Exposed ice on Rosetta’s comet confirmed as water

ESA - Rosetta Mission patch.

13 January 2016

Observations made shortly after Rosetta’s arrival at its target comet in 2014 have provided definitive confirmation of the presence of water ice.

Although water vapour is the main gas seen flowing from comet 67P/Churyumov–Gerasimenko, the great majority of ice is believed to come from under the comet’s crust, and very few examples of exposed water ice have been found on the surface.

Infrared observations of water ice in Imhotep

However, a detailed analysis by Rosetta’s VIRTIS infrared instrument reveals the composition of the comet’s topmost layer: it is primarily coated in a dark, dry and organic-rich material but with a small amount of water ice mixed in.

In the latest study, which focuses on scans between September and November 2014, the team confirms that two areas several tens of metres across in the Imhotep region that appear as bright patches in visible light, do indeed include a significant amount of water ice.

The ice is associated with cliff walls and debris falls, and was at an average temperature of about –120ºC at the time.

Ice in Imhotep

In those regions, pure water ice was found to occupy around 5% of each pixel sampling area, with the rest made up of the dark, dry material. The abundance of ice was calculated by comparing Rosetta’s VIRTIS infrared measurements to models that consider how ice grains of different sizes might be mixed together in one pixel.

The data reveal two different populations of grains: one is several tens of micrometres in diameter, while the other is larger, around 2 mm.

These sizes contrast with the very small grains, just a few micrometres in diameter, found in the Hapi region on the ‘neck’ of the comet, as observed by VIRTIS in a different study.

“The various populations of icy grains on the surface of the comet imply different formation mechanisms, and different time scales for their formation,” says Gianrico Filacchione, lead author of the new study, published in the journal Nature.

At Hapi, the very small grains are associated with a thin layer of ‘frost’ that forms as part of the daily ice cycle, a result of fast condensation in this region over each comet rotation of just over 12 hours.

“By contrast, we think that layers of the larger millimetre-sized grains we see in Imhotep have a more complex history. They likely formed slowly over time, and are only occasionally exposed through erosion,” says Gianrico.

Assuming a typical grain size of tens of micrometres for ice grains on the surface, as inferred on other comets as well as Rosetta’s comet, then observations of millimetre-sized grains can be explained by the growth of secondary ice crystals.

One way this can occur is via ‘sintering’, whereby ice grains are compacted together. Another method is ‘sublimation’, in which heat from the Sun penetrates the surface, triggering the evaporation of buried ice. While some of the resulting water vapour may escape from the nucleus, a significant fraction of it recondenses in layers beneath the surface.

This idea is supported by laboratory experiments that simulate the sublimation behaviour of ice buried under dust, heated from above by sunlight.

Rosetta orbiting the comet

These tests show that more than 80% of the released water vapour does not make it up through the dust mantle, but rather is redeposited below the surface.

Additional energy for sublimation could also be provided by a transformation in structure of the ice at a molecular level. At the low temperatures observed on comets, amorphous ice can change into crystalline ice, releasing energy as it does so.

“Ice grain growth can lead to ice-rich subsurface layers several metres thick, that can then affect the large-scale structure, porosity and thermal properties of the nucleus,” says Fabrizio Capaccioni, VIRTIS principal investigator.

“The thin ice-rich layers that we see exposed close to the surface may be a consequence of cometary activity and evolution, implying that global layering did not necessarily occur early in the comet’s formation history.”

“Understanding which features on the comet are left over from its formation and which have been created during its evolution is somewhat challenging, but this is why we are studying a comet up close: to try to discover what processes are important at different stages of a comet’s lifetime,” adds Matt Taylor, ESA’s Rosetta project scientist.

The Rosetta scientists are now analysing data captured later in the mission, as the comet moved closer to the Sun in mid-2015, to see how the amount of ice exposed on the surface evolved as the heating increased.

