NASA Data Peers into Greenland’s Ice Sheet

NASA - Operation IceBridge patch.

January 25, 2015

A three-dimensional view of the age and structure of the Greenland Ice Sheet

Scientists using ice-penetrating radar data collected by NASA’s Operation IceBridge and earlier airborne campaigns have built the first-ever comprehensive map of layers deep inside the Greenland Ice Sheet.

Greenland's Ice Layers Mapped in 3D

Video above: Peering into the thousands of frozen layers inside Greenland’s ice sheet is like looking back in time. Each layer provides a record of what Earth’s climate was like at the dawn of civilization, or during the last ice age, or during an ancient period of warmth similar to the one we experience today. Image Credit: NASA Goddard's Scientific Visualization Studio.

This new map allows scientists to determine the age of large swaths of Greenland’s ice, extending ice core data for a better picture of the ice sheet’s history. “This new, huge data volume records how the ice sheet evolved and how it’s flowing today,” said Joe MacGregor, a glaciologist at The University of Texas at Austin’s Institute for Geophysics and the study’s lead author.

Greenland’s ice sheet is the second largest mass of ice on Earth, containing enough water to raise ocean levels by about 20 feet. The ice sheet has been losing mass over the past two decades and warming temperatures will mean more losses for Greenland. Scientists are studying ice from different climate periods in the past to better understand how the ice sheet might respond in the future.

One way of studying this distant past is with ice cores. These cylinders of ice drilled from the ice sheet hold evidence of past snow accumulation and temperature and contain impurities like dust and volcanic ash that were carried by snow that accumulated and compacted over hundreds of thousands of years. These layers are visible in ice cores and can be detected with ice-penetrating radar.

Ice-penetrating radar works by sending radar signals into the ice and recording the strength and return time of reflected signals. From those signals, scientists can detect the ice surface, sub-ice bedrock and layers within the ice.

New techniques used in this study allowed scientists to efficiently pick out these layers in radar data. Prior studies had mapped internal layers, but not at the scale made possible by these newer, faster methods. Another major factor in this study was the amount of Greenland IceBridge has measured.

Image above: An east Greenland glacier seen from the NASA P-3 in April 2014. Image Credit: NASA/Jim Yungel.

“IceBridge surveyed previously unexplored parts of the Greenland Ice Sheet and did it using state-of-the-art CReSIS radars,” said study co-author, Mark Fahnestock, a glaciologist from the Geophysical Institute at University of Alaska Fairbanks and IceBridge science team member. CReSIS is the Center for Remote Sensing of Ice Sheets, a National Science Foundation Science and Technology Center headquartered at the University of Kansas in Lawrence, Kansas. 

IceBridge’s flight lines often intersect ice core sites where other scientists have analyzed the ice’s chemical composition to map and date layers in the ice. These core data provide a reference for radar measurements and provide a way to calculate how much ice from a given climate period exists across the ice sheet, something known as an age volume. Scientists are interested in knowing more about ice from the Eemian period, a time from 115,000 to 130,000 years ago that was roughly as warm as today. This new age volume provides the first rough estimate of where Eemian ice may remain.

Comparing this age volume to simple computer models helped the study’s team better understand the ice sheet’s history. Differences in the mapped and modeled age volumes point to past changes in ice flow or processes like melting at the ice sheet’s base. This information will be helpful for evaluating the more sophisticated ice sheet models that are crucial for projecting Greenland’s future contribution to sea-level rise. “Prior to this study, a good ice-sheet model was one that got its present thickness and surface speed right. Now, they’ll also be able to work on getting its history right, which is important because ice sheets have very long memories,” said MacGregor.

This study was published online on Jan. 16, 2015, in Journal of Geophysical Research Earth Surface. It was a collaboration between scientists at UTIG, UAF-GI, CReSIS and the Dept. of Earth System Science at University of California, Irvine. It was supported by NASA’s Operation IceBridge and the National Science Foundation’s Arctic Natural Sciences.

Related link:

Journal of Geophysical Research Earth Surface: http://onlinelibrary.wiley.com/doi/10.1002/2014JF003215/abstract

For more information on Operation IceBridge, visit: http://www.nasa.gov/icebridge

Image (mentioned), Video (mentioned), Text, Credits: NASA's Goddard Space Flight Center/George Hale.

