terça-feira, 28 de junho de 2016

NASA WEB ·DISCOVERY-NASA Rover Findings Point to a More Earth-like Martian Past

Curiosity rover on Mars with inset images
This scene shows NASA's Curiosity Mars rover at a location called "Windjana," where the rover found rocks containing manganese-oxide minerals, which require abundant water and strongly oxidizing conditions to form.Credit: NASA/JPL-Caltech/MSSS 
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Chemicals found in Martian rocks by NASA's Curiosity Mars rover suggest the Red Planet once had more oxygen in its atmosphere than it does now.
Researchers found high levels of manganese oxides by using a laser-firing instrument on the rover. This hint of more oxygen in Mars' early atmosphere adds to other Curiosity findings -- such as evidence about ancient lakes -- revealing how Earth-like our neighboring planet once was.
This research also adds important context to other clues about atmospheric oxygen in Mars' past. The manganese oxides were found in mineral veins within a geological setting the Curiosity mission has placed in a timeline of ancient environmental conditions. From that context, the higher oxygen level can be linked to a time when groundwater was present in the rover's Gale Crater study area.
"The only ways on Earth that we know how to make these manganese materials involve atmospheric oxygen or microbes," said Nina Lanza, a planetary scientist at Los Alamos National Laboratory in New Mexico. "Now we're seeing manganese oxides on Mars, and we're wondering how the heck these could have formed?"
Microbes seem far-fetched at this point, but the other alternative -- that the Martian atmosphere contained more oxygen in the past than it does now -- seems possible, Lanza said. "These high manganese materials can't form without lots of liquid water and strongly oxidizing conditions. Here on Earth, we had lots of water but no widespread deposits of manganese oxides until after the oxygen levels in our atmosphere rose."
Lanza is the lead author of a new report about the Martian manganese oxides in the American Geophysical Union's Geophysical Research Letters. She uses Curiosity's Chemistry and Camera (ChemCam) instrument, which fires laser pulses from atop the rover's mast and observes the spectrum of resulting flashes of plasma to assess targets' chemical makeup.
In Earth's geological record, the appearance of high concentrations of manganese oxide minerals is an important marker of a major shift in our atmosphere's composition, from relatively low oxygen abundances to the oxygen-rich atmosphere we see today. The presence of the same types of materials on Mars suggests that oxygen levels rose there, too, before declining to their present values. If that's the case, how was that oxygen-rich environment formed?
"One potential way that oxygen could have gotten into the Martian atmosphere is from the breakdown of water when Mars was losing its magnetic field," said Lanza. "It's thought that at this time in Mars' history, water was much more abundant." Yet without a protective magnetic field to shield the surface, ionizing radiation started splitting water molecules into hydrogen and oxygen. Because of Mars' relatively low gravity, the planet wasn't able to hold onto the very light hydrogen atoms, but the heavier oxygen atoms remained behind. Much of this oxygen went into rocks, leading to the rusty red dust that covers the surface today. While Mars' famous red iron oxides require only a mildly oxidizing environment to form, manganese oxides require a strongly oxidizing environment, more so than previously known for Mars.
Lanza added, "It's hard to confirm whether this scenario for Martian atmospheric oxygen actually occurred. But it's important to note that this idea represents a departure in our understanding for how planetary atmospheres might become oxygenated." Abundant atmospheric oxygen has been treated as a so-called biosignature, or a sign of extant life, but this process does not require life.
Curiosity has been investigating sites in Gale Crater since 2012. The high-manganese materials it found are in mineral-filled cracks in sandstones in the "Kimberley" region of the crater. But that's not the only place on Mars where high manganese abundances have been found. NASA's Opportunity rover, exploring Mars since 2004, also recently discovered high manganese deposits thousands of miles from Curiosity. This supports the idea that the conditions needed to form these materials were present well beyond Gale Crater.
Los Alamos National Laboratory leads the U.S. and French team that jointly developed and operates ChemCam. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, built the rover and manages the Curiosity mission for NASA's Science Mission Directorate, Washington.

