A NASA Hubble Space Telescope mosaic image of a small portion of the Orion Nebula, taken the Wide Field and Planetary Camera (in wide field mode).
Hubble shows a wealth of detail never seen before in the nebula. New features include: elongated objects oriented on the brightest stars in this region (which are located just off the edge of the picture); rapidly expanding plumes of material around young stars; and protoplanetary disks.
This color photograph is a composite of separate images taken at the wavelengths of three abundant elements in the nebula: Hydrogen, Oxygen and Nitrogen. The images were taken August 13 and 14, 1991.
The image is 1.29 light-years across.
Image Credit: C.R. O'Dell (Rice University), and NASA
Explanation from: https://www.spacetelescope.org/images/opo9229a/
Bright pink nebulae almost completely encircle a spiral galaxy in this NASA/ESA Hubble Space Telescope image of NGC 922. The ring structure and the galaxy’s distorted spiral shape result from a smaller galaxy scoring a cosmic bullseye, hitting the centre of NGC 922 some 330 million years ago.
In Hubble’s image, NGC 922 clearly reveals itself not to be a normal spiral galaxy. The spiral arms are disrupted, a stream of stars extends out towards the top of the image, and a bright ring of nebulae encircles the core. Observing with NASA’s Chandra X-ray Observatory reveals more chaos in the form of ultraluminous X-ray sources dotted around the galaxy.
NGC 922’s current unusual form is a result of a cosmic bullseye millions of years ago. A smaller galaxy, catalogued as 2MASXI J0224301-244443, plunged right through the heart of NGC 922 and shot out the other side. In wide-field views of the NGC 922, the small interloper can be still be seen shooting away from the scene of the crash.
As the small galaxy passed through the middle of NGC 922, it set up ripples that disrupted the clouds of gas, and triggered the formation of new stars whose radiation then lit up the remaining gas. The bright pink colour of the resulting nebulae is a characteristic sign of this process, and it is caused by excited hydrogen gas (the dominant element in interstellar gas clouds). This process of excitation and emission of light by gases is similar to that in neon signs.
In theory, if two galaxies are aligned just right, with the small one passing through the centre of the larger one, the ring of nebulae should form a perfect circle, but more often the two galaxies are slightly off kilter, leading to a circle that, like this one, is noticeably brighter on one side than the other.
These objects, called collisional ring galaxies, are relatively rare in our cosmic neighbourhood. Although galaxy collisions and mergers are commonplace, the precise alignment and ratio of sizes necessary to form a ring like this is not, and the ring-like phenomenon is also thought to be relatively short-lived.
The chances of seeing one of these galaxies nearby is therefore quite low. Despite the immense number of galaxies in the Universe, this is one of only a handful known in our cosmic neighbourhood. Observations of the more distant Universe (where we see further into the past) show that these rings were more common in the past, however.
Hubble’s image of NGC 922 consists of a series of exposures taken in visible light with Hubble’s Wide Field Camera 3, and in visible and near-infrared light with the Wide Field and Planetary Camera 2.
Image Credit: NASA, ESA
Explanation from: https://www.spacetelescope.org/news/heic1218/
The dancing lights of the aurora provide spectacular views on the ground, but also capture the imagination of scientists who study incoming energy and particles from the Sun. Aurora are one effect of such energetic particles, which can speed out from the sun both in a steady stream called the solar wind and due to giant eruptions known as coronal mass ejections or CMEs.
Saturn's orange moon Titan has hundreds of times more liquid hydrocarbons than all the known oil and natural gas reserves on Earth, according to new data from NASA's Cassini spacecraft. The hydrocarbons rain from the sky, collecting in vast deposits that form lakes and dunes.
The new findings from the study led by Ralph Lorenz, Cassini radar team member from the Johns Hopkins University Applied Physics Laboratory, Laurel, Md., are reported in the Jan. 29 issue of the Geophysical Research Letters.
"Titan is just covered in carbon-bearing material -- it's a giant factory of organic chemicals," said Lorenz. "This vast carbon inventory is an important window into the geology and climate history of Titan."
At a balmy minus 179 degrees Celsius (minus 290 degrees Fahrenheit), Titan is a far cry from Earth. Instead of water, liquid hydrocarbons in the form of methane and ethane are present on the moon's surface, and tholins probably make up its dunes. The term "tholins"was coined by Carl Sagan in 1979 to describe the complex organic molecules at the heart of prebiotic chemistry.
