\n<\/p>\n
<\/iframe><br \/><em>Watch a video about the 1908 Tunguska explosion.<\/em><\/p>\n<h3>The Tunguska explosion: June 30, 1908<\/h3>\n<p>\u00a0<br \/>On today\u2019s date 116 years ago, the largest asteroid impact in recorded history struck on a warm summer morning in Siberia, Russia. Now, we observe Asteroid Day each year on June 30, on the anniversary of what\u2019s now known as the <em>Tunguska explosion<\/em>.<\/p>\n<p>The explosion happened over the sparsely populated northern forestland above\u00a0the Podkamennaya Tunguska River in what is present-day Krasnoyarsk Krai. <\/p>\n<p>Incredibly, the blast released enough energy to kill reindeer and flatten an estimated 80 million trees over an area of 830 square miles (2,150 square km).\u00a0Witnesses reported seeing a fireball \u2013 a bluish light, nearly as bright as the sun \u2013 moving across the sky. In addition, a flash and a sound similar to artillery fire was said to follow it. Moreover, a powerful shockwave broke windows hundreds of miles\/kilometers away and knocked people off their feet. <\/p>\n<p>Yet, ultimately, decades passed before anyone could explain the event.<\/p>\n<figure id=\"attachment_339444\" aria-describedby=\"caption-attachment-339444\" style=\"width: 800px\" class=\"wp-caption aligncenter\"><figcaption id=\"caption-attachment-339444\" class=\"wp-caption-text\">Map showing the approximate location of the Tunguska event of 1908 in Siberia, Russia. Image via Wikimedia Commons\/ CC BY-SA 3.0.<\/figcaption><\/figure>\n<h3>Tunguska explosion largest in recorded history<\/h3>\n<p>A mysterious aspect of the Tunguska event was that, surprisingly, no one ever found a crater. But, even without a crater, scientists still categorized it as an impact event. They now believe the incoming object never struck Earth. Instead, it exploded in the atmosphere, causing what\u2019s known as an <em>air burst<\/em>. This type of atmospheric explosion was still enough to cause massive damage to the forest in the region. <\/p>\n<p>Scientists determined the object was most likely a stony asteroid approximately the size of a 25-story building, traveling at a speed of about 33,500 miles (54,000 km) per hour and exploded 3 to 6 miles (5 to 10 km) above Earth\u2019s surface. <\/p>\n<p>The Tunguska explosion was equal to about 4 megatons of TNT. That would make it 250 times more powerful than the atom bomb dropped on Hiroshima.<\/p>\n<figure id=\"attachment_339440\" aria-describedby=\"caption-attachment-339440\" style=\"width: 800px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-339440\" src=\"https:\/\/earthsky.org\/upl\/2019\/06\/Tunguska-fallen-trees-1927-1.jpg\" alt=\"Black and white photo of blasted forest with mostly fallen, some standing tree trunks stripped of limbs.\" width=\"800\" height=\"613\" srcset=\"https:\/\/earthsky.org\/upl\/2019\/06\/Tunguska-fallen-trees-1927-1.jpg 450w, https:\/\/earthsky.org\/upl\/2019\/06\/Tunguska-fallen-trees-1927-1-300x230.jpg 300w, https:\/\/earthsky.org\/upl\/2019\/06\/Tunguska-fallen-trees-1927-1-190x146.jpg 190w, https:\/\/earthsky.org\/upl\/2019\/06\/Tunguska-fallen-trees-1927-1-140x107.jpg 140w\" sizes=\"auto, (max-width: 800px) 100vw, 800px\"\/><figcaption id=\"caption-attachment-339440\" class=\"wp-caption-text\">Fallen trees from the 1908 Tunguska explosion at Tunguska in Siberia. It wasn\u2019t until 1927 that Russian scientists \u2013 led by Leonid Kulik \u2013 were finally able to get to the scene. Photo via the Soviet Academy of Science\/ Leonid Kulik.<\/figcaption><\/figure>\n<h3>Understanding the Tunguska explosion<\/h3>\n<p>Why did it take so long \u2013 the better part of the 20th century \u2013 for scientists to understand what caused the Tunguska event? For one thing, it was almost two decades before the first scientists reached this remote region of Siberia. In 1927, Leonid Kulik led the first Soviet research expedition to investigate the Tunguska event. He made an initial trip to the region, interviewing local witnesses and exploring the area of fallen trees. <\/p>\n<p>But Kulik did not find any meteorite fragments or an impact crater.<\/p>\n<p>As a result of Kulik\u2019s initial investigation, some concocted wild theories to explain the Tunguska event. People claimed a stricken alien spacecraft caused the destruction. In addition, later, they pointed to a mini-black-hole, or a particle of antimatter. <\/p>\n<p>The truth is just as interesting, and perhaps more terrifying \u2026 because it can happen again. <\/p>\n<figure id=\"attachment_146873\" aria-describedby=\"caption-attachment-146873\" style=\"width: 650px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-146873\" src=\"https:\/\/earthsky.org\/upl\/2002\/09\/air_burst_lg.jpeg\" alt=\"Tunguska explosion: Brilliantly glowing spherical burst of flame and smoke in midair.