This mosaic shows Ceres' Occator crater and surrounding terrain from an altitude of 915 miles (1,470 kilometers), as seen by NASA's Dawn spacecraft. Occator is about 60 miles (90 kilometers) across and 2 miles (4 kilometers) deep. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
The most dazzling views ever seen of dwarf planet Ceres and its mysterious bright spots are what’s on tap by year’s end as NASA’s amazing Dawn spacecraft starts a gradual but steep descent over the next two months to its lowest and final orbit around the bizarre icy body.
Engineers at NASA’s Jet Propulsion Laboratory (JPL) successfully fired up the probes exotic ion propulsion system to begin lowering Dawn’s orbital altitude to less than a quarter of what it has been for the past two months of intense mapping operations.
On Oct. 23, Dawn began a seven-week-long dive that uses ion thruster #2 to reduce the spacecrafts vantage point from 915 miles (1,470 kilometers) at the High Altitude Mapping Orbit (HAMO) down to less than 235 miles (380 kilometers) above Ceres at the Low Altitude Mapping Orbit (LAMO).
Dawn is slated to arrive at LAMO by mid-December, just in time to begin delivering the long awaiting Christmas treats.
Ceres has absolutely tantalized researchers far beyond their wildest expectations.
When Dawn arrives at LAMO it will be the culmination of an eight year interplanetary voyage that began with a blastoff on September 27, 2007 by a United Launch Alliance (ULA) Delta II Heavy rocket from Space Launch Complex-17B (SLC-17B) at Cape Canaveral Air Force Station, Florida.
LAMO marks Dawn’s fourth, lowest and final science orbit at Ceres where the highest resolution observations will be gathered and images from the framing camera will achieve a resolution of 120 feet (35 meters) per pixel.
Dawn’s low altitude mapping orbit LAMO. This shows how the orbit naturally shifts slightly (relative to the sun) during the three months of LAMO, starting in blue and ending in red. The spacecraft completes each revolution in 5.5 hours, and Ceres rotates in 9.1 hours, so Dawn will be able to view the entire surface. Credit: NASA/JPL
At LAMO, researchers hope to finally resolve the enduring mystery of the nature of the bright spots that have intrigued science and the general public since they were first glimpsed clearly early this year as Dawn was on its final approach to Ceres.
Dawn arrived in orbit this past spring on March 6, 2015.
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
The science team has just released a new mosaic of the brightest spots on Ceres found at Occator crater and the surrounding terrain – see above.
The images were taken from the HAMO altitude of 915 miles (1,470 kilometers) during the first of six mapping cycles. They have a resolution of 450 feet (140 meters) per pixel.
Occator measures about 60 miles (90 kilometers) across and 2 miles (4 kilometers) deep.
This image, made using images taken by NASA’s Dawn spacecraft during the mission’s High Altitude Mapping Orbit (HAMO) phase, shows Occator crater on Ceres, home to a collection of intriguing bright spots. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Because the spots are so bright they are generally overexposed. Therefore the team took two sets of images, with shorter and longer exposure times, to maximize the details of the interior of Occator.
“This view uses a composite of two images of Occator: one using a short exposure that captures the detail in the bright spots, and one where the background surface is captured at normal exposure.”
The bright spots at Occator crater remain the biggest Cerean mystery.
So far the imagery and other science data may point to evaporation of salty water from the interior as the source of the bright spots.
“Occasional water leakage on to the surface could leave salt there as the water would sublime,” Prof. Chris Russell, Dawn principal investigator told Universe Today exclusively.
“The big picture that is emerging is that Ceres fills a unique niche.”
“Ceres fills a unique niche between the cold icy bodies of the outer solar system, with their rock hard icy surfaces, and the water planets Mars and Earth that can support ice and water on their surfaces,” Russell, of the University of California, Los Angeles, told me.
