Ceres Rolled Over at Some Point in the Past

In 2007, the Dawn mission launched from Earth and began making its way towards two historic rendezvous in the Main Asteroid Belt. The purpose of this mission was to learn more about the history of the early Solar System by studying the two largest protoplanets in the Main Belt – Ceres and Vesta – which have remained intact since their formation.

In 2015, the Dawn mission arrived in orbit around Ceres and began sending back data that has shed light on the protoplanet’s surface, composition and interior structure. Based on mission data, Pasquale Tricarico – the senior scientist at the Planetary Science Institute (PSI) – has also determined that the Ceres also experienced an indirect polar reorientation in the past, where its pole rolled approximately 36° off-axis.

Continue reading “Ceres Rolled Over at Some Point in the Past”

Ice Volcanoes on Ceres are Still Actively Blasting out Material

The 4 km high ice volcano Ahuna Mons (top) is visible projecting above the cratered surface of the dwarf planet Ceres. Image: By NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

In science, one discovery often leads to more questions and mysteries. That’s certainly true of the ice volcanoes on the dwarf planet Ceres. When the Dawn spacecraft discovered the massive cryovolcano called Ahuna Mons on the surface of Ceres, it led to more questions: How cryovolcanically active is Ceres? And, why do we only see one?

Continue reading “Ice Volcanoes on Ceres are Still Actively Blasting out Material”

Ceres Has Even More Organic Molecules on it Than Previously Thought

In March of 2015, NASA’s Dawn mission became the first spacecraft to visit the protoplanet Ceres, the largest body in the Main Asteroid Belt. It was also the first spacecraft to visit a dwarf planet, having arrived a few months before the New Horizons mission made its historic flyby of Pluto. Since that time, Dawn has revealed much about Ceres, which in turn is helping scientists to understand the early history of the Solar System.

Last year, scientists with NASA’s Dawn mission made a startling discovery when they detected complex chains of carbon molecules – organic material essential for life – in patches on the surface of Ceres. And now, thanks to a new study conducted by a team of researchers from Brown University (with the support of NASA), it appears that these patches contain more organic material than previously thought.

The new findings were recently published in the scientific journal Geophysical Research Letters under the title “New Constraints on the Abundance and Composition of Organic Matter on Ceres“. The study was led by Hannah Kaplan, a postdoctoral researcher at Brown University, with the assistance of Ralph E. Milliken and Conel M. O’D. Alexander – an assistant professor at Brown University and a researcher from the Carnegie Institution of Washington, respectively.

A new analysis of Dawn mission data suggests those organics could be more plentiful than originally thought. Credit: NASA/Rendering by Hannah Kaplan

The organic materials in question are known as “aliphatics”, a type of compound where carbon atoms form open chains that are commonly bound with oxygen, nitrogen, sulfur and chlorine. To be fair, the presence of organic material on Ceres does not mean that the body supports life since such molecules can arise from non-biological processes.

Aliphatics have also been detected on other planets in the form of methane (on Mars and especially on Saturn’s largest moon, Titan). Nevertheless, such molecules remains an essential building block for life and their presence at Ceres raises the question of how they got there. As such, scientists are interested in how it and other life-essential elements (like water) has been distributed throughout the Solar System.

Since Ceres is abundant in both organic molecules and water, it raises some intriguing possibilities about the protoplanet. The results of this study and the methods they used could also provide a template for interpreting data for future missions. As Dr. Kaplan – who led the research while completing her PhD at Brown – explained in a recent Brown University press release:

“What this paper shows is that you can get really different results depending upon the type of organic material you  use to compare with and interpret the Ceres data. That’s important not only for Ceres, but also for missions that will soon explore asteroids that may also contain organic material.”

Enhanced color-composite image, made with data from the framing camera aboard NASA’s Dawn spacecraft, shows the area around Ernutet crater. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

The original discovery of organics on Ceres took place in 2017 when an international team of scientists analyzed data from the Dawn mission’s Visible and Infrared Mapping Spectrometer (VIRMS). The data provided by this instrument indicated the presence of these hydrocarbons in a 1000 km² region around of the Ernutet crater, which is located in the northern hemisphere of Ceres and measures about 52 km (32 mi) in diameter.

