NASA's Spitzer Spots Planet Deep Within Our Galaxy

NASA - Spitzer Space Telescope logo.

April 14, 2015

NASA's Spitzer Space Telescope. Image Credits: NASA/JPL-Caltech

NASA's Spitzer Space Telescope has teamed up with a telescope on the ground to find a remote gas planet about 13,000 light-years away, making it one of the most distant planets known.

The discovery demonstrates that Spitzer -- from its unique perch in space -- can be used to help solve the puzzle of how planets are distributed throughout our flat, spiral-shaped Milky Way galaxy. Are they concentrated heavily in its central hub, or more evenly spread throughout its suburbs?

"We don't know if planets are more common in our galaxy's central bulge or the disk of the galaxy, which is why these observations are so important," said Jennifer Yee of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, and a NASA Sagan fellow. Yee is the lead author of one of three new studies that appeared recently in the Astrophysical Journal describing a collaboration between astronomers using Spitzer and the Polish Optical Gravitational Lensing Experiment, or OGLE.

Image above: This artist's map of the Milky Way shows the location of one of the farthest known exoplanets, lying 13,000 light-years away. Most of the thousands of exoplanets discovered to date are closer to our solar system, as indicated by the pink/orange areas. Image Credit: NASA/JPL-Caltech.

OGLE's Warsaw Telescope at the Las Campanas Observatory in Chile scans the skies for planets using a method called microlensing. A microlensing event occurs when one star happens to pass in front of another, and its gravity acts as a lens to magnify and brighten the more distant star's light. If that foreground star happens to have a planet in orbit around it, the planet might cause a blip in the magnification.

Astronomers are using these blips to find and characterize planets tens of thousands of light-years away in the central bulge of our galaxy, where star crossings are more common. Our sun is located in the suburbs of the galaxy, about two-thirds of the way out from the center. The microlensing technique as a whole has yielded about 30 planet discoveries so far, with the farthest residing about 25,000 light-years away.

"Microlensing experiments are already detecting planets from the solar neighborhood to almost the center of the Milky Way," said co-author Andrew Gould of The Ohio State University, Columbus. "And so they can, in principle, tell us the relative efficiency of planet formation across this huge expanse of our galaxy."

Microlensing complements other planet-hunting tools, such as NASA's Kepler mission, which has found more than 1,000 planets closer to home. But it faces one key problem: This method can't always precisely narrow down the distance to the stars and planets being observed. While a passing star may magnify the light of a more distant star, it rarely can be seen itself, making the task of measuring how far away it is challenging.

Image above: This plot shows data obtained from NASA's Spitzer Space Telescope and the Optical Gravitational Lensing Experiment, or OGLE, telescope located in Chile, during a "microlensing" event. Image Credit: NASA/JPL-Caltech/Warsaw University Observatory.

Of the approximately 30 planets discovered with microlensing so far, roughly half cannot be pinned down to a precise location. The result is like a planetary treasure map lacking in X's.

That's where Spitzer can help out, thanks to its remote Earth-trailing orbit. Spitzer circles our sun, and is currently about 128 million miles (207 million kilometers) away from Earth. That's father from Earth than Earth is from our sun. When Spitzer watches a microlensing event simultaneously with a telescope on Earth, it sees the star brighten at a different time, due to the large distance between the two telescopes and their unique vantage points. This technique is generally referred to as parallax.

"Spitzer is the first space telescope to make a microlens parallax measurement for a planet," said Yee. "Traditional parallax techniques that employ ground-based telescopes are not as effective at such great distances."

Using space telescopes to observe microlensing events is tricky. Ground telescopes send out alerts to the astronomy community when an event starts, but the activity can quickly fade, lasting on average about 40 days. The Spitzer team has scrambled to start microlensing campaigns as soon as three days after receiving an alert.

In the case of the newfound planet, the duration of the microlensing event happened to be unusually long, about 150 days. Both Spitzer and OGLE's telescopes detected the telltale planetary blip in the magnification, with Spitzer seeing it 20 days earlier.

Image above: This infographic explains how NASA's Spitzer Space Telescope can be used in tandem with a telescope on the ground to measure the distances to planets discovered using the "microlensing" technique. Image Credit: NASA/JPL-Caltech.