Notes for Editors

“Exposed water ice on the nucleus of comet 67P/Churyumov–Gerasimenko,” by G. Filacchione et al is published in the journal Nature: http://www.nature.com/nature/journal/vaop/ncurrent/full/nature16190.html

Related article:

Rosetta Reveals Comet's Water-Ice Cycle
http://orbiterchspacenews.blogspot.ch/2015/09/rosetta-reveals-comets-water-ice-cycle.html

Related links:

Rosetta Mission: http://www.esa.int/Our_Activities/Space_Science/Rosetta

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

ESA Rosetta blog: http://blogs.esa.int/rosetta/

Text, Credits: ESA/Matt Taylor/Markus Bauer/VIRTIS/Gianrico Filacchione/Fabrizio Capaccioni/Images Credits: Comet images: ESA/Rosetta/NavCam–CC BY–SA IGO 3.0; VIRTIS images and data: ESA/Rosetta/VIRTIS/INAF-IAPS, Rome/OBS DE PARIS-LESIA/DLR; G. Filacchione et al (2016)/CNES.

Greetings, Orbiter.ch

Performed scheduled ISS orbit correction

ROSCOSMOS - Russian Vehicles patch.

01.12.2016

In accordance with the flight program of the International Space Station (ISS) on January 11, 2016 held the planned correction of the ISS orbit. The purpose of the correction was the creation of conditions for the launch of ballistic transport of manned spacecraft (TPC) Soyuz TMA-20M, scheduled for March 2016.

According to calculations of service ballistics navigation support Mission Control Center (MCC) the engines of the cargo spacecraft Progress M-29M were performed at 5:05 min. MSK (Moscow Time). The engine run time was 1003 seconds. After the maneuver the average height of the flight station increased by 3 km and amounted to 403.8 km.

 ISS reboost by Progress-M Cargo

The parameters of the orbit began as follows:

· Minimum height above the Earth's surface - 399.8 km,

· Maximum height above the Earth's surface - 422.2 km,

· Period - 92.58 min.

· Inclination - 51.66 deg.

The previous planned correction of the ISS orbit was held November 25, 2015 to ensure convergence with the station Soyuz TMA-19M, which successfully took place 15 December 2015.

ROSCOSMOS Press Release: http://www.federalspace.ru/21946/

Image, Text, Credits: ROSCOSMOS/NASA/Orbiter.ch Aerospace/Roland Berga.

Greetings, Orbiter.ch

New Details On Ceres Seen in Dawn Images

NASA - Dawn Mission patch.

Jan. 12, 2016

Features on dwarf planet Ceres that piqued the interest of scientists throughout 2015 stand out in exquisite detail in the latest images from NASA's Dawn spacecraft, which recently reached its lowest-ever altitude at Ceres.

Dawn took these images near its current altitude of 240 miles (385 kilometers) from Ceres, between Dec. 19 and 23, 2015.

Image above: This image from NASA's Dawn spacecraft shows Kupalo Crater, one of the youngest craters on Ceres. The crater has bright material exposed on its rim and walls, which could be salts. Its flat floor likely formed from impact melt and debris. Image Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

Kupalo Crater, one of the youngest craters on Ceres, shows off many fascinating attributes at the high image resolution of 120 feet (35 meters) per pixel. The crater has bright material exposed on its rim, which could be salts, and its flat floor likely formed from impact melt and debris. Researchers will be looking closely at whether this material is related to the "bright spots" of Occator Crater. Kupalo, which measures 16 miles (26 kilometers) across and is located at southern mid-latitudes, is named for the Slavic god of vegetation and harvest.

"This crater and its recently-formed deposits will be a prime target of study for the team as Dawn continues to explore Ceres in its final mapping phase," said Paul Schenk, a Dawn science team member at the Lunar and Planetary Institute, Houston.

Image above: This image from NASA's Dawn spacecraft shows part of Messor Crater (25 miles or 40 kilometers, wide), located at northern mid-latitudes on Ceres. The scene shows an older crater in which a large lobe-shaped flow partly covers the northern (top) part of the crater floor. The flow is a mass of material ejected when a younger crater formed just north of the rim. Image Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

Dawn's low vantage point also captured the dense network of fractures on the floor of 78-mile-wide (126-kilometer-wide) Dantu Crater. One of the youngest large craters on Earth's moon, called Tycho, has similar fractures. This cracking may have resulted from the cooling of impact melt, or when the crater floor was uplifted after the crater formed.

