The latest report from NASA JPL on what’s happening with the Curiosity rover on Mars:
Curiosity performs the first investigation of active sand dunes on another planet. Studying the Bagnold Dunes on Mars will help scientists understand the physics of Martian dunes and how they move.
The Dawn probe investigating the asteroid and dwarf planet Ceres has moved its orbit closer to the surface and gotten better views of those famous bright areas at the bottom of some craters:
New Clues to Ceres’ Bright Spots and Origins
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In one study, scientists identify this bright material as a kind of salt. The second study suggests the detection of ammonia-rich clays, raising questions about how Ceres formed.
About the Bright Spots
Ceres has more than 130 bright areas, and most of them are associated with impact craters. Study authors, led by Andreas Nathues at Max Planck Institute for Solar System Research, Göttingen, Germany, write that the bright material is consistent with a type of magnesium sulfate called hexahydrite. A different type of magnesium sulfate is familiar on Earth as Epsom salt.
Nathues and colleagues, using images from Dawn’s framing camera, suggest that these salt-rich areas were left behind when water-ice sublimated in the past. Impacts from asteroids would have unearthed the mixture of ice and salt, they say.
“The global nature of Ceres’ bright spots suggests that this world has a subsurface layer that contains briny water-ice,” Nathues said.
A New Look at Occator
The surface of Ceres, whose average diameter is 584 miles (940 kilometers), is generally dark — similar in brightness to fresh asphalt — study authors wrote. The bright patches that pepper the surface represent a large range of brightness, with the brightest areas reflecting about 50 percent of sunlight shining on the area. But there has not been unambiguous detection of water ice on Ceres; higher-resolution data are needed to settle this question.
The inner portion of a crater called Occator contains the brightest material on Ceres. Occator itself is 60 miles (90 kilometers) in diameter, and its central pit, covered by this bright material, measures about 6 miles (10 kilometers) wide and 0.3 miles (0.5 kilometers) deep. Dark streaks, possibly fractures, traverse the pit. Remnants of a central peak, which was up to 0.3 miles (0.5 kilometers) high, can also be seen.
With its sharp rim and walls, and abundant terraces and landslide deposits, Occator appears to be among the youngest features on Ceres. Dawn mission scientists estimate its age to be about 78 million years old.
Study authors write that some views of Occator appear to show a diffuse haze near the surface that fills the floor of the crater. This may be associated with observations of water vapor at Ceres by the Herschel space observatory that were reported in 2014. The haze seems to be present in views during noon, local time, and absent at dawn and dusk, study authors write. This suggests that the phenomenon resembles the activity at the surface of a comet, with water vapor lifting tiny particles of dust and residual ice. Future data and analysis may test this hypothesis and reveal clues about the process causing this activity.
“The Dawn science team is still discussing these results and analyzing data to better understand what is happening at Occator,” said Chris Russell, principal investigator of the Dawn mission, based at the University of California, Los Angeles.
The Importance of Ammonia
In the second Nature study, members of the Dawn science team examined the composition of Ceres and found evidence for ammonia-rich clays. They used data from the visible and infrared mapping spectrometer, a device that looks at how various wavelengths of light are reflected by the surface, allowing minerals to be identified.
Ammonia ice by itself would evaporate on Ceres today, because the dwarf planet is too warm. However, ammonia molecules could be stable if present in combination with (i.e. chemically bonded to) other minerals.
The presence of ammoniated compounds raises the possibility that Ceres did not originate in the main asteroid belt between Mars and Jupiter, where it currently resides, but instead might have formed in the outer solar system. Another idea is that Ceres formed close to its present position, incorporating materials that drifted in from the outer solar system – near the orbit of Neptune, where nitrogen ices are thermally stable.
“The presence of ammonia-bearing species suggests that Ceres is composed of material accreted in an environment where ammonia and nitrogen were abundant. Consequently, we think that this material originated in the outer cold solar system,” said Maria Cristina De Sanctis, lead author of the study, based at the National Institute of Astrophysics, Rome.
