sexta-feira, 30 de setembro de 2016

NASA WEB · Final Descent Image from Rosetta Spacecraft

NASA JPL latest news release
Final Descent Image from Rosetta SpacecraftA new image of comet 67P/Churyumov-Gerasimenko was taken by the European Space Agency's (ESA) Rosetta spacecraft shortly before its controlled impact into the comet's surface on Sept. 30, 2016. Confirmation of the end of the mission arrived at ESA's European Space Operations Center in Darmstadt, Germany, at 4:19 a.m. PDT (7:19 a.m. EDT / 1:19 p.m. CEST) with the loss of signal upon impact.
The final descent gave Rosetta the opportunity to study the comet's gas, dust and plasma environment very close to its surface, as well as take very high-resolution images.
The image was taken from an altitude of 167 feet (51 meters) above the comet's surface by the spacecraft's OSIRIS wide-angle camera on Sept. 30.?The image scale is about two-tenths of an inch (5 millimeters) per pixel. The image measures about 9 feet (2.4 meters) across.
The decision to end the mission on the surface is a result of Rosetta and the comet heading out beyond the orbit of Jupiter again. Farther from the sun than Rosetta had ever journeyed before, there would be little power to operate the craft. Mission operators were also faced with an imminent month-long period when the sun is close to the line-of-sight between Earth and Rosetta, meaning communications with the craft would have become increasingly more difficult.
The European Space Agency's Rosetta mission was launched in 2004 and arrived at comet 67P/Churyumov-Gerasimenko on Aug. 6, 2014. It is the first mission in history to rendezvous with a comet and escort it as it orbits the sun. On Nov. 4, 2014, a smaller lander name Philae, which had been deployed from the Rosetta mothership, touched down on the comet and bounced several times before finally alighting on the surface. Philae obtained the first images taken from a comet's surface and sent back valuable scientific data for several days.
U.S. contributions aboard the Rosetta spacecraft are the Microwave Instrument for Rosetta Orbiter (MIRO); the Alice spectrograph; the Ion and Electron Sensor (IES), part of the Rosetta Plasma Consortium Suite; and the Double Focusing Mass Spectrometer (DFMS) electronics package for the Rosetta Orbiter Spectrometer for Ion Neutral Analysis (ROSINA). They are part of a suite of 11 total science instruments aboard Rosetta.
Comets are time capsules containing primitive material left over from the epoch when the sun and its planets formed. Rosetta is the first spacecraft to witness at close proximity how a comet changes as it is subjected to the increasing intensity of the sun's radiation. Observations will help scientists learn more about the origin and evolution of our solar system and the role comets may have played in the formation of planets.
Rosetta is an ESA mission with contributions from its member states and NASA. Rosetta's Philae lander is provided by a consortium led by the German Aerospace Center, Cologne; Max Planck Institute for Solar System Research, Gottingen; French National Space Agency, Paris; and the Italian Space Agency, Rome. NASA's Jet Propulsion Laboratory, Pasadena, California, a division of Caltech, manages the U.S. contribution of the Rosetta mission for NASA's Science Mission Directorate in Washington. JPL also built the MIRO and hosts its principal investigator, Mark Hofstadter. The Southwest Research Institute (San Antonio and Boulder, Colorado), developed the Rosetta orbiter's IES and Alice instruments and hosts their principal investigators, James Burch (IES) and Alan Stern (Alice).
For more information on the U.S. instruments aboard Rosetta,