\" width=\"650\" height=\"813\" srcset=\"https:\/\/earthsky.org\/upl\/2002\/09\/air_burst_lg.jpeg 480w, https:\/\/earthsky.org\/upl\/2002\/09\/air_burst_lg-240x300.jpeg 240w, https:\/\/earthsky.org\/upl\/2002\/09\/air_burst_lg-190x237.jpeg 190w, https:\/\/earthsky.org\/upl\/2002\/09\/air_burst_lg-140x175.jpeg 140w, https:\/\/earthsky.org\/upl\/2002\/09\/air_burst_lg-300x375.jpeg 300w\" sizes=\"auto, (max-width: 650px) 100vw, 650px\"\/><figcaption id=\"caption-attachment-146873\" class=\"wp-caption-text\">Photo of an air burst, in this case from a U.S. Navy submarine-launched Tomahawk cruise missile. A similar kind of air burst from an incoming asteroid or comet flattened the trees in Siberia in 1908. Image via Wikimedia Commons\/ public domain.<\/figcaption><\/figure>\n<h3>The Chelyabinsk meteor impact<\/h3>\n<p>In fact, the Tunguska event basically did happen again, just on a smaller scale, with the Chelyabinsk meteor, 105 years later. On February 15, 2013, a similar, although smaller, airburst occurred over the city of Chelyabinsk, Russia, 1,500 miles (2,400 km) to the west of Tunguska. <\/p>\n<blockquote class=\"twitter-tweet\">\n<p lang=\"en\" dir=\"ltr\">Deborah Byrd : <\/p>\n<p>Vapor trail left by the Chelyabinsk meteor, as captured by Flickr user Alex Alishevskikh.<\/p>\n<p>Many people were driving and st\u2026 <a rel=\"nofollow\" href=\"https:\/\/t.co\/2tT1CIwIfy\">pic.twitter.com\/2tT1CIwIfy<\/a><\/p>\n<p>\u2014 Sky Observer (@SkyObserve) <a rel=\"nofollow\" href=\"https:\/\/twitter.com\/SkyObserve\/status\/905115484416204800?ref_src=twsrc%5Etfw\">September 5, 2017<\/a><\/p>\n<\/blockquote>\n<p><iframe loading=\"lazy\" title=\"ScienceCasts: What Exploded Over Russia?\" width=\"1110\" height=\"624\" src=\"https:\/\/www.youtube.com\/embed\/-qZ6oiaSm00?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" referrerpolicy=\"strict-origin-when-cross-origin\" allowfullscreen><\/iframe><span style=\"display: inline-block; width: 0px; overflow: hidden; line-height: 0;\" data-mce-type=\"bookmark\" class=\"mce_SELRES_start\">?<\/span><span data-mce-type=\"bookmark\" style=\"display: inline-block; width: 0px; overflow: hidden; line-height: 0;\" class=\"mce_SELRES_start\">?<\/span><\/iframe><\/p>\n<p>The Chelyabinsk event provided vital clues as to what happened during the Tunguska event. As NASA explained, new evidence arrived to help solve the mystery of Tunguska:<\/p>\n<blockquote>\n<p>This highly documented fireball created an opportunity for researchers to apply modern computer modeling techniques to explain what was seen, heard and felt.<\/p>\n<p>The models were used with video observations of the fireball and maps of the damage on the ground to reconstruct the original size, motion and speed of the Chelyabinsk object. The resulting interpretation is that Chelyabinsk was most likely a stony asteroid the size of a five-story building that broke apart 15 miles (24 kilometers) above the ground. This generated a shock wave equivalent to a 550-kiloton explosion. The explosion\u2019s shockwave blew out roughly a million windows and injured more than a thousand people. Fortunately, the force of the explosion was not enough to knock down trees or structures.<\/p>\n<p>Per current understanding of the asteroid population, an object like the Chelyabinsk meteor can impact the Earth every 10 to 100 years on average.<\/p>\n<\/blockquote>\n<figure id=\"attachment_339499\" aria-describedby=\"caption-attachment-339499\" style=\"width: 800px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/earthsky.org\/upl\/2020\/06\/Tunguska-and-Chelyabinsk-size-comparison-e1593467655241.png\" alt=\"Silhouettes of two tall buildings and two smaller spheres all marked with size in meters.\" width=\"800\" height=\"743\" class=\"size-full wp-image-339499\"\/><figcaption id=\"caption-attachment-339499\" class=\"wp-caption-text\">Chelyabinsk and Tunguska, in relation to the Empire State Building and the Eiffel Tower. Image via Wikimedia Commons\/ CC BY-SA 4.0.<\/figcaption><\/figure>\n<h3>Studying the Tunguska explosion to prepare for future events<\/h3>\n<p>In 2019, scientists published new research about the Tunguska event in a series of papers in a special issue of the journal <em>Icarus<\/em>. A workshop held at NASA\u2019s Ames Research Center in Silicon Valley and sponsored by the NASA Planetary Defense Coordination Office inspired the research. <\/p>\n<p>The theme of the workshop was <em>Reexamining the astronomical cold case of the 1908 Tunguska impact event<\/em>.