As of Today according to Near-Earth asteroid monitoring groups
the ever-increasing number of
KNOWN Potentially Hazardous Asteroids
in Earth-Crossing orbits
“An excellent introduction into the newly emerging and exciting field of astrobiology. An essential, enjoyable and highly readable insight into life in its cosmic context.”
“Astrobiology involves the study of the origin and history of life on Earth, planets and moons where life may have arisen, and the search for extraterrestrial life. It combines the sciences of biology, chemistry, palaeontology, geology, planetary physics and astronomy. This textbook brings together world experts in each of these disciplines to provide the most comprehensive coverage of the field currently available.”
“This up-to-date resource is based on lectures developed by experts in the relevant fields and carefully edited by the leading astrobiologists within the European community. Aimed at graduate students in physics, astronomy and biology and their lecturers, the text begins with a general introduction to astrobiology, followed by sections on basic prebiotic chemistry, extremophiles, and habitability in our solar system and beyond.”
“The dynamic field of astrochemistry brings together ideas of physics, astrophysics, biology and chemistry to the study of molecules between stars, around stars and on planets. Astrochemistry: from Astronomy to Astrobiology provides a clear and concise introduction to this rapidly evolving multidisciplinary subject. Starting with the Molecular Universe, the text covers the formation of the elements, simple models of stars and their classification. It then moves on to draw on the theme of the Origins of Life to study interstellar chemistry, meteorite and comet chemistry as well as the chemistry of planets.”
“This highly interdisciplinary book highlights many of the ways in which chemistry plays a crucial role in making life an evolutionary possibility in the universe. Cosmologists and particle physicists have often explored how the observed laws and constants of nature lie within a narrow range that allows complexity and life to evolve and adapt. Here, these anthropic considerations are diversified in a host of new ways to identify the most sensitive features of biochemistry and astrobiology. Celebrating the classic 1913 work of Lawrence J. Henderson, The Fitness of the Environment for Life, this book looks at the delicate balance between chemistry and the ambient conditions in the universe that permit complex chemical networks and structures to exist.”
“Astrobiology: A Multidisciplinary Approach is the most comprehensive textbook available for emerging upper-level courses in astrobiology. Internationally renowned authority Jonathan Lunine gives students with a variety of backgrounds a solid foundation in the essential concepts of physics, chemistry, biology, and other relevant sciences to help them achieve a well-rounded understanding of the fascinating study of the origin of life, planetary evolution, and life in the cosmos.”
“Asteroids and comets: Every year, millions of these ‘stray bullets’ streak through the skies, and tons of small meteorites strike our planet! Some 65 million years ago, dinosaurs were wiped off the face of the earth – in what many believe was the aftermath of a massive cosmic collision. Could something like this happen again? Scientists believe that the impact of an asteroid only a mile wide would be globally catastrophic.”
“Comet science is a field that has seen tremendous advances in recent years, far surpassing the knowledge reflected in the original Comets volume published as part of the Space Science Series in 1982. This new volume, with more than seventy contributing authors, contains the most extensive collection of knowledge yet assembled in the field. It will enable scientists involved in their study to make connections across disciplinary boundaries and will set the stage for discovery and new understanding in the coming years.”
“Comet Hale-Bopp defines a milestone event for cometary science: it is the first “really big” comet observed with modern equipment on the ground and from space and due to that; it is considered the new reference object in cometary sciences. At the beginning of a new era in spacecraft exploration of comets and five years after Hale-Bopp’s perihelion passage these proceedings of invited and contributed papers for IAU Colloquium 186 “Cometary Science after Hale-Bopp” review the state-of-the-art knowledge on comets, the icy, dusty and most primordial left-overs of the formation disk of our own solar system.”
“Around 700 BC an Assyrian scribe in the Royal Place at Nineveh made a copy of one of the most important documents in the royal collection. Two and a half thousand years later it was found by Henry Layard in the remains of the palace library. It ended up in the British Museum’s cuneiform clay tablet collection as catalogue No. K8538 (also called ‘the Planisphere’), where it has puzzled scholars for over a hundred and fifty years.
In this monograph Bond and Hempsell provide the first comprehensive translation of the tablet, showing it to be a contemporary Sumerian observation of an Aten asteroid over a kilometre in diameter that impacted Kofels in Austria in the early morning of 29th June 3123 BC.”
For many years academics in the historical sciences were content in their belief that terrestrial impacts by solid bodies from space was something that only happened in the very early history of our planet, whilst the average person had never heard the word ‘asteroid’. Then in 1980 the Nobel prizewinning physicist, Luis Alvarez, and his colleagues published their famous paper in “Science” which argued that a cosmic impact had led to the extinction of the dinosaurs. He showed that large amounts of the element iridium present in geological layers dating from about 65 million years BP had a cosmic origin, and proposed a radical theory that it was a massive ‘asteroid impact’ 65 million years ago which finally wiped out the dinosaurs.
Over the following decade interest began to rise in the idea of ‘terrestrial impacts’, and by 1990 most scientists at least accepted that the craters on our Moon were caused by impacts of cometary debris and asteroids of varying sizes, and not the volcanoes they had previously thought responsible.
As space exploration continued, the images sent back to Earth, especially by the Voyager spacecraft, allowed astronomers to build a picture of the sort of dynamic solar system first suggested by Victor Clube and Bill Napier in their groundbreaking books “Cosmic Serpent”, published 1982, and developed further in “Cosmic Winter” published 1990.
This was a new model of the solar system. One where regular influxes of comets from the various areas of space transitted by our solar system in its orbit through the galaxy suggested inevitable, and multiple, collisions with all the planetary bodies and their respective moons. Technologicl advances in space imaging have since shown a multitude of impact craters on all the inner planets and their moons. But some 12 years after the theories about the cosmic impact which led to the extinction of the dinosaurs were first proposed, the possibility of cometary bombardments still seemed something that belonged way back in the very early history of our solar system – even to most scientists.