Cassini has mapped about 20 percent of Titan's surface with radar. Several hundred lakes and seas have been observed, with each of several dozen estimated to contain more hydrocarbon liquid than Earth's oil and gas reserves. The dark dunes that run along the equator contain a volume of organics several hundred times larger than Earth's coal reserves.
Proven reserves of natural gas on Earth total 130 billion tons, enough to provide 300 times the amount of energy the entire United States uses annually for residential heating, cooling and lighting. Dozens of Titan's lakes individually have the equivalent of at least this much energy in the form of methane and ethane.
"This global estimate is based mostly on views of the lakes in the northern polar regions. We have assumed the south might be similar, but we really don't yet know how much liquid is there," said Lorenz. Cassini's radar has observed the south polar region only once, and only two small lakes were visible. Future observations of that area are planned during Cassini's proposed extended mission.
Scientists estimated Titan's lake depth by making some general assumptions based on lakes on Earth. They took the average area and depth of lakes on Earth, taking into account the nearby surroundings, like mountains. On Earth, the lake depth is often 10 times less than the height of nearby terrain.
"We also know that some lakes are more than 10 meters or so deep because they appear literally pitch-black to the radar. If they were shallow we'd see the bottom, and we don't," said Lorenz.
The question of how much liquid is on the surface is an important one because methane is a strong greenhouse gas on Titan as well as on Earth, but there is much more of it on Titan. If all the observed liquid on Titan is methane, it would only last a few million years, because as methane escapes into Titan's atmosphere, it breaks down and escapes into space. If the methane were to run out, Titan could become much colder. Scientists believe that methane might be supplied to the atmosphere by venting from the interior in cryovolcanic eruptions. If so, the amount of methane, and the temperature on Titan, may have fluctuated dramatically in Titan's past.
"We are carbon-based life, and understanding how far along the chain of complexity towards life that chemistry can go in an environment like Titan will be important in understanding the origins of life throughout the universe," added Lorenz.
Image Credit: Steven Hobbs (Brisbane, Queensland, Australia
Explanation from: https://www.nasa.gov/mission_pages/cassini/media/cassini-20080213.html
The JunoCam imager on NASA's Juno spacecraft snapped this shot of Jupiter's northern latitudes on December 11, 2016 at 8:47 a.m. PST (11:47 a.m. EST), as the spacecraft performed a close flyby of the gas giant planet. The spacecraft was at an altitude of 10,300 miles (16,600 kilometers) above Jupiter's cloud tops.
This stunning view of the high north temperate latitudes fortuitously shows NN-LRS-1, a giant storm known as a Little Red Spot (lower left). This storm is the third largest anticyclonic reddish oval on the planet, which Earth-based observers have tracked for the last 23 years. An anticyclone is a weather phenomenon with large-scale circulation of winds around a central region of high atmospheric pressure. They rotate clockwise in the northern hemisphere, and counterclockwise in the southern hemisphere.
This Little Red Spot shows very little color, just a pale brown smudge in the center. The color is very similar to the surroundings, making it difficult to see as it blends in with the clouds nearby. Citizen scientists Gerald Eichstaedt and John Rogers processed the image and drafted the caption.
Although the Universe may seem spacious most galaxies are clumped together in groups or clusters and a neighbour is never far away. But this galaxy, known as NGC 6503, has found itself in a lonely position, shown here at the edge of a strangely empty patch of space called the Local Void. This NASA/ESA Hubble Space Telescope image shows a very rich set of colours, adding to the detail seen in previous images.
NGC 6503 is only some 18 million light-years away from us in the constellation of Draco (The Dragon), making it one of the closest neighbours from our Local Group. It spans some 30 000 light-years, about a third of the size of the Milky Way.
This galaxy does not just offer poetic inspiration; it is also the subject of ongoing research. The Hubble Legacy ExtraGalactic UV Survey (LEGUS) is exploring a sample of nearby galaxies, including NGC 6503, to study their shape, internal structure, and the properties and behaviour of their stars. This survey uses 154 orbits of time on Hubble; by contrast, a typical Hubble observing programme lasts from a few to a few tens of orbits.
The Local Void is a patch of space thought to be about 150 million light-years across that seems to be curiously devoid of galaxies. Astronomers using Hubble discovered that the emptiness of this region has quite an effect on the space around us — the Milky Way is being strongly pulled away from it by the gentle but relentless tug of other nearby galaxies.
