arXiv subjects

Eleanor K. Sansom

Publications and source records attributed to Eleanor K. Sansom.

At least 19 recordsLinked to original sources

arXiv2026

A Cloud-Based Tool for Meteorite Recovery Using Drones and Machine Learning

We present a cloud-based tool that uses drones and machine learning to help recover instrumentally observed meteorite falls. We showcase a collection of improvements made upon previous iterations of our system, as well as detail the successes and limitations of this technique when applied to observed meteorite falls in South and Western Australia. This tool is available to the meteoritics research community upon request at https://find.gfo.rocks.

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arXiv2026

The Desert Fireball Network Clear-Sky Survey

Estimating the meteoroid flux density at centimetre to metre sizes is notoriously difficult. Yet it is an important endeavour, as these sizes represent the transition between small meteoroids that pose a risk to spacecraft, and the Near-Earth Objects that are relevant for planetary defense. We present a novel automated methodology for debiasing meteor observations from multi-camera networks, applied to data from the Desert Fireball Network (DFN). Our approach utilizes the Hierarchical Equal Area isoLatitude Pixelisation (HEALPix) framework to partition the sky into equal-area pixels at 70 km altitude, enabling precise and convenient measurement of effective survey coverage and fireball counting across the network. We developed a comprehensive data processing pipeline that analyses millions of all-sky camera images to determine clear-sky conditions through automated star source detection and flux distribution analysis. As a case study, we apply this methodology to observations of the 2015 Southern Taurid meteor shower, during which there was significant fireball activity. Processing data from 33 cameras over a three-month period (October-December 2015), we calculate an effective observation coverage of $1.58 \times 10^{12}$ km$^2$.h and identified 54 Southern Taurid fireballs from 141 validated detections. Our results are consistent with the extrapolation of previous work done on the same meteor shower at smaller sizes, when we set a $\sim300$ kg.m$^{-3}$ mean meteoroid density, consistent with the cometary origin of the Taurid stream. The HEALPix-based approach successfully automates what was previously a labor-intensive manual process, providing a scalable solution for accurate flux measurements from distributed camera networks; it is directly applicable to other meteor surveys.

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arXiv2025

A Near-Earth Object Model Calibrated to Earth Impactors

The population of Earth-impacting meteoroids and its size-dependent orbital elements are key to understanding the origin of meteorites and informing on planetary defence efforts. Outstanding questions include the role of collisions in depleting meteoroids on highly evolved orbits and the relative importance of delivery resonances. Those depend on size, with current dynamical models considering only asteroids larger than 10m in diameter. Based on 1,202 sporadic meteoroids observed by the Global Fireball Observatory, we created a debiased model of the near-Earth meteoroid population in the 10g - 150kg in size (approximately 1cm - 0.5m) as they dynamically evolved from the main asteroid belt onto Earth-crossing orbits. The observed impact population is best matched with a collisional half-life decreasing from 3Myr for meteoroids of 0.6kg (7cm) or higher, to 1Myr below this size, extending to the model lower bound of 10g. Placing our results in context with near-Earth object models for larger sizes, we find that the inner main belt continues to dominate feeding the small 1m to 10m diameter population primarily via the $ν_6$ secular resonance and the 3:1J mean motion resonance. We also evaluated the potential significance of physical processes other than collisions on Earth-impacting meteoroids, such as low-perihelion disruptions from thermal stresses.

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arXiv2025

Exploring Seismic Signal Detection and Source Identification of Atmospheric Entries: The Hayabusa2 Sample Return Capsule as a Benchmark

This exploratory study investigates whether seismic signals can be used to infer fragmentation during a fireball event. Re-entry objects, particularly sample return capsules (SRCs) such as the one from the Hayabusa2 mission, behave similarly to slow meteors during atmospheric entry and provide valuable insights into natural fireball events. In this study, we initially analyse seismic signals from the Hayabusa2 SRC re-entry, which took place on December 5, 2020, over South Australia. The SRC's signature was captured by a dense network of seismic stations (Eakin, 2018; O'Donnell et al., 2020), offering a unique opportunity to investigate the signals' characteristics and verify their connection to the re-entry event. The ballistic trajectory was confirmed as the source shock mechanism for this event. We isolate this signal and use it as a reference for a ballistic shock signature and compare it to three other fireball case studies, including a suborbital re-entry and two natural meteoroids. Although factors such as local geology and atmospheric conditions were not considered in this preliminary study, our results show promise, with high correlations for events with purely ballistic trajectories and lower correlations for those involving fragmentation or airbursts. This implies that seismic data may be able to disambiguate whether any particular fireball event underwent significant fragmentation or airburst, key phenomena for assessing body strengths.