It was on March 24 1993 that astronomers, husband and wife team Carolyn S. and Eugene M. Shoemaker, and David H. Levy, discovered a new comet in our solar system. Observations over the next few months determined that the comet was, at least temporarily, in orbit around Jupiter, and that on July 7 1992 the tidal forces of the largest planet in our solar system had caused the comet, by then named P/Shoemaker-Levy 9, to disintegrate. Over the next year or so astronomers on Earth observed the fragments proceeding around the Sun and heading back on a collision course directly for Jupiter. From July 16th to 22nd 1994 they watched in awe as the 21 fragments bombarded the visible surface of Jupiter causing ‘fireballs’ 50 times the size of Earth and leaving huge scars on Jupiter’s southern hemisphere.
This was a wake-up call even for those who understood what was going on, and resulted in more funding being requested by astronomers to research the frequency of impacts throughout the solar system, but also to search for any evidence of past impacts on Earth. Following this event, there was an abrupt realisation by astonomers that if it can happen to Jupiter now, it can also happen to Earth in the future, and the search began in earnest to identify the exact orbital paths of all Earth-orbit-crossing celestial objects.
If anyone is in any doubt as to exactly how dangerous a place our planet occupies in the solar system they should simply look at our Moon. There for all to see with the naked eye, and in even greater detail using a pair of good binoculars or a small telescope, are impact craters galore. There doesn’t appear to be one square mile of the lunar surface that is not pockmarked with impact craters, and while some are undoubtedly very ancient they also contain within their crater rims a multitude of newer craters from much more recent impacts. The reason why there are so many visible craters on the Moon from ancient impacts was summed up well by astronomer, Duncan Steel, in his 1995 book,
“Rogue Asteroids and Doomsday Comets”:
“Craters are relatively swiftly eroded on Earth by rain, snow, and wind, whereas on the Moon they remain for eons until a new projectile happens to erase the scar left by some cousin countless millennia before.”
So this explains, partially, why there are so few visible craters on Earth. But raises the obvious question as to why we can’t see more given that, if our Moon is so cratered, surely our planet must be an even bigger target in the same area of the solar system? The answer is at once simple and also very complex. Firstly, there is approximately 71% of the surface area of the Earth covered with oceans – leaving just 29% dry land surface area. This gives a 3 to 1 chance that any incoming impactor will, if it doesn’t explode a few miles up like whatever happenned at Tunguska in 1908, impact one of the oceans and leave no easily visible trace.
Secondly, any crater on dry land would be at the mercy of the elements, and should there have been collisions with cometary debris, or asteroids, in the Amazon Basin, say, then vegetation would without doubt obscure them in a very short time indeed. But these are not the only factors, as Duncan Steel explained:
“The length of time that a crater will survive depends not only on the regions in which it is formed, but also on it’s size. Obviously a crater 50 kilometers across will last longer than a comparatibe pipsqueak just 100 meters in diameter. For example, in Australia there are 19 known craters – probably there are dozens more awaiting discovery – and of those, four are less than about 6,000 years old. Those are the four smallest however, all being less than 200 meters in diameter.”
At the time that Duncan Steel was writing “Rogue Asteroids and Doomsday Comets” in 1994/1995, there were then only about 140 known terrestrial impact craters. But in the years since then, spurred on by a new-found sense of urgency following the events on Jupiter in July 1994, the search picked up steam, and many more have been discovered.
The current tally is just under 1000, and there is an interactive map of all the terrestrial impact craters accessible at the University of Arizona website. This is an excellent resource for anyone wishing to see just how many have so far been discovered on just the 29% of the surface area of our planet that is currenly dry land.
Another good resource for information about terrestrial impact craters which also has an interactive map is accessible at the University of New Brunswick Canadian website. The first paragraph or so of their introduction to the subject is worth quoting from here, as it puts the dynamic history of the solar system into a proper perspective:
“Until recently, impacts by extraterrestrial bodies were regarded as an interesting but, perhaps, not an important phenomenon in the spectrum of geological process affecting the Earth. Our concept of the importance of impact processes, however, has been changed radically through planetary exploration, which has shown that virtually all planetary surfaces are cratered from the impact of interplanetary bodies. It is now clear from planetary bodies that have retained portions of their earliest surfaces that impact was a dominant geologic process throughout the early solar system.
For example, the oldest lunar surfaces are literally saturated with impact craters, produced by an intense bombardment which lasted from 4.6 to approximately 3.9 billion years ago, at least a 100 times higher than the present impact flux. The Earth, as part of the solar system, experienced the same bombardment as the other planetary bodies.”
On this page we have tried to compile a photographic collection of impact craters on Earth to demonstrate just how many there actually are. Asteroids vary in their composition. Some are composed purely of stoney materials, some are composed of nickel & iron, while others have varying combinations of both. It should be understood that many of the asteroids which are made up of stoney materials do not survive the journey through our atmosphere. They explode in the upper atmosphere as the white-hot matter caused by friction upon entry hits the freezing cold air.
This has happened as recently as 1908 over the Tunguska region of Siberia, where the ‘air-burst’ caused an explosion the equivalent of many hundreds of nuclear bombs. Because the asteroid, or fragment of cometary debris, detonated in the upper atmosphere there was no impact crater to show what had happened, but many thousands of square miles of forest lands were completely flattened all around the
detonation area.
The Tunguska airburst, Siberia – June 1908
How many times has this happened before? And how soon will it be before an something like this happens again? …
Click the image below or the headline above to access this story
NASA
Imagine staring into the sky and seeing a tiny yellow dot, gradually getting closer. That dot doubles in size every second, until it slowly darkens the sky. You realize that this dot is actually the size of New York City and is screeching through the atmosphere faster than the speed of sound, coming right for you. This massive object will cause tsunamis, earthquakes and obliterate natural daylight for years … oh … and it will kill you.