In comparing the spectrum of reflected light from Ceres to meteorites, scientists found some similarities. Specifically, they focused on the spectra, or chemical fingerprints, of carbonaceous chondrites, a type of carbon-rich meteorite thought to be relevant analogues for the dwarf planet. But these are not good matches for all wavelengths that the instrument sampled, the team found. In particular, there were distinctive absorption bands, matching mixtures containing ammoniated minerals, associated with wavelengths that can’t be observed from Earth-based telescopes.
The scientists note another difference is that these carbonaceous chondrites have bulk water contents of 15 to 20 percent, while Ceres’ content is as much as 30 percent.
“Ceres may have retained more volatiles than these meteorites, or it could have accreted the water from volatile-rich material,” De Sanctis said.
The study also shows that daytime surface temperatures on Ceres span from minus 136 degrees to minus 28 degrees Fahrenheit (180 to 240 Kelvin). The maximum temperatures were measured in the equatorial region. The temperatures at and near the equator are generally too high to support ice at the surface for a long time, study authors say, but data from Dawn’s next orbit will reveal more details.
As of this week, Dawn has reached its final orbital altitude at Ceres, about 240 miles (385 kilometers) from the surface of the dwarf planet. In mid-December, Dawn will begin taking observations from this orbit, including images at a resolution of 120 feet (35 meters) per pixel, infrared, gamma ray and neutron spectra, and high-resolution gravity data.
Dawn’s mission is managed by the Jet Propulsion Laboratory for NASA. Dawn is a project of the directorate’s Discovery Program, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute are international partners on the mission team.
For a complete list of mission participants, visit: dawn.jpl.nasa.gov/mission
More information about Dawn is available at the following sites:
The Cassini Mission spacecraft has been imaging the Saturn system for 11 years now. Jon Keegan of the Wall Street Journal has compiled the 341,805 images taken by the and put them sequentially into a 3 hour and 48 minute video: Watch the entire Cassini mission image catalog as a movie – The Planetary Society
Caption:
341,805 images taken by Cassini’s Imaging Science Subsystem (ISS) from the Saturn EDR Data Sets (Volumes 1-93). This includes all of Cassini’s Photos from February 6, 2004 – September 15, 2015. Compiled and processed by The Wall Street Journal’s @JonKeegan.
NOTE: These raw, unedited sequences at times include rapid flashing. If you have photosensitive epilepsy, or a similar condition, this could trigger a physical reaction. Please use caution when watching this footage.
Source: NASA/JPL-Caltech/Space Science Institute
This video shows an abbreviated and annotated selection of the image collection:
The New Horizons probe will be slowly downloading images and data from its July flyby of Pluto over the next year. Yesterday the mission released the highest resolutions images yet obtained of the surface of Pluto.
New Horizons Returns the First of Its Very Best Images of Pluto
NASA’s New Horizons spacecraft has sent back the first few of a series of the sharpest views of Pluto it obtained during its July flyby – and this image sequence forms the best close-ups of Pluto that humans may see for decades.
Every week the piano-sized New Horizons spacecraft transmits data stored on its digital recorders from its flight through the Pluto system on July 14. These latest pictures are part of a sequence taken near New Horizons’ closest approach to Pluto, with resolutions of about 250-280 feet (77-85 meters) per pixel – revealing features less than half the size of a city block on the diverse surface of the distant planet. In these new images, New Horizons captured a wide variety of spectacular, cratered, mountainous and glacial terrains.
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The images being released today form a strip 50 miles (80 kilometers) wide trending from Pluto’s jagged horizon about 500 miles (800 kilometers) northwest of the informally named Sputnik Planum, across the al-Idrisi mountains, onto the shoreline of Sputnik and then across its icy plains.
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A video made from these images reveals amazing details on a world 3 billion miles away – as do individual close-ups taken from the wider swath. The images are six times better than the resolution of the global Pluto map New Horizons obtained, and five times better than the best images of Pluto’s cousin Triton, Neptune’s large moon, obtained by Voyager 2 in 1989.
