Europlanet Science Congress 2021
Virtual meeting
13 – 24 September 2021
Europlanet Science Congress 2021
Virtual meeting
13 September – 24 September 2021
Impact Processes in the Solar System


Impact Processes in the Solar System
Co-organized by OPS/SB
Convener: Elena Martellato | Co-conveners: Chrysa Avdellidou, Christopher Hamann, Isabel Herreros, Robert Luther, Jens Ormö
Mon, 20 Sep, 11:45–12:45 (CEST)

Session assets

Discussion on Slack

Oral and Poster presentations and abstracts

Chairpersons: Elena Martellato, Robert Luther, Isabel Herreros
Impact Flashes
Daniel Sheward, Anthony Cook, Chrysa Avdellidou, Marco Delbo, Bruno Cantarella, Luigi Zanatta, Stefano Sposetti, and Rafaello Lena


On 2017-09-27 at 18:56:12 UT a large meteoroid impacted the lunar surface, causing an impact flash with a duration of 1.12 seconds. Using Lunar Reconnaissance Orbiter Camera images, and the PyNAPLE (Python NAC Automatic Pair Lunar Evaluator) software pipeline, the resultant crater was identified. The crater is located at latitude φ= 8.0288, longitude λ = -76.546, approximately 14km east of the crater Glushko. The asymmetrical morphology of the ejecta blanket indicates the direction of impact was from the south, and impacting incidence angle was <30o.


Lunar impacts are monitored on a regular basis, by both amateur and professional groups [1,2,3]. Since the first confirmed recording of a lunar impact flash in 1999, at least 600 confirmed impact flashes have been observed.

This large volume of data has let to several studies on both the properties of the impactor, and the thermal evolution of the impact itself [4,5,6]. These studies make use of the observed brightness of the flash, and the most likely parent meteoroid stream to calculate the total energy and temperature of the impact, and estimate the resultant crater size.

Very few of these impact craters have located [7] however, as finding metre scale craters and linking them to an observed impact with certainty is difficult. By identifying the resultant crater from an observed impact flash, valuable ground truth data can be obtained to help constrain the energy of the impact through use of crater scaling laws. The ejecta pattern of the impact can also tell us important information about the trajectory of the impactor.


Impact Flash

At 18:56:10 UT on 2017-09-27, a meteoroid impacted the lunar surface. The impact was observed by SdR UAI Luna members Bruno Cantarella and Luigi Zanatta, using a dual telescope system capturing with ZWO ASI120MM cameras, running at 25fps in one telescope, and 30fps in the other. It was also confirmed to be observed by Stefano Sposetti in Gnosca, Switzerland, ruling out the possibility the flash being a false detection.

The flash lasted 29 frames in the 25fps camera, giving it a duration of 1.12s. The first 22 frames are shown in Fig. 1. Its peak luminosity is reached in the second frame after only 0.04s, with the peak quantum efficiency of the camera at 590nm.


Figure 1: The first 22 frames of the 2017-09-27 impact flash.

As there were no meteor streams active at the time of the impact, it is concluded that the impactor belonged to the sporadic meteor background.


Crater Detection

The PyNAPLE software [8] was utilised in order to search for the resultant impact crater in Lunar Reconnaissance Orbiter Narrow Angle Camera images (LRO NAC).

PyNAPLE works by searching for all before-after LRO NAC image pairs for a given time and location on the lunar surface, and running them through several operations which calibrate, map project, register, and align the images in order for pixel by pixel division to occur. This produces a final image in which similarities have cancelled out, and changes between the images are highlighted.

The crater, Fig. 2, was discovered in both LRO NAC images M1315871095R and M1344064055L, taken in 2019 and 2020 respectively, and and is absent from any images of the location from pre-2017.

Figure 2: The crater formed during the 2017-09-27 lunar impact. Left: The ‘before’ image M1180620010R. Centre: The ‘after’ image M1315871095R. Right: The resultant image from dividing M1315871095R by M1180620010R.


Crater Analysis

The ejecta blanket and newly exposed regolith are higher albedo than the surrounding undisturbed material. Consequently, in the current LROC images the fresh regolith is overexposed, and no measurements as the craters diameter can be made, although the extent of the ejecta can be measured up to 600m away from the point of impact. This prevents the calculation of impact energy by employing crater scaling laws at this time. As the LRO is still collecting images, however, once new images of the site get released, these calculations will be possible.

The ejecta blanket of the impact crater tells us some information on the impact. The asymmetrical morphology of the ejecta blanket, shown in Fig. 3, is formed by the meteoroid impacting with an angle below ~30o incidence, according to Shuvalov’s findings for projectiles below 100m in size [9]. The exclusion zone towards the bottom of the image containing no ejecta is indicative of the up-range direction of the impactor being towards the bottom of the image.

Knowing the direction of the impact is important as incidence angle plays a large part in a number of crater scaling laws [10], but also as a way to differentiate potential parent meteoroid streams if there were multiple possible candidates.


Figure 3: The cropped ratio image, with a threshold applied to highlight only the ejecta blanket.

The presence of smaller exclusion zones within the ejecta blanket are likely due to effects caused by the local terrain.


Future Work

Once new images of the crater are collected and released by the Lunar Reconnaissance Orbiter, a size measurement for the impact crater can be obtained. This will allow for the application of crater scaling laws to calculate the impacting kinetic energy, and to solve backwards through current impact flash methodologies.



[1] Madiedo et al (2010) Advances in Astronomy, 2010:167494

[2] Xilouris et al (2018) A&A , 619, A141

[3] Suggs et al (2008) Earth Moon and Planets, 102:293298

[4] Avdellidou and Vaubaillon (2019) MNRAS, 484, 5212-5222

[5] Madiedo et al (2018) MNRAS, 480, 5010-5016

[6] Bonanos et al (2018) A&A, 612, A76

[7] Suggs et al (2014) Icarus, 10.1016

[8] Sheward et al (2019) EPSC-DPS2019, Abstract 1032-1

[9] Shuvalov (2011) Meteoritics & Planetary Science, 11, 1713-1718

[10] Horedt and Neukum (1984) Earth moon and Planets, 31, 265-269

How to cite: Sheward, D., Cook, A., Avdellidou, C., Delbo, M., Cantarella, B., Zanatta, L., Sposetti, S., and Lena, R.: Lunar Surface Change Detection with PyNAPLE: The 2017-09-27 Lunar Impact Flash and Impact Crater, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-590,, 2021.

Mert Acar and Alper K. Ateş


A number of attempts have been done to detect of lunar impact flash observations by various researchers in last 20 years. One of the systematically research of lunar impact flash observations has been done at İSTEK Belde Observatory since 2017. We report the very first results of two first lunar impact flashes detected from Turkey.


Interplanetary space is full of meteoroids, cometary fragments and debris. Occasionaly these objects impact to the surface of the Moon at high velocities. During these events the kinetic energy of the impactor is converted to thermal energy and give out an optical signature detectable with small instruments. Impact flashes are rapid events that in most cases escape attantion due to low amount of signal. Monitoring the night side of the Moon increases capturing an impact flash due to higher contrast. For this reason impact observations are carried out between 5-10 and 20-25 ages of the Moon. Impact events are beneficial providing information on impact energy, impactor mass,  impactor source, temperature of the event [1,2,3,4,5,6]. We present the first report of two impact flashes on December 12, 2017 from Turkey.

Observation and method

ISTEK Belde Observatory (IBO) is located on the Asian shore of the historic Bosphorus waterway at 41o 01' 48'' N latitude and 29o 02' 32'' E longitude at an altitude of 150m. The observatory houses a Meade LX600 16'' Schmidt-Cassegrain f/8 telescope as the primary instrument. By using f3.3 focal reducer and Celestron Skyris 274M (1600×1200 px) monochrome camera, the telescope provides 24x30 arcminute field of view. The camera is operated at 15 fps. The time signal is acquired by network synchronisation. On 2017 December 12th a number of consecutive 10 minute observations each providing 9000 frames were inspected by LunarScan [7] and ZEPAZO software. Two impacts were detected and the signal is converted into visual magnitudes using MaximDL aperture photometry routine. For magnitude calculation three reference stars HD111662, HD111663 and HD111692 with known V magnitudes are used. These stars were within 1/4° from the impact sites and they were imaged in close succession with same air mass and exposure time. The impact flashes are detected at 82o.8 E, 8o.3 N (Flash 1) and 33o.7E , 16o.3N (Flash 2) selenographic coordinates. The photometric data are provided in Table 1 and location of flashes on the Moon are shown in Figure 1.


Figure1: Flash 1- 82o.8 E, 8o.3 N and  Flash 2 - 33o.7E , 16o.3N Selenographic coordinates.


Table 1: Information of lunar impact flashes.