Similar asteroid impacts have and will happen on numerous occasions in our earth?s history. Today we?ll show you the biggest impact craters by diameter.
Over 100 Years Since The Tunguska Event
June 30, 1908
Taken during the 1927 Leonid Kulik expedition, this photograph shows trees destroyed by the blast nearly 20 years before
It has now been 100 years since the events of June 30, 1908, when a bolide of some description exploded over the Tunguska River region of Siberia. A conference to mark the anniversary took place in Moscow, Russia in 2008.
One hundred years ago, an explosion bigger than an atomic bomb blasted Tunguska, Siberia. We still don’t know what caused it, but there are plenty of theories!
In 1991, Italian scientists still found evidence of fallen trees near the blast site
University of Bologna
Early on the morning of June 30, 1908, a massive explosion rocked the Siberian wilderness flattening more than 2,000 square kilometres of forest.
Villagers 100 kilometres away from the Podkamennaya Tunguska river basin reported seeing a fireball in the sky, feeling intense heat, hearing loud thumps and being thrown off their feet.
‘The split in the sky grew larger, and the entire Northern side was covered with fire. At that moment I became so hot that I couldn’t bear it, as if my shirt was on fire; from the northern side, where the fire was, came strong heat.’
‘I wanted to tear off my shirt and throw it down, but then the sky shut closed, and a strong thump sounded, and I was thrown a few yards’, reported one villager.
The explosion lit up the sky as far away as London for several days.
Nearly two decades later, the first expedition into the area led by Russian meteorite specialist Leonid Kulik found a region of scorched trees 50 km in diameter, but no crater.
It’s now believed that the Tunguska event ? as it’s now known ? was hundreds of times more powerful than the atomic bomb dropped on Hiroshima
Tunguska has long fascinated scientists, enthusiasts and sci-fi fans. Over the years, the mystery of the event has prompted a number of theories with varying degrees of scientific plausibility. These have ranged from a meteorite to the crash of an alien spacecraft; an explosion of methane or the result of Nikola Tesla’s experiments with electricity near New York.” [Full Story]
Geographic Distribution of Known Impact Structures
Lunar & Planetary Institute
Terrestrial & Solar System
Impacts and Impact Craters
November 25 2014, NASA Earth Observatory, Earth Orbit
“A small asteroid disintegrates in Earth’s atmosphere about every other week, and the distribution around the world appears to be random.
That is the main message of a map released in November 2014 by NASA’s Near-Earth Object (NEO) observation program.
Newly Released Map Data Shows Frequency of Small Asteroid Impacts
The new data could help scientists refine estimates of the distribution of asteroids near Earth, including larger ones that could pose a danger.
The map above indicates the locations where small asteroids crashed into Earth’s atmosphere between 1994 and 2013. Each of these 556 events resulted in a very bright meteor—also known as a bolide or fireball.
On the map, orange dots represent daytime impacts and blue represents nighttime.
The size of each dot is proportional to the radiated energy of the fireball, measured in billions of Joules (GigaJoules).
The map includes asteroids/meteors ranging from about 1 meter (3 feet) to almost 20 meters (65 feet); it does not include objects smaller than a meter.”
October 27 2014, ESA News, France
“Mars is peppered with craters. Scientists have deduced that the red planet is struck by around 200 meteoroids every year that dig out new craters.
While some small craters are fresh, Mars has a great many that are much larger and more ancient, such as the roughly circular patch of terrain, partially encircled by wrinkled cliffs, shown at the centre of this image.
Named Atlantis basin, this crater is so old that its outer rim has eroded and is now barely detectable.
It is thought to be the result of a massive collision some 4 billion years ago, during the ?Late Heavy Bombardment? ? a period when an unusually high number of asteroids rained down on the rocky inner Solar System planets.
The Atlantis basin is located in the southern highlands of Mars.
Many different structures and geological features can be found across this region of the planet, a number of which are shown in this image such as cliffs, impact craters, channels carved into steep slopes, wrinkled ridges and scarps.”
September 29 2014, ESA News, France
“The greyscale pattern of dark and light blotches on the Moon is a familiar sight to stargazers.
However, there are regions that remained relatively mysterious to us until surprisingly recently ? most notably the Moon?s polar regions, which astronomers have dubbed ?Luna Incognita?, or ?the unknown Moon?.
In recent years, missions including ESA?s SMART-1 have shed light on these regions of the lunar surface, and they are now better known.
This mosaic covers about 700 km by 220 km and was taken by the Advanced Moon Imaging Experiment on SMART-1.
It shows a trio of craters very near to the Moon?s north pole, on the edge of the Luna Incognita. From right to left, these craters are named Plaskett, Rozhdestvenskiy and Hermite.
Hermite (104 km diameter) is perched right on the edge of the Moon?s northern limb, while Plaskett (109 km diameter) and Rozhdestvenskiy (177 km diameter) overlap the lunar far side.”
September 19 2014, ESA News, France
“Over billions of years, the southern uplands of Mars have been pockmarked by numerous impact features, which are often so closely packed that they overlap.
One such feature is Hooke crater, shown in this frost-tinged scene, imaged by ESA?s Mars Express during winter in the southern hemisphere.
Hooke crater is located near the northern edge of the 1800 km-wide Argyre basin ? one of the most impressive impact structures on Mars, excavated in a giant collision about 4 billion years ago.
Sitting in a flat part of the basin known as Argyre Planitia, Hooke crater has a diameter of 138 km and a maximum depth of about 2.4 km.
It is named after the English physicist and astronomer Robert Hooke (1635?1703).
Hooke crater comprises two different impact structures, with a smaller impactor blasting a depression off-centre in the floor of a larger, pre-existing crater.”
August 18 2014, ESA News, France
“Scarring the southern highlands of Mars is one of the Solar System?s largest impact basins: Hellas, with a diameter of 2300 km and a depth of over 7 km.
