vendredi 23 janvier 2015

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.

video
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.

video
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

jeudi 22 janvier 2015

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

Mysteries in Nili Fossae












ESA - Mars Express Mission patch.

22 January 2015

Nili Fossae

These new images from the high-resolution stereo camera on ESA’s Mars Express show Nili Fossae, one of the most enticing regions on Mars. This ‘graben system’ lies northeast of the volcanic region of Syrtis Major on the northwestern edge of the large Isidis impact basin – and intriguing hints of methane have been seen here.

Grabens are blocks of land that have fallen between parallel faults, sometimes forming rift valleys. The graben system in Nili Fossae contains numerous troughs oriented concentrically around the edges of an impact basin, as can be seen in the context map.

Nili Fossae in context

The easternmost of these troughs is partially visible at the lower left of the images. It is perhaps most obvious as a depression in the topography map from Mars Express.

The graben is most likely associated with the formation of the Isidis impact basin. Flooding of the basin with basaltic lava may have resulted in subsidence, which added stress to the planet’s crust and was then released through fracturing and trough formation.

Nili Fossae topography

Mars Express and other spacecraft have shown that the region displays a fascinating mineral diversity, drawing the attention of many planetary scientists. The minerals include phyllosilicates (clays), carbonates and opaline silica. These indicate a diverse history for this area resulting from the huge geological and tectonic forces that have been at play.

Perspective view of Nili Fossae

Water has played an important role here, too. The visible trough’s flanks are very steep (see the topography map) and some layered materials can be spotted at the walls. On the plateau, several depressions can be observed. Some of them appear to extend into the trough and show a resemblance to small ‘sapping valleys’.

Sapping valleys develop when groundwater removes material from underneath the surface. This gradually relocates the spring line further upstream, carving a valley in the process.

 Nili Fossae in 3D

The images also contain evidence for percolating hydrothermal fluids in the subsurface of the region. A large, 55 km-diameter impact crater with a central pit is clearly seen in the main colour, topography and 3D images. The pit is believed to have been excavated when water or ice, trapped below the surface, was rapidly heated by the impact that shaped the crater. The sudden heating caused a violent steam explosion that either weakened the rocky surface, leading to its collapse, or it may even have blasted it away, leaving the rocky hole and rocky debris.

Mars Express

In addition to the variety of interesting geological features, Nili Fossae is of particular interest because it is a site where atmospheric methane may have been detected by Earth-based telescopes. Methane may be produced here, but its origin remains mysterious, and could be geological or perhaps even biological.

There is certainly a huge amount to study here. Nili Fossae was on the shortlist of landing sites for NASA’s Curiosity rover, even though ultimately the choice was made to send the robotic explorer to Gale Crater.

More about...:

Looking at Mars: http://www.esa.int/Our_Activities/Space_Science/Mars_Express

Mars Express overview: http://www.esa.int/Our_Activities/Space_Science/Mars_Express_overview

Mars Express 10 year brochure: http://esamultimedia.esa.int/multimedia/publications/BR-312/

Related links:

High Resolution Stereo Camera: http://berlinadmin.dlr.de/Missions/express/indexeng.shtml

Behind the lens...: http://www.esa.int/Our_Activities/Space_Science/Mars_Express/Behind_the_lens

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

ESA Planetary Science archive (PSA): http://www.rssd.esa.int/PSA

NASA Planetary Data System: http://pds-geosciences.wustl.edu/missions/mars_express/hrsc.htm

HRSC data viewer: http://hrscview.fu-berlin.de/

In depth:

Mars Express in depth: http://sci.esa.int/science-e/www/area/index.cfm?fareaid=9

Mars Express top 10 discoveries: http://sci.esa.int/jump.cfm?oid=51820

Mars Express blog: http://blogs.esa.int/mex/

Mars Webcam: http://blogs.esa.int/vmc

Images, Text, Credits: ESA/Alex Lutkus/DLR/FU Berlin, CC BY-SA 3.0 IGO/NASA MGS MOLA Science Team.

Greetings, Orbiter.ch

mardi 20 janvier 2015

Telescope To Seek Dust Where Other Earths May Lie











Large Binocular Telescope Interferometer (LBTI) logo.

January 20, 2015

The NASA-funded Large Binocular Telescope Interferometer, or LBTI, has completed its first study of dust in the "habitable zone" around a star, opening a new door to finding planets like Earth. Dust is a natural byproduct of the planet-formation process, but too much of it can block our view of planets.

The findings will help in the design of future space missions that have the goal of taking pictures of planets similar to Earth, called exo-Earths.

"Kepler told us how common Earth-like planets are," said Phil Hinz, the principal investigator of the LBTI project at the University of Arizona, Tucson, referring to NASA's planet-hunting Kepler mission, which has identified more than 4,000 planetary candidates around stars. "Now we want to find out just how dusty and obscured planetary environments are, and how difficult the planets will be to image."