Best regards, Orbiter.ch

NASA’s CATS Installed on ISS by Robotic Handoff

ISS - International Space Station patch.

January 25, 2015

On Jan. 22, 2015, robotic flight controllers successfully installed NASA’s Cloud Aerosol Transport System (CATS) aboard the International Space Station through a robotic handoff — the first time one robotic arm on station has worked in concert with a second robotic arm. CATS will collect data about clouds, volcanic ash plumes and tiny airborne particles that can help improve our understanding of aerosol and cloud interactions and improve the accuracy of climate change models.

CATS had been mounted inside the SpaceX Dragon cargo craft’s unpressurized trunk since it docked at the station on Jan. 12. Ground controllers at NASA’s Johnson Space Center in Houston used one of the space station’s robotic arms, called the Special Purpose Dexterous Manipulator, to extract the instrument from the capsule. The NASA-controlled arm passed the instrument to a second robotic arm — like passing a baton in a relay race. This second arm, called the Japanese Experiment Module Remote Manipulator System, is controlled by the Japanese Aerospace Exploration Agency. The Japanese-controlled arm installed the instrument to the Space Station’s Japanese Experiment Module, making CATS the first NASA-developed payload to fly on the Japanese module.

Image above: This video frame shows a robotic arm on the space station, called the Japanese Experiment Module Remote Manipulator System, successfully installing NASA's Cloud-Aerosol Transport System (CATS) to the Space Station’s Japanese Experiment Module on Jan. 22, 2015. Image Credit: NASA.

After installation, CATS was powered on and is currently sending health and status data back to NASA’s Goddard Space Flight Center in Greenbelt, Maryland, where the instrument’s data will be analyzed, as the team begins their checkout procedures.

CATS is a lidar remote-sensing instrument designed to last from six months to three years. It is specifically intended to demonstrate a low-cost, streamlined approach to developing science payloads on the space station. CATS launched aboard the SpaceX Dragon spacecraft on Jan. 10 from Cape Canaveral Air Force Station in Florida.

Related Link:

NASA's CATS website: http://www.nasa.gov/cats/

Image (mentioned), Text, Credits: NASA's Goddard Space Flight Center/Kasha Patel.

Greetings, Orbiter.ch

Satellites catch Austfonna shedding ice

ESA - Sentinel-1 logo / ESA - Cryosat 2 logo.

23 January 2015

Rapid ice loss in a remote Arctic ice cap has been detected by the Sentinel-1A and CryoSat satellites.

Located on Norway’s Nordaustlandet island in the Svalbard archipelago, parts of the Austfonna ice cap have thinned by more than 50 m since 2012 – about a sixth of the ice’s thickness.

 Austfonna ice loss & Increased ice velocity

Over the last two decades, ice loss from the southeast region of Austfonna has increased significantly, and ice thinning has spread over 50 km inland and is now within 10 km of the summit.

The ice cap’s outlet glacier is also flowing 25 times faster, from 150 m to 3.8 km per year – half a metre per hour.

In the study published in Geophysical Research Letters, a team led by scientists from the Centre for Polar Observation and Modelling (CPOM) at the University of Leeds in the UK combined observations from eight satellite missions, including Sentinel-1A and CryoSat, with results from regional climate models.

“These results provide a clear example of just how quickly ice caps can evolve, and highlight the challenges associated with making projections of their future contribution to sea level,” said the study’s lead author, Dr Mal McMillan.

“New satellites such as Sentinel-1A and CryoSat are essential for enabling us to systematically monitor ice caps and ice sheets, and to better understand these remote polar environments.”

Sentinel-1A, the first satellite developed for Europe’s Copernicus programme, was launched in April last year, while CryoSat has been in orbit since 2010.

Melting ice caps and glaciers are responsible for about a third of recent global sea-level rise. Although scientists predict that they will continue to lose ice in the future, determining the exact amount is difficult, owing to a lack of observations and the complex nature of their interaction with the surrounding climate.

Sentinel-1

“Glacier surges, similar to what we have observed, are a well-known phenomenon,” said Professor Andrew Shepherd, Director of CPOM.

“However, what we see here is unusual because it has developed over such a long period of time, and appears to have started when ice began to thin and accelerate at the coast.”

There is evidence that the surrounding ocean temperature has increased in recent years, which may have been the original trigger for the ice cap thinning.

CryoSat

“Whether or not the warmer ocean water and ice cap behaviour are directly linked remains an unanswered question.

