Hubble captures vivid auroras in Jupiter’s atmosphere

ESA - Hubble Space Telescope logo.

30 June 2016

Astronomers are using the NASA/ESA Hubble Space Telescope to study auroras — stunning light shows in a planet’s atmosphere — on the poles of the largest planet in the Solar System, Jupiter. This observation programme is supported by measurements made by NASA’s Juno spacecraft, currently on its way to Jupiter.

Auroras on Jupiter

Jupiter, the largest planet in the Solar System, is best known for its colourful storms, the most famous being the Great Red Spot. Now astronomers have focused on another beautiful feature of the planet, using the ultraviolet capabilities of the NASA/ESA Hubble Space Telescope.

The extraordinary vivid glows shown in the new observations are known as auroras [1]. They are created when high energy particles enter a planet’s atmosphere near its magnetic poles and collide with atoms of gas. As well as producing beautiful images, this programme aims to determine how various components of Jupiter’s auroras respond to different conditions in the solar wind, a stream of charged particles ejected from the Sun.

Timelapse of Jupiter’s auroras

This observation programme is perfectly timed as NASA’s Juno spacecraft is currently in the solar wind near Jupiter and will enter the orbit of the planet in early July 2016. While Hubble is observing and measuring the auroras on Jupiter, Juno is measuring the properties of the solar wind itself; a perfect collaboration between a telescope and a space probe [2].

“These auroras are very dramatic and among the most active I have ever seen”, says Jonathan Nichols from the University of Leicester, UK, and principal investigator of the study. “It almost seems as if Jupiter is throwing a firework party for the imminent arrival of Juno.”

To highlight changes in the auroras Hubble is observing Jupiter daily for around one month. Using this series of images it is possible for scientists to create videos that demonstrate the movement of the vivid auroras, which cover areas bigger than the Earth.

Timelapse of Jupiter’s auroras (2)

Not only are the auroras huge, they are also hundreds of times more energetic than auroras on Earth. And, unlike those on Earth, they never cease. Whilst on Earth the most intense auroras are caused by solar storms — when charged particles rain down on the upper atmosphere, excite gases, and cause them to glow red, green and purple — Jupiter has an additional source for its auroras.

The strong magnetic field of the gas giant grabs charged particles from its surroundings. This includes not only the charged particles within the solar wind but also the particles thrown into space by its orbiting moon Io, known for its numerous and large volcanos.

The new observations and measurements made with Hubble and Juno will help to better understand how the Sun and other sources influence auroras. While the observations with Hubble are still ongoing and the analysis of the data will take several more months, the first images and videos are already available and show the auroras on Jupiter’s north pole in their full beauty.

Hubble orbiting Earth

Notes:

[1] Jupiter’s auroras were first discovered by the Voyager 1 spacecraft in 1979. A thin ring of light on Jupiter's nightside looked like a stretched-out version of our own auroras on Earth. Only later on was it discovered that the auroras were best visible in the ultraviolet.

[2] This is not the first time astronomers have used Hubble to observe the auroras on Jupiter, nor is it the first time that Hubble has cooperated with space probes to do so. In 2000 the NASA/ESA/ASI Cassini spacecraft made its closest approach to Jupiter and scientists used this opportunity to gather data and images about the auroras simultaneously from Cassini and Hubble (heic0009). In 2007 Hubble obtained images in support of its sister NASA Mission New Horizons which used Jupiter's gravity for a manoeuvre on its way to Pluto (opo0714a).
More information

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

Links:

Images of Hubble: http://www.spacetelescope.org/images/archive/category/spacecraft/

Link to hubblesite release: http://hubblesite.org/newscenter/archive/releases/2016/24/

Juno mission webpage: https://www.nasa.gov/mission_pages/juno/overview/index.html

NASA/ESA/ASI Cassini spacecraft: http://sci.esa.int/cassini-huygens/

NASA Mission New Horizons: http://www.nasa.gov/mission_pages/newhorizons/main/index.html

heic0009: https://www.spacetelescope.org/news/heic0009/

opo0714a: https://www.spacetelescope.org/images/opo0714a/

For more information about the Hubble Space Telescope, visit:

http://hubblesite.org/
http://www.nasa.gov/hubble
https://www.spacetelescope.org/

Image, Videos, Text, Credits: NASA, ESA, J. Nichols.

