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V Martín

Thread with a few selected #DARTMission animations from Farnham et al. "High-Speed Boulders and the Debris Field in DART Ejecta"
arxiv.org/abs/2506.16694

I have slowed down the animations to my liking, alt text is from the authors' descriptions. All original files available at
drum.lib.umd.edu/items/968963e

ZIP file: drum.lib.umd.edu/bitstreams/d2

h/t @michael_w_busch

🧵 1/4

arXiv.orgHigh-Speed Boulders and the Debris Field in DART EjectaOn 26 September 2022 the Double Asteroid Redirection Test (DART) spacecraft collided with Dimorphos, the moon of the near-Earth asteroid 65803 Didymos, in a full-scale demonstration of a kinetic impactor concept. The companion LICIACube spacecraft documented the aftermath, capturing images of the expansion and evolution of the ejecta from 29 to 243 s after the impact. We present results from our analyses of these observations, including an improved reduction of the data and new absolute calibration, an updated LICIACube trajectory, and a detailed description of the events and phenomena that were recorded throughout the flyby. One notable aspect of the ejecta was the existence of clusters of boulders, up to 3.6 m in radius, that were ejected at speeds up to 52 m/s. Our analysis of the spatial distribution of 104 of these boulders suggests that they are likely the remnants of larger boulders shattered by the DART spacecraft in the first stages of the impact. The amount of momentum contained in these boulders is more than 3 times that of the DART spacecraft, and it is directed primarily to the south, almost perpendicular to the DART trajectory. Recoil of Dimorphos from the ejection of these boulders has the potential to change its orbital plane by up to a degree and to impart a non-principal axis component to its rotation state. Damping timescales for these phenomena are such that the Hera spacecraft, arriving at the system in 2026, should be able to measure these effects.
Michael Busch

Today on the #arXiv:

Farnham et al. 2025, "High-Speed Boulders and the Debris Field in DART Ejecta" - arxiv.org/abs/2506.16694

#DARTMission science with predictions for the #HeraMission.

And demonstrating how things can go sideways in a collision.

arXiv.orgHigh-Speed Boulders and the Debris Field in DART EjectaOn 26 September 2022 the Double Asteroid Redirection Test (DART) spacecraft collided with Dimorphos, the moon of the near-Earth asteroid 65803 Didymos, in a full-scale demonstration of a kinetic impactor concept. The companion LICIACube spacecraft documented the aftermath, capturing images of the expansion and evolution of the ejecta from 29 to 243 s after the impact. We present results from our analyses of these observations, including an improved reduction of the data and new absolute calibration, an updated LICIACube trajectory, and a detailed description of the events and phenomena that were recorded throughout the flyby. One notable aspect of the ejecta was the existence of clusters of boulders, up to 3.6 m in radius, that were ejected at speeds up to 52 m/s. Our analysis of the spatial distribution of 104 of these boulders suggests that they are likely the remnants of larger boulders shattered by the DART spacecraft in the first stages of the impact. The amount of momentum contained in these boulders is more than 3 times that of the DART spacecraft, and it is directed primarily to the south, almost perpendicular to the DART trajectory. Recoil of Dimorphos from the ejection of these boulders has the potential to change its orbital plane by up to a degree and to impart a non-principal axis component to its rotation state. Damping timescales for these phenomena are such that the Hera spacecraft, arriving at the system in 2026, should be able to measure these effects.
Michael Busch

Today on the #arXiv :

López-Oquendo et al. 2025, "Thermal and Optical Characterization of Near-Earth Objects: Science Commissioning of the Recently Upgraded Mid-Infrared Camera MIRSI" - arxiv.org/abs/2506.13943

Including observations of Didymos before and after the #DARTMission impact.

Consistent with other observations of the ejecta (including from ALMA as detailed in Roth et al. 2023).

arXiv.orgThermal and Optical Characterization of Near-Earth Objects: Science Commissioning of the Recently Upgraded Mid-Infrared Camera MIRSI on the NASA Infrared Telescope FacilityMid-infrared (mid-IR) observations of Near-Earth Objects (NEOs) have historically been a valuable tool for understanding their physical properties. However, the current state of mid-IR instruments on ground-based telescopes places several limitations on performing thermal characterization of NEOs. The complexity of maintaining these instruments in operational conditions on telescopes has led to their decommissioning. Here, we present the first science commissioning observations out to 12.5 microns from the upgraded Mid-Infrared Spectrograph and Imager (MIRSI) at the NASA-IRTF. We obtained 42 observations of 31 NEOs and derived their diameters and albedos. Since MIRSI allows simultaneous optical observations with its MIRSI Optical Camera (MOC), we were able to determine the absolute magnitude for most of the targets at the time of the thermal acquisition. We present ejecta characterization for the Didymos system from observations made 11 hours and 9 days after the Double Asteroid Redirection Test (DART) impact. We present albedo and size measurements for (98943) Torifune 2001 CC21, the fly-by target of the Japanese Extended Hayabusa2 Mission. We also highlight several applications that the MIRSI system will provide for future airless body characterization, such as constraining thermal inertia from simultaneous optical and thermal lightcurves. This work also demonstrates the importance of having MIRSI as an available rapid-response instrument for planetary defense purposes.
Continued thread
*
Michael Busch

The last panel title is a reference to "The Expanse".