“Feeding the results into existing ice flow models may help us to shed light on the cause, and also improve predictions of global ice loss and sea level rise in the future.”

Long-term observations by satellites are crucial for monitoring such climate-related phenomena in the years and decades to come. 

Related links:

The study published in Geophysical Research Letters: http://onlinelibrary.wiley.com/doi/10.1002/2014GL062255/abstract

Centre for Polar Observation and Modelling: http://www.cpom.org/index.html

University of Leeds: http://www.leeds.ac.uk/

Copernicus: http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus/Overview3

Related missions:

Sentinel-1: http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus/Sentinel-1

CryoSat: http://www.esa.int/Our_Activities/Observing_the_Earth/CryoSat

Images, Text, Credits: ESA/P. Carril/CPOM/GRL/ATG medialab.

Best regards, Orbiter.ch

Hilltop Panorama Marks Mars Rover's 11th Anniversary

NASA - Mars Exploration Rover (MER-B) patch.

January 23, 2015

Image above: This panorama is the view NASA's Mars Exploration Rover Opportunity gained from the top of the "Cape Tribulation" segment of the rim of Endeavour Crater. Image Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.

A panorama from one of the highest elevations that NASA's Mars Exploration Rover Opportunity has reached in its 11 years on Mars includes the U.S. flag at the summit.

The view is from the top of "Cape Tribulation," a raised section of the rim of Endeavour Crater. The panorama spans the interior of the 14-mile-wide (22-kilometer-wide) crater and extends to the rim of another crater on the horizon.

Image above: NASA's Mars Exploration Rover Opportunity obtained this view from the top of the "Cape Tribulation" segment of the rim of Endeavour Crater. Image Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.

Opportunity has driven 25.9 miles (41.7 kilometers) since it landed in the Meridiani Planum region of Mars on Jan. 25, 2004 (Universal Time, which was Jan. 24, PST). That is farther than any other off-Earth surface vehicle has driven. The rover's work on Mars was initially planned for three months. During that prime mission and for more than a decade of bonus performance in extended missions, Opportunity has returned compelling evidence about wet environments on ancient Mars.

Opportunity has been exploring Endeavour's western rim since 2011. From a low segment of the rim that it crossed in mid-2013, called "Botany Bay," it climbed about 440 feet (about 135 meters) in elevation to reach the top of Cape Tribulation. That's about 80 percent the height of the Washington Monument.

Image above: NASA's Mars Exploration Rover Opportunity gained this stereo vista from the top of a raised segment of the rim of Endeavour Crater during the month of the 11th anniversary of its 2004 landing on Mars. Image Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.

The U.S. flag is printed on the aluminum cable guard of the rover's rock abrasion tool, which is used for grinding away weathered rock surfaces to expose fresh interior material for examination. The flag is intended as a memorial to victims of the Sept. 11, 2001, attacks on the World Trade Center in New York. The aluminum was recovered from the site of the Twin Towers in the weeks following the attacks. Workers at Honeybee Robotics in lower Manhattan, less than a mile from World Trade Center, were making the rock abrasion tool for Opportunity and NASA's twin Mars Exploration Rover, Spirit, in September 2001.

11 Years and Counting: Opportunity on Mars

Video above: View the many unique areas that the Mars Exploration Rover Opportunity traveled during its 11 year historic journey. Video Credits: NASA/JPL-Caltech.

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover Project for NASA's Science Mission Directorate in Washington. For more information about Opportunity and Spirit, visit: http://www.nasa.gov/rovers and http://marsrovers.jpl.nasa.gov

You can follow the project on Twitter and on Facebook at: http://twitter.com/MarsRovers and http://www.facebook.com/mars.rovers

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

Cheers, Orbiter.ch

Integral manoeuvres for the future

ESA - Integral Mission patch.

23 January 2015

Since 2002, ESA’s Integral spacecraft has been observing some of the most violent events in the Universe, including gamma-ray bursts and black holes. While it still has years of life ahead, its fuel will certainly run out one day.

Integral, one of ESA’s longest-serving and most successful space observatories, has begun a series of four thruster burns carefully designed to balance its scientific life with a safe reentry in 2029.

Integral: gamma-ray observatory

That seems far off, but detailed planning and teamwork now will ensure that the satellite’s eventual entry into the atmosphere will meet the Agency’s guidelines for minimising space debris.

