The 1908 Tunguska airburst over Siberia, most likely caused by a 50–80 m stony asteroid, released roughly 15 Mt of energy yet left no undisputed macroscopic meteorite. Carbognani, Di Martino and Stirpe (Icarus, 2024) computed a first probabilistic strewn field for surviving meter-scale stony fragments — about 11 km west-northwest of the epicenter, roughly 140 km² — but conditioned it on poorly constrained inputs: the trajectory azimuth and inclination, the fragment-strength distribution (extrapolated from Chelyabinsk samples), a substitute modern atmosphere, and a phenomenological fragmentation model. The open problem is to determine, with quantified uncertainty, whether macroscopic fragments of the Tunguska Cosmic Body survived the airburst and where they lie, and to make that prediction testable by a targeted search. Later literature has validated the modeling machinery on small observed falls and has reported shocked and melted microscopic grains near the epicenter and in a lake ~60 km west, but no macroscopic fragment has been recovered and no later study has recomputed or closed the Tunguska strewn-field question.

Background

On June 30, 1908, a small cosmic body — the Tunguska Cosmic Body (TCB) — exploded in the atmosphere about 8.5 km above the Siberian taiga, flattening roughly 2150 km² of forest with an energy release of about 15 Mt (megatons of TNT equivalent). Kulik's 1927 expedition and all later searches found no undisputed macroscopic meteorite near the epicenter, and a leading modeling tradition since Chyba, Thomas and Zahnle (Nature, 1993) holds that a stony body of this size disrupts high in the atmosphere. A strewn field is the elongate region on the ground where fragments of a meteoroid that survives atmospheric passage land; after an airburst (an explosive disruption of the body in flight), surviving fragments undergo dark flight — the final, drag-dominated, subsonic trajectory governed by gravity, atmospheric density, and winds. Because larger meteoroids are weaker per unit mass, Chelyabinsk-class events (Borovička et al., Nature, 2013) show that meter-scale fragments can survive: the 570 kg F1 fragment of the 2013 Chelyabinsk fall was recovered from a lakebed ~70 km from its airburst, and the 2007 Carancas fall in Peru demonstrated impact strengths of 20–40 MPa. Carbognani, Di Martino and Stirpe (Icarus, 2024) built a single-body entry model — mass ablation (erosion of the body by aerodynamic heating), a pancake phase (a phenomenological lateral-expansion treatment of the flattening, disrupted body before it decouples into fragments), and Weibull's law for fragment strength (the statistical scaling under which smaller fragments of a stony body are stronger, with modulus α borrowed from Chelyabinsk laboratory samples, α≈0.2) — followed by dark-flight integration. For a 15 Mt body entering at 11–20 km/s with inclination 35°±5°, they concluded that a fragment of ~1.4 m and ~5000 kg with mean strength 14–85 MPa could reach the ground at 0.5–0.8 km/s, likely burying itself in permafrost, and they mapped the resulting probabilistic strewn field ~11 km west-northwest of the epicenter. Their conclusion that Lake Cheko — proposed by Gasperini and colleagues as a TCB impact crater but disputed by Collins and colleagues, who found no impact evidence — lies ~3.5 km outside the field at 3σ, and that the large quartzitic boulder John's Stone is probably terrestrial (Bonatti et al., Icarus, 2015), are adjuncts of this prediction. The authors themselves stress what the prediction cannot fix: the trajectory azimuth and inclination are not uniquely constrained by eyewitness accounts and the treefall pattern (e.g., Krinov's azimuth near 137∘137^\circ versus the 150∘150^\circ–180∘180^\circ that would place Cheko inside the field); no contemporaneous atmospheric sounding exists, so winds must be taken from modern climatological models such as NRLMSISE-00 (an empirical model of Earth's upper atmosphere) or the US Standard Atmosphere; the TCB's true fragment-strength statistics are unknown and were extrapolated with an ad hoc strength cap; and the pancake treatment, the assumption of a monolithic stony (non-rubble-pile) progenitor, and the neglect of detailed shock–fragment and plasma physics all leave the fragmentation and decoupling timing uncertain.

Problem Statement

Determine whether macroscopic stony fragments (order-meter, thousands of kilograms) of the Tunguska Cosmic Body could have survived the 1908 airburst and reached the ground, and where they lie. The probabilistic strewn-field prediction for surviving fragments must quantify its uncertainty explicitly over the unconstrained inputs the source paper identified — the trajectory azimuth and inclination (marginalizing over the mutually inconsistent eyewitness and treefall estimates), the fragment-strength distribution (Weibull statistics extrapolated from other falls, with its strength caps), the substituted atmospheric wind and temperature profiles, and the phenomenological fragmentation and pancake modeling — and it must be testable by a targeted search of the ~11 km west-northwest candidate region (or its revision). Physical recovery of a fragment would be the definitive confirmation but is not required, since no modeling study can secure it. The overarching single objective is whether macroscopic Tunguska material survived and, if so, where it lies; the trajectory, strength-statistics, atmospheric, and fragmentation-modeling components all serve that objective.