quinta-feira, 23 de junho de 2016

NASA WEB-NASA DISCOVERY-NASA Scientists Discover Unexpected Mineral on Mars

NASA JPL latest news release
NASA Scientists Discover Unexpected Mineral on Mars
Scientists have discovered an unexpected mineral in a rock sample at Gale Crater on Mars, a finding that may alter our understanding of how the planet evolved.
NASA's Mars Science Laboratory rover, Curiosity, has been exploring sedimentary rocks within Gale Crater since landing in August 2012. In July 2015, on Sol 1060 (the number of Martian days since landing), the rover collected powder drilled from rock at a location named "Buckskin." Analyzing data from an X-ray diffraction instrument on the rover that identifies minerals, scientists detected significant amounts of a silica mineral called tridymite.
This detection was a surprise to the scientists, because tridymite is generally associated with silicic volcanism, which is known on Earth but was not thought to be important or even present on Mars.
The discovery of tridymite might induce scientists to rethink the volcanic history of Mars, suggesting that the planet once had explosive volcanoes that led to the presence of the mineral.
Scientists in the Astromaterials Research and Exploration Science (ARES) Division at NASA's Johnson Space Center in Houston led the study. A paper on the team's findings has been published in the Proceedings of the National Academy of Sciences.
"On Earth, tridymite is formed at high temperatures in an explosive process called silicic volcanism. Mount St. Helens, the active volcano in Washington State, and the Satsuma-Iwojima volcano in Japan are examples of such volcanoes. The combination of high silica content and extremely high temperatures in the volcanoes creates tridymite," said Richard Morris, NASA planetary scientist at Johnson and lead author of the paper. "The tridymite was incorporated into 'Lake Gale' mudstone at Buckskin as sediment from erosion of silicic volcanic rocks."
The paper also will stimulate scientists to re-examine the way tridymite forms. The authors examined terrestrial evidence that tridymite could form at low temperatures from geologically reasonable processes and not imply silicic volcanism. They found none. Researchers will need to look for ways that it could form at lower temperatures.
"I always tell fellow planetary scientists to expect the unexpected on Mars," said Doug Ming, ARES chief scientist at Johnson and co-author of the paper. "The discovery of tridymite was completely unexpected. This discovery now begs the question of whether Mars experienced a much more violent and explosive volcanic history during the early evolution of the planet than previously thought."

sexta-feira, 17 de junho de 2016

NASA WEB-NASA DISCOVERY-NASA's Juno Spacecraft to Risk Jupiter's Fireworks for Science

NASA JPL latest news release
NASA's Juno Spacecraft to Risk Jupiter's Fireworks for ScienceOn July 4, NASA will fly a solar-powered spacecraft the size of a basketball court within 2,900 miles (4,667 kilometers) of the cloud tops of our solar system's largest planet.
As of Thursday, Juno is 18 days and 8.6 million miles (13.8 million kilometers) from Jupiter. On the evening of July 4, Juno will fire its main engine for 35 minutes, placing it into a polar orbit around the gas giant. During the flybys, Juno will probe beneath the obscuring cloud cover of Jupiter and study its auroras to learn more about the planet's origins, structure, atmosphere and magnetosphere.
"At this time last year our New Horizons spacecraft was closing in for humanity's first close views of Pluto," said Diane Brown, Juno program executive at NASA Headquarters in Washington. "Now, Juno is poised to go closer to Jupiter than any spacecraft ever before to unlock the mysteries of what lies within."
A series of 37 planned close approaches during the mission will eclipse the previous record for Jupiter set in 1974 by NASA's Pioneer 11 spacecraft of 27,000 miles (43,000 kilometers). Getting this close to Jupiter does not come without a price -- one that will be paid each time Juno's orbit carries it toward the swirling tumult of orange, white, red and brown clouds that cover the gas giant.
"We are not looking for trouble, we are looking for data," said Scott Bolton, principal investigator of Juno from the Southwest Research Institute in San Antonio. "Problem is, at Jupiter, looking for the kind of data Juno is looking for, you have to go in the kind of neighborhoods where you could find trouble pretty quick."
The source of potential trouble can be found inside Jupiter itself. Well below the Jovian cloud tops is a layer of hydrogen under such incredible pressure it acts as an electrical conductor. Scientists believe that the combination of this metallic hydrogen along with Jupiter's fast rotation -- one day on Jupiter is only 10 hours long -- generates a powerful magnetic field that surrounds the planet with electrons, protons and ions traveling at nearly the speed of light. The endgame for any spacecraft that enters this doughnut-shaped field of high-energy particles is an encounter with the harshest radiation environment in the solar system.
"Over the life of the mission, Juno will be exposed to the equivalent of over 100 million dental X-rays," said Rick Nybakken, Juno's project manager from NASA's Jet Propulsion Laboratory in Pasadena, California. "But, we are ready. We designed an orbit around Jupiter that minimizes exposure to Jupiter's harsh radiation environment. This orbit allows us to survive long enough to obtain the tantalizing science data that we have traveled so far to get."
Juno's orbit resembles a flattened oval. Its design is courtesy of the mission's navigators, who came up with a trajectory that approaches Jupiter over its north pole and quickly drops to an altitude below the planet's radiation belts as Juno races toward Jupiter's south pole. Each close flyby of the planet is about one Earth day in duration. Then Juno's orbit will carry the spacecraft below its south pole and away from Jupiter, well beyond the reach of harmful radiation.
While Juno is replete with special radiation-hardened electrical wiring and shielding surrounding its myriad of sensors, the highest profile piece of armor Juno carries is a first-of-its-kind titanium vault, which contains the spacecraft's flight computer and the electronic hearts of many of its science instruments. Weighing in at almost 400 pounds (172 kilograms), the vault will reduce the exposure to radiation by 800 times of that outside of its titanium walls.
Without the vault, Juno's electronic brain would more than likely fry before the end of the very first flyby of the planet. But, while 400 pounds of titanium can do magical things, it can't do it forever in an extreme radiation environment like that on Jupiter. The quantity and energy of the high-energy particles is just too much. However, Juno's special orbit allows the radiation dose and the degradation to accumulate slowly, allowing Juno to do a remarkable amount of science for 20 months.
"Over the course of the mission, the highest-energy electrons will penetrate the vault, creating a spray of secondary photons and particles," said Heidi Becker of JPL, Juno's Radiation Monitoring Investigation lead. "The constant bombardment will break the atomic bonds in Juno's electronics."
The Juno spacecraft launched on Aug. 5, 2011 from Cape Canaveral, Florida.
JPL manages the Juno mission for the principal investigator, Scott Bolton, of Southwest Research Institute in San Antonio. Juno is part of NASA's New Frontiers Program, which is managed at NASA's Marshall Space Flight Center in Huntsville, Alabama, for NASA's Science Mission Directorate. Lockheed Martin Space Systems, Denver, built the spacecraft. The California Institute of Technology in Pasadena manages JPL for NASA.