  Flash 1 Flash 2
Time 04:19:30.866 04:20:04.400
Duration  0.533(s) 0.466(s)
Peak Magnitude 7.98 7.48
Radiated Energy (J) 1,96x106(J) 2.33x106(J)


Analysis and results

Magnitudes of the flashes are calculated using Pogson formula mf =ms+2,5log(fs/ff), where mf, ms are the magnitudes of the flash and the reference star respectively, fs and ff are the observed fluxes of the flash and the reference star. The peak magnitudes of the flashes are 7.98 and 7.48 for Flash 1 and Flash 2, respectively. The radiated power P, in watts m-2, of an impact flash can be calculated using P=κ x 10-M/2.5Δλ , where κ is the flux density in W m-2 µm-1for a magnitude 0 source (κ=3,75x10-8) [8], M is the aparent magnitude of the flash and Δλ is filter passband (Δλ=500nm), in µm. The observed energy Ed is calculated by integrating power equation with respect to time. The radiated energy which emitted as light on the lunar surface Er, can be estimate by means of the relation  Er=EdπƒR2 where R is the Earth-Moon distance (R=386605km), in m, when the flash occurs, f is a factor discribes the anisotropy degree of the light emission process (f=2 for the lunar surface and f=4 for the high altitude on the lunar soil)[9].  We conclude the observed events released energy  1,96x106 J and 2.33x106 J for Flash 1 and Flash2 respectively. These flashes are the first of their kind observed from Turkey; these event provided valuable insight on performance of the observatory instruments and reduction software. 


[1] Ortiz J. L., Aceituno F. J., Aceituno J., A search for meteoritic flashes on the Moon, A&A, 343, L57,1999.

[2] Ortiz J. L., Sada P. V., Bellot Rubio L. R., et al., Optical detection of meteoridal impacts on the MoonNature, 405, 921, Nature, 2000.

[3] Suggs R. M., Moser D. E., Cooke W. J., Suggs R. J., The flux kilogram-sized meteoroids from lunar impact monitoring, Icarus, 238, 23, 2014.

[4] Madiedo J. M., Ortiz J. L., Organero F., et al., Analysis of Moon impacrt flashes detected during the 2012 and 2013 Perseids, A&A, 577, A118, 201, 2015.

[5] Bonanos et al., NELIOTA: first temperature measurement of lunar impact flashes, A&A, 612, 2018.

[6] Madiedo, J.M., et al., First determination of the temperature of a lunar impact flash and its evolution, MNRAS, 480, 5010-5016, 2018.

[7] Gural, P. Meteoroid environments workshop, MSFC 2007.

[8] Bessel, M.S., Castelli, F., and Plez, B. 1998. Model atmospheres broad-band colors, bolometric corrections and temperature calibrations for O-M stars. A&A, 333, 231-250.

[9] Bellot Rubio, L. R., Ortiz, J. L., Sada, P. V., Luminous efficiency in hypervelocity impacts from the 1999 lunar Leonids, AJ, 542, L65, L68, 2000.


How to cite: Acar, M. and Ateş, A. K.: Two Successive Lunar Impact Flashes: First lunar impact detection from Turkey, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-498,, 2021.

Jose Maria Madiedo, Jose Luis Ortiz, Nicolas Morales, Pablo Santos-Sanz, Faustino Organero, Leonor Ana, and Fernando Fonseca


We present the contribution of our team to ESA's P3-NEO-I project, where we have been responsible for the detection and analysis of lunar impact flashes. These events provide key information about the impact processes taking place when meteoroids hit the Moon, and also allow to quantify the impact hazard of asteroids and comets for Earth. We also focus on the development of a new system for lunar impact flashes observations which has been deployed at the Calar Alto Observatory (Spain). This system can observe these events simultaneously in three different wavelengths by means of high-frame-rate and high-resolution CMOS cameras.

1. Introduction

The identification and analysis of flashes produced by the impact of meteoroids on the lunar surface is one of the techniques suitable for the study of the flux of interplanetary matter impacting the Earth. This method has the advantage that the area covered by one single detection instrument is much larger than the atmospheric volume monitored by meteor detectors on Earth.  Our team at the Institute of Astrophysics of Andalusia (IAA-CSIC) has been involved in the observation and analysis of these events since 1997 [1]. Since then, impact flashes have been unambiguously detected during the maximum activity period of several major meteor showers by using this technique, and flashes of sporadic origin have been also recorded [2].

For the detection of lunar impact flashes we have employed telescopes endowed with high-sensitivity CCD video cameras. Most of out telescopes are Schmidt-Cassegrain instruments with an aperture ranging between 28 to 50 cm, although some observational campaigns have been also performed with much larger instruments, such as, for instance, the 3.5 m telescope located at the Calar Alto Observatory [3].

During the last decade we have performed important improvements in the systems employed to detect these flashes. Most of these advances involved the use of faster cameras with higher resolution working at different wavelengths. In this work we focus on the systems employed by our team in the framework of ESA's P3NEOI project, and also on a new fast multiwavelength system deployed at the Calar Alto Observatory.

2. Contribution to the P3NEOI project

Since 2019 our team is member of a consortium of eight astronomical observatories leaded by the company Deimos Space, This consortium presented a technical proposal to the ESA ITT AO/1-9591/18/D/MR "P3NEOI: observational support from collaborating observatories". We are responsible for the work package (WP) dedicated to the detection and analysis of lunar impact flashes. One of the aims of this WP is the quantification of the flux of interplanetary matter that impacts our planet. For this purpose we have employed several telescopes located at three observatories in Spain: La Sagra, La Hita, and Sevilla. New instrumentation has been tested within this WP, including CMOS cameras with a maximum frame rate of 168 fps at full resolution (1920x1200 pixels). A sample impact flash recorded with one of these devices is shown in Figure 1. The main advantages of these cameras in relation to previously-employed imaging devices have been analyzed. One of their main utilities is related to their ability to obtain light curves with enhanced resolution. The monitoring in different wavelengths has also provided the temperature of lunar impact flashes.


Figure 1. Lunar impact flash recorded in the framework of the ESA P3NEOI project on 27 May 2020 at 20h48m49s UT, with a peak apparent magnitude of 5.5.

3. New instrumentation at CAHA

Our team has deployed a new telescope at the Calar Alto Observatory (Spain) and one of its goals is to observe lunar impact flashes. This instrument has an aperture of 60 cm and employs a set of high-speed CMOS cameras (with a frame rate of 300 fps) that can observe, simultaneously, at three different wavelengths: namely, I, V and R. The telescope, which has been founded by the Spanish Ministry for Science and Innovation, is located within a dedicated 4-m automated dome and works in a coordinated way with the rest of instruments we are currently employing at different observatories in our country. Figure 2 shows an image of this new instrument, which can be controlled remotely. This new telescope has implied an important step for the analysis of the collision of meteoroids with the lunar ground.


Figure 2. The new 60 cm telescope deployed at the Calar Alto Observatory.


[1] Ortiz, J.L. et al., J., 1999. A search for meteoritic flashes on the Moon. Astron. Astrophys. 343, L57–L60.

[2] J.L. Ortiz, et al., 2000, Optical detection of meteoroidal impacts on the Moon. Nature 405, 921–923.

[3] Madiedo J. M., Ortiz J. L., Yanagisawa M., Aceituno J. and Aceituno F. (2019b). "Impact flashes of meteoroids on the Moon". Meteoroids: Sources of Meteors on Earth and Beyond, Ryabova G. O., Asher D. J., and Campbell-Brown M. D. (eds.), Cambridge, UK. Cambridge University Press, ISBN 9781108426718, 2019, p. 136-158

How to cite: Madiedo, J. M., Ortiz, J. L., Morales, N., Santos-Sanz, P., Organero, F., Ana, L., and Fonseca, F.: Development of new systems for the observation of lunar impact flashes and the IAA participation in the ESA P3NEOI project, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-754,, 2021.

Jon Tandy, Vassilia Spathis, Penny Wozniakiewicz, and Luke Alesbrook


The intense, short-lived, self-luminous plume (or ‘impact flash’) produced from a hypervelocity impact is frequently observed on the lunar surface [1-4]. Laboratory measurements of these impact flashes (e.g. Figure 1) can also be acquired to determine parameters such as the target and impactor composition, or size/mass of the impactor [5-9]. Previous work has shown that the emission intensity from hypervelocity impacts tends to increase at higher impact velocities [10-15]. The relative intensity of atomic and molecular emission lines/bands originating from both projectile and target materials can also be used to determine approximate temperatures reached during impact [16-20].

Figure 1: Photograph of a hypervelocity impact flash from a 3 mm aluminium projectile impacting a water ice target at 4.51 km s-1.

Current understanding of icy Solar System bodies, such as Europa and Enceladus, suggests they may contain favourable environmental conditions to synthesise biologically significant molecules such as amino acids, fatty acids, sugars and heterocyclic bases. Ground-breaking impact experiments [21-24] have demonstrated that complex organic molecules can be formed during hypervelocity impact events that are ubiquitous throughout the Solar System. Consequently, laboratory impact flash measurements from icy targets can be utilised to constrain the temperatures required for the shock-synthesis of these biologically important species. This preliminary study utilises emission spectra for the temperature measurement of impacted salt-water ice using different projectile speeds and materials.


The University of Kent two-stage light-gas gun (LGG) [25] was used to horizontally accelerate a 3 mm aluminium or 4.3 mm Nylon projectile into salt-water ice targets composed of 20 g NaCl in 1 L of deionized water inside a sterilised 100 mm diameter, stainless steel container with their surfaces aligned at 90o to the shot line. Specific impact parameters for each experiment are summarised in Table 1.

Shot ID

Projectile Material

Impact Speed / km s-1


3 mm 7075 Aluminium



3 mm 7075 Aluminium



4.3 mm Nylon 6



4.3 mm Nylon 6


Table 1: Experimental parameters for impact flash measurements from salt-water ice targets.