This time delay between viewing of the event by OGLE and Spitzer was used to calculate the distance to the star and its planet. Knowing the distance allowed the scientists also to determine the mass of the planet, which is about half that of Jupiter.

Spitzer has eyed 22 other microlensing events in collaboration with OGLE and several other ground-based telescopes. While these observations have not turned up new planets, the data are essential to learning the population statistics of stars and planets at the heart of our galaxy. Spitzer will watch approximately 120 additional microlensing events this summer.

"We've mainly explored our own solar neighborhood so far," said Sebastiano Calchi Novati, a Visiting Sagan Fellow at NASA's Exoplanet Science Institute at the California Institute of Technology, Pasadena. "Now we can use these single lenses to do statistics on planets as a whole and learn about their distribution in the galaxy."

NASA's Jet Propulsion Laboratory, Pasadena, California, manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA.

For more information about Spitzer, visit: http://spitzer.caltech.edu and http://www.nasa.gov/spitzer

Images (mentioned), Text, Credits: NASA/Felicia Chou/JPL/Whitney Clavin.

Greetings, Orbiter.ch

Rosetta and Philae find comet not magnetised

ESA - Rosetta Mission patch.

14 April 2015

Measurements made by Rosetta and Philae during the probe’s multiple landings on Comet 67P/Churyumov-Gerasimenko show that the comet’s nucleus is not magnetised.

Studying the properties of a comet can provide clues to the role that magnetic fields played in the formation of Solar System bodies almost 4.6 billion years ago. The infant Solar System was once nothing more than a swirling disc of gas and dust but, within a few million years, the Sun burst into life in the centre of this turbulent disc, with the leftover material going into forming the asteroids, comets, moons and planets.

Rosetta and Philae investigate magnetic properties of Comet 67P/C-G

The dust contained an appreciable fraction of iron, some of it in the form of magnetite. Indeed, millimetre-sized grains of magnetic materials have been found in meteorites, indicating their presence in the early Solar System.

This leads scientists to believe that magnetic fields threading through the proto-planetary disc could have played an important role in moving material around as it started to clump together to form larger bodies.

But it remains unclear as to how crucial magnetic fields were later on in this accretion process, as the building blocks grew to centimetres, metres and then tens of metres across, before gravity started to dominate when they grew to hundreds of metres and kilometres in scale.

Some theories concerning the aggregation of magnetic and non-magnetic dust particles show that the resulting bigger objects could also remain magnetised, allowing them to also be influenced by the magnetic fields of the proto-planetary disc.

Because comets contain some of the most pristine materials in the Solar System, they offer a natural laboratory for investigating whether or not these larger chunks could have remained magnetised.

However, detecting the magnetic field of comets has proven difficult in previous missions, which have typically made rapid flybys, relatively far from comet nuclei.

It has taken the proximity of ESA’s Rosetta orbiter to Comet 67P/Churyumov-Gerasimenko, and the measurements made much closer to and at the surface by its lander Philae, to provide the first detailed investigation of the magnetic properties of a comet nucleus.

Reconstructing Philae’s trajectory

Philae’s magnetic field measuring instrument is the Rosetta Lander Magnetometer and Plasma Monitor (ROMAP), while Rosetta carries a magnetometer as part of the Rosetta Plasma Consortium suite of sensors (RPC-MAG).

Changes in the magnetic field surrounding Rosetta allowed RPC-MAG to detect the moment when Philae was deployed in the morning of 12 November 2014.

Then, by sensing periodic variations in the measured external magnetic field and motions in its boom arm, ROMAP was able to detect the touchdown events and determine the orientation of Philae over the following hours. Combined with information from the CONSERT experiment that provided an estimate of the final landing site location, timing information, images from Rosetta’s OSIRIS camera, assumptions about the gravity of the comet, and measurements of its shape, it was possible to determine Philae’s trajectory.

The mission teams soon discovered that Philae not only touched down once at Agilkia, but also came into contact with the comet’s surface four times in fact – including a grazing collision with a surface feature that sent it tumbling towards the final touchdown point at Abydos.

This complex trajectory turned out to be scientifically beneficial to the ROMAP team.

