Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Sandia supercomputers offer new explanation of Tunguska disaster

19.12.2007
Smaller asteroids may pose greater danger than previously believed

The stunning amount of forest devastation at Tunguska a century ago in Siberia may have been caused by an asteroid only a fraction as large as previously published estimates, Sandia National Laboratories supercomputer simulations suggest.

“The asteroid that caused the extensive damage was much smaller than we had thought,” says Sandia principal investigator Mark Boslough of the impact that occurred June 30, 1908. “That such a small object can do this kind of destruction suggests that smaller asteroids are something to consider. Their smaller size indicates such collisions are not as improbable as we had believed.”

Because smaller asteroids approach Earth statistically more frequently than larger ones, he says, “We should be making more efforts at detecting the smaller ones than we have till now.”

The new simulation — which more closely matches the widely known facts of destruction than earlier models — shows that the center of mass of an asteroid exploding above the ground is transported downward at speeds faster than sound. It takes the form of a high-temperature jet of expanding gas called a fireball.

This causes stronger blast waves and thermal radiation pulses at the surface than would be predicted by an explosion limited to the height at which the blast was initiated.

“Our understanding was oversimplified,” says Boslough, “We no longer have to make the same simplifying assumptions, because present-day supercomputers allow us to do things with high resolution in 3-D. Everything gets clearer as you look at things with more refined tools.”

Sandia is a National Nuclear Security Administration laboratory.

The new interpretation also accounts for the fact that winds were amplified above ridgelines where trees tended to be blown down, and that the forest at the time of the explosion, according to foresters, was not healthy. Thus previous scientific estimates had overstated the devastation caused by the asteroid, since topographic and ecologic factors contributing to the result had not been taken into account.

“There’s actually less devastation than previously thought,” says Boslough, “but it was caused by a far smaller asteroid. Unfortunately, it’s not a complete wash in terms of the potential hazard, because there are more smaller asteroids than larger ones.”

Boslough and colleagues achieved fame more than a decade ago by accurately predicting that that the fireball caused by the intersection of the comet Shoemaker-Levy 9 with Jupiter would be observable from Earth.

Simulations show that the material of an incoming asteroid is compressed by the increasing resistance of Earth’s atmosphere. As it penetrates deeper, the more and more resistant atmospheric wall causes it to explode as an airburst that precipitates the downward flow of heated gas.

Because of the additional energy transported toward the surface by the fireball, what scientists had thought to be an explosion between 10 and 20 megatons was more likely only three to five megatons. The physical size of the asteroid, says Boslough, depends upon its speed and whether it is porous or nonporous, icy or waterless, and other material characteristics.

“Any strategy for defense or deflection should take into consideration this revised understanding of the mechanism of explosion,” says Boslough.

One of most prominent papers in estimating frequency of impact was published five years ago in Nature by Sandia researcher Dick Spalding and his colleagues, from satellite data on explosions in atmosphere. “They can count those events and estimate frequencies of arrival through probabilistic arguments,” says Boslough.

The work was presented at the American Geophysical Union meeting in San Francisco on Dec. 11. A paper on the phenomenon, co-authored by Sandia researcher Dave Crawford and entitled “Low–altitude airbursts and the impact threat” has been accepted for publication in the International Journal of Impact Engineering.

The research was paid for by Sandia’s Laboratory-Directed Research and Development office.

Neal Singer | EurekAlert!
Further information:
http://www.sandia.gov

More articles from Physics and Astronomy:

nachricht A 100-year-old physics problem has been solved at EPFL
23.06.2017 | Ecole Polytechnique Fédérale de Lausanne

nachricht Quantum thermometer or optical refrigerator?
23.06.2017 | National Institute of Standards and Technology (NIST)

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>