Best regards, Orbiter.ch

Rosetta finale set for 30 September

ESA - Rosetta Mission patch.

30 June 2016

Rosetta is set to complete its mission in a controlled descent to the surface of its comet on 30 September.

The mission is coming to an end as a result of the spacecraft’s ever-increasing distance from the Sun and Earth. It is heading out towards the orbit of Jupiter, resulting in significantly reduced solar power to operate the craft and its instruments, and a reduction in bandwidth available to downlink scientific data.

Rosetta approaching comet

Combined with an ageing spacecraft and payload that have endured the harsh environment of space for over 12 years – not least two years close to a dusty comet – this means that Rosetta is reaching the end of its natural life.

Unlike in 2011, when Rosetta was put into a 31-month hibernation for the most distant part of its journey, this time it is riding alongside the comet. Comet 67P/Churyumov-Gerasimenko’s maximum distance from the Sun (over 850 million km) is more than Rosetta has ever journeyed before. The result is that there is not enough power at its most distant point to guarantee that Rosetta’s heaters would be able to keep it warm enough to survive.

Instead of risking a much longer hibernation that is unlikely to be survivable, and after consultation with Rosetta’s science team in 2014, it was decided that Rosetta would follow its lander Philae down onto the comet.

Where will Rosetta be on 30 September?

The final hours of descent will enable Rosetta to make many once-in-a-lifetime measurements, including very-high-resolution imaging, boosting Rosetta’s science return with precious close-up data achievable only through such a unique conclusion.

Communications will cease, however, once the orbiter reaches the surface, and its operations will then end.

“We’re trying to squeeze as many observations in as possible before we run out of solar power,” says Matt Taylor, ESA Rosetta project scientist.  “30 September will mark the end of spacecraft operations, but the beginning of the phase where the full focus of the teams will be on science. That is what the Rosetta mission was launched for and we have years of work ahead of us, thoroughly analysing its data.”

Rosetta’s operators will begin changing the trajectory in August ahead of the grand finale such that a series of elliptical orbits will take it progressively nearer to the comet at its closest point.

Close-up view of the comet

“Planning this phase is in fact far more complex than it was for Philae’s landing,” says Sylvain Lodiot, ESA Rosetta spacecraft operations manager. “The last six weeks will be particularly challenging as we fly eccentric orbits around the comet – in many ways this will be even riskier than the final descent itself.

“The closer we get to the comet, the more influence its non-uniform gravity will have, requiring us to have more control on the trajectory, and therefore more manoeuvres – our planning cycles will have to be executed on much shorter timescales.” 

A number of dedicated manoeuvres in the closing days of the mission will conclude with one final trajectory change at a distance of around 20 km about 12 hours before impact, to put the spacecraft on its final descent.

The region to be targeted for Rosetta’s impact is still under discussion, as spacecraft operators and scientists examine the various trade-offs involved, with several different trajectories being examined.

Broadly speaking, however, it is expected that impact will take place at about 50 cm/s, roughly half the landing speed of Philae in November 2014.

Commands uploaded in the days before will automatically ensure that the transmitter as well as all attitude and orbit control units and instruments are switched off upon impact, to fulfill spacecraft disposal requirements.

In any case, Rosetta’s high-gain antenna will very likely no longer be pointing towards Earth following impact, making any potential communications virtually impossible.

A challenging environment

In the meantime, science will continue as normal, although there are still many risks ahead. Last month, the spacecraft experienced a ‘safe mode’ while only 5 km from the comet as a result of dust confusing the navigation system. Rosetta recovered, but the mission team cannot rule out this happening again before the planned end of the mission.

“Although we’ll do the best job possible to keep Rosetta safe until then, we know from our experience of nearly two years at the comet that things may not go quite as we plan and, as always, we have to be prepared for the unexpected,” cautions Patrick Martin, ESA Rosetta’s mission manager.

“This is the ultimate challenge for our teams and for our spacecraft, and it will be a very fitting way to end the incredible and successful Rosetta mission.”

Notes for Editors:

Details regarding the end of mission scenario are subject to change. Further information will be announced once available.