Very Best Views of Pluto: This movie is composed of the sharpest views of Pluto that NASA’s New Horizons spacecraft obtained during its flyby of the distant planet on July 14, 2015. The pictures are part of a sequence taken near New Horizons’ closest approach to Pluto, with resolutions of about 250-280 feet (77-85 meters) per pixel – revealing features smaller than half a city block on Pluto’s diverse surface. The images include a wide variety of spectacular, cratered, mountainous and glacial terrains – giving scientists and the public alike a breathtaking, super-high resolution window on Pluto’s geology. Click for full caption – Click for the full image
“The mountains bordering Sputnik Planum are absolutely stunning at this resolution” added New Horizons science team member John Spencer. “The new details revealed here, particularly the crumpled ridges in the rubbly material surrounding several of the mountains, reinforce our earlier impression that the mountains are huge ice blocks that have been jostled and tumbled and somehow transported to their present locations.”
These images were made with the telescopic Long Range Reconnaissance Imager (LORRI) aboard New Horizons, in a timespan of about a minute centered on 11:36 UT on July 14 – just about 15 minutes before New Horizons’ closest approach to Pluto – from a range of just 10,000 miles (17,000 kilometers). They were obtained with an unusual observing mode; instead of working in the usual “point and shoot,” LORRI snapped pictures every three seconds while the Ralph/Multispectral Visual Imaging Camera (MVIC) aboard New Horizons was scanning the surface. This mode requires unusually short exposures to avoid blurring the images.
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New Horizons, speeding through deep space at more than 32,000 miles per hour, is approximately 104 million miles (167 million kilometers) beyond Pluto and 3.2 billion miles (5.2 billion kilometers) from Earth. All spacecraft systems are healthy.
New Horizons is part of NASA’s New Frontiers Program, managed by the agency’s Marshall Space Flight Center in Huntsville, Alabama. The Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, designed, built, and operates the New Horizons spacecraft and manages the mission for NASA’s Science Mission Directorate. The Southwest Research Institute leads the mission and mission science, payload operations, and encounter science planning.
At an American Astronomical Society (AAS) Planetary Sciences Meeting today, the New Horizons team brought a truckload of results to present from the probe’s flyby of the Pluto system. Copies of their presentation slides are available at: Science Results from the New Horizons Encounter with Pluto – Presentations – New Horizons.
An overview of the findings was released:
From possible ice volcanoes to geologically diverse surfaces to oddly behaving moons that could have formed through mergers of smaller moons, Pluto system discoveries continue to surprise scientists on NASA’s New Horizons mission team.
“The New Horizons mission has taken what we thought we knew about Pluto and turned it upside down,” said Jim Green, director of planetary science at NASA Headquarters in Washington. “It’s why we explore – to satisfy our innate curiosity and answer deeper questions about how we got here and what lies beyond the next horizon.”
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In one such discovery, New Horizons geologists have combined images of Pluto’s surface to make 3-D maps that indicate that two of Pluto’s most distinctive mountains could be cryovolcanoes—ice volcanoes that may have been active in the recent geological past.
The two cryovolcano candidates are large features measuring tens of miles (tens of kilometers) across and several miles or kilometers high. “These are big mountains with a large hole in their summit, and on Earth that generally means one thing—a volcano,” said Oliver White, New Horizons postdoctoral researcher with NASA’s Ames Research Center, Moffett Field, California. While their appearance is similar to volcanoes on Earth that spew molten rock, ice volcanoes on Pluto are expected to emit a somewhat melted slurry of substances such as water ice, nitrogen, ammonia, or methane on Pluto.
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If Pluto is proven to have volcanoes, it will provide an important new clue to its geologic and atmospheric evolution. “After all, nothing like this has been seen in the deep outer solar system,” said Jeffrey Moore, New Horizons Geology, Geophysics and Imaging team leader, also from NASA Ames.
