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frojack writes:

Just last week we talked about getting data back from Pluto from the New Horizons spacecraft.

Today NASA's "Dawn" spacecraft has returned the sharpest-ever photos of Ceres, just a month before its planned orbit around the mysterious dwarf planet.

On the night of March 5, Dawn will become the first spacecraft ever to orbit Ceres. Its the second solar system body (beyond Earth) that the Dawn space craft has orbited. (Dawn orbited the protoplanet Vesta, the asteroid belt's second-largest denizen, from July 2011 through September 2012.)

Space.com has a story and an animation built of multiple stills taken last Wednesday from 90,000 miles (145,000 kilometers) away from Ceres.

According to Dawn mission director and chief engineer Marc Rayman:

Its going to be an interesting couple months for space watchers.

martyb writes:

I found this wonderfully readable and informative story on The Conversation: After Eight Years, NASA's Dawn Probe Brings Dwarf Planet Ceres Into Closest Focus — and it was written by "the mission director and chief engineer on Dawn at JPL." (Nothing against journalists, but sometimes they don't quite understand what they are writing about — and I should know, as an Editor on SN, I've done that myself!)

More than a thousand times farther from Earth than the moon, farther even than the sun, an extraordinary extraterrestrial expedition is taking place. NASA's Dawn spacecraft is exploring dwarf planet Ceres, which orbits the sun between Mars and Jupiter. The probe has just reached the closest point it ever will, and is now beginning to collect its most detailed pictures and other measurements on this distant orb.

Ceres is a remnant from the dawn of our solar system nearly 4.6 billion years ago. All the data Dawn is now sending back will provide insight into Ceres' history and geology, including the presence of water, past or present. Scientists believe that by studying Ceres, we can unlock some of the secrets of the epoch in which planets, including our own, formed.

But this mission isn't only for scientists. Discovering the nature of an uncharted world is a thrill that can be shared by anyone who has ever gazed up at the night sky in wonder, been curious about the universe and Earth's place in it, or felt the lure of a bold adventure into the unknown.

I happen to fall into all those categories. I fell in love with space at the age of four, and I knew by the fourth grade that I wanted to earn a doctorate in physics. (It was a few more years before I did.) My passion for the exploration of space and the grandeur of scientific discovery and understanding has never wavered. It's a dream come true for me to be the mission director and chief engineer on Dawn at JPL.

Fun fact: Ceres has a diameter of about 600 miles (~ 1000 km) implying that its surface area, if laid flat, would cover a third of the continental USA. It will be a while before all of the data is accumulated and even longer for it to be downloaded and analyzed, so keep your eyes peeled for new revelations about Ceres.

I grew up in the age of Apollo and, like the story's author, am fascinated about astronomy. Not to the extent to make it my career, but I did take a few courses in college. The mind-boggling immensity of space, the incredible forces at play, the diversity of objects "out there" never cease to inspire curiosity and wonder in me.

I'm hoping there are Soylentils who share this fascination. Stories about space don't seem to get many comments, so I wonder how much interest there actually is in such stories. If you'd like to see more stories about space, please mention it in a comment.

Original Submission

takyon writes:

An unexpected mountain has been discovered on Ceres in images sent by NASA's Dawn orbiter:

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."

Original Submission

takyon writes:

The Dawn spacecraft has found evidence of magnesium sulphate (epsom salts) on Ceres, causing the mysterious bright spots:

The US space agency's Dawn satellite continues to return remarkable images from the dwarf planet Ceres. Now just 385km above the surface (lower than the space station is above Earth), the probe has revealed new features inside the mini-world's Occator Crater. This is the 92km-wide depression that has multiple bright spots of what are thought to be exposed salts.

[...] "The intricate geometry of the crater interior suggests geologic activity in the recent past, but we will need to complete detailed geologic mapping of the crater in order to test hypotheses for its formation." Scientists think the bright spots are deposits of epsom salts (magnesium sulphate), the trace remains of briny water-ice that at one time became exposed on the surface.

With no atmosphere on the dwarf planet, the water content would have rapidly vaporised, leaving only the magnesium sulphate spots. Ceres likely has quite a lot of buried water-ice. This idea is being investigated by the satellite's GRaND instrument, which senses neutrons and gamma rays produced by cosmic ray interactions with surface materials. It is a means to understand the chemistry of the top metre or so of Ceres' rocky "soil".

