Tunguska

On June 30th 1908 a powerful explosion shook the region of Russia know as Siberia, near Tunguska The force of the blast was 1000 times more powerful than that of the Hiroshima bomb, registering a 5 on the Reciter scale, and leveling an estimated 80 million trees. Many questions have been raised over the years as to what may have been the cause of this great event. On April 29th 2013,  Russian scientist, Dr, Andrei Zlobin submitted a paper that announced that he had obtained the first evidence of a possible impactor.

In 1988, Dr. Zlobin went on an expedition to the Tunguska impact site. It was there that he found about 100 rocks that appeared to be meteorite fragments at the bottom of the Khushmo River's shoal. However, Dr. Zlobin didn't examine his find until 20 years later in 2008. When he finally examined the stones he found three which showed clear signs of melting and regmalypts, or thumb like impressions on their surface. These impressions are what are found on meteorites and are caused by ablation as a hot meteor or asteroid falls through the earth's atmosphere at high velocity. Using tree ring evidence to estimate the heat of the blast, Dr. Zlobin determined that the heat was was not hot enough to melt rocks or stones already on the ground. Therefore, he concluded that the stones were most likely fragments of whatever had fallen to Earth over Tunguska.

Dr. Zlobin has gone on to say, that a detailed chemical analysis has not yet been done, so the nature of the body that fell will take a little more time before it is known. However, Dr. Zlobin believes that it could have been a comet because comets often have a nucleus that contains rock fragments. He has estimated the density of the impactor to be 0.6 grams per cubic centimeter which is the same as Halley's comet.

While it's clear that there is still more work to be done in order to confirm that the stones came from space, the fact that they have been preliminarily identified as remnants of a possible and/or a probable impactor, may help to shed some light on what caused the explosion. It may also help in determining what type of damage we could expect in any future collisions, and what our chances are for surviving such events.

Many near Earth objects are now being monitored and a vigil is being kept in order to determine if any of those object might someday be on a collision course with the Earth. As they say, it's not a question of if, it's matter of when.