Making these disposal manoeuvres so early will also minimises fuel usage, allowing ESA to exploit the valuable satellite’s lifetime to the fullest.

This is the first time that a spacecraft’s orbit is being adjusted, after 12 years in space, to achieve a safe reentry 15 years in the future, while maximising valuable science return for the subsequent seven to eight years.

“Our four burns will use about half of the estimated 96 kg of fuel available,” says Richard Southworth, spacecraft operations manager at ESA’s Space Operations Centre, ESOC, in Darmstadt, Germany.

“This will influence how Integral’s orbit evolves, so that even after we run out of propellant we will still have a safe reentry in February 2029 as a result of natural orbit decay.

“No further manoeuvres are required between now and then and Integral can continue to operate.”

Debris mitigation

The latest ESA debris guidelines require that a satellite must be disposed of in such a way that it poses no risk to other satellites in protected orbital regions for more than 25 years.

Although Integral’s early launch date, in 2002, means it is not required to stick to the guidelines, they were followed for planning the disposal.

Protected orbital regions

“We have done a great deal of modelling for Integral’s reentry in 2029,” says Klaus Merz of ESA’s Space Debris Office.

“We’re confident that this month’s manoeuvres will put it on track for a future safe reentry at latitudes in the far south, reducing risk far below guideline levels.”

Without these firings, the fuel supply would run out in perhaps 12–16 more years, after other essentials such as power end Integral's working life. But the satellite would not reenter for up to 200 years, which would present a hazard to other missions.

Manoeuvring in space

The first of the four burns was performed on 12–13 January, and ran for 16 minutes.

It delivered a small change in orbital velocity, and hence size and shape of the orbit, so that ESA’s Perth, Australia, ground tracking station would become usable for the satellite for all future manoeuvres.

This is important because it allows the Integral team to execute subsequent firings exactly at perigee – the point of closest approach to Earth’s surface – which is the optimum point in its orbit to execute manoeuvres, leading to the most efficient use of fuel.

Supernova explosion

The second and largest burn is set for Saturday, 24 January, and will run for about 32 minutes to provide about half of the overall required change in velocity.

The third manoeuvre is planned for 4 February, followed by a possible fourth on 12 February to trim the orbit in order to provide favourable tracking coverage for the rest of the mission from ESA’s Kiruna ground station in Sweden.

Teamwork delivers results

Developing the complex plan has taken years of teamwork by the mission operations and science operations teams, but it will set Integral onto a sustainable course for the rest of its mission.

“At first glance, it looked like the goals of space debris mitigation and maximising science were incompatible considering the limited amount of fuel available,” explained Claudia Dietze and Gerald Ziegler, flight dynamics specialists working on Integral at ESOC.

“However, after detailed analysis, a sequence was developed that meets both goals. Moreover, additional considerations of attitude constraints and ground station coverage had to be taken into account, making it a highly interesting and challenging undertaking.”

Space navigators at work

With the burns complete, Integral will continue scientific observations until its fuel runs out in the early 2020s.

The normal degradation of the solar panels by radiation will begin to limit observations anyway until, at some point probably in the mid-2020s, science operations would need to stop regardless of fuel.

“However, we are also looking into ways to reduce routine fuel usage by applying techniques developed for other missions, such as our sister satellite, XMM-Newton,” says Richard Southworth.

Sustainable future

“This is a robust, doable, safe and complete plan,” says Peter Kretschmar, Integral’s mission manager.

“It’s allowing us to maximise the precious scientific return from this satellite, while fully meeting end-of-life and debris mitigation guidelines,” adds Erik Kuulkers, Integral’s project scientist.

The mission celebrated its 10th anniversary in orbit in 2012, and is currently extended until December 2016.

Integral’s reentry animation

Integral enables scientists to study our Universe at gamma-ray wavelengths, and it has discovered amazing objects including one of the fastest spinning neutron stars as well as gamma-rays from a supernova.

Editor’s note: manoeuvre dates mentioned here are all subject to change through operational considerations. Follow ESA’s Rocket Science blog for a detailed timeline and Twitter for live updates.

http://blogs.esa.int/rocketscience

http://www.twitter.com/esaoperations

Related links:

ESA Perth ground tracking station: http://www.esa.int/Our_Activities/Operations/Perth_station

ESA Kiruna ground station: http://www.esa.int/Our_Activities/Operations/Kiruna_station

Integral operations: http://www.esa.int/Our_Activities/Operations/Integral_operations

Integral: http://www.esa.int/Our_Activities/Space_Science/Integral

Integral workshop: http://integralworkshop2012.in2p3.fr/Home.html

Images, Video, Text, Credits: ESA/J. Mai/Medialab/CNES/ATG medialab/HTG.