The target mixture was frozen to -120 °C, with the temperature increasing to approximately -50 °C during the evacuation process of the LGG target chamber (to 50 mbar), prior to firing. A manual focus, 50 mm, F1.2, Nikon NIKKOR lens was aligned with the front viewport of the LGG target chamber and focused onto the end of a 0.5 mm internal diameter core of a fibre optic cable connected to an Ocean Insight Red Tide USB-650 spectrometer to record the impact flash spectrum.

Results and Conclusions

Figure 2 shows an example impact flash spectrum recorded using this methodology, with Na, Al and Zn atomic emission lines and AlO molecular bands clearly visible. The Al, AlO and Zn emission originate from the 7075 Al projectile (containing ~6% Zn). The relative intensities of the averaged Na 589 nm and 819 nm doublet emission lines originating from the target material were used to determine approximate peak temperatures for each impact experiment using a Boltzmann distribution calculation as outlined by Unnikrishnan et al. [26].

Figure 2: Impact flash emission spectrum from a 3 mm Al projectile impacting a salt-water ice target 6.03 km s-1. Labelled Na atomic lines were used for peak temperature determination.

All determined temperatures using this method were between 3000 K and 3420 K. Furthermore, shots 1 and 4, with similar impacts speeds, showed a small temperature difference of 140 K despite the distinctly different projectile material properties. This suggests that the calculated peak temperature is derived primarily from the target material. This observation may be a result of the method only utilising Na emission lines originating from the salt-water ice. Future work will constrain the calculated temperatures more precisely using spectra from shots at a wider range of impact speeds. These experiments should also provide an approximate correlation of impact energy and resulting temperature to be ascertained. Additional measurements with improved spectral resolution will further increase the precision of the determined temperatures and allow complimentary calculations using atomic emission lines originating from the projectile (e.g. the Al doublet at ~395 nm).


The authors thank the STFC for financially supporting this work and Mark Price for IDL support.


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How to cite: Tandy, J., Spathis, V., Wozniakiewicz, P., and Alesbrook, L.: Emission Spectroscopy for the Temperature Measurement of Salt-Water Ice during Hypervelocity Impact, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-630,, 2021.

Impacts & Atmospheric Entry
Matthias Van Ginneken, Steven Goderis, Natalia Artemieva, Vinciane Debaille, Sophie Decrée, Ralph Harvey, Katherine Huwig, Lutz Hecht, Shuying Yang, Felix Kaufmann, Bastien Soens, Munir Humayun, Flore Van Maldeghem, Matthew Genge, and Philippe Claeys

Introduction: Impactors several tens up to 200 m in size are likely to suffer complete disruption and to produce large airbursts, similarly to the Tunguska event over Russia in 1908 [e.g., 1]. Observations and numerical modeling of medium sized impacts producing large airbursts have shown that such impacts represent an important fraction of extraterrestrial matter accretion to Earth, with Tunguska-like events occurring every 100 to 10,000 years, which is notably more frequent than crater-forming impact events. However, little is known about occurrences of such airburst events in the geological record, principally because of the lack of readily identifiable evidences such as impact craters. Finding residues of such events is thus critical for assessing the complete impact history of the Earth. Here we present the discovery of extraterrestrial particles in the Sør Rondane Mountains, Queen Maud Land, Antarctica, which were produced during a “touchdown” impact event ca. 430 ka ago, when a large airburst vapor jet interacted with the Antarctic ice sheet.

Material and Methods: Twenty nine igneous particles were recovered from glacial sediment collected during the 2017-2018 BELAM (Belgian Antarctic Meteorites) expedition that took place in the Sør Rondane Mountains, Queen Maud Land, Antarctica. Glacial sediment was sampled from a flat eroded summit in the Walnumfjellet (WN) area. 10Be exposure age of nearby summits suggest that the first sampled area has been continuously exposed over the last 870 ka [2]. About half the particles are compound spherules consisting of two or more spherules fused together. The petrography and mineralogy of 18 particles were determined at the Royal Belgian Institute of Natural Sciences of Brussels, Belgium. Their major and trace element compositions were determined at the Museum für Naturkunde of Berlin, Germany, and at Florida State University, USA, respectively. Oxygen isotopic compositions were determined by means of secondary ion mass spectrometry at the CRPG of Nancy, France.

Results: The mineralogy of the particles consists of olivine and spinel, with minor interstitial glass. On the basis on their internal textures and spinel content, we identify four groups of particles: 1/ the spinel-rich particles (SR; N = 9; ≥19% vol. spinel); 2/ Porphyritic olivine (PO; N = 5; <10% vol. spinel); 3/ Barred olivine (BO; N = 3; <10% vol. spinel); and 4/ one cryptocrystalline (CC; ⁓15% vol. spinel).  The bulk major and trace element compositions of the particles are chondritic, pointing to a meteoritic origin. Spinel chemistry in SR particles is characterized by an Fe3+/Fetot of 77-89, where in porphyritic olivine particles, Fe3+/Fetot is lower at 60-62. Bulk spinel chemical compositions suggest highly oxidizing conditions during the formation of SR particles, suggesting that they formed in the lower atmosphere, whereas conditions were much less oxidizing for SP particles [3]. Chemistry and similarities to textural groups in BIT-58 impact particles suggest that all WN particles formed during a single impact event. However, age incompatibly prevents a pairing of WN particles with the impact event recorded in BIT-58. On a petrological and chemical level, WN particles match ⁓430 ka old impact particles found as layers in EPICA Dome C and Dome Fuji (i.e. L1 and DF2641, respectively) [4; 5], suggesting a continental distribution. A likely scenario is the disruption of a large (i.e. at least 100 m in size) chondritic asteroid over Antarctica ~430 ka ago. Oxygen isotopic signatures of WN particles are characterized by a highly negative δ18O, ranging from -35 to -52‰, and Δ17O ranging from -0.5 to - 1.2‰, consistent with oxygen isotopic compositions of L1 and DF2621 particles. Highly negative δ18O values are also consistent with interaction with the Antarctic icesheet during formation of the particles. This suggests that WN, L1 and DF2621 particles were produced during a touchdown impact, which occurs when the jet of melted and vaporized meteoritic material resulting from a large airburst reaches the surface, in this case the Antarctic icesheet, at high velocity. Numerical simulations of a projectile with a diameter of 100 to 150 m entering Earth’s atmosphere at a velocity of 20 km s−1 and an impact angle from 15° to 90° support such a touchdown scenario and, in particular, explain the complex chemical and isotopic conditions leading to the formation of the four observed textural groups SR, SP, BO and CC.

Conclusion: We report the discovery of meteoritic ablation spheres from the Sør Rondane Mountains. Their chondritic chemistry, coupled with characteristic spinel chemical compositions and oxygen isotopic signatures show that they formed in the lower atmosphere during a large touchdown event over the Antarctic icesheet. Combining chemical and isotopic composition with a numerical model help understanding the complex formation processes occurring during this unique impact event over Antarctic likely ~430 ka ago.

References: [1] Artemieva N. A. and Shuvalov V. V. (2016) Annu. Rev. Earth Planet. Sci. 44: 37–56. [2] Suganuma Y. et al. (2014) Quat. Sc. Rev. 97: 102-120. [3] Van Ginneken M. et al. (2010) Earth Planet. Sci. Lett. 293: 104–113. [4] Narcisi B. et al. (2007) Geophys. Res. Lett. 34: (2007) [5] Misawa K. et al. (2010) Earth Planet. Sci. Lett. 289: 287–297. [5] H. Motoyama (2007) Eos Trans. AGU  88, abs. #C51A-0076.

How to cite: Van Ginneken, M., Goderis, S., Artemieva, N., Debaille, V., Decrée, S., Harvey, R., Huwig, K., Hecht, L., Yang, S., Kaufmann, F., Soens, B., Humayun, M., Van Maldeghem, F., Genge, M., and Claeys, P.: A large meteoritic event over Antarctica ca. 430 ka ago inferred from chondritic spherules from the Sør Rondane Mountains., Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-679,, 2021.

Natalia Artemieva, Andrea Schmalen, and Robert Luther

Description of the CdC

Campo del Cielo (CdC, Figure 1) is a 4000-year-old [1, 2] strewn field in the south of the Chaco province, Argentina, which was caused by an impact of IA iron octahedrite [3]. This strewn field has an extremely elongated pattern extending over an area of ~14 km (downrange) by ~3.5 km (lateral). Other known terrestrial strewn fields are much smaller: the Sikhote-Alin in Siberia is 1.2 km long, the Kaalijarv in Estonia is 1 km, and  the Morasko strewn field in Poland extends over a length of 0.4 km.  Another interesting characteristic of CdC is that a lot of depressions found within the strewn field are not impact craters but penetration funnels [4] in which intact meteorites could be found including 30-ton-weight fragments.


This study presents an attempt to reconstruct the Campo del Cielo impact event, i.e., to estimate the minimal pre-atmospheric mass and velocity of the meteoroid, its fragmentation during the atmospheric entry, and to compare the resulting strewn field with the observed one.