Lunar and Planetary Science Conference.

Original Submission

takyon writes:

A liquid ocean under the crust of Ceres, the largest object in the asteroid belt, may have led to the formation of its cryovolcano, Ahuna Mons:

Ahuna Mons is a giant mountain with a[n] icy volcanic dome, a so-called cryovolcano. All volcanic activity for cryovolcanoes happens at low temperatures; they spew icy magma which can consist of freezing water, ammonia or methane instead of hot bubbling lava. The lack of craters on the volcano's surface meant it was probably formed quite recently – a couple of hundred million years at most. Ottaviano Ruesch, lead author of the paper and a NASA scientist working on the Dawn mission, said: "This is the only known example of a cryovolcano that potentially formed from a salty mud mix, and which formed in the geologically recent past."

The possibility of cryovolcanism on Ceres has important implications. Not only does this confirm the dwarf planet's surface temperature of minus 40°C, but it also suggests that its interior has kept warm enough for a sea of salty liquid water to exist below the planet's surface for a relatively long time. "Ceres appears differentiated internally, with a core and a complex crust made of 30 to 40 per cent water ice mixed with silicate rock and salts," said Williams.

The geomorphology of Ceres (DOI: 10.1126/science.aaf4332) (DX)

Original Submission

takyon writes:

Scientists theorize that Ceres's cryovolcanoes slowly flatten over time:

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. They report their findings in a new paper accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.

[...] Ceres has no atmosphere, so the processes that wear down volcanoes on Earth – wind, rain and ice – aren't possible on the dwarf planet. Sori and his colleagues hypothesized that another process, called viscous relaxation, could be at work. Viscous relaxation is the idea that just about any solid will flow, given enough time. For example, a cold block of honey appears to be solid. But if given enough time, the block will flatten out until there is no sign left of the original block structure. On Earth, viscous relaxation is what makes glaciers flow, Sori explained. The process doesn't affect volcanoes on Earth because they are made of rock, but Ceres's volcanoes contain ice – making viscous relaxation possible. On Ceres, viscous relaxation could be causing older cryovolcanoes to flatten out over millions of years so they are hard to discern. Ceres's location close to the sun could make the process more pronounced, Sori said.

The vanishing cryovolcanoes of Ceres (open, DOI: 10.1002/2016GL072319) (DX)

Original Submission

takyon writes:

Scientists using imagery from the Dawn spacecraft have found evidence of organic material on the surface of the dwarf planet Ceres:

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.

[...] "This is the first clear detection of organic molecules from orbit on a main belt body," said Maria Cristina De Sanctis, lead author of the study, based at the National Institute of Astrophysics, Rome. The discovery is reported in the journal Science. 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.

[...] Having completed nearly two years of observations in orbit at Ceres, Dawn is now in a highly elliptical orbit at Ceres, going from an altitude of 4,670 miles (7,520 kilometers) up to almost 5,810 miles (9,350 kilometers). On Feb. 23, it will make its way to a new altitude of around 12,400 miles (20,000 kilometers), about the height of GPS satellites above Earth, and to a different orbital plane. This will put Dawn in a position to study Ceres in a new geometry. In late spring, Dawn will view Ceres with the sun directly behind the spacecraft, such that Ceres will appear brighter than before, and perhaps reveal more clues about its nature.

Localized aliphatic organic material on the surface of Ceres (DOI: 10.1126/science.aaj2305) (DX)

Original Submission

takyon writes:

Giant mud balls roamed the early solar system

The earliest asteroids were probably made of mud, not rock. Radioactive heat in the early solar system could have melted globs of dust and ice before they had a chance to turn to rock [open, DOI: 10.1126/sciadv.1602514] [DX], a new simulation published July 14 in Science Advances shows. The results could solve several puzzles about the composition of meteorites found on Earth and may explain why asteroids are different from comets.

[...] Bland reasoned that heat from radioactive decay would melt the ice, and the resulting body would be an enormous dollop of mud. The mud would suspend sediment particles, so they wouldn't be stripped of their sunlike elements. And it would allow the early asteroids to be any size and remain cool.

Bland and Bryan Travis of the Planetary Science Institute, who is based in Los Alamos, N.M., ran computer models of how the mud balls would evolve. Convection currents, like those that move molten rock within the Earth's mantle, would develop, helping to transfer heat into space, the models showed. After several million years, the ball would harden completely, yielding the asteroids seen today.