To get an idea of how abundant the organic compounds were, the original research team compared the VIRMS data to spectra obtained in a laboratory from Earth rocks with traces of organic material. From this, they concluded that between 6 and 10% of the spectral signature detected on Ceres could be explained by organic matter.

They also hypothesized that the molecules were endogenous in origin, meaning that they originated from inside the protoplanet. This was consistent with previous surveys that showed signs of hydorthermal activity on Ceres, as well others that have detected ammonia-bearing hydrated minerals, water ice, carbonates, and salts – all of which suggested that Ceres had an interior environment that can support prebiotic chemistry.

But for the sake of their study, Kaplan and her colleagues re-examined the data using a different standard. Instead of relying on Earth rocks for comparison, they decided to examine an extraterrestrial source. In the past, some meteorites – such as carbonaceous chondrites – have been shown to contain organic material that is slightly different than what we are familiar with here on Earth.

Artist’s rendition of the Dawn mission on approach to the protoplanet Ceres. Credit: NASA/JPL

After re-examining the spectral data using this standard, Kaplan and her team determined that the organics found on Ceres were distinct from their terrestrial counterparts. As Kaplan explained:

“What we find is that if we model the Ceres data using extraterrestrial organics, which may be a more appropriate analog than those found on Earth, then we need a lot more organic matter on Ceres to explain the strength of the spectral absorption that we see there. We estimate that as much as 40 to 50 percent of the spectral signal we see on Ceres is explained by organics. That’s a huge difference compared to the six to 10 percent previously reported based on terrestrial organic compounds.”

If the concentrations of organic material are indeed that high, then it raises new questions about where it came from. Whereas the original discovery team claimed it was endogenous in origin, this new study suggests that it was likely delivered by an organic-rich comet or asteroid. On the one hand, the high concentrations on the surface of Ceres are more consistent with a comet impact.

This is due to the fact that comets are known to have significantly higher internal abundances of organics compared with primitive asteroids, similar to the 40% to 50% figure this study suggests for these locations on Ceres. However, much of those organics would have been destroyed due to the heat of the impact, which leaves the question of how they got there something of a mystery.

Dawn spacecraft data show a region around the Ernutet crater where organic concentrations have been discovered (labeled “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

If they did arise endogenously, then there is the question of how such high concentrations emerged in the northern hemisphere. As Ralph Milliken explained:

“If the organics are made on Ceres, then you likely still need a mechanism to concentrate it in these specific locations or at least to preserve it in these spots. It’s not clear what that mechanism might be. Ceres is clearly a fascinating object, and understanding the story and origin of organics in these spots and elsewhere on Ceres will likely require future missions that can analyze or return samples.”

Given that the Main Asteroid Belt is composed of material left over from the formation of the Solar System, determining where these organics came from is expected to shed light on how organic molecules were distributed throughout the Solar System early in its history. In the meantime, the researchers hope that this study will inform upcoming sample missions to near-Earth asteroids (NEAs), which are also thought to host water-bearing minerals and organic compounds.

These include the Japanese spacecraft Hayabusa2, which is expected to arrive at the asteroid Ryugu in several weeks’ time, and NASA’s OSIRIS-REx mission – which is due to reach the asteroid Bennu in August. Dr. Kaplan is currently a science team member with the OSIRIS-REx mission and hopes that the Dawn study she led will help the OSIRIS-REx‘s mission characterize Bennu’s environment.

“I think the work that went into this study, which included new laboratory measurements of important components of primitive meteorites, can provide a framework of how to better interpret data of asteroids and make links between spacecraft observations and samples in our meteorite collection,” she said. “As a new member to the OSIRIS-REx team, I’m particularly interested in how this might apply to our mission.”

The New Horizons mission is also expected to rendezvous with the Kuiper Belt Object (KBO) 2014 MU69 on January 1st, 2019. Between these and other studies of “ancient objects” in our Solar System – not to mention interstellar asteroids that are being detected for the first time – the history of the Solar System (and the emergence of life itself) is slowly becoming more clear.

