Cosmic Space

Slush on Ceres widens hopes for water worlds

Even before NASA’s Dawn probe mapped Ceres in detail in 2015, scientists suspected that the dwarf planet was a water world. Now they’ve traced Ceres’ upwellings of salty slush and mud to reservoirs deep beneath the surface.

The details came out this week in a package of papers published by Nature Astronomy, Nature Geoscience and Nature Communications. The findings serve as a fitting coda to an 11-year mission that almost didn’t happen, but ultimately succeeded in solving many of the mysteries surrounding Ceres as well as its sister asteroid Vesta.

For example, consider the bright spots in Ceres’ Occator Crater, which some have likened to “alien headlights.” The reflectivity is due to a crust of sodium carbonate, a salt left behind by the evaporation of briny water that percolated up to the surface.

Gravity readings gathered during the latter days of Dawn’s mission led scientists to conclude that the brine came from a reservoir that’s 25 miles deep and hundreds of miles wide.

In one of the bright spots, known as Cerealia Facula, Dawn’s instruments detected a concentration of hydrated salt compounds. The fact that those compounds are still hydrated suggest that they must have reached the surface relatively recently — perhaps within the past few centuries. That suggests that the transfer of liquid material from Ceres’ deep reservoir is continuing.

“For the large deposit at Cerealia Facula, the bulk of the salts were supplied from a slushy area just beneath the surface that was melted by the heat of the impact that formed the crater about 20 million years ago,” Dawn principal investigator, Carol Raymond, explained in a news release. “The impact heat subsided after a few million years; however, the impact also created large fractures that could reach the deep, long-lived reservoir, allowing brine to continue percolating to the surface.”

Dawn’s scientists saw additional evidence for Ceres’ active, slush-based geology in the presence of conical hills reminiscent of earthly features known as pingos. On Earth, pingos are formed when pressurized groundwater freezes beneath the surface and pushes up the soil above. Similar geological structures have been observed on Mars.

On icy moons such as Europa, Enceladus and Titan, geological activity is primarily driven by gravitational interactions with their parent planets. The fact that Ceres is geologically active, even though its crust is not being flexed by a nearby planet, widens the possibilities for finding slush or liquid water deep within ice-rich worlds in the main asteroid belt, the Kuiper Belt and elsewhere.

The data-gathering phase of Dawn’s mission ended in 2018, and the dead spacecraft is now silently circling Ceres. But decades or centuries from now, the scientific findings resulting from the mission just might guide explorers to new kinds of interplanetary watering holes.


Dawn probe falls silent, ending mission to Ceres

Dawn's view of Ceres
This photo of Ceres and the bright regions in Occator Crater was one of the last views NASA’s Dawn spacecraft transmitted before it completed its mission. This view, which faces south, was captured on Sept. 1 from an altitude of 2,340 miles as the spacecraft was ascending in its elliptical orbit. (NASA / JPL-Caltech / UCLA / MPS / DLR / IDA Photo)

Dawn is dead, but Dawn is not gone: Today NASA said that the Dawn spacecraft has fallen out of contact with Earth, presumably because it’s run out of the thruster fuel that was used to keep its antennas oriented toward Earth and its power-generating solar panels oriented toward the sun.

After Dawn missed out on communications sessions on Wednesday and today, NASA declared an end to the mission.

During its 11 years in space, Dawn sent back unprecedented closeups of the asteroid Vesta as well as Ceres, which is the largest known asteroid and the smallest confirmed dwarf planet.

Dawn will continue circling Ceres for decades to come in the main asteroid belt, 257 million miles out from the sun.

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Dawn probe snaps close-ups of Ceres’ white spots

Ceres' white spots
A mosaic of images from NASA’s Dawn spacecraft shows a prominent mound of bright material on the western side of Cerealia Facula on dwarf planet Ceres. (NASA / JPL-Caltech / UCLA / MPS / DLR / IDA Photo)

The once-mysterious bright spots shining on the surface of the dwarf planet Ceres are getting their closest close-ups from NASA’s Dawn spacecraft, adding to the strangest sights of the solar system.

This week, NASA released a mosaic of images captured on June 22 from a height of 22 miles, showing mounds of the white stuff at the center of Occator Crater. Dawn’s current close-up orbit will serve as the last act of a scientific saga that began with its launch more than a decade ago and featured visits to Ceres and Vesta, the two biggest objects in the main asteroid belt.

Ceres’ white spots shone brightly with reflected sunlight in the pictures that Dawn took from millions of miles away, leading some to dub them “alien headlights.” For a time, Dawn’s scientists puzzled over what they were made of. But the probe’s spectral readings confirmed that the material in the bright spots consisted primarily of sodium carbonate.

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Water, water everywhere on dwarf planet Ceres

Hydrogen on Ceres
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. (NASA / JPL-Caltech / UCLA / MPS / DLR / IDA / PSI Photo)

Readings from instruments aboard NASA’s Dawn orbiter support the view that a treasure trove of frozen water lies just beneath the surface of the dwarf planet Ceres.

Researchers reported those findings today at the American Geophysical Union’s fall meeting San Francisco, as well as in two papers published by Nature Astronomy and Science.

The findings are based on hydrogen readings from Dawn’s gamma ray and neutron detector, or GRaND, as well as from the spacecraft’s cameras and infrared mapping spectrometer.

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Dawn probe points to ice volcano on Ceres

Image: Ceres' 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. (Credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA / PSI)

Scientists say a mysterious mountain on the dwarf planet Ceres was apparently once an ice volcano, spewing salty water and mud instead of lava.

They also say Ceres has patches of water ice that can be seen on or near the surface, and might have an off-and-on atmosphere that contains water vapor.