NASA will make a decision within the next two months on whether to extend the Dawn mission to another asteroid, leaving Ceres.

Original Submission

takyon writes:

The Dawn spacecraft will continue to orbit the dwarf planet Ceres, and will capture closer imagery than ever before:

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).

[...] 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.

The Dawn spacecraft will remain in orbit at Ceres, where it is expected to operate until late 2018, without being crashed into the surface or sent to another target.

Original Submission

takyon writes:

Dawn Finds Possible Ancient Ocean Remnants at Ceres

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.

"More and more, we are learning that Ceres is a complex, dynamic world that may have hosted a lot of liquid water in the past, and may still have some underground," said Julie Castillo-Rogez, Dawn project scientist and co-author of the studies, based at NASA's Jet Propulsion Laboratory, Pasadena, California.

Ceres.

Constraints on Ceres' internal structure and evolution from its shape and gravity measured by the Dawn spacecraft (open, DOI: 10.1002/2017JE005302) (DX)

The interior structure of Ceres as revealed by surface topography (DOI: 10.1016/j.epsl.2017.07.053) (DX)

Previously: Dawn Spies Magnesium Sulphate and Possible Geological Activity on Ceres
Ceres's Cryovolcanoes Viscously Relax Into Nothingness
Organic Molecules Found on Ceres
Early Asteroids May Have Been Made of Mud Rather Than Rock
Dawn Mission Extended at Ceres

Original Submission

takyon writes:

Bright Areas on Ceres Suggest Geologic Activity

Since Dawn arrived in orbit at Ceres in March 2015, scientists have located more than 300 bright areas on Ceres. A new study in the journal Icarus, led by Nathan Stein, a doctoral researcher at Caltech in Pasadena, California, divides Ceres' features into four categories.

The first group of bright spots contains the most reflective material on Ceres, which is found on crater floors. The most iconic examples are in Occator Crater, which hosts two prominent bright areas. Cerealia Facula, in the center of the crater, consists of bright material covering a 6-mile-wide (10-kilometer-wide) pit, within which sits a small dome. East of the center is a collection of slightly less reflective and more diffuse features called Vinalia Faculae. All the bright material in Occator Crater is made of salt-rich material, which was likely once mixed in water. Although Cerealia Facula is the brightest area on all of Ceres, it would resemble dirty snow to the human eye.

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 by the gradual accumulation of thick, slowly flowing icy materials, has prominent bright streaks on its flanks.

Ceres and cryovolcanos.

The formation and evolution of bright spots on Ceres (open, DOI: 10.1016/j.icarus.2017.10.014) (DX)

Previously: A Closer Look At Mystery Spots On Dwarf Planet Ceres
NASA's Dawn Orbiter Finds a Mountain on Ceres
Ceres's Cryovolcanoes Viscously Relax Into Nothingness
Organic Molecules Found on Ceres
Dawn Mission Extended at Ceres
Ceres May Have Had a Global Surface Ocean in the Past

Original Submission

takyon writes:

Previously, NASA planned to lower the closest approach to Ceres of the Dawn spacecraft to around 120 miles (200 km) from 239 miles (385 km). Now, the XMO7 orbit will reach an altitude of just 22 miles (35 km) above Ceres. The images returned should be over 9000 times better than what Hubble can capture. This is the final orbit planned:

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.

Previously: Dawn Mission Extended at Ceres

Related: Ceres May Have Had a Global Surface Ocean in the Past
Evidence of a Seasonal Water Cycle and Surface Changes Found on Ceres

Original Submission

takyon writes:

The Dawn spacecraft has entered its lowest-ever orbit around Ceres:

Dawn entered orbit around 1 Ceres on March 6, 2015. Up until this year, Dawn's orbits brought it no closer than 483 kilometers (300 miles) from the rock's surface. The complicated process of entering the new 27-hour, 13-minute orbit around the asteroid began on April 16th, when NASA engineers instructed Dawn to fire its ion engines. The new orbit has a periapsis of less than 48 km above the pockmarked surface of Ceres and an apoapsis of 4,000 km.

