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posted by martyb on Sunday July 08 2018, @10:05AM   Printer-friendly
from the Theme-Music-by-Tony-Orlando dept.

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


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Ceres Bright Spots Seen Closer Than Ever 10 comments

JPL has published an even closer look at the bright spots on Ceres.

Apart from a closer look, there isn't much new information. While looking at the picture though, I was having trouble with the perspective on the craters. If I invert/negative the image, the spots are of course black, but the craters look like craters. What gives?

"Dawn scientists can now conclude that the intense brightness of these spots is due to the reflection of sunlight by highly reflective material on the surface, possibly ice," Christopher Russell, principal investigator for the Dawn mission from the University of California, Los Angeles, said recently.

Dawn is currently about 7,200 km from the surface of Ceres. On December 8th, it will be 375 km from the surface.

Life On Ceres? Mysterious Changes in the Bright Spots Still Baffle Scientists 13 comments

Bright spots on the dwarf planet Ceres continue to puzzle researchers. When recently a team of astronomers led by Paolo Molaro of the Trieste Astronomical Observatory in Italy, conducted observations of these features, they found out something unexpected. The scientists were surprised to detect that the spots brighten during the day and also show other variations. This variability still remains a mystery.

The bright features have been discovered by NASA's Dawn spacecraft which is orbiting this dwarf planet, constantly delivering substantial information about it. These spots reflect far more light than their much darker surroundings. The composition of these features is discussed as the scientists debate if they are made of water ice, of evaporated salts, or something else.

Molaro and his colleagues studied the spots on Ceres in July and August 2015, using the High Accuracy Radial velocity Planet Searcher (HARPS), as was reported by the European Southern Observatory (ESO) earlier this year. This instrument, mounted on ESO's 3.6m telescope at La Silla Observatory in Chile, enables measurements of radial velocities with the highest accuracy currently available.

By utilizing HARPS, the researchers found out unexpected changes in the mysterious bright spots. However, at the beginning they thought that it was an instrumental problem. But after double checking, they had to conclude that the radial velocity anomalies were likely real. Then the team noticed that they were connected to periods of time when the bright spots in the Occator crater were visible from the Earth. So the scientists made an association between them.


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Bright Areas on Ceres Suggest Geologic Activity 8 comments

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

Evidence of a Seasonal Water Cycle and Surface Changes Found on Ceres 4 comments

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

Dawn's Orbit Around Ceres: A New Low 9 comments

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

Dawn's Orbit Around Ceres: First Images 3 comments

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

NASA's Dawn Spacecraft Nears the End of its Mission 6 comments

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

Dawn Spacecraft Runs Out of Hydrazine, Ceases Operations 13 comments

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

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