This image of Ceres was taken by NASA's Dawn spacecraft on May 7, 2015, from a distance of 8,400 miles (13,600 kilometers). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Video caption: This new video animation of Ceres was created from images taken by NASA’s Dawn spacecraft at altitudes of 8,400 miles (13,600 kilometers) and 3,200 miles (5,100 kilometers) away. Vertical dimension has been exaggerated by a factor of two and a star field added. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Scientists leading NASA’s Dawn mission to dwarf planet Ceres have just released a brand new animated video showing a dramatic fly over of the heavily cratered world featuring its mysterious bright spots whose exact origin and nature remain elusive.
Meanwhile, the venerable probe has just successfully entered its new and lower mapping orbit on June 3 from which researchers hope to glean hordes of new data to unravel the secrets of the bright spots and unlock the nature of Ceres origin and evolution.
Pockmarked Ceres is an alien world unlike any other in our solar system.
“Dawn completed the maneuvering to reach its second mapping orbit and stopped ion-thrusting on schedule. Since May 9, the spacecraft has reduced its orbital altitude from 8,400 miles (13,600 kilometers) to 2,700 miles (4,400 kilometers),” reported Marc Rayman, Dawn Chief Engineer/ Mission Director of NASA’s Jet Propulsion Laboratory, Pasadena, California.
“As Dawn flew 2,700 miles (4,400 kilometers) over Ceres’ north pole on June 5 that marked the beginning of the new mapping phase, and Dawn began taking photos and making other measurements on schedule.”
Each orbit of Dawn around Ceres at this second science mapping orbit lasts 3.1 days.
The new video was created by the research team based on observations of Ceres that were taken from Dawn’s initial mapping orbit, at an altitude of 8,400 miles (13,600 kilometers), as well as the most recent navigational images taken from 3,200 miles (5,100 kilometers), according to NASA.
It is based on data from over 80 images captured by Dawn’s framing cameras which were provided The German Aerospace Center (DLR) and Max Planck Institute for Solar System Research in Göttingen, Germany.
The images were used to provide a three-dimensional video view. The vertical dimension is exaggerated by a factor of two in the video.
“We used a three-dimensional terrain model that we had produced based on the images acquired so far,” said Dawn team member Ralf Jaumann of the German Aerospace Center (DLR), in Berlin.
“They will become increasingly detailed as the mission progresses — with each additional orbit bringing us closer to the surface.”
Imagery of the mysterious bright spots show them to seemingly be sheets of many spots of water ice, and not just single huge patches. The famous duo of ice spots are located inside the middle of a 57 miles (92 kilometers) wide crater situated in Ceres northern hemisphere.
Dawn is an international science mission managed by NASA’s Jet Propulsion Laboratory, Pasadena, California. The trio of science instruments are from the US, Germany and Italy.
The framing camera was provided by the Max Planck Institute for Solar System Research, Göttingen, Germany and the German Aerospace Center (DLR).
This view of Ceres was taken by Dawn spacecraft on May 23 and shows finer detail becoming visible on the dwarf planet. The spacecraft snapped the image at a distance of 3,200 miles (5,100 kilometers) with a resolution of 1,600 feet (480 meters) per pixel. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Dawn will spend most if June at this second mapping orbit before firing up the ion engines and spiraling yet lower for a mission expected to last until at least June 2016.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
Dawn’s spiral descent from its first mapping orbit (RC3) to its second (survey). The two mapping orbits are shown in green. The color of Dawn’s trajectory progresses through the spectrum from blue, when it began ion-thrusting on May 9, to red, when ion-thrusting concludes on June 3. The red dashed sections show where Dawn is coasting, mostly for telecommunications. The first two coast periods include OpNav 8 and 9. Image credit: NASA/JPL-Caltech
Latest image released by NASA of the spatter of white spots in the 57-mile-wide crater on the dwarf planet Ceres. Scientists with the Dawn mission believe they're highly reflective material, likely ice. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
The latest views of Ceres’ enigmatic white spots are sharper and clearer, but it’s obvious that Dawn will have to descend much lower before we’ll see crucial details hidden in this overexposed splatter of white dots. Still, there are hints of interesting things going on here.
Comparison of the most recent photos of the white spots taken Dawn’s current 4,500 miles vs. 8,400 miles on May 4. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
The latest photo is part of a sequence of images shot for navigation purposes on May 16, when the spacecraft orbited 4,500 miles (7,200 km) over the dwarf planet. Of special interest are a series of troughs or cracks in Ceres crust that appear on either side of the crater housing the spots.
While the exact nature of the spots continues to baffle scientists, Christopher Russell, principal investigator for the Dawn mission, has narrowed the possibilities: “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.”
The bright material in both photos was excavated from below the surface and deposited nearby by a 2008 impact that dug a crater about 26 feet (8 meters) in diameter. The extent of the bright patch was large enough for the Compact Reconnaissance Imaging Spectrometer for Mars, an instrument on NASA’s Mars Reconnaissance Orbiter, to obtain information confirming it as water ice. Credit: NASA/JPL-Caltech/University of Arizona
We’ve seen ice exposed by meteorite / asteroid impact before on Mars where recent impacts have exposed fresh ice below the surface long hidden by dust. In most cases the ice gradually sublimates away or covered by dust over time. But if Ceres’ white spots are ice, then we can reasonably assume they must be relatively new features otherwise they would have vaporized or sublimated into space like the Martian variety.