NGC 6503 lies right on the edge of this void. It has an almost non-existent central bulge surrounded by a massive halo of gas. The galaxy’s central region is a good example of something known as a “low ionisation nuclear emission region”, or LINER. These are less luminous than some of the brightest galaxies. Emission from NGC 6503’s heart is believed to be the result of a starved black hole that is only just being kept active, receiving a very small amount of infalling gas to keep its large appetite at bay.
A previous image of NGC 6503 was released in 2010, taken by Hubble’s Advanced Camera for Surveys. However, this image, taken using Hubble’s Wide Field Camera 3 (WFC3), shows NGC 6503 in striking detail and with a richer set of colours. Bright red patches of gas can be seen scattered through its swirling spiral arms, mixed with bright blue regions that contain newly-forming stars. Dark brown dust lanes snake across the galaxy’s bright arms and centre, giving it a mottled appearance.
Installed in 2009 during the final Hubble servicing mission, SM4, WFC3 covers a wide range of the spectrum, from the ultraviolet all the way through to the near-infrared. Compared with its predecessor, the Wide Field and Planetary Camera 2 (WFPC2), it offers improved resolution and a wider field of view, and has led to a large number of stunning Hubble images since its installation.
Image Credit: NASA, ESA
Explanation from: http://www.spacetelescope.org/images/heic1513a/
The large dark feature is a classic Martian sand dune. Most sand on Earth is made from the mineral quartz, which is white and bright. On Mars, most sand is composed of dark basalt, a volcanic rock. For this reason, dunes on Mars are darker than those on Earth.
The dunes in this observation, within Wirtz Crater, are known as "barchans." The steepest slope is on the eastern (right) side, partially in shadow, and represents the direction the dune is migrating as the sand is blown and transported by the wind. Small ripples are visible on much of the dune surface. The dark streaks on the dune are tracks left by passing vortices known to us as dust devils. These raise dust off the dune, revealing a darker substrate.
Image Credit: NASA/JPL-Caltech/Univ. of Arizona
Explanation from: http://photojournal.jpl.nasa.gov/catalog/PIA12289
An astronaut aboard the International Space Station adjusted the camera for night imaging and captured the green veils and curtains of an aurora that spanned thousands of kilometers over Quebec, Canada.
Snow and ice in this winter image, acquired on February 3, 2012, reflect enough light from stars, the moon, and the aurora to reveal details of the landscape. On the lower right, we see a circle of ice on the frozen reservoir that now occupies Manicouagan impact crater (70 kilometers in diameter). City lights reveal small settlements, such as Labrador City (an iron-ore mining town) and the Royal Canadian Air Force base at Goose Bay on the Labrador Sea.
The aurora borealis (northern lights) is the light that glows when charged particles from the magnetosphere (the magnetic space around Earth) are accelerated by storms from the Sun. The particles collide with atoms in the atmosphere; the green and red colors, for instance, are caused by the release of photons by oxygen atoms.
The fainter arc of light that parallels the horizon is known as airglow. This is another manifestation of the interaction of the Earth’s atmosphere with radiation from the sun.
The atmosphere shields life on Earth from the sun’s harmful radiation. It also causes small asteroids to burn up or catastrophically explode before hitting the ground. Larger asteroids can occasionally penetrate the atmosphere and collide with our rocky planet—with dramatic effects.
Geologists know that a large asteroid slammed into Earth roughly 214 million years ago, creating a crater about 100 kilometers (60 miles) across on the landmass that is now part of Canada. The impact caused a shock wave to radiate across Earth’s surface, followed closely by high-velocity winds. Near the impact point, wind speeds would have exceeded 1000 kilometers (600 miles) per hour. The shock wave and air blast would have severely damaged and killed plants and animals out to distances of approximately 560 kilometers (350 miles)—as far as Goose Bay. After erosion by glaciers and other processes over millions of years, the Manicouagan crater is now about 60 kilometers (37 miles) wide.
Image Credit: NASA
Explanation from: https://www.nasa.gov/image-feature/aurora-and-manicouagan-crater
A layer of dry ice covers the South Polar layered deposits every winter. In the spring, gas created from heating of the dry ice escapes through ruptures in the overlying seasonal ice, entraining material from the ground below. The gas erodes channels in the surface, shown in this image, generally exploiting weaker material.
The ground likely started as polygonal patterned ground (common in water-ice-rich surfaces), and then escaping gas widened the channels. Fans of dark material are bits of the surface carried onto the top of the seasonal ice layer and deposited in a direction determined by local winds.