The process of meteoroids entering atmosphere can be described with an ordinary differential equation system, which combines drag, gravity and ablation with some kinematic equations [5]. In addition, most meteoroids fragment along their trajectory due to dynamic (ram) pressure caused by the atmosphere. To get good approximate solutions, with inexpensive computational power, we use semi-analytical approaches, like the Pancake and Separate Fragment Model in combination with statistics, such as the Size-Frequency-Distribution, to describe the fragmentation process.

The impact of dense material onto a porous target results in funnels formation instead of an impact crater [6] if the impact velocity is below a critical value. To simulate funnel formation, we use the iSALE-2D shock physics code [7] with initial conditions consistent with the atmospheric entry model.


Atmospheric Model Constraints

  • The largest recovered fragments with a mass of ~30 tons each (El Gancedo, 30.8 tons, found in funnel No. 24 and El Chaco, 28.84 tons, found in funnel No. 10) were not fragmented upon landing, but penetrated the surface to form funnels.
  • The distance between the largest crater (No. 3) and the most distant small meteorite found in situ (No. 26, 3.09 tons) is ~14 km.
  • There are 4 impact craters with a diameter range from 65 to 115 m.



Preliminary analysis of impact experiments and numerical models shows that in the CdC case (iron projectile and loess as a target) funnel formation and projectile survivability is possible at impact velocities below 1 km/s. The iSALE models confirm this estimate: the 1 km/s is probably the upper limit of impact velocity allowing survivability of high strength iron meteoroids impacting into loess. Such low impact velocity requires a specific entry scenario with an extremely shallow entry angle.

Figure 2 shows, that for the vaporization dominated regime (ablation coefficient of 0.01 s2/km2) a fragment with initial mass of 90-100 tons (immediately after fragmentation at an altitude of 20 km) and initial velocity of 16 km/s reaches the surface with velocity below 1 km/s if the entry angle is in the range of 7 - 16° to horizon. Several runs for variated speed of meteoroid at disruption in the range of 12-20 km/s show a possible angle range up to 18.5° and a mass range of 60-150 tons for the largest funnel-forming fragments.

To get a match between calculated and observed expand of the strewn field (~14.03 km), the trajectory angle at the point of disruption should be at least 13° (at a speed of 20 km/s) or up to 15° for lower speed of 12 km/s). 

We also reconstructed the mass and velocity of the four crater-forming fragments using pi-scaling-laws (Figure 3). Their summed mass near the surface is at least 3028 tons (at a speed of 18 km/s) and up to 3692 tons (at a speed of 14 km/s). Its corresponding mass at the disruption point is 5348 and 6779 tons, respectively.

Those results represent just one possible scenario which assumes one fragmentation event from a number of possible scenarios. This scenario suggests that the Campo del Cielo strewn field was formed after an atmospheric entry of a minimal ~9000 tons in mass iron meteoroid (~13 m in diameter) at a shallow entry angle of ~16° and a speed of 14-18 km/s. The meteoroid was severely fragmented during the atmospheric passage: crater-forming fragments (with a final mass of 520 - 1150 tons impacted the surface with a velocity of 4 – 6.5 km/s at an angle of ~14°; funnel-forming fragments (5 – 31 tons, Fig. 4) and small meteorites (3 - 5 tons) landed with velocities < 1 km/s at various angles up to 45° (the smaller the meteorite, the more it is decelerated, and the steeper is the impact angle).



Discussion: We successfully reproduced the length of the CdC strewn field, but its lateral extension is substantially smaller than the observed one. The main reason of this discrepancy is the uncertainty of the repulsion coefficient in case of catastrophic fragmentation and complex behavior of small fragments. The survivability of large fragments (~30 tons) is indeed possible. However, the dependence of funnel’s length on fragment mass (and hence, its velocity) requires additional runs. Also, post-impact collapse of penetration funnels cannot be resolved without 3D models.


The authors acknowledge the funding from the ESA project P3-NEO-VIII. The authors are grateful to Shawn Wright for the update of CdC field observations.



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[2] Cassidy W. A. et al. 1965. Science 149: 1055–1064.

[3] Liberman R. G. et al. 2002. 37:295–300.

[4] Vesconi M. A. et al. 2011. M&PS 46:935–949.

[5] Artemieva N. A. and Shuvalov V. V. 2001. JGR 106:3297–3310.

[6] Kadono T. 1999. Hypervelocity impact into low density material and cometary outburst. PSS 47: 305–318.

[7] Wünnemann K. et al. 2006. Icarus 180: 514–527.

How to cite: Artemieva, N., Schmalen, A., and Luther, R.: Modeling Campo del Cielo strewn field, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-106,, 2021.

Tanja Neidhart, Katarina Miljković, Eleanor K. Sansom, Ingrid J. Daubar, Gareth S. Collins, Jonas Eschenfelder, Annabelle Gao, and Daniel Wexler

An increasing number of newly formed impact craters on Mars have been detected in the last 15 years. These small craters are normally identified via dark spots in lower resolution images that formed during the impact process, presumably through the removal or disturbance of bright surface material [1]. Later higher resolution images revealed single craters or crater clusters, which form when impactors fragment in the atmosphere, within those halos [1,2]. Due to this detection method, most of the new impact sites found are in dusty regions, which imposes an observational bias [3]. Newly formed clusters consist of two to thousands of individual craters and can be tightly clustered or spread out over hundreds of meters [2]. Since the InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission landed on Mars in 2018 [4], the search for newly formed impact craters has become even more important, because identifying impacts in seismic signals could provide further constraints on both the atmospheric and solid-body effects of impact cratering process on Mars, as well as help place further constraints on the properties of the uppermost layer of the crust. As one of InSight’s mission goals is to estimate the current impact rate on Mars, the seismic detection of impacts is also crucial [4].

The aim of this new study is to describe the properties of the complete catalog of known newly formed craters on Mars and examine correlations between different crater cluster properties. We investigated 559 crater clusters and 493 single craters detected between 2008 and 2020 using 25 cm/px HiRISE images. The locations and diameters were noted for each single crater, as well as for every individual crater within a cluster down to 1 m diameter. This was done using ArcMap (ArcGIS) software with the three-point method of the CraterTools add-in [5]. We describe the cluster characteristics, such as the number of craters within a cluster, largest crater in a cluster, cluster effective diameter, cluster dispersion, elevation of the impact sites, and the variation in sizes of craters within a cluster.

More than half of the new impact sites form as clusters. We did not find any differences between the spatial distribution of single and crater clusters across Mars. The mapped crater clusters from this study consist of 2 to 2334 individual craters. More than half of all clusters (58%) consist of 10 craters or less. Crater clusters containing more than 100 craters are rare. With regard to the sizes of craters within crater clusters, we found that for highly populated clusters, the majority of craters are very small, and clusters with few craters have a tendency for craters that are more equal in size. Clusters having large effective diameters contain more equally sized craters. Our results show the full range of parameter spaces that are possible for cluster properties, which can help validate theoretical atmospheric fragmentation models.


[1] Malin M. C. et al. (2006) Science, 314, 1573-1577.

[2] Daubar I. J. et al. (2019) JGR, 124, 958-969.

[3] Daubar I. J. et al. (2013) Icarus, 225, 506-516.

[4] Banerdt B. W. et al. (2020) Nature, 13, 183-189.

[5] Kneissl T. et al. (2011) Planet. Space Sci., 59, 1243-1254.

How to cite: Neidhart, T., Miljković, K., Sansom, E. K., Daubar, I. J., Collins, G. S., Eschenfelder, J., Gao, A., and Wexler, D.: Updated statistics for crater clusters on Mars, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-570,, 2021.

Shock Metamorphic Effects
Mara Murri, Giancarlo Capitani, Mauro Fasoli, Angelo Monguzzi, Alberto Calloni, Gianlorenzo Bussetti, and Marcello Campione

Silicate nanoparticles, otherwise referred to as very small grains (VSGs) [1], occur in various astrophysical environments. These grains experience substantial processing (e.g., amorphization) during their lifetime in the diffuse interstellar medium due to events such as grain-grain collisions and irradiation [2]. Moreover, several studies have pointed out that the main building blocks of these silicates are O, Si, Fe, Mg, Al and Ca, all elements that are among the principal constituents of the Earth’s surface [3], thus leading to the name “astronomical silicates”. However, the structure and chemical evolution together with the origin of these grains are still poorly understood and intensively debated [4,5].

              The aim of this study is the simulation of space weathering processes on olivine single crystals by liquid phase pulsed laser ablation (LP-PLA). The study of the resulting structure of both the target and the ablated material together with their chemical evolution has been carried out by a multiple technique characterization. In particular, spectroscopy and dynamic light scattering measurements, analyses of the electrostatic properties and reactivity to acids and bases on the obtained colloidal solutions of the ablated nanoproducts have been performed and coupled with high-resolution transmission electron microscopy (HR-TEM).