NASA’s Hubble Space Telescope took these images of the asteroid 1 Ceres over a 2-hour and 20-minute span, the time it takes the Texas-sized object to complete one quarter of a rotation. The observations were made in visible and in ultraviolet light. Hubble took the snapshots between December 2003 and January 2004. Credit: NASA, ESA, J. Parker, P. Thomas and L. McFadden
Much has been written – including here – that these spots are the same as those photographed in much lower resolution by the Hubble Space Telescope in 2004. But according the Phil Plait, who writes the Bad Astronomy blog, that’s false. He spoke to Joe Parker, who was part of the team that made the 2004 photos, and Parker says the Dawn spots and Hubble spots are not the same.
Could the spots have formed post-2004 or were they simply too small for Hubble to resolve them? That seems unlikely. The chances are slim we’d just happen to be there shortly after such a rare event occurred? And what happened to Hubble’s spot – did it sublimate away?
Video compiled from Dawn’s still frames of Ceres by Tom Ruen. Watch as the spots continue to reflect light even at local sunset.
Watching the still images of Ceres during rotation, it’s clear that sunlight still reflects from the spots when the crater fills with shadow at sunset and sunrise. This implies they’re elevated, and as far as I can tell from the sunrise photo (see below), the brightest spots appear to shine from along the the side of a hill or mountain. Could we be seeing relatively fresh ice or salts after recent landslides related to impact or tectonic forces exposed them to view?
Single from from the video shows the white spots shortly after sunrise. The brightest appear to be located on a central mountain peak. It’s unclear if the pair of spots below the bright pair are situated on a rise or the flat floor. Credit: NASA
Let’s visit another place in the Solar System with an enigmatic white spot, or should I say, white arc. It’s Wunda Crater on Uranus’ crater-blasted moon Umbriel. The 131-mile-wide crater, situated on the moon’s equator, is named for Wunda, a dark spirit in Aboriginal mythology. But on its floor is a bright feature about 6 miles (10 km) wide. We still don’t know what that one is either!
The moon Umbriel, 727 miles in diameter, with Wunda Crater and its bright internal ring of unknown origin. The moon’s equator is vertical in this photo. Credit: NASA
Photos of the white spots within the 57-mile-wide on Ceres photographed on May 3 and 4 by NASA's Dawn spacecraft. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA / montage by Tom Ruen
We don’t know exactly what those mysterious white spots on Ceres are yet, but we’re getting closer to an explanation. Literally. The latest images from the Dawn spacecrafttaken a mere 8,400 miles from the dwarf planet Ceres reveal that the pair of spots are comprised of even more spots.
“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,” said Christopher Russell, principal investigator for the Dawn mission from the University of California, Los Angeles.
This animation shows a sequence of images taken by NASA’s Dawn spacecraft on May 4, 2015, from a distance of 8,400 miles (13,600 km), in its RC3 or science mapping orbit. The image resolution is 0.8 mile (1.3 km) per pixel. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Dawn recently concluded its first science orbit, making a 15-day full circle around Ceres while gathering data with its suite of science instruments. This past Saturday, May 9, its ion engine fired once again to lower the spacecraft to its second science orbit which it will enter on June 6. On that date, the probe will hover just 2,700 miles (4,400 km) above the dwarf planet and begin a comprehensive mapping of the surface. Scientists also hope the bird’s eye view will reveal clues of ongoing geological activity.
Check out this great video compiled from Dawn’s still frames of Ceres by Tom Ruen. Almost feels like you’re there.
There’s no doubt a lot’s been happening on Ceres. One look at all those cracks hint at either impact-related stresses some kind of crustal expansion. Geological processes may still make this little world rock and roll.
In this uncropped single frame, not only are multiple white spots visible but also long, roughly parallel cracks or troughs in Ceres’ surface. Are they impact-related or caused by some other stress? Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Fortunately, we won’t have to wait till next month for more photos. NASA plans to pause the probe twice on the way down to shoot and send fresh images.
Dawn's framing camera took these images of Ceres on April 10, 2015 which were combined into a short animation. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Brand new images taken on April 10 by NASA’s Dawn probe show the dwarf planet from high above its north pole. Photographed at a distance of just 21,000 miles (33,000 km) — less than 1/10 the Earth-moon distance — they’re our sharpest views to date. The crispness combined with the low-angled sunlight gives Ceres a stark, lunar-like appearance.
Artist’s concept of Dawn above Ceres around the time it was captured into orbit by the dwarf planet in early March. Since its arrival, the spacecraft turned around to point the blue glow of its ion engine in the opposite direction. Because it’s been facing the Sun while lowering its orbit, the new images of Ceres show it as a crescent. Credit: NASA/JPL
Images will only get better. Dawn arrived at Ceres on March 6 and immediately got to work using its ion thrusters in conjunction with the dwarf planet’s gravity to gradually lower itself into a circular orbit. Once the spacecraft settles into its first science orbit on April 23 at a distance of 8,400 miles from the surface, it will begin taking a hard look at this cratered mini-planet. A little more than two weeks later, the probe will spiral down for an even closer view on May 9.
The map is an enhanced color view that offers an expanded range of the colors visible to human eyes. Pictures were taken using blue, green and infrared filters and combined. Scientists use this technique to highlight subtle color differences across Ceres, which can provide insights into the physical properties and composition of the surface. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/ID
Dawn’s gravity spiral continues throughout the summer and fall until the probe tiptoes down to just 233 miles (375 km) altitude in late November. From there it will deploy its Gamma Ray and Neutron Detector (GRaND) to map the elements composing Ceres’ surface rocks. We’re in for a great ride!