“The unplanned flight across the surface actually meant we could collect precise magnetic field measurements with Philae at the four points we made contact with, and at a range of heights above the surface,” says Hans-Ulrich Auster, co-principal investigator of ROMAP and lead author of the results published in the journal Science and presented at the European Geosciences Union General Assembly in Vienna, Austria, today.

The non-magnetic comet

The multiple descents and ascents meant that the team could compare measurements made on the inward and outward journeys to and from each contact point, and as it flew across the surface.

ROMAP measured a magnetic field during these sequences, but found that its strength did not depend on the height or location of Philae above the surface. This is not consistent with the nucleus itself being responsible for that field.

“If the surface was magnetised, we would have expected to see a clear increase in the magnetic field readings as we got closer and closer to the surface,” explains Hans-Ulrich.  “But this was not the case at any of the locations we visited, so we conclude that Comet 67P/Churyumov-Gerasimenko is a remarkably non-magnetic object.”

Instead, the magnetic field that was measured was consistent with an external one, namely the influence of the solar wind interplanetary magnetic field near the comet nucleus.  This conclusion is confirmed by the fact that variations in the field that were measured by Philae closely agree with those seen at the same time by Rosetta.

“During Philae’s landing, Rosetta was about 17 km above the surface, and we could provide complementary magnetic field readings that rule out any local magnetic anomalies in the comet’s surface materials,” says Karl-Heinz Glassmeier, principal investigator of RPC-MAG on board the orbiter and a co-author of the Science paper.

If large chunks of material on the surface of 67P/Churyumov-Gerasimenko were magnetised, ROMAP would have recorded additional variations in its signal as Philae flew over them.

“If any material is magnetised, it must be on a scale of less than one metre, below the spatial resolution of our measurements. And if Comet 67P/Churyumov-Gerasimenko is representative of all cometary nuclei, then we suggest that magnetic forces are unlikely to have played a role in the accumulation of planetary building blocks greater than one metre in size,” concludes Hans-Ulrich.

“It’s great to see the complementary nature of Rosetta and Philae’s measurements, working together to answer this simple, but important ‘yes-no’ question as to whether the comet is magnetised,” says Matt Taylor, ESA’s Rosetta project scientist.

Notes for Editors:

“The non-magnetic nucleus of Comet 67P/Churyumov-Gerasimenko,” by H.-U. Auster et al. is published in Science Express on 14 April.

The results were also presented on 14 April at the European Geosciences Union (EGU) General Assembly 2015 in Vienna, Austria, during a dedicated Rosetta mission press briefing.

The data were collected by the Rosetta Lander Magnetometer and Plasma Monitor (ROMAP) on board Philae and the Rosetta Plasma Consortium fluxgate magnetometer (RPC-MAG) on board Rosetta.

Overall, the data show that the comet has an upper magnetic field magnitude of less than 2 nT at the cometary surface at multiple locations, with a specific magnetic moment of < 3.1 x 10–5 Am2/kg, less than known values for lunar material and meteorites measured on Earth.

About ROMAP:

ROMAP is the Rosetta Lander Magnetometer and Plasma Monitor. The contributing institutions to ROMAP are: Institut für Geophysik und Extraterrestrische Physik, Technische Universität Braunschweig, Germany; Max-Planck Institut für Sonnensystemforschung, Göttingen, Germany; Hungarian Academy of Sciences Centre for Energy Research, Hungary; and Space Research Institute Graz, Austria. The co-principal investigators are Hans-Ulrich Auster (Technische Universität, Braunschweig) and István Apáthy, KFKI, Budapest, Hungary.

About RPC-MAG:

RPC-MAG one of six instruments comprising the Rosetta Plasma Consortium. The fluxgate magnetometer (RPC-MAG) is led by Karl-Heinz Glassmeier, Technische Universität, Braunschweig, Germany.

About Rosetta:

Rosetta is an ESA mission with contributions from its Member States and NASA. Rosetta’s Philae lander was provided by a consortium led by DLR, MPS, CNES and ASI. Rosetta is the first mission in history to rendezvous with a comet. It is escorting the comet as they orbit the Sun together. Philae landed on the comet on 12 November 2014. Comets are time capsules containing primitive material left over from the epoch when the Sun and its planets formed. By studying the gas, dust and structure of the nucleus and organic materials associated with the comet, via both remote and in situ observations, the Rosetta mission should become the key to unlocking the history and evolution of our Solar System.