Image Credit: NASA/JPL-Caltech/Univ. of Arizona
Explanation from: http://photojournal.jpl.nasa.gov/catalog/PIA11706
This NASA/ESA Hubble Space Telescope image shows the galaxy IC 335 in front of a backdrop of distant galaxies. IC 335 is part of a galaxy group containing three other galaxies, and located in the Fornax Galaxy Cluster 60 million light-years away.
As seen in this image, the disc of IC 335 appears edge-on from the vantage point of Earth. This makes it harder for astronomers to classify it, as most of the characteristics of a galaxy’s morphology — the arms of a spiral or the bar across the centre — are only visible on its face. Still, the 45 000 light-year-long galaxy could be classified as an S0 type.
These lenticular galaxies are an intermediate state in galaxy morphological classification schemes between true spiral and elliptical galaxies. They have a thin stellar disc and a bulge, like spiral galaxies, but in contrast to typical spiral galaxies they have used up most of the interstellar medium. Only a few new stars can be created out of the material that is left and the star formation rate is very low. Hence, the population of stars in S0 galaxies consists mainly of aging stars, very similar to the star population in elliptical galaxies.
As S0 galaxies have only ill-defined spiral arms they are easily mistaken for elliptical galaxies if they are seen inclined face-on or edge-on as IC 335 here. And indeed, despite the morphological differences between S0 and elliptical class galaxies, they share a some common characteristics, like typical sizes and spectral features.
Both classes are also early-type galaxies, as they are evolving passively. However, elliptical galaxies may be passively evolving when we observe them, but they had violent interactions with other galaxies in their past. Whereas S0 galaxies are either aging and fading spiral galaxies, which never had any interactions with other galaxies, or they are the aging result of a single merger between two spiral galaxies in the past. The exact nature of these galaxies is still a matter of debate.
Image Credit: ESA/Hubble & NASA
Explanation from: https://www.spacetelescope.org/images/potw1451a/
The Carina Nebula is a large bright nebula that surrounds several clusters of stars. It contains two of the most massive and luminous stars in our Milky Way galaxy, Eta Carinae and HD 93129A. Located 7500 light years away, the nebula itself spans some 260 light years across, about 7 times the size of the Orion Nebula, and is shown in all its glory in this mosaic. It is based on images collected with the 1.5-m Danish telescope at ESO's La Silla Observatory.
Being brighter than one million Suns, Eta Carinae (the brightest star in this image) is the most luminous star known in the Galaxy, and has most likely a mass over 100 times that of the Sun. It is the closest example of a luminous blue variable, the last phase in the life of a very massive star before it explodes in a fiery supernova. Eta Carinae is surrounded by an expanding bipolar cloud of dust and gas known as the Homunculus ('little man' in Latin), which astronomers believe was expelled from the star during a great outburst seen in 1843.
Image Credit: ESO/IDA/Danish 1.5 m/R.Gendler, J-E. Ovaldsen, C. Thöne, and C. Feron
Explanation from: https://www.eso.org/public/images/etamosaicnm2/
Image of the Earth acquired with the OSIRIS narrow-angle camera from a distance of 633 000 km on 12 November 2009 at 13:28 CET.
The resolution is 12 km/pixel. The image is part of a sequence of images taken every hour through one full rotation (24 hours).
Three images with an orange, green, and blue filter were combined to create this one. The illuminated crescent is centered roughly around the South Pole (South at the bottom of the image). The outline of Antarctica is visible under the clouds that form the striking south-polar vortex. Pack ice in front of the coastline with its strong spectacular reflection is the cause for the very bright spots on the image.
Image Credit: ESA/OSIRIS Team
Explanation from: http://www.esa.int/spaceinimages/Images/2009/11/First_view_as_Rosetta_approaches_home
The large annular lake in this image represents the remnants of one of the largest impact craters still preserved on the surface of the Earth. Lake Manicouagan in northern Quebec, Canada, surrounds the central uplift of the impact structure, which is about 70 kilometers in diameter and is composed of impact-brecciated (relativley large pieces of rock embedded in finer grained material) rock. Glaciation and other erosional processes have reduced the extent of the crater, with the original diameter estimated at about 100 kilometers. This natural-color image of the region was acquired by the Multi-angle Imaging Spectroradiometer’s (MISR’s) nadir (vertical-viewing) camera on June 1, 2001.