Simulated Ceres rotation by Tom Ruen using the new color map
Meanwhile, scientists have assembled images taken by Dawn through blue, green and infrared filters to create a new color-enhanced map of the dwarf planet. The variety of landforms in conjunction with the color variations hint that Ceres was once an active body or one with the means to resurface itself from within. Mechanisms might involve internal heating and / or movement of water or ice.
Pictures from Dawn’s VIR instrument highlight two regions on Ceres containing bright spots. The top images show a region scientists labeled “1” and the bottom images show the region labeled “5,” which show the Ceres’ brightest pair of spots. Region 1 is cooler than the rest of Ceres’ surface, but region 5 appears to be located in a region that is similar in temperature to its surroundings. Credit: NASA/JPL-Caltech/UCLA/ASI/INAF
There are still no new close-ups of the pair of enigmatic white spots taunting us from inside that 57-mile-wide crater. But there is a bit of news. Dawn’s visible and infrared mapping spectrometer or VIR has already examined Ceres in visible and infrared or thermal light. Data from VIR indicate that light and darker regions on the dwarf planet have different properties.
A topographic map of Ceres with provisional names given to each quadrangle. Ceres’ craters are named for agricultural gods; other features after world agricultural festivals. Let’s hope the names are made permanent. I mean, you can’t beat Yumyum. Credit: NASA / JPL / UCLA / MPS / DLR / IDA / JohnVV / Emily Lakdawalla
The bright spots are located in a region with a temperature similar to its surroundings. However, a different bright feature appears in a region that’s cooler than the neighboring surface. Exactly what those variations are telling us will hopefully become clear once Dawn returns more detailed images:
“The bright spots continue to fascinate the science team, but we will have to wait until we get closer and are able to resolve them before we can determine their source,” said Chris Russell, principal investigator for the Dawn mission.
The slim crescent of Ceres smiles back as the dwarf planet awaits the arrival of an emissary from Earth. This image was taken by NASA’s Dawn spacecraft on March 1, 2015, just a few days before the mission achieved orbit around the dwarf planet. Because of its angle of approach (see video above) Dawn saw Ceres from its backside, which from its perspective, was mostly in darkness. Credit: NASA/JPL
Dawn’s approach and trajectory as it begins its orbital “dance” with Ceres. As you watch, note the timeline at upper right.
Dawn made it! After a 14-month tour of the asteroid Vesta and 2 1/2 years en route to Ceres, the spacecraft felt the gentle tug of Ceres gravity and slipped into orbit around the dwarf planet at 6:39 a.m. (CST) Friday morning.
“We feel exhilarated,” said lead researcher Chris Russell at the University of California, Los Angeles, after Dawn radioed back the good news.
Not only is this humankind’s first probe to orbit a dwarf planet, Dawn is the only spacecraft to fly missions to two different planetary bodies. Dawn’s initial orbit places it 38,000 miles (61,000 km) from Ceres with a view of the opposite side of Ceres from the Sun. That’s why we’ll be seeing photos of the dwarf planet as a crescent for the time being. If you watch the video, you’ll notice that Dawn won’t see Ceres’ fully sunlit hemisphere until early-mid April.
Dawn’s spiral descent from survey orbit to the high altitude mapping orbit. The trajectory progresses from blue to red over the course of the six weeks. The red dashed segments are where the spacecraft is not thrusting with its ion propulsion system. Credit: NASA/JPL
The spacecraft will spend the next month gradually spiraling down to Ceres to reach its “survey orbit” of 2,730 miles in April. From there it will train its science camera and visible and infrared mapping spectrometer to gather pictures and data. The leisurely pace of the orbit will allow Dawn to spend more than 37 hours examining Ceres’ dayside per revolution. NASA will continue to lower the spacecraft throughout the year until it reaches its minimum altitude of 235 miles.
As Dawn maneuvers into orbit, its trajectory takes it to the opposite side of Ceres from the sun, providing these crescent views. These additional pictures were taken on March 1 at a distance of 30,000 miles (49,000 km). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
“Since its discovery in 1801, Ceres was known as a planet, then an asteroid and later a dwarf planet,” said Marc Rayman, Dawn chief engineer and mission director at JPL. “Now, after a journey of 3.1 billion miles (4.9 billion kilometers) and 7.5 years, Dawn calls Ceres, home.”
More about Dawn’s incredible accomplishment can be found in the excellent Dawn Journal, written by Dawn chief engineer and mission director Marc Rayman.
Artist’s concept of Dawn in its survey orbit at dwarf planet Ceres. Credit: NASA/JPL-Caltech
On March 6, the Dawn spacecraft will ease into orbit around the dwarf planet Ceres. This is the visit to a dwarf planet (New Horizons will flyby Pluto later this year) and scientists are eager to see its surface in detail. But did you know that Ceres got its name from the ancient Roman goddess of agriculture and grain crops? Think about that when you enjoy your breakfast!
As we mentioned in our previous article about the intriguing white spots that Dawn has seen on Ceres as it makes its approach, Dawn will then continue to spiral its way down to an altitude of about 920 miles (1,480 kilometers), and in August 2015 will begin a two-month phase known as the high-altitude mapping orbit. Then, it will spiral down to an altitude of about 2,750 miles (4,430 kilometers), and obtain more science data in its survey science orbit. This phase will last for 22 days, and is designed to obtain a global view of Ceres with Dawn’s framing camera, and global maps with the visible and infrared mapping spectrometer (VIR).