Dawn has peeled back Ceres secrets as the spacecraft orbits lower and lower. Detailed measurements gathered to date have yielded global mineral and topographic maps from HAMO with the best resolution ever as the science team painstakingly stitched together the probes spectral and imaging products.
And the best is yet to come at LAMO.
At HAMO, Dawn’ instruments, including the Framing Camera and Visible and Infrared Spectrometer (VIR) were aimed at slightly different angles in each mapping cycle allowing the team to generate stereo views and construct 3-D maps.
“The emphasis during HAMO is to get good stereo data on the elevations of the surface topography and to get good high resolution clear and color data with the framing camera,” Russell explained.
This view from NASA’s Dawn spacecraft is a color-coded topographic map of Occator crater on Ceres. Blue is the lowest elevation, and brown is the highest. The crater, which is home to the brightest spots on Ceres, is approximately 56 miles (90 kilometers wide). Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Dawn is Earth’s first probe in human history to explore any dwarf planet, the first to explore Ceres up close and the first to orbit two celestial bodies.
The asteroid Vesta was Dawn’s first orbital target where it conducted extensive observations of the bizarre world for over a year in 2011 and 2012.
Ceres is a Texas-sized world, ranks as the largest object in the main asteroid belt between Mars and Jupiter, and may have a subsurface ocean of liquid water that could be hospitable to life.
This map-projected view of Ceres was created from images taken by NASA’s Dawn spacecraft during its high-altitude mapping orbit, in August and September, 2015. This color coded map can provide valuable insights into the mineral composition of the surface, as well as the relative ages of surface features. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
The mission is expected to last until at least March 2016, and possibly longer, depending upon fuel reserves.
“It will end some time between March and December,” Dr. Marc Rayman, Dawn’s chief engineer and mission director based at NASA’s Jet Propulsion Laboratory, Pasadena, California, told Universe Today.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
An artist’s conception shows NASA’s Dawn spacecraft flying above Ceres. This view incorporates actual imagery from the Dawn mission. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
This image, made using images taken by NASA's Dawn spacecraft during the mission's High Altitude Mapping Orbit (HAMO) phase, shows Occator crater on Ceres, home to a collection of intriguing bright spots. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
This image, made using images taken by NASA’s Dawn spacecraft during the mission’s High Altitude Mapping Orbit (HAMO) phase, shows Occator crater on Ceres, home to a collection of intriguing bright spots. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
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Since scientists believe that Ceres occupies a “unique niche” in the solar system and apparently harbors subsurface ice or liquid oceans, could the bright spots arise from subsurface “water leakage?” To find out Universe Today asked Dawn’s Principal Investigator and Chief Engineer.
“The big picture that is emerging is that Ceres fills a unique niche,” Prof. Chris Russell, Dawn principal investigator told Universe Today exclusively.
“Ceres fills a unique niche between the cold icy bodies of the outer solar system, with their rock hard icy surfaces, and the water planets Mars and Earth that can support ice and water on their surfaces,” said Russell, of the University of California, Los Angeles.
And with Dawn recently arrived at its second lowest science mapping orbit of the planned mission around icy dwarf planet Ceres in mid-August, the NASA spacecraft is capturing the most stunningly detailed images yet of those ever intriguing bright spots located inside Occator crater.
The imagery and other science data may point to evaporation of salty water as the source of the bright spots.
“Occasional water leakage on to the surface could leave salt there as the water would sublime,” Russell told me.
Circling the Lights of Occator crater on Ceres. This image, made using images taken by NASA’s Dawn spacecraft during the mission’s High Altitude Mapping Orbit (HAMO) phase and draped over a shape model, shows Occator crater on Ceres, home to a collection of intriguing bright spots. The image has been stretched by 1.5 times in the vertical direction to better illustrate the crater’s topography. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Dawn is Earth’s first probe to explore any dwarf planet and the first to explore Ceres up close. It was built by Orbital ATK.
