omnianasa/nasa-apod-metadata huggingface dataset:
Could Hydrogen Peroxide Life Survive on Mars? (2007-08-28)
Is there life on Mars?  Although no unambiguous evidence for indigenous life on Mars has ever been found, a more speculative question -- could some life forms survive on Mars -- has taken on a new twist.  Two planetary scientists recently speculated that were extremophile microbes to involve a mixture of hydrogen peroxide (H2O2) and water (H2O), these microbes might well be able survive the thin, cold, dry atmosphere on Mars.  Life that involves hydrogen peroxide does exist here on Earth, they note, and such life would be better able to absorb water on Mars. They also claim that such life would be consistent with the ambiguous results coming out from the life-detecting experiments aboard the old Viking Landers. Although such speculation is not definitive, debating possibilities for life on Mars has again proven to be fun and a magnet for media attention.   Pictured above, the Viking Lander 2 captured an unusual image of the Martian surface in 1979 sporting a thin layer of seasonal water ice.
Gigantic Jets Over Oklahoma (2007-08-29)
Have you ever seen a gigantic jet?  They are extremely rare but tremendously powerful. Gigantic jets are a newly discovered type of lightning discharge between some thunderstorms and the Earth's ionosphere high above them.  Pictured above is one such jet caught by accident by a meteor camera in Oklahoma, USA.  The gigantic jet, at the lower left, traversed perhaps 70 kilometers in just under one second.  Clicking on the image will bring up a movie in many browsers, also visible here. Gigantic jets are much different from regular cloud-to-cloud and cloud-to-ground lightning. The bottoms of gigantic jets appear similar in appearance to another type cloud-to-ionosphere strike called blue jets, while the tops appear similar to upper-atmosphere red sprites. Although the mechanism and trigger that causes gigantic jets is a topic of research, it is clear that the jets reduce charge imbalance between different parts of Earth's atmosphere.  A good way to look for gigantic jets is to watch a powerful but distant thunderstorm from a clear location.
Dark Lunar Eclipse (2007-08-30)
The Moon passed close to the center of Earth's shadow on August 28th. Seen best by skywatchers in western North America, and the Pacific region, the resulting total lunar eclipse was a dark one, lasting about 90 minutes. In this telescopic image taken near mid totality from Yass, NSW Australia, the 85 kilometer wide ray crater Tycho lies near the top right of the shadowed lunar surface. Of course, even during a total lunar eclipse,the Moon is not completely dark. Instead the Moon remains visible during totality, reflecting reddened light filtering into the Earth's shadow. The light comes from all the sunsets and sunrises, as seen from the lunar perspective, around the edges of a silhouetted Earth.
Stars Forming in Serpens (2007-08-31)
Stars are forming in a dense molecular cloud a mere 1,000 light-years away in the constellation Serpens Cauda (The Serpent's Tail). At that estimated distance, this sharp, near-infrared close-up of the active Serpens star-forming region spans about 2 arcminutes or just over half a light-year. Though such near-infrared observations can be made by mountain-top telescopes with specialized detectors, near-infrared light has too long a wavelength to be visible to the eye. This view was recorded with a sensitive camera, HAWK-I (High Acuity, Wide field K-band Imaging), just commissioned at the Paranal Observatory in Chile. Intended to illustrate HAWK-I's impressive capabilities, the tantalizing image highlights reddish young stars and protostars, likely up to a few million years old, emerging from the nebular gas and dust.
Kalamalka Lake Eclipse (2007-09-01)
Recorded on August 28th, this serene total lunar eclipse sequence looks southwest down Kalamalka Lake toward the lights of Coldstream, British Columbia. An exposure every 4 minutes captured the Moon's position and eclipse phase, until the Moon set behind the town lights and a hill on the horizon. In fact, the sequence effectively measures the duration of the total phase of the eclipse. Around 270 BC, the Greek astronomer Aristarchus also measured the duration of lunar eclipses - though probably without the benefit of digital clocks and cameras. Still, using geometry, he devised a simple and impressively accurate way to calculate the Moon's distance, in terms of the radius of planet Earth, from the eclipse duration.
