The finding
Cause of deathCold, for six of the nine; crushing under a mass of snow, most probably in the ravine, for three. No other people, no weapon, no explosion, no vehicle and no poison is recorded on or around the bodies.
Why they leftThe uphill half of the tent came down on them under snow, in the dark, most probably a small slab avalanche released from the stepped slope above the platform they had cut, less probably drifted snow collapsing the roof. They went downhill for the forest expecting more to follow, and could not find their way back. Within that general cause, the slab that Gaume and Puzrin modelled is the leading candidate at 45 per cent, but it has not been established.
Confidencenatural causes, no human agent · 90% snow on the tent as the trigger · 65% of which a small slab avalanche, the Gaume–Puzrin mechanism · 45% the three injured in the ravine rather than at the tent · 75%
Strength of the evidenceThe evidence for natural causes is strong: it leaves little room for another answer. The trigger mechanism has a leading candidate, the slab, among several that remain possible. The ravine as the place of the injuries is probable: the evidence clearly favours it over the tent without proving it.
Conditional onThe nine explanations scored in the matrix and the weight given to each of the 28 facts. The percentages are judgments about the evidence; a different list of rivals or different weights gives different numbers. Re-weighting the facts moves them about this far: natural causes 80 to 95, on the weight given to the missing chemical sheets; snow trigger 50 to 80 and the slab 20 to 65, on the unmeasured snow above the 1959 position and the fitted delay; the ravine 60 to 85, on the examiner's survival-time statements against the claim by Eduard Tumanov, a Moscow forensic expert who reviewed the 2018 exhumation, that the rib fractures run on different lines. The ranges come from re-weighting the 28 facts for this report; they are not taken from any published source.
The slab modelInternally sound, reproduced here to the published precision, and physically possible on this slope. Its terrain requirement, a step steeper than 28 degrees above the tent, is met on the authors' 9 cm drone survey of 2021, which shows such steps above every candidate tent position; a coarser public elevation model cannot see them and does not count against it. Its snow requirement, a buried weak layer on that step in February 1959, is unmeasured; its release delay is fitted to the forensic clock rather than predicted; and its injury calculation cannot tell the tent from the ravine. Its positive case, that a slab could have struck the tent, does not by itself place the crushing injuries at the tent; the objections to it do not by themselves place them in the ravine. The 75 per cent for the ravine rests on the 1959 examiner's statements about mobility and survival time (л.д. 381–383) and on the 2019 reading of Zolotaryov's bones by Sergey Nikitin, the forensic expert who examined them after their exhumation in 2018. The slab argument does not bear on it either way.
Would overturn itA snow profile up the step above the 1959 tent position: a buried weak layer under a wind slab would make the slab the finding, and hard, well-bonded snow to the ground, found repeatedly, would lower it. The missing 1959 chemical and histological sheets, or a full exhumation, showing a toxin or soft-tissue injury would cut the natural-cause figure. A range record of a launch over the northern Urals on 1–2 February 1959 would revive the military theory; none exists in the published launch lists. The full list is in the section on what would overturn it.
How to read the numbers. The 90 per cent for natural causes is not shared out among the named rivals. Each of those is contradicted by at least one documented fact and is scored below. The residual is for what the file cannot check: the chemical and histological analyses referred to in the autopsy acts are not in the file, and of the nine bodies only one, Zolotaryov's, has been examined since 1959, privately, in 2018. Of the 65 per cent for snow on the tent, 45 points go to a small slab avalanche from the steps above the tent, the mechanism Gaume and Puzrin modelled, and 20 to drifted snow collapsing the roof without any release. The remaining 35 per cent of the trigger splits between a wind event alone, 15, which the standing entrance and the calm tracks argue against, and something not in the record, 20.
The most probable sequence. The sequence below carries the confidences given above. Nine experienced skiers cut their way out through the downhill wall of a tent whose uphill half had come down, left their boots and coats inside, and walked 1.5 km to the forest edge in a close group at a normal pace, in complete darkness, in a rising wind at about −12 °C and falling. Under a cedar they made a fire and cleared a line of sight up the slope. Two of the least dressed died beside it within about two hours. Three set off back for the tent and died on their own track 180 to 230 m short of it, one of them after a fall that cracked his skull. The four best dressed, now wearing the dead men's clothes, dug into a drifted stream bank 75 m from the fire and laid a floor of fir tops; the snow over the stream gave way, three were crushed under it without a mark on the skin, and the fourth froze beside them. The prosecutor Lev Ivanov closed the case on 28 May 1959 with «стихийная сила, преодолеть которую туристы были не в состоянии», an elemental force the hikers were unable to overcome. No later work has displaced that finding. This report adds, as the most probable answers rather than as established facts, what the resolution left unstated: the force was snow, at about 65 per cent, and the crushing injuries happened in the ravine rather than at the tent, at about 75 per cent.