NASA WEB-Curiosity Finds Evidence of Mars Crust Contributing to Atmosphere

Processes in Mars' surface material can explain why particular xenon (Xe) and krypton (Kr) isotopes are more abundant in the Martian atmosphere than expected, as measured by NASA's Curiosity rover. Cosmic rays striking barium (Ba) or bromine (Br) atoms can alter isotopic ratios of xenon and krypton. Credit: NASA/GSFC/JPL-Caltech
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NASA's Curiosity rover has found evidence that chemistry in the surface material on Mars contributed dynamically to the makeup of its atmosphere over time. It's another clue that the history of the Red Planet's atmosphere is more complex and interesting than a simple legacy of loss.
The findings come from the rover's Sample Analysis at Mars, or SAM, instrument suite, which studied the gases xenon and krypton in Mars' atmosphere. The two gases can be used as tracers to help scientists investigate the evolution and erosion of the Martian atmosphere. A lot of information about xenon and krypton in Mars' atmosphere came from analyses of Martian meteorites and measurements made by the Viking mission.
"What we found is that earlier studies of xenon and krypton only told part of the story," said Pamela Conrad, lead author of the report and SAM's deputy principal investigator at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "SAM is now giving us the first complete in situ benchmark against which to compare meteorite measurements."
Of particular interest to scientists are the ratios of certain isotopes - or chemical variants - of xenon and krypton. The SAM team ran a series of first-of-a-kind experiments to measure all the isotopes of xenon and krypton in the Martian atmosphere. The experiments are described in a paper published in Earth and Planetary Science Letters.
The team's method is called static mass spectrometry, and it's good for detecting gases or isotopes that are present only in trace amounts. Although static mass spectrometry isn't a new technique, its use on the surface of another planet is something only SAM has done.
Overall, the analysis agreed with earlier studies, but some isotope ratios were a bit different than expected. When working on an explanation for those subtle but important differences, the researchers realized that neutrons might have gotten transferred from one chemical element to another within the surface material on Mars. The process is called neutron capture, and it would explain why a few selected isotopes were more abundant than previously thought possible.
In particular, it looks as if some of the barium surrendered neutrons that got picked up by xenon to produce higher-than-expected levels of the isotopes xenon-124 and 126. Likewise, bromine might have surrendered some of its neutrons to produce unusual levels of krypton-80 and krypton-82.
These isotopes could have been released into the atmosphere by impacts on the surface and by gas escaping from the regolith, which is the soil and broken rocks of the surface.
"SAM's measurements provide evidence of a really interesting process in which the rock and unconsolidated material at the planet's surface have contributed to the xenon and krypton isotopic composition of the atmosphere in a dynamic way," said Conrad.
The atmospheres of Earth and Mars exhibit very different patterns of xenon and krypton isotopes, particularly for xenon-129. Mars has much more of it in the atmosphere than does Earth.
"The unique capability to measure in situ the six and nine different isotopes of krypton and xenon allows scientists to delve into the complex interactions between the Martian atmosphere and crust," said Michael Meyer, lead scientist for the Mars Exploration Program at NASA Headquarters in Washington. "Discovering these interactions through time allows us to gain a greater understanding of planetary evolution."
NASA's Mars Science Laboratory Project is using Curiosity to determine if life was possible on Mars and study major changes in Martian environmental conditions. NASA studies Mars to learn more about our own planet, and in preparation for future human missions to Mars. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the project for NASA's Science Mission Directorate in Washington.

segunda-feira, 26 de setembro de 2016

NASA WEB ·Hubble: Possible Water Plumes on Jupiter's Moon Europa

This composite image shows suspected plumes of water vapor erupting at the 7 o'clock position off the limb of Jupiter's moon Europa. The plumes, photographed by NASA's Hubble's Space Telescope Imaging Spectrograph, were seen in silhouette as the moon passed in front of Jupiter. Credits: NASA/ESA/W. Sparks (STScI)/USGS Astrogeology Science Center
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Astronomers using NASA's Hubble Space Telescope have imaged what may be water vapor plumes erupting off the surface of Jupiter's moon Europa. This finding bolsters other Hubble observations suggesting the icy moon erupts with high altitude water vapor plumes.
The observation increases the possibility that missions to Europa may be able to sample Europa's ocean without having to drill through miles of ice.
"Europa's ocean is considered to be one of the most promising places that could potentially harbor life in the solar system," said Geoff Yoder, acting associate administrator for NASA's Science Mission Directorate in Washington. "These plumes, if they do indeed exist, may provide another way to sample Europa's subsurface."
The plumes are estimated to rise about 125 miles (200 kilometers) before, presumably, raining material back down onto Europa's surface. Europa has a huge global ocean containing twice as much water as Earth's oceans, but it is protected by a layer of extremely cold and hard ice of unknown thickness. The plumes provide a tantalizing opportunity to gather samples originating from under the surface without having to land or drill through the ice.
The team, led by William Sparks of the Space Telescope Science Institute in Baltimore observed these finger-like projections while viewing Europa's limb as the moon passed in front of Jupiter.