Pluto’s Long History of Geologic Activity
Another of the more surprising findings from New Horizons is the wide range of surface ages found on Pluto, from ancient to intermediate to relatively young in geological terms. Crater counts used to determine surface unit ages indicate that Pluto has ancient surface areas dating to just after the formation of the planets, about 4 billion years ago. In addition, there’s a vast area that was geologically born “yesterday,” meaning it may have formed within the past 10 million years. This area – informally named Sputnik Planum – appears on the left side of Pluto’s “heart” and is completely impact-free in all images returned to date.
Scientists wondered if Sputnik Planum’s smooth, icy plains were an oddity; did a recent geological episode form the plains long after all other geologic activity ceased?
Apparently not. New data from crater counts reveal the presence of intermediate or “middle-aged” terrains on Pluto as well. This suggests that Sputnik Planum is not an anomaly—that Pluto has been geologically active throughout much of its more than 4-billion-year history. “We’ve mapped more than a thousand craters, which vary greatly in size and appearance,” said postdoctoral researcher Kelsi Singer, of the Southwest Research Institute (SwRI) in Boulder, Colorado. “Among other things, I expect cratering studies like these to give us important new insights into how this part of the solar system formed.”
Building Blocks of the Solar System
Crater counts are giving the New Horizons team insight into the structure of the Kuiper Belt itself. The dearth of smaller craters across Pluto and its large moon Charon indicate that the Kuiper Belt likely had fewer smaller objects than some models had predicted. This leads New Horizons scientists to doubt a longstanding model that all Kuiper Belt objects formed by accumulating much smaller objects of less than a mile wide. The absence of small craters on Pluto and Charon support other models theorizing that Kuiper Belt objects tens of miles across may have formed directly, at their current—or close to current—size.
In fact, the evidence that many Kuiper Belt objects could have been “born large” has scientists excited that New Horizons’ next potential target – the 30-mile-wide (40-50 kilometer wide) KBO named 2014 MU69 – which may offer the first detailed look at just such a pristine, ancient building block of the solar system.
Spinning, Merged Moons
The New Horizons mission is also shedding new light on Pluto’s fascinating system of moons and their unusual properties. For example, nearly every other moon in the solar system, including Earth’s moon, is in synchronous rotation, but not so of Pluto’s small moons. These small satellites are spinning much faster, with Hydra – the most distant moon – rotating an unprecedented 89 times during a single lap around Pluto. Scientists believe these spin rates could be chaotic (i.e., variable) because Charon exerts a strong torque that prevents each small moon from settling down into synchronous rotation, which means keeping one face toward the planet.
Most inner moons in the solar system keep one face pointed toward their central planet; this animation shows that certainly isn’t the case with the small moons of Pluto, which behave like spinning tops. Pluto is shown at center with, in order, from smaller to wider orbit: Charon, Styx, Nix, Kerberos and Hydra. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Another oddity of Pluto’s moons: scientists expected the satellites to wobble, but not to this degree. “Pluto’s moons are behaving like spinning tops,” said co-investigator Mark Showalter of the SETI Institute in Mountain View, California.
Images of Pluto’s four smallest satellites also indicate that several of them could have been born from mergers of two or more former moons, suggesting the presence of more moons at some point. “We suspect from this that Pluto had more moons in the past, in the aftermath of the big impact that also created Charon,” said Showalter.
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The New Horizons team is presenting new data at DPS that reveal Pluto’s upper atmosphere is significantly colder and therefore more compact than Earth-based models had indicated. As a result, scientists have discovered that Pluto’s atmospheric escape rate is thousands of times lower than had been thought. It now appears that Pluto’s atmosphere escapes by the same mechanism as do gases from the atmospheres of Earth and Mars – rather than the previously believed escape process that more resembled escape from cometary atmospheres.
New Horizons is part of NASA’s New Frontiers Program, managed by the agency’s Marshall Space Flight Center in Huntsville, Alabama. The Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, designed, built, and operates the New Horizons spacecraft and manages the mission for NASA’s Science Mission Directorate. The Southwest Research Institute leads the science mission, payload operations, and encounter science planning.
For more information on the New Horizons mission, including fact sheets, video and images, visit www.nasa.gov/newhorizons and pluto.jhuapl.edu.