Siberian forest after explosion of the Tunguska body: astroecological problems E.A. Kasatkina and O.I. Shumilov Institute of North Industrial Ecology Problems of Kola Science Centre RAS, Apatity, RUSSIA;

Environmental consequences of impacts by comets and asteroids depend on their sizes. The impact of 10 km sized asteroid killed off the dinosaurs 65 million years ago. A comet impact in AD 536 (>500 m diameter) caused a global climatic downturn. An impact of Tunguska-sized (50 m diameter) object could devastate a 2000 km^2 forest area, roughly the size of Moscow or New York.

Scientists think impacts from comets may have played a role in the evolution of Earth billions of years ago. Meteorites and comets delivered large amounts of organic to the early Earth.

A comet impact in AD 536? A comet impact in AD 536? (E. Rigby, M. Symonds, D. Ward-Thompson, 2004) Dendrochronological data showing the decreases in the rate of tree-ring growth for the years around AD 540. USA Ireland

Comet or Asteroid? n On June 30, 1908, something exploded above the Siberian taiga, near the Tunguska River. The TNT equivalent of explosion is estimated between 10 and 40 megatons. The explosion devastated a 2000 km 2 forest area. n Theories of its origin range from a large asteroid or comet, to a nuclear-fueled spaceship.

Some mysteries of Tunguska event n The mechanism of optical anomalies (abnormal dawns and luminescence of an atmosphere) developed in the summer of 1908 before and after Tunguska event. n The cause of the accelerated tree growth after 1908 in the catastrophe area.

Development of optical anomalies in summer of Total number of points where optical anomalies were registered - solid line (I), number of points where noctilucent clouds were observed - dashed line (II). The appearance of noctilucent clouds during June-July 1908 must have been the largest event of that type in the last century (Vasilyev, 1998).

Points where optical anomalies of summer 1908 were observed. Anomalies observed to the west from the place of explosion (West Siberia, European Russia, Northern Europe) but not seen in other parts of the Earth. +

Calculations by Zotkin in 1969 and Kresak in 1978 have shown that TSB was a fragment by comet Enke. This version makes clear why 10 days prior to Tunguska event in Northern Hemisphere were registered optical anomalies. It was an influence of the ionized dust tail of a comet on the top layers of the Earth’s atmosphere. And the more the trajectory of flight TSB came nearer to the Earth after June 20, the scales of this influence were stronger. Note: The similar optical phenomena were observed in the sky of the Earth when the Earth passed through a tail of Galley comet. Note: The appearance of dust before the passage of fireball was observed during the similar event - “1930 Brazilian Event”. It was called “Brazilian twin” of Tunguska event ( Bailey et al., 1995 ).

60-75N; E -112% 60-75N; 80-90E -70% 60-75N; 70-90E no effect 60-75N; 60-70E no effect

60-75N; E -112% 50-60N; E no effect 60-75N; E no effect

57.8N; 108.1E -9% Small increase in summer temperatures would hardly be a main reason of the accelerated tree growth observed.

Areas where accelerated tree growth was observed: zone A - 112%; zone B - 70%. Accelerated tree growth was observed 12° to the north, 10° to the east and 20° to the west from the place of explosion.

Winter Summer Zonal winds in the Northern Hemisphere

Consequences of the Chulym bolide explosion and tree growth The Chulym bolide exploded above the Chulym river, Siberia (57.7N; 85.1E) on 26 February, TNT equivalent - 10 Kt

55-75N; 80-90E - 63% 55-75N; 70-80E no or small effect 55-75N; 60-70E no or small effect 50-55N; 80-90E no effect

55-75N; 80-90E - 63% 55-75N; E - 50% 55-75N; E no or small effect

Areas where accelerated tree growth was observed: zone A - 63%; zone B - 50%. Accelerated tree growth was observed 14° to the north, 5° to the west and 15° to the east from the place of explosion.

Chulym Summer temperatures

Consequences of the Kola bolide explosion (1873) and tree growth. 49% 29% 26%

Possible reasons of the tree- growth anomaly observed n Stimulation of tree growth by cometary matter spreaded over a large territory and introduced into a soil. n NO produced in the atmosphere during bolide explosions: Tunguska event - 30 million tons (Turko et al., 1982); Chulym bolide tons.

The comet composition n 1. Organic - C, C 2, CN, CO, HCN et al.; n 2. Inorganic - H, NH, NH 2, O, OH, H 2 O; n 3. Metals - Na, Ca, Cr, Mn, Fe, Cu et al.; n 4. Ions - CO +, CN +, OH +, H 2 O + et al.

Effects on plant growth were examined on Solanum tuberosum (potato), where extracts of the Murchison meteorite lead to enhanced growth and pigmentation.

Conclusions n It was considered the possibility of using of tree-ring chronologies as a proxy of comet impacts.