Greetings, Orbiter.ch

Getting to know Rosetta’s comet

ESA - Rosetta Mission patch.

22 January 2015

Comet from 8 km

Rosetta is revealing its host comet as having a remarkable array of surface features and with many processes contributing to its activity, painting a complex picture of its evolution.

In a special edition of the journal Science, initial results are presented from seven of Rosetta’s 11 science instruments based on measurements made during the approach to and soon after arriving at Comet 67P/Churyumov–Gerasimenko in August 2014.

Comet regional maps

The familiar shape of the dual-lobed comet has now had many of its vital statistics measured: the small lobe measures 2.6 × 2.3 × 1.8 km and the large lobe 4.1 × 3.3 × 1.8 km. The total volume of the comet is 21.4 km3 and the Radio Science Instrument has measured its mass to be 10 billion tonnes, yielding a density of 470 kg/m3.

By assuming an overall composition dominated by water ice and dust with a density of 1500–2000 kg/m3, the Rosetta scientists show that the comet has a very high porosity of 70–80%, with the interior structure likely comprising weakly bonded ice-dust clumps with small void spaces between them.

Ripples and wind-tails

The OSIRIS scientific camera, has imaged some 70% of the surface to date: the remaining unseen area lies in the southern hemisphere that has not yet been fully illuminated since Rosetta’s arrival.

The scientists have so far identified 19 regions separated by distinct boundaries and, following the ancient Egyptian theme of the Rosetta mission, these regions are named for Egyptian deities, and are grouped according to the type of terrain dominant within.

Five basic – but diverse – categories of terrain type have been determined: dust-covered; brittle materials with pits and circular structures; large-scale depressions; smooth terrains; and exposed more consolidated (‘rock-like’) surfaces.

Active pit

Much of the northern hemisphere is covered in dust. As the comet is heated, ice turns directly into gas that escapes to form the atmosphere or coma. Dust is dragged along with the gas at slower speeds, and particles that are not travelling fast enough to overcome the weak gravity fall back to the surface instead.

Some sources of discrete jets of activity have also been identified. While a significant proportion of activity emanates from the smooth neck region, jets have also been spotted rising from pits.    

The gases that escape from the surface have also been seen to play an important role in transporting dust across the surface, producing dune-like ripples, and boulders with ‘wind-tails’ – the boulders act as natural obstacles to the direction of the gas flow, creating streaks of material ‘downwind’ of them.

Icy alcove

The dusty covering of the comet may be several metres thick in places and measurements of the surface and subsurface temperature by the Microwave Instrument on the Rosetta Orbiter, or MIRO, suggest that the dust plays a key role in insulating the comet interior, helping to protect the ices thought to exist below the surface.

Small patches of ice may also be present on the surface. At scales of 15–25 m, Rosetta’s Visible, InfraRed and Thermal Imaging Spectrometer, or VIRTIS, finds the surface to be compositionally very homogenous and dominated by dust and carbon-rich molecules, but largely devoid of ice. But smaller, bright areas seen in images are likely to be ice-rich. Typically, they are associated with exposed surfaces or debris piles where collapse of weaker material has occurred, uncovering fresher material.

A crack in the comet

On larger scales, many of the exposed cliff walls are covered in randomly oriented fractures. Their formation is linked to the rapid heating–cooling cycles that are experienced over the course of the comet’s 12.4-hour day and over its 6.5-year elliptical orbit around the Sun. One prominent and intriguing feature is a 500 m-long crack seen roughly parallel to the neck between the two lobes, although it is not yet known if it results from stresses in this region.

Some very steep regions of the exposed cliff faces are textured on scales of roughly 3 m with features that have been nicknamed ‘goosebumps’. Their origin is yet to be explained, but their characteristic size may yield clues as to the processes at work when the comet formed. 

Comet goosebumps

And on the very largest scale, the origin of the comet’s overall double-lobed shape remains a mystery. The two parts seem very similar compositionally, potentially favouring the erosion of a larger, single body. But the current data cannot yet rule out the alternative scenario: two separate comets formed in the same part of the Solar System and then merged together at a later date.