Background information on ending Rosetta’s mission on the comet was published on the blog last year: From one comet landing to another – planning Rosetta's grand finale: http://blogs.esa.int/rosetta/2015/11/12/from-one-comet-landing-to-another-planning-rosettas-grand-finale/

Related article:

Rosetta safe mode 5 km from comet
http://orbiterchspacenews.blogspot.ch/2016/06/rosetta-safe-mode-5-km-from-comet.html

Related links:

Comet viewer tool: http://sci.esa.int/comet-viewer/

Where is Rosetta?: http://sci.esa.int/where_is_rosetta/

For more information about Rosetta mission, visit: http://www.esa.int/Our_Activities/Space_Science/Rosetta

Rosetta overview: http://www.esa.int/Our_Activities/Space_Science/Rosetta_overview

Rosetta in depth: http://sci.esa.int/rosetta

Images, Text, Credits: ESA/ATG medialab; Comet image: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0/ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA/ESA/Markus Bauer/Matt Taylor/Sylvain Lodiot/Patrick Martin.

Best regards, Orbiter.ch

Highly impactful: 10 facts about ESA’s Asteroid Impact Mission

ESA - AIM Mission logo.

30 June 2016

AIM and CubeSats watch impact

Europe’s proposed Asteroid Impact Mission is set to become humanity’s first mission to a double asteroid, and ESA’s first to a small body since Rosetta put down its lander on Comet 67P/Churyumov–Gerasimenko. Here are 10 key facts:

1. AIM has a trio of goals: to demonstrate key technologies for future deep-space missions, to investigate asteroid deflection techniques for planetary defence, and to revolutionise scientific understanding of asteroids.

2. AIM will have a ringside seat for the collision of a separate NASA spacecraft called DART with the asteroid’s tiny moon, gathering invaluable data that would help save Earth from impacts in the future should a real deflection mission be needed. These two ESA & NASA missions are collectively called the Asteroid Impact & Deflection Assessment (AIDA) mission.

The AIM spacecraft

3. AIM is a mission in a hurry. It must be built and ready to fly for a firm October/–November 2020 launch window in order to reach the Didymos binary asteroid system by June 2022, coinciding with Didymos’s exceptionally close approach to Earth.

4. AIM will perform detailed surface and internal structure investigations of the smaller 163- m- diameter ‘Didymoon’ in orbit around the 775- m diameter main asteroid both before and after the DART impact, to assess changes in its condition as well as its orbit. The closest precedent to this collision would be the 2005 impact strike of NASA’s Deep Impact probe with Comet Tempel 1, but that comet was a mountain-sized 6 km across, whereas Didymoon is only the size of the Great Pyramid of Giza.

Mascot-2 lander model

5. AIM’s instruments currently under study include a high-resolution visible imager, infrared imager, and high- and low-frequency radars, the former to build up a 10- cm-resolution surface map, the latter to sound deep beneath the surface of the asteroid.

6. The mission is designed to carry a microlander called Mascot-2, based on its twin Mascot-1 currently flying on-board Japan’s Hayabusa-2. Powered by a solar array, Mascot-2 would image the surface in visible and infrared light, and beam radar signals through the asteroid for its AIM mothership to pick up on the other side. In case of a landing in a non-illuminated area, a ‘mobility mechanism’ would let the shoebox-sized microlander jump to another location.

AIM mission objectives

7. AIM will also carry Europe’s first deep-space CubeSats. Several concepts being investigated would all contribute and complement AIM’s objectives with additional close-up measurements. Final selection will be made in January 2017.

8. Intended to be launched on Soyuz or the maiden flight of the Ariane 6 rocket, AIM will measure just 1.4 x 1.4 x 1.9 m (with solar arrays stowed). With a maximum mass of 835 kg at launch and about the size of a large office desk, AIM is much more compact than the lorry-sized Rosetta.

AIM mission objectives

9. AIM will return science data to Earth from deep- space using an ambitious long-distance optical communications system, which would also double as an altimeter and ‘laser radar’ lidar mapper for scientific use, combined with a novel ‘holographic’ modulated metasurface antenna.