Hellas is thought to have formed between 3.8 and 4.1 billion years ago, when a large asteroid hit the surface of Mars. Since its formation, Hellas has been subject to modification by the action of wind, ice, water and volcanic activity.
Impact craters have also since pock-marked this vast basin floor, two of which are the focus of this image, taken by the High Resolution Stereo Camera on ESA?s Mars Express on 17 December 2013.
The ground resolution is about 15 metres per pixel.
These craters lie in the deepest, western portion of Hellas, and such a clear view is unusual because dust clouds typically obscure the basin floor.
Indeed, this region seems to be covered by a thick blanket of dust.”
July 21 2014, ESA News, France
“Even to the naked eye, our Moon looks heavily cratered. The snippet of carved and pitted lunar surface shown in this image lies within a 66 km-wide crater known as Zucchius.
From our perspective, Zucchius is located on the edge of the southwest limb of the Moon.
The crater?s uneven and messy appearance is a result of how it formed. Lunar craters like Zucchius were created when rocky bodies, such as, meteors and asteroids, collided with the Moon at speeds of tens of kilometres per second, smashing holes into its surface.
More forceful impacts caused material to spring back upwards, a bit like a water droplet hitting a body of water.
This process formed a peak in the centre of the impact crater, as shown here by the cluster of bobbly mounds.”
August 2014, Geology Magazine, USA
“Here we make the first quantitative estimates of the maximum total number of large terrestrial impact craters that can survive until the current era on Earth.
Our estimates of crater survival are made using the age of Earth?s crust and the expected flux of large extraterrestrial bodies striking Earth.
This analysis neglects effects such as weathering and burial, which tend to preferentially erase smaller craters. Thus, our results represent the maximum number of craters we expect to exist on Earth today.
Although the constant recycling of crustal material creates a strong bias toward younger ages, our model suggests that the terrestrial cratering record can be used to determine the size frequency distribution of the impactors that bombarded Earth over the past 3.5 G.y.”
[Read the full abstract]
July 10 2014, ESA News, France
“The surface of Mars is pocked and scarred with giant impact craters and rocky ridges, as shown in this new image from ESA?s Mars Express that borders the giant Hellas basin in the planet?s southern hemisphere.
The Hellas basin, some 2300 km across, is the largest visible impact structure in the Solar System, covering the equivalent of just under half the land area of Brazil.
The images presented here were taken on 13 January 2014 by the high-resolution stereo camera on Mars Express and feature a portion of the western rim of the Hellas basin, which slopes into the foreground.
This view highlights the Hellespontus Montes, a rough chain of mountain-like terrain that runs around the rim of the basin, seen here as an uneven ridge curving across the top of the main colour, topography and 3D images, and extending to the right in the perspective view. “
May 26 2014, ESA News, France
“The dark and shadowed regions of the Moon fascinate astronomers and Pink Floyd fans alike.
Our Moon?s rotation axis has a tilt of 1.5º, meaning that some parts of its polar regions never see sunlight ? the bottoms of certain craters, for example, are always in shadow.
Imaged during summertime in the Moon?s southern hemisphere by the Advanced Moon Imaging Experiment on ESA?s SMART-1 spacecraft, this mosaic shows a crater-riddled region spanning the lunar south pole.
It is made up of around 40 individual images taken between December 2005 and March 2006, and covers an area of about 500 x 150 km.
The craters visible here include (from right to left, starting with the largest round shape visible in the frame) the Amundsen, Faustini, Shoemaker, Shackleton and de Gerlache craters.”
February 10 2014, ESA News, France
“Large and small, hundreds of thousands of craters scar the surface of Mars, hollowed out by a multitude of asteroids and comets that impacted the Red Planet throughout its history.
The image in this story shows a region of the planet?s northern hemisphere known as Hephaestus Fossae ? after the Greek god of fire ? that was imaged by the high-resolution stereo camera on ESA?s Mars Express orbiter on 28 December 2007.
The image has been coloured to indicate the elevation of the terrain: green and yellow shades represent shallow ground, while blue and purple stand for deep depressions, down to about 4 km.
Scattered across the scene are a few dozen impact craters that cover a wide range of sizes, with the largest boasting a diameter of around 20 km.
The long and intricate canyon-like features that resemble riverbeds are the phenomenal aftermath of the same fierce impacts that created the largest craters.”
[Full Story page with images]
January 02 2014, Sky & Telescope, USA
“Discovered on New Year’s Eve by a telescope in Arizona, a small asteroid struck Earth somewhere over the Atlantic Ocean – apparently unnoticed – about 25 hours later.
It was New Year’s Eve, but that didn’t stop observer Richard Kowalski from scanning the sky for near-Earth objects (NEOs).
He hadn’t been using the 60-inch telescope on Arizona’s Mount Lemmon for long when he noticed a 19th-magnitude blip skimming through northern Orion in a seven-image series begun at 5:16 p.m. (01:16 Universal Time on January 1st).
But at the time neither Kowalski nor anyone else realized that the little intruder was only 300,000 miles (500,000 km) from Earth and closing fast.
As announced by the MPC earlier today, it’s ‘virtually certain’ that 2014 AA hit Earth. According to calculations by dynamicist Stephen Chesley (Jet Propulsion Laboratory), the impact occurred over the Atlantic Ocean somewhere between Central America to East Africa.
Chesley’s ‘best-fit’ collision is just off the coast of West Africa at roughly 2:30 Universal Time this morning.”
[Full Story]
December 17, 2013, NASA LROC, Lunar Orbit
“The NASA Lunar Impact Monitoring Program monitors the Moon from a dedicated telescope facility at Marshal Space Flight Center for Meteoroid Impacts.
Since 2005 the Marshall group recorded over 300 flashes(assumed to be meteoroid impacts), their brightest recorded flash occurred on 17 March 2013 with coordinates 20.6°N, 336.1°E.
