Dawn: Journey to the Asteroid Belt

[neufer]

[b][color=#0000FF][size=150]The cover of The Dynamics of an Asteroid,[/size] from Sherlock Holmes: A Game of Shadows.[/color][/b]

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<<The Dynamics of An Asteroid is a book described by author Arthur Conan Doyle in "The Valley of Fear" (written in 1914, but set in 1888) when Sherlock Holmes, speaking of Professor Moriarty, states:

• Is he not the celebrated author of The Dynamics of an Asteroid, a book which ascends to such rarefied heights of pure mathematics that it is said that there was no man in the scientific press capable of criticizing it?
  — Sherlock Holmes, The Valley of Fear

Doyle also portrayed Professor Moriarty as the author of "a treatise on the binomial theorem", written when he was only 21 years of age. In addition to covering a completely different topic, it must have been quite a bit more accessible, since it got him a position as a chair of mathematics at a provincial university.

In 1809, Carl Friedrich Gauss wrote a ground-breaking treatise on the dynamics of an asteroid (1 Ceres). However, it was understood immediately and his method is still used today (see Gauss' Method).

Two decades before Arthur Conan Doyle's writing, the Canadian-American dynamic astronomer Simon Newcomb had published a series of books analyzing motions of planets in the solar system. The notoriously spiteful Newcomb could have been an inspiration for Professor Moriarty.

Since citation analysis does not look at a document's contents, only references to it, it can be applied to a documents such as Dynamics or Treatise that do not in fact exist. The list in the previous section shows 42 references to Dynamics and 27 to Treatise, which are a lower limit, since the list is not up to date. An online search, as of 2005, for these titles with author Moriarty, reveals 263 references to Dynamics and 209 to Treatise. These are very high numbers for any scientific paper, where the overall average is about 6 references. They are even more numerous when compared to other papers from the same era – by 1900, the Royal Society's Catalog of Scientific Papers already listed 800,000 papers from 3,000 journals. Most of these have been forgotten, and only a few are still referenced today, as shown by analyses of references to old scientific articles. The Dynamics of An Asteroid is among the select group of Victorian scientific works that are still remembered and referenced even today, despite (or perhaps because of) its fictional existence.>>

[bystander]

New Clues to Ceres' Bright Spots and Origins
NASA | JPL-Caltech | 2015 Dec 09

[c][youtube]https://www.youtube.com/watch?v=8er_0yY1S1o[/youtube]Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA [/c][hr][/hr]

Ceres reveals some of its well-kept secrets in two new studies in the journal Nature, thanks to data from NASA's Dawn spacecraft. They include highly anticipated insights about mysterious bright features found all over the dwarf planet's surface.

In one study, scientists identify this bright material as a kind of salt. The second study suggests the detection of ammonia-rich clays, raising questions about how Ceres formed.

About the Bright Spots

Ceres has more than 130 bright areas, and most of them are associated with impact craters. Study authors, led by Andreas Nathues at Max Planck Institute for Solar System Research, Göttingen, Germany, write that the bright material is consistent with a type of magnesium sulfate called hexahydrite. A different type of magnesium sulfate is familiar on Earth as Epsom salt. ...

A New Look at Occator

The surface of Ceres, whose average diameter is 584 miles (940 kilometers), is generally dark -- similar in brightness to fresh asphalt -- study authors wrote. The bright patches that pepper the surface represent a large range of brightness, with the brightest areas reflecting about 50 percent of sunlight shining on the area. But there has not been unambiguous detection of water ice on Ceres; higher-resolution data are needed to settle this question. ...

The Importance of Ammonia

In the second Nature study, members of the Dawn science team examined the composition of Ceres and found evidence for ammonia-rich clays. They used data from the visible and infrared mapping spectrometer, a device that looks at how various wavelengths of light are reflected by the surface, allowing minerals to be identified. ...

Sublimation in bright spots on (1) Ceres - A. Nathues et al

• Nature 528(7581):237 (10 Dec 2015 DOI: 10.1038/nature15754

Ammoniated phyllosilicates with a likely outer Solar System origin on (1) Ceres - M. C. De Sanctis et al

• Nature 528(7581):241 (10 Dec 2015 DOI: 10.1038/nature16172

Dwarf planet Ceres: water vapor in Occator crater
Max Planck Institute for Solar System Research | 2015 Dec 09

Brine Deposits Source of Ceres’ Bright Spots
Planetary Science Institute | 2015 Dec 09

[neufer]

<<Akatsuki ("Dawn"), also known as the Venus Climate Orbiter (VCO) is a Japanese (JAXA) space probe tasked to study the atmosphere of Venus. It was launched on 20 May 2010, and failed to enter orbit around Venus on 6 December 2010. After the craft orbited the Sun for five years, engineers placed it into an alternative elliptical Venusian orbit on December 7, 2015 by firing its attitude control thrusters for 20 minutes. By using five different cameras, Akatsuki will study the stratification of the atmosphere, atmospheric dynamics, and cloud physics.>>

[b][color=#0000FF]Dawn has entered its 4th & final Ceres mapping orbit: LAMO[/color][/b]

