Geological Map of Vesta

This high-resolution geological map of Vesta is derived from Dawn spacecraft data. Brown colors represent the oldest, most heavily cratered surface. Purple colors in the north and light blue represent terrains modified by the Veneneia and Rheasilvia impacts, respectively. Light purples and dark blue colors below the equator represent the interior of the Rheasilvia and Veneneia basins. Greens and yellows represent relatively young landslides or other downhill movement and crater impact materials, respectively. This map unifies 15 individual quadrangle maps published this week in a special issue of Icarus. Map is a Mollweide projection, centered on 180 degrees longitude using the Dawn Claudia coordinate system.

Map credit: NASA/JPL-Caltech/ASU

Note: For more information, see PIA18789: Geological Time Scale of Vesta and Geologic Maps of Vesta from NASA's Dawn Mission Published.

Artist’s Impression of Bright Exozodiacal Light

This artist’s view from an imagined planet around a nearby star shows the brilliant glow of exozodiacal light extending up into the sky and swamping the Milky Way. This light is starlight reflected from hot dust created as the result of collisions between asteroids, and the evaporation of comets. The presence of such thick dust clouds in the inner regions around some stars may pose an obstacle to the direct imaging of Earth-like planets in the future.

Illustration credit: ESO/L. Calçada

Note: For more information, see VLTI Detects Exozodiacal Light.

Grooves on Asteroid 21 Lutetia

A portion of asteroid Lutetia, looking into the 55 km-wide Massilia crater (red circular outline) with the North Pole Crater Cluster (NPCC) in the distance (purple outline). The grooves (or ‘lineaments’) are colored according to the crater to which they are associated, i.e. red for Massilia and purple for NPCC. The blue lineaments are associated with the ‘Suspicio’ crater, while the yellow lineaments are not associated with any crater discussed in this study.

Lutetia was imaged in July 2010 by ESA’s Rosetta spacecraft, while en route to Comet 67P/Churyumov-Gerasimenko. Rosetta took images of the 100 km-wide asteroid for about two hours during the flyby. At its closest approach, Rosetta was 3162 km from Lutetia. In the image shown here, north is up.

Image credit: Besse et al (2014); image: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Note: For more information, see Lutetia's Dark Side Hosts Hidden Crater.

Artist's Conception of a Protoplanetary Collision

Planets, including those like our own Earth, form from epic collisions between asteroids and even bigger bodies, called proto-planets. Sometimes the colliding bodies are ground to dust, and sometimes they stick together to ultimately form larger, mature planets.

This artist's conception shows one such smash-up, the evidence for which was collected by NASA's Spitzer Space Telescope. Spitzer's infrared vision detected a huge eruption around the star NGC 2547-ID8 between August 2012 and 2013. Scientists think the dust was kicked up by a massive collision between two large asteroids. They say the smashup took place in the star's "terrestrial zone," the region around stars where rocky planets like Earth take shape.

NGC 2547-ID8 is a sun-like star located about 1,200 light-years from Earth in the constellation Vela. It is about 35 million years old, the same age our young sun was when its rocky planets were finally assembled via massive collisions -- including the giant impact on proto-Earth that led to the formation of the moon. The recent impact witnessed by Spitzer may be a sign of similar terrestrial planet building. Near-real-time studies like these help astronomers understand how the chaotic process works.

Illustration credit: NASA/JPL-Caltech

Note: For more information, see PIA18470: Witnessing a Planetary Wreckage and NASA's Spitzer Telescope Witnesses Asteroid Smashup.

Asteroid 21 Lutetia

This ethereal image shows a stunning sliver of large main-belt asteroid Lutetia from the viewpoint of ESA’s Rosetta spacecraft, taken as Rosetta passed by on its 10-year voyage towards comet 67P/Churyumov–Gerasimenko.

This week marks four years since Rosetta flew by this ancient rocky body, on 10 July 2010. As the spacecraft swung past Lutetia it snapped hundreds of high-resolution photographs with its Optical, Spectroscopic and Infrared Remote Imaging System (OSIRIS) as well as obtaining valuable spectra, and maps of the surface temperature using other instruments.