Image above: The Large Binocular Telescope at Mt. Graham, Arizona. Image Credit: Large Binocular Telescope Observatory.

The new instrument, based at the Large Binocular Telescope Observatory at the top of Mount Graham in southeastern Arizona, will obtain the best infrared images yet of dust permeating a star's habitable zone, the region around the star where water -- an essential ingredient for life as we know it -- could pool on a planet. Earth sits comfortably within our sun's habitable zone, hence its glistening surface of oceans.

Scientists want to take pictures of exo-Earths and break up their light into a rainbow of colors. This color information is displayed in plots, called spectra, which reveal chemical clues about whether a planet could sustain life. But dust -- which comes from colliding asteroids and evaporating comets -- can outshine the feeble light of a planet, making this task difficult.

"Imagine trying to view a firefly buzzing around a lighthouse in Canada from Los Angeles," said Denis Defrère of the University of Arizona, lead author of the new study that appears in the Jan. 14 issue of the Astrophysical Journal. "Now imagine that fog is in the way. The fog is like our stardust. We want to eliminate the stars with fog from our list of targets to study in the future."

A previous NASA project, called the Keck Interferometer, had a similar task of seeking out this dust, finding good news for planet hunters: The stars they observed didn't seem to be all that dusty on average. LBTI is taking the research a step further, more precisely quantifying the amount of dust around stars. It will be 10 times more sensitive than the Keck Interferometer, and is specially designed to target a star's inner region -- its sweet spot, the habitable zone.

The new study reports LBTI's first test observations of stardust, in this case around a mature, sun-like star called eta Corvi known to be unusually dusty. According to the science team, this star is 10,000 times dustier than our own solar system, likely due to a recent impact between planetary bodies in its inner regions. The surplus of dust gives the telescope a good place to practice its dust-detecting skills.


Image above: The Large Binocular Telescope Interferometer (LBTI) instrument set its eyes on a dusty star system called Eta Corvi, depicted here in this artist's concept. Recent collisions between comets and rocky bodies within the star system are thought to have generated the surplus of dust. Image Credit: NASA/JPL-Caltech.

The results showed the telescope works as intended, but also yielded a surprise: The dust was observed to be significantly closer to the star than previously thought, lying between the star and its habitable zone. NASA's Spitzer Space Telescope has previously estimated the dust to be farther out, based on models of the size of the dust grains.

"With LBTI, we can really see where the dust is," said Hinz. "This star is a not a good candidate for direct imaging of planets, but it demonstrates what LBTI is good for: We are figuring out the architecture of planetary systems in a way that has not been done before."

LBTI will begin its official science operations this spring, and will operate for at least three years. One of the project's goals is to find stars 10 times less dusty than our solar system -- the good candidates for planet imaging. These survey results will inform designs and strategies for upcoming exo-Earth imaging missions now in early planning stages. The journey to find worlds ripe for life begins in part by following a trail of dust.

LBTI is funded by NASA Headquarters. It is managed by the agency's Jet Propulsion Laboratory, Pasadena, California, for NASA's Exoplanet Exploration Program office, and operated by the University of Arizona. The Large Binocular Telescope Observatory is operated by an international collaboration among institutions in the United States, Italy and Germany. JPL is a division of the California Institute of Technology in Pasadena.

The Astrophysical Journal paper is online at: http://iopscience.iop.org/0004-637X/799/1/42/article

For more information about Large Binocular Telescope Interferometer (LBTI), visit: http://lbti.as.arizona.edu/LBTI/index.html and http://www.jpl.nasa.gov/missions/large-binocular-telescope-interferometer-lbti/

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

Greetings, Orbiter.ch

Telescope on NASA’s SDO Collects Its 100-Millionth Image












NASA - Solar Dynamics Observatory (SDO) patch.

Jan. 20, 2015

On Jan. 19, 2015, at 12:49 p.m. EST, an instrument on NASA's Solar Dynamics Observatory captured its 100 millionth image of the sun. The instrument is the Atmospheric Imaging Assembly, or AIA, which uses four telescopes working parallel to gather eight images of the sun – cycling through 10 different wavelengths -- every 12 seconds.


Image above: The Atmospheric Imaging Assembly on NASA's Solar Dynamics Observatory captured its 100 millionth image of the sun on Jan. 19, 2015. The dark areas at the bottom and the top of the image are coronal holes -- areas of less dense gas, where solar material has flowed away from the sun. Credit: NASA/SDO/AIA/LMSAL.

Between the AIA and two other instruments on board, the Helioseismic Magnetic Imager and the Extreme Ultraviolet Variability Experiment, SDO sends down a whopping 1.5 terabytes of data a day. AIA is responsible for about half of that. Every day it provides 57,600 detailed images of the sun that show the dance of how solar material sways and sometimes erupts in the solar atmosphere, the corona.