Dawn will then continue to spiral its way down to an altitude of about 920 miles (1,480 kilometers), and in August 2015 will begin a two-month phase known as the high-altitude mapping orbit. During this phase, the spacecraft will continue to acquire near-global maps with the VIR and framing camera at higher resolution than in the survey phase. The spacecraft will also image in “stereo” to resolve the surface in 3-D.
Then, after spiraling down for two months, Dawn will begin its closest orbit around Ceres in late November, at a distance of about 233 miles (375 kilometers). The dance at low-altitude mapping orbit will be a long waltz — three months — and is specifically designed to acquire data with Dawn’s gamma ray and neutron detector (GRaND) and gravity investigation. GRaND will reveal the signatures of the elements on and near the surface. The gravity experiment will measure the tug of the dwarf planet, as monitored by changes in the high-precision radio link to NASA’s Deep Space Network on Earth.
Dawn’s nominal mission to Ceres is expected to last for 16 months.
Ceres rotates in this sped-up movie comprised of images taken by NASA's Dawn mission during its approach to the dwarf planet. The images were taken on Feb. 19, 2015, from a distance of nearly 29,000 miles (46,000 kilometers). Dawn observed Ceres for a full rotation of the dwarf planet, which lasts about nine hours. The images have a resolution of 2.5 miles (4 kilometers) per pixel. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
As the Dawn spacecraft prepares to enter orbit around Ceres on March 6, the science team provided the latest images and a mission preview during a briefing on March 2. The images released yesterday show more of those unusual bright spots and lots of craters, and feature two new global views of Ceres: one spinning globe, and a mosaic of a flat map-view of Ceres’ surface.
But the most-talked about feature is the 90-km-wide (57-mile) crater with two bright spots.
“These spots are extremely surprising and have been puzzling to the team and everyone that has seen them,” said Deputy Principal Investigator Carol Raymond. “The team is really, really excited about this feature because it is unique in the solar system.”
Raymond added that the team will be revealing the true nature of spots with the public in real time as the spacecraft gets closer and is able to make a determination.
So what is the leading theory on the bright spots?
The surface of Ceres is covered with craters of many shapes and sizes, as seen in this new mosaic of the dwarf planet comprised of images taken by NASA’s Dawn mission on Feb. 19, 2015 from a distance of nearly 29,000 miles (46,000 kilometers). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.
While cryovolcanoes have been bantered around as a possibility, during the briefing yesterday the science team downplayed that possibility, citing several pieces of evidence.
First, Raymond said the spots are consistent with highly reflective materials that may contain ice or salts. As an example of this, this morning, Cassini imaging lead Carolyn Porco tweeted an image of exposures of bright ice on Saturn’s moon Phoebe.
Raymond added that if the bright features end up to be liquid water, salt would be most likely element that would keep the water from freezing. The science team will also be looking for dust levitating from the surface, as sublimating gases could cause dust to rise.
Secondly, Raymond said if the bright spots were a cryovolcano, they would expect to see some type of surface evidence of a mound, peak or crack. “We don’t see that with the bright spots so a cryovolcano is unlikely,” she said.
NASA’s Dawn spacecraft took these images of dwarf planet Ceres from about 25,000 miles (40,000 kilometers) away on Feb. 25, 2015. Ceres appears half in shadow because of the current position of the spacecraft relative to the dwarf planet and the sun. The resolution is about 2.3 miles (3.7 kilometers) per pixel. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.
Third, — and this is also for anyone who may be thinking there is a beam or light-creating mechanism on the surface — team member Chris Russell said there is quite conclusive evidence that the spots are reflecting light, not creating light.
“We have followed the light curve into the terminator,” he said. “The spots do get darker and then go out when the terminator is reached.”
The terminator is the term for the boundary between day and night.
Lastly, even though in 2014 the Herschel spacecraft detected water vapor coming from two longitudal regions on Ceres (one of them is the region where crater with the bright spots is located), the current evidence points to the vaporization or sublimation of ice, not a spewing cryovolcano.
The Herschel team estimated that approximately 6 kg of water vapor is being produced per second, requiring only a tiny fraction of Ceres to be covered by water ice. This links nicely to the two localized surface features that the Herschel team observed and to the bright spots observed by Dawn.
Raymond said the Dawn science team should be able to verify the Herschel emissions, as they have modeled a similar emission coming from a distributed area and they are confident that observations with Dawn’s infrared spectrometer could detect such an emission, if present. “So if the activity is still ongoing, or if it is coming from a deposit left behind, we should be able to detect it,” she said.
This image was taken by NASA’s Dawn spacecraft of dwarf planet Ceres on Feb. 19 from a distance of nearly 29,000 miles (46,000 kilometers). It shows that the brightest spot on Ceres has a dimmer companion, which apparently lies in the same basin. Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
After Dawn enters orbit, it will make its first full characterization of Ceres later in April, at an altitude of about 8,400 miles (13,500 kilometers), and it will then spiral down to an altitude of about 2,750 miles (4,430 kilometers), and obtain more science data in its survey science orbit. This phase will last for 22 days, and is designed to obtain a global view of Ceres with Dawn’s framing camera, and global maps with the visible and infrared mapping spectrometer (VIR).