To shed more light on what still remains rather mysterious even today, NASA has just released the best yet imagery, which was taken at Dawn’s High Altitude Mapping Orbit (HAMO) phase and they raise as many questions as they answer.
Occator has captured popular fascination world-wide because the 60 miles (90 kilometers) diameter crater is rife with the alien bodies brightest spots and whose nature remains elusive to this day, over half a year after Dawn arrived in orbit this past spring on March 6, 2015.
The new imagery from Dawn’s current HAMO mapping orbit was taken at an altitude of just 915 miles (1,470 kilometers). They provide about three times better resolution than the images captured from its previous orbit in June, and nearly 10 times better than in the spacecraft’s initial orbit at Ceres in April and May, says the team.
So with the new HAMO orbit images in hand, I asked the team what’s the latest thinking on the bright spots nature?
Initially a lot of speculation focused on water ice. But the scientists opinions have changed substantially as the data pours in from the lower orbits and forced new thinking on alternative hypotheses – to the absolute delight of the entire team!
“When the spots appeared at first to have an albedo approaching 100%, we were forced to think about the possibility of [water] ice being on the surface,” Russell explained.
“However the survey data revealed that the bright spots were only reflecting about 50% of the incoming light.”
“We did not like the ice hypothesis because ice sublimes under the conditions on Ceres surface. So we were quite relieved by the lower albedo.”
“So what could be 50% reflective? If we look at Earth we find that when water evaporates on the desert it leaves salt which is reflective. We know from its density that water or ice is inside Ceres.”
“So the occasional water leakage on to the surface could leave salt there as the water would sublime even faster than ice.”
At this time no one knows how deep the potential ice deposit or water reservoir sources of the “water leakage” reside beneath the surface, or whether the bright salt spots arose from past or current activity and perhaps get replenished or enlarged over time. To date there is no evidence showing plumes currently erupting from the Cerean surface.
Video Caption: Circling Occator Crater on Ceres. This animation, made using data from NASA’s Dawn spacecraft, shows the topography of Occator crater on Ceres. Credits: Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI
Dawn is an international science mission and equipped with a trio of state of the art science instruments from Germany, Italy and the US. They will elucidate the overall elemental and chemical composition and nature of Ceres, its bright spots and other wondrous geological features like the pyramidal mountain object.
I asked the PI and Chief Engineer to explain specifically how and which of the instruments is the team using right now at HAMO to determine the bright spots composition?
“The instruments that will reveal the composition of the spots are the framing camera [from Germany], the infrared spectrometer, and the visible spectrometer [both from the VIR instrument from Italy], replied Dr. Marc Rayman, Dawn’s chief engineer and mission director based at NASA’s Jet Propulsion Laboratory, Pasadena, California.
“Dawn arrived in this third mapping orbit [HAMO] on Aug. 13. It began this third mapping phase on schedule on Aug. 17.”
But much work remains to gather and interpret the data and discern the identity of which salts are actually present on Ceres.
“While salts of various sorts have the right reflectance, they are hard to distinguish from one another in the visible,” Russell elaborated to Universe Today.
“That is one reason VIR is working extra hard on the IR spectrum. Scientists are beginning to speculate on the salts. And to think about what salts could be formed in the interior.”
“That is at an early stage right now,” Russell stated.
“I know of nothing exactly like these spots anywhere. We are excited about these scientific surprises!”
Occator crater lies in Ceres northern hemisphere.
“There are other lines of investigation besides direct compositional measurement that will provide insight into the spots, including the geological context,” Rayman told Universe Today.
Each of Dawn’s two framing cameras is also outfitted with a wheel of 7 color filters, explained Joe Makowski, Dawn program manager from Orbital ATK, in an interview.
Different spectral data is gathered using the different filters which can be varied during each orbit.
“So far Dawn has completed 2 mapping orbit cycles of the 6 cycles planned at HAMO.”