10. The mission, set to be presented for approval by European space ministers in December, will demonstrate various key technologies for follow-on deep space and resource utilisation missions, including inter-satellite links between AIM and its microlander and CubeSats, as well as advanced spacecraft navigation and guidance systems to allow semi-autonomous low-gravity landing and proximity operations around Didymoon.

Related articles and links:

Work begins on ESA's part of planetary defence test:
http://orbiterchspacenews.blogspot.ch/2015/04/work-begins-on-esas-part-of-planetary.html

Design begins for ESA's Asteroid Impact Mission:
http://orbiterchspacenews.blogspot.ch/2015/04/design-begins-for-esas-asteroid-impact.html

Asteroid Impact & Deflection Assessment (AIDA) mission:
http://www.esa.int/Our_Activities/Space_Engineering_Technology/Asteroid_Impact_Mission/Asteroid_Impact_Deflection_Assessment_mission

AIM has a trio of goals: http://www.esa.int/Our_Activities/Space_Engineering_Technology/Asteroid_Impact_Mission/Asteroid_Impact_Mission2

Didymos binary asteroid system by June 2022: http://www.esa.int/Our_Activities/Space_Engineering_Technology/Asteroid_Impact_Mission/Mission_profile

AIM’s instruments currently under study: http://www.esa.int/Our_Activities/Space_Engineering_Technology/Asteroid_Impact_Mission/Instruments

Mascot-2: http://www.esa.int/spaceinimages/Images/2016/05/Mascot-2_lander_model

Europe’s first deep-space CubeSats - CubeSat companions for ESA’s asteroid mission:
http://orbiterchspacenews.blogspot.ch/2015/11/cubesat-companions-for-esas-asteroid.html

Long-distance optical communications system - AIMing a light across millions of kilometres:
http://orbiterchspacenews.blogspot.ch/2015/10/aiming-light-across-millions-of.html

Robot arm simulates close approach of ESA’s asteroid mission:
http://orbiterchspacenews.blogspot.ch/2015/12/robot-arm-simulates-close-approach-of.html

AIDA science community: https://www-n.oca.eu/michel/AIDA/

NEO Space Mission Studies: http://www.esa.int/Our_Activities/Space_Engineering_Technology/NEO

Images, Text, Credits: ESA/ScienceOffice.org/DLR.


Best regards, Orbiter.ch

El Niño Could Drive Intense Season for Amazon Fires

ISS - International Space Station patch / NASA & DLR - GRACE Mission logo.

June 29, 2016

The long-lasting effects of El Niño are projected to cause an intense fire season in the Amazon, according to the 2016 seasonal fire forecast from scientists at NASA and the University of California, Irvine.

Image above: The smoke from multiple fires in the Mato Grosso region of Brazil rises over forested and deforested areas in this astronaut photograph taken from the International Space Station on Aug. 19, 2014. Image Credit: NASA.

El Niño conditions in 2015 and early 2016 altered rainfall patterns around the world.  In the Amazon, El Niño reduced rainfall during the wet season, leaving the region drier at the start of the 2016 dry season than any year since 2002, according to NASA satellite data.

Wildfire risk for the dry season months of July to October this year now exceeds fire risk in 2005 and 2010, drought years when wildfires burned large areas of Amazon rainforest, said Doug Morton, an Earth scientist at NASA’s Goddard Space Flight Center who helped create the fire forecast.

"Severe drought conditions at the start of the dry season set the stage for extreme fire risk in 2016 across the southern Amazon," Morton said.

Image above: On a scale of zero to 100, the risk of severe fire activity in July, August and September is high for six states in Braxil (Acre, Amazonas, Maranhao, Mato Grosso, Para and Rondonia), three departments in Bolivia (El Beni, Pando, and Santa Cruz), and one country (Peru). Image Credits: Yang Chen, University of California, Irvine.

The Amazon fire forecast uses the relationship between climate and active fire detections from NASA satellites to predict fire season severity during the region’s dry season. Developed in 2011 by scientists at University of California, Irvine and NASA’s Goddard Space Flight Center, the forecast model is focused particularly on the link between sea surface temperatures and fire activity. Warmer sea surface temperatures in the tropical Pacific (El Niño) and Atlantic oceans shift rainfall away from the Amazon region, increasing the risk of fires during dry season months.