Dawn will then continue to spiral its way down to an altitude of about 920 miles (1,480 kilometers), and in August 2015 will begin a two-month phase known as the high-altitude mapping orbit. During this phase, the spacecraft will continue to acquire near-global maps with the VIR and framing camera at higher resolution than in the survey phase. The spacecraft will also image in “stereo” to resolve the surface in 3-D.
Then, after spiraling down for two months, Dawn will begin its closest orbit around Ceres in late November, at a distance of about 233 miles (375 kilometers), allowing Dawn’s gamma ray and neutron detector (GRaND) and gravity investigation to make their observations.
Dawn’s nominal mission to Ceres is expected to last for 16 months, until near the end of 2016. There is a possibility of an extended mission, but that will depend on the amount of fuel left in the Dawn’s tank. While Dawn’s ion engine is nearly limitless in its power, hydrazine is used for attitude control or pointing the spacecraft – pointing it to Ceres to take images and pointing it back to Earth to send data. Robert Mase, Dawn project manager said the hydrazine the most scarce resource in terms of an extended mission.
“There’s not a likely prospect of years and years ahead of us,” he said.
Jim Green, director of NASA’s Planetary Science Division said while Dawn has plenty of fuel for its nominal mission, it likely won’t last more than a few months in an extended mission.
“We will take stock of how much hydrazine is left and then go through a process of evaluation if we can give the go ahead for an extended mission,” he said. “I’m sure it will observe some really exciting things, but we have to see what the fuel reserves are before we make that decision.”
Still, Dawn will remain in a stable orbit around Ceres for hundreds of years.
This image was taken by NASA's Dawn spacecraft of dwarf planet Ceres on Feb. 19 from a distance of nearly 29,000 miles (46,000 km). It shows that the brightest spot on Ceres has a dimmer companion, which apparently lies in the same basin. See below for the wide view. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Aliens making dinner with a solar cooker? Laser beams aimed at hapless earthlings? Whatever can that – now those – bright spots on Ceres be? The most recent images taken by the Dawn spacecraftnow reveal that the bright pimple has a companion spot. Both are tucked inside a substantial crater and seem to glow with an intensity out of proportion to the otherwise dark and dusky surrounding landscape.“The brightest spot continues to be too small to resolve with our camera, but despite its size it is brighter than anything else on Ceres,” said Andreas Nathues, lead investigator for the framing camera team at the Max Planck Institute for Solar System Research, Gottingen, Germany. “This is truly unexpected and still a mystery to us.”
Tight crop of the two bright spots. Could they be ice? Volcano-related? Credit:
It’s a mystery bound to stir fresh waves of online speculative pseudoscience. The hucksters better get moving. Dawn is fewer than 29,000 miles (46,000 km) away and closing fast. On March 6 it will be captured by Ceres gravity and begin orbiting the dwarf planet for a year or more. Like waking up and rubbing the sleep from your eyes, our view of Ceres and its enigmatic “twin glows” will become increasingly clear in about six weeks.
Dawn approaches Ceres from the left (direction of the Sun) and gets captured by its gravity. The craft first gets closer as it approaches but then recedes (moves off to right) before closing in again and ultimately settling into orbit around the asteroid. The solid lines show where Dawn is thrusting with its ion engine. As it swings to the right, photos will show Ceres as a crescent. Credit: NASA/Marc Rayman
Why not March 6th when it enters orbit? Momentum is temporarily carrying the probe beyond Ceres. Only after a series of balletic moves to reshape its orbit to match that of Ceres will it be able to return more detailed images. You’ll recall that Rosetta did the same before finally settling into orbit around Comet 67P.
Closest approach occurred on Feb. 23 at 24,000 miles (38,600 km); at the moment the spacecraft is moving beyond Ceres at the very relaxed rate of 35 mph (55 kph).
This and the photo below were taken on Feb. 19, 2015 and processed to enhance clarity. Notice the very large but shallow crater below center. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
We do know that unlike Dawn’s first target, the asteroid Vesta, Ceres is rich in water ice. It’s thought that it possesses a mantle of ice and possibly even ice on its surface. In January 2014, ESA’s orbiting Herschel infrared observatory detected water vapor given off by the dwarf planet. Clays have been identified in its crust as well, making Ceres unique compared to many asteroids in the main belt that orbit between Mars and Jupiter.
Given the evidence for H20, we could be seeing ice reflecting sunlight possibly from a recent impact that exposed new material beneath the asteroid’s space-weathered skin. If so, it’s odd that the spot should be almost perfectly centered in the crater.
A different hemisphere of Ceres photographed on Feb. 19. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Chris Russell, principal investigator for the Dawn mission, offers another possible scenario, where the bright spots “may be pointing to a volcano-like origin.” Might icy volcanism in the form of cryovolcanoes have created the dual white spots? Or is the white material fresh, pale-colored rock either erupted from below or exposed by a recent impact? Ceres is a very dark world with an albedo or reflectivity even less than our asphalt-dark Moon. Freshly exposed rock or ice might stand out starkly.
A part slice of the eucrite meteorite NWA 3147. Most eucrites are derived from lava flows on the asteroid Vesta and are rich in light-toned minerals. Credit: Bob King
One of the more common forms of asteroid lava found on Earth are the eucrite achondrite meteorites. Many are rich in plagioclase and other pale minerals that are good reflectors of light. Of course, these are all speculations, but the striking contrast of bright and dark certainly piques our curiosity.