Further Reading: Brown University, Geophysical Research Letters

Wow! Asteroid/Dwarf Planet Ceres Once had an Ocean?

In March of 2015, NASA’s Dawn mission arrived around Ceres, a protoplanet that is the largest object in the Asteroid Belt. Along with Vesta, the Dawn mission seeks to characterize the conditions and processes of the early Solar System by studying some of its oldest objects. One thing Dawn has determined since its arrival is that water-bearing minerals are widespread on Ceres, an indication that the protoplanet once had a global ocean.

Naturally, this has raised many questions, such as what happened to this ocean, and could Ceres still have water today? Towards this end, the Dawn mission team recently conducted two studies that shed some light on these questions. Whereas the former used gravity measurements to characterize the interior of the protoplanet, the latter sought to determine its interior structure by studying its topography.

The first study, titled “Constraints on Ceres’ internal structure and evolution from its shape and gravity measured by the Dawn spacecraft“, was recently published in the Journal of Geophysical Research. Led by Anton Ermakov, a postdoctoral researcher at JPL, the team also consisted of researchers from the NASA’s Goddard Space Flight Center, the German Aerospace Center, Columbia University, UCLA and MIT.

Ceres. as imaged by the NASA Dawn probe. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Together, the team relied on gravity measurements of the protoplanet, which the Dawn probe has been collecting since it established orbit around Ceres. Using the Deep Space Network to track small changes in the spacecraft’s orbit, Ermakov and his colleagues were able to conduct shape and gravity data measurements of Ceres to determine the internal structure and composition.

What they found was that Ceres shows signs of being geologically active; if not today, than certainly in the recent past. This is indicated by the presence of three craters – Occator, Kerwan and Yalode – and Ceres’ single tall mountain, Ahuna Mons. All of these are associated with “gravity anomalies”, which refers to discrepancies between the way scientists have modeled Ceres’ gravity and what Dawn observed in these four locations.

The team concluded that these four features and other outstanding geological formations, are therefore indications of cryovolcanism or subsurface structures. What’s more, they determined that the crust’s density was relatively low, being closer to that of ice than solid rock.  This, however, was inconsistent with a previous study performed by Dawn guest investigator Michael Bland of the U.S. Geological Survey.

Bland’s study, which was published in Nature Geoscience back in 2016, indicated that ice is not likely to be the dominant component of Ceres strong crust, on a count of it being too soft. Naturally, this raises the question of how the crust could be light as ice in terms of density, but also much stronger. To answer this, the second team attempted to model how Ceres’ surface evolved over time.

Gravity measurements of Ceres, which provided  hints about its internal structure. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Their study, titled “The Interior Structure of Ceres as Revealed by Surface Topography and Gravity“, was published in the journal Earth and Planetary Science Letters. Led by Roger Fu, an assistant professor with the Department of Earth, Atmospheric and Planetary Sciences at MIT, this team consisted of members from Virginia Tech, Caltech, the Southwest Research Institute (SwRI), the US Geological Survey, and the INAF.

Together, they investigated the strength and composition of Ceres’ crust and deeper interior by studying the dwarf planet’s topography. By modeling how the protoplanet’s crust flows, Fu and colleagues determined that it is likely a mixture of ice, salts, rock, and likely clathrate hydrate. This type of structure, which is composed of a gas molecule surrounded by water molecules, is 100 to 1,000 times stronger than water ice.

This high-strength crust, they theorize, could rest on a softer layer that contains some liquid. This would have allowed Ceres’ topography to deform over time, smoothing down features that were once more pronounced. It would also account for its possible ancient ocean, which would have frozen and become bound up with the crust. Nevertheless, some of its water would still exist in a liquid state underneath the surface.

This theory is consistent with several thermal evolution models which were published before the Dawn mission arrived at Ceres. These models contend that Ceres’ interior contains liquid water, similar to what has been found on Jupiter’s moon Europa and Saturn’s moon Enceladus. But in Ceres’ case, this liquid could be what is left over from its ancient ocean rather than the result of present-day geological activity in the interior.