The team also uses data on terrestrial water storage from the joint NASA/German Aerospace Center (DLR) Gravity Recovery and Climate Experiment (GRACE) mission to follow changes in groundwater during the dry season. GRACE measurements serve as a proxy for the dryness of soils and forests.

The NASA and UC-Irvine scientists have worked with South American official and scientists to make them aware of the forecast in recent years. Liana Anderson, a Brazilian scientist from the National Center for Monitoring and Early Warning of Natural Disasters (CEMADEN), said that “fire forecasts three to six months before peak fire activity are important to identify areas with higher fire probability for integrated planning in support of local actions.”

For 2016, El Niño-driven conditions are far drier than 2005 and 2010 – the last years when the region experienced drought. The team has also developed a web tool to track the evolution of the Amazon fire season in near real time. Estimated fire emissions from each forecast region are updated daily, based on the relationship between active fire detections – made by the Moderate resolution Imaging Spectroradiometer (MODIS) instrument on NASA's Terra satellite – and fire emissions data from the Global Fire Emissions Database (GFED) in previous years. So far, however, the region has seen more fires to date than those years, another indicator that aligns with the fire severity forecast.

Graphics above: An analysis of data from the Gravity Recovery and Climate Experiment (GRACE) satellite mission shows greater soil water deficits in 2016 than previous drought years with high Amazon fire activity. Graphics Credits: Yang Chen, University of California, Irvine.

"When trees have less moisture to draw upon at the beginning of the dry season, they become more vulnerable to fire, and evaporate less water into the atmosphere," said UC-Irvine scientist Jim Randerson, who collaborated with UC-Irvine scientist Yang Chen on building the forecast model. "This puts millions of trees under stress and lowers humidity across the region, allowing fires to grow bigger than they normally would."

Fires in the Amazon have local, regional, and long-distance impacts. Agricultural fires that escape their intended boundaries can damage neighboring croplands and Amazon forests. Even slow-moving forest fires cause severe forest degradation, as Amazon rainforest trees are not adapted to fire. Together, intentional fires for agricultural management, deforestation, and wildfires generate massive smoke plumes that degrade regional air quality, exacerbating problems with asthma and respiratory illness. Smoke from Amazon fires eventually flows south and east over major urban centers in southern Brazil, including São Paulo and Rio de Janeiro, contributing to air quality concerns.

While scientists have been working with South American officials to broadcast the results of the fire forecasts and increase awareness of fire risk, they also said that the work could lead to better wildfire forecasts in other regions of the world. The team recently identified 9 regions outside the Amazon where fire season risk can also be forecast 3-6 months ahead of peak fire activity. It may be possible to build operational seasonal fire forecasts for much of Central America and for many countries in Southeast Asia, Randerson said.

Related links:

GRACE (Gravity Recovery And Climate Experiment): http://www.nasa.gov/mission_pages/Grace/index.html

Amazon fire forecast: http://www.ess.uci.edu/~amazonfirerisk/ForecastWeb/SAMFSS2016.html

Web tool to track the evolution of the Amazon fire season in near real time: http://globalfiredata.org/updates.html

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html

Images (mentioned), Text, Credits: NASA Goddard Space Flight Center/Patrick Lynch/Lynn Jenner.

Greetings, Orbiter.ch

NASA's Juno Peers Inside a Giant

NASA - JUNO Mission logo.

June 29, 2016

NASA's Juno spacecraft will make its long anticipated arrival at Jupiter on July 4.  Coming face-to-face with the gas giant, Juno will begin to unravel some of the greatest mysteries surrounding our solar system's largest planet, including the origin of its massive magnetosphere.

Magnetospheres are the result of a collision between a planet's intrinsic magnetic field and the supersonic solar wind. Jupiter's magnetosphere – the volume carved out in the solar wind where the planet’s magnetic field dominates –extends up to nearly 2 million miles (3 million kilometers). If it were visible in the night sky, Jupiter's magnetosphere would appear to be about the same size as Earth’s full moon. By studying Jupiter's magnetosphere, scientists will gain a better understanding about how Jupiter's magnetic field is generated. They also hope to determine whether the planet has a solid core, which will tell us how Jupiter formed during the earliest days of our solar system.

