sábado, 25 de março de 2017

NASA WEB · NASA's Juno spacecraft will make its fifth flyby over Jupiter's mysterious

NASA's Juno spacecraft will make its fifth flyby over Jupiter's mysterious cloud tops on Monday, March 27, at 1:52 a.m. PDT (4:52 a.m. EDT, 8:52 UTC).
At the time of closest approach (called perijove), Juno will be about 2,700 miles (4,400 kilometers) above the planet's cloud tops, traveling at a speed of about 129,000 miles per hour (57.8 kilometers per second) relative to the gas-giant planet. All of Juno's eight science instruments will be on and collecting data during the flyby.
"This will be our fourth science pass -- the fifth close flyby of Jupiter of the mission -- and we are excited to see what new discoveries Juno will reveal," said Scott Bolton, principal investigator of Juno from the Southwest Research Institute in San Antonio. "Every time we get near Jupiter's cloud tops, we learn new insights that help us understand this amazing giant planet."
The Juno science team continues to analyze returns from previous flybys. Scientists have discovered that Jupiter's magnetic fields are more complicated than originally thought, and that the belts and zones that give the planet's cloud tops their distinctive look extend deep into the its interior. Observations of the energetic particles that create the incandescent auroras suggest a complicated current system involving charged material lofted from volcanoes on Jupiter's moon Io.
Peer-reviewed papers with more in-depth science results from Juno's first flybys are expected to be published within the next few months.
Juno launched on Aug. 5, 2011, from Cape Canaveral, Florida, and arrived in orbit around Jupiter on July 4, 2016. During its mission of exploration, Juno soars low over the planet's cloud tops -- as close as about 2,600 miles (4,100 kilometers). During these flybys, Juno is probing beneath the obscuring cloud cover of Jupiter and studying its auroras to learn more about the planet's origins, structure, atmosphere and magnetosphere.
NASA's Jet Propulsion Laboratory, Pasadena, California, manages the Juno mission for the principal investigator, Scott Bolton, of Southwest Research Institute in San Antonio. The Juno mission is part of the New Frontiers Program managed by NASA's Marshall Space Flight Center in Huntsville, Alabama, for the Science Mission Directorate. Lockheed Martin Space Systems, Denver, built the spacecraft. JPL is a division of Caltech in Pasadena, California.