<\/p>\n<p>Read more about NASA\u2019s research on the Tunguska explosion<\/p>\n<p>In recent decades \u2013 due to the Tunguska event, and other, smaller impacts \u2013 astronomers have come to take the possibility of catastrophic comet and asteroid impacts seriously. They now have observing programs to watch for near-Earth objects (NEOs), as they\u2019re called. At regular meetings they discuss what might happen if we do find a large object on a collision course with Earth. <\/p>\n<h3>DART\u2019s successful asteroid mission<\/h3>\n<p>DART \u2013 the <em>Double Asteroid Redirect Test<\/em> \u2013 was a huge hit, quite literally. The spacecraft smashed into an asteroid moon \u2013 called Didymos B, or Dimorphos \u2013 on September 26, 2022. The goal was to prove that we can send a spacecraft <em>to push an asteroid<\/em> slightly in its orbit. It was practice for a possible future scenario in which we find a hazardous asteroid barreling toward Earth. NASA said on October 11, 2022, that analysis of data obtained from the DART mission shows the spacecraft did, indeed, successfully alter the orbit of Dimorphos.<\/p>\n<h3>Future asteroid mission<\/h3>\n<p>ESA\u2019s Hera mission is due to launch\u00a0in October 2024. The Hera mission will journey to Didymos to study DART\u2019s impact.<\/p>\n<p>Lorien Wheeler, a researcher at NASA Ames Research Center, working on NASA\u2019s Asteroid Threat Assessment Project, said:<\/p>\n<blockquote>\n<p>Because there are so few observed cases, a lot of uncertainty remains about how large asteroids break up in the atmosphere and how much damage they could cause on the ground. However, recent advancements in computational models, along with analyses of the Chelyabinsk and other meteor events, are helping to improve our understanding of these factors so that we can better evaluate potential asteroid threats in the future.<\/p>\n<\/blockquote>\n<p>Astronomer David Morrison, also at NASA Ames Research Center, commented:<\/p>\n<blockquote>\n<p>Tunguska is the largest cosmic impact witnessed by modern humans. It also is characteristic of the sort of impact we are likely to have to protect against in the future.<\/p>\n<\/blockquote>\n<p>Bottom line: The Tunguska explosion on June 30, 1908, was the largest asteroid impact in recorded history. It flattened 830 square miles (2,150 sq km) of Siberian forest. Researchers are preparing for future Tunguska-sized events.<\/p>\n<p>Source: Icarus special papers on Tunguska<\/p>\n<p>Via Forbes<\/p>\n<p>Via NASA <\/p>\n<p>Read more: Detecting asteroids near the sun with NEOMIR<\/p>\n<p><span class=\"cp-load-after-post\"\/><\/div>\n<div>\n<div class=\"post-author\">\n<h4>Kelly Kizer Whitt<\/h4>\n<p> View Articles\n <\/p><\/div>\n<div class=\"post-tags\">\n<h6 data-udy-fe=\"text_7c58270d\">About the Author:<\/h6>\n<p>Kelly Kizer Whitt has been a science writer specializing in astronomy for more than two decades. She began her career at Astronomy Magazine, and she has made regular contributions to AstronomyToday and the Sierra Club, among other outlets. Her children\u2019s picture book, Solar System Forecast, was published in 2012. She has also written a young adult dystopian novel titled A Different Sky. When she is not reading or writing about astronomy and staring up at the stars, she enjoys traveling to the national parks, creating crossword puzzles, running, tennis, and paddleboarding. Kelly lives in Wisconsin.<\/p>\n<\/p><\/div>\n<\/p><\/div>\n<p><script async src=\"https:\/\/platform.twitter.com\/widgets.js\" charset=\"utf-8\"><\/script><br \/>\n<br \/><br \/>\n<br \/><a href=\"https:\/\/earthsky.org\/space\/what-is-the-tunguska-explosion\/?rand=772280\">Source link <\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Watch a video about the 1908 Tunguska explosion. The Tunguska explosion: June 30, 1908 \u00a0On today\u2019s date 116 years ago, the largest asteroid impact in recorded history struck on a… <\/p>\n","protected":false},"author":1,"featured_media":785018,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[46],"tags":[],"class_list":["post-785017","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-earth-sky"],"_links":{"self":[{"href":"https:\/\/spaceweekly.com\/index.php?rest_route=\/wp\/v2\/posts\/785017","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/spaceweekly.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/spaceweekly.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/spaceweekly.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/spaceweekly.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=785017"}],"version-history":[{"count":0,"href":"https:\/\/spaceweekly.com\/index.php?rest_route=\/wp\/v2\/posts\/785017\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/spaceweekly.com\/index.php?rest_route=\/wp\/v2\/media\/785018"}],"wp:attachment":[{"href":"https:\/\/spaceweekly.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=785017"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/spaceweekly.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=785017"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/spaceweekly.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=785017"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}