Exploring Jupiter's Magnetic Field

Video above: NASA is sending the Juno spacecraft to Jupiter, to peer beneath its cloudy surface and explore the giant planet's structure and magnetic field. Juno's twin magnetometers, built at Goddard Space Flight Center, will give scientists their first look within Jupiter at the powerful dynamo that drives its magnetic field.

In order to look inside the planet, the science team equipped Juno with a pair of magnetometers. The magnetometers, which were designed and built by an in-house team of scientists and engineers at NASA's Goddard Space Flight Center in Greenbelt, Maryland, will allow scientists to map Jupiter's magnetic field with high accuracy and observe variations in the field over time.

"The best way to think of a magnetometer is like a compass," said Jack Connerney, deputy principal investigator and head of the magnetometer team at Goddard. "Compasses record the direction of a magnetic field. But magnetometers expand on that capability and record both the direction and magnitude of the magnetic field."

The magnetometer sensors rest on a boom attached to one of the solar arrays, placing them about 40 feet (12 meters) from the body of the spacecraft. This helps ensure that the rest of the spacecraft does not interfere with the magnetometer.

However, the sensor orientation changes in time with the mechanical distortion of the solar array and boom resulting from the extremely cold temperatures of deep space. This distortion would limit the accuracy of the magnetometer measurements if not measured.

To ensure that the magnetometers retain their high accuracy, the team paired the instruments with a set of four cameras. These cameras measure the distortion of the magnetometer sensors in reference to the stars to determine their orientation.

"This is our first opportunity to do very precise, high-accuracy mapping of the magnetic field of another planet," Connerney said. "We are going to be able to explore the entire three-dimensional space around Jupiter, wrapping Jupiter in a dense net of magnetic field observations completely covering the sphere."

Image above: This artist's rendering shows NASA's Juno spacecraft orbiting Jupiter. Image Credit: NASA/JPL-Caltech.

One of the mysteries the team hopes to answer is how Jupiter's magnetic field is generated. Scientists expect to find similarities between Jupiter's magnetic field and that of Earth.

Magnetic fields are produced by what are known as dynamos — convective motion of electrically conducting fluid inside planets. As a planet rotates, the electrically susceptible liquid swirls around and drives electric currents, inducing a magnetic field. Earth's magnetic field is generated by liquid iron in the planet's core.

"But with Jupiter, we don't know what material is producing the planet's magnetic field,” said Jared Espley, Juno program scientist for NASA Headquarters, Washington. “What material is present and how deep down it lies is one of the questions Juno is designed to answer."

The observations made by Juno's magnetometers will also add to our understanding of Earth's dynamo, the source of our planet’s magnetic field, which lies deep beneath a magnetized layer of rocks and iron.

Imagine Earth's crust strewn with refrigerator magnets as you try to peer beneath the surface to observe the dynamo. The magnetization of Earth's crust will skew your measurements of the magnetic field.

"One of the reasons that the Juno mission is so exciting is because we can map Jupiter’s magnetic field without having to look through the crustal magnetic fields, which behave like a jumble of refrigerator magnets," Connerney said. "Jupiter has a gaseous envelope about it made of hydrogen and helium that gives us a clear and unobstructed view of the dynamo."

These observations will also add to the general understanding of how dynamos generate magnetic fields, including here on Earth.

"Any time we understand anything about another planet, we can take that knowledge and apply it to our knowledge about our own planet," Espley said. "We'll be looking at Juno's observations in a big-picture perspective."

NASA's Jet Propulsion Laboratory in Pasadena, California, manages the Juno mission for the principal investigator, Scott Bolton, of Southwest Research Institute in San Antonio. Juno is part of NASA's New Frontiers Program, which is managed at NASA's Marshall Space Flight Center in Huntsville, Alabama, for NASA's Science Mission Directorate. Lockheed Martin Space Systems, Denver, built the spacecraft.

For more information about the Juno mission, visit: http://www.nasa.gov/juno and http://missionjuno.swri.edu.

Image (mentioned), Video (mentioned), Text, Credits: NASA's Goddard Space Flight Center/Sarah Schlieder/Karl Hille.