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arXiv2025

Perihelion history and atmospheric survival as primary drivers of the Earth`s meteorite record

Models predict that more than half of all impacting meteoroids should be carbonaceous, reflecting the abundance of carbon-rich asteroids in the main belt and near-Earth space. Yet carbonaceous chondrites represent only about 4% of meteorites recovered worldwide. Here we analyse 7,982 meteoroid impacts and 540 potential meteorite falls from 19 global observation networks and demonstrate that intense thermal stress at low perihelion distances coupled with the filtering effect of Earth`s atmosphere explains this mismatch. Meteoroids repeatedly subjected to intense thermal cycling near the Sun fracture and weaken, removing the most friable objects even before atmospheric entry. Our data also show that tidally disrupted meteoroid streams produce especially fragile fragments that rarely survive to the ground. Consequently, compact, higher-strength, thermally cycled bodies dominate the meteorite record. These findings reconcile the predicted carbonaceous flux with its scarcity in collections, underscoring how orbital evolution and atmospheric filtering shape the materials that reach Earth`s surface.

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arXiv2024

The Arpu Kuilpu Meteorite: In-depth characterization of an H5 chondrite delivered from a Jupiter Family Comet orbit

Over the Nullarbor Plain in South Australia, the Desert Fireball Network detected a fireball on the night of 1 June 2019 (7:30 pm local time), and six weeks later recovered a single meteorite (42 g) named Arpu Kuilpu. This meteorite was then distributed to a consortium of collaborating institutions to be measured and analyzed by a number of methodologies including: SEM-EDS, EPMA, ICP-MS, gamma-ray spectrometry, ideal gas pycnometry, magnetic susceptibility measurement, μCT, optical microscopy, and accelerator and noble gas mass spectrometry techniques. These analyses revealed that Arpu Kuilpu is an unbrecciated H5 ordinary chondrite, with minimal weathering (W0-1) and minimal shock (S2). The olivine and pyroxene mineral compositions (in mol%) are Fa: 19.2 +- 0.2, and Fs: 16.8 +- 0.2, further supporting the H5 type and class. The measured oxygen isotopes are also consistent with an H chondrite (δ17O = 2.904 +- 0.177; δ18O = 4.163 +- 0.336; Δ17O = 0.740 +- 0.002). Ideal gas pycnometry measured bulk and grain densities of 3.66 +- 0.02 and 3.77 +- 0.02 g cm-3, respectively, yielding a porosity of 3.0 % +- 0.7. The magnetic susceptibility of this meteorite is log X = 5.16 +- 0.08. The most recent impact-related heating event experienced by Arpu Kuilpu was measured by 40Ar/39Ar chronology to be 4467 +- 16 Ma, while the cosmic ray exposure age is estimated to be between 6-8 Ma. The noble gas isotopes, radionuclides, and fireball observations all indicate that Arpu Kuilpu's meteoroid was quite small (maximum radius of 10 cm, though more likely between 1-5 cm). Although this meteorite is a rather ordinary ordinary chondrite, its prior orbit resembled that of a Jupiter Family Comet (JFC) further lending support to the assertion that many cm- to m-sized objects on JFC orbits are asteroidal rather than cometary in origin.

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arXiv2024

Seismic and acoustic signals from the 2014 'Interstellar Meteor'

We conduct a thorough analysis of seismic and acoustic data from the so-called `Interstellar Meteor' which entered the Earth's atmosphere off the coast of Papua New Guinea on 2014-01-08. We conclude that both previously-reported seismic signals are spurious -- one has characteristics suggesting a local vehicular-traffic based origin; whilst the other is statistically indistinguishable from the background noise. As such, previously-reported localisations based on this data are spurious. Analysis of acoustic data provides a best fit location estimate which is very far ($\sim$170~km) from the reported fireball location. Accordingly, we conclude that material recovered from the seafloor and purported to be from the meteor is almost certainly unrelated to it, and is likely of more mundane (non-interstellar) origin.