Diagram showing a possible internal structure of Ceres. Credit: NASA/ESA/STScI/A. Feild

Taken together, these studies indicate that Ceres has had a long and turbulent history. While the first study found that Ceres’ crust is a mixture of ice, salts and hydrated materials – which represents most of its ancient ocean – the second study suggests there is a softer layer beneath Ceres’ rigid surface crust, which could be the signature of residual liquid left over from the ocean.

As Julie Castillo-Rogez, the Dawn project scientist at JPL and a co-author on both studies, explained, “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.”

On October 19, 2017, NASA announced that the Dawn mission would be extended until its fuel runs out, which is expected to happen in the latter half of 2018. This extension means that the Dawn probe will be in orbit around Ceres as it goes through perihelion in April 2018. At this time, surface ice will start to evaporate to form a transient atmosphere around the body.

During this period and long after, the spacecraft is likely to remain in a stable orbit around Ceres, where it will continue to send back information on this protoplanet/large asteroid. What it teaches us will also go a long way towards informing our understanding of the early Solar System and how it evolved over the past few billion years.

In the future, it is possible that a mission will be sent to Ceres that is capable of landing on its surface and exploring its topography directly. With any luck, future missions will also be able to explore the interior of Ceres, and other “ocean worlds” like Europa and Enceladus, and find out what lurks beneath their icy surfaces!

Further Reading: NASA

Dawn Gets Right in Between the Sun and Ceres and Takes this Video

The Dawn probe continues to excite and amaze! Since it achieved orbit around Ceres in March of 2015, it has been sending back an impressive stream of data and images on the protoplanet. In addition to capturing pictures of the mysterious “bright spots” on Ceres’ surface, it has also revealed evidence of cryovolcanism and the possibility of an interior ocean that could even support life.

Most recently, the Dawn probe conducted observations of the protoplanet while it was at opposition – directly between the Sun and Ceres surface – on April 29th. From this position, the craft was able to capture pictures of the Occator Crater, which contains the brightest spot on Ceres. These images were then stitched together by members of the mission team in order to create a short movie that showcases the view Dawn had of the planet.

The images were snapped when the Dawn probe was at an altitude of about 20,000 km (12,000 mi) from Ceres’ surface. As you can see (by clicking on the image below), the short movie shows the protoplanet rotating so that the Occator Crater is featured prominently. This crater is unmistakable thanks to the way its bright spots (two side by side white dots) stand out from the bland, grey landscape.

NASA movie made of images taken by NASA’s Dawn spacecraft, from a position exactly between the sun and Ceres’ surface. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

This increase in brightness is attributable to the size of grains of material on the surface, as well as their degree of porosity. As scientists have known for some time (thanks to the Dawn mission data) these bright spots are salt deposits, which stand out because they are more reflective than their surrounding environment. But for the sake of movie, this contrast was enhanced further in order to highlight the difference.

The observations were conducted as part of the latest phase of the Dawn mission, where it is recording cosmic rays in order to refine its earlier measurements of Ceres’ underground environment. In order to conduct these readings, the probe has been placed through an intricate set of maneuvers designed to shift its orbit around Ceres. Towards the end of April, this placed the probe in a position directly between the Sun and Ceres.

Based on previous data collected by ground-based telescopes and spacecraft that have viewed planetary bodies at opposition, the Dawn team predicted that Ceres would appear brighter from this vantage point. But rather than simply providing for some beautiful images of Ceres’ surface, the pictures are expected to reveal new details of the surface that are not discernible by visual inspection.

A view of Ceres in natural colour, pictured by the Dawn spacecraft in May 2015. Credit: NASA/JPL/Planetary Society/Justin Cowart

For more than two years now, the Dawn probe has been observing Ceres from a range of illumination angles that exceed those made of just about any other body in the Solar System. These has provided scientists with the opportunity to gain new insights into its surface features, properties, and the forces which shape it. Such observations will come in very handy as they continue to probe Ceres’ surface for hints of what lies beneath.

For years, scientists have been of the opinion that Ceres’ harbors an interior ocean that could support life. In fact, the Dawn probe has already gathered spectral data that hinted at the presence of organic molecules on the surface, which were reasoned to have been kicked up when a meteor impacted the surface. Characterizing the surface and subsurface environments will help determine if this astronomical body really could support life.