This image was taken as Rosetta had passed its closest approach, at just under 3170 km from Lutetia’s surface, and was beginning its journey away from the asteroid.

As a result of this flyby, astronomers have been able to characterize Lutetia, viewing the wide range of craters and geological features scarring the asteroid’s surface and gauging its mass and volume–and thus density and composition. These measurements showed that Lutetia is primordial, likely having formed just under 4 billion years ago during the very early phases of the Solar System.

This asteroid is one of just two that Rosetta has closely flown past, the other being asteroid Steins in 2008.

Rosetta was launched in 2004 and, after 10 years in space, will finally rendezvous with its target comet in August. It will study the comet’s surface, dust and gases in unprecedented detail, deploy a lander onto its surface, and follow the comet for over a year as it orbits around the Sun.

Image credit: ESA 2010 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA

Asteroid 2011 MD by Spitzer

This image of asteroid 2011 MD was taken by NASA's Spitzer Space Telescope in February 2014, over a period of 20 hours. The long observation, taken in infrared light, was needed to pick up the faint signature of the small asteroid (center of frame). The Spitzer observations helped narrow down the size of the space rock to roughly 20 feet (6 meters), making it one of a few candidates for NASA's proposed Asteroid Redirect Mission for which sizes are approximately known.

This image was taken by Spitzer's Infrared Array Camera at a wavelength of 4.5 microns.

Image credit: NASA/JPL-Caltech/Northern Arizona University/SAO

Note: For more information, see Spitzer Spies an Odd, Tiny Asteroid. For more information on NASA's Asteroid Redirect Mission, see NASA Update on Asteroid Redirect Mission and NASA Announces Latest Progress in Hunt for Asteroids.

Asteroid 2014 HQ124

NASA scientists used Earth-based radar to produce these sharp views -- an image montage and a movie sequence -- of the asteroid designated "2014 HQ124" on June 8, 2014.

2014 HQ124 is what scientists call a "contact binary": an asteroid that consists of two lobes that are in contact and that could have once been separate objects. About one in six asteroids in the near-Earth population has this type of elongated, "peanut" shape.

The asteroid is about 1,300 feet (400 meters) long and about half as wide. The radar images reveal a wealth of interesting features, including a large depression or concavity on the larger lobe as well as two blocky, sharp-edged features at the bottom on the radar echo. Scientists suspect that some of the bright features that persist from frame to frame could be surface boulders.

The 21 radar images were taken over a span of four hours. During that interval, the asteroid rotated a few degrees per frame, suggesting its rotation period is slightly less than 24 hours.

At its closest approach to Earth on June 8, the asteroid came within 776,000 miles (1.25 million kilometers), or slightly more than three times the distance to the moon. Scientists began radar observations of 2014 HQ124 shortly after the closest approach, when the asteroid was between about 864,000 miles (1.39 million kilometers) and 902,000 miles (1.45 million kilometers) from Earth.

The new views show features as small as about 12 feet (3.75 meters) wide. This is the highest resolution currently possible using scientific radar antennas to produce images. Such sharp views were made possible for this asteroid by linking together two giant radio telescopes to enhance their capabilities.

To obtain the new views, researchers paired the 230-foot (70-meter) Deep Space Network antenna at Goldstone, California, with two other radio telescopes, one at a time. Using this technique, the Goldstone antenna beams a radar signal at an asteroid and the other antenna receives the reflections. The technique dramatically improves the amount of detail that can be seen in radar images.

To image 2014 HQ124, the researchers first paired the large Goldstone antenna with the 1000-foot (305-meter) Arecibo radio telescope in Puerto Rico. They later paired the large Goldstone dish with a smaller companion, a 112-foot (34-meter) antenna, located about 20 miles (32 kilometers) away.