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arXiv2023

The Golden Meteorite Fall: Fireball Trajectory, Orbit and Meteorite Characterization

The Golden (British Columbia, Canada) meteorite fall occurred on Oct 4, 2021 at 0534 UT with the first recovered fragment (1.3 kg) landing on an occupied bed. The meteorite is an unbrecciated, low-shock (S2) ordinary chondrite of intermediate composition, typed as an L/LL5. From noble gas measurements the cosmic ray exposure age is 25 Ma while gas retention ages are all >2 Ga. Short-lived radionuclides and noble gas measurements of the pre-atmospheric size overlap with estimates from infrasound and lightcurve modelling producing a preferred pre-atmospheric mass of 70-200 kg. The orbit of Golden has a high inclination (23.5 degs) and is consistent with delivery from the inner main belt. The highest probability (60%) of an origin is from the Hungaria group. We propose that Golden may originate among the background S-type asteroids found interspersed in the Hungaria region. The current collection of 18 L and LL chondrite orbits shows a strong preference for origins in the inner main belt, suggesting multiple parent bodies may be required to explain the diversity in CRE ages and shock states.

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arXiv2023

The Winchcombe Fireball -- that Lucky Survivor

On February 28, 2021, a fireball dropped $\sim0.6$ kg of recovered CM2 carbonaceous chondrite meteorites in South-West England near the town of Winchcombe. We reconstruct the fireball's atmospheric trajectory, light curve, fragmentation behaviour, and pre-atmospheric orbit from optical records contributed by five networks. The progenitor meteoroid was three orders of magnitude less massive ($\sim13$ kg) than any previously observed carbonaceous fall. The Winchcombe meteorite survived entry because it was exposed to a very low peak atmospheric dynamic pressure ($\sim0.6$ MPa) due to a fortuitous combination of entry parameters, notably low velocity (13.9 km/s). A near-catastrophic fragmentation at $\sim0.07$ MPa points to the body's fragility. Low entry speeds which cause low peak dynamic pressures are likely necessary conditions for a small carbonaceous meteoroid to survive atmospheric entry, strongly constraining the radiant direction to the general antapex direction. Orbital integrations show that the meteoroid was injected into the near-Earth region $\sim0.08$ Myr ago and it never had a perihelion distance smaller than $\sim0.7$ AU, while other CM2 meteorites with known orbits approached the Sun closer ($\sim0.5$ AU) and were heated to at least 100 K higher temperatures.

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arXiv2022

Direct measurement of decimeter-sized rocky material in the Oort cloud

The Oort cloud is thought to be a reservoir of icy planetesimals and the source of long-period comets (LPCs) implanted from the outer Solar System during the time of giant planet formation. The abundance of rocky ice-free bodies is a key diagnostic of Solar System formation models as it can distinguish between ``massive" and ``depleted" proto-asteroid belt scenarios and thus disentangle competing planet formation models. Here we report a direct observation of a decimeter-sized ($\sim2$ kg) rocky meteoroid on a retrograde LPC orbit ($e \approx 1.0$, i = $121^{\circ}$). During its flight, it fragmented at dynamic pressures similar to fireballs dropping ordinary chondrite meteorites. A numerical ablation model fit produces bulk density and ablation properties also consistent with asteroidal meteoroids. We estimate the flux of rocky objects impacting Earth from the Oort cloud to be $1.08^{+2.81}_{-0.95} \mathrm{meteoroids/10^6 km^2/yr}$ to a mass limit of 10 g. This corresponds to an abundance of rocky meteoroids of $\sim6^{+13}_{-5}$\% of all objects originating in the Oort cloud and impacting Earth to these masses. Our result gives support to migration-based dynamical models of the formation of the Solar System which predict that significant rocky material is implanted in the Oort cloud, a result not explained by traditional Solar System formation models.

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arXiv2022

Minimoon still on the loose

On Aug 22, 2016, a bright fireball was observed by the Desert Fireball Network in South Australia. Its pre-atmosphere orbit suggests it was temporarily captured by the Earth-Moon system before impact. A search was conducted two years after the fall, and a meteorite was found after 6 days of searching. The meteorite appeared relatively fresh, had a mass consistent with fireball observation predictions, and was at the predicted location within uncertainties. However, the meteorite did show some weathering and lacked short-lived radionuclides ($^{58}$Co, $^{54}$Mn). A terrestrial age based on cosmogenic $^{14}$C dating was determined; the meteorite has been on the Earth's surface for $3.2\pm1.3$ kyr, ruling out it being connected to the 2016 fireball. Using an upper limit on the pleistieocene terrain age and the total searched area, we find that the contamination probability from another fall is $<2\%$. Thus, the retrieval of the "wrong" meteorite is at odds with the contamination statistics. This is a key example to show that fireball-meteorite pairings should be carefully verified.