Since then LRO passed over the flash site and the NAC imaged the surrounding area; a new 18 meter (59 feet) diameter crater was found by comparing images taken before and after the March date.” [Before & After Animated Images]
December 09, 2013, NASA Earth Observatory, Earth Orbit
“The Aorounga impact structure in northern Chad is 12.6 kilometers (7.8 miles) in diameter, large enough to display a central peak and more than one concentric ring.
This eroded remnant of a crater (top photo) in Africa’s Sahara Desert is estimated to be less than 345 million years old.
Astronauts have photographed it several times over the years, most recently in 2009 and in 2011.
But it’s not the crater itself that caught our eyes this time. It is the sandy landscape around it.
The middle and lower images [on the NASA website] feature a series of horn-shaped ‘barchan’ dunes clustered in a narrow corridor between lines of dark-toned hills.
This peak is surrounded by a low, sand-filled ring, which is surrounded by another ring of rock from when the material was thrown outwards.” [Full Story]
November 29, 2013, ESA Space in Images, Earth Orbit
“The image from Japan?s ALOS satellite shows the Aorounga Crater in northern Chad.
The crater is just south of the Tibesti Mountains, a range of inactive ? with some potentially active ? volcanoes in the central Sahara desert.
Measuring about 12 km across, the crater was created by a meteorite impact about 340 million years ago.
Clearly visible is the dark, central peak, caused by material splashing up after the impact, similar to how water bounces back up when a stone is thrown in.
This peak is surrounded by a low, sand-filled ring, which is surrounded by another ring of rock from when the material was thrown outwards.” [Full Story]
September 04, 2013, ESA Mars Express News, Mars Orbit
“Becquerel Crater is named for the 19th-century French physicist Antoine Henri Becquerel (1852?1908), winner of the Nobel Prize in physics in 1903 along with Marie and Pierre Curie for the discovery of radioactivity.
It is the largest crater in this scene, with a diameter of 167 km, and drops to a depth of about 3.5 km below the surrounding terrain.
A second large crater lies within Becquerel, punching even deeper into the surface, as seen in the Mars Express topography and 3D images.
This perspective view reveals an intriguing, large mound within Becquerel?s crater walls, reminiscent of Mount Sharp in Gale crater, currently being explored by NASA?s Curiosity rover.
The mound rises about 1 km above the crater floor and comprises hundreds of layers of light-toned sediments, each just a few metres thick, made of sulphate-bearing rocks.
On Earth, sulphates are most often formed via the evaporation of water, so the presence of these minerals in Becquerel crater suggests that water may once have pooled here in a vast crater lake, before evaporating away.
It is likely that the entire crater floor was once covered with such sediments, but over billions of years much of it has been eroded away by wind, leaving just a polished, rounded mound behind.”
March 04, 2013, ISS, Earth Orbit
“The whole world took notice of meteor impacts after the spectacular event over Russia?s Ural Mountains on February 15, 2013.
While the Chelyabinsk meteor exploded while entering the atmosphere, impact craters document the locations where meteors survive the transit through the atmosphere to crash onto the surface.
While some meteor impact locations are readily recognizable from orbit as distinct circular structures?such as Barringer Crater in Arizona?most are harder to recognize because erosion, tectonic alteration of the landscape, or human land use obscure the features.
In cases where only the eroded remnants of a potential impact crater have been recognized, the terms ‘impact structure’ or ‘astrobleme’ are used.
Such is the case for the Piccaninny Impact Structure, located in northern Western Australia and featured in this astronaut photograph.
This is the first confirmed image of the impact structure taken from the International Space Station (ISS).
The Piccaninny structure is located within the semi-arid Purnululu National Park and World Heritage Site, and is thought to have been formed less than 360 million years ago.” [Full Story]
[ A good high resolution image of this newly discovered crater in NW Australia can be accessed HERE
– JM. ]
“Russia?s Urals region has been rocked by a meteorite explosion in the stratosphere. The impact wave damaged several buildings, and blew out thousands of windows amid frigid winter weather. Hundreds are seeking medical attention for minor injuries, [TV channel Russia Today (RT.com) has reported].
Around 950 people have sought medical attention in Chelyabinsk alone because of the disaster, the region’s governor Mikhail Yurevich told RIA Novosti. Over 110 of them have been hospitalized and two of them are in heavy condition. Among the injured there are 159 children, Emergency ministry reported.
Army units found three meteorite debris impact sites, two of which are in an area near Chebarkul Lake, west of Chelyabinsk. The third site was found some 80 kilometers further to the northwest, near the town of Zlatoust. One of the fragments that struck near Chebarkul left a crater six meters in diameter.”
Several video clips of the actual explosion taken by eyewitnesses
[Later this evening, February 15 2013,
Asteroid 2012 DA14, with an estimated diameter of 65 metres, is due to fly past Earth with a staggeringly small miss distance of less than one tenth of the distance between Earth and the Moon.
Numerous pieces of debris from the fragmented meteorite that exploded over the Urals in Russia this morning have been found in the area of Chebarkul Lake, west of Chelyabinsk, where a large hole in the ice suspected to have been made by meteorite debris was discovered by a fisherman after the explosion. Another impact site has now been discovered 80 kilometers northwest of Chelyabinsk near the town of Zlatoust.
There is much speculation already that both these events may be related, but NASA’ SpaceWeather website has issued the following statement:
“The trajectory of the Russian meteorite was significantly different than the trajectory of the asteroid 2012 DA14, making it a completely unrelated object. Information is still being collected about the Russian meteorite and analysis is preliminary at this point. In videos of the meteor, it is seen to pass from left to right in front of the rising sun, which means it was traveling from north to south. Asteroid DA14’s trajectory is in the opposite direction, from south to north.”