The first five images in the sequence -- the top row in the montage -- represent the data collected by Arecibo, and demonstrate that these data are 30 times brighter than what Goldstone can produce observing on its own. There is a gap of about 35 minutes between the first and second rows in the montage, or between the fifth and sixth frames in the video. The gap represents the time needed to switch from receiving at Arecibo to receiving at the smaller Goldstone station.

Each image in the montage and movie represents 10 minutes of data. Each frame has the same orientation, delay-Doppler dimensions and resolution (3.75 meters by 0.0125 Hertz).

For asteroids, as well as comets, radar is a powerful tool for studying the objects' size, shape, rotation, surface features and orbits. Radar measurements of asteroid distances and velocities enable researchers to compute orbits much further into the future than if radar observations were not available.

Image credit: NASA/JPL-Caltech/Arecibo Observatory/USRA/NSF

Note: For more information, see Giant Telescopes Pair Up to Image Near-Earth Asteroid.

The Night Sky from Mars

The Mast Camera (Mastcam) on NASA's Curiosity Mars rover has captured the first image of an asteroid taken from the surface of Mars. The night-sky image actually includes two asteroids: Ceres and Vesta, plus one of Mars' two moons, Deimos, which may have been an asteroid before being captured into orbit around Mars. The image was taken after nightfall on the 606th Martian day, or sol, of Curiosity's work on Mars (April 20, 2014, PDT). In other camera pointings the same night, the Mastcam also imaged Mars' larger moon, Phobos, plus the planets Jupiter and Saturn.

Ceres, with a diameter of about 590 miles (950 kilometers), is the largest object in the asteroid belt, large enough to be classified as a dwarf planet. Vesta is the third-largest object in the asteroid belt, about 350 miles (563 kilometers) wide. These two bodies are the destinations of NASA's Dawn mission, which orbited Vesta in 2011 and 2012 and is on its way to begin orbiting Ceres in 2015.

This annotated image combines portions of images taken at the same pointing with two different exposure times, plus insets from other camera pointings. In the main portion of the image, Vesta, Ceres and three stars appear as short streaks due to the duration of a 12-second exposure. The background is detector noise, limiting what we can see to magnitude 6 or 7, much like normal human eyesight. The two asteroids and three stars would be visible to someone of normal eyesight standing on Mars. Specks are effects of cosmic rays striking the camera's light detector.

Three square insets at left show Phobos, Jupiter and Saturn at exposures of one-half second each. Deimos was much brighter than the visible stars and asteroids in the same part of the sky, in the main image. The circular inset covers a patch of sky the size that Earth's full moon appears to observers on Earth. At the center of that circular inset, Deimos appears at its correct location in the sky, in a one-quarter-second exposure. In the unannotated version of the 12-second-exposure image, the brightness of Deimos saturates that portion of the image, making the moon appear overly large.

Image credit: NASA/JPL-Caltech/MSSS/Texas A&M

Note: For more information, see Asteroids as Seen From Mars; A Curiosity Rover First.

Rings Around Asteroid 10199 Chariklo

Observations at many sites in South America, including ESO’s La Silla Observatory, have made the surprise discovery that the remote asteroid Chariklo is surrounded by two dense and narrow rings. This is the smallest object by far found to have rings and only the fifth body in the Solar System — after the much larger planets Jupiter, Saturn, Uranus and Neptune — to have this feature. The origin of these rings remains a mystery, but they may be the result of a collision that created a disc of debris.

This artist’s impression shows how the rings might look from close to the surface of Chariklo.

Illustration credit: ESO/L. Calçada/Nick Risinger (skysurvey.org)

Note: For more information, see First Ring System Around Asteroid.

Update: A new video shows how the occultation of a star by Asteroid 10199 Chariklo revealed the two rings that orbit the asteroid.

Asteroid P/2013 R3 Disintegrates

This series of images shows the asteroid P/2013 R3 breaking apart, as viewed by the NASA/ESA Hubble Space Telescope in 2013. This is the first time that such a body has been seen to undergo this kind of break-up.

The Hubble observations showed that there are ten distinct objects, each with comet-like dust tails, embedded within the asteroid's dusty envelope. The four largest rocky fragments are up to 200 meters in radius, about twice the length of a football pitch.

