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Using charcoals as a proxy to estimate energy released from small Impact cratering processes

Periodic Reporting for period 1 - ImpChar (Using charcoals as a proxy to estimate energy released from small Impact cratering processes)

Reporting period: 2017-10-01 to 2019-09-30

Asteroid impacts represent a natural hazard capable of causing significant damage on the Earth, as evidenced by the impact of a body that formed the 180-km wide Chixulub crater causing extensive environmental perturbations. Estimates of the current impact flux on Earth show that within the lifetime of our species it is likely that a significant asteroid impact will hit a populated area.

Existing observational and modelling approaches have found it hard to quantify the thermal energy release from small impact cratering processes. Most methods used to study and characterise small impact craters and the energy processes associated with them are based on approaches used to assess large impact craters with high temperature transitions, that are rarely present in small impact craters in unconsolidated target rocks.
The aim of ImpCHAR was to use properties of dead bodies of organisms killed during the fall of the asteroid and preserved within their ejecta blanket as a char to understand the energy release from small impacts. We do it by a set of targeted field work within proximal ejecta blanket of confirmed impact craters up to 120 m in diameter (Kaali in Estonia, Morasko in Poland and Whitecourt in Kanada), a couple of unconfirmed structures (Ilumetsa in Estonia and Tor in Sweden), a set of laboratory experiments mimicking different scenarios of charcoal production.

Here we show that the reflective properties of charcoals found in the proximal ejecta of small impact craters are distinguishable from those produced by wildfires. We reveal that: 1) the proximal ejecta blanket of small impact craters is locally hot, and 2) finding charcoal with specific reflective properties within proximal ejecta can be used to identify the meteorite impact origin of small craters. This study will enable us to better quantify the impact rate and understand the full spectrum of possible interactions of impactors with the atmosphere and Earth’s surface, so that we can adequately prepare for the future impact.
"Work performed:
- Charcoals have been collected from selected, confirmed, very small impact craters, two possible craters as well as wildfires.
- Experiments mimicking two possible modes of charcoal formation.
- Charcoals were measured under the reflectance microscope.
- Data was analysed.
- Additional field work was made.
- Results were presented on conferences (see below).
- Papers were written and some were already published (see below).
- Plenty of outreach activities was done.

Published papers:
Losiak, A. Jõeleht, J. Plado, M. Szyszka, K. Kirsimäe, E.M. Wild, P. Steier, A.M. Jazwa, R. Helde, C. Belcher (2020) Determining the age and possibility for an extraterrestrial impact formation mechanism of the Ilumetsa structures (Estonia). Meteoritics and Planetary Sciences.
9 other papers are in preparation/ submission.

Conference abstracts:
Losiak, Jõeleht, Plado, Szyszka, Wild, Steier 2018. Dating small impact craters on Earth and the “old wood problem”. MetSoc, #6219.
Losiak, Belcher 2018. Proximal ejecta blankets of small impact craters as time capsules preserving a timelapse of paleoenvironment 10th European Palaeobotany and Palynology Conference 12-17.08.2018 in Dublin.
Losiak, Belcher, Jõeleht, Plado, Szyszko 2019. Death from Space: Origin of Charcoal found in Proximal Ejecta Blanket of Kaali Craters (is NOT what we Think). LPSC #2406.
Losiak, Belcher, Plado, Jõeleht 2019. Recognising small impact craters on Earth Impacts and Life conference Tällberg, Siljan Crater 10-13.06.2019.
Losiak., Avery, Elliott, Belcher 2019. Burning trash for science: using waste to monitor wildfire energies. Wildfire Conference England and Wales Wildfire Forum. Cardiff 2019.
Karahan, Lubanski, Wilczyński, Węclewski, Losiak 2020. European Rover Challenge (ERC) – an Annual International Robotics Competition in Poland. LPSC #2188
Losiak, Belcher, Plado, Jõeleht, Herd, Kofman, Szokaluk, Szczucinski, Muszynski 2020. Using Charcoal formed during an Asteroid Collision to Recognise Small Impact Craters on Earth and to Learn about Energy Distribution around such features. LPSC #1934.
Losiak, Avery, Elliott, Baker, Belcher 2020. Burning trash for science - using waste to monitor wildfire energies. EGU #11536.
Losiak, Belcher, Buchner 2020. Fossil plant remains preserved as charcoal within proximal ejecta blankets of impact craters reveal the influence of asteroid collisions with the Earth’s surface. EGU #11609.
Ormö, Raducan, Luther, Herreros, Collins, Losiak, Wünnemann 2020. Effects of target heterogeneity on impact cratering processes in the light of the Hera mission: combined experimental and numerical approach. EPSC2020-922
Plado, Jõeleht, Losiak, Szyszka, Ormö, Alexanderson, Johnsen, Alwmark, Wild, Steier, Belcher, Jazwa. 2021. Small Impact Crater-Like Features: The Tor Crater, Sweden, As A Reference Structure In Evaluating Alternative Causes Of Formation In Non-Volcanic Settings On Earth And Mars. LPSC2021."
ImpCHAR is the first study that, thanks to innovative combination of targeted field work and extended set of laboratory experiments, showed that process of formation of small impact craters on Earth: 1) is capable of killing and charring organisms in its surroundings as well as preserving them within proximal ejecta blanket, 2) char formed during this process is recognisably different than char produced during the forest fires (in terms of its distribution in the subsurface and its reflective properties).

This project will have two main scientific results. Firstly, using technique developed by the ImpCHAR we can distinguish craters made by an impact of an asteroid from pits made by other processes – even if no extraterrestrial material have been found nearby. This will better define the impact rate on Earth. Secondly, properties of impact charcoals can be used as a proxy of how much energy is released and distributed within the proximity of small impact craters on Earth and other terrestrial planets, because reflectance of charcoal depends on the environment in which it was formed. Because of that we used it to map the energy distribution within proximal ejecta. This will help to better calibrate numerical models of impact crater formation.

There are two most important societal influences of the core part of the ImpCHAR project. Firstly, the project resulted in numerous outreach activities. This helped to not only explain issues related to formation of small impact craters, but also built a larger appreciation of Earth Sciences, the role of women in STEM and of course irreplaceable value of funding from the MSCA IF programme. Secondly, we hope that the results of ImpCHAR will help to save lives. Small asteroids (<50 m in diameter) that are large enough to reach the Earth’s surface and form an impact crater, represent the most likely hazard, because smaller bodies are more common than large ones, and positions of small meteoroids is not efficiently tracked by the current Near-Earth Objects search programs. The formation of Carancas crater in 2007 and the fall of Chelyabinsk meteor in 2012 are examples of such events that were not foreseen by any of these programs. A better understanding of the real extend of the environmental effects of such event provided by the ImpCHAR will help to prepare for them in the future.
Ilumetsa Large crater.
Kaali Main impact crater i Estonia.
Formation of an impact crater in the laboratory.
Anna Losiak in the Kaali Main crater.
Anna Losiak in the trench dug within proximal ejecta blanket of Kaali Main crater.
Lidar map of the Kaali strewn field.
A piece of charcoal found within proximal ejecta blanket of Morasko crater in Poland.