Naturally, panic and scare stories have spread in the wake of the event, and the web is full of nonsense from the start of World War 3 to Alien Invasion. Hopefully this will end speculation that the two events are related – they are not.
NASA ScienceCast
Record-setting Asteroid Flyby on February 15th 2013
RUSSIAN ASTEROID IMPACT UPDATE February 18 2013: It is now known that some 1200 people were injured as a result of what NASA says was an asteroid: ‘about 17 meters in diameter and weighed approximately 10,000 metric tons’.
Quoting Bill Cooke, head of NASA’s Meteoroid Environment Office, NASA also says: ‘It struck Earth’s atmosphere at 40,000 mph (18 km/s) and broke apart about 12 to 15 miles (20 to 25 km) above Earth’s surface. The energy of the resulting explosion was in the vicinity of 500 kilotons of TNT. A shock wave propagated down and struck the city below, causing large numbers of windows to break, some walls to collapse, and minor damage throughout the city. When you hear about injuries, those are undoubtedly due to the effects of the shock wave, not due to fragments striking the ground. There are undoubtedly fragments on the ground, but as of this time we know of no recovered fragments that we can verify.’ .
This impact has been described as ‘the most energetic recorded meteor strike since the Tunguska impact of 1908’, and there are a number of Russian websites which show a compilation of the many videos of the event taken by ordinary folk on mobile phones and other devices. These vary in quality as a result of this and may take a while to download depending on your connection speed, though it is worth the wait in my opinion – Ed.]
January 21, 2013, ABC Science News, Australia
“A US spacecraft orbiting Mars has provided evidence of an ancient crater lake fed by groundwater, adding further support to theories that the Red Planet may once have hosted life.
Spectrometer data from NASA’s Mars Reconnaissance Orbiter (MRO) shows traces of carbonate and clay minerals usually formed in the presence of water at the bottom of the 2.2 kilometre deep McLaughlin Crater.
‘These new observations suggest the formation of the carbonates and clay in a groundwater-fed lake within the closed basin of the crater,’ write NASA scientists in a paper published in the online edition of Nature Geoscience.
The crater lacks large inflow channels, so the lake was likely fed by groundwater, the scientists write.” [Full Story]
October 18, 2012, SpaceWeather.com / SETI, USA
“A small asteroid that exploded over the San Francisco Bay Area on Oct. 17th, shaking houses with its sonic boom, might have scattered pieces of itself on the ground.
That’s the conclusion of Peter Jenniskens of the NASA Ames Research Center. He triangulated data from a pair of meteor surveillance cameras to determine the fireball’s trajectory.
‘The asteroid entered at a [relatively slow] speed of 14 km/s. There’s a good chance that a fairly large fraction of this rock survived and fell somewhere around the North Bay’, says Jenniskens.
‘Much more accurate results will follow from a comprehensive study of the video records. Now, we hope that someone recovers a meteorite on the ground.’
The disintegrating asteroid continued beyond the tip of the arrow for a possible landfall somewhere north of San Francisco.” [Full Story]
[Stay tuned for updates on the meteorite hunt – Ed.]
September 06, 2012, ESA News, France
“Recently engaged in providing support to the successful landing of NASA?s Mars Science Laboratory’s Curiosity rover, ESA?s Mars Express has now returned to its primary mission of studying the diverse geology and atmosphere of the ‘Red Planet’ from orbit.
Earlier this year, the spacecraft observed the 120 km wide Hadley Crater, providing a tantalising insight into the martian crust.
The images show multiple subsequent impacts within the main crater wall, reaching depths of up to 2600 m below the surrounding surface.
This region imaged on 9 April 2012 by the High Resolution Stereo Camera on Mars Express shows the crater which lies to the west of the Al-Qahira Vallis in the transition zone between the old southern highlands and the younger northern lowlands.
The images show that Hadley Crater was struck multiple times by large asteroids and/or comets after its initial formation and subsequent infilling with lava and sediments. “ [Full Story]
[An excellent series of High Definition images – Ed.]
August 02, 2012, ESA News, France
“ESA?s Mars Express has observed the southern part of a partially buried approx. 440-km wide crater, informally named Ladon basin.
The images, near to where Ladon Valles enters this large impact region reveal a variety of features, most notably the double interconnected impact craters Sigli and Shambe, the basins of which are criss-crossed by extensive fracturing.
This region, imaged on 27 April by the high-resolution stereo camera on Mars Express is of great interest to scientists since it shows significant signs of ancient lakes and rivers.
Both Holden and Eberswalde Craters were on the final shortlist of four candidate landing sites for NASA?s Mars Science Laboratory, which is due now to land in Gale Crater on 6 August.
Large-scale overview maps show clear evidence that vast volumes of water once flowed from the southern highlands. This water carved Ladon Valles, eventually flowing into Ladon basin, an ancient large impact region.” [Full Story]
June 24, 2012, NASA Earth Observatory, Earth Orbit
“Impact craters can be tough to detect from the ground, especially if they are situated in remote locations and covered by vegetation.
Both factors hampered understanding of the Luizi Structure, located in southeastern Congo.
The crater is covered by grasses up to a meter (3 feet) high, and tucked away in central Africa.” [Full Story]
May 07, 2012, NASA Earth Observatory, Earth Orbit
“The Ouarkziz Impact Crater is located in northwestern Algeria, close to the border with Morocco.
The crater was formed by a meteor impact less than 70 million years ago, during the late Cretaceous Period of the Mesozoic Era, or ‘Age of Dinosaurs.’
Originally called Tindouf, the 3.5-kilometer wide crater (image center) has been heavily eroded since its formation; however, its circular morphology is highlighted by exposures of older sedimentary rock layers that form roughly northwest to southeast-trending ridgelines.
From the vantage point of an astronaut on the International Space Station, the impact crater is clearly visible with a magnifying camera lens.” [Full Story]
April 23, 2012, ABC Science News, Australia
“Scientists studying life deep below an asteroid impact crater in the United States have found tiny organisms thriving kilometres under the surface.