Image above: Processed image of SDO multiwavelength blend from Jan. 19, 2015, the date of the spacecraft's 100th millionth image release. Image Credits: NASA/SDO.

In the almost five years since its launch on Feb. 11, 2010, SDO has provided images of the sun to help scientists better understand how the roiling corona gets to temperatures some 1000 times hotter than the sun's surface, what causes giant eruptions such as solar flares, and why the sun's magnetic fields are constantly on the move.


Images above: This image shows an early SDO image (2010) and SDO's 100th millionth image (2015). Images Credits: NASA/SDO.

In honor of the 100 millionth image, Dean Pesnell, SDO's project scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland and Karel Schrijver, the AIA principal investigator at Lockheed Martin in Palo Alto, California, chose some of their favorite images produced by SDO so far.

Related Links:

NASA's SDO website: http://www.nasa.gov/sdo

How SDO gathers images: http://www.nasa.gov/content/goddard/why-nasa-studies-the-ultraviolet-sun/

View "100 million images" mosaic: http://www.nasa.gov/content/goddard/100-millionth-image-from-sdos-aia-mosaic/

SDO Images: Scientists' Picks: http://www.nasa.gov/content/goddard/sdo-telescope-collects-its-100-millionth-image/index.html#lowerAccordion-set1-slide7

Images (mentioned), Text, Credits: NASA's Goddard Space Flight Center/Karen C. Fox.

Cheers, Orbiter.ch

SolarImpulse - First Round-The-World Solar Flight











SolarImpulse - Around the World patch.

20 January 2015

After the Solar Impulse prototype’s 8 world records, when it became the first solar airplane ever to fly through the night, between two continents, and across the United States, it is time for Bertrand Piccard and André Borschberg to move on to the final phase of the adventure: the 2015 round-the-world flight.


Image above: From Abu Dhabi to the first solar flight around the world, the route map.

What better way to demonstrate the importance of the pioneering, innovatory spirit than by achieving “impossible” things with renewable energy and highlighting new solutions for environmental problems?


Image above: SI2 has 17'248 solar cells, powering four 17,4hp electric motor.

The route: Si2 will take-off from Abu Dhabi, capital of the United Arab Emirate, in late February or early March and return by late July or early August 2015. The route includes stops in Muscat, Oman; Ahmedabad and Varanasi, India; Mandalay, Myanmar; and Chongqing and Nanjing, China. After crossing the Pacific Ocean via Hawaii, Si2 will fly across the Continental U.S.A. stopping in three locations – Phoenix, and New York City at JFK. A location in the Midwest will be decided dependent on weather conditions. After crossing the Atlantic, the final legs include a stop-over in Southern Europe or North Africa before arriving back in Abu Dhabi. Solar Impulse unveiled the flight path in Abu Dhabi alongside partner representatives. This included main partners Solvay, Omega, Schindler and ABB. They were also joined by official partners Altran, Bayer, Google, Swiss Re Corporate Solutions, Swisscom and Moët Hennessy alongside Solar Impulse’s host partner Masdar, Abu Dhabi’s renewable energy company.


Image above: SI2 is a single-seater airplane, for one pilot to live in for flight of 120 hours!

A great historic first: for such an adventure, as for any premiere, there are no references. We were, and will be, faced with a number of challenges, leading us to push the limits of technological, human and piloting performance.

For more information about SolarImpulse, visit: http://www.solarimpulse.com/

Images, Text, Credit: SolarImpulse.

Best regards, Orbiter.ch

lundi 19 janvier 2015

Two new planets to the bottom of the solar system?












Astronomy - Astrophysics logo.

January 19, 2015

British and Spanish scientists have discovered that at least two stars could be "hidden" behind Neptune, they argue in a study.

The solar system could contain more planets than expected

The solar system could house two additional planets, according to British and Spanish researchers deduct the unexpected trajectory of the various objects observed behind Neptune suffer the influence of the unknown planets.

In 2006, the International Astronomical Union withdrew Pluto's planet status given its small size which relates now to the category of dwarf planets, dropping the number of planets in the solar system to eight.

A debate for decades

This has not stopped the debate stirred astronomers around the world for decades: other planets exist beyond Pluto?

In a study published in the journal "Monthly notices of the Royal astronomical society letters" the researchers provide "at least two planets" are hidden behind Neptune.

"Unexpected orbital parameters"

The researchers based their particular deduction on the study of the orbital behavior of a dozen extreme Trans-Neptunian Objects (ETNO).

They have "unexpected orbital parameters" that "suggest that unseen forces affect their orbital distribution," said astrophysicist Carlos de la Fuente Marcos, the agency of Spanish scientific information Sinc.