terça-feira, 14 de junho de 2016

NASA WEB-DISCOVERY-Rover Opportunity Wrapping up Study of Martian Valley

"Marathon Valley" on Mars opens to a view across Endeavour Crater in this scene from the Pancam of NASA's Mars rover Opportunity. The scene merges many exposures taken during April and May 2016. The view spans from north (left) to west-southwest. Its foreground shows the valley's fractured texture. Image Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ. 
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"Marathon Valley," slicing through a large crater's rim on Mars, has provided fruitful research targets for NASA's Opportunity rover since July 2015, but the rover may soon move on.
Opportunity recently collected a sweeping panorama from near the western end of this east-west valley. The vista shows an area where the mission investigated evidence about how water altered the ancient rocks and, beyond that, the wide floor of Endeavour Crater and the crater's eastern rim about 14 miles (22 kilometers) away.
Marathon Valley lured the mission because researchers using NASA's Mars Reconnaissance Orbiter had mapped water-related clay minerals at this area of the western rim of Endeavour Crater. The rover team chose the valley's informal name because Opportunity's arrival at this part of the rim coincided closely with the rover surpassing marathon-footrace distance in total driving since its January 2004 Mars landing.
"We are wrapping up our last few activities in Marathon Valley and before long we'll drive away, exiting along the southern wall of the valley and heading southeast," said Opportunity Principal Investigator Steve Squyres, of Cornell University, Ithaca, New York.
As Opportunity examined the clay-bearing rocks on the valley floor that were detected from orbit, the rover's own observations of the valley's southern flank revealed streaks of red-toned, crumbly material. The science team chose to investigate this apparently weathered material. The rover approached exposures of it to prepare for using the Rock Abrasion Tool, called the RAT. This tool grinds away a rock's surface to expose the interior for inspection.
"What we usually do to investigate material that's captured our interest is find a bedrock exposure of it and use the RAT," Squyres said. "What we didn't realize until we took a close-enough look is that this stuff has been so pervasively altered, it's not bedrock. There's no solid bedrock you could grind with the RAT."
Instead, the rover exposed some fresh surfaces for inspection by scuffing some of the reddish material with a wheel.
Squyres said, "In the scuff, we found one of the highest sulfur contents that's been seen anywhere on Mars. There's strong evidence that, among other things, these altered zones have a lot of magnesium sulfate. We don't think these altered zones are where the clay is, but magnesium sulfate is something you would expect to find precipitating from water.
"Fractures running through the bedrock, forming conduits through which water could flow and transport soluble materials, could alter the rock and create the pattern of red zones that we see."
As of June 14, Opportunity has driven 26.59 miles (42.79 kilometers). NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, built the rover and manages the mission for NASA's Science Mission Directorate, Washington. For more information about Opportunity,

segunda-feira, 13 de junho de 2016

NASA WEB-NASA DISCOVERY-NASA Mars Rover Descends Plateau, Turns Toward Mountain

This graphic maps the first 14 sites where NASA's Curiosity Mars rover collected rock or soil samples
Rover's self-portrait