Lunation (2007-09-02)
Our Moon's appearance changes nightly.  This time-lapse sequence shows what our Moon looks like during a lunation, a complete lunar cycle.  As the Moon orbits the Earth, the half illuminated by the Sun first becomes increasingly visible, then decreasingly visible.  The Moon always keeps the same face toward the Earth.  The Moon's apparent size changes slightly, though, and a slight wobble called a  libration is discernable as it progresses along its elliptical orbit. During the cycle, sunlight reflects from the Moon at different angles, and so illuminates different features differently.  A full lunation takes about 29.5 days, just under a month (moon-th). Click on the picture to view the animated gif file.
The Colorful Clouds of Rho Ophiuchi (2007-09-03)
The many spectacular colors of the Rho Ophiuchi (oh'-fee-yu-kee) clouds highlight the many processes that occur there.  The blue regions shine primarily by reflected light.  Blue light from the star Rho Ophiuchi and nearby stars reflects more efficiently off this portion of the nebula than red light.  The Earth's daytime sky appears blue for the same reason.  The red and yellow regions shine primarily because of emission from the nebula's atomic and molecular gas.  Light from nearby blue stars - more energetic than the bright star  Antares - knocks electrons away from the gas, which then shines when the electrons recombine with the gas.  The dark regions are caused by dust grains - born in young stellar atmospheres - which effectively block light emitted behind them.  The Rho Ophiuchi star clouds, well in front of the globular cluster M4 visible  above on far lower left, are even more colorful than humans can see - the clouds emits light in every wavelength band from the radio to the gamma-ray.
A Path Into Victoria Crater (2007-09-04)
What's inside Victoria Crater?  Now that the dust has settled from the regional Martian dust storms that immobilized the rolling Martian rovers, the task ahead has become clear.  Opportunity arrived at Victoria Crater last month and was poised to enter when the dust storms flared up unexpectedly.  The above image was taken last week by the Opportunity rover perched at a possibly traversable slope into the 750-meter impact feature.  Victoria Crater is the largest crater that either Martian rover has come across during their explorations.  The crater walls might hold clues about the Martian surface before the tremendous impact that created Victoria Crater.
Aurigids from 47,000 Feet (2007-09-05)
On September 1, Aurigid meteors filled the sky, in keeping with an innovative prediction of an outburst from this historically tentative meteor shower. The prediction was made by Peter Jenniskens of the SETI Institute, in work with Esko Lyytinen of Finland and Jeremie Vaubaillon of Caltech. Astronomers flying at 47,000 feet on a dedicated mission to observe the outburst collected image data for this composite photo of the Aurigids' bright and colorful streaks. The source of the shower is understood to be Comet Kiess, a comet that would have swung through the inner solar system around 2,000 years ago, and again in 1911. Pushed outward by solar radiation pressure, dust from the tail of the comet has been drifting toward the Earth's orbit, creating the 2007 outburst as well as outbursts of the Aurigids recorded in 1935, 1986, and 1994. Of course, the shower's radiant point is in the eponymous constellation Auriga, the Charioteer.
Time Tunnel (2007-09-06)
Spiky stars are nearby, but fuzzy galaxies are strewn far across the Universe in this cosmic view. Spanning about 1/2 degree on the sky, the pretty picture is the result of astronomer Johannes Schedler's project to look back in time, toward a quasar 12.7 billion light-years away. The quasar is just visible in the full resolution image at the position marked by short vertical lines (center). The intrinsically bright nucleus of a young, active galaxy powered by a supermassive black hole, the quasar was recently identified as one of the most distant objects known. Since light travels at a finite speed, the galaxies receding into the distance are seen as they were in the increasingly remote past. The quasar appears as it did about 12.7 billion years ago, when the Universe was just 7 percent of its present age. Of course, the expansion of the Universe has redshifted the light. Schedler added image data extending to the near-infrared, acquired by collaborator Ken Crawford, to detect the distant quasar, with a measured redshift of 6.04.
South Pole Lunar Eclipse (2007-09-07)
The Moon was up continuously for 14 days in August -- when viewed from the South Pole. But during the total lunar eclipse on August 28, it circled only about 10 degrees above the horizon. For Robert Schwarz, the resulting long line-of-sight through the atmosphere that blurred his images was a minor problem when he recorded this four hour long lunar eclipse sequence. A more severe problem was the outdoor air temperature of -68 C (-90 F). The extreme cold required him to make the series of exposures through a slit in a window from inside a heated room. Though the heat produced convection and further blurring, it was the only way to keep the camera at a reasonable operating temperature for an extended period of time. Still, he was rewarded with this impressive record of August's lunar eclipse from a unique perspective on planet Earth.