At present, the Dawn probe is maintaining an elliptical orbit that is taking it farther away from Ceres. As of May 11th, NASA reported that the probe was in good health and functioning well, despite the malfunction that took place in April where it’s third reaction wheel failed. The Dawn mission has already been extended, and it is expected to operate around Ceres until 2017.

Further Reading: NASA

Ceres Prank Lands Bart Simpson In Detention For Eternity

Do you see Bart Simpson's face on these surface features on Ceres? Researchers studying the surface of the dwarf planet for evidence of the presence of ice do. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, taken by Dawn Framing Camera

Human-kind has a long history of looking up at the stars and seeing figures and faces. In fact, there’s a word for recognizing faces in natural objects: pareidolia. But this must be the first time someone has recognized Bart Simpson’s face on an object in space.

Researchers studying landslides on the dwarf planet Ceres noticed a pattern that resembles the cartoon character. The researchers, from the Georgia Institute of Technology, are studying massive landslides that occur on the surface of the icy dwarf. Their findings are reinforcing the idea that Ceres has significant quantities of frozen water.

Dwarf planet Ceres is the largest object in the asteroid belt between Mars and Jupiter. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, taken by Dawn Framing Camera
Dwarf planet Ceres is the largest object in the asteroid belt between Mars and Jupiter. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, taken by Dawn Framing Camera

In a new paper in the journal Nature Geoscience, the team of scientists, led by Georgia Tech Assistant Professor and Dawn Science Team Associate Britney Schmidt, examined the surface of Ceres looking for morphologies that resemble landslides here on Earth.

Research shows us that Ceres probably has a subsurface shell that is rich with water-ice. That shell is covered by a layer of silicates. Close examination of the type, and distribution, of landslides at different latitudes adds more evidence to the sub-surface ice theory.

Ceres is pretty big. At 945 km in diameter, it’s the largest object in the asteroid belt between Mars and Jupiter. It’s big enough to be rounded by its own gravity, and it actually comprises about one third of the mass of the entire asteroid belt.

Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, taken by Dawn Framing Camera
Type 1 landslides on Ceres are large and occur at higher latitudes. Image: Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, taken by Dawn Framing Camera

The team used observations from the Dawn Framing Camera to identify three types of landslides on Ceres’ surface:

  • Type 1 are large, rounded features similar to glacier features in the Earth’s Arctic region. These are found mostly at high latitudes on Ceres, which is where most of the ice probably is.
  • Type 2 are the most common. They are thinner and longer than Type 1, and look like terrestrial avalanche deposits. They’re found mostly at mid-latitudes on Ceres. The researchers behind the study thought one of them looked like Bart Simpson’s face.
  • Type 3 occur mostly at low latitudes near Ceres’ equator. These are always found coming from large impact craters, and probably formed when impacts melted the sub-surface ice.
Type 3 landslides on Ceres occur at low latitudes at large craters, and form when ice is melted by impacts. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, taken by Dawn Framing Camera
Type 3 landslides on Ceres occur at low latitudes at large craters, and form when ice is melted by impacts. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, taken by Dawn Framing Camera

The authors of the study say that finding larger landslides further away from the equator is significant, because that’s where most of the ice is.

“Landslides cover more area in the poles than at the equator, but most surface processes generally don’t care about latitude,” said Schmidt, a faculty member in the School of Earth and Atmospheric Sciences. “That’s one reason why we think it’s ice affecting the flow processes. There’s no other good way to explain why the poles have huge, thick landslides; mid-latitudes have a mixture of sheeted and thick landslides; and low latitudes have just a few.”  

Key to understanding these results is the fact that these types of processes have only been observed before on Earth and Mars. Earth, obviously, has water and ice in great abundance, and Mars has large quantities of sub-surface ice as well. “It’s just kind of fun that we see features on this small planet that remind us of those on the big planets, like Earth and Mars,” Schmidt said. “It seems more and more that Ceres is our innermost icy world.”

“These landslides offer us the opportunity to understand what’s happening in the upper few kilometers of Ceres,” said Georgia Tech Ph.D. student Heather Chilton, a co-author on the paper. “That’s a sweet spot between information about the upper meter or so provided by the GRaND (Gamma Ray and Neutron Detector) and VIR (Visible and Infrared Spectrometer) instrument data, and the tens of kilometers-deep structure elucidated by crater studies.”