The scientists say all this and more in six research papers published in this week’s issue of the journal Science. The studies are based on more than a year’s worth of orbital observations from NASA’s Dawn spacecraft. Dawn is still circling 590-mile-wide Ceres, which is the solar system’s smallest dwarf planet as well as its biggest main-belt asteroid.

The mysterious mountain is Ahuna Mons, a 3-mile-high peak that looks like a bright space pyramid. Scientists took note of the peak’s concave top, its elliptical base, cracks at the summit, steep slopes and other features that pointed to previous volcanic activity.

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New Horizons mission extended to Kuiper Belt

Image: New Horizons
Artwork shows New Horizons flying by a Kuiper Belt object known as 2014 MU69. (Credit: NASA)

Almost a year after New Horizons’ unprecedented flyby of Pluto, NASA has given the official go-ahead for the probe to fly past another icy object in the Kuiper Belt in 2019.

At the same time, the space agency decided to keep the Dawn spacecraft in orbit around the dwarf planet Ceres, rather than sending it out to another asteroid known as Adeona.

The decisions are part of NASA’s process for extending its planetary missions into the 2017-2018 time frame.

New Horizons’ extension means that mission operations will be supported as the piano-sized probe makes its way toward a Kuiper Belt object called 2014 MU69. The object was detected in 2014 during a Hubble Space Telescope search for post-Pluto targets that could be reached by New Horizons. The mission team already has been maneuvering the spacecraft in preparation for a flyby on Jan. 1, 2019.

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Ceres’ mystery spots get their close-up

Image: Occator Crater
The bright central spots near the center of Occator Crater are shown in enhanced color in this view from NASA’s Dawn spacecraft. Such views can be used to highlight subtle color differences on Ceres’ surface. The view combines high-resolution images of Occator from February with lower-resolution color data from September. (Credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA / PSI / LPI)

The scientists behind NASA’s Dawn mission today showed off their latest, greatest pictures of the dwarf planet Ceres, including close-up views of curious bright spots on the surface.

The car-sized Dawn spacecraft has been circling Ceres, the biggest mini-world in the solar system’s asteroid belt, for just more than a year. In Dawn’s distant views, the bright spots looked like alien headlights. The latest images, captured from a height of just 240 miles, reveal that the brightest spot is a fractured dome sticking up from 57-mile-wide Occator Crater.

Other bright areas appear to be highly reflective deposits, crisscrossed by linear features and fractures.

Dawn’s scientists discussed their latest data today at the Lunar and Planetary Science Conference in The Woodlands, Texas.

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Dawn sheds more light on Ceres’ bright spots

Image: Kupalo Crater on Ceres
This image of Ceres’ Kupalo Crater was captured by NASA’s Dawn spacecraft from a height of about 240 miles on Dec. 21. (Credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA)

For years, scientists puzzled over the bright spots that shine like alien headlights from the surface of Ceres, a dwarf planet in the main asteroid belt. Scientists are leaning toward identifying them as salt deposits, and now there’s a new line of evidence that could help tell the tale definitively.

The evidence takes the form of bright deposits in Kupalo Crater, one of the freshest craters spotted on Ceres. In this case, just a little bit of bright material can be seen on on the crater’s floor. But lots of the stuff is tumbling down from the crater’s rim.

The material shows up clearly in an image captured by NASA’s Dawn spacecraft. Dawn has been circling Ceres since last March, but last month it descended to a 240-mile orbit for up-close imaging. The newly released picture of Kupalo Crater was taken Dec. 21.

“This crater and its recently formed deposits will be a prime target of study for the team as Dawn continues to explore Ceres in its final mapping phase,” Paul Schenk, a Dawn science team member at the Lunar and Planetary Institute in Houston, said Tuesday in a NASA news release.

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See Ceres as you’ve never seen it before

Image: Ceres
This Dec. 10 image of Ceres shows the area around a crater chain called Gerber Catena,. NASA’s Dawn spacecraft was flying about 240 miles above Ceres when the picture was taken. (Credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA).

Earlier this month we started seeing some of the closest views yet of Pluto, and now it’s time for close-ups from a closer dwarf planet: Ceres.

NASA’s Dawn orbiter has begun delivering pictures of the solar system’s biggest asteroid and smallest known dwarf planet as seen from its closest vantage point, just 240 miles (385 kilometers) above the surface. That’s roughly how high the International Space Station flies above Earth.

One of the more intriguing views released today shows the area around a crater chain called Gerber Catena. Get out your red-blue glasses, and you can easily spot a trough running through a 3-D view of the terrain.

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Those weird spots on Ceres? Probably water ice

Image: Ceres' Occator Crater
This color-coded representation of Ceres’ Occator Crater shows differences in surface composition, highlight bright patches inside the crater. (Credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA)

For months, scientists have puzzled over weirdly bright spots of material shining on the asteroid Ceres, but now they say the spots are probably made of salty ice.

That determination, based on a detailed analysis of spectral data from NASA’s Dawn orbiter, comes in a paper published today by the journal Nature. Dawn’s images highlight one particular patch in a 106-mile-wide impact basin known as Occator Crater, but other spots are spread across the surface of the 590-mile-wide dwarf planet.

“The global nature of Ceres’ bright spots suggests that this world has a subsurface layer that contains briny water-ice,” the study’s principal author, Andreas Nathues of the Max Planck Institute for Solar System Research, said in a NASA statement. He and his co-authors suggest that cosmic impacts dig up enough surface material to expose the shiny ice.

Get updates on Ceres, alien megastructures and Japan’s Venus probe on GeekWire.