              Selected olivine target crystals (Fo87) from the São Miguel island (Azores) were analyzed by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDX). LP-PLA experiments were performed with a Nd:YAG laser focused via a singlet lens onto the surface of the target, which was fixed at the bottom of a polystyrene box filled with 4 ml of deionized water (type 1) to immerge it completely. Laser pulses of 5 ns and 100 mJ simulate the timeframe and energy exchange occurring during grain-grain interstellar collisions [6] and they generate a plasma plume at the crystal/liquid interface. The rapid cooling induced by the confining liquid layer brings about the condensation of the chemical vapor it contains with production of a colloidal solution of nanoparticles. These solutions were analyzed by dynamic light scattering techniques and optical absorption spectroscopy in the range from 200 nm to 1100 nm (6.20 eV - 1.13 eV). Absorption measurements on the colloidal solutions have been compared against reference colloidal solutions dispersed in deionized water (i.e. mesoporous silica [SiO2] nanoparticles, brucite [Mg(OH)2] nanoparticles, aluminum hydroxide [Al(OH)3] nanoparticles, chrysotile [Mg3Si2O5(OH)4] nanotubes, and synthetic forsterite [Mg2SiO4] nanoparticles). Moreover, additional absorption analyses have been carried out as a function of the addition of known aliquots of sulfuric acid and sodium hydroxide solutions. TEM/EDS analyses were then performed on the ablated nanoparticles deposited via electrophoresis on C-coated Cu grids and compositional variations of the ablated target were determined by X-ray photo-emission spectroscopy analyses.

              The size distribution of LP-PLA synthesized nanoparticles is typically multimodal due to aggregation phenomena. Aggregation is consistent with the measured ζ-potential, which is negative with a relatively low absolute value, within the range 30-50 mV. Nonetheless, a recurrent mode is centered at about 2 nm (hydrodynamic diameter) and it is consistent with the measured size distribution obtained by transmission electron microscopy analysis (average nanoparticles diameter around 3-5 nm). Optical absorption measurements on the ejected material show a main band around 215 nm. This feature is very similar to the “B2 band” reported in several studies on silica glass [7] and ascribed to oxygen vacancies, but its nature is still far to be fully understood. We also found that this feature at 215 nm is very common among both Si and Mg compounds (e.g., Si-oxide, Mg-hydroxide, chrysotile). Moreover, additional absorption bands in the range 240-350nm are observed suggesting the formation of new space weathering products as result of the ablation process.

              Therefore, these results suggest that substantial chemical processing might be expected during space weathering of “typical” interstellar grains into VSGs. Moreover, coupling these experimental results with remote sensing datasets will provide fundamental information about the origin and evolution of these silicate grains.


 Acknowledgments: M.M is supported by the SIMP PhD thesis award.

References: [1] Witt A. N. (2000) Journal of Geophysical Research: Space Physics, 105(A5), 10299-10302. [2] Carrez P. et al. (2002) Meteoritics & Planetary Science, 37, 1599-1614. [3] Henning T. (2010) Annual Review of Astronomy and Astrophysics, 48, 21-46. [4] Draine B. T. (2003) Annual Review of Astronomy and Astrophysics, 41, 241-289. [5] Escatllar A. M. et al. (2019) ACS Earth and Space Chemistry, 3, 2390-2403. [6] Loeffler M. J. et al. (2016) Meteoritics & Planetary Science, 51, 261-275. [7] Skuja L. N. et al. (1984), Solid State Communications, 50, 1069-1072.

How to cite: Murri, M., Capitani, G., Fasoli, M., Monguzzi, A., Calloni, A., Bussetti, G., and Campione, M.: Astronomical silicate nanoparticle analogues produced by pulsed laser ablation on olivine single crystals, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-111,, 2021.

Haruka Ono, Kousuke Kurosawa, Takafumi Niihara, Takashi Mikouchi, Hidenori Genda, Naotaka Tomioka, Tatsuhiro Sakaiya, Tadashi Koundo, Masahiro Kayama, Mizuho Koike, Yuji Sano, Wataru Satake, and Takafumi Matsui

Introduction: Many meteorites have shock metamorphic textures, such as deformation and melting features under polarizing microscope. These shock features have been used to explore a variety of shock histories on meteorite’s parent bodies. A number of shock experiments have been conducted to estimate the shock pressure, which the shock metamorphic textures formed (e.g.,[1]). The previous experiments have been conducted mainly with uniaxial shock-recovery techniques (e.g., [2]). However, the conventional method can only obtain one data set at specific pressure per shot and is difficult to conduct a number of shots due to the destruction of metal containers. There is another technique pertaining to shock recovery, that is, the use of decaying shock waves. This method was applied to shock recovery of single olivine crystals with a high-power laser [3]. In this study, we extend this technique to macro rocky materials with the size of >10 mm using a two-stage light gas gun. Since we used a projectile much smaller than a metal container, a decaying compressive pulse propagates into the target, resulting in shocked samples compressed at various pressures. Our method allows us to reduce the effect of reflected waves from the wall of the container, which is a well-known problem in conventional shock recovery experiments.

Methods: We conducted the shock recovery experiments with a two-stage light gas gun at the Planetary Exploration Research Center of Chiba Institute of Technology, Japan [4]. We used marble and basalt as experimental samples. The samples were shaped into cylinders with a diameter of 30 mm and a height of 24 mm, sealed in a titanium (Ti) container, and covered with a Ti or Al front plate. The impact velocity was 7 km/s on average. The samples were cut across the epicenter and made into thin sections. We used an optical microscope and a scanning electron microscope (SEM) to observe shocked samples in detail. We also conducted numerical calculations under the same conditions as the experiments with the iSALE shock physics code [5-7] to estimate the peak pressure distributions in the samples.

Results and Discussion: We numerically estimated an allowable range of peak pressure in a recovered sample to be ~20 GPa around the epicenter and ~1 GPa around the rear surface of the sample. In the recovered marble sample, we found that calcite exhibited undulatory extinction which is one of the known shock metamorphic textures. The total number of calcite grains showing undulatory extinction decreased with increasing distance from the epicenter. The threshold pressure required for the production of undulatory extinction was estimated to be about 2 GPa, which is close to the Hugoniot elastic limit of calcite [8]. This suggests that plastic deformation leads to the formation of undulatory extinction in calcite. In the case of the recovered basalt sample, plagioclase and pyroxene showed undulatory extinction, and plagioclase does not exhibit mosaicism and vitrification. These observation results indicate that an experienced pressure is up to 20 GPa. In addition, shock melt veins (<4 µm wide) were found to be formed at a distance of 1–2 mm from the epicenter. We estimated that the experienced pressure of the materials at the locations of shock melt veins is about 10 GPa with the iSALE calculation. Therefore, the shock textures, which are the co-existence of undulatory extinction in silicates and shock melt veins, are produced at 10 GPa compression. The shock pressures estimated by the iSALE calculation are consistent with those based on the petrological and mineralogical observations of the recovered samples in this study.

Conclusion: We developed a method to collect shocked samples with a variety of shock pressures (1–20 GPa). Additionally, the peak pressures at the location where the shock features are found are quantitatively estimated with a combination of observation and shock physics modeling. These shock indicators may be useful to estimate the shock histories of chondrite parent bodies.

Acknowledgments: We appreciate the developers of iSALE, including G. Collins, K. Wünnemann, B. Ivanov, J. Melosh, and D. Elbeshausen. We also thank T. Davison for the development of the pySALEPlot.

References: [1] Stöffler, D. et al. (2018) Meteoritics & Planet. Sci. (MaPS), 53, 5-49. [2] Yamaguchi, A. et al. (2003) Springer Science+Business Media, LLC. pp. 29–45. [3] Nagaki, K. et al. (2016) MaPS, 51, 1153-1162. [4] Kurosawa, K. et al. (2015) Journal of Geophysical Research Planets (JGR), 120, 1237-1251. [5] Amsden, A. A., et al. (1980) LANL Report LA-8095. 101 p. [6] Ivanov, B. A., et al. (1997), IJIE, 20, 411. [7] Wünnemann, K., et al. (2006) Icarus, 180, 514. [8] Ahrens, T. J. & Gregson, Jr, V. G. (1964) JGR, 69, 4839-4874

How to cite: Ono, H., Kurosawa, K., Niihara, T., Mikouchi, T., Genda, H., Tomioka, N., Sakaiya, T., Koundo, T., Kayama, M., Koike, M., Sano, Y., Satake, W., and Matsui, T.: Shock recovery of rocks with a variety of shock-induced pressure at a single shot, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-175,, 2021.

Juulia-Gabrielle Moreau, Aleksandra N. Stojic, Argo Jõeleht, Jüri Plado, and Satu Hietala

Introduction: We present a shock-recovery setup to study the melting of genuine troilite and its migration into the surrounding silicate host [1-4], a process responsible for optical darkening in ordinary chondrites [5-6] between 40-60 GPa [3]. We combine a numerical approach [7] with a reverberation shock-recovery experiment [7-10] to calibrate our experimental requirements and verify or falsify our numerical results predictions. Because shock-recovery experiments are expensive, numerical models allow us to identify the optimum experimental conditions. Moreover, natural (precious) meteoritic samples do not allow for an all-parameter controlled experimental set-up, many phases can interact in shock settings [2-4], e.g., the eutectic properties of troilite change when Fe-metal is present [11], affecting the troilite melting efficiency.

Our work aims at identifying shock darkening enhancing parameters by using numerical models to narrow down experimental parameters to an ideal setup. We do this by using olivine and troilite minerals only, thus disposing of chondritic materials. Moreover, the simplification of the starting mineral setup (peridotite and troilite) ensures an uncorrupted study of the genuine melt behavior of troilite.