A 20-mile (32-kilometer) crater west of Dantu is covered in steep slopes, called scarps, and ridges. These features likely formed when the crater partly collapsed during the formation process. The curvilinear nature of the scarps resembles those on the floor of Rheasilvia, the giant impact crater on protoplanet Vesta, which Dawn orbited from 2011 to 2012.

Dawn's other instruments also began studying Ceres intensively in mid-December. The visible and infrared mapping spectrometer is examining how various wavelengths of light are reflected by Ceres, which will help identify minerals present on its surface.

Image above: The fractured floor of Dantu Crater on Ceres is seen in this image from NASA's Dawn spacecraft. Similar fractures are seen in Tycho, one of the youngest large craters on Earth's moon. This cracking may have resulted from the cooling of impact melt, or when the crater floor was uplifted after the crater formed. Image Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

Dawn's gamma ray and neutron detector (GRaND) is also keeping scientists busy. Data from GRaND help researchers understand the abundances of elements in Ceres' surface, along with details of the dwarf planet's composition that hold important clues about how it evolved.

The spacecraft will remain at its current altitude for the rest of its mission, and indefinitely afterward. The end of the prime mission will be June 30, 2016.

"When we set sail for Ceres upon completing our Vesta exploration, we expected to be surprised by what we found on our next stop. Ceres did not disappoint," said Chris Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles. "Everywhere we look in these new low- altitude observations, we see amazing landforms that speak to the unique character of this most amazing world."

Image above: NASA's Dawn spacecraft viewed this Cerean crater, which is covered in ridges and steep slopes, called scarps on Dec. 23, 2015. These features likely resulted when the crater partly collapsed during its formation. The curvilinear nature of the scarps resembles those on the floor of Rheasilvia, the giant impact crater on Vesta, which Dawn orbited from 2011 to 2012. Image Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

Dawn is the first mission to visit a dwarf planet, and the first mission outside the Earth-moon system to orbit two distinct solar system targets. After orbiting Vesta for 14 months in 2011 and 2012, it arrived at Ceres on March 6, 2015.

Dawn's mission is managed by the Jet Propulsion Laboratory for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute are international partners on the mission team. For a complete list of mission participants, visit: http://dawn.jpl.nasa.gov/mission

More information about Dawn is available at the following sites:

http://dawn.jpl.nasa.gov

http://www.nasa.gov/dawn

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

Best regards, Orbiter.ch

Saturn the Mighty

NASA - Cassini International logo.

Jan. 11, 2016

It is easy to forget just how large Saturn is, at around 10 times the diameter of Earth. And with a diameter of about 72,400 miles (116,500 kilometers), the planet simply dwarfs its retinue of moons. One of those satellites, Tethys (660 miles or 1,062 kilometers across), is seen here at lower right.

This view looks toward the sunlit side of the rings from about 8 degrees above the ring plane. The image was taken with the Cassini spacecraft wide-angle camera on March 7, 2015 using a spectral filter that preferentially admits wavelengths of near-infrared light centered at 752 nanometers.

Tethys has been brightened by a factor of 2 to increase its visibility.

The view was acquired at a distance of approximately 1.6 million miles (2.6 million kilometers) from Saturn. Image scale is 10 miles (16 kilometers) per pixel. Tethys is slightly closer at 1.5 million miles (2.4 million kilometers) away, for an image scale of 9 miles (14 kilometers) per pixel.

The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov or http://www.nasa.gov/cassini . The Cassini imaging team homepage is at http://ciclops.org and ESA's website: http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens

Image, Text, Credits: NASA/JPL-Caltech/Space Science Institute/Tony Greicius.

Greetings, Orbiter.ch

Starburst Spider

NASA - Mars Reconnaissance Orbiter (LRO) logo.

Jan. 11, 2016

Mars' seasonal cap of carbon dioxide ice has eroded many beautiful terrains as it sublimates (goes directly from ice to vapor) every spring. In the region where the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter took this image, we see troughs that form a starburst pattern. In other areas these radial troughs have been refered to as spiders, simply because of their shape. In this region the pattern looks more dendritic as channels branch out numerous times as they get further from the center.