The date increases from left to right, with frames from 29 October 2013, 15 November 2013, 13 December 2013, and 14 January 2014 respectively, showing how the clumps of debris material move around. The 14 January 2014 frame was not included in the science paper and is additional data.

Image credit: (top) NASA, ESA, D. Jewitt (UCLA); (bottom) NASA, ESA, D. Jewitt (UCLA)

Note: For more information, see Hubble Witnesses an Asteroid Mysteriously Disintegrating and Hubble Witnesses Asteroid's Mysterious Disintegration.

Comet NEOWISE C2014 C3

Comet NEOWISE was first observed by NASA's Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) spacecraft on Valentine's Day, 2014. This heat-sensitive infrared image was made by combining six exposures taken by the NEOWISE mission of the newly discovered comet. The image shows 1/20th of a degree of sky on a side, or about 155,000 miles (250,000 kilometers) at the comet's distance. The NEOWISE mission searches for asteroids and comets using two infrared wavelength channels. The shorter wavelength, at 3.4 microns [or millionths of a meter], is mapped to cyan and the longer wavelength, at 4.6 microns [or millionths of a meter], is shown in red. The tail of the comet NEOWISE extends about 25,000 miles (40,000 kilometers) to the right in the image.

Image credit: NASA/JPL-Caltech

Note: For more information, see NEOWISE Spies Its First Comet.

Asteroid 2006 DP14

This image is one frame from a collage of radar images taken on February 11, 2014, of near-Earth asteroid 2006 DP 14, which is about 1,300 feet (400 meters) long. The imaging used the 230-foot (70-meter) Deep Space Network antenna at Goldstone, California, while the asteroid was about 11 times farther from Earth than the moon is.

A collage of radar images of near-Earth asteroid 2006 DP14 was generated by NASA scientists using the 230-foot (70-meter) Deep Space Network antenna at Goldstone, California, on the night of February 11, 2014.

Delay-Doppler radar imaging revealed that the asteroid is about 1,300 feet (400 meters) long, 660 feet (200 meters) wide, and shaped somewhat like a big peanut. The asteroid's period of rotation is about six hours. The asteroid is of a type known as a "contact binary" because it has two large lobes on either end that appear to be in contact. Previous radar data from Goldstone and the Arecibo Observatory in Puerto Rico has shown that at least 10 percent of near-Earth asteroids larger than about 650 feet (200 meters) have contact binary shapes like that of 2006 DP14. The data were obtained over an interval of 2.5 hours as the asteroid completed about half a revolution. The resolution is about 60 feet (19 meters) per pixel.

The data were obtained on February 11 between 9:03 a.m. and 11:27 p.m. PST (12:03 a.m. to 2:27 a.m. EST on February 12). At the time of the observations, the asteroid's distance was about 2.6 million miles (4.2 million kilometers) from Earth. That is about 11 times the average distance between Earth and its moon. The asteroid's closest approach to Earth occurred on February 10, at a distance of about 1.5 million miles (2.4 million kilometers).

Radar is a powerful technique for studying an asteroid's size, shape, rotation state, surface features and surface roughness, and for improving the calculation of asteroid orbits. Radar measurements of asteroid distances and velocities often enable computation of asteroid orbits much further into the future than if radar observations weren't available.

NASA places a high priority on tracking asteroids and protecting our home planet from them. In fact, the United States has the most robust and productive survey and detection program for discovering near-Earth objects. To date, U.S. assets have discovered more than 98 percent of the known near-Earth objects.

Image credit: NASA/JPL-Caltech/GSSR

Structural Composition of Asteroid 25143 Itokawa

A schematic view of the strange peanut-shaped asteroid Itokawa.

By making exquisitely precise timing measurements using ESO’s New Technology Telescope, and combining them with a model of the asteroid's surface topography, a team of astronomers has found that different parts of this asteroid have different densities. As well as revealing secrets about the asteroid’s formation, finding out what lies below the surface of asteroids may also shed light on what happens when bodies collide in the Solar System, and provide clues about how planets form. The shape model used for this view is based on the images collected by JAXA's Hayabusa spacecraft.

This very detailed view shows the strange peanut-shaped asteroid Itokawa. By making exquisitely precise timing measurements using ESO’s New Technology Telescope a team of astronomers has found that different parts of this asteroid have different densities. As well as revealing secrets about the asteroid’s formation, finding out what lies below the surface of asteroids may also shed light on what happens when bodies collide in the Solar System, and provide clues about how planets form.

This picture comes from the Japanese spacecraft Hayabusa during its close approach in 2005.

Top illustration credit: ESO. Acknowledgement: JAXA. Bottom photo credit: JAXA

Note: For more information, see The Anatomy of an Asteroid.

Asteroid 2415 Ganesa and Star Cluster NGC 2158

More than 100 asteroids were captured in this view from NASA's Wide-field Infrared Survey Explorer, or WISE, during its primary all-sky survey. In August of this year, the mission was revived to hunt more asteroids, and renamed NEOWISE.

Not all of the asteroids are easy to see, but some stand out as a series of dots. Each dot in a track shows one asteroid, captured at different times as it marched across the sky. The asteroid at center left is called (2415) Ganesa.

Clusters of stars can also be seen; for example, NGC 2158 glitters like a jeweled brooch at center right. There are about 2,500 stars in this view, which is about 30 light-years across.

Clouds of gas and dust surround the region, visible only in infrared light.

These data were acquired in March 2010, before WISE was put into hibernation in 2011.

Image credit: NASA/JPL-Caltech/UCLA

Note: For more information, see NEOWISE Celebrates First Month of Operations After Reactivation.

Asteroid 2013 YP139

The six red dots in this composite picture indicate the location of the first new near-Earth asteroid seen by NASA's Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) since the spacecraft came out of hibernation in December 2013. The asteroid, called 2013 YP139, is the first of hundreds of space-rock discoveries expected during its renewed mission. The inset shows a zoomed-in view of one of the detections of 2013 YP139.

2013 YP139 was discovered by NEOWISE on December 29, 2013. The mission's sophisticated software picked out the moving object against a background of stationary stars.

Near-Earth objects are asteroids and comets with orbits that come close to Earth's path around the sun. 2013 YP139, is currently about 27 million miles (43 million kilometers) from Earth. Based on its infrared brightness, scientists estimate it to be approximately 0.4 miles (650 meters) in diameter and extremely dark. Because NEOWISE is an infrared telescope, it senses heat from asteroids. 2013 YP139 is as dark as a piece of coal, and it glows brightly at infrared wavelengths. The shortest infrared wavelength, 3.4 microns, is color-coded blue, and the longer wavelength, 4.6 microns, is color-coded red. The asteroid appears as a string of red dots because it is much cooler than the stars. Stars are thousands of degrees, but the asteroid is close to room temperature, so it is red in these images.

While asteroid 2013 YP139 orbits the sun in an elliptical orbit nearly in the plane of our solar system and is classified as a potentially hazardous asteroid, it is not likely to approach within Earth's vicinity anytime over the next 100 years. However, the asteroid's future motion can bring it within about 300,000 miles (490,000 kilometers) of Earth's orbit, so its long-term motion will be closely monitored.

The image is about 1.5 degrees across. Asteroid 2013 YP139 was traveling across the sky at about 3.2 degrees per day when these images were taken. For reference, the full moon is about 0.5 degree across.

Image credit: NASA/JPL-Caltech

Note: For more information, see Recently Reactivated NASA Spacecraft Spots Its First New Asteroid.

Asteroid 2014 AA

Several sources confirm that the first discovered asteroid in 2014, designated 2014 AA, entered Earth's atmosphere late January 1 (January 2 Universal time) over the mid-Atlantic Ocean. The Catalina Sky Survey operating near Tucson, Arizona discovered this very small asteroid -- 6 to 9 feet (2 to 3 meters) in size -- early on the morning of January 1, and immediately followed up on it. (An animation of the discovery images is shown [above]). The asteroid entered Earth's atmosphere about 21 hours later, and probably broke up.

The high-precision astrometry data and rapid follow-up observations provided by the Catalina Sky Survey team made it possible for orbit analysts from NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, California, to determine possible Earth impact locations. Before that, and based upon the Catalina Sky Survey observations, Steve Chesley of JPL produced a plot of the possible impact locations for asteroid 2014 AA. (Chesley's graphic is shown in Figure 2, where the blue, nearly horizontal band represents the region of possible impacts).

The geolocation derived by Chesley allowed Peter Brown of the University of Western Ontario, and Petrus Jenniskens of the SETI Institute, Mountain View, California, to search the data from low-frequency infrasound observation sites of the Comprehensive Nuclear-Test-Ban Treaty Organization. They found weak signals from stations in Bolivia, Brazil and Bermuda that indicated that the likely impact location was indeed positioned within the predicted area. The location, marked with a red dot, is still somewhat uncertain due to observational factors, including atmospheric effects on the propagation of infrasound signals.

Infrasound stations record ultra-low-frequency sound waves to monitor the location of atmospheric explosions. These sites often pick up airbursts from small asteroid impacts, commonly called fireballs or bolides. There are about a billion near-Earth objects in the size range of 2014 AA, and impacts of comparably sized objects occur several times each year.

Uncertainties present in the infrasound technique and the very limited amount of optical tracking data before impact make it difficult to pinpoint the impact time and location. Even so, Chesley provides the following estimate:

Impact time: January 1, 2014 at 11:02 p.m. EST (January 2 4:02 UTC) Impact location coordinates: 11.7 degrees north latitude, 319.7 degrees latitude.

This information is preliminary and has uncertainties of perhaps a few hundred kilometers, or miles, in location, and tens of minutes in time.

Prior to impact, the orbit of 2014 AA had a very low inclination (about 1 degree) with respect to the ecliptic plane and an orbit that ranged from 0.9 to 1.3 astronomical units from the sun, with an orbital period of about 1.2 years.

Image credit: CSS/LPL/UA

Note: For more information, see First 2014 Asteroid Discovered: Update.

Sextilia Crater

This colorful image from NASA's Dawn mission shows material northwest of the crater Sextilia on the giant asteroid Vesta. Sextilia, located around 30 degrees south latitude, is at the bottom right of this image.

The image was taken by Dawn's framing camera from September to October 2011.

In this image, the entire color spectrum of Vesta becomes visible. While a large asteroid impact probably brought the black material, the red material may have been melted by the impact.

The composite image was created by assigning ratios of color information collected from several color filters in visible light and near-infrared light to maximize subtle differences in lithology (the physical characteristics of rock units, such as color, texture and composition). The color scheme pays special attention to the iron-rich mineral pyroxene.

Image credit: NASA/JPL-Caltech/UCLAMPS/DLR/IDA

Note: For more information, see Dawn Creates Guide to Vesta's Hidden Attractions.

Rock Comet 3200 Phaethon

Meteor showers are supposed to come from comets, yet there is no comet that matches the orbit of the Geminid debris stream. Instead, the orbit of the Geminids is occupied by a thing called "3200 Phaethon." Discovered in 1983 by NASA's IRAS satellite, Phaethon looks remarkably like a rocky asteroid. It swoops by the sun every 1.4 years, much like a comet would, but it never sprouts a dusty tail to replenish the Geminids.

That is, until now.

A group of astronomers led by Dave Jewitt of UCLA have been using NASA’s STEREO probes to take a closer look at 3200 Phaethon when it passes by the sun. The twin spacecraft were designed to monitor solar activity, so they get a good view of sungrazing comets and asteroids. In 2010 one of the STEREO probes recorded a doubling of Phaethon's brightness as it approached the sun, as if sunlight were shining through a cloud of dust around the asteroid. The observers began to suspect 3200 Phaethon was something new:

"A rock comet", says Jewitt. A rock comet is, essentially, an asteroid that comes very close to the sun--so close that solar heating scorches dusty debris right off its rocky surface. This could form a sort of gravelly tail.

Indeed, in further STEREO observations from 2009 and 2012, Jewitt along with colleagues Jing Li of UCLA and Jessica Agarwal of the Max Planck Institute have spotted a small tail sticking out behind the "rock."

"The tail gives incontrovertible evidence that Phaethon ejects dust," says Jewitt.

Jewitt's team believes that the dust is launched by thermal fracturing of the asteroid’s crust. A related process called “desiccation fracturing”--like mud cracks in a dry lake bed--may play a role too.

Seeing 3200 Phaethon sprout a tail, even a small one, gives researchers confidence that Phaethon is indeed the source of the Geminids--but a mystery remains: How can such a stubby protuberance produce such a grand meteor shower?

Adding up all of the light STEREO saw in Phaethon’s tail, Jewitt and colleagues estimate a combined mass of some 30 thousand kilograms. That might sound like a lot of meteoroids but, in fact, it is orders of magnitude too small to sustain the massive Geminid debris stream.

Perhaps Phaethon experienced a "big event" in the recent past. “The analogy I think of is a log in a campfire,” says Jewitt. “The log burns, makes a few embers, but occasionally will spit out a shower of sparks.”

Continued monitoring by NASA's STEREO probes might one day catch the rock comet spitting out a shower of dust and debris, solving the mystery once and for all.

Until then, it's a puzzle to savor under the stars. This year's Geminid meteor shower peaks on the nights of Dec. 13-14 with dozens of “rock comet meteors” every hour. Bundle up and enjoy the show.

Text/video credit: NASA; image credit: Jewitt, Li, Agarwal /NASA/STEREO

Asteroid 872 Holda

NASA's NEOWISE spacecraft opened its "eyes" after more than two years of slumber to see the starry sky with the same clarity achieved during its prime mission. This image of a patch of sky in the constellation Pisces is among the first taken by the revived spacecraft's infrared cameras, and shows the ultimate target: asteroids. Appearing as a string of red dots, an asteroid can be seen in a series of exposures captured by the spacecraft.

The rocky body belongs to our solar system's main belt, a band of asteroids that orbits between Mars and Jupiter. NEOWISE is on the lookout for both main belt asteroids such as these, and especially for near-Earth objects (NEOs), which include asteroids and comets that pass relatively close to Earth.

The asteroid is called Holda, or 872, and was discovered in 1917.

The faint red streak in the image is an Earth-orbiting satellite passing above the NEOWISE spacecraft.

NEOWISE originated as a mission called WISE, which was put into hibernation in 2011 upon completing its goal of surveying the entire sky in infrared light. WISE cataloged three quarters of a billion objects, including asteroids, stars and galaxies. In August 2013, NASA decided to reinstate the spacecraft on a mission to find and characterize more asteroids.

Photo credit: NASA/JPL-Caltech

Note: For more information, see PIA17810: NEOWISE Opens its Eyes and NASA's Asteroid Hunter Spacecraft Returns First Images after Reactivation.

Antonia Crater

This colorized composite image from NASA's Dawn mission shows the crater Antonia, which lies in the enormous Rheasilvia basin in the southern hemisphere of the giant asteroid Vesta. The area lies around 58 degrees south latitude. Antonia has a diameter of 11 miles (17 kilometers).

The image was taken by Dawn's framing camera from September to October 2011.

The light blue material is fine-grain material excavated from the lower crust. The southern edge of the crater was buried by coarser material shortly after the crater formed. The dark blue of the southern crater rim is due to shadowing of the blocky material.

The composite image was created by assigning ratios of color information collected from several color filters in visible light and near-infrared light to maximize subtle differences in lithology (the physical characteristics of rock units, such as color, texture and composition). The color scheme pays special attention to the iron-rich mineral pyroxene.

Image credit: NASA/JPL-Caltech/UCLAMPS/DLR/IDA

Note: For more information, see Dawn Creates Guide to Vesta's Hidden Attractions.