Advertisements

Blog Archives

Chelyabinsk: a Blast From the Not-Too-Distant Past (or, How’s That Space Program Coming Along?)

Dashcam video of the Chelyabinsk meteor exploding on Feb. 15, 2013 (Source: RT.com)

Dashcam video of the Chelyabinsk meteor exploding on Feb. 15, 2013 (Source: RT.com)

Four years ago today an explosion shattered the morning sky over the Chelyabinsk region in southwestern Russia, the result of a 60-foot-wide fragment of an asteroid entering Earth’s atmosphere at over 40,000 mph and brilliantly blowing itself to smithereens at 97,000 feet up. Even at that altitude, the resulting flash of light and air blast was powerful enough to cause extensive damage on the ground, shattering windows, knocking in doors, and causing injury to nearly 1,500 people across towns in the area—several of them seriously.

This was the largest observed meteor since the famous 1908 Tunguska event, but thanks to the prevalence today of dashboard and CCTV cameras in Russia this one was well-recorded. (I remember seeing the videos online within an hour after it happened!) The footage has allowed scientists to not only determine the energy of the Chelyabinsk meteor explosion—about 500 kilotons—but also the object’s trajectory and origin.

Watch a video below of footage captured from various locations of the Chelyabinsk meteor:

Read the rest of this entry

Advertisements

We Still Don’t Know What Exploded Over Tunguska in 1908

This is an article, now updated, that I originally posted in 2009 during my first year of blogging. Since then more research has been done on the famous 1908 Tunguska Event and we even had a remarkably similar type of thing occur in February 2013 over the Chelyabinsk area, not too far from Tunguska, but even today, the 108th anniversary of the event, scientists aren’t in agreement over what it was that violently exploded over the boggy forests of Siberia—asteroid or comet.

tunguska_event

Flattened trees in Siberia from a 1908 atmospheric explosion

Long the subject of debate, with various theories ranging from meteorite impact to a comet to a flying saucer’s sudden engine meltdown, there’s actually strong evidence that the 1908 “Tunguska Event” was likely caused by the explosion of a comet in the upper atmosphere.

This idea has been suggested before, and is supported by Cornell University engineering professor Michael Kelly’s study of – strangely enough – the space shuttle’s exhaust plumes and their effect on high-atmosphere cloud formation.

To those not familiar with the Tunguska Event, something exploded or impacted in the remote area of Russia on June 30, 1908, flattening the forest in an 830-square-mile area, but leaving no visible crater or other obvious sign of what caused the event. Nearby residents reported the sound of a massive explosion, but that’s about it. Whatever it was, the devastation it caused was extensive and undeniable.

Read the rest of this entry

Blast Zone

Hubble's View of Jupiter's Southern Scar

Hubble's View of Jupiter's Southern Scar

The Hubble Space Telescope trained its newly-installed Wide Field Camera 3 on Jupiter, capturing a photo of the recent impact scar made on July 19.

This image is the first taken by the new camera installed in May, and while it’s still uncalibrated, details can be seen of the dark debris plume that has spread across thousands of miles of Jupiter’s atmosphere.

It’s not known yet exactly what hit the giant planet but scientists believe it may have been a comet or wayward asteroid. The impact occurred on the side of Jupiter facing away from Earth, and when the planet eventually rotated around the impact mark was spotted by amateur astronomer Anthony Wesley from his telescope in Australia.

The scar has been slowly expanding since, Jupiter’s turbulent atmosphere distorting and spreading the dark material across its churning cloudtops.

“Details seen in the Hubble view shows a lumpiness to the debris plume caused by turbulence in Jupiter’s atmosphere.” – Amy Simon-Miller, Goddard Space Flight Center

It’s estimated that the impact was “thousands of times more powerful than the suspected comet or asteroid that exploded over the Tunguska River Valley in June 1908”. (NASA article here.) The object may have been several hundred yards across.

Image: NASA, ESA, and H. Hammel (Space Science Institute, Boulder, Colo.), and the Jupiter Impact Team.

Tunguska Mystery Solved?

tunguska_event

Flattened trees in Siberia from a 1908 atmospheric explosion

Inspired by a post on Universe Today by Nancy Atkinson: 1908 Tunguska Event Caused by Comet, New Research Reveals

Long the subject of debate, with various theories ranging from meteorite impact to a comet to a flying saucer’s sudden engine meltdown, there’s actually strong evidence that the 1908 “Tunguska Event” was likely caused by the explosion of a comet in the upper atmosphere.

This idea has been suggested before, and is now supported by Cornell University engineering professor Michael Kelly’s study of – strangely enough – the space shuttle’s exhaust plumes and their effect on high-atmosphere cloud formation.

To those not familiar with the Tunguska Event, something exploded or impacted in the remote area of Russia on June 30, 1908, flattening the forest in an 830-square-mile area, but leaving no visible crater or other obvious sign of what caused the event. Nearby residents reported the sound of a massive explosion, but that’s about it. Whatever it was, the devastation it caused was extensive and undeniable.

It has been estimated that the blast was equivalent in power to 1,000 Hiroshima-sized detonations.

Michael Kelly noted that high-altitude clouds, called noctilucent clouds (NLCs) commonly form after the entry of the space shuttle into the atmosphere. These clouds tend to reflect light from the sun long into the night, and were particularly visible on July 1, 1908, one day after the Tunguska event. In fact it was noted that many cities across Europe experienced unusually bright nights. The reflective clouds are made up of ice particles, and may have been caused by massive amounts of water vapor scattered into the cold upper atmosphere from the vapor trail and explosion of a comet, which are typically made of rock and water ice.

See images of NLCs made by the shuttle Atlantis’ launch in 2007 here.

Iss017e011632

Noctilucent clouds photographed from the Space Station (NASA)

Made up of ice formed on the surface of exhaust and dust particles, noctilucent clouds occur only at high altitudes. The researchers believe that water vapor discharged into the atmosphere by a comet’s icy center was caught up in a vortex of immense energy in a process called two-dimensional turbulence, traveling at speeds of nearly 300 feet per second—which explains why the clouds formed thousands of miles away. “It’s like solving a murder mystery,” says Kelley. “We were finishing a puzzle. The pieces were there, but we put them together.” (Source: Cornell Alumni Magazine)

The comet theory is also supported by the obvious lack of an impact crater…an icy comet would have exploded high in the atmosphere, its ice rapidly boiling and expanding upon entry, and although the shockwave would have been – was – extensive and devastating, there was little left to strike the ground. Anything that was left likely disappeared into the soft peat bogs of the Siberian tundra.

But despite the association with NLCs it’s still not known exactly what to blame for the 1908 event—comet or asteroid. Although continuing research over the years has unearthed evidence for both (with some scientists quite strongly asserting their own findings as conclusive) nothing as yet has proven to be a true “smoking gun” for either option and every finding seems to quickly get its fair share of detractors.

Regardless of an origin of comet or asteroid—or something else entirely—the Tunguska Event has been a staple of pop science enigma for decades and probably will be for many more to come.

Bookmark and Share

ADDED 2/4/11: Here’s some more articles on the event from “bad” astronomer Phil Plait:

How Often Does a Tunguska Event Happen?

100 Years Ago Today: KABLAM!!!

%d bloggers like this: