NASA's Dawn mission has found evidence for organic material on Ceres, a dwarf planet and the largest body in the main asteroid belt between Mars and Jupiter. Scientists using the spacecraft's visible and infrared mapping spectrometer (VIR) detected the material in and around a northern-hemisphere crater called Ernutet. Organic molecules are interesting to scientists because they are necessary, though not sufficient, components of life on Earth.
The discovery adds to the growing list of bodies in the solar system where organics have been found. Organic compounds have been found in certain meteorites as well as inferred from telescopic observations of several asteroids. Ceres shares many commonalities with meteorites rich in water and organics -- in particular, a meteorite group called carbonaceous chondrites. This discovery further strengthens the connection between Ceres, these meteorites and their parent bodies. ...
Data presented in the Science paper support the idea that the organic materials are native to Ceres. The carbonates and clays previously identified on Ceres provide evidence for chemical activity in the presence of water and heat. This raises the possibility that the organics were similarly processed in a warm water-rich environment. ...
Dawn spacecraft data suggest organic materials are native to the dwarf planet
SwRI scientists are studying the geology associated with the organic-rich
areas on Ceres. Dawn spacecraft data show a region around the Ernutet
crater where organic concentrations have been discovered (“a” through “f”).
The color coding shows the strength of the organics absorption band, with
warmer colors indicating the highest concentrations. Credit: NASA/JPL-Caltech/UCLA/ASI/INAF/MPS/DLR/IDA
NASA’s Dawn spacecraft recently detected organic-rich areas on Ceres. Scientists evaluated the geology of the regions to conclude that the organics are most likely native to the dwarf planet. Data from the spacecraft suggest that the interior of Ceres is the source of these organic materials, as opposed to arriving via impacting asteroids or comets ...
Ceres is believed to have originated about 4.5 billion years ago at the dawn of our solar system. Studying its organics can help explain the origin, evolution, and distribution of organic species across the solar system. Data from Dawn’s visible and infrared mapping spectrometer show an unusually high concentration of organic matter close to the 50-km diameter Ernutet crater in the northern hemisphere of Ceres. The distribution and characteristics of the organics seem to preclude association with any single crater. The largest concentration appears to drape discontinuously across the southwest floor and rim of Ernutet and onto an older, highly degraded crater. Other organic-rich areas are scattered to the northwest. While other scientists looked at the distribution and spectra of the materials, Marchi focused on the geological settings. ...
Localized aliphatic organic material on the surface of Ceres - M. C. De Sanctis et al
<<In ancient Roman religion, Ceres) was a goddess of agriculture, grain crops, fertility and motherly relationships. She was originally the central deity in Rome's so-called plebeian or Aventine Triad, then was paired with her daughter Proserpina in what Romans described as "the Greek rites of Ceres". Her seven-day April festival of Cerealia included the popular Ludi Ceriales (Ceres' games). She was also honoured in the May lustratio of the fields at the Ambarvalia festival, at harvest-time, and during Roman marriages and funeral rites.>>
Among the most striking features on the surface of Ceres are the bright spots in the center of Occator crater which stood out already as NASA’s space probe Dawn approached the dwarf planet. Scientists under the leadership of the Max Planck Institute for Solar System Research (MPS) have now for the first time determined the age of this bright material, which consists mainly of deposits of special mineral salts. With about four million years only, these deposits are about 30 million years younger than the crater itself. This, as well as the distribution and nature of the bright material within the crater, suggests that Occator crater has been the scene of eruptive outbursts of subsurface brine over a long period and until almost recently. Ceres is thus the body closest to the Sun that shows cryovolcanic activity.
For nearly two years, the NASA’s space probe Dawn has been accompanying dwarf planet Ceres, which orbits the Sun within the asteroid belt between Mars and Jupiter. During the first part of the mission, the probe advanced to lower and lower orbits until between December 2015 and September 2016 only approximately 375 kilometers separated it from the surface. During this so-called Low Altitude Mapping Orbit the Dawn Framing Cameras produced highly resolved images of Ceres’ surface displaying a resolution of 35 meters per pixel. The Dawn Framing Cameras, Dawn’s scientific imaging system, were developed and built and are operated under the leadership of the MPS.
MPS researchers have now thoroughly investigated the complex geological structures that are shown in the detailed images of Occator crater. These structures include fractures, avalanches, and younger, smaller craters. "In these data, the origin and evolution of the crater as it presents itself today can be read more clearly than ever before”, says Andreas Nathues, Framing Camera Lead Investigator. Additional indications were provided by measurements of the infrared spectrometer VIR onboard Dawn. ...
Evolution of Occator Crater on (1) Ceres - A. Nathues et al
The bright central area of Ceres' Occator Crater, known as Cerealia Facula, is approximately 30 million years younger than the crater in which it lies, according to a new study in the Astronomical Journal. Scientists used data from NASA's Dawn spacecraft to analyze Occator's central dome in detail, concluding that this intriguing bright feature on the dwarf planet is only about 4 million years old -- quite recent in terms of geological history. ...
The new study supports earlier interpretations from the Dawn team that this reflective material -- comprising the brightest area on all of Ceres -- is made of carbonate salts, although it did not confirm a particular type of carbonate previously identified. The secondary, smaller bright areas of Occator, called Vinalia Faculae, are comprised of a mixture of carbonates and dark material, the study authors wrote.
New evidence also suggests that Occator's bright dome likely rose in a process that took place over a long period of time, rather than forming in a single event. They believe the initial trigger was the impact that dug out the crater itself, causing briny liquid to rise closer to the surface. Water and dissolved gases, such as carbon dioxide and methane, came up and created a vent system. These rising gases also could have forced carbonate-rich materials to ascend toward the surface. During this period, the bright material would have erupted through fractures, eventually forming the dome that we see today. ...
Ice in Ceres' Shadowed Craters Linked to Tilt History
Posted: Wed Mar 22, 2017 5:15 pm
by bystander
Ice in Ceres' Shadowed Craters Linked to Tilt History NASA | JPL-Caltech | Dawn | 2017 Mar 22
Dwarf planet Ceres may be hundreds of millions of miles from Jupiter, and even farther from Saturn, but the tremendous influence of gravity from these gas giants has an appreciable effect on Ceres' orientation. In a new study, researchers from NASA's Dawn mission calculate that the axial tilt of Ceres -- the angle at which it spins as it journeys around the sun -- varies widely over the course of about 24,500 years. Astronomers consider this to be a surprisingly short period of time for such dramatic deviations.
Changes in axial tilt, or "obliquity," over the history of Ceres are related to the larger question of where frozen water can be found on Ceres' surface, scientists report in the journal Geophysical Research Letters. Given conditions on Ceres, ice would only be able to survive at extremely cold temperatures -- for example, in areas that never see the sun. ...
Ceres's obliquity history and its implications for the permanently shadowed regions - A.I. Ermakov et al
JPL: Ceres' Temporary Atmosphere Linked to Solar Activity
Posted: Thu Apr 06, 2017 7:20 pm
by bystander
Ceres' Temporary Atmosphere Linked to Solar Activity NASA | JPL-Caltech | Dawn | 2017 Apr 06
NASA's Dawn spacecraft determined the hydrogen content of the upper yard,
or meter, of Ceres' surface. Blue indicates where hydrogen content is higher,
near the poles, while red indicates lower content at lower latitudes. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI
Scientists have long thought that Ceres may have a very weak, transient atmosphere, but mysteries lingered about its origin and why it's not always present. Now, researchers suggest that this temporary atmosphere appears to be related to the behavior of the sun, rather than Ceres' proximity to the sun. The study was conducted by scientists from NASA's Dawn mission and others who previously identified water vapor at Ceres using other observatories. ...
Ceres is the largest object in the asteroid belt that lies between Mars and Jupiter. When energetic particles from the sun hit exposed ice and ice near the surface of the dwarf planet, it transfers energy to the water molecules as they collide. This frees the water molecules from the ground, allowing them to escape and create a tenuous atmosphere that may last for a week or so. ...
Before Dawn arrived in orbit at Ceres in 2015, evidence for an atmosphere had been detected by some observatories at certain times, but not others, suggesting that it is a transient phenomenon. ...
The Dependence of the Cerean Exosphere on Solar Energetic Particle Events - M. N. Villarreal et al
Type II features are the most common of Ceres’ landslides and look similar to deposits
left by avalanches on Earth. This one also looks similar to TV's Bart Simpson. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, taken by Dawn Framing Camera
Massive landslides, similar to those found on Earth, are occurring on the asteroid Ceres. That’s according to a new study led by the Georgia Institute of Technology, adding to the growing evidence that Ceres retains a significant amount of water ice.
The study is published in the journal Nature Geoscience. It used data from NASA’s Dawn spacecraft to identify three different types of landslides, or flow features, on the Texas-sized asteroid.
Type I are relatively round, large and have thick "toes" at their ends. They look similar to rock glaciers and icy landslides in Earth’s arctic. Type I landslides are mostly found at high latitudes, which is also where the most ice is thought to reside near Ceres' surface.
Type II features are the most common of Ceres’ landslides and look similar to deposits left by avalanches on Earth. They are thinner and longer than Type I and found at mid-latitudes. The authors affectionately call one such Type II landslide "Bart" because of its resemblance to the elongated head of Bart Simpson from TV's "The Simpsons."
Ceres' Type III features appear to form when some of the ice is melted during impact events. These landslides at low latitudes are always found coming from large-impact craters. ...
Landslides on Ceres Reflect Ice Content NASA | JPL-Caltech | Dawn | 2017 Apr 19
Geomorphological Evidence for Ground Ice on Dwarf Planet Ceres - Britney E. Schmidt et al
Re: GA Tech: Landslides on Ceres Reflect Hidden Ice
Posted: Wed Apr 19, 2017 4:38 pm
by neufer
Type II features are the most common of Ceres’ landslides and look similar to deposits
left by avalanches on Earth. This one also looks similar to TV's Bart Simpson. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, taken by Dawn Framing Camera
One can still see Homer's fingerprints on Bart's neck from years ago.
Why you little!
.
Dawn: Movie Shows Ceres at Opposition from Sun
Posted: Tue May 16, 2017 5:24 pm
by bystander
Movie Shows Ceres at Opposition from Sun NASA | JPL-Caltech | Dawn | 2017 May 16
NASA's Dawn spacecraft successfully observed Ceres at opposition on April 29, taking images from a position exactly between the sun and Ceres’ surface. Mission specialists had carefully maneuvered Dawn into a special orbit so that the spacecraft could view Occator Crater, which contains the brightest area of Ceres, from this new perspective.
A new movie shows these opposition images, with contrast enhanced to highlight brightness differences. The bright spots of Occator stand out particularly well on an otherwise relatively bland surface. Dawn took these images from an altitude of about 12,000 miles (20,000 kilometers).
Based on data from ground-based telescopes and spacecraft that previously viewed planetary bodies at opposition, scientists correctly predicted that Ceres would appear brighter from this opposition configuration. This increase in brightness, or "surge," relates the size of the grains of material on the surface, as well as the porosity of those materials. ...
Dawn Mission Celebrates 10 Years in Space
Posted: Wed Sep 27, 2017 9:47 pm
by bystander
Dawn Mission Celebrates 10 Years in Space NASA | JPL-Caltech | Dawn | 2017 Sep 27
Click to play embedded YouTube video.
Fly Over Ceres with the Dawn Spacecraft (360 video) Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Ten years ago, NASA's Dawn spacecraft set sail for the two most massive bodies in the asteroid belt between Mars and Jupiter: giant asteroid Vesta and dwarf planet Ceres. The mission was designed to deliver new knowledge about these small but intricate worlds, which hold clues to the formation of planets in our solar system. ...
Since its launch on Sept. 27, 2007, Dawn has achieved numerous technical and scientific feats while traveling 4 billion miles (6 billion kilometers). It is the only spacecraft to orbit two extraterrestrial solar system targets. It is also the only spacecraft to orbit a dwarf planet, a milestone it achieved when in entered orbit around Ceres on March 6, 2015. The spacecraft's ion propulsion system enabled Dawn to study each of these worlds from a variety of vantage points and altitudes, creating an impressive scrapbook of 88,000 photos. Additionally, Dawn's suite of instruments enabled it to take a variety of other measurements of Vesta and Ceres, revealing the contrasting compositions and internal structures of these two bodies. ...
NASA has authorized a second extension of the Dawn mission at Ceres, the largest object in the asteroid belt between Mars and Jupiter. During this extension, the spacecraft will descend to lower altitudes than ever before at the dwarf planet, which it has been orbiting since March 2015. The spacecraft will continue at Ceres for the remainder of its science investigation and will remain in a stable orbit indefinitely after its hydrazine fuel runs out.
The Dawn flight team is studying ways to maneuver Dawn into a new elliptical orbit, which may take the spacecraft to less than 120 miles (200 kilometers) from the surface of Ceres at closest approach. Previously, Dawn's lowest altitude was 240 miles (385 kilometers).
A priority of the second Ceres mission extension is collecting data with Dawn's gamma ray and neutron spectrometer, which measures the number and energy of gamma rays and neutrons. This information is important for understanding the composition of Ceres' uppermost layer and how much ice it contains.
The spacecraft also will take visible-light images of Ceres' surface geology with its camera, as well as measurements of Ceres' mineralogy with its visible and infrared mapping spectrometer.
The extended mission at Ceres additionally allows Dawn to be in orbit while the dwarf planet goes through perihelion, its closest approach to the Sun, which will occur in April 2018. At closer proximity to the Sun, more ice on Ceres' surface may turn to water vapor, which may in turn contribute to the weak transient atmosphere detected by the European Space Agency's Herschel Space Observatory before Dawn's arrival. Building on Dawn's findings, the team has hypothesized that water vapor may be produced in part from energetic particles from the Sun interacting with ice in Ceres' shallow surface.Scientists will combine data from ground-based observatories with Dawn's observations to further study these phenomena as Ceres approaches perihelion. ...
Re: Dawn Mission Extended at Ceres
Posted: Sat Oct 21, 2017 4:35 pm
by neufer
bystander wrote:Dawn Mission Extended at Ceres NASA | JPL-Caltech | Dawn | 2017 Oct 19
The extended mission at Ceres additionally allows Dawn to be in orbit while the dwarf planet goes through perihelion, its closest approach to the Sun, which will occur in April 2018. At closer proximity to the Sun, more ice on Ceres' surface may turn to water vapor, which may in turn contribute to the weak transient atmosphere detected by the European Space Agency's Herschel Space Observatory before Dawn's arrival. Building on Dawn's findings, the team has hypothesized that water vapor may be produced in part from energetic particles from the Sun interacting with ice in Ceres' shallow surface.Scientists will combine data from ground-based observatories with Dawn's observations to further study these phenomena as Ceres approaches perihelion. ...
https://en.wikipedia.org/wiki/Ceres_(dwarf_planet) wrote:
<<Ceres [obliquity/Axial tilt ~4°]follows an orbit between Mars and Jupiter, within the asteroid belt, with a period of 4.6 Earth years. The orbit is moderately inclined (i = 10.6° compared to 7° for Mercury and 17° for Pluto) and moderately eccentric (e = 0.08 compared to 0.09 for Mars). When Ceres has an opposition near the [2.5577 AU : Max surface temperature ~ -38° C] perihelion, it can reach a visual magnitude of +6.7. This is generally regarded as too dim to be seen with the naked eye, but under exceptional viewing conditions a very sharp-sighted person may be able to see it. The only other asteroids that can reach a similarly bright magnitude are 4 Vesta, and, during rare oppositions near perihelion, 2 Pallas and 7 Iris. It can thus be seen with binoculars whenever it is above the horizon of a fully dark sky.
Dawn Finds Possible Ancient Ocean Remnants at Ceres
Posted: Thu Oct 26, 2017 5:21 pm
by bystander
Dawn Finds Possible Ancient Ocean Remnants at Ceres NASA | JPL-Caltech | Dawn | 2017 Oct 26
This animation shows dwarf planet Ceres as seen by NASA's Dawn. The map overlaid at right gives scientists hints about Ceres' internal structure from gravity measurements. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Minerals containing water are widespread on Ceres, suggesting the dwarf planet may have had a global ocean in the past. What became of that ocean? Could Ceres still have liquid today? Two new studies from NASA's Dawn mission shed light on these questions.
The Dawn team found that Ceres' crust is a mixture of ice, salts and hydrated materials that were subjected to past and possibly recent geologic activity, and that this crust represents most of that ancient ocean. The second study builds off the first and suggests there is a softer, easily deformable layer beneath Ceres' rigid surface crust, which could be the signature of residual liquid left over from the ocean, too. ...
The first of the two studies ... used shape and gravity data measurements from the Dawn mission to determine the internal structure and composition of Ceres. The measurements came from observing the spacecraft's motions with NASA's Deep Space Network to track small changes in the spacecraft's orbit. ...
The second study ... investigated the strength and composition of Ceres' crust and deeper interior by studying the dwarf planet's topography. ...
Constraints on Ceres’ Internal Structure and Evolution from
Its Shape and Gravity Measured by the Dawn Spacecraft - A. I. Ermakov et al
Journal of Geophysical Research - Planets (accepted 18 Oct 2017) DOI: 10.1002/2017JE005302
The Interior Structure of Ceres as Revealed by Surface Topography - Roger R. Fu et al
This image made with data from NASA's Dawn spacecraft shows
pit chains on dwarf planet Ceres called Samhain Catenae. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Surface features on Ceres -- the largest world between Mars and Jupiter -- and its interior evolution have a closer relationship than one might think.
A recent study, published in Geophysical Research Letters, analyzed Ceres' surface features to reveal clues about the dwarf planet's interior evolution. Specifically, the study explored linear features -- the chains of pits and small, secondary craters common on Ceres.
The findings align with the idea that, hundreds of millions (up to a billion) years ago, materials beneath Ceres' surface pushed upward toward the exterior, creating fractures in the crust.
"As this material moved upward from underneath Ceres' surface, portions of Ceres' outer layer were pulled apart, forming the fractures," said Jennifer Scully, lead study author and associate of the Dawn science team at NASA's Jet Propulsion Laboratory in Pasadena, California.
The indication of upwelling material under Ceres' surface allows for another perspective in establishing how the dwarf planet may have evolved. ...
Evidence for the Interior Evolution of Ceres from Geologic Analysis of Fractures - J. E. C. Scully et al
Geophysical Research Letters 44(19):9564 (16 Oct 2017) DOI: 10.1002/2017GL075086
<<The brightest cluster of spots ("Spot 5") is located in an 80-kilometer crater called Occator, which is located at 19.86° N latitude; 238.85 E longitude. The spot in the center of the crater is named Cerealia Facula, and the group of spots to the east - Vinalia Faculae.
Alan Duffy of Swinburne University suggested "a meteorite strike either shook covering material off the salty ice or heated it so that salty water rose to the surface as a geyser. The water escaped into space and now, only the salt remains." A haze that fills around half of Occator crater and that does not extend over its rim periodically appears around Spot 5, the best known bright spot, adding credence to the idea that some sort of outgassing or volcanism is occurring.
An informal NASA poll during May offered the following ideas for the nature of the spots: ice, volcanos, geysers, salt deposits, rock, or other. Asteroid specialist A. Rivkin noted, in an article by Sky & Telescope magazine, that at low angles a haze can be seen in but not outside of the crater, and speculated that this could be sublimated vapor from ice, possibly linked to the bright spots. Reflectivity studies from September 2015 suggest that the spots are probably salts rather than ice, implying that Ceres's interior is somehow delivering fresh salt to the surface.>>
Salt Glacier,
Zagros Mountains
Earth Observatory,
November 13, 2017
<<The scale and form of many impressive features on Earth’s surface can only be fully appreciated through an overhead view. The astronauts onboard the International Space Station may enjoy the best overhead view of all.
The Zagros Mountains of southeastern Iran are the location of numerous salt domes and salt glaciers, formed as a result of the depositional history and tectonic forces operating in the region. While many of these landscape features are named on maps, the salt glacier in this photograph remains unnamed on global maps and atlases.
The vaguely hourglass (or bowtie) shaped morphology of the salt glacier is due to the central location of the salt dome, which formed within the central Zagros ridge crest (top and lower left). Salt extruded from the dome and then flowed downslope into the adjacent valleys. For a sense of scale, the distance across the salt glacier from northwest to southeast is approximately 14 kilometers.
Much like what happens in flowing ice glaciers, concentric transverse ridges have formed in the salt perpendicular to the flow direction. While bright salt materials are visible in stream beds incising the salt glacier, older surfaces—those farther from the central salt dome—appear dark, most likely due to windblown dust deposition over time or entrainment of sediments in the salt during flow.>>
Bright Areas on Ceres Suggest Geologic Activity
Posted: Wed Dec 13, 2017 5:55 pm
by bystander
Bright Areas on Ceres Suggest Geologic Activity NASA | JPL-Caltech | Dawn | 2017 Dec 12
If you could fly aboard NASA's Dawn spacecraft, the surface of dwarf planet Ceres would generally look quite dark, but with notable exceptions. These exceptions are the hundreds of bright areas that stand out in images Dawn has returned. Now, scientists have a better sense of how these reflective areas formed and changed over time -- processes indicative of an active, evolving world. ...