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

More about...

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

Rosetta factsheet: http://www.esa.int/Our_Activities/Space_Science/Rosetta/Rosetta_factsheet

Frequently asked questions: http://www.esa.int/Our_Activities/Space_Science/Rosetta/Frequently_asked_questions

For the media:

Rosetta Media press kit: http://sci.esa.int/rosetta/54816-press-kit---12-november-2014---landing-on-a-comet/

Rosetta Media factsheet: http://www.esa.int/Our_Activities/Space_Science/Rosetta/Rosetta_Media_factsheet

Rosetta Media Pages: http://www.esa.int/For_Media/Photos/Highlights/Rosetta_and_Philae

In depth:

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

Related links:

Rosetta at Astrium: http://www.astrium.eads.net/en/programme/rosetta-1go.html

Rosetta at DLR: http://www.dlr.de/dlr/en/desktopdefault.aspx/tabid-10394/

Ground-based comet observation campaign: http://www.rosetta-campaign.net/home

Images, Text, Credits: ESA/Markus Bauer, ESA Science and Robotic Exploration Communication Officer/Hans-Ulrich Auster, ROMAP principal investigator, Technische Universität, Braunschweig/Karl-Heinz Glassmeier, RPC-MAG principal investigator, Technische Universität, Braunschweig/Matt Taylor, ESA Rosetta project scientist/Data: Auster et al. (2015)/Spacecraft: ESA/ATG medialab/Comet image: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA/Background comet image: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0.

Best regards, Orbiter.ch

NASA-funded Study Explains Saturn's Epic Tantrums

NASA - Cassini Mission to Saturn patch.

April 14, 2015

Image above: This series of images from NASA's Cassini spacecraft shows the development of a huge storm of the type that erupts about every 30 years on Saturn. Credit: NASA/JPL-Caltech/SSI.

The long-standing mystery of why Saturn seethes with enormous storms every 30 years may have been solved by scientists working with data from NASA's Cassini mission. The tempests, which can grow into bright bands that encircle the entire planet, are on a natural timer that is reset by each subsequent storm, the researchers report.

In 140 years of telescope observations, great storms have erupted on Saturn six times. Cassini and observers on Earth tracked the most recent of these storms from December 2010 to August 2011. During that time, the storm exploded through the clouds, eventually winding its way around Saturn.

In a paper published online today in the journal Nature Geoscience, scientists describe the effect they believe is responsible for the periodic outbursts. The basic idea is that water vapor is heavier than the hydrogen and helium that make up the bulk of Saturn's atmosphere, so once each giant storm dumps its huge mass of rain, the air within the clouds is left lighter than the atmosphere below. For a time, this situation shuts off the process of convection -- in which warm, moist air rises, and cool, dense air sinks -- that creates new clouds and storms.

"For decades after one of these storms, the warm air in Saturn's deep atmosphere is too wet, and too dense, to rise," said Cheng Li, a graduate student at the California Institute of Technology in Pasadena, who led the study. "The air above has to cool off, radiating its heat to space, before its density is greater than that of the hot, wet air below. This cooling process takes about 30 years, and then come the storms."

Li thinks the episodic nature of the storms indicates Saturn's deep atmosphere contains more water, relative to the other atmospheric constituents, than Jupiter. The researchers suggest Saturn's extra-wet interior might explain why the planet has such epic tantrums, whereas Jupiter does not. If Saturn's deep atmosphere were drier, scientists would expect continuous, smaller storms, as observed on Jupiter, Li said. Instead, Saturn's outbursts are episodic and quite explosive.

Cassini spacecraft. Image Credits: NASA/JPL-Caltech

Other observations by ground and space-based telescopes have hinted at a wet interior for Saturn. "Previous studies using spectroscopy have shown that Saturn's interior is enriched in methane and other volatiles, by two or three times, compared to Jupiter. From there, it's a short leap to expect that Saturn is also rich in oxygen, which is also a volatile and a big part of every H2O molecule," said Andrew Ingersoll, a member of the Cassini science team, also at Caltech, who co-authored the paper with Li. Volatiles are elements and chemical compounds that change from solid to liquid or gas at relatively low temperatures.

