enhancement after about 20 days post-impact. This bulk photometric behavior was not well represented by an HG photometric model. An HG1G2 model did fit the data well across a wide range of phase angles. Lastly, we note the presence of an ejecta tail through at least March 2023. Its persistence implied ongoing escape of ejecta from the system many months after DART impact.

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arXiv2023

Ejecta Evolution Following a Planned Impact into an Asteroid: The First Five Weeks

The impact of the DART spacecraft into Dimorphos, moon of the asteroid Didymos, changed Dimorphos' orbit substantially, largely from the ejection of material. We present results from twelve Earth-based facilities involved in a world-wide campaign to monitor the brightness and morphology of the ejecta in the first 35 days after impact. After an initial brightening of ~1.4 magnitudes, we find consistent dimming rates of 0.11-0.12 magnitudes/day in the first week, and 0.08-0.09 magnitudes/day over the entire study period. The system returned to its pre-impact brightness 24.3-25.3 days after impact through the primary ejecta tail remained. The dimming paused briefly eight days after impact, near in time to the appearance of the second tail. This was likely due to a secondary release of material after re-impact of a boulder released in the initial impact, through movement of the primary ejecta through the aperture likely played a role.

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