[...] Attaining a low orbit around Ceres object is no mean feat, as the asteroid's gravitational field is lumpy due to the asteroid's uneven composition. NASA engineers looked at over 45,000 possible trajectories before settling on the solution. A lower orbit will allow researchers to map Ceres's gravitational field and hence its internal mass distribution. Surprises may be in store, though: Dawn's reaction wheels failed earlier this year, so it now uses its hydrazine-fueled thrusters to control its orientation in space.

[...] We can enjoy the final closeups of Ceres before Dawn falls silent later this year. Then, the excitement in asteroid exploration will shift towards the arrival of the Japanese Aerospace Exploration Agency's Hayabusa-2 at 162173 Ryugu this July, as well as Osiris-REX's arrival at 101955 Bennu this August.

Check out Landslides Along Occator Crater's Rim and other recent images.

162173 Ryugu and 101955 Bennu.

Previously: Dawn Mission Extended at Ceres
Dawn's Orbit Around Ceres: A New Low

Related: Ceres May Have Had a Global Surface Ocean in the Past
Evidence of a Seasonal Water Cycle and Surface Changes Found on Ceres

Original Submission

takyon writes:

Dawn spacecraft captures new images of Ceres' Occator Crater

NASA's Dawn spacecraft has entered into its final planned orbital position from which it will study the dwarf planet Ceres, the lowest the probe has descended to the tiny world since it arrived in orbit on March 6, 2015.

The probe is powered by three xenon ion thrusters and it enter[ed] into its new orbit around the dwarf planet on June 6, 2018. Since then, the spacecraft has begun beaming back to Earth stunning new and closer images of this tiny worldlet.

One of Dawn's targets is Occator Crater. While the name might not ring a bell even among space enthusiasts, the "bright spots" contained within the crater should. These deposits are thought to be salt from briny water that erupted from the dwarf planet's surface before sublimating. It was found that the bright regions were comprised of sodium carbonate. On Earth, these salts are left behind when water evaporates.

Dawn was instructed to fire its ion engine—for what could be the last time—last week. By carrying out this maneuver, the probe flew closer to the dwarf planet's Cerealia Facula. This is the region of Occator Crater that contains a large deposit of sodium carbonate.

Perhaps more important than the cool photographs will be the data collected by the spacecraft's two other instruments, and particularly the Gamma Ray and Neutron Detector (GRaND).

Previously: Ceres Bright Spots Seen Closer Than Ever
Life On Ceres? Mysterious Changes in the Bright Spots Still Baffle Scientists
Bright Areas on Ceres Suggest Geologic Activity
Evidence of a Seasonal Water Cycle and Surface Changes Found on Ceres
Dawn's Orbit Around Ceres: A New Low
Dawn's Orbit Around Ceres: First Images

Original Submission

takyon writes:

Legacy of NASA's Dawn, Near the End of its Mission

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.

[...] Because Ceres has conditions of interest to scientists who study chemistry that leads to the development of life, NASA follows strict planetary protection protocols for the disposal of the Dawn spacecraft. Unlike Cassini, which deliberately plunged into Saturn's atmosphere to protect the system from contamination -- Dawn will remain in orbit around Ceres, which has no atmosphere.

Engineers designed Dawn's final orbit to ensure it will not crash for at least 20 years -- and likely decades longer.

Dawn, Vesta, and Ceres.

Previously: Dawn's Orbit Around Ceres: A New Low
Dawn Spacecraft Captures Closest-Ever Images of Ceres' Shiny Occator Crater

Original Submission

takyon writes:

NASA Retires Kepler Space Telescope

After nine years in deep space collecting data that indicate our sky to be filled with billions of hidden planets - more planets even than stars - NASA's Kepler space telescope has run out of fuel needed for further science operations. NASA has decided to retire the spacecraft within its current, safe orbit, away from Earth. Kepler leaves a legacy of more than 2,600 planet discoveries from outside our solar system, many of which could be promising places for life.

"As NASA's first planet-hunting mission, Kepler has wildly exceeded all our expectations and paved the way for our exploration and search for life in the solar system and beyond," said Thomas Zurbuchen, associate administrator of NASA's Science Mission Directorate in Washington. "Not only did it show us how many planets could be out there, it sparked an entirely new and robust field of research that has taken the science community by storm. Its discoveries have shed a new light on our place in the universe, and illuminated the tantalizing mysteries and possibilities among the stars."