Scientists are interested in understanding the amount of oxygen and other volatile ingredients in Saturn and Jupiter. These ingredients provide important clues about the formation of the two planets -- which are thought to have formed before all the others -- and conditions in the early solar system.

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. JPL, a division of Caltech, manages the mission for NASA's Science Mission Directorate in Washington.

For previous news and images related to Saturn's giant storm: http://go.nasa.gov/1H89e3p

For more information about Cassini, visit: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov and http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens

Images (mentioned), Text, Credits: NASA/JPL/Preston Dyches.

Best regards, Orbiter.ch

Unable to live on this planet

Exoplanet Science logo.

April 13, 2015

The exoplanet HD189733, located 63 light-years from Earth, has hellish weather conditions, according to a study.

Artist's view of the exoplanet HD189733b

Astronomers from the Universities of Geneva (UNIGE) and Berne have closely studied the atmosphere of the exoplanet HD189733b, thanks to new measurement techniques. Their findings were unveiled Monday. On this planet, it is 3000 degrees and altitude winds to several thousand km/h.

These infernal weather could be measured by combining both approaches. One is based on the HARPS spectrometer and the other on a new way of interpreting the signal emitted by the sodium in the atmosphere, said in a statement the University of Geneva.

Hot and Stormy at High Altitudes on Exoplanet HD 189733b

According to the alma mater Geneva, this study opens "the way to exploring the atmospheres of exoplanets with more accessible tools that giant or space telescopes." It led to publications in journals "Astronomy & Astrophysics" and "Astrophysical Journal Letters".

The exoplanet HD189733b is 63 light years from Earth in the constellation Vulpecula. studies of this planet by the Universities of Geneva and Bern were conducted as part of the national research center PlanetS.

Related links:

Universities of Geneva (UNIGE) http://www.unige.ch/

Astronomical Observatory of Geneva http://www.unige.ch/sciences/astro/fr/
English: http://www.unige.ch/sciences/astro/en/

HARPS: http://obswww.unige.ch/Instruments/HARPS/

NCCR PlanetS: http://exoplanets.ch/nccr-planets/

Images, Tex, Credits: ATS/Universities of Geneva (UNIGE)/Orbiter.ch Aerospace.

Cheers, Orbiter.ch

NASA Mars Rover's Weather Data Bolster Case for Brine

NASA - Mars Science Laboratory (MSL) logo.

April 13, 2015

Martian weather and soil conditions that NASA's Curiosity rover has measured, together with a type of salt found in Martian soil, could put liquid brine in the soil at night.

Perchlorate identified in Martian soil by the Curiosity mission, and previously by NASA's Phoenix Mars Lander mission, has properties of absorbing water vapor from the atmosphere and lowering the freezing temperature of water. This has been proposed for years as a mechanism for possible existence of transient liquid brines at higher latitudes on modern Mars, despite the Red Planet's cold and dry conditions.

Image above: The Rover Environmental Monitoring Station (REMS) on NASA's Curiosity Mars rover includes temperature and humidity sensors mounted on the rover's mast. One of the REMS booms extends to the left from the mast in this view. Image Credit: NASA/JPL-Caltech/MSSS.

New calculations were based on more than a full Mars year of temperature and humidity measurements by Curiosity. They indicate that conditions at the rover's near-equatorial location were favorable for small quantities of brine to form during some nights throughout the year, drying out again after sunrise. Conditions should be even more favorable at higher latitudes, where colder temperatures and more water vapor can result in higher relative humidity more often.

"Liquid water is a requirement for life as we know it, and a target for Mars exploration missions," said the report's lead author, Javier Martin-Torres of the Spanish Research Council, Spain, and Lulea University of Technology, Sweden, and a member of Curiosity's science team. "Conditions near the surface of present-day Mars are hardly favorable for microbial life as we know it, but the possibility for liquid brines on Mars has wider implications for habitability and geological water-related processes."

The weather data in the report published today in Nature Geosciences come from the Cuirosity's Rover Environmental Monitoring Station (REMS), which was provided by Spain and includes a relative-humidity sensor and a ground-temperature sensor. NASA's Mars Science Laboratory Project is using Curiosity to investigate both ancient and modern environmental conditions in Mars' Gale Crater region. The report also draws on measurements of hydrogen in the ground by the rover's Dynamic Albedo of Neutrons (DAN) instrument, from Russia.