By succeeding shock melt migration of troilite, we aim to characterize the melt using various analytical methods. The experimental run products will be investigated by scanning electron microscopy, electron microprobe analyses, spectral analyses, x-ray tomography, and optical microscope observations. Identifying melt production and migration relevant parameters will improve our understanding of shock metamorphism and shock-darkening processes.

Methods: The outline of the shock experiment is summarized in Fig. 1. The sample consists of a 20 mm × 1.5 mm thick peridotite disk (Tulppio, Finland; Fo91). Previously synthesized powdered troilite (FeS, [12]) is filled into sub-mm drilled holes atop or beneath the peridotite disk. Powdered troilite promotes shock melting by pore crushing [2].

In classic shock-recovery experiments [8,9] a steel flyer plate (2 mm thick) is accelerated towards a steel container containing the sample. The shock wave propagates in sample after passing a 3 mm thick steel interface (driver plate). Reverberations occurring at bottom/top interfaces between sample and steel container equalize pressures in sample to the pressure in steel. A tantalum foil is used to protect the sample from iron contamination from the sample container.

Using the shock physics code iSALE-2D [13], we reproduce this setup: a half-disk of olivine for simulating peridotite (ANEOS for Fo90) with a 0.5 mm half-sphere of troilite (Tillotson EoS, [2]) surrounded by 0.06 mm thick tantalum (Tillotson EoS, [7]), all inserted in steel (ANEOS for iron) with the 3 mm thick steel driver plate above, are hit by a 2 mm thick steel flyer plate. We vary the impact velocity of the flyer plate (2000–2800 m/s), the troilite porosity (0–20%), its position in olivine (on top, at bottom) and record the following: pressure and temperature at nominal input (before reverberation) and peak of the shock (after reverberation) for olivine and troilite. We interpolate pressure and temperature values with Hugoniot data and estimate the effective entropy input from the reverberation in pressure units.

Expected results: The best conditions to induce melting of troilite are summarized in Fig. 2. A more in-depth illustration of the shock-wave propagation in the numerical models is shown in Fig. 3a-b. We estimate that a 20% porous troilite powder is necessary to induce melting of troilite upon release of the shock wave [2]; for good measure, we compared results for a 3- and 5-mm thick driver plate. We also observed that it is more efficient to melt 20% porous troilite that sits beneath the olivine disk. By observing the propagation of the shock wave, we see that reflected shock waves (first from bottom, lastly from top of the sample) which interfere with previous initial shock waves result in equalization of the pressure to the initial pressure in steel.

Outlook: The numerical study helps to set up optimum experimental conditions of the shock experiment in terms of phase positions within the sample (troilite top or bottom placement) and sample composition. With the planned experiment, we hope to observe shock-darkening of the troilite/peridotite assemblage, which will help to provide leads on similar processes observed in ordinary chondrites.


[1] Stöffler et al. (2018) Meteorit. Planet. Sci. 53, 5–49. [2] Moreau et al. (2018) Phys. Earth Planet. In., 282, 25-38. [3] Moreau et al. (2019) Icarus, 332, 50-65. [4] Moreau and Schwinger (2020) Phys. Earth Planet. In., 310, 106630. [5] Kohout T. et al. (2014) Icarus, 228, 78-85. [6] DeMeo F. E. and Carry R. P. (2014) Nature, 505, 629-634. [7] Moreau (2019) Ph.D. thesis, Unigrafia, Helsinki, 60 pp. [8] Langenhorst and Deutsch (1994) Earth Planet. Sci. Lett. 125, 407–420. [9] Langenhorst and Hornemann (2005) EMU Notes Mineral. 7, 357–387. [10] Schmitt (2000) Meteorit. Planet. Sci., 35(3), 545-560. [11] Mare et al. 2014) Meteorit. Planet. Sci. 49, 636–651. [12] Moreau et al. (2021) Meteorit. Planet. Sci., in prep. [13] Wünnemann K. et al. (2006) Icarus, 180, 514-527.

How to cite: Moreau, J.-G., Stojic, A. N., Jõeleht, A., Plado, J., and Hietala, S.: A shock-recovery experiment to study shock melting of troilite in ordinary chondrites, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-34,, 2021.

Nicole Güldemeister, Juulia Moreau, Tomas Kohout, Kai Wünnemann, and Robert Luther

Introduction: Shock metamorphism in ordinary chondrites [1] is driven by impact events between asteroids. One effect of shock is the darkening of the lithology, which happens at two different stages of the shock intensity scale, at shock stage C-S7 (>70 GPa, whole rock melting, [1]) or between shock-stage 5 and 6 (40–60 GPa, metals and iron sulfides melt veins [2−7]). The darkening affects reflectance spectra of ordinary chondrites and, consequently, of asteroids. If an asteroid fragment of the S-complex asteroids is shock-darkened, its spectra will be similar to C/X-complex asteroids. This would affect the generally accepted spectroscopy-derived distribution of asteroids in the Main Asteroid Belt [7,8].

We investigate the impact conditions on rubble-pile asteroids in order to study the shock stage distribution and the mass of possibly shock-darkened asteroidal fragments. The distribution of porosity in rubble-pile asteroids depends on the internal structure [9]. The aim of the research is to highlight what type of rubble-pile asteroid collisions can explain the abundance of high shock stage materials [10] and the abundance of shock-darkened asteroidal fragments within the asteroid population.

Methods: We use the iSALE code [11] to simulate hypervelocity impact processes. We used the ε-α compaction model [11] for porosity, strength properties from [12] and an ANEOS for dunite to represent the material of the projectile and asteroid. We applied cylindrical-symmetry 2-D Eulerian gridwith Lagrangian tracers to study the distribution of peak shock pressures [13,14]. We apply numerical models of simplified rubble-pile structures of asteroids and study: a) The distribution of peak shock pressures (shock metamorphism). b) Quantification of shock-darkened material in the rubble-pile asteroid as well as in the escaping material. The model of a rubble-pile asteroid of 5 km in diameter is represented by several porous boulders of varying sizes surrounded by loose material. For the different impact scenarios, we varied the impact velocities (4−10km/s), the projectile diameters (800-1600m) and the porosities of the boulders (10−30%) as well as the porosity of the loose material (75−100%).

Results and discussion: The distribution of peak shock pressures strongly depends on both: impact velocity and projectile size (Fig.1a, b). Scenarios with cases considering higher boulder porosities (30%) only result in a small decrease of pressure (Fig. 1c, left panel) and thus lower shock stages are experienced as the shock wave is dampened by the compaction of porosity.

On the one hand porosity is responsible for an overall energy absorption but can on the other hand lead to localized pressure amplifications. Larger porosities of loose material (Figure 1c, right panel; here empty space) do not lead to significant differences compared to the case with porosities of 75% (Fig. 1a, left panel). We also observe that the rubble-pile asteroid is almost completely destroyed and porosity of the loose material is crushed out by the shock wave.

We also determined the efficiency of shock-darkening, which is defined as the shock-darkened mass in the rubble-pile asteroid normalized to the projectile mass (mt/mp). As shown in Fig. 2, the efficiency of shock-darkening increases significantly with increasing impact velocity and is dependent on the porosity of the boulders (compare squares and triangles in Fig. 2). For the most energetic impacts (large impactor and large impact velocities of 10 km/s) an efficiency of eight is reached, which correspond to about 30% of the asteroid being shock-darkened. Increasing the porosity of the boulders from 10 to 30% decreases the efficiency to about half the value. However, the effect remains stronger for larger impact velocity. By decreasing the impact velocity, the efficiency decreases linearly. For the lowest considered impact velocities shock-darkening is not efficient anymore.

In Fig. 3 we show the results from the investigation of the ejecta for different collision scenarios. For the largest impactor, almost the entire asteroid material is already escaping at 6 km/s (cp. red squares). For those cases up to 90% of the asteroid mass is escaping. Considering lower impact velocities, only for the larger impactor a sufficient amount (~50%) of material is escaping. An increase of boulder porosity has a pronounced negative effect on the amount of escaping mass: only a small percentage between 1% and 8% of the total asteroid mass will escape. Fig. 3b and c show the escaping shock-darkened mass with respect to total escaping mass (b) and to the total shock-darkened mass in the rubble-pile (c). Only a small portion of the total escaping mass is actually shock-darkened, for almost all collision scenarios less than 6% (Fig. 3b). It can be shown that for the most energetic impact between 15 and 45% of the shock-darkened mass in the rubble-pile asteroid are escaping from the asteroid (Fig. 3c).

To conclude, high levels of shock metamorphism in ordinary chondrites require impacts with high velocities (8−10km/s) and large projectiles in order to exceed at least 20% of target mass within the C-S5, C-S6 and C-S7 shock stage distribution in rubble-pile asteroids as well as a sufficient amount of shock-darkened escaping material.

Acknowledgments: Our thanks go to the iSALE developers. This work is supported by the Academy of Finland and the European Regional Development Fund and the programme Mobilitas Pluss (Grant No. MOBJD639).