This key question will be studied further over the coming year as Rosetta accompanies the comet around the Sun.

How to grow an atmosphere

Their closest approach to the Sun occurs on 13 August at a distance of 186 million kilometres, between the orbits of Earth and Mars. As the comet continues to move closer to the Sun, an important focus for Rosetta’s instruments is to monitor the development of the comet’s activity, in terms of the amount and composition of gas and dust emitted by the nucleus to form the coma.

Images from the scientific and navigation cameras have shown an increase in the amount of dust flowing away from the comet over the past six months, and MIRO showed a general rise in the comet’s global water vapour production rate, from 0.3 litres per second in early June 2014 to 1.2 litres per second by late August. MIRO also found that a substantial portion of the water seen during this phase originated from the comet’s neck.

Water is accompanied by other outgassing species, including carbon monoxide and carbon dioxide. The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis, ROSINA, is finding large fluctuations in the composition of the coma, representing daily and perhaps seasonal variations in the major outgassing species. Water is typically the dominant outgassing molecule, but not always.

How a comet grows a magnetosphere

By combining measurements from MIRO, ROSINA and GIADA (Rosetta’s Grain Impact Analyzer and Dust Accumulator) taken between July and September, the Rosetta scientists have made a first estimate of the comet’s dust-to-gas ratio, with around four times as much mass in dust being emitted than in gas, averaged over the sunlit nucleus surface.

However, this value is expected to change once the comet warms up further and ice grains – rather than pure dust grains – are ejected from the surface.

GIADA has also been tracking the movement of dust grains around the comet, and, together with images from OSIRIS, two distinct populations of dust grains have been identified. One set is outflowing and is detected close to the spacecraft, while the other family is orbiting the comet no closer than 130 km from the spacecraft.

It is thought that the more distant grains are left over from the comet’s last closest approach to the Sun. As the comet moved away from the Sun, the gas flow from the comet decreased and was no longer able to perturb the bound orbits. But as the gas production rate increases again over the coming months, it is expected that this bound cloud will dissipate. However, Rosetta will only be able to confirm this when it is further away from the comet again – it is currently in a 30 km orbit.

Comet vital statistics

As the gas–dust coma continues to grow, interactions with charged particles of the solar wind and with the Sun’s ultraviolet light will lead to the development of the comet’s ionosphere and, eventually, its magnetosphere. The Rosetta Plasma Consortium, or RPC, instruments have been studying the gradual evolution of these components close to the comet.

“Rosetta is essentially living with the comet as it moves towards the Sun along its orbit, learning how its behaviour changes on a daily basis and, over longer timescales, how its activity increases, how its surface may evolve, and how it interacts with the solar wind,” says Matt Taylor, ESA’s Rosetta project scientist.

“We have already learned a lot in the few months we have been alongside the comet, but as more and more data are collected and analysed from this close study of the comet we hope to answer many key questions about its origin and evolution.”

Notes for Editors

These are among the very first scientific results from Rosetta and there is much more to come as the scientists work through the data and as the comet continues to evolve during its closest approach to the Sun. They are described in more detail in accompanying posts on the Rosetta blog and in the 23 January 2015 Science special edition:

“Dust Measurements in the Coma of Comet 67P/Churyumov- Gerasimenko Inbound to the Sun Between 3.7 and 3.4 AU” by A. Rotundi et al. (GIADA)

“Subsurface properties and early activity of comet 67P/Churyumov-Gerasimenko” by S. Gulkis et al. (MIRO)

“The Morphological Diversity of Comet 67P/Churyumov-Gerasimenko” by N. Thomas et al. (OSIRIS)

“On the nucleus structure and activity of comet 67P/Churyumov-Gerasimenko” by H. Sierks et al. (OSIRIS)

“Time variability and heterogeneity in the coma of 67P/Churyumov-Gerasimenko,” by M. Hässig et al. (ROSINA)

“Birth of a comet magnetosphere: a spring of water ions,” by H. Nilsson et al. (RPC-ICA)

“67P/Churyumov-Gerasimenko: The Organic-rich surface of a Kuiper Belt comet as seen by VIRTIS/Rosetta” by F. Capaccioni et al. (VIRTIS)

More 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.