The Voyagers' Message in a Bottle (2007-09-08)
Launched thirty years ago, NASA's Voyager 1 and 2 spacecraft are now respectively 15 and 12.5 billion kilometers from the Sun, equivalent to about 14 and 11.5 light-hours distant. Still functioning, the Voyagers are being tracked and commanded through the Deep Space Network. Having traveled beyond the outer planets, they are only the third and fourth spacecraft from planet Earth to escape toward interstellar space, following in the footsteps of Pioneer 10 and 11. A 12-inch gold plated copper disk (a phonograph record) containing recorded sounds and images representing human cultures and life on Earth, is affixed to each Voyager - a message in a bottle cast into the cosmic sea. The recorded material was selected by a committee chaired by astronomer Carl Sagan. Simple diagrams on the cover symbolically represent the spacecraft's origin and give instructions for playing the disk. The exotic construction of the disks should provide them with a long lifetime as they coast through interstellar space.
The Great Basin on Saturn's Tethys (2007-09-09)
Some moons wouldn't survive the collision.  Tethys, one of Saturn's larger moons at about 1000 kilometers in diameter, survived the collision, but sports today the expansive impact crater Odysseus.  Sometimes called the Great Basin, Odysseus occurs on the leading hemisphere of Tethys and shows its great age by the relative amount of smaller craters that occur inside its towering walls.  Another large crater, Melanthius, is visible near the moon's terminator. The density of Tethys is similar to water-ice.  The above digitally enhanced image was captured in July by the robot Cassini spacecraft  in orbit around Saturn as it swooped past the giant ice ball.
Building Galaxies in the Early Universe (2007-09-10)
What was the very early universe like?  To help find out, astronomers pointed the Hubble Space Telescope between bright nearby objects to create one of the deepest images ever -- the Hubble Ultra Deep Field (HUDF).  The resulting HUDF is like a jewel box of strange and distant galaxies.  A recent analysis of the HUDF focused on the smallest, faintest and most compact galaxies imaged.   These small galaxies are thought to be the building blocks of modern galaxies. Analysis shows that these small galaxies are indeed themselves frequently merging to form large galaxies.   An image of this field with the Spitzer Space Telescope shows a lack of infrared emission that would be expected from old stars, indicating that these small galaxies are very young, possibly only a few million years old.  Therefore the young blue stars might be members of the first-ever generation of stars. Part of the HUDF is shown above, while one blue building-block galaxy, highly redshifted by the universe so as to appear more yellow, is shown in the upper left inset.
A Scorpius Sky Spectacular (2007-09-11)
If Scorpius looked this good to the unaided eye, humans might remember it better.  Scorpius more typically appears as a few bright stars in a well known but rarely pointed out zodiacal constellation. To get a spectacular image like this, though, one needs a good camera, color filters, and a digital image processor.  To bring out detail, the above image not only involved long duration exposures taken in several colors, but one exposure in a very specific red color emitted by hydrogen that brings out great detail.  The resulting image shows many breathtaking features.  Vertically across the image left is part of the plane of our Milky Way Galaxy.   Visible there are vast clouds of bright stars and long filaments of dark dust.  Jutting out diagonally from the Milky Way in the image center are dark dust bands known as the Dark River.  This river connects to several bright stars on the right that are part of Scorpius' head and claws, and include the bright star Antares.  Above and right of Antares is an even brighter planet Jupiter. Numerous red emission nebulas and blue reflection nebulas are visible throughout the image. Scorpius appears prominently in southern skies after sunset during the middle of the year.
Six Rainbows Across Norway (2007-09-12)
Have you ever seen six rainbows at once?  They are not only rare to see -- they are a puzzle to understand.  The common rainbow is caused by sunlight internally reflected by the backs of falling raindrops, while also being refracted at the air / water boundary.   To see a rainbow, look opposite the Sun towards a rainstorm.   This primary rainbow is the brightest color swath in the above image.  Multiple internal reflections inside water droplets sometimes make a secondary rainbow to become visible outside the first, with colors reversed.  Just such a secondary rainbow is visible of the far left.  Harder to explain is the intermediate rainbow, between the two.   This rainbow is likely caused by sunlight that has first reflected off the lake before striking the distant raindrops that is reflecting sunlight back toward the observer. Each of these rainbows appears to be reflected by the calm lake, although because the positions of rainbows depend on the location of the observer, a slightly displaced image of each rainbow is actually being imaged.