References: [1] Stöffler et al. (2018) Meteorit. Planet. Sci., 53, 5-49.  [2] Moreau J. et al. (2017) Meteorit. Planet. Sci., 52(11), 2375-2390. [3] Moreau J. et al. (2018). Phys. Earth Planet. In., 282, 25-38. [4] Moreau J. et al. (2019). Icarus, 332, 50-65. [5] Moreau J. and Schwinger S. (2020), 310, 106630. [6] Kohout T. et al. (2020) Astron. Astrophys., 639, A146.  [7] Kohout T. et al. (2014) Icarus, 228, 78-85. [8] DeMeo F. E. and Carry R. P. (2014) Nature, 505, 629-634. [9] Housen and Holsapple (2003) Icarus, 163, 102-119. [10] Bischoff et al. (2018) Meteorit. Planet. Sci., 1-14.  [11] Wünnemann K. et al. (2006) Icarus, 180, 514-527. [11] Asphaug et al. (1998) Nature, 393, 437-440. [12] Cremonese et al. (2012) Planet. Space Sci., 66, 147-154. [13] Elbeshausen et al. (2009) Icarus, 204, 716-731. [14] Elbeshausen and Wünnemann (2011) Proc. 11th Hypervelocity Impact Symposium 2010.

How to cite: Güldemeister, N., Moreau, J., Kohout, T., Wünnemann, K., and Luther, R.: High Pressure Shock Metamorphism in Rubble-pile Asteroids using Numerical Simulations, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-468,, 2021.

Impact-induced Seismic Activity
Katarina Miljkovic, Andrea Rajsic, Tanja Neidhart, Eleanor Sansom, Natalia Wojcicka, Gareth Collins, and Ingrid Daubar

The crust on Mars has been structurally affected by various geologic processes such as impacts, volcanism, mantle flow and erosion. Previous observations and modelling point to a dynamically active interior in early Martian history, that for some reason was followed by a rapid drop in heat transport. Such a change has significantly influenced the geological, geophysical and geochemical evolution of the planet, including the history of water and climate. Impact-induced seismic signature is dependent on the target properties (conditions in the planetary crust and interior) at the time of crater formation; Thus, we can use simulations of impact cratering mechanics as a tool to probe the interior properties of a planet.

Contrary to large impacts happening in Mars’ early geologic history, the present-day impact bombardment is limited to small meter-size crater-forming impacts (in the atmosphere and on the ground), which are also natural seismic sources (Daubar et al., 2018, 2020; Neidhart et al., 2020). Impact simulations, in tandem with NASA InSight seismic observations (Benerdt et al., 2020, Giardini et al., 2020), can help understand the crustal properties over the course of Mars’ evolution, including the state of Mars’ crust today. Our most recent numerical investigations include: estimating the seismic efficiency and moment from small meter-size impact events, tracking pressure propagation from the impact point into far field, transfer of impact energy into seismic energy, etc (Rajsic et al., 2020, Wojcicka et al., 2020). Understanding coupling between impact crater formation process with the generation and progression of seismic energy can help identify small impact everts in seismic data on Mars. We also looked at the same process on the Earth (Neidhart et al., 2020) and the Moon (Rajsic, et al., this issue).

Since the landing of the NASA InSight mission on Mars, there was a dozen known new impacts (Miljkovic et al., 2021). However, all but one impact occurred much too far away (3000 to 8400 km distance from the InSight lander) to be within the detectability threshold estimates (Teanby et al., 2015; Wojcicka et al., 2020). About 50% of the observed craters were likely single impacts and the other 50% were evidently cluster craters with less than 40 individual craters in the largest cluster. The largest single crater was ~14 m in diameter, and the largest crater in a cluster was ~13 m (Neidhart et al., this issue), consistent with crater cluster observations (Daubar et al., 2013). The one impact that had a possibility of being detected by SEIS was 1.5 m in diameter at 37 km distance (Daubar et al. 2020).

Considering that orbital imaging is limited in space and time, these known new impacts represent only a fraction of the total number of impacts that have occurred on Mars in the last ~2 years. According to impact flux calculations (Teanby and Wookey, 2011), there should have been ~3000 detectable craters, larger than 1 m in diameter, formed on Mars since InSight landed. If any of these unobserved impacts have been large enough and close enough to InSight to detect seismically, we have not yet discerned them in the seismic data.


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How to cite: Miljkovic, K., Rajsic, A., Neidhart, T., Sansom, E., Wojcicka, N., Collins, G., and Daubar, I.: Numerical modelling of recent impacts on Mars and contribution to InSight mission science, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-459,, 2021.

Andrea Rajšić, Katarina Miljković, Natalia Wojcicka, Keisuke Onodera, Gareth Collins, Taichi Kawamura, Philipe Lognonne, Mark Wieczorek, and Ingrid Daubar

Introduction: A possible source of seismic activity on Mars is meteoroid impacts [5]. Nevertheless, in the first Martian year of the the NASA InSight Mission [2] no signal has been unambiguously associated with an impact event [4]. This calls for further investigation of meteorite strikes and the relationship between impact conditions and the seismic signals they generate. One of the ways to understand the seismic signature of meteoroid impacts is to analyze already existing data from other planetary bodies.

During the Apollo era, over one thousand seismic signals were recorded on the Moon [e.g. 12]. Part of the Apollo seismic experiments were artificial impacts of Lunar modules (LM) and Saturn booster drops (S-IVB). Artificial impacts are considered large scale controlled experiments, because the exact position of the crater and the impactor parameters that made it are known. In this work, we model S-IVB artificial impacts on the Moon, using the iSALE-2D shock physics hydrocode [e.g., 1, 3, 21]. We simulated both the crater formation and the pressure wave propagation and attenuation. We examined size of the crater, cratering efficiency, impact momentum transferred to the target and two seismic parameters: seismic efficiency and seismic moment, and compared these measurements to the existing data [e.g., 10, 8, 7].

One challenge with modelling the S-IVB artificial impacts is the realistic presentation of the projectile. The Apollo S-IVB boosters were hollow aluminum cylinders, with a very low bulk density of 23 gcm3 and mass of 14 t. The booster was 17.8 m long and 6.6 m in radius. The impact speed at the ground level was 2.54-2.66 kms1. The drop angle was reported to be between 13.2 and 35 from vertical. [e.g., 14, 19]. There were five such impacts, and they all impacted into mare basalts and made elliptical craters (long and short axis in between 29.71 m and 38.7 m) with a central mound (crater depth was roughly estimated to 2-3 m) [e.g., 14].

Numerical modelling: All simulations in this work used the iSALE-2D shock physics hydrocode [e.g., 1, 3, 21]. To exclude any influence of target properties, all simulations used the same uniform target model of a 44% porous basaltic regolith [20, 15]. The mass and impact velocity of the projectile in our simulations were the same in all simulations and consistent with the experi- ments. Given the axial symmetry of the mesh geometry employed, we investi- gated five simplified representations of the irregularly shaped projectile. Three cases had a geometry of right-cylinder, with 90% porosity and different dimen- sions: 1. 11.7 m radius and height 0.5 m; 2. 5.8 m radius and 2 m height; 3. 0.992 m radius and 16.7 m height. The last two cases were spheroids: one was non-porous aluminum sphere with 1.06 m radius and the other one was 90% porous and had a radius of 2.3 m [13,21]. To calculate momentum transfer, the vertical component of the seismic moment and seismic efficiency we use approaches described extensively in previous studies [9, 7, 20, 15].

Here, we focus only on the vertical component of the seismic moment Mz [11, 7, 20]. To calculate seismic efficiency we used the same approach described in numerous previous work [e.g., 9, 20, 15].

Results: The shape of the projectile has a substantial effect on crater for- mation but little effect on the seismic signature of the impact. The largest crater was formed in Case 3, while the best agreement with observed crater properties was provided by Case 1 (for depth) and Case 5 (diameter). The porosity of the projectile affected the size of the mound at the bottom of the crater, which supports the idea that the observed central mounds at the bottom of the ob- served craters are projectile remenants [14]. The seismic efficiency k 106 and seismic moment Mz4 1010 Nm were of the same order of magnitude for all cases. This seismic efficiency is in agreement with lower estimates of [10], and the seismic moment is consistent with the scaling proposed in [17, 16, 20, 6].

Conclusion: We have successfully replicated the S-IVB artificial impacts on the moon with iSALE2D, producing craters that are consistent with obser- vations in their approximate dimensions and morphology. The simulations also constrain the seismic efficiency and seismic moment of the artificial impacts, which are relatively insensitive to the density and shape of the impactor. The low seismic efficiency determined here for artificial impacts on the Moon may help explain the non-detection of impacts by InSight in the first Martian year of operating. Moreover, the insensitivity of seismic moment to impactor density and shape suggests that results from the Apollo seismic experiment of these artificial impacts are useful analogs for small impacts on Mars that can be used to better inform their detectability by InSight [17, 16, 20, 6].

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How to cite: Rajšić, A., Miljković, K., Wojcicka, N., Onodera, K., Collins, G., Kawamura, T., Lognonne, P., Wieczorek, M., and Daubar, I.: Numerical modelling of the artificial impacts on the Moon, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-710,, 2021.