The troughs are believed to be formed by gas flowing beneath the seasonal ice to openings where the gas escapes, carrying along dust from the surface below. The dust falls to the surface of the ice in fan-shaped deposits.

This image, covering an area about 1 kilometer (0.6 mile) across, is a portion of the HiRISE observation catalogued as ESP_011842_0980, taken on Feb. 4, 2009. The observation is centered at 81.8 degrees south latitude, 76.2 degrees east longitude. The image was taken at a local Mars time of 4:56 p.m. and the scene is illuminated from the west with a solar incidence angle of 78 degrees, thus the sun was about 12 degrees above the horizon. At a solar longitude of 203.6 degrees, the season on Mars is northern autumn.

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, is the prime contractor for the project and built the spacecraft. The High Resolution Imaging Science Experiment is operated by the University of Arizona, Tucson, and the instrument was built by Ball Aerospace & Technologies Corp., Boulder, Colo.

Related link:

HiRISE observation catalogued as ESP_011842_0980: http://hirise.lpl.arizona.edu/ESP_011842_0980

For more information about Mars Reconnaissance Orbiter (MRO), visit: http://www.nasa.gov/mission_pages/MRO/main/index.html

Image, Text, Credits: NASA/JPL-Caltech/University of Arizona/NASA Administrator, Charles F. Bolden.

Greetings, Orbiter.ch

Weekly Recap From the Expedition Lead Scientist Jan. 11, 2016

ISS - Expedition 46 Mission patch.

Jan. 11, 2016

The crew of the International Space Station kicked off the new year with science investigations in to aging of human skin and how fabrics burn in space, both of which could have a significant impact on life on Earth.

NASA astronaut Scott Kelly retrieved the hardware for the Burning and Suppression of Solids-Milliken (BASS-M) investigation scheduled to begin within the next few weeks. Materials burn differently in microgravity than they do on Earth, and understanding these differences is crucial for maintaining safety. This NASA investigation tests 10 specially treated, flame-retardant cotton fabrics to determine how well they resist burning in microgravity.

Image above: JAXA (Japan Aerospace Exploration Agency) astronaut Akihiko Hoshide performs a Sprint ultrasound pre-scan during Expedition 32 on the International Space Station in August 2012. Ultrasound scans are used to evaluate spaceflight-induced changes in the muscle volume to determine the effectiveness of exercises to combat muscle and bone loss. Image Credit: NASA.

The important observations from BASS-M experiments include flame shape and appearance as a function of airflow speed around the sample, how fast the flame develops, and flame dynamics -- pulsations and oscillations. Each textile’s ability to self-extinguish is evaluated and compared against normal terrestrial behavior. Results benefit research on flame-retardant textiles that can be used on Earth and in space.

Image above: A composite image of candle flames from the Burning and Suppression of Solids (BASS) investigation on the International Space Station. Image Credit: NASA.

ESA (European Space Agency) astronaut Tim Peake performed his first round of measurements for the Skin-B investigation. The ESA investigation will improve understanding of skin aging, which is slow on Earth but accelerated in space. It will provide insight into the aging process in other similar bodily tissues and could help scientists identify impacts for astronauts on future long-duration missions beyond low Earth orbit where environmental conditions are more challenging.

Peake measured the hydration level of his skin’s outer layer, the skin barrier function and the skin surface topography. The data will be compared to measurements performed before Peake began his stay on the space station. Data gathered on the station can provide insight into the mechanisms by which all organs covered with epithelial and connective tissue adapt and age over time and under the physical stress imposed by the microgravity environment. Gaining an understanding of how biological tissue can change should allow for better diagnostic and treatment on Earth.

One proven treatment to maintain the health of crew members is regular exercise on the orbiting laboratory. NASA astronaut Tim Kopra completed an ultrasound on different muscle groups for the end of his second week on the space station as part of the Integrated Resistance and Aerobic Training Study (Sprint). This NASA Human Research Program study evaluates the use of high intensity, low volume exercise training to minimize loss of muscle, bone and cardiovascular function in crew members during long-duration missions.