(Click on the image for enlarge)

Image above: This April 10, 2015, view from the Navigation Camera on NASA's Curiosity Mars rover shows the terrain ahead of the rover as it makes its way westward through a valley called "Artist's Drive." Image Credit: NASA/JPL-Caltech.

"We have not detected brines, but calculating the possibility that they might exist in Gale Crater during some nights testifies to the value of the round-the-clock and year-round measurements REMS is providing," said Curiosity Project Scientist Ashwin Vasavada of NASA's Jet Propulsion Laboratory, Pasadena, California, one of the new report's co-authors.

Curiosity is the first mission to measure relative humidity in the Martian atmosphere close to the surface and ground temperature through all times of day and all seasons of the Martian year. Relative humidity depends on the temperature of the air, as well as the amount of water vapor in it. Curiosity's measurements of relative humidity range from about five percent on summer afternoons to 100 percent on autumn and winter nights. 

Air filling pores in the soil interacts with air just above the ground. When its relative humidity  gets above a threshold level, salts can absorb enough water molecules to become dissolved in liquid, a process called deliquescence. Perchlorate salts are especially good at this. Since perchlorate has been identified both at near-polar and near-equatorial sites, it may be present in soils all over the planet.

(Click on the image for enlarge)

Image above: NASA's Curiosity Mars rover used its Navigation Camera to capture this view on April 11, 2015, during passage through a valley called "Artist's Drive" on the route up Mount Sharp. The image appears three-dimensional when viewed through red-blue glasses with the red lens on the left. Image Credit: NASA/JPL-Caltech.

Researchers using the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter have in recent years documented numerous sites on Mars where dark flows appear and extend on slopes during warm seasons. These features are called recurring slope lineae, or RSL. A leading hypothesis for how they occur involves brines formed by deliquesence.

"Gale Crater is one of the least likely places on Mars to have conditions for brines to form, compared to sites at higher latitudes or with more shading. So if brines can exist there, that strengthens the case they could form and persist even longer at many other locations, perhaps enough to explain RSL activity," said HiRISE Principal Investigator Alfred McEwen of the University of Arizona, Tucson, also a co-author of the new report.

In the 12 months following its August 2012 landing, Curiosity found evidence for ancient streambeds and a lakebed environment more than 3 billion years ago that offered conditions favorable for microbial life. Now, the rover is examining a layered mountain inside Gale Crater for evidence about how ancient environmental conditions evolved. JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Science Laboratory and Mars Reconnaissance Projects for NASA's Science Mission Directorate, Washington.

For more information about Curiosity, visit: http://www.nasa.gov/msl and http://mars.jpl.nasa.gov/msl/

Images (mentioned), Text, Credits: NASA/Dwayne Brown/JPL/Guy Webster.

Best regards, Orbiter.ch

Dawn's Ceres Color Map Reveals Surface Diversity

NASA - DAWN Mission patch.

April 13, 2015

A new color map of dwarf planet Ceres, which NASA's Dawn spacecraft has been orbiting since March, reveals the diversity of the surface of this planetary body. Differences in morphology and color across the surface suggest Ceres was once an active body, Dawn researchers said today at the 2015 General Assembly of the European Geosciences Union in Vienna.

Image above: This map-projected view of Ceres was created from images taken by NASA's Dawn spacecraft during its initial approach to the dwarf planet, prior to being captured into orbit in March 2015. Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

"This dwarf planet was not just an inert rock throughout its history. It was active, with processes that resulted in different materials in different regions. We are beginning to capture that diversity in our color images," said Chris Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles.

The Dawn mission made history on March 6 as the first spacecraft to reach a dwarf planet, and the first spacecraft to orbit two extraterrestrial targets. Previously, Dawn studied giant asteroid Vesta from 2011 to 2012, uncovering numerous insights about its geology and history. While Vesta is a dry body, Ceres is believed to be 25 percent water ice by mass. By comparing Vesta and Ceres, scientists hope to gain a better understanding of the formation of the solar system.