The first group of bright spots contains the most reflective material on Ceres, which is found on crater floors. ...
More commonly, in the second category, bright material is found on the rims of craters, streaking down toward the floors. Impacting bodies likely exposed bright material that was already in the subsurface or had formed in a previous impact event.
Separately, in the third category, bright material can be found in the material ejected when craters were formed.
The mountain Ahuna Mons gets its own fourth category -- the one instance on Ceres where bright material is unaffiliated with any impact crater. This likely cryovolcano, a volcano formed bythe gradual accumulation of thick, slowly flowing icy materials, has prominent bright streaks on its flanks. ...
The Formation and Evolution of Bright Spots on Ceres - N. T. Stein et al
Observations of Ceres have detected recent variations in its surface, revealing that the only dwarf planet in the inner solar system is a dynamic body that continues to evolve and change.
NASA’s Dawn mission has found recently exposed deposits that give us new information on the materials in the crust and how they are changing, according to two papers published March 14 in Science Advances that document the new findings.
Observations obtained by the visible and infrared mapping spectrometer (VIR) on the Dawn spacecraft previously found water ice in a dozen sites on Ceres. The new study revealed the abundance of ice on the northern wall of Juling Crater, a crater 12 miles (20 kilometers) in diameter. The new observations, conducted from April through October 2016, show an increase in the amount of ice on the crater wall.
“This is the first direct detection of change on the surface of Ceres,” said Andrea Raponi of the Institute of Astrophysics and Planetary Science in Rome.
Raponi led the new study, which found changes in the amount of ice exposed on the dwarf planet. “The combination of Ceres moving closer to the Sun in its orbit, along with seasonal change, triggers the release of water vapor from the subsurface, which then condenses on the cold crater wall. This causes an increase in the amount of exposed ice. The warming might also cause landslides on the crater walls that expose fresh ice patches.” ...
Variations in the Amount of Water Ice on Ceres’ Surface Suggest a Seasonal Water Cycle - Andrea Raponi et al
NASA’s Dawn spacecraft is maneuvering to its lowest-ever orbit for a close-up examination of the inner solar system’s only dwarf planet.
In early June, Dawn will reach its new, final orbit above Ceres. Soon after, it will begin collecting images and other science data from an unprecedented vantage point. This orbit will be less than 30 miles (50 kilometers) above the surface of Ceres -- 10 times closer than the spacecraft has ever been.
Dawn will collect gamma ray and neutron spectra, which help scientists understand variations in the chemical makeup of Ceres’ uppermost layer. That very low orbit also will garner some of Dawn’s closest images yet.
The transfer from Dawn’s previous orbit to its final one is not as simple as making a lane change. Dawn’s operations team worked for months to plot the course for this second extended mission of the veteran spacecraft, which is propelled by an ion engine. Engineers mapped out more than 45,000 possible trajectories before devising a plan that will allow the best science observations. ...
Re: Dawn Mission: New Orbit, New Opportunities
Posted: Sat Jun 02, 2018 5:34 pm
by neufer
bystander wrote: ↑Sat Jun 02, 2018 2:47 pmDawn Mission: New Orbit, New Opportunities NASA | JPL-Caltech | Dawn | 2018 May 31
In early June, Dawn will reach its new, final orbit above Ceres. Soon after, it will begin collecting images and other science data from an unprecedented vantage point. This orbit will be less than 50 kilometers above the surface of Ceres -- 10 times closer than the spacecraft has ever been. Dawn will collect gamma ray and neutron spectra, which help scientists understand variations in the chemical makeup of Ceres’ uppermost layer. That very low orbit also will garner some of Dawn’s closest images yet.