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Dawn Journal | by Marc Rayman

<<December 9, 2015 - Dawn completed ion-thrusting on schedule on December 7, 2015 and continues to be healthy and operating well in its new orbit. Over the last two days, the flight team has determined that the spacecraft did an excellent job in maneuvering to its planned orbit at an average altitude of 240 miles (385 kilometers). The spacecraft is even closer to the rocky, icy ground than the International Space Station is to Earth’s surface. The pictures will be four times sharper than the best it has yet taken. Dawn is so near the dwarf planet that its sensors will detect only a small fraction of the vast territory at a time. Mission planners have designed the complex itinerary so that every three weeks, Dawn will fly over most of the terrain while on the sunlit side. (The neutron spectrometer, gamma ray spectrometer and gravity measurements do not depend on illumination from the sun, but the camera, infrared mapping spectrometer and visible mapping spectrometer do.)

Obtaining the planned coverage of the exotic landscapes requires a delicate synchrony between Ceres’ and Dawn’s movements. Ceres rotates on its axis every nine hours and four minutes (one Cerean day). Dawn will revolve around it in a little less than five and a half hours, traveling from the north pole to the south pole over the hemisphere facing the sun and sailing northward over the hemisphere hidden in the darkness of night. Orbital velocity at this altitude is around 610 mph (980 kilometers per hour).>>

[bystander]

<<Akatsuki ("Dawn"), also known as the Venus Climate Orbiter (VCO) is a Japanese (JAXA) space probe tasked to study the atmosphere of Venus. It was launched on 20 May 2010, and failed to enter orbit around Venus on 6 December 2010. After the craft orbited the Sun for five years, engineers placed it into an alternative elliptical Venusian orbit on December 7, 2015 by firing its attitude control thrusters for 20 minutes. By using five different cameras, Akatsuki will study the stratification of the atmosphere, atmospheric dynamics, and cloud physics.>>

http://asterisk.apod.com/viewtopic.php?p=251334#p251334

[bystander]

Lowdown on Ceres: Images From Dawn's Closest Orbit
NASA | JPL-Caltech | Dawn | 2015 Dec 22

[img3="This image of Ceres was taken in Dawn's low-altitude mapping orbit around a crater chain called Gerber Catena. A 3-D view is also available.
Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA"]http://www.nasa.gov/sites/default/files ... n-1041.jpg[/img3][hr][/hr]

NASA's Dawn spacecraft, cruising in its lowest and final orbit at dwarf planet Ceres, has delivered the first images from its best-ever viewpoint. The new images showcase details of the cratered and fractured surface. 3-D versions of two of these views are also available.

Dawn took these images of the southern hemisphere of Ceres on Dec. 10, at an approximate altitude of 240 miles (385 kilometers), which is its lowest-ever orbital altitude. Dawn will remain at this altitude for the rest of its mission, and indefinitely afterward. The resolution of the new images is about 120 feet (35 meters) per pixel.

Among the striking views is a chain of craters called Gerber Catena, located just west of the large crater Urvara. Troughs are common on larger planetary bodies, caused by contraction, impact stresses and the loading of the crust by large mountains -- Olympus Mons on Mars is one example. The fracturing found all across Ceres' surface indicates that similar processes may have occurred there, despite its smaller size (the average diameter of Ceres is 584 miles, or 940 kilometers). Many of the troughs and grooves on Ceres were likely formed as a result of impacts, but some appear to be tectonic, reflecting internal stresses that broke the crust. ...

[orin stepanek]

Ceres; The little planet that glows on you!

[neufer]

[b][color=#0000FF]3D anaglyph LAMO photo of Ceres’ troughs [NASA/JPL-Caltech/UCLA/MPS/DLR/IDA][/color][/b]

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Lowdown on Ceres: Images From Dawn's Closest Orbit
NASA | JPL-Caltech | Dawn | 2015 Dec 22

Among the striking views is a chain of craters called Gerber Catena, located just west of the large crater Urvara.

[bystander]

New Details On Ceres Seen in Dawn Images
NASA | JPL-Caltech | Dawn | 2016 Jan 12

Features on dwarf planet Ceres that piqued the interest of scientists throughout 2015 stand out in exquisite detail in the latest images from NASA's Dawn spacecraft, which recently reached its lowest-ever altitude at Ceres.

Dawn took these images near its current altitude of 240 miles (385 kilometers) from Ceres, between Dec. 19 and 23, 2015. ...

Image Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

[i]Kupalo Crater from LAMO[/i]

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[i]Messor Crater from LAMO[/i]

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[i]Floor of Dantu Crater from LAMO[/i]

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[i]Crater with Scarps in LAMO[/i]

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[bystander]

New Animation Takes a Colorful Flight Over Ceres
NASA | JPL-Caltech | Dawn | 2016 Jan 29

Click to play embedded YouTube video.

A colorful new animation shows a simulated flight over the surface of dwarf planet Ceres, based on images from NASA's Dawn spacecraft.

The movie shows Ceres in enhanced color, which helps to highlight subtle differences in the appearance of surface materials. Scientists believe areas with shades of blue contain younger, fresher material, including flows, pits and cracks.

The animated flight over Ceres emphasizes the most prominent craters, such as Occator, and the tall, conical mountain Ahuna Mons. Features on Ceres are named for earthly agricultural spirits, deities and festivals.

The movie was produced by members of Dawn's framing camera team at the German Aerospace Center, DLR, using images from Dawn's high-altitude mapping orbit. During that phase of the mission, which lasted from August to October 2015, the spacecraft circled Ceres at an altitude of about 900 miles (1,450 kilometers). ...

[bystander]

Dawn's First Year at Ceres: A Mountain Emerges
NASA | JPL-Caltech | Dawn | 2016 Mar 07

[img3="Ahuna Mons Seen from LAMO"]http://photojournal.jpl.nasa.gov/jpeg/PIA20348.jpg[/img3]
[img3="Ahuna Mons Perspective View

Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI"]http://photojournal.jpl.nasa.gov/jpeg/PIA20349.jpg[/img3][hr][/hr]

One year ago, on March 6, 2015, NASA's Dawn spacecraft slid gently into orbit around Ceres, the largest body in the asteroid belt between Mars and Jupiter. Since then, the spacecraft has delivered a wealth of images and other data that open an exciting new window to the previously unexplored dwarf planet.

"Ceres has defied our expectations and surprised us in many ways, thanks to a year's worth of data from Dawn. We are hard at work on the mysteries the spacecraft has presented to us," said Carol Raymond, deputy principal investigator for the mission, based at NASA's Jet Propulsion Laboratory, Pasadena, California.

Among Ceres' most enigmatic features is a tall mountain the Dawn team named Ahuna Mons. This mountain appeared as a small, bright-sided bump on the surface as early as February 2015 from a distance of 29,000 miles (46,000 kilometers), before Dawn was captured into orbit. As Dawn circled Ceres at increasingly lower altitudes, the shape of this mysterious feature began to come into focus. From afar, Ahuna Mons looked to be pyramid-shaped, but upon closer inspection, it is best described as a dome with smooth, steep walls.

Dawn's latest images of Ahuna Mons, taken 120 times closer than in February 2015, reveal that this mountain has a lot of bright material on some of its slopes, and less on others. On its steepest side, it is about 3 miles (5 kilometers) high. The mountain has an average overall height of 2.5 miles (4 kilometers). It rises higher than Washington's Mount Rainier and California's Mount Whitney.

Scientists are beginning to identify other features on Ceres that could be similar in nature to Ahuna Mons, but none is as tall and well-defined as this mountain.

"No one expected a mountain on Ceres, especially one like Ahuna Mons," said Chris Russell, Dawn's principal investigator at the University of California, Los Angeles. "We still do not have a satisfactory model to explain how it formed."

About 420 miles (670 kilometers) northwest of Ahuna Mons lies the now-famous Occator Crater. Before Dawn arrived at Ceres, images of the dwarf planet from NASA's Hubble Space Telescope showed a prominent bright patch on the surface. As Dawn approached Ceres, it became clear that there were at least two spots with high reflectivity. As the resolution of images improved, Dawn revealed to its earthly followers that there are at least 10 bright spots in this crater alone, with the brightest area on the entire body located in the center of the crater. It is not yet clear whether this bright material is the same as the material found on Ahuna Mons. ...

[bystander]

Unexpected Changes of Bright Spots on Ceres Discovered
ESO Science Release | HARPS | 2016 Mar 16

[img3="Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA"]http://cdn.eso.org/images/screen/eso1609b.jpg[/img3][hr][/hr]

Observations made using the HARPS spectrograph at ESO’s La Silla Observatory in Chile have revealed unexpected changes in the bright spots on the dwarf planet Ceres. Although Ceres appears as little more than a point of light from the Earth, very careful study of its light shows not only the changes expected as Ceres rotates, but also that the spots brighten during the day and also show other variations. These observations suggest that the material of the spots is volatile and evaporates in the warm glow of sunlight.

Ceres is the largest body in the asteroid belt between Mars and Jupiter and the only such object classed as a dwarf planet. NASA’s Dawn spacecraft has been in orbit around Ceres for more than a year and has mapped its surface in great detail. One of the biggest surprises has been the discovery of very bright spots, which reflect far more light than their much darker surroundings. The most prominent of these spots lie inside the crater Occator and suggest that Ceres may be a much more active world than most of its asteroid neighbours.

New and very precise observations using the HARPS spectrograph at the ESO 3.6-metre telescope at La Silla, Chile, have now not only detected the motion of the spots due to the rotation of Ceres about its axis, but also found unexpected additional variations suggesting that the material of the spots is volatile and evaporates in sunlight. ...

Daily variability of Ceres’ albedo detected by means of radial velocities changes of the reflected sunlight - P. Molaro et al

• Monthly Notices of the RAS: Letters 458(1):L54 (2016 May 01) DOI: 10.1093/mnrasl/slw017
  arXiv.org > astro-ph > arXiv:1602.03467 > 10 Feb 2016

[bystander]

Bright Spots & Color Differences Revealed on Ceres
NASA | JPL-Caltech | 2016 Mar 22

Click to play embedded YouTube video.

GRaND Seeks Subsurface Water Ice on Ceres
Planetary Science Institute | 2016 Mar 22

[i]This map of neutron counting data at Ceres was acquired by Dawn's gamma ray and neutron detector (GRaND) instrument. The data comes from Dawn's low-altitude mapping orbit at Ceres, which is at a distance of 240 miles (385 kilometers) from the dwarf planet. The color scale of this map is from blue (lowest) to red (highest). This data, based on number of neutrons detected per second, reflects the concentration of hydrogen in the upper yard (meter) of regolith. Counts decrease with increasing hydrogen concentration. A portion of the northern hemisphere of Ceres is shown. The pole is marked with a white line. The longitude is centered on Occator Crater. Lower neutron counts near the pole suggest the presence of water ice within about a yard (meter) of the surface at high latitudes.[/i]

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[bystander]

New Ceres Images Show Bright Craters
NASA | JPL-Caltech | Dawn | 2016 Apr 19

Craters with bright material on dwarf planet Ceres shine in new images from NASA's Dawn mission.

In its lowest-altitude mapping orbit, at a distance of 240 miles (385 kilometers) from Ceres, Dawn has provided scientists with spectacular views of the dwarf planet.

[img3="Haulani Crater in Enhanced Color
Ceres' Haulani Crater, with a diameter of 21 miles (34 kilometers),
shows evidence of landslides from its crater rim."]http://www.jpl.nasa.gov/spaceimages/ima ... 358_ip.jpg[/img3][hr][/hr]

Haulani Crater, with a diameter of 21 miles (34 kilometers), shows evidence of landslides from its crater rim. Smooth material and a central ridge stand out on its floor. An enhanced false-color view allows scientists to gain insight into materials and how they relate to surface morphology. This image shows rays of bluish ejected material. The color blue in such views has been associated with young features on Ceres. ...

The crater's polygonal nature (meaning it resembles a shape made of straight lines) is noteworthy because most craters seen on other planetary bodies, including Earth, are nearly circular. The straight edges of some Cerean craters, including Haulani, result from pre-existing stress patterns and faults beneath the surface.

[img3="Oxo Crater at LAMO
Oxo Crater is unique because of the relatively large "slump" in its crater rim."]http://www.jpl.nasa.gov/spaceimages/ima ... 360_ip.jpg[/img3][hr][/hr]

A hidden treasure on Ceres is the 6-mile-wide (10-kilometer-wide) Oxo Crater, which is the second-brightest feature on Ceres (only Occator's central area is brighter). Oxo lies near the 0 degree meridian that defines the edge of many Ceres maps, making this small feature easy to overlook. Oxo is also unique because of the relatively large "slump" in its crater rim, where a mass of material has dropped below the surface. Dawn science team members are also examining the signatures of minerals on the crater floor, which appear different than elsewhere on Ceres. ...

Image Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI

[bystander]

Recent Hydrothermal Activity May Explain Ceres' Brightest Area
NASA | JPL-Caltech | Dawn | 2016 June 29

[img3="The center of Ceres' mysterious Occator Crater is the brightest area on the dwarf planet. The inset perspective view shows new data on this feature: Red signifies a high abundance of carbonates, while gray indicates a low carbonate abundance.
Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/ASI/INAF"]http://photojournal.jpl.nasa.gov/jpeg/PIA20694.jpg[/img3][hr][/hr]

The brightest area on Ceres, located in the mysterious Occator Crater, has the highest concentration of carbonate minerals ever seen outside Earth, according to a new study from scientists on NASA's Dawn mission. The study, published online in the journal Nature, is one of two new papers about the makeup of Ceres. ...

At about 80 million years old, Occator is considered a young crater. It is 57 miles (92 kilometers) wide, with a central pit about 6 miles (10 kilometers) wide. A dome structure at the center, covered in highly reflective material, has radial and concentric fractures on and around it.

De Sanctis' study finds that the dominant mineral of this bright area is sodium carbonate, a kind of salt found on Earth in hydrothermal environments. This material appears to have come from inside Ceres, because an impacting asteroid could not have delivered it. The upwelling of this material suggests that temperatures inside Ceres are warmer than previously believed. Impact of an asteroid on Ceres may have helped bring this material up from below, but researchers think an internal process played a role as well.

More intriguingly, the results suggest that liquid water may have existed beneath the surface of Ceres in recent geological time. The salts could be remnants of an ocean, or localized bodies of water, that reached the surface and then froze millions of years ago. ...

Bright Carbonate Deposits as Evidence of Aqueous Alteration on (1) Ceres - M. C. De Sanctis et al

• Nature (online 29 June 2016) DOI: 10.1038/nature18290

Composition and Structure of the Shallow Subsurface of Ceres Revealed by Crater Morphology - Michael T. Bland et al

• Nature Geoscience (online 29 June 2016) DOI: 10.1038/ngeo2743

[bystander]

Dawn Completes Primary Mission
NASA | JPL-Caltech | Dawn | 2016 June 30

[img3="NASA's Dawn mission exceeded all expectations during its primary mission to Vesta and Ceres. Credit: NASA/JPL-Caltech"]http://www.jpl.nasa.gov/infographics/up ... /11364.jpg[/img3][hr][/hr]

On June 30, just in time for the global celebration known as Asteroid Day, NASA's Dawn spacecraft completes its primary mission. The mission exceeded all expectations originally set for its exploration of protoplanet Vesta and dwarf planet Ceres.

The historic mission is the first to orbit two extraterrestrial solar system targets, and the first to orbit any object in the main asteroid belt, between Mars and Jupiter. On March 6, 2015, Dawn also became the first spacecraft to enter orbit around a dwarf planet.

An infographic highlights some of the accomplishments of Dawn's journey since launching in September 2007. Dawn has traveled 3.5 billion miles (5.6 billion kilometers) since launch, and has made 2,450 orbits around Vesta and Ceres. The spacecraft has returned about 69,000 images, combined, of both bodies.

Dawn's advanced ion propulsion system made it possible for the spacecraft to orbit two targets in the main asteroid belt. The spacecraft has logged about 48,000 hours of ion engine thrusting.

Scientists have learned a great deal about these unique, massive residents of the asteroid belt through data from the mission. Dawn has revealed that while Vesta is a dry body, Ceres could be as much as 25 percent water ice by mass. Dawn also discovered many intriguing features at both bodies -- Vesta is home to a mountain whose height is more than twice that of Mount Everest, and Ceres has a crater called Occator with mysterious bright features that continue to spark scientific investigation.

Dawn to Remain at Ceres

[bystander]

Dawn Maps Ceres Craters Where Ice Can Accumulate
NASA | JPL-Caltech | Dawn | AGU | 2016 July 08

Click to play embedded YouTube video.

Scientists with NASA's Dawn mission have identified permanently shadowed regions on the dwarf planet Ceres. Most of these areas likely have been cold enough to trap water ice for a billion years, suggesting that ice deposits could exist there now. ...

Permanently shadowed regions do not receive direct sunlight. They are typically located on the crater floor or along a section of the crater wall facing toward the pole. The regions still receive indirect sunlight, but if the temperature stays below about minus 240 degrees Fahrenheit (minus 151 degrees Celsius), the permanently shadowed area is a cold trap -- a good place for water ice to accumulate and remain stable. Cold traps were predicted for Ceres but had not been identified until now.

In this study, Schorghofer and colleagues studied Ceres' northern hemisphere, which was better illuminated than the south. Images from Dawn's cameras were combined to yield the dwarf planet's shape, showing craters, plains and other features in three dimensions. Using this input, a sophisticated computer model developed at NASA's Goddard Space Flight Center, Greenbelt, Maryland, was used to determine which areas receive direct sunlight, how much solar radiation reaches the surface, and how the conditions change over the course of a year on Ceres. ...

The Permanently Shadowed Regions of Dwarf Planet Ceres - Norbert Schorghofer et al

• Geophysical Research Letters (online 06 July 2016) DOI: 10.1002/2016GL069368

[bystander]

Puzzling Paucity of Large Craters on Dwarf Planet Ceres
Southwest Research Institute | 2016 July 26

[c][attachment=0]ceres-kerwan-crater.jpg[/attachment][/c][hr][/hr]

A team of scientists led by Southwest Research Institute (SwRI) made a puzzling observation while studying the size and distribution of craters on the dwarf planet Ceres.

Ceres is the largest object in the tumultuous Main Asteroid Belt between Mars and Jupiter. Collision models predicted Ceres should have accumulated up to 10 to 15 craters larger than 400 kilometers (250 miles) wide, and at least 40 craters larger than 100 km (62 miles) wide. Instead, NASA’s Dawn spacecraft found only 16 craters larger than 100 km, and none larger than the 280 km (175 miles) across.

Crater size and distribution offer planetary scientists important clues to the age, makeup, and geologic history of planets and asteroids. Ceres is believed to have originated about 4.5 billion years ago at the dawn of our solar system. It grew in size through a history of accretionary collisions of smaller bodies. Some of its largest siblings were subsequently incorporated into larger objects, such as planets. Today, Ceres and Main Belt asteroids remain as the leftovers of the planet-building process.

Although Ceres endured the most violent phase of the solar system’s collision-prone past, images of its surface taken by the Dawn spacecraft showed plenty of small impact craters, but the largest well-defined crater is only about 280-km in diameter. This defied most models of crater size and distribution and is at odds with what known from previously imaged asteroids. For example, Dawn images of the asteroid Vesta, only about half the size of Ceres, revealed huge craters, including one 500 kilometers (300 miles) in diameter, covering almost an entire side of that asteroid. ...

The Case of the Missing Craters
Arizona State University | 2016 July 26

The Case of the Missing Ceres Craters
NASA | JPL-Caltech | Dawn | 2016 July 26

Click to play embedded YouTube video.

The Missing Large Impact Craters on Ceres - Simone Marchi et al

• Nature Communications 7:12257 (26 July 2016) DOI: 10.1038/ncomms12257

[bystander]

What’s Inside Ceres? New Findings from Gravity Data
NASA | JPL-Caltech | Dawn | 2016 Aug 03

[img3="This artist's concept shows a diagram of how the inside of Ceres could be structured, based on data about the dwarf planet's gravity field from NASA's Dawn mission. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA"]http://www.jpl.nasa.gov/images/dawn/201 ... 867-16.jpg[/img3][hr][/hr]

› Full image and caption

In the tens of thousands of photos returned by NASA's Dawn spacecraft, the interior of Ceres isn't visible. But scientists have powerful data to study Ceres' inner structure: Dawn's own motion.

Since gravity dominates Dawn's orbit at Ceres, scientists can measure variations in Ceres' gravity by tracking subtle changes in the motion of the spacecraft. Using data from Dawn, scientists have mapped the variations in Ceres' gravity for the first time in a new study in the journal Nature, which provides clues to the dwarf planet's internal structure.

"The new data suggest that Ceres has a weak interior, and that water and other light materials partially separated from rock during a heating phase early in its history," said Ryan Park ...

A partially differentiated interior for (1) Ceres deduced from its gravity field and shape - R. S. Park et al

• Nature (online 03 Aug 2016) DOI: 10.1038/nature18955

[bystander]

Dawn Sets Course for Higher Orbit
NASA | JPL-Caltech | Dawn | 2016 Aug 31

[img3="This artist concept shows NASA's Dawn spacecraft above dwarf planet Ceres,
as seen in images from the mission. Credit: NASA/JPL-Caltech"]http://www.jpl.nasa.gov/spaceimages/ima ... _hires.jpg[/img3][hr][/hr]

After studying Ceres for more than eight months from its low-altitude science orbit, NASA's Dawn spacecraft will move higher up for different views of the dwarf planet.

Dawn has delivered a wealth of images and other data from its current perch at 240 miles (385 kilometers) above Ceres' surface, which is closer to the dwarf planet than the International Space Station is to Earth. Now, the mission team is pivoting to consider science questions that can be examined from higher up.

After Dawn completed its prime mission on June 30, having surpassed all of its scientific objectives at Vesta and at Ceres, NASA extended the mission to perform new studies of Ceres. One of the factors limiting Dawn's lifetime is the amount of hydrazine, the propellant needed to orient the spacecraft to observe Ceres and communicate with Earth. By going to a higher orbit at Ceres, Dawn will use the remaining hydrazine more sparingly, because it won't have to work as hard to counter Ceres' gravitational pull. ...

On Sept. 2, Dawn will begin spiraling upward to about 910 miles (1,460 kilometers) from Ceres. The altitude will be close to where Dawn was a year ago, but the orientation of the spacecraft's orbit -- specifically, the angle between the orbit plane and the sun -- will be different this time, so the spacecraft will have a different view of the surface. ...

[bystander]

Ceres' Geological Activity, Ice Revealed in New Research
NASA | JPL-Caltech | Dawn | 2016 Sep 01

[img3="Ahuna Mons: Ceres' lonely mountain, Ahuna Mons, is seen in this simulated perspective view. The elevation has been exaggerated by a factor of two. The view was made using enhanced-color images from NASA's Dawn mission.
Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI"]http://www.jpl.nasa.gov/spaceimages/ima ... _hires.jpg[/img3][hr][/hr]

A lonely 3-mile-high (5-kilometer-high) mountain on Ceres is likely volcanic in origin, and the dwarf planet may have a weak, temporary atmosphere. These are just two of many new insights about Ceres from NASA's Dawn mission published this week in six papers in the journal Science.

"Dawn has revealed that Ceres is a diverse world that clearly had geological activity in its recent past," said Chris Russell, principal investigator of the Dawn mission, based at the University of California, Los Angeles. ...

Ceres: The Tiny World Where Volcanoes Erupt Ice
Arizona State University | 2016 Sep 01

Ice Not a Major Factor of Ceres' Surface Features
Johns Hopkins University Applied Physics Laboratory | 2016 Sep 01

Dawn Arrives at Ceres: Exploration of a Small, Volatile-Rich World - C. T. Russell et al

• Science 353(6303):1008 (02 Sep 2016) DOI: 10.1126/science.aaf4219

Cratering on Ceres: Implications for Its Crust and Evolution - H. Hiesinger et al

• Science 353(6303):1003 (02 Sep 2016) DOI: 10.1126/science.aaf4759

The Geomorphology of Ceres - D. L. Buczkowski et al

• Science 353(6303):1004 (02 Sep 2016) DOI: 10.1126/science.aaf4332

Cryovolcanism on Ceres - O. Ruesch et al

• Science 353(6303):1005 (02 Sep 2016) DOI: 10.1126/science.aaf4286

Distribution of Phyllosilicates on the Surface of Ceres - E. Ammannito et al

• Science 353(6303):1006 (02 Sep 2016) DOI: 10.1126/science.aaf4279

Detection of Local H₂O Exposed at the Surface of Ceres - Jean-Philippe Combe et al

• Science 353(6303):1007 (02 Sep 2016) DOI: 10.1126/science.aaf3010

Sulfur, Sulfur Dioxide and Graphitized Carbon Observed on Asteroid For First Time
Planetary Science Institute | 2016 Sep 01

Ceres: Sulfur Deposits and Graphitized Carbon - Amanda Hendrix, Faith Vilas, Jian-Yang Li

• Geophysical Research Letters (online 31 Aug 2016) DOI: 10.1002/2016GL070240

[bystander]

New Ceres Views as Dawn Moves Higher
NASA | JPL-Caltech | Dawn | 2016 Nov 18

[img3="Occator Crater, home of Ceres' intriguing brightest areas,
is prominently featured in this image from NASA's Dawn spacecraft.
Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA"]http://photojournal.jpl.nasa.gov/jpeg/PIA21078.jpg[/img3]
[img3="This image approximates how the dwarf planet's colors would appear to the eye.
Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA"]http://photojournal.jpl.nasa.gov/jpeg/PIA21079.jpg[/img3][hr][/hr]

The brightest area on Ceres stands out amid shadowy, cratered terrain in a dramatic new view from NASA's Dawn spacecraft, taken as it looked off to the side of the dwarf planet. Dawn snapped this image on Oct. 16, from its fifth science orbit, in which the angle of the sun was different from that in previous orbits. Dawn was about 920 miles (1,480 kilometers) above Ceres when this image was taken -- an altitude the spacecraft had reached in early October.

Occator Crater, with its central bright region and secondary, less-reflective areas, appears quite prominent near the limb, or edge, of Ceres. At 57 miles (92 kilometers) wide and 2.5 miles (4 kilometers) deep, Occator displays evidence of recent geologic activity. The latest research suggests that the bright material in this crater is comprised of salts left behind after a briny liquid emerged from below, froze and then sublimated, meaning it turned from ice into vapor.

The impact that formed the crater millions of years ago unearthed material that blanketed the area outside the crater, and may have triggered the upwelling of salty liquid.

"This image captures the wonder of soaring above this fascinating, unique world that Dawn is the first to explore," said Marc Rayman, Dawn's chief engineer and mission director, based at NASA's Jet Propulsion Laboratory, Pasadena, California.

Dawn scientists also have released an image of Ceres that approximates how the dwarf planet's colors would appear to the human eye. This view, produced by the German Aerospace Center in Berlin, combines images taken from Dawn's first science orbit in 2015, using the framing camera's red, green and blue filters. The color was calculated based on the way Ceres reflects different wavelengths of light.

The spacecraft has gathered tens of thousands of images and other information from Ceres since arriving in orbit on March 6, 2015. After spending more than eight months studying Ceres at an altitude of about 240 miles (385 kilometers), closer than the International Space Station is to Earth, Dawn headed for a higher vantage point in August. In October, while the spacecraft was at its 920-mile altitude, it returned images and other valuable insights about Ceres.

On Nov. 4, Dawn began making its way to a sixth science orbit, which will be over 4,500 miles (7,200 kilometers) from Ceres. While Dawn needed to make several changes in its direction while spiraling between most previous orbits at Ceres, engineers have figured out a way for the spacecraft to arrive at this next orbit while the ion engine thrusts in the same direction that Dawn is already going. This uses less hydrazine and xenon fuel than Dawn's normal spiral maneuvers. Dawn should reach this next orbit in early December. ...

[bystander]

Where Is the Ice on Ceres? New Dawn Findings
NASA | JPL-Caltech | Dawn | 2016 Dec 15

[img3="Water Ice Abundance on Ceres and Vesta
Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI"]http://www.jpl.nasa.gov/spaceimages/ima ... _hires.jpg[/img3][hr][/hr]

At first glance, Ceres, the largest body in the main asteroid belt, may not look icy. Images from NASA's Dawn spacecraft have revealed a dark, heavily cratered world whose brightest area is made of highly reflective salts -- not ice. But newly published studies from Dawn scientists show two distinct lines of evidence for ice at or near the surface of the dwarf planet. Researchers are presenting these findings at the 2016 American Geophysical Union meeting in San Francisco.

"These studies support the idea that ice separated from rock early in Ceres' history, forming an ice-rich crustal layer, and that ice has remained near the surface over the history of the solar system," said Carol Raymond, deputy principal investigator of the Dawn mission, based at NASA's Jet Propulsion Laboratory, Pasadena, California.

Water ice on other planetary bodies is important because it is an essential ingredient for life as we know it. "By finding bodies that were water-rich in the distant past, we can discover clues as to where life may have existed in the early solar system," Raymond said. ...