It’s not just the presence of these landslides, but the frequency of them, that upholds the icy-mantle idea on Ceres. The study showed that 20% to 30% of craters on Ceres larger than 10 km have some type of landslide. The researchers say that upper layers of Ceres’ could be up to 50% ice by volume.

Confirmed: Ceres Has a Transient Atmosphere

Sometimes they see it, sometimes they don’t. That’s why scientists have never been completely sure if Ceres has an atmosphere or not. But now data from the Dawn spacecraft — in orbit of Ceres — confirms the dwarf planet really does have a very weak atmosphere, but it comes and goes.

The on-again-off-again nature of Ceres’ atmosphere appears to be linked to solar activity. When energetic particles from the Sun hit exposed ice within the craters on Ceres, the ice can sublimate and create an “exosphere” that lasts for a week or so.

Michaela Villarreal from UCLA, lead author of the new study, and her team wrote in their paper that the “atmosphere appeared shortly after the passage of a large enhancement in the local flux of high-energy solar protons,” and explained that 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.

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. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI

A process like this could also be taking place on the Moon, and is likely similar to the process similar to what takes place on comets.

“Our results also have implications for other airless, water-rich bodies of the solar system, including the polar regions of the moon and some asteroids,” said Chris Russell, principal investigator of the Dawn mission, also at UCLA. “Atmospheric releases might be expected from their surfaces, too, when solar activity erupts.”

There have been hints of an atmosphere at Ceres since the early 1990’s. In 1991, the International Ultraviolet Explorer satellite detected hydroxyl emission from Ceres, but not in 1990. Then, in 2007, the European Southern Observatory’s Very Large Telescope searched for a hydroxide emission, but came up empty. The European Space Agency’s Herschel Space Observatory detected water vapor as a possible weak atmosphere, on three occasions, but did not on a fourth attempt.

Dwarf planet Ceres is located in the asteroid belt, between the orbits of Mars and Jupiter. Observations by ESA’s Herschel space observatory between 2011 and 2013 find that the dwarf planet has a thin water-vapour atmosphere. It is the first unambiguous detection of water vapour around an object in the asteroid belt. The inset shows the water absorption signal detected by Herschel on 11 October 2012. Copyright ESA/ATG medialab/Küppers et al.

The Dawn spacecraft itself saw evidence of a transient atmosphere when it arrived at Ceres in March 2015, with data from its Gamma Ray and Neutron Detector instrument. It also has found ample evidence for water in the form of ice, found just underground at higher latitudes, where temperatures are lower. Ice has been detected directly at the small bright crater called Oxo and in at least one of the craters that are persistently in shadow in the northern hemisphere. Other research has suggested that persistently shadowed craters are likely to harbor ice. Additionally, the shapes of craters and other features are consistent with significant water-ice content in the crust.

The team’s research shows the atmosphere doesn’t necessarily show up when Ceres is close to the Sun or when sunlight hits the ice directly, but from energetic particles released by the Sun when its activity level is high. For example, the best detections of Ceres’ atmosphere did not occur at its closest approach to the Sun.

Also, the times where no atmosphere was detected coincided with lower solar activity, so the researchers say this suggests that solar activity, rather than Ceres’ proximity to the Sun, is a more important factor in generating an exosphere.

Ceres actually is now getting closer to the Sun. However, since the Sun appears to be in a very quiet period, Villarreal, Russell and team predict an atmosphere won’t show up, that the dwarf planet will have little to no atmosphere for some time. However, they said both Dawn and other observatories should keep an eye on what’s happening at Ceres.

Paper: The Dependence of the Cerean Exosphere on Solar Energetic Particle Events

JPL press release

Brightest ‘Spot’ on Ceres is Likely a Cryovolcano

The bright regions on the dwarf planet Ceres have been some of the most talked about features in planetary science in recent years. While data from the Dawn spacecraft has shown these bright areas are salt deposits (alas, not lights of an alien city), the question remained of how these salts reached the surface.