https://en.wikipedia.org/wiki/GRAIL wrote:
<<The Gravity Recovery and Interior Laboratory (GRAIL) was an American lunar science mission in NASA's Discovery Program which used high-quality gravitational field mapping of the Moon to determine its interior structure. [With a periselene of just 25 kilometres] the two spacecraft were able to detect very small changes in the distance between one another. Changes in distance as small as one micron were detectable and measurable. By measuring the change in distance between the two spacecraft, the gravity field and geological structure of the Moon was obtained.>>
https://en.wikipedia.org/wiki/GRAIL wrote:
<<MESSENGER (whose backronym is "MErcury Surface, Space ENvironment, GEochemistry, and Ranging", and which is a reference to the messenger of the same name from Roman mythology) was a NASA robotic spacecraft that orbited the planet Mercury between 2011 and 2015. MESSENGER's orbit was highly elliptical, taking it within 200 kilometers of Mercury's surface and then 15,000 km away from it every twelve hours. This orbit was chosen to shield the probe from the heat radiated by Mercury's hot surface. Only a small portion of each orbit was at a low altitude, where the spacecraft was subjected to radiative heating from the hot side of the planet.>>
Dawn: Dramatic New Views of Occator Crater
Posted: Tue Jul 03, 2018 4:22 am
by bystander
Dawn’s Latest Orbit Reveals Dramatic New Views of Occator Crater NASA | JPL-Caltech | Dawn | 2018 Jul 02
NASA's Dawn spacecraft reached its lowest-ever and final orbit around dwarf planet Ceres on June 6 and has been returning thousands of stunning images and other data.
The flight team maneuvered the spacecraft into an orbit that dives 22 miles (35 kilometers) above the surface of Ceres and viewed Occator Crater, site of the famous bright deposits, and other intriguing regions. In more than three years of orbiting Ceres, Dawn's lowest altitude before this month was 240 miles (385 kilometers), so the data from this current orbit bring the dwarf planet into much sharper focus.
These low orbits have revealed unprecedented details of the relationships between bright and dark materials in the region of Vinalia Faculae. Dawn's visible and infrared mapping spectrometer had previously found the bright deposits to be made of sodium carbonate, a material commonly found in evaporite deposits on Earth. Last week Dawn fired its ion engine, possibly for the final time, to fly nearer Cerealia Facula, the large deposit of sodium carbonate in the center of Occator Crater. ...
The wealth of information contained in these images, and more that are planned in the coming weeks, will help address key, open questions about the origin of the faculae, the largest deposits of carbonates observed thus far outside Earth, and possibly Mars. In particular, scientists have been wondering how that material was exposed, either from a shallow, sub-surface reservoir of mineral-laden water, or from a deeper source of brines (liquid water enriched in salts) percolating upward through fractures. ...
https://en.wikipedia.org/wiki/Ceres_(dwarf_planet) wrote:
<<On 9 December 2015, NASA scientists reported that the bright spots on Ceres may be related to a type of salt, particularly a form of brine containing magnesium sulfate hexahydrite (MgSO4·6H2O); the spots were also found to be associated with ammonia-rich clays. In June 2016, near-infrared spectra of these bright areas were found to be consistent with a large amount of sodium carbonate (Na2CO3), implying that recent geologic activity was probably involved in the creation of the bright spots.>>
Sodium carbonate, Na2CO3, (also known as washing soda, soda ash and soda crystals, and in the monohydrate form as crystal carbonate) is the water-soluble sodium salt of carbonic acid. Pure sodium carbonate is a white, odorless powder that is hygroscopic (absorbs moisture from the air). It has a strongly alkaline taste, and forms a moderately basic solution in water. Sodium carbonate is well known domestically for its everyday use as a water softener. Historically it was extracted from the ashes of plants growing in sodium-rich soils, such as vegetation from the Middle East, kelp from Scotland and seaweed from Spain. Because the ashes of these sodium-rich plants were noticeably different from ashes of timber (used to create potash), they became known as "soda ash". It is synthetically produced in large quantities from salt (sodium chloride) and limestone by a method known as the Solvay process.
The manufacture of glass is one of the most important uses of sodium carbonate. Sodium carbonate acts as a flux for silica, lowering the melting point of the mixture to something achievable without special materials. This "soda glass" is mildly water-soluble, so some calcium carbonate is added to the melt mixture to make the glass produced insoluble. This type of glass is known as soda lime glass: "soda" for the sodium carbonate and "lime" for the calcium carbonate. Soda lime glass has been the most common form of glass for centuries.
