mirrored file at http://SaturnianCosmology.Org/ For complete access to all the files of this collection see http://SaturnianCosmology.org/search.php ========================================================== Past, Present, and Future * Two stories from Tunguska _Collected and commented by Timo Niroma, Helsinki, Finland Go to the [1]Evidence of Astronomical Aspects of Mankind's Past and Recent Climate Homepage _ Tunguska. June 30, 1908, Tunguska, Siberia. Let's have two eyewittnesses tell themselves. We can compare and imagine what some myths tell about faraway incidents of a similar incident. S. P. Semenov: "Suddenly the sky broke into two above the Tunguska river. High above the forest the whole northern sky seemed to be in fire. At that moment I felt the heat as if my shirt was in fire. This heat came from north." "I was just about drawing the shirt off to throw it away, when a tremendous detonation was heard from the sky followed by sounds of crashes and cracks. I was sitting on the porch and was flown about six meters. My wife ran out and helped me to the house. The sounds of rumble continued. The whole ground was shaking and trembling." Akulina Potapovits: "Early in the morning, when everybody was still sleeping in the tent, the tent and everybody inside it flew in the air. When they fell back to the ground, the whole family had slight bruises. Akulina and Ivan lost their consciousness. When they recovered, they heard tremendous noise and saw that the forest around them was in fire and much of it was demolished." Dangers in our future. Once upon a time (and not so long ago) it was thought that the bombardment caused by space debris, comets or asteroids, was over some billion of years ago. But the really big hits 65 and 35 million years ago already awaked those who happened to make some percentage calculations. These being only 1.4% and 0.77% old compared to the age of the Earth, should have alerted that the danger of a collision is still here. What thoughts did the Arizona Meteor Crater (so-called Barringer Crater) awake, when it was realized that it was only 50,000 years old. And then there was the Tunguska event 1908. When it was realized that instead of the 2500 km2 of forest that it burned and knocked down it could have done the same for a big town with all its buildings and people, the attitude still was more one of curiosity than an awareness of what could happen to us. Then there came the mega-show in 1994 when 21 pieces of a comet splashed into Jupiter. The greatest caused rings that were greater than the Earth. But maybe the March 1998 awaked all people who in general are interested in these kinds of things. There was first published a letter by IAU, who regarded it possible that an asteroid, 1997 XF11 had a chance of hitting Earth in October 2028. Because of its size, 1.5 km in diameter, it is just on borderline of causing a global disaster. At least the fine infrastructure of mankind would have been destroyed and the surviving people would have had circumstances of stone age. In less than a day, Nasa announced a new calculation based on old pictures of this asteroid from years ago. It showed that XF11 will pass the Earth by a safe distance of 960,000 km or 2.5 LU (the mean distance to moon). In fairness we should remind that IAU (that immediately agreed with the NASA calculations), had in its paper asked people to make further calculations and did not declare its prediction of a possibility as the last word. According to folklore, in 1490 in China's Shanxi Province tens of thousands of people were killed from "falling stones". At the same time was the peace in Florence broken, and the peacemaker Lorenzo de Medici died in 1492, but the connection between these two events is unclear. As provoking is a German woodcut from 1493 which shows an "earthquake" of biblical proportions with totally collapsed buildings. _One rough estimate of the probability of Tunguska-size events we can get from the Spacewatch program. During years 1991-1996 it has observed 7 closer than 500,000 kilometers passes of asteroids of size from about 10 to 100 meters (the Tunguskan one was 60 meters). 4 of these were closer than the moon (in avg. 384,000 km). From this we can calculate that the average hit rate of tunguskans (10-100 m) is about once every 35 years. In fact there has been 3 (1908, 1930 and 1947), possibly 4 (Greenland 1997) tunguska-size hits during this century. _ Estimates of greater size impacts are harder to make because we have so few of them, but various extrapolations have been made. One picture can be achieved from the Harvard list of known forthcoming close approaches. _The closest known approaches before 2029 are: _ ========================================================== Toutatis (4179) 29 Sep 2004 1,550,000 km (4.0 Moon Units) 2000 UG11 09 Nov 2008 1,330,000 km (3.5 MU) 1999 MN 02 Jun 2010 1,140,000 km (3.0 MU) 1998 HH49 16 Oct 2023 1,170,000 km (3.0 MU) 1999 AN10 07 Aug 2027 397,000 km (1.03 MU) 2001 WN5 25 Jun 2028 653,000 km (1.7 MU) 1997 XF11 26 Oct 2028 930,000 km (2.4 MU) ========================================================== _Possible impacts known before 2050 down to prob. 1 to 1 million: _ NONE One must remember that these are only _known_ asteroids and even in the category "above 1 km in diameter" only about 10 % of all NEOs are known not to speak of the smaller ones. Hazards and perturbations. T. Gehrels (ed.) has in his "Hazards Due to Comets and Asteroids" an interesting article "Environmental Perturbations Caused by Asteroid Impacts" by Owen Toon and Kevin Zahnle (NASA), Richard Turco (Univ. of California, L. A.), and Curt Lovey (Lawrence Livermore Lab). "... For impactors with energies greater than about [teratons] TNT equivalent, _cooling and light loss due to dust_ lifted by the impact, as well as _fires_ set by the lofted debris as it re-enters the atmosphere, appear to be the major short-term environmental hazards." Their scenario contains 1. Dust loading: - Cooling, cessation of photosyntesis and loss of vision. 2. Fires: - Burning, soot cooling, pyrotoxins, acid rain. 3. NO(x) generation: - Ozone loss, acid rain, cooling. 4. Shock wave: - Mechanical presuure. 5. Tidal wave: - Drowning. 6. Heavy metals. - Poisoning. 7. Water/CO(2) injections: - Warming. 8. SO(2) injections: -Cooling, acid rain. _Go to the [2]Evidence of Astronomical Aspects of Mankind's Past and Recent Climate Homepage _ References Visible links 1. http://personal.eunet.fi/pp/tilmari/tilmari.htm 2. http://personal.eunet.fi/pp/tilmari/tilmari.htm Hidden links: 4. file://localhost/www/sat/files/tilmari7.htm#tunguska 5. file://localhost/www/sat/files/tilmari7.htm#cosmic 6. file://localhost/www/sat/files/tilmari7.htm#hazards