sexta-feira, 24 de março de 2017

NASA WEB · Andromeda's Bright X-Ray Mystery Solved by NuSTAR

NASA's Nuclear Spectroscope Telescope Array, or NuSTAR, has identified a candidate pulsar in Andromeda -- the nearest large galaxy to the Milky Way. This likely pulsar is brighter at high energies than the Andromeda galaxy's entire black hole population. Image credit: NASA/JPL-Caltech/GSFC/JHU 
› Full image and caption
The Milky Way's close neighbor, Andromeda, features a dominant source of high-energy X-ray emission, but its identity was mysterious until now. As reported in a new study, NASA's NuSTAR (Nuclear Spectroscopic Telescope Array) mission has pinpointed an object responsible for this high-energy radiation.
The object, called Swift J0042.6+4112, is a possible pulsar, the dense remnant of a dead star that is highly magnetized and spinning, researchers say. This interpretation is based on its emission in high-energy X-rays, which NuSTAR is uniquely capable of measuring. The object's spectrum is very similar to known pulsars in the Milky Way.
It is likely in a binary system, in which material from a stellar companion gets pulled onto the pulsar, spewing high-energy radiation as the material heats up.
"We didn't know what it was until we looked at it with NuSTAR," said Mihoko Yukita, lead author of a study about the object, based at Johns Hopkins University in Baltimore. The study is published in The Astrophysical Journal.
This candidate pulsar is shown as a blue dot in a NuSTAR X-ray image of Andromeda (also called M31), where the color blue is chosen to represent the highest-energy X-rays. It appears brighter in high-energy X-rays than anything else in the galaxy.
The study brings together many different observations of the object from various spacecraft. In 2013, NASA's Swift satellite reported it as a high-energy source, but its classification was unknown, as there are many objects emitting low energy X-rays in the region. The lower-energy X-ray emission from the object turns out to be a source first identified in the 1970s by NASA's Einstein Observatory. Other spacecraft, such as NASA's Chandra X-ray Observatory and ESA's XMM-Newton had also detected it. However, it wasn't until the new study by NuSTAR, aided by supporting Swift satellite data, that researchers realized it was the same object as this likely pulsar that dominates the high energy X-ray light of Andromeda.
Traditionally, astronomers have thought that actively feeding black holes, which are more massive than pulsars, usually dominate the high-energy X-ray light in galaxies. As gas spirals closer and closer to the black hole in a structure called an accretion disk, this material gets heated to extremely high temperatures and gives off high-energy radiation. This pulsar, which has a lower mass than any of Andromeda's black holes, is brighter at high energies than the galaxy's entire black hole population.
Even the supermassive black hole in the center of Andromeda does not have significant high-energy X-ray emission associated with it. It is unexpected that a single pulsar would instead be dominating the galaxy in high-energy X-ray light.
"NuSTAR has made us realize the general importance of pulsar systems as X-ray-emitting components of galaxies, and the possibility that the high energy X-ray light of Andromeda is dominated by a single pulsar system only adds to this emerging picture," said Ann Hornschemeier, co-author of the study and based at NASA's Goddard Space Flight Center, Greenbelt, Maryland.
Andromeda is a spiral galaxy slightly larger than the Milky Way. It resides 2.5 million light-years from our own galaxy, which is considered very close, given the broader scale of the universe. Stargazers can see Andromeda without a telescope on dark, clear nights.
"Since we can't get outside our galaxy and study it in an unbiased way, Andromeda is the closest thing we have to looking in a mirror," Hornschemeier said.
NuSTAR is a Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp., Dulles, Virginia. NuSTAR's mission operations center is at UC Berkeley, and the official data archive is at NASA's High Energy Astrophysics Science Archive Research Center. ASI provides the mission's ground station and a mirror archive. JPL is managed by Caltech for NASA.

domingo, 12 de março de 2017

NASA WEB · NASA Studying Shared Venus Science Objectives with Russian Space Research Institute

NASA JPL latest news release
NASA Studying Shared Venus Science Objectives with Russian Space Research InstituteA team of NASA-sponsored scientists will meet with the Russian Academy of Sciences' Space Research Institute (IKI) next week to continue work on a Joint Science Definition Team study focused on identifying shared science objectives for Venus exploration. The visit comes after a report was recently delivered to both NASA Headquarters in Washington and IKI in Moscow, assessing and refining the science objectives of the IKI Venera-D (Venera-Dolgozhivuschaya) Mission to Venus, Earth's closest planetary neighbor.
"While Venus is known as our 'sister planet,' we have much to learn, including whether it may have once had oceans and harbored life," said Jim Green, director of the Planetary Science Division at NASA Headquarters in Washington. "By understanding the processes at work at Venus and Mars, we will have a more complete picture about how terrestrial planets evolve over time and obtain insight into the Earth's past, present and future."
Venus has intrigued scientists for decades. Similar to Earth in composition and size, it spins slowly in the opposite direction. The rocky world's thick atmosphere traps heat in a runaway greenhouse effect, making it the warmest planet in our solar system with surface temperatures hot enough to melt lead. Glimpses below the clouds reveal volcanoes and an intricate landscape. Venus is named for the Roman goddess of love and beauty, the counterpart to the Greek goddess Aphrodite.
"On a solar-system scale, Earth and Venus are very close together and of similar size and makeup," said David Senske, co-chair of the U.S. Venera-D science definition team, and a scientist at NASA's Jet Propulsion Laboratory in Pasadena, California. "Among the goals that we would like to see if we can accomplish with such a potential partnership is to understand how Venus' climate operates so as to understand the mechanism that has given rise to the rampant greenhouse effect we see today."
The IKI Venera-D mission concept as it stands today would include a Venus orbiter that would operate for up to three years, and a lander designed to survive the incredibly harsh conditions a spacecraft would encounter on Venus' surface for a few hours. The science definition team is also assessing the potential of flying a solar-powered airship in Venus' upper atmosphere. The independent flying vehicle could be released from the Venera-D lander, enter the atmosphere, and independently explore Venus' atmosphere for up to three months.
NASA first visited Venus when the JPL-managed Mariner 2 collected data during a flyby in December 1962. NASA's last dedicated mission to explore Venus was Magellan. Launched in 1990, and managed by JPL, Magellan used radar to map 98 percent of the planet at a resolution of 330 feet (100 meters) or better during its four-year mission.
The Venera spacecraft program is the only one to date to successfully land on Venus and survive its harsh environment. Said Adriana Ocampo, who leads the Joint Science Definition Team at NASA Headquarters in Washington, "This potential collaboration makes for an enriching partnership to maximize the science results from Venera-D, and continue the exploration of this key planet in our solar system."