Sodium carbonate is also used as a relatively strong base in various settings. For example, it is used as a pH regulator to maintain stable alkaline conditions necessary for the action of the majority of photographic film developing agents. It acts as an alkali because when dissolved in water, it dissociates into the weak acid: carbonic acid and the strong alkali: sodium hydroxide. This gives sodium carbonate in solution the ability to attack metals such as aluminium with the release of hydrogen gas.
It is a common additive in swimming pools used to raise the pH which can be lowered by chlorine tablets and other additives which contain acids. In cooking, it is sometimes used in place of sodium hydroxide for lyeing, especially with German pretzels and lye rolls. These dishes are treated with a solution of an alkaline substance to change the pH of the surface of the food and improve browning. In taxidermy, sodium carbonate added to boiling water will remove flesh from the bones of animal carcasses for trophy mounting or educational display.>>
Dusk for Dawn: Mission to Gather More Data in Home Stretch
Posted: Tue Jul 17, 2018 3:10 pm
by bystander
Dusk for Dawn: Mission of Many Firsts
to Gather More Data in Home Stretch NASA | JPL-Caltech | Dawn | 2018 Jul 16
As NASA's Dawn spacecraft prepares to wrap up its groundbreaking 11-year mission, which has included two successful extended missions at Ceres, it will continue to explore -- collecting images and other data.
Within a few months, Dawn is expected to run out of a key fuel, hydrazine, which feeds thrusters that control its orientation and keeps it communicating with Earth. When that happens, sometime between August and October, the spacecraft will stop operating, but it will remain in orbit around dwarf planet Ceres. ...
Although the Dawn mission is winding down, the science is not. Besides the high-resolution images, the spacecraft is collecting gamma ray and neutron spectra, infrared and visible spectra, and gravity data. The observations focus on the area around Occator and Urvara craters, with the main goal of understanding the evolution of Ceres, and testing for possible ongoing geology. ...
Re: Dusk for Dawn: Mission to Gather More Data in Home Stretch
Posted: Tue Jul 17, 2018 3:28 pm
by neufer
"Ashes to crashes, Dawn to dust"
Legacy of Dawn, Near the End of Mission
Posted: Fri Sep 07, 2018 10:06 pm
by bystander
The Legacy of NASA's Dawn, Near the End of Its Mission NASA | JPL-Caltech | Dawn | 2018 Sep 07
Revealing Solar System Time Capsules, Breaking Engineering Barriers
NASA's Dawn mission is drawing to a close after 11 years of breaking new ground in planetary science, gathering breathtaking imagery, and performing unprecedented feats of spacecraft engineering.
Dawn's mission was extended several times, outperforming scientists' expectations in its exploration of two planet-like bodies, Ceres and Vesta, that make up 45 percent of the mass of the main asteroid belt. Now the spacecraft is about to run out of a key fuel, hydrazine. When that happens, most likely between mid-September and mid-October, Dawn will lose its ability to communicate with Earth. It will remain in a silent orbit around Ceres for decades.
"Although it will be sad to see Dawn's departure from our mission family, we are intensely proud of its many accomplishments," said Lori Glaze, acting director of the Planetary Science Division at NASA Headquarters in Washington. "Not only did this spacecraft unlock scientific secrets at these two small but significant worlds, it was also the first spacecraft to visit and orbit bodies at two extraterrestrial destinations during its mission. Dawn's science and engineering achievements will echo throughout history." ...
Icy volcanoes have erupted throughout the history of Ceres, but such continuous activity has not had the same extensive impact on the dwarf planet’s surface as standard volcanism on Earth, says a new paper ... Cryovolcanoes erupt liquid or gaseous volatiles such as water, ammonia or methane instead of spewing molten rock like seen on Earth. Salty water is likely the major component of cryolavas on Ceres. ...
Ceres, around which NASA’s Dawn spacecraft continues to orbit, offers the best opportunity to test the significance of cryovolcanism on outer space system bodies, compared to regular volcanism on terrestrial planets like Earth. ...
Finite Element Method models were used to analyze images from Dawn to show Ceres has experienced cryovolcanism throughout its geologic history, with an average surface extrusion rate of about 10,000 cubic meters per year, orders of magnitude lower than that of basaltic volcanism on the terrestrial planets. ...