More about...:

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 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

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

Operations: http://www.esa.int/Our_Activities/Operations

Rosetta Blog: http://blogs.esa.int/rosetta/

Images, Text, Credits: Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA/RPC-ICA.

Best regards, Orbiter.ch

Gullies on Vesta Suggest Past Water-Mobilized Flows

NASA - Dawn Mission patch.

January 22, 2015

Protoplanet Vesta, visited by NASA's Dawn spacecraft from 2011 to 2013, was once thought to be completely dry, incapable of retaining water because of the low temperatures and pressures at its surface. However, a new study shows evidence that Vesta may have had short-lived flows of water-mobilized material on its surface, based on data from Dawn.

"Nobody expected to find evidence of water on Vesta. The surface is very cold and there is no atmosphere, so any water on the surface evaporates," said Jennifer Scully, postgraduate researcher at the University of California, Los Angeles. "However, Vesta is proving to be a very interesting and complex planetary body."

The study has broad implications for planetary science.

Image above: This image shows Cornelia Crater on the large asteroid Vesta. On the right is an inset image showing an example of curved gullies, indicated by the short white arrows, and a fan-shaped deposit, indicated by long white arrows. Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

"These results, and many others from the Dawn mission, show that Vesta is home to many processes that were previously thought to be exclusive to planets," said UCLA's Christopher Russell, principal investigator for the Dawn mission. "We look forward to uncovering even more insights and mysteries when Dawn studies Ceres."

Dawn is currently in the spotlight because it is approaching dwarf planet Ceres, the largest object in the main asteroid belt between Mars and Jupiter. It will be captured into orbit around Ceres on March 6. Yet data from Dawn's exploration of Vesta continue to capture the interest of the scientific community.

Scully and colleagues, publishing in the journal "Earth and Planetary Science Letters," identified a small number of young craters on Vesta with curved gullies and fan-shaped ("lobate") deposits.

"We're not suggesting that there was a river-like flow of water. We're suggesting a process similar to debris flows, where a small amount of water mobilizes the sandy and rocky particles into a flow," Scully said.

The curved gullies are significantly different from those formed by the flow of purely dry material, scientists said. "These features on Vesta share many characteristics with those formed by debris flows on Earth and Mars," Scully said.

The gullies are fairly narrow, on average about 100 feet (30 meters) wide. The average length of the gullies is a little over half a mile (900 meters). Cornelia Crater, with a width of 9 miles (15 kilometers), contains some of the best examples of the curved gullies and fan-shaped deposits.

The leading theory to explain the source of the curved gullies is that Vesta has small, localized patches of ice in its subsurface. No one knows the origin of this ice, but one possibility is that ice-rich bodies, such as comets, left part of their ice deep in the subsurface following impact. A later impact would form a crater and heat up some of the ice patches, releasing water onto the walls of the crater.

Image above: This image of NASA's Dawn spacecraft and the giant asteroid Vesta is an artist's concept. Dawn arrived at Vesta on July 15, 2011 PDT (July 16, 2011 EDT) and is set to depart on Sept. 4, 2012 PDT (Sept. 5, 2012 EDT). Image credit: NASA/JPL-Caltech.

"If present today, the ice would be buried too deeply to be detected by any of Dawn’s instruments," Scully said. "However, the craters with curved gullies are associated with pitted terrain, which has been independently suggested as evidence for loss of volatile gases from Vesta." Also, evidence from Dawn's visible and infrared mapping spectrometer and gamma ray and neutron detector indicates that there is hydrated material within some rocks on Vesta’s surface, suggesting that Vesta is not entirely dry.

It appears the water mobilized sandy and rocky particles to flow down the crater walls, carving out the gullies and leaving behind the fan-shaped deposits after evaporation. The craters with curvy gullies appear to be less than a few hundred million years old, which is still young compared to Vesta's age of 4.6 billion years.

Laboratory experiments performed at NASA's Jet Propulsion Laboratory, Pasadena, California, indicate that there could be enough time for curved gullies to form on Vesta before all of the water evaporated. “The sandy and rocky particles in the flow help to slow the rate of evaporation,” Scully said.

The Dawn mission to Vesta and Ceres is managed by JPL, a division of the California Institute of Technology in Pasadena, for NASA's Science Mission Directorate, Washington. UCLA is responsible for overall Dawn mission science.

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

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

Cheers, Orbiter.ch