The impact that formed Manicouagan is thought to have occurred about 212 million years ago, toward the end of the Triassic period. Some scientists believe that this impact may have been responsible for a mass extinction associated with the loss of roughly 60% of all species. It has been proposed that the impact was created by an asteroid with a diameter of about 5 kilometers. The lake is bounded by erosion-resistant metamorphic and igneous rocks, and shock metamorphic effects are abundant in the target rocks of the crater floor. Today Lake Manicouagan serves as a reservoir and is one of Quebec’s most important regions for Atlantic salmon fishing.
Image Credit: NASA/GSFC/LaRC/JPL, MISR Team
Explanation from: http://earthobservatory.nasa.gov/IOTD/view.php?id=1993
The release of the first images today from NOAA’s newest satellite, GOES-16, is the latest step in a new age of weather satellites. This composite color full-disk visible image is from 1:07 p.m. EDT on January 15, 2017, and was created using several of the 16 spectral channels available on the GOES-16 Advanced Baseline Imager (ABI) instrument. The image shows North and South America and the surrounding oceans. GOES-16 observes Earth from an equatorial view approximately 22,300 miles high, creating full disk images like these, extending from the coast of West Africa, to Guam, and everything in between.
GOES-16, formerly known as GOES-R, is the first spacecraft in a new series of NASA-built advanced geostationary weather satellites. NASA successfully launched the satellite at 6:42 p.m. EST on November 19, 2016, from Cape Canaveral Air Force Station in Florida. NOAA manages the GOES-R Series Program through an integrated NOAA-NASA office. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, oversees the acquisition of the GOES-R series spacecraft and instruments.
The lesser-known constellation of Canes Venatici (The Hunting Dogs), is home to a variety of deep-sky objects — including this beautiful galaxy, known as NGC 4861. Astronomers are still debating on how to classify it: While its physical properties — such as mass, size and rotational velocity — indicate it to be a spiral galaxy, its appearance looks more like a comet with its dense, luminous “head” and dimmer “tail” trailing behind. Features more fitting with a dwarf irregular galaxy.
Although small and messy, galaxies like NGC 4861 provide astronomers with interesting opportunities for study. Small galaxies have lower gravitational potentials, which simply means that it takes less energy to move stuff about inside them than it does in other galaxies. As a result, moving in, around, and through such a tiny galaxy is quite easy to do, making them far more likely to be suffused with streams and outflows of speedy charged particles known as galactic winds, which can flood such galaxies with little effort.
These galactic winds can be powered by the ongoing process of star formation, which involves huge amounts of energy. New stars are springing into life within the bright, colourful ‘head’ of NGC 4861 and ejecting streams of high-speed particles as they do so, which flood outwards to join the wider galactic wind. While NGC 4861 would be a perfect candidate to study such winds, recent studies did not find any galactic winds in it.
Image Credit: ESA/Hubble & NASA
Explanation from: https://www.spacetelescope.org/images/potw1704a/
Tethys, one of Saturn's larger icy moons, vaguely resembles an eyeball staring off into space in this view from NASA's Cassini spacecraft. The resemblance is due to the enormous crater, Odysseus, and its complex of central peaks.
Like any solar system moon, Tethys (660 miles or 1,062 kilometers across) has suffered many impacts. These impacts are a prime shaper of the appearance of a moon's surface , especially when the moon has no active geological processes. In this case, a large impact not only created a crater known as Odysseus, but the rebound of the impact caused the mountainous peaks, named Scheria Montes, to form in the center of the crater.
This view looks toward the leading side of Tethys. North on Tethys is up and rotated 1 degree to the left. The image was taken in green light with the Cassini spacecraft narrow-angle camera on November 10, 2016.
The view was acquired at a distance of approximately 228,000 miles (367,000 kilometers) from Tethys. Image scale is 1.2 miles (2 kilometers) per pixel.
Image Credit: NASA/JPL-Caltech/Space Science Institute
Explanation from: http://photojournal.jpl.nasa.gov/catalog/PIA20518
This image, taken with the NASA/ESA Hubble Space Telescope, reveals startling new details of one of the most unusual nebulae known in our Galaxy. Catalogued as HD 44179, this nebula is more commonly called the "Red Rectangle" because of its unique shape and colour as seen with ground-based telescopes.
Hubble has revealed a wealth of new features in the Red Rectangle that cannot be seen by ground-based telescopes looking through the Earth's turbulent atmosphere.
A new study unveils NGC 604, the largest region of star formation in the nearby galaxy M33, in its first deep, high-resolution view in X-rays. This composite image from Chandra X-ray Observatory data (colored blue), combined with optical light data from the Hubble Space Telescope (red and green), shows a divided neighborhood where some 200 hot, young, massive stars reside.