Best regards, Orbiter.ch

Recent Hydrothermal Activity May Explain Ceres' Brightest Area

NASA - Dawn Mission patch.

June 29, 2016

The brightest area on Ceres, located in the mysterious Occator Crater, has the highest concentration of carbonate minerals ever seen outside Earth, according to a new study from scientists on NASA's Dawn mission. The study, published online in the journal Nature, is one of two new papers about the makeup of Ceres.

Image above: The center of Ceres' mysterious Occator Crater is the brightest area on the dwarf planet. The inset perspective view shows new data on this feature: Red signifies a high abundance of carbonates, while gray indicates a low carbonate abundance. Image Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/ASI/INAF.

"This is the first time we see this kind of material elsewhere in the solar system in such a large amount," said Maria Cristina De Sanctis, lead author and principal investigator of Dawn's visible and infrared mapping spectrometer. De Sanctis is based at the National Institute of Astrophysics, Rome.

At about 80 million years old, Occator is considered a young crater. It is 57 miles (92 kilometers) wide, with a central pit about 6 miles (10 kilometers) wide. A dome structure at the center, covered in highly reflective material, has radial and concentric fractures on and around it.

De Sanctis' study finds that the dominant mineral of this bright area is sodium carbonate, a kind of salt found on Earth in hydrothermal environments. This material appears to have come from inside Ceres, because an impacting asteroid could not have delivered it. The upwelling of this material suggests that temperatures inside Ceres are warmer than previously believed. Impact of an asteroid on Ceres may have helped bring this material up from below, but researchers think an internal process played a role as well.

More intriguingly, the results suggest that liquid water may have existed beneath the surface of Ceres in recent geological time. The salts could be remnants of an ocean, or localized bodies of water, that reached the surface and then froze millions of years ago.

"The minerals we have found at the Occator central bright area require alteration by water," De Sanctis said. "Carbonates support the idea that Ceres had interior hydrothermal activity, which pushed these materials to the surface within Occator."

The spacecraft's visible and infrared mapping spectrometer examines how various wavelengths of sunlight are reflected by the surface of Ceres. This allows scientists to identify minerals that are likely producing those signals. The new results come from the infrared mapping component, which examines Ceres in wavelengths of light too long for the eye to see.

Image above: Occator Crater is 57 miles (92 kilometers) wide, with a central pit around 6 miles (10 kilometers) wide. This enhanced-color view highlights subtle color differences on Ceres' surface. Image Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI/LPI.

Last year, in a Nature study, De Sanctis' team reported that the surface of Ceres contains ammoniated phyllosilicates, or clays containing ammonia. Because ammonia is abundant in the outer solar system, this finding introduced the idea that Ceres may have formed near the orbit of Neptune and migrated inward. Alternatively, Ceres may have formed closer to its current position between Mars and Jupiter, but with material accumulated from the outer solar system.

The new results also find ammonia-bearing salts -- ammonium chloride and/or ammonium bicarbonate -- in Occator Crater. The carbonate finding further reinforces Ceres' connection with icy worlds in the outer solar system. Ammonia, in addition to sodium carbonate and sodium bicarbonate found at Occator, has been detected in the plumes of Enceladus, an icy moon of Saturn known for its geysers erupting from fissures in its surface. Such materials make Ceres interesting for the study of astrobiology.

"We will need to research whether Ceres' many other bright areas also contain these carbonates," De Sanctis said.

A separate Nature study in 2015 by scientists with the Dawn framing camera team hypothesized that the bright areas contain a different kind of salt: magnesium sulfate. But the new findings suggest sodium carbonate is the more likely constituent.

"It’s amazing how much we have been able to learn about Ceres' interior from Dawn's observations of chemical and geophysical properties. We expect more such discoveries as we mine this treasure trove of data," said Carol Raymond, deputy principal investigator for the Dawn mission, based at NASA's Jet Propulsion Laboratory, Pasadena, California.

