Stories tagged Tunguska event

Mars: Is the Red Planet on a collision course with an asteroid?
Courtesy NASAThe planet Mars may be in for a collision from an asteroid headed its way. Scientists from NASA have been tracking the 160-foot-wide asteroid for some time now, and say the odds of it hitting the Red Planet are about 1 in 75. Back in 1908, Earth was hit by a similar asteroid, near Tunguska, Siberia. That impact flattened millions of trees and is thought to have left a crater that is now a lake.

I remember the excitement I felt peering through my brother's telescope and seeing the effects of the Shoemaker-Levy comet when it collided with Jupiter back in July of 1994. You could just make out some of the dark holes punched into Jupiter's surface from the comet fragments. Very exciting considering we were witnessing it from over half a billion miles away.

The view of this possible impact could even be better. The Mars Reconnaissance Orbiter, currently mapping the Martian surface, could capture a the best view of such an event - unless by chance this thing impacts in range of the cameras of one of the two rovers, Spirit and Opportunity, currently exploring the planet's environs.

If a collision does take place, it's expected to happen on January 30, 2008, which by the way is my birthday. What a great present that would be!

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Associated Press story

Tags : mars, meteors, asteroid, Tunguska event

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Fallen Trees at Tunguska site: 1927 Kulik expeditionA team of scientists may have finally found a possible impact crater from the Tunguska event that blasted above Siberia nearly a century ago.

Map showing Tunguska event location: Image source: Public DomainOn June 30, 1908, some sort of extraterrestrial object, such as a comet or an asteroid (at least according to the consensus), exploded in Earth’s atmosphere above the Tunguska River with such force that it flattened more than 2000 square miles of forest. But until now, no viable impact site had ever been found.

This whole Tunguska thing is cloaked in so much mystery and mythology, that agents Muldar and Scully could do a whole X-Files episode about it (in fact, they did). Well, the truth may be out there, but there’s a whole lot of it that remains unknown.

What’s is known is that something big exploded over the Tunguska river region in 1908. The place, unfortunately, is so out-in-the-middle-of-nowhere; it wasn’t scientifically investigated until more than two decades later when mineralogist Leonid Kulik led the first official expedition into the region in 1927. Kulik had initially come upon the site six years earlier when he doing a survey for the Soviet Academy of Sciences. Local eyewitness accounts convinced him that the explosion had been caused by an enormous meteorite impact, and he persuaded the Soviet government to fund the expedition in hopes of salvaging meteoric iron for Soviet industry. But to his disappointment, no possible impact crater was ever located (except in one bare location that later proved to be just a bog). What the expedition did find was a huge area of forest flattened out in a butterfly pattern. Oddly, the only trees still standing were located at ground zero, but those had been stripped bare of all their leaves and bark.

Kulik didn’t find any chunks of iron either, although later expeditions did find microscopic traces of nickel and iron in the soil.

But now, a University of Bologna team of scientists claims that Lake Cheko, which is located just 5 miles north-northwest of the explosion’s epicenter, shows some interesting features that could be interpreted as resulting from some sort of impact, perhaps from a small chunk of the disintegrating space rock – if that’s what it was. The team’s research appears in the online journal Terra Nova.

But other scientists aren’t jumping on the bandwagon just yet. For one thing the lake exhibits almost none of the usual telltale physical markings of an impact crater, other than being uniquely funnel-shaped unlike other neighboring lakes. And even then, its shape is more elliptical than circular. Cheko’s rim is not raised and lacks any sign of upturned ejecta. The scientists have found no shocked terrestrial rock in or around the lake, and to date no meteoric material either. And even if some is found, skeptics say it could have washed into the lake from the surrounding landscape. Also, trees older than a hundred years old are still standing near the lake. If Cheko were an impact crater, the force of the collision would have knocked them all down. It’s true that the lake doesn’t appear on any map prior to 1929, but the region is extremely remote, and there is some folklore evidence of its existence before then.

Other scientists speculate that the source of the event wasn’t from outer space at all, but rather was caused by geophysical forces, such as a cataclysmic gas blow out from deep inside the Earth. It just so happens that the Tunguska event epicenter sets at the intersection of a number of tectonic faults, and atop the ancient crater of a paleovolcano. Kimberlite pipes are also found in the area, an indication of magma reservoirs deep beneath the surface. And evidently there was a lot of earthquake activity in the Tunguska epicenter region back in 1908.
Andrei Ol'khovatov, a former Soviet scientist who is now -in his own words- “an independent researcher/expert” on everything Tunguska, has an entire website addressing this and other possibilities about the event. He has participated in a number of International Tunguska conferences, and I found his site very interesting to peruse.

So, whatever the Tunguska event was, whether it was a comet or asteroid, a UFO, an errant radio transmission, or the real cause of global warning - it exploded about 3-6 miles above the ground, knocked down a whole lot of lumber, scared the dickens out of the locals, and illuminated the sky so brightly it could be seen in London, a third of the way around the globe!

The Italian team plans to return to Lake Cheko in 2008 to perform further tests, including drilling into the core of the lake to examine an anomaly detected some 10 meters below the lake bottom. It could be a meteorite fragment or maybe just some compacted mud. I guess we’ll have to wait and see.

MORE INFO

More on the Tunguska event
The Tunguska event in fiction
BBC website story
Lake Cheko story on Sky& Telescope website

Tags : asteroid, extraterrestrial impact, Tunguska event, impact crater

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