Throughout the cosmic metropolis, giant bubbles in the cool dust and warm gas are filled with diffuse, multi-million degree gas that emits X-rays. Scientists think these bubbles are generated and heated to X-ray temperatures when powerful stellar winds from the young massive stars collide and push aside the surrounding gas and dust. So, the vacated areas are immediately repopulated with the hotter material seen by Chandra.
However, there is a difference between the two sides of this bifurcated stellar city. (Rollover the image above or view this separate annotated image for the location of the "wall".) On the western (right) side, the amount of hot gas found in the bubbles corresponds to about 4300 times the mass of the sun. This value and the brightness of the gas in X-rays imply that the western part of NGC 604 is entirely powered by winds from the 200 hot massive stars.
This result is interesting because previous modeling of other bubbles usually predicted them to be fainter than observed, so that additional heating from supernova remnants is required. The implication is that in this area of NGC 604, none or very few of the massive stars must have exploded as supernovas.
The situation is different on the eastern (left) side of NGC 604. On this side, the X-ray gas contains 1750 times the mass of the sun and winds from young stars cannot explain the brightness of the X-ray emission. The bubbles on this side appear to be much older and were likely created and powered by young stars and supernovas in the past.
A similar separation between east and west is seen in the optical results. This implies that a massive wall of gas shields the relatively quiet region in the east from the active star formation in the west.
This study was led by Ralph Tuellmann of the Harvard Smithsonian Center for Astrophysics and was part of a very deep, 16-day long observation of M33 called the Chandra ACIS Survey of M33, or ChASeM33.
Meteor Crater is a meteorite impact crater approximately 37 miles (60 km) east of Flagstaff and 18 miles (29 km) west of Winslow in the northern Arizona desert of the United States. Because the United States Board on Geographic Names commonly recognizes names of natural features derived from the nearest post office, the feature acquired the name of "Meteor Crater" from the nearby post office named Meteor. The site was formerly known as the Canyon Diablo Crater and fragments of the meteorite are officially called the Canyon Diablo Meteorite. Scientists refer to the crater as Barringer Crater in honor of Daniel Barringer, who was first to suggest that it was produced by meteorite impact. The crater is privately owned by the Barringer family through their Barringer Crater Company, which proclaims it to be the "best preserved meteorite crater on Earth".
Despite its importance as a geological site, the crater is not protected as a national monument, a status that would require federal ownership. It was designated a National Natural Landmark in November 1967.
Meteor Crater lies at an elevation of about 1,740 m (5,710 ft) above sea level. It is about 1,200 m (3,900 ft) in diameter, some 170 m (560 ft) deep, and is surrounded by a rim that rises 45 m (148 ft) above the surrounding plains. The center of the crater is filled with 210–240 m (690–790 ft) of rubble lying above crater bedrock. One of the interesting features of the crater is its squared-off outline, believed to be caused by existing regional jointing (cracks) in the strata at the impact site.
The crater was created about 50,000 years ago during the Pleistocene epoch, when the local climate on the Colorado Plateau was much cooler and damper. The area was an open grassland dotted with woodlands inhabited by woolly mammoths and giant ground sloths.
Since the crater's formation, the rim is thought to have lost 15–20 m (49–66 ft) of height at the rim crest due to natural erosion. Similarly, the basin of the crater is thought to have approximately 30 m (98 ft) of additional post-impact sedimentation from lake sediments and of alluvium. These erosion processes are the reason that very few remaining craters are visible on Earth, since many have been erased by these geological processes. The relatively young age of Meteor Crater, paired with the Arizona climate, have allowed this crater to remain almost unchanged since its formation. The lack of erosion that preserved the crater's shape helped lead to this crater being the first crater recognized as an official impact crater from a natural celestial body.
The object that excavated the crater was a nickel-iron meteorite about 50 meters (160 feet) across. The speed of the impact has been a subject of some debate. Modeling initially suggested that the meteorite struck at up to 20 kilometers per second (12 miles per second) but more recent research suggests the impact was substantially slower, at 12.8 kilometers per second (8.0 miles per second). It is believed that about half of the impactor's bulk was vaporized during its descent. Impact energy has been estimated at about 10 megatons. The meteorite was mostly vaporized upon impact, leaving little remains in the crater.
Image Credit: National Map Seamless Server
Explanation from: https://en.wikipedia.org/wiki/Meteor_Crater