NGC 7129 and NGC 7142 (2007-09-13)
This alluring telescopic image looks toward the constellation Cepheus and an intriguing visual pairing of dusty reflection nebula NGC 7129 (left) and open star cluster NGC 7142. The two appear separated by only half a degree on the sky, but they actually lie at quite different distances. In the foreground, dusty nebula NGC 7129 is about 3,000 light-years distant, while open cluster NGC 7142 is likely over 6,000 light-years away. In fact, the pervasive and clumpy foreground dust clouds in this region redden the light from NGC 7142, complicating astronomical studies of the cluster. Still, NGC 7142 is thought to be an older open star cluster, while the bright stars embedded in NGC 7129 are perhaps a million years young. The telltale reddish crescent shapes around NGC 7129 are associated with energetic jets streaming away from newborn stars. Surprisingly, despite the dust, far off background galaxies can be seen in the colorful cosmic vista.
Iapetus in Black and White (2007-09-14)
Iapetus, Saturn's third largest moon, is a candidate for the strangest moon of Saturn. Tidally locked in its orbit around the ringed gas giant, Iapetus is sometimes called the yin-yang moon because its leading hemisphere is very dark, reflecting about 5 percent of the Sun's light, while its trailing hemisphere is almost as bright as snow.  This recent Cassini spacecraft flyby image is one of the closest views ever. It spans about 35 kilometers across a cratered transition zone between bright and dark terrain. Iapetus itself has a density close to that of water ice, but the detailed reflective properties of the dark material suggest an organic composition. Honoring the moon's discoverer, the dark terrain is called Cassini Regio.
Iapetus: 3D Equatorial Ridge (2007-09-15)
This bizarre, equatorial ridge extending across and beyond the dark, leading hemisphere of Iapetus gives the two-toned Saturnian moon a distinct walnut shape. With red/blue glasses you can check out a remarkable stereo composition of this extraordinary feature -- based on close-up images from this week's Cassini spacecraft flyby. In fact, the ridge's combination of equatorial symmetry and scale, about 20 kilometers wide and reaching up to 20 kilometers above the surface, is not known to be duplicated anywhere else in our solar system. The unique feature was discovered in Cassini images from 2004. It appears to be heavily cratered and therefore ancient, but the origin of the equatorial ridge on Iapetus remains a mystery.
To Fly Free in Space (2007-09-16)
At about 100 meters from the cargo bay of the space shuttle Challenger, Bruce McCandless II was further out than anyone had ever been before.  Guided by a Manned Maneuvering Unit (MMU), astronaut McCandless, pictured above, was floating free in space. McCandless and fellow NASA astronaut Robert Stewart were the first to experience such an "untethered space walk" during Space Shuttle mission  41-B in 1984.  The MMU works by shooting jets of nitrogen and has since been used to help deploy and retrieve satellites.  With a mass over 140 kilograms, an MMU is heavy on Earth, but, like everything, is weightless when drifting in orbit. The MMU was replaced with the SAFER backpack propulsion unit.
Inside Victoria Crater on Mars (2007-09-17)
NASA's Opportunity rover is now inside Victoria Crater on Mars.  Last week the robot rolled about 20 meters into the largest crater any Martian rover has yet encountered, the crater next to which Opportunity has been perched for months.  Currently, the rolling explorer is situated in Duck Bay alcove, peering across at the internal crater wall dubbed Cape St. Vincent. The above wide-angle view is from Opportunity's front hazard-identification camera.  Over the next few weeks, Opportunity is scheduled to explore this telling alien indentation, searching for clues to the ancient past of Mars before the huge impact that created Victoria Crater ever took place.