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arXiv2022

Successful Recovery of an Observed Meteorite Fall Using Drones and Machine Learning

We report the first-time recovery of a fresh meteorite fall using a drone and a machine learning algorithm. A fireball on the 1st April 2021 was observed over Western Australia by the Desert Fireball Network, for which a fall area was calculated for the predicted surviving mass. A search team arrived on site and surveyed 5.1 km2 area over a 4-day period. A convolutional neural network, trained on previously-recovered meteorites with fusion crusts, processed the images on our field computer after each flight. meteorite candidates identified by the algorithm were sorted by team members using two user interfaces to eliminate false positives. Surviving candidates were revisited with a smaller drone, and imaged in higher resolution, before being eliminated or finally being visited in-person. The 70 g meteorite was recovered within 50 m of the calculated fall line using, demonstrating the effectiveness of this methodology which will facilitate the efficient collection of many more observed meteorite falls.

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arXiv2022

Arpu Kuilpu: An H5 from the Outer Main Belt

On 1 June 2019, just before 7:30 PM local time, the Desert Fireball Network detected a -9.3 magnitude fireball over South Australia near the Western Australia border. The event was observed by six fireball observatories, and lasted for five seconds. One station was nearly directly underneath the trajectory, greatly constraining the trajectory solution. This trajectory's backward numerical integrations indicate that the object originated from the outer main belt with a semi-major axis of 2.75 au. A light curve was also extracted and showed that the body experienced very little fragmentation during its atmospheric passage. A search campaign was conducted with several Desert Fireball Network team members and other volunteers. One 42 g fragment was recovered within the predicted fall area based on the dark flight model. Based on measurements of short-lived radionuclides, the fragment was confirmed to be a fresh fall. The meteorite, Arpu Kuilpu, has been classified as an H5 ordinary chondrite. This marks the fifth fall recovered in Australia by the Desert Fireball Network, and the smallest meteoroid ($\simeq 2$ kg) to ever survive entry and be recovered as a meteorite.

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arXiv2022

Trajectory, recovery, and orbital history of the Madura Cave meteorite

On the 19th June 2020 at 20:05:07 UTC, a fireball lasting 5.5 s was observed above Western Australia by three Desert Fireball Network observatories. The meteoroid entered the atmosphere with a speed of $14.00 \pm 0.17$ km s$^{-1}$ and followed a $58^{\circ}$ slope trajectory from a height of 75 km down to 18.6 km. Despite the poor angle of triangulated planes between observatories (29$^{\circ}$) and the large distance from the observatories, a well constrained kilo-size main mass was predicted to have fallen just South of Madura in Western Australia. However, the search area was predicted to be large due to the trajectory uncertainties. Fortunately, the rock was rapidly recovered along the access track during a reconnaissance trip. The 1.072 kg meteorite called Madura Cave was classified as an L5 ordinary chondrite. The calculated orbit is of Aten type (mostly contained within the Earth's orbit), the second time only a meteorite is observed on such an orbit after Bunburra Rockhole. Dynamical modelling shows that Madura Cave has been in near-Earth space for a very long time. The NEO dynamical lifetime for the progenitor meteoroid is predicted to be $\sim87$ Myr. This peculiar orbit also points to a delivery from the main asteroid belt via the $\nu6$ resonance, and therefore an origin in the inner belt. This result contributes to drawing a picture for the existence of a present-day L chondrite parent body in the inner belt.

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arXiv2021

Taurid stream #628: a reservoir of large cometary impactors

The Desert Fireball Network observed a significant outburst of fireballs belonging to the Southern Taurid Complex of meteor showers between October 27 and November 17, 2015. At the same time, the Cameras for Allsky Meteor Surveillance project detected a distinct population of smaller meteors belonging to the irregular IAU shower #628, the s-Taurids. While this returning outburst was predicted and observed in previous work, the reason for this stream is not yet understood. 2015 was the first year that the stream was precisely observed, providing an opportunity to better understand its nature. We analyse the orbital elements of stream members, and establish a size frequency distribution from millimetre to metre size range. The stream is highly stratified with a large change of entry speed along Earth's orbit. We confirm that the meteoroids have orbital periods near the 7:2 mean-motion resonance with Jupiter. The mass distribution of this population is dominated by larger meteoroids, unlike that for the regular Southern Taurid shower. The distribution index is consistent with a gentle collisional fragmentation of weak material. A population of metre-sized objects is identified from satellite observations at a rate consistent with a continuation of the size-frequency distribution established at centimetre size. The observed change of longitude of perihelion among the s-Taurids points to recent (a few centuries ago) activity from fragmentation involving surviving asteroid 2015TX24. This supports a model for the Taurid Complex showers that involves an ongoing fragmentation cascade of comet 2P/Encke siblings following a breakup some 20,000 years ago.