Researchers with the Dawn mission say they have now thoroughly investigated the complex geological structures in Occator crater, the region with the brightest regions on Ceres. The scientists conclude that a bright dome-like feature called Cerealia Facula is the remnant of a cryovolcano — an ice volcano — that repeatedly and relatively recently spewed salty ice from within Ceres up to the surface.

“The age and appearance of the material surrounding the bright dome indicate that Cerealia Facula was formed by a recurring, eruptive process, which also hurled material into more outward regions of the central pit,” said Andreas Nathues, a Dawn scientist from the Max Planck Institute for Solar System Research. “A single eruptive event is rather unlikely.”

The bright central spots near the center of Occator Crater are shown in enhanced color in this view from NASA’s Dawn spacecraft. The view was produced by combining the highest resolution images taken in February 2016 (at image scales 115 feet (35 meters) per pixel of 35 meters with color images obtained in September 2015 at a lower resolution. Click for a highest-res view. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI

Occator crater located in the northern hemisphere of Ceres measures 92 kilometers (57 miles) in diameter. In its center is a pit with a diameter of about 11 kilometers (7 miles). On some parts of its edges, jagged mountains and steep slopes rise up to 750 meters (820 yards) high. Within the pit a bright dome formed. It has a diameter of 3 km (1.8 miles), is 400 meters (437 yards) high, with prominent fractures.

In analyzing images from Dawn’s Framing Camera, Nathues and his team deduced that the central pit is a remnant of a former central mountain, formed from the impact that created Occator Crater about 34 million years ago. But with a method for estimating the age of a planet’s surface – called crater counting — the science team could determine the dome of bright material is only about four million years old.

This suggests, the team said, that Occator crater has been the scene of eruptive outbursts of subsurface brine over a long period and until almost recently.

Jupiter’s moons Callisto and Ganymede show similar types of domes, and researchers interpret them as signs of cryovolcanism. While Ceres is too far from the Sun to be warm enough for regular volcanic activity, it very likely has harbored cryovolcanic activity, and it may even be active today.

This 3d-anaglyph for the first time shows a part of Occator crater in a combination of anaglyphe and false-color image. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Images from the Hubble Space Telescope taken more than a decade ago hinted at the bright spots in Occator Crater, but as the Dawn spacecraft approached Ceres in 2015, new images showed the bright areas almost shining like “cosmic beacons, like interplanetary lighthouses drawing us forth,” as described by Marc Rayman, the chief engineer and mission director for Dawn, in an interview with me last year.

Dawn scientist had previously determined the bright areas were salts left over from subsurface briny water that had made its way to the surface, and in the vacuum of space, the water sublimated away, leaving behind the dissolved salts. These salts were determined to be sodium carbonate and ammonium chloride.

This view of the whole Occator crater shows the brightly colored pit in its center and the cryovolcanic dome. The jagged mountains on the edge of the pit throw their shadows on parts of the pit. This image was taken from a distance of 1478 kilometers above the surface and has a resolution of 158 meters per pixel. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

But don’t call these bright areas “spots,” said Rayman. “Some of these bright areas are miles across,” he said, “and just as if you were standing on salt flats on Earth that were several thousand acres, you wouldn’t say, ‘I’m standing on a spot.’ You are standing on a big area. But just to see the distribution of this material in the Dawn images shows there is something complex going on there.”

It is currently unknown if the region in Occator Crater is active, but there are hints it is, at least at a low level.

In 2014 the Herschel spacecraft detected water vapor above Occator, and images from Dawn’s cameras of the crater show a ‘haze’ when imaged at certain angles, and this has been explained as the sublimation of water.

Dawn scientists are also studying the large volcanic feature on Ceres, Ahuna Mons, to determine if it could be a cryovolcano, and will continue to study other bright areas on Ceres, as well.

Ceres’ lonely mountain, Ahuna Mons, is seen in this simulated perspective view. The elevation has been exaggerated by a factor of two. Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI

Further Reading: Max Planck Institute for Solar System Research

Ceres Provides First Detection Of Life’s Building Blocks In Asteroid Belt

NASA’s Dawn spacecraft has been poking around Ceres since it first established orbit in March of 2015. In that time, the mission has sent back a steam of images of the minor planet, and with a level of resolution that was previously impossible. Because of this, a lot of interesting revelations have been made about Ceres’ composition and surface features (like its many “bright spots“).