Rover's self-portrait
This May 11, 2016, self-portrait of NASA's Curiosity Mars rover shows the vehicle at the "Okoruso" drilling site on lower Mount Sharp's "Naukluft Plateau." The scene is a mosaic of multiple images taken with the arm-mounted Mars Hands Lens Imager (MAHLI). Credit: NASA/JPL-Caltech/MSSS 
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NASA's Curiosity Mars rover has analyzed its 12th drilled sample of Mars. This sample came from mudstone bedrock, which the rover resumed climbing in late May after six months studying other features.
Since the previous time Curiosity drilled into this "Murray formation" layer of lower Mount Sharp, the mission has examined active sand dunes along the rover's route, then crossed a remnant plateau of fractured sandstone that once more extensively covered the Murray formation.
While on the "Naukluft Plateau," the rover examined its 10th and 11th drill targets to repeat an experiment comparing material within and away from pale zones around fractures. From there, Curiosity also took the latest in a series of self-portraits.
"Now that we've skirted our way around the dunes and crossed the plateau, we've turned south to climb the mountain head-on," said Curiosity Project Scientist Ashwin Vasavada, of NASA's Jet Propulsion Laboratory, Pasadena, California. "Since landing, we've been aiming for this gap in the terrain and this left turn. It's a great moment for the mission."
Curiosity landed near Mount Sharp in 2012. It reached the base of the mountain in 2014 after successfully finding evidence on the surrounding plains that ancient Martian lakes offered conditions that would have been favorable for microbes if Mars has ever hosted life. Rock layers forming the base of Mount Sharp accumulated as sediment within ancient lakes billions of years ago.
The Murray formation is about one-eighth of a mile (200 meters) thick. So far, Curiosity has examined about one-fifth of its vertical extent.
"The story that the Murray formation is revealing about the habitability of ancient Mars is one of the mission's surprises," Vasavada said. "It wasn't obvious from pre-mission data that it formed in long-lived lakes and that its diverse composition would tell us about the chemistry of those lakes and later groundwater."
The latest sample-collection target, "Oudam," was drilled on June 4. On the Naukluft Plateau, Curiosity drilled "Lubango," within a halo of brighter sandstone near a fracture, and "Okoruso," away from a fracture-related halo, for comparison. The mission conducted a similar experiment last year, with two sample targets drilled at another exposure of the fractured sandstone.
This sandstone unit, called the Stimson formation, is interpreted to have resulted from wind that draped a band of sand dunes over lower Mount Sharp. That would have been after the main stack of the mountain's lower layers had formed and partially eroded. Water later moved through fractures in the sandstone. Investigation of the fracture-related halos aims to determine how fluid moved through the fractures and altered surrounding rock.
"We were about to drive off the Naukluft Plateau and leave the Stimson formation forever as we go up Mount Sharp," said Curiosity science-team member Albert Yen of JPL. "A few of us were concerned. The fracture-associated haloes were becoming more prevalent, and we had only one data point. With just one data point, you never know whether it is representative."
As with the similar previous experiment, comparison of Lubango and Okoruso found higher silica and sulfate levels in the sample nearer to the fracture. Multiple episodes of groundwater flow with different chemistry at different times may have both delivered silica and sulfate from elsewhere and leached other ingredients away.
"The big-picture story is that this may be one of the youngest fluid events we're likely to study with Curiosity," Yen said. "You had to lay down the Murray, then cement it, then lay down the Stimson and cement that, then fracture the Stimson, then have fluids moving through the fractures."
On Mount Sharp, Curiosity is investigating how and when the habitable ancient conditions known from the mission's earlier findings evolved into conditions drier and less favorable for life. For more information about Curiosity