Nicola Allen, Hannah Susorney, and Nicholas Teanby

Near-Earth Asteroids visited by spacecraft display a depletion in the number of small craters (< 100 m). For example, the fractured monolith 433 Eros (Thomas et al., 2005), and the rubble piles 25143 Itokawa (Michel et al., 2009), 162173 Ryugu (Noguchi et al., 2021), and 101955 Bennu (Daly et al., 2020) all show a depletion in small craters. Models of the crater populations on Eros and Itokawa indicate that the depletion can be explained by seismic shaking induced by meteorite impacts (e.g., Thomas et al., 2005; Richardson et al., 2004; 2005; Michel et al., 2009). The effects of seismic activity occur in the active layer, the uppermost layer of the regolith. Previous models of seismic shaking that recreate crater populations have used a broad range of active layer depths, ranging from 0.1 m to 5 m across various models for Itokawa and Eros (Richardson et al., 2004; 2005; 2020; Michel et al 2009; Susorney et al., 2021). However, the actual regolith thickness is poorly constrained or unknown in many cases.

In this study, the uncertainty introduced into seismic shaking models from the assumed active layer thickness is investigated by comparing the relative timescales of crater relaxation (crater erasure). We use the Richardson et al., (2004) seismic shaking model, as modified by Michel et al., (2009) for Itokawa with impactor populations from O’Brien and Greenberg (2005). Our results show that decreasing the active layer depth leads to a nonlinear increase in the time to erase a crater. The total increase in time to erasure for a crater 20 m in diameter when changing from regolith depths of 5 m to 0.1 m is over three magnitudes, mostly accommodated between depths of 1 m to 0.1 m. We also investigated the relative timescales of crater erasure for craters of different sizes. Increasing the crater diameter leads to a non-linear increase in crater erasure time, with a 103 increase in erasure time when the diameter is increased from 5 m to 100 m.

The high sensitivity of crater erasure time on active layer depth and crater size implies that care should be taken when inferring surface properties, in particular asteroid surface age, time since a resetting event, or depth/diameter comparisons between asteroids with different crater populations.



                  Daly, R.T., Bierhaus, E.B., Barnouin, O.S., Daly, M.G., Seabrook, J.A., Roberts, J.H., Ernst, C.M., Perry, M.E., Nair, H., Espiritu, R.C., Palmer, E.E., Gaskell, R.W., Weirich, J.R., Susorney, H.C.M., Johnson, C.L., Walsh, K.J., Nolan, M.C., Jawin, E.R., Michel, P., Trang, D., Lauretta, D.S., 2020. The Morphometry of Impact Craters on Bennu. Geophys. Res. Lett. 47, e89672. doi:10.1029/2020GL089672

Michel, P., O'Brien, D.P., Abe, S., Hirata, N., 2009. Itokawa's cratering record as observed by Hayabusa: Implications for its age and collisional history. Icarus 200, 503–513. doi:10.1016/j.icarus.2008.04.002

Noguchi, R., Hirata, N., Hirata, N., Shimaki, Y., Nishikawa, N., Tanaka, S., Sugiyama, T., Morota, T., Sugita, S., Cho, Y., Honda, R., Kameda, S., Tatsumi, E., Yoshioka, K., Sawada, H., Yokota, Y., Sakatani, N., Hayakawa, M., Matsuoka, M., Yamada, M., Kouyama, T., Suzuki, H., Honda, C., Ogawa, K., Kanamaru, M., Watanabe, S.-I., 2021. Crater depth-to-diameter ratios on asteroid 162173 Ryugu. Icarus 354, 114016. doi:10.1016/j.icarus.2020.114016

O'Brien, D.P., Greenberg, R., 2005. The collisional and dynamical evolution of the main-belt and NEA size distribution, Icarus 178, 179

Richardson, J.E., Melosh, H.J., Greenberg, R., 2004. Impact-induced seismic activity on asteroid 433 Eros: a surface modification process. Science 306, 1526–1529. doi:10.1126/science.1104731

Richardson, J.E., Melosh, H.J., Greenberg, R.J., O'Brien, D.P., 2005. The global effects of impact-induced seismic activity on fractured asteroid surface morphology. Icarus 179, 325–349. doi:10.1016/j.icarus.2005.07.005

Richardson, J.E., Steckloff, J.K., Minton, D.A., 2020. Impact-produced seismic shaking and regolith growth on asteroids 433 Eros, 2867 Šteins, and 25143 Itokawa. Icarus 347, 113811. doi:10.1016/j.icarus.2020.113811

How to cite: Allen, N., Susorney, H., and Teanby, N.: The role of regolith thickness in seismic shaking on asteroids, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-118,, 2021.

The Impact Cratering Record
Hidenori Genda and Ryuki Hyodo

Numerous small bodies inevitably lead to cratering impacts on large planetary bodies during planet formation and evolution. As a consequence of these small impacts, a fraction of the target material escapes from the gravity of the large body, and a fraction of the impactor material accretes onto the target surface, depending on the impact velocities and angles. Here, we study the mass of the high-speed ejecta that escapes from the target gravity by cratering impacts when material strength is neglected. We perform a large number of cratering impact simulations onto a planar rocky and icy targets using the smoothed particle hydrodynamics method. We show that the escape mass of the target material obtained from our numerical simulations agrees with the prediction of a scaling law under a point-source assumption when vimp > ~ 10 vesc, where vimp is the impact velocity and vesc is the escape velocity of the target. However, we find that the point-source scaling law overestimates the escape mass up to a factor of ~ 70, depending on the impact angle, when vimp < ~ 10 vesc (Figure 1). Using data obtained from numerical simulations, we derive a new scaling law for the escape mass of the target material􏰁. We also derive a scaling law that predicts the accretion mass of the impactor material onto the target surface upon cratering impacts by numerically evaluating the escape mass of the impactor material. Our newly derived scaling laws would be useful for predicting the erosion of the target body and the accretion of the impactor for a variety of cratering impacts that would occur on large rocky and icy planetary bodies during planet formation and collisional evolution from ancient times to today (Figure 2).


Figure 1. Schematic illustration of cratering impacts (left) and velocity distribution of the ejecta (right). High- and low-speed ejecta are launched closer to and farther from the impact point, respectively; that is, the escape mass is launched from the vicinity of the impact point (left). Irregular-shaped objects in the left panel indicate ejecta of target and impactor materials (the total amount and their fractions depend on the impact condition). The point-source scaling law is characterized by a unique slope in the velocity distribution, while direct SPH simulations of cratering impacts demonstrated that high-speed ejecta would have a steeper slope for the velocity distribution (the gray line in the right panel). This discrepancy leads to an overestimation in the escape mass when using the point-source scaling law, depending on the considered escape velocity of the target vesc.


Figure 2. Impact angle-averaged scaling laws for rocky (red lines) and icy (blue lines) bodies as a function of vimp/vesc. Left: the escape mass of the target material (Mesc,tar) normalized by impactor mass (mimp). Middle: the accretion mass of the impactor material onto the target surface (Macc,imp/mimp). Right: total escape mass (Mesc,tot = Mesc,tar + Mesc,imp in a unit of mimp; Mesc,tot > 1 indicates a net erosion and vice versa for a net accretion). Examples of typical outcomes of cratering impacts on different solar system bodies under different contexts are indicated by the labels in each panels.


How to cite: Genda, H. and Hyodo, R.: Erosion and accretion by cratering impacts on rocky and icy bodies: Formulation of scaling relations for high-speed ejecta, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-154,, 2021.

Bernd Buchenberger, Elliot Sefton-Nash, and Olivier Witasse


The elongated crater population on Mars is of great interest in planetary sciences [1]. In 1982, 1988 and 2000 three datasets were established using Viking images [1,2,3]. In 2011 a new and improved set of data with 261 craters and a database including up-to-date images taken by the High Resolution Stereo Camera (HRSC) onboard ESA’s Mars Express were established [4] and continuously updated [5]. Based on the crater shape [6] and the ejecta deposit [7] the direction of impact can be estimated. Since this is not always a straightforward determination, it was decided to check whether the topographic profile could help in ambiguous cases.

1. Introduction

Impact cratering is one of the fundamental processes in shaping the surface of terrestrial planets. Even though most impact structures have a circular shape, a small fraction of elongated craters formed by oblique impacts can be observed. Using the recently developed Mars Express database, the current study focuses on the impact direction of elongated craters on Mars.

2. Motivation for the study

One major driver for conducting this study is the ongoing discussion of the decaying moonlets hypothesis, which might be an explanation for at least a fraction of the elongated crater population on Mars, as well as the unsolved origin of the Martian moons, Phobos and Deimos [5,9].

3. Direction of impact

As a precondition the crater orientation is analysed and a strong correlation to the crater age can be stated. For the identification of the impact direction a two-stage process is applied and this presentation shows the usefulness of the procedure. A first estimation is based on the crater shape [6] and the ejecta deposit [7]. Figure 1 shows a crater example and table 1 the summarized results for the elongated crater population on Mars. Subsequently, the estimation is reviewed by an analysis of the topographic crater profiles, which result from the pressure distribution during impact [8]. Figure 2 presents the corresponding profile for the first example crater. This review process indicates the validation of the results of the first stage. For craters with morphological characteristics not allowing a distinct identification of the impact direction in stage one this approach helps to improve the dataset dramatically (figures 3 and 4).

4. Figures

Figure 1: Estimation of impact direction based on crater shape and ejecta deposit for example crater 1

Figure 2: Altitude profile of example 1 based on HRSC MOLA blended DEM (200m) confirms East to West impact direction

Figure 3: Distinct identification of impact direction based on crater shape and ejecta deposit difficult for example crater 2

Figure 4: Altitude profile indicates West to East impact direction