The work, reported in the journal Astrobiology suggests impact craters may be a good place to look for life on other planets.
Despite a large fraction of Earth’s bio-mass being on or below the surface, the new study is the first to examine how asteroid impacts affect sub-surface ecosystems.
Scientists including Professor Charles Cockell, from the University of Edinburgh, examined drill samples taken from deep below the Chesapeake Bay impact crater in Virginia, United States.
Cockell and colleagues studied cores taken from as far as 1.76 kilometres below the 90 kilometre-wide structure.” [Full Story]
February 09, 2012, Discovery News, USA
“Britain’s largest space rock – excavated 200 years ago by an archaeological dig – was preserved by the Ice Age.
With a weight that rivals a baby elephant, a meteorite that fell from space some 30,000 years ago is likely Britain’s largest space rock.
And after much sleuthing, researchers think they know where it came from and how it survived so long without weathering away.
The giant rock, spanning about 1.6 feet (0.5 meters) across and weighing 205 pounds (93 kilograms), was likely discovered by an archaeologist about 200 years ago at a burial site created by the Druids (an ancient Celtic priesthood) near Stonehenge, according to said Colin Pillinger, a professor of planetary sciences at the Open University.
Pillinger curated the exhibition “Objects in Space,” which opened Feb. 9 and is the first time the public will get a chance to see the meteorite. The exhibition will explore not only the mystery that surrounds the origins of the giant meteorite, but also the history and our fascination with space rocks.
‘Britain was under an ice age for 20,000 years’, Pillinger told LiveScience, explaining the climate would have protected the rock from weathering.” [Full Story]
Terrestrial & Solar System
Impacts and Impact Craters
Below are some images of the larger known asteroids
Asteroid Eros
NEAR, JHU APL, NASA
“Several spacecraft have orbited or landed on asteroids and sent pictures of these bodies back to Earth. The NEAR Shoemaker mission, launched in 1996, was the first spacecraft to land on an asteroid, touching down on Eros on February 12, 2001.”
Asteroid 253 Mathilde
NEAR, JHU APL, NASA
On June 27, the NEAR (for Near Earth Asteroid Rendezvous) spacecraft, traveling some 36,000 kilometers per hour, streaked past an asteroid named Mathilde far beyond the orbit of Mars. It was just a brief encounter along a long journey to a different asteroid, Eros.
“Liquid water, carbon-based molecules and a relatively stable environment are critical elements for life. Comets and asteroids can bring water and the chemicals on which life is based, but can also bring widespread destruction. If future impacts are inevitable, what should we do?”
Books About Asteroids,
Comets, Meteor Storms,
Impact Craters & Ancient Cosmic Catastrophes
“The 2300 BC Event takes a new look at an old puzzle: what happened at this date to cause the advanced societies on the Earth to simultaneously collapse?
Civilizations in Anatolia and Greece, through Egypt and the Middle East, and eastward to India and Central Asia were at their height. The collapse of these civilizations due to earthquakes and climatic changes has been mirrored by similar interruptions on all continents, in the Arctic, and extending into the Pacific.
The discontinuities have long puzzled archaeologists and historians. New religions and accompanying mythologies appeared at this time in all cultural regions describing bombardment and flooding from the skies.
Strangely, the dominant aspect of the mythologies, however, is the observation and worship of a ring appearing to surround the Earth, oriented to the two Ursa (Bear) constellations.”
“Some time around 2300 BC the Eath encountered a dense clustering of space debris, the early Southern & Northern Taurid meteoroid stream. The result was an intense fall of meteoroids, some of them sufficiently large to cause surface destruction.
Simultaneous with the meteoroid fall was a huge downpouring of water which caused flash flooding. Extensive destruction and loss of life resulted. An astonishing aspect of the event was the formation of a ring surrounding the Earth, reflecting sunlight during the day, hiding some stars at night, and moving around the sky through a 24-hour period.
Following the ‘main event’, there were crustal movements which shifted the location of water sources, and caused earthquakes which destroyed settlements. Abrupt severe climate changes occurred.”
“The Northern/Southern Taurid meteoroid stream is identified as the specific meteoroid stream that the Earth encountered at 2300 BC.
The Earth’s encounter with a dense cluster of large objects would produce atmospheric phenomena very different from the pleasant and interesting night displays of meteor trails that are within our own experience.
The rain of objects would have generated extraordinary visual and auditory effects combined with ground vibrations; and under extreme conditions would bring about severe surface destruction and loss of life.
The overall event was associated by the people with powerful deities and formed the basis for major religions. The mythologies and traditions are, in large part, the residues of those religions.”
Research in the field of neo-catastrophism and impact cratering has quickened its pace since the early 1980s. Scholars such as Victor Clube, Bill Napier, Mark Bailey, Sir Fred Hoyle and Duncan Steel claim that a more ‘active’ sky might have caused major cultural changes of Bronze Age civilizations, belief systems and religious rituals.”
“Around 700 BC an Assyrian scribe in the Royal Place at Nineveh made a copy of one of the most important documents in the royal collection. Two and a half thousand years later it was found by Henry Layard in the remains of the palace library. It ended up in the British Museum’s cuneiform clay tablet collection as catalogue No. K8538 (also called “the Planisphere”), where it has puzzled scholars for over a hundred and fifty years. In this monograph Bond and Hempsell provide the first comprehensive translation of the tablet, showing it to be a contemporary Sumerian observation of an Aten asteroid over a kilometre in diameter that impacted Kofels in Austria in the early morning of 29th June 3123 BC.”