References

  1. Albino Carbognani, Mario Di Martino, Giovanna Stirpe (2024). Computation of a possible Tunguska's strewn field. Icarus 408, 115845, DOI 10.1016/j.icarus.2023.115845; preprint arXiv:2302.13620 (2023), https://arxiv.org/abs/2302.13620
  2. Albino Carbognani, Marco Fenucci, Raffaele Salerno, Marco Micheli (2025). Ab initio strewn field for small asteroids impacts. Icarus 425, 116345, DOI 10.1016/j.icarus.2024.116345, https://doi.org/10.1016/j.icarus.2024.116345
  3. Gunther Kletetschka, Marian Takac, Lucie Smrcinova, Radana Kavkova, Dallas Abbott, Malcolm A. LeCompte, Christopher R. Moore, James P. Kennett, Victor Adedeji, Timothy Witwer, Kurt Langworthy, Joshua J. Razink, Valerie Brogden, Brian van Devener, Jesus Paulo Perez, Randy Polson, Teresa M. Eaton, Matthew J. Valente, David B. Lanning, Yoav Rapoport, Argyro Reyes, Ravi Holladay, Michelle Madrigal, Aleksei Kiselev, Allen West (2025). New Evidence of High-Temperature, High-Pressure Processes at the Site of the 1908 Tunguska Event: Implications for Impact and Airburst Phenomena. Airbursts and Cratering Impacts, DOI 10.14293/aci.2025.0001, https://doi.org/10.14293/aci.2025.0001
  4. Gunther Kletetschka (2025). Misunderstandings about the Tunguska airburst event, clarifying the physical record based on new evidence. Airbursts and Cratering Impacts, DOI 10.14293/aci.2025.0006, https://doi.org/10.14293/aci.2025.0006
  5. Lucie Smrčinová, Gunther Kletetschka, Richard Štorc, Eva Švecová, Viktor Goliáš, Daniel Vondrák (2025). Lake Zapovednoe's Molten Fragments of Tunguska Airburst in 1908. EGU General Assembly 2024 abstract (EGUsphere), DOI 10.5194/egusphere-egu24-15462, https://doi.org/10.5194/egusphere-egu24-15462
  6. G. S. Collins, N. Artemieva, K. Wünnemann, P. A. Bland, W. U. Reimold, C. Koeberl (2008). Evidence that Lake Cheko is not an impact crater. Terra Nova 20, DOI 10.1111/j.1365-3121.2008.00791.x, https://doi.org/10.1111/j.1365-3121.2008.00791.x
  7. Luca Gasperini, Enrico Bonatti, Giuseppe Longo (2008). Lake Cheko and the Tunguska Event: impact or non-impact? Terra Nova 20, DOI 10.1111/j.1365-3121.2008.00792.x, https://doi.org/10.1111/j.1365-3121.2008.00792.x
  8. Enrico Bonatti, Dee Breger, Tommaso Di Rocco, Fulvio Franchi, Luca Gasperini, Alina Polonia, John Anfinogenov, Yana Anfinogenova (2015). Origin of John's Stone: A quartzitic boulder from the site of the 1908 Tunguska (Siberia) explosion. Icarus 258, DOI 10.1016/j.icarus.2015.06.018, https://doi.org/10.1016/j.icarus.2015.06.018
  9. Rosanna Fantucci, Romano Serra, Gunther Kletetschka, Mario Di Martino (2015). The Tunguska event and Cheko lake origin: dendrochronological analysis. International Journal of Astrobiology 14, DOI 10.1017/s1473550414000445, https://doi.org/10.1017/s1473550414000445
  10. D. Y. Rogozin, L. B. Nazarova, N. A. Rudaya, L. A. Frolova, L. S. Syrykh, G. N. Bolobanshchikova, O. V. Palagushkina, A. V. Darin, A. V. Meydus (2025). Tracking Late Holocene climate change and the 1908 Tunguska impact event from lake sediments in Central Siberia. Quaternary Research 125, DOI 10.1017/qua.2024.35, https://doi.org/10.1017/qua.2024.35
  11. Jiří Borovička, Pavel Spurný, Peter Brown, Paul Wiegert, Pavel Kalenda, David Clark, Lukáš Shrbený (2013). The trajectory, structure and origin of the Chelyabinsk asteroidal impactor. Nature 503, DOI 10.1038/nature12671, https://doi.org/10.1038/nature12671
  12. Christopher F. Chyba, Paul J. Thomas, Kevin J. Zahnle (1993). The 1908 Tunguska explosion: atmospheric disruption of a stony asteroid. Nature 361, DOI 10.1038/361040a0, https://doi.org/10.1038/361040a0
  13. Mark Boslough; Los Alamos National Laboratory (2025). Tunguska as validation case for fast-running airburst TTX simulator. OSTI report, DOI 10.2172/2996973, https://doi.org/10.2172/2996973