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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:

NASA Dawn Reveals Recent Changes in Ceres' Surface

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.

[...] In a second study, VIR observations also reveal new information about the variability of Ceres' crust, and suggest recent surface changes, in the form of newly exposed material.

[...] This study, led by Giacomo Carrozzo of the Institute of Astrophysics and Planetary Science, identified 12 sites rich in sodium carbonates and examined in detail several areas of a few square miles that show where water is present as part of the carbonate structure. The study marks the first time hydrated carbonate has been found on the surface of Ceres, or any other planetary body besides Earth, giving us new information about the dwarf planet's chemical evolution.

Ceres.

Variations in the amount of water ice on Ceres' surface suggest a seasonal water cycle (open, DOI: 10.1126/sciadv.aao3757) (DX)

Nature, formation, and distribution of carbonates on Ceres (open, DOI: 10.1126/sciadv.1701645) (DX)

Previously: Ceres's Cryovolcanoes Viscously Relax Into Nothingness
Organic Molecules Found on Ceres
Ceres May Have Had a Global Surface Ocean in the Past
Bright Areas on Ceres Suggest Geologic Activity

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:

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:

NASA's Dawn Mission to Asteroid Belt Comes to End

NASA's Dawn spacecraft has gone silent, ending a historic mission that studied time capsules from the solar system's earliest chapter.

Dawn missed scheduled communications sessions with NASA's Deep Space Network on Wednesday, Oct. 31, and Thursday, Nov. 1. After the flight team eliminated other possible causes for the missed communications, mission managers concluded that the spacecraft finally ran out of hydrazine, the fuel that enables the spacecraft to control its pointing. Dawn can no longer keep its antennae trained on Earth to communicate with mission control or turn its solar panels to the Sun to recharge.

The Dawn spacecraft launched 11 years ago to visit the two largest objects in the main asteroid belt. Currently, it's in orbit around the dwarf planet Ceres, where it will remain for decades.

Ceres, Vesta, and Dawn.

Also at Ars Technica, The Verge, and Science News.

Previously: NASA's Dawn Spacecraft Nears the End of its Mission
NASA Retires the Kepler Space Telescope after It Runs Out of Hydrazine

Related:

*SPOILER* (click to show) *SPOILER* (click to hide)

Pluto and Ceres
After Eight Years, NASA's Dawn Probe Brings Dwarf Planet Ceres Into Closest Focus
NASA's Dawn Orbiter Finds a Mountain on Ceres
Dawn Spies Magnesium Sulphate and Possible Geological Activity on Ceres
Ceres' Cryovolcano Ahuna Mons Formed in the Geologically Recent Past
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
Ceres May Have Had a Global Surface Ocean in the Past
Bright Areas on Ceres Suggest Geologic Activity
Dawn's Orbit Around Ceres: A New Low
Dawn's Orbit Around Ceres: First Images
Dawn Spacecraft Captures Closest-Ever Images of Ceres' Shiny Occator Crater

Original Submission