Neptune

Number unknown

"We believe that the most likely explanation is that other unknown planets exist beyond Neptune and Pluto," said the researcher at the Complutense University of Madrid and co-author of the study with scientists from the University of Cambridge.

"Their exact number is unknown, because our data are limited, but our calculations suggest that there are at least two planets, and probably more, on the borders of our solar system," he added.

A possible revolution in astronomy

The authors of the study, however, recognize that their theory contradicts the currently accepted model of the formation of the solar system, according to which there are no other planets in circular orbit behind Neptune.

Moreover, the calculations are based on the study of a small number of objects, but researchers ensure that other results will be published in the coming months, broadening the sample. "If confirmed, our findings could revolutionize astronomy," considers Mr. Marcos Fuente.

Related link:

Monthly notices of the Royal astronomical society letters: http://mnras.oxfordjournals.org/

Images, Text, Credits: AFP/Wikimedia/NASA&ESA Hubble/Translation: Orbiter.ch Aerospace.

Cheers, Orbiter.ch

Dawn Delivers New Image of Ceres












NASA - Dawn Mission patch.

January 19, 2015


Animation above: The Dawn spacecraft observed Ceres for an hour on Jan. 13, 2015, from a distance of 238,000 miles (383,000 kilometers). A little more than half of its surface was observed at a resolution of 27 pixels. This animated GIF shows bright and dark features.Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI.

As NASA's Dawn spacecraft closes in on Ceres, new images show the dwarf planet at 27 pixels across, about three times better than the calibration images taken in early December. These are the first in a series of images that will be taken for navigation purposes during the approach to Ceres.

Over the next several weeks, Dawn will deliver increasingly better and better images of the dwarf planet, leading up to the spacecraft's capture into orbit around Ceres on March 6. The images will continue to improve as the spacecraft spirals closer to the surface during its 16-month study of the dwarf planet.

"We know so much about the solar system and yet so little about dwarf planet Ceres. Now, Dawn is ready to change that," said Marc Rayman, Dawn's chief engineer and mission director, based at NASA's Jet Propulsion Laboratory in Pasadena, California.


Image above: This is a raw image, taken Jan. 13, 2015, showing the dwarf planet Ceres as seen from the Dawn spacecraft on its approach. Dawn's framing camera took this image at 238,000 miles (383,000 kilometers) from Ceres. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR.

The best images of Ceres so far were taken by NASA's Hubble Space Telescope in 2003 and 2004. This most recent images from Dawn, taken January 13, 2015, at about 80 percent of Hubble resolution, are not quite as sharp. But Dawn's images will surpass Hubble's resolution at the next imaging opportunity, which will be at the end of January.

"Already, the [latest] images hint at first surface structures such as craters," said Andreas Nathues, lead investigator for the framing camera team at the Max Planck Institute for Solar System Research, Gottingen, Germany.

Ceres is the largest body in the main asteroid belt, which lies between Mars and Jupiter. It has an average diameter of 590 miles (950 kilometers), and is thought to contain a large amount of ice. Some scientists think it's possible that the surface conceals an ocean.


Image above: This processed image, taken Jan. 13, 2015, shows the dwarf planet Ceres as seen from the Dawn spacecraft. The image hints at craters on the surface of Ceres. Dawn's framing camera took this image at 238,000 miles (383,000 kilometers) from Ceres Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

Dawn's arrival at Ceres will mark the first time a spacecraft has ever visited a dwarf planet.

"The team is very excited to examine the surface of Ceres in never-before-seen detail," said Chris Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles. "We look forward to the surprises this mysterious world may bring."

The spacecraft has already delivered more than 30,000 images and many insights about Vesta, the second most massive body in the asteroid belt. Dawn orbited Vesta, which has an average diameter of 326 miles (525 kilometers), from 2011 to 2012. Thanks to its ion propulsion system, Dawn is the first spacecraft ever targeted to orbit two deep-space destinations.

JPL manages the Dawn mission 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. The University of California at Los Angeles (UCLA) is responsible for overall Dawn mission science. Orbital Sciences Corp. in Dulles, Virginia, designed and built the spacecraft. UCLA is responsible for overall Dawn mission science. The Dawn framing cameras were developed and built under the leadership of the Max Planck Institute for Solar System Research, Gottingen, Germany, with significant contributions by German Aerospace Center (DLR), Institute of Planetary Research, Berlin, and in coordination with the Institute of Computer and Communication Network Engineering, Braunschweig. The Framing Camera project is funded by the Max Planck Society, DLR, and NASA/JPL. The Italian Space Agency and the Italian National Astrophysical Institute are international partners on the mission team.

More information about Dawn is online at http://dawn.jpl.nasa.gov.

Images (mentioned), Animation (mentioned), Text, Credit: NASA.

Greetings, Orbiter.ch