In what is sure to be the most surprising find yet, the Dawn spacecraft has revealed that Ceres may actually possess the ingredients for life. Using data from the Dawn spacecraft’s Visible and InfraRed Mapping Spectrometer (VIMS), an international team of scientists has confirmed the existence of organic molecules on Ceres – a find which could indicate that it has conditions favorable to life.

These findings – which were detailed in a study titled Localized aliphatic organic material on the surface of Ceres” – appeared in the Feb. 17th, 2017, issue of Science. For the sake of their study, the international team of researchers – which was led by Maria Cristina de Sanctis from the National Institute of Astrophysics in Rome, Italy – showed how Dawn sensor data pointed towards the presence of aliphatic compounds on the surface.

Enhanced color-composite image from Dawn’s visible and infrared mapping spectrometer, showing the area around Ernutet Crater on Ceres. Credit: NASA/JPL-Caltech/UCLA/ASI/INAF

Aliphatics are a type of organic compound where carbon atoms form open chains that are commonly bound with oxygen, nitrogen, sulfur and chlorine. The least complex aliphatic is methane, which has been detected in many locations across the Solar System – including in the Martian atmosphere and in both liquid and gaseous form on Saturn’s moon Titan.

From their study, Dr. de Sanctis and her colleagues determined that spectral data obtained by the VIMS instrument corresponded to the presence of these hydrocarbons in a region outside of the Ernutet crater. This crater, which is located in the northern hemisphere of Ceres, measures about 52 km (32 mi) in diameter. The aliphatic compounds which were detected were localized in a roughly 1000 square kilometers region around it.

The team ruled out the possibility that these organic molecules were deposited from an external source – such as a comet or carbonaceous chondrite asteroid. While both have been shown to contain organic molecules in their interior in the past, the largest concentrations on Ceres were distributed discontinuously across the southwest floor and rim of the Ernutet crater and onto an older, highly degraded crater.

In addition, other organic-rich areas were spotted being are scattered to the northwest of the crater. As Dr.  Maria Cristina De Sanctis told Universe Today via email:

“The composition that we see on Ceres is similar to some meteorites that has organics and thus we searched for this material. We considered both endogenous and exogenous origin, but the last one seems less likely due to several reasons including the larger abundance observed on Ceres with respect the meteorites.”

Dawn spacecraft data, showing the organics absorption band (warmer colors indicate highest concentrations). Credit: NASA/JPL-Caltech/UCLA/ASI/INAF/MPS/DLR/IDA

Instead, they considered the possibility that they organic molecules were endogenous in origin. In the past, surveys have shown evidence of hydrothermal activity on Ceres, which included signs of surface renewal and fluid mobility. Combined with other surveys that have detected ammonia-bearing hydrated minerals, water ice, carbonates, and salts, this all points towards Ceres having an environment that can support prebiotic chemistry.

“The overall composition of Ceres can favor the pre-biotic chemistry,” said De Sanctis. “Ceres has water ice and minerals (carbonates and phyllosilicates) derived  from pervasive aqueous  alteration of rocks. It has also material that we think is formed in hydrothermal environments.  All these information indicate condition not hostel to biotic molecules.”

These findings are certainly significant in helping to determine if life could exist on Ceres – in a way that is similar to Europa and Enceladus, locked away beneath its icy mantle. But given that Ceres is believed to have originated 4.5 billion years ago (when the Solar System was still in the process of formation), this study is also significant in that it can shed light on the origin, evolution, and distribution of organic life in our the Solar System.

Other members of the research team include researchers from the department of Earth Planetary and Space Sciences at the University of California, the Department of Earth and Planetary Sciences at the University of Tennessee, the Department of Earth, Environmental, and Planetary Sciences at Brown University, the Southwest Research Institute (SwRI), the NASA Goddard Space Flight Center, and NASA’s Jet Propulsion Laboratory.

Further Reading: ScienceMag, SwRI