Subsurface Water Shaped Dwarf Planet Ceres
Planetary Science Institute | 2016 Dec 15

Ice is Everywhere on the Dwarf Planet Ceres
Institute for Astronomy | University of Hawaii | 2016 Dec 15

Extensive water ice within Ceres’ aqueously altered regolith: Evidence from nuclear spectroscopy - T. H. Prettyman et al

• Science (online 15 Dec 2016) DOI: 10.1126/science.aah6765

Surface water-ice deposits in the northern shadowed regions of Ceres - T. Platz et al

• Nature Astronomy 1:0007 (15 Dec 2015) DOI: 10.1038/s41550-016-0007

[bystander]

New Research Shows Ceres May Have Vanishing Ice Volcanoes
American Geophysical Union | 2017 Feb 02

[img3="Ahuna Mons seen in a simulated perspective view. The elevation has been exaggerated by a factor of two. The view was made using enhanced-color images from NASA’s Dawn mission. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA"]http://photojournal.jpl.nasa.gov/jpeg/PIA20915.jpg[/img3][hr][/hr]

A recently discovered solitary ice volcano on the dwarf planet Ceres may have some hidden older siblings, say scientists who have tested a likely way such mountains of icy rock – called cryovolcanoes – might disappear over millions of years.

NASA’s Dawn spacecraft discovered Ceres’s 4-kilometer (2.5-mile) tall Ahuna Mons cryovolcano in 2015. Other icy worlds in our solar system, like Pluto, Europa, Triton, Charon and Titan, may also have cryovolcanoes, but Ahuna Mons is conspicuously alone on Ceres. The dwarf planet, with an orbit between Mars and Jupiter, also lies far closer to the sun than other planetary bodies where cryovolcanoes have been found.

Now, scientists show there may have been cryovolcanoes other than Ahuna Mons on Ceres millions or billions of years ago, but these cryovolcanoes may have flattened out over time and become indistinguishable from the planet’s surface. ...

The vanishing cryovolcanoes of Ceres - Michael M. Sori et al

• Geophysical Research Letters (online 24 Jan 2017) DOI: 10.1002/2016GL072319

[Ann]

Ah, poor ice volcano, I knew him!

Ann

[neufer]

[b][color=#FF0000][size=150]Weinbaum's '[i]Flight on Titan[/i]' was reprinted in 1950[/size] under the title of '[i]A Man, A Maid, and Saturn's Temptation[/i]'[/color][/b]

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[b][color=#0000FF]Doom Mons with collapse feature Sotra Patera and flow feature Mohini Fluctus, the latter partially covered by dunes. Radar image by Cassini, 2007[/color][/b]

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<<Doom Mons is the name of a mountain range and its eponymous peak on Titan, the largest moon of Saturn. A putative cryovolcano (i.e., ice volcano), it is the largest mountain range on Titan by volume.

Doom Mons is named after Mount Doom, a volcano that appears in J. R. R. Tolkien's fictional world of Middle-earth, most prominently in The Lord of the Rings. The name follows a convention by the IAU Working Group for Planetary System Nomenclature that Titanean mountains are named after mountains in Tolkien's works. Coincidentally, prior to the naming of Doom Mons, a fictional mountain range of Titan already existed that carried the name "Mount Doom"; this was a major setting in the 1935 science-fiction tale Flight on Titan by Stanley G. Weinbaum. Weinbaum's Mount Doom was populated by hostile native wildlife such as "Ice-Ants", "Whiplash Trees", pterodactyl-like "Knife-Kites", and the hypnosis-inducing "Giant Titanian Cave Threadworm". The climate of Weinbaum's mountain is described as sub-Arctic, and it is constantly battered by howling ice-needle storms and hurricane-force winds.

Many Titanean "mountains" are little more than hills. However, some of these mountains rise to some several hundreds of meters high. Doom Mons is currently believed to be possibly the largest Titanean mountain range and with the eponymous peak one of the highest; the title of highest peak on Titan is thought to be held by the Mithrim Montes, which may have been formed by global contraction. Doom Mons is believed to be a twin-peak that rises 1.45 km above the relatively flat surrounding plain, and a probable massive cryovolcano. It has a 500-600 m deep indentation on its western side, containing a circular pit that is another 400 m deep.

Doom Mons is constantly bombarded with wind, rain and snow composed of liquid methane and ethane, hydrocarbon dust and organic smog and tholin haze; the summit of Doom Mons, however, appears to be mostly clear and ice-capped with water ice. The superficial features of Doom Mons are constantly changing, a fact which may be exacerbated by a sub-surface, briny ocean. The permanent hurricane at the southern pole of Titan probably causes an issue of constant erosion on Doom Mons, preventing the mountain from growing taller. Doom Mons is believed to have a total width about 60 km. Robert Brown of the University of Arizona, one of the controllers of the Cassini-Huygens probe, gave the following description of Doom Mons at the December 2006 meeting of the American Geophysical Union in San Francisco, California:

"This mountain range is tall enough to produce streamers of clouds that extend far around the moon. You could call this the Titan Sierras. Several smaller ranges appear to be nearby, as does a circular feature that might be the crater from an ancient asteroid impact powerful enough to have punched through Titan's outer crust. I speculate that the mountains might be a chain of volcanoes that oozed up along cracks in the crust after the impact.">>