quinta-feira, 9 de junho de 2016

NASA WEB-NASA DISCOVERY-NASA Mars Orbiters Reveal Seasonal Dust Storm Pattern

Mars Atmospheric Temperature and Dust Storm Tracking

Seasonal Temperature Pattern Indicating Martian Dust Storms
This graphic presents Martian atmospheric temperature data as curtains over an image of Mars taken during a regional dust storm. The temperature profiles extend from the surface to about 50 miles up. Temperatures are color coded, from minus 243 degrees Fahrenheit (purple) to minus 9 F (red).
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Fast Facts:
› A pattern of three large regional dust storms occurs with similar timing most Martian years.
› The seasonal pattern was detected from dust storms' effects on atmospheric temperatures, monitored by NASA orbiters since 1997.
› Improving the ability to predict large-scale, potentially hazardous dust storms on Mars would have safety benefits for planning robotic and human missions.
After decades of research to discern seasonal patterns in Martian dust storms from images showing the dust, but the clearest pattern appears to be captured by measuring the temperature of the Red Planet's atmosphere.
For six recent Martian years, temperature records from NASA Mars orbiters reveal a pattern of three types of large regional dust storms occurring in sequence at about the same times each year during the southern hemisphere spring and summer. Each Martian year lasts about two Earth years.
"When we look at the temperature structure instead of the visible dust, we finally see some regularity in the large dust storms," said David Kass of NASA's Jet Propulsion Laboratory, Pasadena, California. He is the instrument scientist for the Mars Climate Sounder on NASA'sMars Reconnaissance Orbiter and lead author of a report about these findings posted this week by the journal Geophysical Research Letters.
"Recognizing a pattern in the occurrence of regional dust storms is a step toward understanding the fundamental atmospheric properties controlling them," he said. "We still have much to learn, but this gives us a valuable opening."
Dust lofted by Martian winds links directly to atmospheric temperature: The dust absorbs sunlight, so the sun heats dusty air more than clear air. In some cases, this can be dramatic, with a difference of more than 63 Fahrenheit degrees (35 Celsius degrees) between dusty air and clear air. This heating also affects the global wind distribution, which can produce downward motion that warms the air outside the dust-heated regions. Thus, temperature observations capture both direct and indirect effects of the dust storms on the atmosphere.
Improving the ability to predict large-scale, potentially hazardous dust storms on Mars would have safety benefits for planning robotic and human missions to the planet's surface. Also, by recognizing patterns and categories of dust storms, researchers make progress toward understanding how seasonal local events affect global weather in a typical Mars year.
NASA has been operating orbiters at Mars continuously since 1997. The Mars Climate Sounder on Mars Reconnaissance Orbiter, which reached Mars in 2006, and the Thermal Emission Spectrometer on Mars Global Surveyor, which studied Mars from 1997 to 2006, have used infrared observations to assess atmospheric temperature. Kass and co-authors analyzed temperature data representative of a broad layer centered about 16 miles (25 kilometers) above the Martian surface. That's high enough to be more affected by regional storms than by local storms.
Most Martian dust storms are localized, smaller than about 1,200 miles (about 2,000 kilometers) across and dissipating within a few days. Some become regional, affecting up to a third of the planet and persisting up to three weeks. A few encircle Mars, covering the southern hemisphere but not the whole planet. Twice since 1997, global dust storms have fully enshrouded Mars. The behavior of large regional dust storms in Martian years that include global dust storms is currently unclear, and years with a global storm were not included in the new analysis.
Three large regional storms, dubbed types A, B and C, all appeared in each of the six Martian years investigated.
Multiple small storms form sequentially near Mars' north pole in the northern autumn, similar to Earth's cold-season arctic storms that swing one after another across North America.
"On Mars, some of these break off and head farther south along favored tracks," Kass said. "If they cross into the southern hemisphere, where it is mid-spring, they get warmer and can explode into the much larger Type A dust storms."
Southern hemisphere spring and summer on modern-day Mars are much warmer than northern spring and summer, because the eccentricity of Mars' orbit puts the planet closest to the sun near the end of southern spring. Southern spring and summer have long been recognized as the dustiest part of the Martian year and the season of global dust storms, even though the more detailed pattern documented in the new report had not been previously described.
When a Type A storm from the north moves into southern-hemisphere spring, the sunlight on the dust warms the atmosphere. That energy boosts the speed of winds. The stronger winds lift more dust, further expanding the area and vertical reach of the storm.
In contrast, the Type B storm starts close to the south pole shortly before the beginning of southern summer. Its origin may be from winds generated at the edge of the retreating south-polar carbon dioxide ice cap. Multiple storms may contribute to a regional haze.
The Type C storm starts after the B storm ends. It originates in the north during northern winter (southern summer) and moves to the southern hemisphere like the Type A storm. From one year to another, the C storm varies more in strength, in terms of peak temperature and duration, than the A and B storms do.
The longevity of NASA's Mars Reconnaissance Orbiter has helped enable studies such as this of seasonal patterns on Mars. JPL provided the Mars Climate Sounder instrument and manages the mission for NASA's Science Mission Directorate. Arizona State University, Tempe, provided the Thermal Emission Spectrometer for Mars Global Surveyor. Lockheed Martin Space Systems, Denver, built both orbiters.