Tungurahua Erupts (2007-09-18)
Volcano Tungurahua erupted spectacularly last year.  Pictured above, molten rock so hot it glows visibly pours down the sides of the 5,000-meter high Tungurahua, while a cloud of dark ash is seen being ejected toward the left.  Wispy white clouds flow around the lava-lit peak, while a star-lit sky shines in the distance.  The above image was captured last year as ash fell around the adventurous photographer.  Located in Ecuador, Tungurahua has become active roughly every 90 years since for the last 1,300 years.   Volcano Tungurahua has started erupting again this year and continues erupting at a lower level even today.   APOD editor to review best space pictures in Philadelphia next Wednesday
4,000 Kilometers Above Saturn's Iapetus (2007-09-19)
What does the surface of Saturn's mysterious moon Iapetus look like? To help find out, the robotic Cassini spacecraft now orbiting Saturn was sent soaring last week just 2,000 kilometers from the unique equatorial ridge of the unusual walnut-shaped two-toned moon. The above image from Cassini is from about 4,000 kilometers out and allows objects under 100-meters across to be resolved.  Cassini found an ancient and battered landscape of craters, sloping hills, and mountains as high as 10 kilometers and so rival the 8.8-kilometer height of Mt. Everest on Earth.  Just above the center of this image is a small bright patch where an impacting rock might have uncovered deep clean water ice.  Space scientists will be studying flyby images like this for clues to the origin of Iapetus' unusual shape and coloring with particular emphasis because no more close flybys of the enigmatic world are planned.   APOD editor to review best space pictures in Philadelphia next Wednesday
Northern Cygnus (2007-09-20)
Bright, hot, supergiant star Deneb lies at top center in this gorgeous skyscape. The 20 frame mosaic spans an impressive 12 degrees across the northern end of Cygnus the Swan. Crowded with stars and luminous gas clouds along the plane of our Milky Way Galaxy, Cygnus is also home to the dark, obscuring Northern Coal Sack Nebula, extending from Deneb toward the bottom center of the view. The reddish glow of NGC 7000, the North America Nebula, and IC 5070, the Pelican Nebula, are at the upper left, but many other nebulae and star clusters are identifiable throughout the wide field. Of course, Deneb itself is the alpha star of Cygnus and is also known to northern hemisphere skygazers for its place in two asterisms -- marking the top of the Northern Cross and a vertex of the Summer Triangle.
Coronet in the Southern Crown (2007-09-21)
X-rays from young stars and infrared light from stars and cosmic dust are combined in this false color image of a star-forming region in Corona Australis, the Southern Crown. The small star grouping is fittingly known as the Coronet Cluster. A mere 420 light-years distant, the Coronet Cluster offers a relatively close-up view of stars and protostars evolving with a wide range of masses. The observations suggest that energetic x-rays come from the hot, extended stellar atmospheres or coronae of the Coronet stars. The tantalizing multi-wavelength view spans about 2 light-years and was produced using data from the orbiting Chandra Observatory (x-ray) and the Spitzer Space Telescope (infrared).
Pangea Ultima: Earth in 250 Million Years? (2007-09-22)
Is this what will become of the Earth's surface?  The surface of the Earth is broken up into several large plates that are slowly shifting.  About 250 million years ago, the plates on which the present-day continents rest were positioned quite differently, so that all the landmasses were clustered together in one supercontinent now dubbed Pangea.  About 250 million years from now, the plates are again projected to reposition themselves so that a single landmass dominates.  The above simulation from the PALEAOMAP Project shows this giant landmass: Pangea Ultima.  At that time, the Atlantic Ocean will be just a distant memory, and whatever beings inhabit Earth will be able to walk from North America to Africa.  APOD editor to review best space pictures in Philadelphia on Wednesday
The Equal Night (2007-09-23)
Today, the Sun crosses the celestial equator heading south at 0951 UT. Known as the equinox, the astronomical event marks the first day of autumn in the northern hemisphere and spring in the south. Equinox means equal night and with the Sun on the celestial equator, Earth dwellers will experience nearly 12 hours of daylight and 12 hours of darkness. Of course, for those in the south, the days will grow longer with the Sun marching higher in the sky as summer approaches. A few weeks after the September Equinox of 1994, the Crew of the shuttle orbiter Endeavour recorded this image of the Sun poised above the Earth's limb. Glare illuminates Endeavour's vertical tail (pointing toward the Earth) along with radar equipment in the payload bay.