Artist’s concept of Dawn in its survey orbit at dwarf planet Ceres. Credit: NASA/JPL-Caltech
Additional higher resolutions photos streamed back by Dawn show a fascinating array of crater types from small and deep to large and shallow. On icy worlds, ancient impact craters gradually “relax” and lose relief over time, flattening as it were. We’ve seen this on the icy Galilean moons of Jupiter and perhaps the largest impact basins on Ceres are examples of same.
Questions, speculations. Our investigation of any new world seen up close for the first time always begins with questions … and often ends with them, too.
ILLUSTRATION IS RESERVED - DO NOT USE. The eight planets of the Solar System and the dwarf planet Pluto. For many astronomers and planetary scientists Pluto's status remains an open question. Redefining what is a planet could return Pluto to the fold - 9 planets and also open the door for many more. Insets from upper left, clockwise: Clyde Tombaugh, Mike Brown, Alan Stern, Gerard Kuiper.(Credit: NASA, Judy Schmidt, Björn Jónsson)
A storm is brewing, a battle of words and a war of the worlds. The Earth is not at risk. It is mostly a civil dispute, but it has the potential to influence the path of careers. In 2014, a Harvard led debate was undertaken on the question: Is Pluto a planet. The impact of the definition of planet and everything else is far reaching – to the ends of the Universe.
It could mean a count of trillions of planets in our galaxy alone or it means leaving the planet Pluto out of the count – designation, just a dwarf planet. This is a question of how to classify non-stellar objects. What is a planet, asteroid, comet, planetoid or dwarf planet? Does our Solar System have 8 planets or some other number? Even the count of planets in our Milky Way galaxy is at stake.
“Dawn arising.” The latest image of Ceres – February 12, 2015 – by the Dawn spacecraft from 80,000 km. With icy deposits pock marking its surface, a possible reservoir of water below its surface, is Ceres a planet, dwarf planet, an asteroid or all three? (Credit: NASA/Dawn)
Not to dwell on the Harvard debate, let it be known that if given their way, the debates outcome would reset the Solar System to nine planets. For over eight years, the solar system has had eight planets. During the period 1807 to 1845, our Solar System had eleven planets. Neptune was discovered in 1846 and astronomers began to discover many more asteroids. They were eliminated from the club. This is very similar to what is now happening to Pluto-like objects – Plutoids. So from 1846 to 1930, there were 8 planets – the ones as defined today.
The discoverer of Pluto – Clyde Tombaugh in the 1930s and again with homebuilt telescope in the 1990s that earned him an assignment at Lowell Observatory – discover Planet X. The cremated remains of Clyde are attached to the New Horizons space probe that is now approaching the dwarf planet Pluto.
In 1930, a Kansas farm boy, Clyde Tombaugh, hired by Lowell Observatory discovered Pluto and for 76 years there were 9 planets. In the year 2006, the International Astronomical Union (IAU) took up a debate using a “democratic process” to accept a new definition of planet, define a new type – dwarf planet and then set everything else as “Small Bodies.” If your head is spinning with planets, you are not alone.
All two body systems have a barycenter, the shared point in space around which they orbit. Pluto and Charon’s happens to be between both bodies due to their proximity and similar mass. (Credit: NASA/New Horizons)
Two NASA missions were launched immediately before and after the IAU announcement took affect. The Dawn mission suddenly was to be launched to an asteroid and a dwarf planet and the New Horizons had rather embarked on a nine year journey to a planet belittled to a dwarf planet – Pluto. Principal Investigator, Dr. Alan Stern was upset. Furthermore, from the discoveries of the Kuiper mission and other discoveries, we now know that there are hundreds of billions of planets in our Milky Way galaxy; possibly trillions. The present definition excludes hundreds of billions of bodies from planethood status.
The presently known largest trans-Neptunian objects (TSO) – are likely to be surpassed by future discoveries. Which of these trans-Neptunian objects (TSO) would you call planets and which “dwarf planets”? (Illustration Credit: Larry McNish, Data: M.Brown)
There are two main camps with de facto leaders. One camp has Dr. Mike Brown of Caltech and the other, Dr. Stern of the Southwest Research Institute (SWRI) as leading figures. A primary focus of Dr. Brown’s research is the study of trans-Neptunian objects while Dr. Sterns’s activities are many but specifically, the New Horizons mission which is 6 months away from its flyby of Pluto. Consider first the IAU Resolution 5A that its members approved:
(1) A “planet” is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.
(2) A “dwarf planet” is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape2, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.
(3) All other objects, except satellites, orbiting the Sun shall be referred to collectively as “Small Solar System Bodies”.
This is our starting point – planet, dwarf planet, everything else. Consider “everything else”. This broad category includes meteoroids, asteroids, comets and planetesimals. Perhaps other small body types will arise as we look more closely at the Universe. Within the category, there is now a question of what is an asteroid and what is a comet. NASA’s flybys of comets and now ESA’s Rosetta at 67P/Churyumov–Gerasimenko are making the delineation between the two types difficult. The difference between a meteoroid and an asteroid is simply defined as less than or greater than one meter in size, respectively. So the Chelyabinsk event absolutely involved a small asteroid – about 20 meters in diameter. Planetesimals are small bodies in a solar nebula that are the building blocks of planets but they could lead to the creation of all the other types of small bodies.