Happy New Year from the International Space Station

Video above: ESA astronaut Tim Peak and NASA astronauts Tim Kopra and Scott Kelly wished the people of Earth a Happy New Year from the International Space Station. Kelly is starting the 10th month of a year-long mission on the orbital laboratory, while Kopra and Peake arrived Dec. 15 to begin a six-month mission on the complex. Video Credit: NASA-TV.

Ultrasound scans are used to evaluate spaceflight-induced changes in the muscle volume. Upon completion of this study, investigators expect to provide an integrated resistance and aerobic exercise training protocol capable of maintaining muscle, bone and cardiovascular health while reducing total exercise time over the course of a long-duration spaceflight. This will provide valuable information in support of the long-term goal of protecting human fitness for even longer space exploration missions. Data gathered from the investigation also may help scientists develop treatments to aid in muscle, bone and heart health on Earth.

Other human research investigations this week included Biochemical Profile, Cardio-Ox, Cognition, Dose Tracker, Fine Motor Skills, Fluid Shifts, Habitability, Journals, Microbiome, Salivary Markers, Telomeres, Ocular Health, Sleep Log, and Space Headaches.

Progress made on other investigations and facilities this week included VEG-01, OASIS, MGM, RaDI-N2, CIR, GLACIER, and EXPRESS Racks.

Related links:

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

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

Burning and Suppression of Solids-Milliken (BASS-M): http://www.nasa.gov/mission_pages/station/research/experiments/2123.html

Skin-B investigation: http://www.nasa.gov/mission_pages/station/research/experiments/1166.html

Integrated Resistance and Aerobic Training Study (Sprint): http://www.nasa.gov/mission_pages/station/research/experiments/972.html

Images (mentioned), Video (mentioned), Text, Credits: NASA/Kristine Rainey.

Best regards, Orbiter.ch

Dark pools on Titan

NASA & ESA - Cassini-Huygens Mission to Saturn & Titan patch.

Jan. 11, 2016

This radar image from the Cassini orbiter shows a thin strip of surface on Saturn’s moon Titan. The yellow-hued terrain appears to be peppered with blue-tinted lakes and seas. However, these would not be much fun to splash around in – rather than containing water, they are filled with liquid methane.

Cassini has been orbiting Saturn since 2004, and has studied Titan in detail. Alongside the Cassini orbiter was the Huygens probe, which separated from the orbiter on 25 December 2004 and landed on Titan 11 years ago this week, on 14 January 2005. This was the first landing on an outer Solar System body.

As intended, Huygens sent back data for a short time after landing – about 72 minutes – before its mission ended. The probe provided a unique insight into the moon’s dense nitrogen-rich atmosphere during the descent, and gathered in situ measurements of the surface.

One of its discoveries was that the landing site resembled a dried lakebed, and there were channels and valleys nearby, hinting at the sporadic presence of surface liquid. A year later the presence of liquid-filled lakes was confirmed, making Titan the only Solar System body other than Earth known to have liquid lakes and seas on its surface.

This image is made from observations gathered during a flyby of Titan on 22 July 2006, when the orbiter was about 950 km from the moon’s surface. It has been coloured to give a rough approximation of what Cassini saw – it does not reflect what the human eye would see.

Brighter regions that strongly reflected Cassini’s radar signal look different from regions that reflected the signal weakly: bright areas show up as a tan–yellow shade, while less reflective regions appear as dark, mottled patches. These patches have also been tinted blue to make them even clearer; this is a research technique used by scientists to enhance and highlight various features and details in their observations.

Although Huygens’ mission is over, we have many more opportunities to explore Titan with Cassini. The orbiter will perform nearly 40 more flybys of Titan before the mission ends in September 2017. These will range from close flybys at just under 1000 km, like the one responsible for this image, to more distant ones when the moon will be seen from a vantage point up to a million kilometers away.

This image was originally published on 3 January 2007.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov or http://www.nasa.gov/cassini . The Cassini imaging team homepage is at http://ciclops.org and ESA's website: http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens

Image, Text, Credits: ESA/NASA/JPL/USGS.

Greetings, Orbiter.ch