The highest-resolution images yet obtained of Ceres’ alien terrain by NASA’s recently arrived Dawn orbiter spacecraft reveal that the mysterious pair of eye-like bright spots are actually comprised of a multitude of spots that may be “icy,” the science team tells AmericaSpace.
Spectral measurements from NASA’s just-released imagery of the closest-yet views of dwarf planet Ceres show that the most intriguing bright spots are “highly reflective material” and exhibit “spectrum resembling that expected for ice,” Chris Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles, told AmericaSpace.
“I know of nothing exactly like these spots anywhere,” Russell elaborated. “We are excited about these scientific surprises!”
The latest sequence of images of Ceres’ dauntingly mysterious bright spots show them to seemingly be sheets of many spots of water ice, and not just single huge patches. The duo of ice spots are located smack dab inside the middle of a 57-mile-wide (92 km) crater, situated in Ceres’ northern hemisphere.
Altogether, Ceres features a remarkable collection of perhaps 10 or more bright spots, with the brightest ones being the pair inside the crater.
The bright spots had not yet been resolved in prior images taken by the framing camera at further distances, during the Ceres approach and capture into orbit that took place March 6.
The bright patches of what appear for now to be ice are now much better resolved compared to all prior imagery captured at farther distances, and were taken by the Dawn spacecraft May 3 and 4, 2015.
The images were taken from a distance of 8,400 miles (13,600 kilometers) while the probe was in its first mapping orbit known as RC3, or the rotation characterization 3 mapping orbit.
The image resolution at RC3 is 0.8 mile (1.3 kilometers) per pixel.
AmericaSpace asked the PI, “What’s the best current hypothesis on the nature of the bright spots based on the data gathered so far?”
“The spectrum resembles that expected for ice. The simplest explanation is that they are ice,” Russell stated. “I expect that there will be more surprises.”
To date, Dawn has gathered several thousand images and millions of spectral measurements for the science team to analyze and scrutinize in making conclusions and constructing the science plan of action.
“So far we obtained about 2,500 pictures and about two million spectra,” Dr. Marc Rayman, Dawn’s mission director and chief engineer, based at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., told AmericaSpace.
“RC3 executed very well indeed.”
Given their extreme brightness, are the bright spots more reflective then expected for ice?
“The spots look to be no more reflective than we expect for ice,” Russell replied.
“But it is always possible at some level that a mechanism that we believe is improbable is responsible. The increasing resolution as we descend will be helpful in the final analysis.”
How do these two compare to the other bright areas?
“There are other small bright spots on the surface. But none as numerous in one area than those at 240 deg East in our preliminary coordinate system.”
Could they still possibly be icy cryovolcanoes?
“We don’t understand how the ice—if that is what it is—was produced. Except that it had to freeze at sometime. So, no mechanism is ‘ruled out’.”
Roughly how many individual spots are you seeing in each of the two areas?
“I think we should be careful in giving a count because the larger spots may break into many smaller ones when we get higher resolution,” Russell explained.
Do they still remain unlike anything seen before, or are there some types of analogs now that the team has had more to reflect?
“I know of nothing exactly like these spots anywhere. But there are some bright spots on some moons.”
Now that Dawn is spiraling down in altitude ever closer toward Ceres’ surface, the best results are yet to come over the course of the next year or more while Dawn actively investigates Ceres until at least June 2016—if all goes well.
Dawn just completed its first mapping orbit at RC3, composed of one 15-day full circle around Ceres while making new observations with its scientific instruments.
On May 9, the spacecraft powered on its ion engine to begin the month-long descent toward its second mapping orbit, known as the survey orbit, which it will enter June 6, according to NASA.
During the survey orbit phase, Dawn will circle Ceres about every three days at an altitude of 2,700 miles (4,400 kilometers)—three times closer than the RC3.
“During this phase, Dawn will comprehensively map the surface to begin unraveling Ceres’ geologic history and assess whether the dwarf planet is active,” say NASA officials.
As it spirals down, Dawn will pause twice to take images of Ceres.
“Our opnavs [imaging] during the spiral to survey start on May 16 and May 22,” Rayman told me.
And there is a big change coming in the look of the images. After Dawn reaches the survey orbit there won’t be any more images of the whole globe of Ceres because it will more than fill the camera view.
“From now on, Ceres will be larger than the camera field of view. As at Vesta, we will build up maps from higher resolution views of smaller areas,” Rayman explained.
Dawn is an international science mission run by NASA and equipped with a trio of science instruments from the U.S., 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).
The visible and infrared mapping spectrometer (VIR), provided by Italy, is an imaging spectrometer that examines Ceres in visible and infrared light.
Dawn made history in March when it simultaneously became the first probe from Earth to reach Ceres as well as the first spacecraft to orbit two extraterrestrial bodies.
It had previously visited Vesta. After achieving orbit in July 2011, Dawn became the first spacecraft from Earth to orbit a body in the main Asteroid Belt, located between Mars and Jupiter.
In sharp contrast to rocky Vesta, Ceres is an icy world.
Scientists believe that Ceres may harbor an ocean of subsurface liquid water as large in volume as the oceans of Earth, below a thick icy mantle, despite its small size—and thus could be a potential abode for life. Overall, Ceres is estimated to be about 25 percent water by mass.
Dawn’s images obtained thus far reveal Ceres to be a pockmarked world with craters of many sizes.
Ceres is a huge and mysterious alien world the size of Texas. It measures approximately 590 miles (950 kilometers) in diameter and is nearly round.
Russell has this new message for AmericaSpace readers:
“We really appreciate their interest in our mission and hope they are as excited as we have been about these scientific surprises. Since we are only just beginning our investigation, I expect that there will be more surprises. So please stick with us!”
Dawn was launched Sept, 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, Fla.
Stay tuned here for continuing updates on Dawns’ orbital capture and science mission at protoplanet Ceres!
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