Ceres' surface is heavily cratered, as expected, but appears to have fewer large craters than scientists anticipated. It also has a pair of very bright neighboring spots in its northern hemisphere. More detail will emerge after the spacecraft begins its first intensive science phase on April 23, from a distance of 8,400 miles (13,500 kilometers) from the surface, said Martin Hoffmann, investigator on the Dawn framing camera team, based at the Max Planck Institute for Solar System Research, Göttingen, Germany.

DAWN spacecraft heading Ceres. Image Credits:NASA/JPL-Caltech

The visible and infrared mapping spectrometer (VIR), an imaging spectrometer that examines Ceres in visible and infrared light, has been examining the relative temperatures of features on Ceres’ surface. Preliminary examination suggests that different bright regions on Ceres' surface behave differently, said Federico Tosi, investigator from the VIR instrument team at the Institute for Space Astrophysics and Planetology, and the Italian National Institute for Astrophysics, Rome.

Based on observations from NASA/ESA Hubble Space Telescope, planetary scientists have identified 10 bright regions on Ceres’ surface. One pair of bright spots, by far the brightest visible marks on Ceres, appears to be located in a region that is similar in temperature to its surroundings. But a different bright feature corresponds to a region that is cooler than the rest of Ceres' surface.

Image above: These images, from Dawn's visible and infrared mapping spectrometer (VIR), highlight two regions on Ceres containing bright spots. The top images show a region scientists have labeled "1" and the bottom images show the region labeled "5." Image Credit: NASA/JPL-Caltech/UCLA/ASI/INAF.

The origins of Ceres' bright spots, which have captivated the attention of scientists and the public alike, remain unknown. It appears the brightest pair is located in a crater 57 miles (92 kilometers) wide. As Dawn gets closer to the surface of Ceres, better-resolution images will become available.

"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," Russell said.

Both Vesta and Ceres are located in the main asteroid belt between Mars and Jupiter. The Dawn spacecraft will continue studying Ceres through June 2016.

Dawn's mission is managed by NASA's Jet Propulsion Laboratory, Pasadena, California, 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/

For more information about Dawn, visit: http://dawn.jpl.nasa.gov

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

Greetings, Orbiter.ch

Rosetta watches the comet’s activity as it approaches the inner Solar System

ESA - Rosetta Mission patch.

April 13, 2015

Comet activity 31 January – 25 March 2015

Four months from today, on 13 August, Comet 67P/Churyumov-Gerasimenko will reach perihelion – a moment that defines its closest point to the Sun along its orbit.

For 67P/Churyumov-Gerasimenko, this takes place at a distance of about 185 million km from the Sun, between the orbits of Earth and Mars.

Rosetta is along for the ride, and has been watching the gradual evolution of the comet since arriving in August 2014.

As the comet’s surface layers are gently warmed, frozen ices sublimate. The escaping gas carries streams of dust out into space, and together these slowly expand to create the comet’s fuzzy atmosphere, or coma.

Comet on 25 March 2015 – NavCam

As the comet continues to move closer to the Sun, the warming continues and activity rises, and pressure from the solar wind causes some of the materials to stream out into long tails, one made of gas, the other of dust. The comet’s coma will eventually span tens of thousands of kilometres, while the tails may extend hundreds of thousands of kilometres, and both will be visible through large telescopes on Earth.

But it is Rosetta’s close study of the comet, from just a few tens of kilometres above its surface, which enables the source of the comet’s activity to be studied in great detail, providing context to the more distant ground-based observations.

Comet on 14 March 2015 (b) – NavCam

This spectacular montage of 18 images shows off the comet’s activity from many different angles as seen between 31 January (top left) and 25 March (bottom right), when the spacecraft was at distances of about 30 to 100 km from the comet. At the same time, Comet 67P/Churyumov-Gerasimenko was at distances between 363 million and 300 million km from the Sun.

After perihelion, Rosetta will continue to follow the comet, watching how the activity subsides as it moves away from the Sun and back  to the outer Solar System again.

While the majority of the images in the montage have been released previously, the final frame is published for the first time in today's Cometwatch on the Rosetta blog: http://blogs.esa.int/rosetta/2015/04/13/cometwatch-activity-31-january-25-march/

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

Images , Text, Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0.

Greetings, Orbiter.ch