But Andy Cheng, lead investigator for the #DARTMission to demonstrate asteroid deflection, also previously worked on the NEAR Shoemaker mission to Eros.

So Eros did in fact change everything where asteroid science is concerned.

Michael Busch

Today on the #arXiv :

Langner et al. 2025, "Secondary impact debris in the Didymos system: what could be observed by Hera?" - arxiv.org/abs/2503.08158

Describing possibilities for the #HeraMission observing lingering debris from the #DARTMission impact hitting one of the asteroids.

arXiv.orgSecondary impact debris in the Didymos system: what could be observed by Hera?We investigate the effects of low--velocity impacts of rocks and boulders, originally released after the DART impact, on the surface of Didymos and the dynamics of dust particles released by those impacts. We determine if any of those effects can be observed by the Hera mission. The iSALE-2D shock physics code was used to simulate the re-impacts of boulders on the surface of the asteroid. To model the dynamics of the boulders, we used a numerical model that includes the gravity of non-spherical Didymos and Dimorphos, the solar gravity, and the radiation pressure. The sesquinary impacts can result in small, shallow craters on the surface of Didymos. For the given low impact speeds, the ejected mass depends mostly on the boulder mass. Ejection speeds range from 10 \% to 80 \% of the impact speed. The majority of the ejected dust falls back covering a large area of the surface, mostly at low/medium latitudes. Less than 20 \% of the ejected dust is escaping the system after a few days. The space surrounding the asteroids becomes free from dust after 15-30 days following each sesquinary impact. Results. The sesquinary impacts can result in small, shallow craters on the surface of Didymos. For the given low impact speeds, the ejected mass depends mostly on the boulder mass. Ejection speeds range from 10 \% to 80 \% of the impact speed. The majority of the ejected dust falls back covering a large area of the surface, mostly at low and medium latitudes. Less than 20 \% of the ejected dust is escaping the system after a few days. The space surrounding the asteroids becomes free from dust after 15-30 days following each sesquinary impact.
Michael Busch

Today on the #arXiv :

Richardson et al. 2025, "The Dynamical State of the Didymos System Before and After the DART Impact" - arxiv.org/abs/2502.14990

Reviewing the results of the #DARTMission impact.

"The largest uncertainty in the momentum transfer enhancement factor of the DART impact remains the mass of Dimorphos, which will be resolved by the #HeraMission ."

arXiv.orgThe Dynamical State of the Didymos System Before and After the DART ImpactNASA's Double Asteroid Redirection Test (DART) spacecraft impacted Dimorphos, the natural satellite of (65803) Didymos, on 2022 September 26, as a first successful test of kinetic impactor technology for deflecting a potentially hazardous object in space. The experiment resulted in a small change to the dynamical state of the Didymos system consistent with expectations and Level 1 mission requirements. In the pre-encounter paper Richardson (2022), predictions were put forward regarding the pre- and post-impact dynamical state of the Didymos system. Here we assess these predictions, update preliminary findings published after the impact, report on new findings related to dynamics, and provide implications for ESA's Hera mission to Didymos, scheduled for launch in 2024 with arrival in late December 2026. Pre-encounter predictions tested to date are largely in line with observations, despite the unexpected, flattened appearance of Didymos compared to the radar model and the apparent pre-impact oblate shape of Dimorphos (with implications for the origin of the system that remain under investigation). New findings include that Dimorphos likely became prolate due to the impact and may have entered a tumbling rotation state. A possible detection of a post-impact transient secular decrease in the binary orbital period suggests possible dynamical coupling with persistent ejecta. Timescales for damping of any tumbling and clearing of any debris are uncertain. The largest uncertainty in the momentum transfer enhancement factor of the DART impact remains the mass of Dimorphos, which will be resolved by the Hera mission.
Michael Busch

Today in the Planetary Science Journal:

Stickle et al. 2025, "Dimorphos's Material Properties and Estimates of Crater Size from the DART Impact" - iopscience.iop.org/article/10.

Estimating the crater diameter from the #DARTMission impact as 40-60 m and awaiting constraints by the #HeraMission .

As an aside:

This is why I wonder about the risk of the pending CNSA asteroid deflection demonstration shattering its target object.

iopscience.iop.orgRadware Bot Manager Captcha
Continued thread
Michael Busch

#DPS2024 and #TeamRadar continued:

@PlanetTreky et al., "On the Radar Detectability of Near-Earth Asteroid Surface Refreshing Processes" - submissions.mirasmart.com/DPS5

Zambrano-Marin et al., "Shape and Mutual Orbit Modeling of Binary Near-Earth Asteroid 2020 BX12" - submissions.mirasmart.com/DPS5

Naidu et al., "Orbital and physical characterization of asteroid Dimorphos following the DART impact" - submissions.mirasmart.com/DPS5

#DARTMission .

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