The original goal of the team's observing proposal was to determine whether Europa has a thin, extended atmosphere, or exosphere. Using the same observing method that detects atmospheres around planets orbiting other stars, the team realized if there was water vapor venting from Europa's surface, this observation would be an excellent way to see it.
"The atmosphere of an extrasolar planet blocks some of the starlight that is behind it," Sparks explained. "If there is a thin atmosphere around Europa, it has the potential to block some of the light of Jupiter, and we could see it as a silhouette. And so we were looking for absorption features around the limb of Europa as it transited the smooth face of Jupiter."
In 10 separate occurrences spanning 15 months, the team observed Europa passing in front of Jupiter. They saw what could be plumes erupting on three of these occasions.
This work provides supporting evidence for water plumes on Europa. In 2012, a team led by Lorenz Roth of Southwest Research Institute in San Antonio detected evidence of water vapor erupting from the frigid south polar region of Europa and reaching more than100 miles (160 kilometers) into space. Although both teams used Hubble's Space Telescope Imaging Spectrograph instrument, each used a totally independent method to arrive at the same conclusion.
"When we calculate in a completely different way the amount of material that would be needed to create these absorption features, it's pretty similar to what Roth and his team found," Sparks said. "The estimates for the mass are similar, the estimates for the height of the plumes are similar. The latitude of two of the plume candidates we see corresponds to their earlier work."
But as of yet, the two teams have not simultaneously detected the plumes using their independent techniques. Observations thus far have suggested the plumes could be highly variable, meaning that they may sporadically erupt for some time and then die down. For example, observations by Roth's team within a week of one of the detections by Sparks' team failed to detect any plumes.
If confirmed, Europa would be the second moon in the solar system known to have water vapor plumes. In 2005, NASA's Cassini orbiter detected jets of water vapor and dust spewing off the surface of Saturn's moon Enceladus.
Scientists may use the infrared vision of NASA's James Webb Space Telescope, which is scheduled to launch in 2018, to confirm venting or plume activity on Europa. NASA also is formulating a mission to Europa with a payload that could confirm the presence of plumes and study them from close range during multiple flybys.
"Hubble's unique capabilities enabled it to capture these plumes, once again demonstrating Hubble's ability to make observations it was never designed to make," said Paul Hertz, director of the Astrophysics Division at NASA Headquarters in Washington. "This observation opens up a world of possibilities, and we look forward to future missions -- such as the James Webb Space Telescope -- to follow-up on this exciting discovery."
The work by Sparks and his colleagues is published in the Sept. 29 issue of the Astrophysical Journal.
Planetary scientist Kevin Hand of NASA's Jet Propulsion Laboratory, Pasadena, California, co-authored the new paper.
The Hubble Space Telescope is a project of international cooperation between NASA and ESA (the European Space Agency.) NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute, which is operated for NASA by the Association of Universities for Research in Astronomy in Washington, conducts Hubble science operations.

sexta-feira, 2 de setembro de 2016

NASA WEB ·SpaceX Falcon 9 Explodes During Routine Test

SpaceX Falcon 9 Explodes During Routine Test

A SpaceX Falcon 9 rocket blew up today at Cape Canaveral Air Force Station during preparations for a routine static engine firing. The rocket and its Amos-6 payload were destroyed. The exact cause of the explosion is unknown at the present time.
According to SpaceX: "SpaceX can confirm that in preparation for today's static fire, there was an anomaly on the pad resulting in the loss of the vehicle and its payload. Per standard procedure, the pad was clear and there were no injuries."
Elon Musk Tweeted "Loss of Falcon vehicle today during propellant fill operation. Originated around upper stage oxygen tank. Cause still unknown. More soon."

NASA WEB ·Copernicus Sentinel-1A Hit By Space Debris

Copernicus Sentinel-1A Hit By Space Debris

Space debris impact site
ESA engineers have discovered that a solar panel on the Copernicus Sentinel-1A satellite was hit by a millimetre-size particle in orbit on 23 August.
Thanks to onboard cameras, ground controllers were able to identify the affected area. So far, there has been no effect on the satellite's routine operations.
A sudden small power reduction was observed in a solar array of Sentinel-1A, orbiting at 700 km altitude, at 17:07 GMT on 23 August. Slight changes in the orientation and the orbit of the satellite were also measured at the same time.
Following a preliminary investigation, the operations team at ESA's control centre in Darmstadt, Germany suspected a possible impact by space debris or micrometeoroid on the solar wing.
Detailed analyses of the satellite's status were performed to understand the cause of this power loss. In addition, the engineers decided to activate the board cameras to acquire pictures of the array. These cameras were originally carried to monitor the deployment of the solar wings, which occurred just a few hours after launch in April 2014, and were not intended to be used afterwards.
Following their switch-on, one camera provided a picture that clearly shows the strike on the solar panel.
The power reduction is relatively small compared to the overall power generated by the solar wing, which remains much higher than what the satellite requires for routine operations.
"Such hits, caused by particles of millimetre size, are not unexpected," notes Holger Krag, Head of the Space Debris Office at ESA's establishment in Darmstadt, Germany.
"These very small objects are not trackable from the ground, because only objects greater than about 5 cm can usually be tracked and, thus, avoided by manoeuvring the satellites.
"In this case, assuming the change in attitude and the orbit of the satellite at impact, the typical speed of such a fragment, plus additional parameters, our first estimates indicate that the size of the particle was of a few millimetres.
"Analysis continues to obtain indications on whether the origin of the object was natural or man-made. The pictures of the affected area show a diameter of roughly 40 cm created on the solar array structure, confirming an impact from the back side, as suggested by the satellite's attitude rate readings."
This event has no effect on the satellite's routine operations, which continue normally.
The Sentinel-1 satellites, part of the European Union's Copernicus Programme, are operated by ESA on behalf of the European Commission.

NASA WEB ·Volcanoes on Ceres Erupt Ice

Volcanoes on Ceres Erupt Ice

Ahuna Mons
Ahuna Mons is a volcano that rises 13,000 feet high and spreads 11 miles wide at its base. This would be impressive for a volcano on Earth. But Ahuna Mons stands on Ceres, a dwarf planet less than 600 miles wide that orbits the Sun between Mars and Jupiter.
Even stranger, Ahuna Mons isn't built from lava the way terrestrial volcanoes are -- it's built from ice.
"Ahuna is the one true 'mountain' on Ceres," said David Williams, associate research professor in Arizona State University's School of Earth and Space Exploration. "After studying it closely, we interpret it as a dome raised by cryovolcanism."
This is a form of low-temperature volcanic activity, where molten ice -- water, usually mixed with salts or ammonia -- replaces the molten silicate rock erupted by terrestrial volcanoes. Giant mountain Ahuna is a volcanic dome built from repeated eruptions of freezing salty water.
Williams is part of a team of scientists working with NASA's Dawn mission who have published papers in the journal Science this week []. His specialty is volcanism, and that drew him to the puzzle of Ahuna Mons.
"Ahuna is truly unique, being the only mountain of its kind on Ceres," he said. "It shows nothing to indicate a tectonic formation, so that led us to consider cryovolcanism as a method for its origin."
Dawn scientist Ottaviano Ruesch, of NASA's Goddard Space Flight Center, Greenbelt, Maryland, is the lead author on the Science paper about Ceres volcanism. He says, "This is the only known example of a cryovolcano that potentially formed from a salty mud mix, and which formed in the geologically recent past."
Williams explained that "Ahuna has only a few craters on its surface, which points to an age of just couple hundred million years at most."
According to the Dawn team, the implications of Ahuna Mons being volcanic in origin are enormous. It confirms that although Ceres' surface temperature averages almost -40° (Celsius or Fahrenheit; the scales converge at this temperature), its interior has kept warm enough for liquid water or brines to exist for a relatively long period. And this has allowed volcanic activity at the surface in recent geological time.
Ahuna Mons is not the only place where icy volcanism happens on Ceres. Dawn's instruments have spotted features that point to cryovolcanic activity that resurfaces areas rather than building tall structures. Numerous craters, for example, show floors that appear flatter than impacts by meteorites would leave them, so perhaps they have been flooded from below. In addition, such flat-floored craters often show cracks suggesting that icy "magma" has pushed them upward, then subsided.
A few places on Ceres exhibit a geo-museum of features. "Occator Crater has several bright spots on its floor," said Williams. "The central spot contains what looks like a cryovolcanic dome, rich in sodium carbonates." Other bright spots, he says, occur over fractures that suggest venting of water vapor mixed with bright salts.
"As the vapor has boiled away," he explained, "it leaves the bright salts and carbonate minerals behind."
Looking Inside
Although volcanic-related features appear across the surface of Ceres, for scientists perhaps the most interesting aspect is what these features say about the interior of the dwarf world. Dawn observations suggest that Ceres has an outer shell that's not purely ice or rock, but rather a mixture of both.
Recently, Williams was involved in research that discovered that large impact craters are missing, presumably erased by internal heat, but smaller craters are preserved. "This shows that Ceres' crust has a variable composition -- it's weak at large scales but strong at smaller scales," he said. "It has also evolved geologically."
In the big picture, said Williams, "Ceres appears differentiated internally, with a core and a complex crust made of 30 to 40 percent water ice mixed with silicate rock and salts." And perhaps pockets of brine still exist in its interior.
"We need to continue studying the data to better understand the interior structure of Ceres," said Williams.
Ceres is the second port of call for the Dawn mission, which was launched in 2007 and visited another asteroid, Vesta, from 2011 to 2012. The spacecraft arrived at Ceres in March 2015. It carries a suite of cameras, spectrometers, and gamma-ray and neutron detectors. These were built to image, map, and measure the shape and surface materials of Ceres, and they collect information to help scientists understand the history of these small worlds and what they can tell us of the solar system's birth.
NASA plans for Dawn to continue orbiting Ceres and collecting data for another year or so. The dwarf planet is slowly moving toward its closest approach to the Sun, called perihelion, which will come in April 2018. Scientists expect that the growing solar warmth will produce some detectable changes in Ceres' surface or maybe even trigger volcanic activity.
"We hope that by observing Ceres as it approaches perihelion, we might see some active venting. This would be an ideal way to end the mission," said Williams.
Primary image caption: Volcanic dome Ahuna Mons rises above a foreground impact crater, as seen by NASA's Dawn spacecraft with no vertical exaggeration. Eruptions of salty, muddy water built the mountain by repeated eruptions, flows, and freezing. Streaks from falls of rocks and debris run down its flanks, while overhead views show fracturing across its summit. Credit: Dawn Science Team and NASA/JPL-Caltech/GSFC

quinta-feira, 1 de setembro de 2016

NASA WEB- Dawn Sets Course for Higher Orbit

NASA JPL latest news release
Dawn Sets Course for Higher OrbitAfter studying Ceres for more than eight months from its low-altitude science orbit, NASA's Dawn spacecraft will move higher up for different views of the dwarf planet.
Dawn has delivered a wealth of images and other data from its current perch at 240 miles (385 kilometers) above Ceres' surface, which is closer to the dwarf planet than the International Space Station is to Earth. Now, the mission team is pivoting to consider science questions that can be examined from higher up.
After Dawn completed its prime mission on June 30, having surpassed all of its scientific objectives at Vesta and at Ceres, NASA extended the mission to perform new studies of Ceres. One of the factors limiting Dawn's lifetime is the amount of hydrazine, the propellant needed to orient the spacecraft to observe Ceres and communicate with Earth. By going to a higher orbit at Ceres, Dawn will use the remaining hydrazine more sparingly, because it won't have to work as hard to counter Ceres' gravitational pull.
"Most spacecraft wouldn't be able to change their orbital altitude so easily. But thanks to Dawn's uniquely capable ion propulsion system, we can maneuver the ship to get the greatest scientific return from the mission," said Marc Rayman, chief engineer and mission director, based at NASA's Jet Propulsion Laboratory, Pasadena, California.
On Sept. 2, Dawn will begin spiraling upward to about 910 miles (1,460 kilometers) from Ceres. The altitude will be close to where Dawn was a year ago, but the orientation of the spacecraft's orbit -- specifically, the angle between the orbit plane and the sun -- will be different this time, so the spacecraft will have a different view of the surface.
The mission team is continuing to develop the extended mission itinerary and will submit a full plan to NASA next month.
Dawn's mission is managed by JPL for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute are international partners on the mission team. For a complete list of mission participants