Each HAMO mapping orbit cycle lasts 11 days and consists of 14 orbits lasting 19 hours each. Ceres is entirely mapped during each of the 6 cycles. The third mapping cycle just started on Wednesday, Sept. 9.
The instruments will be aimed at slightly different angle in each mapping cycle allowing the team to generate stereo views and construct 3-D maps.
“The emphasis during HAMO is to get good stereo data on the elevations of the surface topography and to get good high resolution clear and color data with the framing camera,” Russell explained.
“We are hoping to get lots of VIR IR data to help understand the composition of the surface better.”
“Dawn will use the color filters in its framing camera to record the sights in visible and infrared wavelengths,” notes Rayman.
“Dawn remains at HAMO until October 23. Then it begins thrusting with the ion propulsion thrusters to reach its lowest mapping orbit named LAMO [Low Altitude Mapping Orbit],” Makowski told me.
“Dawn will arrive at LAMO on December 15, 2015.”
That’s a Christmas present we can all look forward to with glee!
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
What is the teams reaction, interplay and interpretation regarding the mountains of new data being received from Dawn? How do the geologic processes compare to Earth?
“Dawn has transformed what was so recently a few bright dots into a complex and beautiful, gleaming landscape,” says Rayman. “Soon, the scientific analysis will reveal the geological and chemical nature of this mysterious and mesmerizing extraterrestrial scenery.”
“We do believe we see geologic processes analogous to those on Earth – but with important Cerean twists,” Russell told me.
“However we are at a point in the mission where conservative scientists are interpreting what we see in terms of familiar processes. And the free thinkers are imagining wild scenarios for what they see.”
“The next few weeks (months?) will be a time where the team argues amongst themselves and finds the proper compromise between tradition and innovation,” Russell concluded elegantly.
Among the highest features seen on Ceres so far is a mountain about 4 miles (6 kilometers) high, which is roughly the elevation of Mount McKinley in Alaska’s Denali National Park. Vertical relief has been exaggerated by a factor of five to help understand the topography. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/LPI
A batch of new results from Dawn at Ceres are expected to be released during science presentations at the European Planetary Science Congress 2015 being held in Nantes, France from 27 September to 2 October 2015.
The Dawn mission is expected to last until at least March 2016, and possibly longer, depending upon fuel reserves.
“It will end some time between March and December,” Rayman told me.
The science objectives in the LAMO orbit could be achieved as soon as March. But the team wants to extend operations as long as possible, perhaps to June or beyond, if the spacecraft remains healthy and has sufficient hydrazine maneuvering fuel and NASA funding to operate.
“We expect Dawn to complete the mission objectives at Ceres by March 2016. June is a the programmatic milestone for end of the nominal mission, effectively a time margin,” Makowski told Universe Today.
“The team is working to a well-defined exploration plan for Ceres, which we expect to accomplish by March, if all goes well.”
“At launch Dawn started with 45 kg of hydrazine. It has about 21 kg of usable hydrazine onboard as of today.”
“We expect to use about 15 kg during the nominal remaining mission,” Makowski stated.
Therefore Dawn may have roughly 5 kg or so of hydrazine fuel for any extended mission, if all goes well, that may eventually be approved by NASA. Of course NASA’s budget depends also on what is approved by the US Congress.
The intriguing brightest spots on Ceres lie in a crater named Occator, which is about 60 miles (90 kilometers) across and 2 miles (4 kilometers) deep. Vertical relief has been exaggerated by a factor of five. Exaggerating the relief helps scientists understand and visualize the topography much more easily, and highlights features that are sometimes subtle. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/LPI
Dawn was launched on September 27, 2007 by a United Launch Alliance (ULA) Delta II Heavy rocket from Space Launch Complex-17B (SLC-17B) at Cape Canaveral Air Force Station, Florida.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
Dawn launch on September 27, 2007 by a United Launch Alliance Delta II Heavy rocket from Cape Canaveral Air Force Station, Florida. Credit: Ken Kremer/kenkremer.com