Dr. Alan Stern, project scientist for New Horizons and Neil deGrasse Tyson discuss the New Horizons spacecraft in the mission operations center at JHU/APL. The interview was for a NOVA special (12/14/2011), the Pluto Files, about a Kansas farm boy, a missing planet and the 70 years of astronomical discoveries leading to the present day. (Credit: JHU/APL,PBS)
Putting aside the question of “Small Bodies” and its sub-classes, what should be the definition of planet and dwarf planet? These are the two terms that demoted Pluto and raised Ceres to dwarf planet. It is also interesting to note how Resolution 5A is meant exclusively for our Solar System. In 2006, there were not thousands of exo-planets but just a few dozen extreme cases but nevertheless, the IAU did not choose to extend the definition to “stars” but rather just in reference to our pretty well known star, the Sun.
Recall Tim Allen’s movie, “The Santa Clause”. Clauses can cause a heap of trouble. The IAU has such a clause – Clause C which has caused much of the present controversy around the definition of planets. Clause (c) of Resolution 5A: “has cleared the neighborhood around its orbit.” This is the Pluto killer-clause which demoted it to dwarf planet status and reduced the number of planets in our solar system to eight. In a sense, the IAU chose to cauterize a wound, a weakness in the definitions, that if left unchanged, would have led to who knows how many planets in our Solar System.
The question of what is Pluto is open for public discussion so armed with enough knowledge to be dangerous, the following is my proposed alternative to the IAU’s that are arguably an improvement. The present challenge to Pluto’s status lies in the Kuiper Belt and Oort Cloud. Such belts or clouds are probably not uncommon throughout the galaxy. Plutoids are the 500 lb gorilla in the room.
Two spacecraft, Dawn and New Horizon will reach their final objectives in 2015 – Dwarf Planets – Ceres and Pluto. (Credit: NASA, Illustration – T.Reyes)
This year, as touted by the likes of Planetary Society, Universe Today and elsewhere, is the year of the dwarf planet. How remarkable and surprising will the study of Ceres, Pluto and Charon by NASA spacecraft be? There is a strong possibility that after the celestial dust clears and data analysis is published, the IAU will take on the challenge again to better define what is a planet and everything else. It is impossible to imagine that the definitions can remain unchanged for long. Even now, there is sufficient information to independently assess the definitions and weigh in on the approaching debate. Anyone or any group – from grade schools to astronomical societies – can take on the challenge.
To encourage a debate and educate the public on the incredible universe that space probes and advanced telescopes are revealing, what follows is one proposed solution to what is a planet and everything else.
planet: is a celestial body that a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium – nearly round shape, b) has a differentiated interior as a result of its formation c) has insufficient mass to fuse hydrogen in its core, d) does not match the definition of a moon.
minor planet: is a planet with a mass less than one Pluto mass and does not match the definition of a moon.
inter-Stellar (minor) planet: is a (minor) planet that is not gravitationally bound to a stellar object.
binary (minor) planet: is a celestial body that is orbiting another (minor) planet for which the system’s barycenter resides above the surface of both bodies.
These definitions solve some hairy dilemmas. For one, planets orbit around the majority of most stars in the Universe, not just the Sun as Resolution 5A was only intended. Planets can also exist gravitationally not bound to a star – the result of it own molecular cloud collapse without a star or expulsion from a stellar system. One could specify gravitational expulsion however, it is possible that explosive events occur that cause the disintegration of a star and its binding gravity or creates such an impulse that a planet is thrusted out of a stellar system. Having an atmosphere certainly doesn’t work. Astronomers are already anticipating Mars or Earth-sized objects deep in the Oort cloud that could have no atmosphere – frozen out and also despite their size, not be able to “clear their neighborhood.”
An animation (above) of Kepler mission planet candidates compiled by Jeff Thorpe. Kepler and other exoplanet projects are revealing that the properties of planets – orbits, size, temperature, makeup – are all extreme. Does Pluto represent one of those extremes – the smallest of planets? (Credit: NASA/Kepler, Jeff Thorp)
The need to create a lower-end limit to what is a planet reached a near fever pitch with the discovery of a Trans-Nepturnian Object (TNO) in 2005 that is bigger than Pluto – Eris. Dr. Michael Brown of Caltech and his team led in the discovery of bright large KBOs. There was not just Eris but many of nearly the same size as Pluto. So without clause (c), one would be left with a definition for planet that could allow the count of planets in our Solar System to rise into the hundreds maybe even thousands. This would become a rather unmanageable problem; the number of planets rising year after year and never settled and with no means to make reasonable comparisons between planetary systems throughout our galaxy and even the Universe.
The book that tells the story of discovery – trans-Neptunian objects (TNO) that led to the downfall of Pluto from full planethood to that of a dwarf. The 2006 IAU decision was a pre-emptive strike to stave off a proliferation of planets in our system. It worked but “killed” Pluto. Did it have it coming? Dr. Brown also agrees that the present definition of planet is flawed and incomplete. (Photo Credits: Caltech/M.Brown)
Two more celestial body types follow that are proposed to round out the set.
moon: is a celestial body that a) orbits a (minor) planet and b) for which the barycenter of its orbit is below the surface of its parent (minor) planet.
This creates the possibility of a planet-moon system such that its barycenter is above the surface of the larger body. Pluto and Charon are the most prominent case in our Solar System. In such cases, if one body meets the criteria of a (minor)planet, then the other body can also be assessed to determine if it is also a (minor) planet and the pair as binary (minor) planets. If the primary body was a minor planet, it is possible that the barycenter could be above its surface but the secondary body does not meet all the criteria of a minor planet, specifically “differentiated interior”.