“This volume synthesizes 16 years of geological and geophysical studies which document an 85-km-wide impact crater buried 500 m beneath Chesapeake Bay in south eastern Virginia, USA. The authors integrate extensive seismic reflection profiling and deep core drilling to analyze the structure, morphology, gravimetrics, sedimentology, petrology, geochemistry, and paleontology of this submarine structure. Of special interest are a detailed comparison with other terrestrial and extraterrestrial craters, as well as a conceptual model and computer simulation of the impact. The extensive illustrations encompass more than 150 line drawings and core photographs. An accompanying CD-ROM includes selected seismic profiles, scaled cross sections, detailed maps, and downhole geophysical logs.”
“Describes a search for geological evidence of meteorite impact structures in Britain. The statistics of impact structures indicate that Britain should have Phanerozoic impact structures up to tens of kilometres in diameter. A constant theme is the importance of atmospheric break-up of small asteroids and comets. These fragmenting bodies produce anomalously shallow craters with low rims and central peaks; three British structures of this type are identified. Analysis of fireball statistics implies that damaging fireball explosions occur over the British Isles on a time-scale of decades. On a time-scale of millennia, however, more damage is done by Atlantic impact tsunami.”
“Mackenzie prefaces his absorbing account of the new “giant impact” theory of the moon’s origin with the fascinating story of humanity’s long relationship with Earth’s only natural satellite. Evidence of that relationship begins with what is very probably a lunar calendar among the famous Lascaux cave paintings, and continues in early civilizations’ timekeeping uses of the moon and classical Greek ideas about the moon’s composition. In the fifth century B.C.E., Anaxagoras correctly realized that the moon was made of rock. Later, Aristotle didn’t agree, and his view held sway for centuries.”
“This volume is the 8th in a series of impact books resulting from the activities of the scientific program “Response of the Earth System to Impact Processes” (IMPACT), by the European Science Foundation. The book resulted from an international meeting at Mora, Sweden, which was held as part of the IMPACT program. The papers cover various structural geologic, geochemical, and geophysical topics on research of asteroid impact structures on Earth and Mars.”
“In recent years, meteorites have caught the imagination of scientist and collector alike. An army of people are now actively searching for them in the hot and cold deserts of Earth. Fascinating extraterrestrial rocks in meteorites are our only contact with materials from beyond the Earth-Moon system.”
“The Celtic myths, involving heroic warriors such as Finn and CuChulinn, can be read as simple primitive stories, but closer examination reveals strange descriptions and relationships.
The authors of this ground-breaking book argue that all the principal characters are aspects of the one Celtic sky god, Lugh, who was a comet. Against the background of a comet scenario this re-interpretation of about ten key Celtic myths shows how many of the descriptions in the myths fit the appearance of comets.
The fact that these comets on occasions produced abrupt environmental changes, that can be traced in the tree-ring and ice-core chronologies, pins the stories to a central reality. With a novel twist this original book confirms the widespread belief that these stories must contain ‘a core of truth’.”
“Could both Stonehenge and the pyramids of Egypt have been constructed to observe and commemorate a period of phenomenal meteor storms and asteroid detonations produced by a burst of activity in the Taurid Complex 4,500 to 5,000 years ago? Author Duncan Steel examines the evidence indicating rogue asteroids and doomsday comets may have been behind these and other ancient phenomena.”
“The End of the Dinosaurs gives a detailed account of the great mass extinction that rocked the Earth 65 million years ago, and focuses on the discovery of the culprit: the Chicxulub impact crater in Mexico. It recounts the birth of the cosmic hypothesis, the controversy that preceded its acceptance, the search for the crater, its discovery and ongoing exploration, and the effect of the giant impact on the biosphere. Other mass extinctions in the fossil record are reviewed, as is the threat of asteroids and comets to our planet today. The account of the impact and its aftermath is suitable for general readers. The description of the crater geology is in enough detail to interest students of the earth sciences. A detailed index and bibliography are included.”
“During its five billion year history, Earth has been hit countless times by asteroids and meteorites. Over 150 crater-producing events have been identified, and this book describes all 139 sites worldwide at which evidence of the impacts can be seen. They range in age from recent craters formed this century to the highly eroded billion-year old ancient craters. Some are spectacular to visit, such as the Barringer Crater in Arizona, the ring-shaped mountains of Gosses Bluff, Australia, and the huge crater at Ries in Germany.
For each site there is a summary table giving location, size, age and present condition. Maps are included where necessary. The author has visited many of the sites and his photographs enrich this thorough survey. Meteorite craters are fascinating to visit, so the descriptions include guidance about access and suggested itineraries for the large structures.”
“On the morning of June 30, 1908, a fireball cascaded down the Siberian sky and exploded with 2000 times the force of the nuclear blast that devastated Hiroshima, Japan. Weighing some 100,000 metric tons, the cosmic missile cut into the atmosphere and shattered in a rapid series of bursts, felling trees and incinerating an area of 2150 square miles – now known as the Tunguska ‘event’.
In the spring of 1992, Roy Gallant was invited by the Siberian branch of the National Academy of Sciences to take part in the annual Tunguska Expedition, to investigate this largest meteorite explosion in human history.”
“In the early years of the twentieth century, an enormous bowl-shaped hole in the high plains of northern Arizona was investigated by a mining engineer and his associates. The hole was almost three quarters of a mile wide-a little over one kilometer¹-and it penetrated thick layers of subsurface rock.
The investigators concluded that it was created thousands of years ago when a mass of meteoritic iron struck the earth, and they produced extensive evidence in support of their claim.”
“Norton (astronomy, Central Oregon Community College) tells the story of meteorites and our attempts to read their history. Topics include the development of the interdisciplinary science of meteoritics, asteroids, current classifications of meteorites, and the impact of the comet Shoemaker-Levy on Jupiter in 1994.
“A straightforward, thorough look at all aspects of meteors and meteorites, including how and where meteors originate, when and where to watch for them, and how to classify, collect, and preserve meteorites. Meteor showers, interesting meteorite craters, and tektites are all discussed in detail. Also contains a comprehensive listing of meteorite organisations, dealers, museums, and references.”
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