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arXiv2021

The main asteroid belt: the primary source of debris on comet-like orbits

Jupiter family comets contribute a significant amount of debris to near-Earth space. However, telescopic observations of these objects seem to suggest they have short physical lifetimes. If this is true, the material generated will also be short-lived, but fireball observation networks still detect material on cometary orbits. This study examines centimeter-meter scale sporadic meteoroids detected by the Desert Fireball Network from 2014-2020 originating from Jupiter family comet-like orbits. Analyzing each event's dynamic history and physical characteristics, we confidently determined whether they originated from the main asteroid belt or the trans-Neptunian region. Our results indicate that $<4\%$ of sporadic meteoroids on JFC-like orbits are genetically cometary. This observation is statistically significant and shows that cometary material is too friable to survive in near-Earth space. Even when considering shower contributions, meteoroids on JFC-like orbits are primarily from the main-belt. Thus, the presence of genuine cometary meteorites in terrestrial collections is highly unlikely.

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arXiv2019

Recreating the OSIRIS-REx Slingshot Manoeuvre from a Network of Ground-Based Sensors

Optical tracking systems typically trade-off between astrometric precision and field-of-view. In this work, we showcase a networked approach to optical tracking using very wide field-of-view imagers that have relatively low astrometric precision on the scheduled OSIRIS-REx slingshot manoeuvre around Earth on September 22nd, 2017. As part of a trajectory designed to get OSIRIS-REx to NEO 101955 Bennu, this flyby event was viewed from 13 remote sensors spread across Australia and New Zealand to promote triangulatable observations. Each observatory in this portable network was constructed to be as lightweight and portable as possible, with hardware based off the successful design of the Desert Fireball Network. Over a 4 hour collection window, we gathered 15,439 images of the night sky in the predicted direction of the OSIRIS-REx spacecraft. Using a specially developed streak detection and orbit determination data pipeline, we detected 2,090 line-of-sight observations. Our fitted orbit was determined to be within about 10~km of orbital telemetry along the observed 109,262~km length of OSIRIS-REx trajectory, and thus demonstrating the impressive capability of a networked approach to SSA.

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arXiv2019

A Dynamic Trajectory Fit to Multi-Sensor Fireball Observations

Meteorites with known orbital origins are key to our understanding of Solar System formation and the source of life on Earth. However, these pristine samples of space material are incredibly rare. Less than 40 of the 60,000 meteorites held in collections around the world have known dynamical origins. Fireball networks have been developed globally in a unified effort to increase this number by using multiple observatories to record, triangulate, and dynamically analyse ablating meteoroids as they enter our atmosphere. The accuracy of the chosen meteoroid triangulation method directly influences the accuracy of the determined orbit and the likelihood of possible meteorite recovery. There are three leading techniques for meteoroid triangulation discussed in the literature: the Method of Planes, the Straight Line Least Squares method, and the Multi-Parameter Fit method. Here we describe an alternative method to meteoroid triangulation, called the Dynamic Trajectory Fit. This approach uses the meteoroid's 3D dynamic equations of motion to fit a realistic trajectory directly to multi-sensor line-of-sight observations. This method has the ability to resolve fragmentation events, fit systematic observatory timing offsets, and determine mass estimates of the meteoroid along its observable trajectory. Through a comprehensive Monte-Carlo analysis of over 100,000 trajectory simulations, we find this new method to more accurately estimate meteoroid trajectories of slow entry events ($<$25\,km/s) and events observed from low convergence angles ($<$10$^{\circ}$) compared to existing meteoroid triangulation techniques. Additionally, we triangulate an observed fireball event with visible fragmentation using the various triangulation methods to show that the proposed Dynamic Trajectory Fit implementing fragmentation to best match the captured multi-sensor line-of-sight data.

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