Dawn spacecraft during the Ceres flyby. Image Credits: NASA/JPL-Caltech

Dawn science team members have also published a new study about the makeup of the outer layer of Ceres in Nature Geoscience, based on images from Dawn's framing camera. This study, led by Michael Bland of the U.S. Geological Survey, Flagstaff, Arizona, finds that most of Ceres' largest craters are more than 1 mile (2 kilometers) deep relative to surrounding terrain, meaning they have not deformed much over billions of years. These significant depths suggest that Ceres' subsurface is no more than 40 percent ice by volume, and the rest may be a mixture of rock and low-density materials such as salts or chemical compounds called clathrates. The appearance of a few shallow craters suggests that there could be variations in ice and rock content in the subsurface.

Related link:

Nature study in 2015: http://www.jpl.nasa.gov/news/news.php?feature=4785

Dawn’s mission is managed by JPL for NASA’s Science Mission Directorate in Washington. 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:

http://dawn.jpl.nasa.gov/mission

More information about Dawn is available at the following sites:

http://dawn.jpl.nasa.gov

http://www.nasa.gov/dawn

Images (mentioned),Text, Credits: NASA/Tony Greicius/JPL/Elizabeth Landau.

Best regards, Orbiter.ch

Rosetta - OSIRIS data release – including “shadow” flyby

ESA - Rosetta Mission patch.

June 29, 2016

Remember the stunning image Rosetta snapped of its own shadow last year? This was just one of twelve images taken by the OSIRIS narrow-angle camera during the 6 km flyby of Comet 67P/Churyumov-Gerasimenko on 14 February 2015 that captured the shadow, and which have today been released into the Archive Image Browser and the Planetary Science Archive.

Animation above showing Rosetta’s shadow move across the surface of Comet 67P/Churyumov-Gerasimenko during the 14 February 2015 flyby. The sequence lasts from 12:38 to 12:41 UT. The full resolution images can be downloaded from the Archive. Animation Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.

This latest OSIRIS data release comprises 1357 narrow-angle camera images and 2162 wide-angle camera images from the period 20 December 2014 – 10 March 2015. During this time Rosetta was initially in ~28 km orbits around the comet. In early February the spacecraft moved out to 142 km before swooping past the comet at 6 km on 14 February and away again (this video visualizes Rosetta’s trajectory at that time).

The 14 February flyby was not only special because it was the closest Rosetta had ever been to the surface of the comet at that time but it also passed through a unique observational geometry: for a short time the Sun, spacecraft, and comet were exactly aligned. In this geometry, surface structures cast almost no shadows, and therefore the reflection properties of the surface material can be determined. As a side effect, Rosetta’s shadow could also be seen, cast on the surface of the comet as a fuzzy rectangular-shaped dark spot surrounded by a bright halo-like region. The shadow is fuzzy and somewhat larger than Rosetta itself, measuring approximately 20 x 50 metres. (For more information about this effect see last year’s blog post “Comet flyby: OSIRIS catches glimpse of Rosetta’s shadow"):
http://orbiterchspacenews.blogspot.ch/2015/03/comet-flyby-osiris-catches-glimpse-of.html

Images above: Example of images from the OSIRIS wide-angle camera albums in the latest data release. Images Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.

The data release also contains many other beauty shots of the comet from both near and far, with the wide-angle camera shots in particular capturing the comet’s ever-increasing activity at that time.

Also today, 540 new NAVCAM images were added to the Archive Image Browser. The latest batch cover the period 4-31 May 2016 and as such include images from the close flyby that took Rosetta to within 5 km of the surface.

Images above: Examples of NAVCAM images from the May 2016 archive. Images Credits: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0.

For more recent OSIRIS images, see the OSIRIS image of the day archive: https://planetgate.mps.mpg.de/Image_of_the_Day/public/IofD_archive.html

Related links:

Archive Image Browser: http://imagearchives.esac.esa.int/

Planetary Science Archive: http://www.sciops.esa.int/index.php?project=PSA

Comet viewer tool: http://sci.esa.int/comet-viewer/

Where is Rosetta?: http://sci.esa.int/where_is_rosetta/

For more information about Rosetta mission, visit: http://www.esa.int/Our_Activities/Space_Science/Rosetta

Rosetta overview: http://www.esa.int/Our_Activities/Space_Science/Rosetta_overview

Rosetta in depth: http://sci.esa.int/rosetta

Images (mentioned), Animation (mentioned), Text, Credit: European Space Agency (ESA).

Greetings, Orbiter.ch