The definition of moon is compounded by the existence of, for example, asteroids with moons. For such objects, the smaller object is defined as a satellite.
Satellite: is a celestial body that a) orbits another celestial body, b) whose parent body is not a (minor) planet.
Another permissible term is moonlet which could be used to describe both very small moons such as those found in the Jovian and Saturn systems or a small body orbiting an asteroid or comet. Moonlet could replace satellite.
The discriminator between planet and moon is not mass but simply whether the celestial body orbits a (minor) planet and the barycenter resides inside the larger body. The definition of moon excludes the possibility of a planet orbiting another planet except in the special case of binary (minor) planet.
Defining a lower size limit to “Planet” is necessary to compare stellar systems and classify. A limit based on the body’s average surface pressure and temperature or the surface gravity could define a limit. While they could, they are not practical because of the extremes and diverse combinations of conditions. Strange objects would fall through the cracks.
Removing clause (c) – “has cleared the neighborhood around its orbit” – will avoid a future conflict such as a very low mass star with a plutoid-sized object or smaller, in a close orbit that has cleared its neighborhood.
Additionally, choosing to declare that Pluto becomes the “standard weight” that differentiates minor planet from planet sets a precedent. In an era in which computers measure and tally the state of our existence, setting this limit to include Pluto and return it as the ninth planet of our Solar System, is, in a small but significant way, a re-declaration of our humanity. Soon we will be challenged by artificial intelligence greater than ours; we are already have. Where will we stand our ground?
Forget about Pluto for a moment. Should Eris be our tenth planet? Like Pluto it has a prominent moon- Dysnomia. Human perception and conceptions of the Universe have shaped our view of the Solar System. The Ptolemaic system (Earth centered), Kepler’s Harmonic Spheres, even the fact that ten digits reside on our hands impact our impression of the Solar System (Photo Credits:NASA/ESA and M. Brown / Caltech)
The consequences of this proposed set of definitions, makes Ceres a minor planet and no longer an asteroid. Many trans-Neptunian objects discovered in this century become minor planets. Of the known TNOs only Pluto and Eris meets the criteria of planet.The dwarf planet Eris would become the tenth planet. Makemake, Sedna, Quaoar, Orcus, Haumea would be minor planets. By keeping Pluto a planet and defining it as the standard bearer, only one new planet must be declared. Surely, more will be found, very distant, in odd elliptical and tilted orbits. The count of planets in our solar system could rise by 10, 20 maybe 50 and perhaps this would make the definition untenable but maybe not. So be it. New Horizons will fly by a dwarf planet in July but this should mark the beginning of the end of the present set of definitions.
Three perspectives of a ten planet Solar System. No longer Earth centered, or with harmonic spheres but now with planets outside the ecliptic plane and growing. How many planets would be too many? (Credits: Wikimedia, T.Reyes)
This set of definitions defines a set of celestial bodies that consistently covers the spectrum of known bodies. There is the potential of exotic celestial objects that are spawned from cataclysmic events or from the unique conditions during the early epochs of the Universe or from remnants of old or dying stellar objects. Their discovery will likely trigger new or revised definitions but these definitions are a good working set for the time being. Ultimately, it is the decision of the IAU but the sharing of knowledge and the democratic processes that we cherish permits anyone to question and evaluate such definitions or proclamations.To all that share an interest in Pluto as or as not a planet raise your hand and be heard.
A video from 2014 by Kurz Gesagt describing the Pluto-Charon system. Is this a binary planet system or one of the “dwarf” variety?
My condolences to the friends and family of Tammy Plotner, the first regular contributing writer to Universe Today. Can’t we all relate to what drew Tammy to write about the Universe? She wrote outstanding articles for U.T.
One several images NASA's Dawn spacecraft took on approach to Ceres on Feb. 4, 2015 at a distance of about 90,000 miles (145,000 kilometers) from the dwarf planet. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
NASA’s Dawn spacecraft has acquired its latest and closest-yet snapshot of the mysterious dwarf planet world Ceres. These latest images, taken on Feb. 4, from a distance of about 90,000 miles (145,000 km) clearly show craters – including a couple with central peaks – and a clearer though still ambiguous view of that wild white spot that has so many of us scratching our heads as to its nature.
Get ready to scratch some more. The mystery spot has plenty of company.
Take a look at some still images I grabbed from the video which NASA made available today. In several of the photos, the white spot clearly looks like a depression, possibly an impact site. In others, it appears more like a rise or mountaintop. But perhaps the most amazing thing is that there appear to be not one but many white dabs and splashes on Ceres’ 590-mile-wide globe. I’ve toned the images to bring out more details:
Here the spot appears more like a depression. Frost? Ice? Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDAHere the white spot is at the asteroid’s left limb. You can also see lots of additional smaller spots that remind me of rayed lunar craters. Of course, they may be something else entirely. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDALook down along the lower limb to spot a crater with a cool central peak. Note also how many white spots are now visible on Ceres. The mystery spot is a little right of center in this view. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDAOur mystery white spot is further right of center. Is it a rise or a hole?Are the streaks rays for fresh material from an impact the way the lunar crater Tycho appears from Earth? Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDAYet another view of the mystery spot. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Animation made from images taken by Dawn on Feb. 4. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Now let’s take a look at an additional NASA animation of Ceres made using processed images. As the spot first rounds the limb it looks like a depression. But just before it disappears around the backside a pointed peak seems to appear. Intriguing, isn’t it?