sexta-feira, 10 de março de 2017

NASA WEB · NASA Mars Orbiter Tracks Back- to-Back Regional Storms

Back-to-Back Martian Dust Storms
Active Lifting During Martian Dust Storm

This false-color scene from the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity documents movement of dust as a regional dust storm approached the rover's location on Feb. 24, 2017, during the 4,653rd Martian day, or sol, of the rover's work on Mars. Image credit: NASA/JPL-Caltech/Cornell/ASU
› Full image and caption
A regional dust storm currently swelling on Mars follows unusually closely on one that blossomed less than two weeks earlier and is now dissipating, as seen in daily global weather monitoring by NASA's Mars Reconnaissance Orbiter.
Images from the orbiter's wide-angle Mars Color Imager (MARCI) show each storm growing in the Acidalia area of northern Mars, then blowing southward and exploding to sizes bigger than the United States after reaching the southern hemisphere.
That development path is a common pattern for generating regional dust storms during spring and summer in Mars' southern hemisphere, where it is now mid-summer.
"What's unusual is we're seeing a second one so soon after the first one," said Mars meteorologist Bruce Cantor of Malin Space Science Systems, San Diego, which built and operates MARCI. "We've had orbiters watching weather patterns on Mars continuously for nearly two decades now, and many patterns are getting predictable, but just when we think we have Mars figured out, it throws us another surprise."
Weekly Martian weather reports including animated sequences of MARCI observations are available at:
Weather updates from the Mars Reconnaissance Orbiter science team provide operators of Mars rovers advance notice both for taking precautions and for planning observations of storms, particularly in case a regional storm grows to encircle the whole planet. A planet-encircling Martian storm last occurred in 2007.
The orbiter monitors storms with its Mars Climate Sounder (MCS) instrument as well as with MARCI. MCS measurements of high-altitude atmospheric warming associated with dust storms have revealed an annual pattern in the occurrence of large regional storms, and the first of these back-to-back storms fits into the identified pattern for this time of the Martian year.
Researchers have watched effects of the latest storms closely. "We hope for a chance to learn more about how dust storms become global, if that were to happen," said David Kass of NASA's Jet Propulsion Laboratory, Pasadena, California. "Even if it does not become a global storm, the temperature effects due to thin dust hazes will last for several weeks."
Cantor reported the second of the current back-to-back regional storms on March 5 to the team operating NASA's Mars Exploration Rover Opportunity. The earlier storm, which had become regional in late February, was dissipating by then but still causing high-altitude haziness and warming.
"There's still a chance the second one could become a planet-encircling storm, but it's unlikely because we're getting so late in the season," Cantor said this week. All previously observed planet-encircling dust storms on Mars occurred earlier in the southern summer.
Opportunity Project Manager John Callas, at JPL, credits MARCI weather reports with helping his team protect rovers when sudden increases in atmospheric dust decrease sunlight reaching the rover solar arrays. For example, Cantor's warning about a regional storm approaching the rover Spirit in November 2008 prompted JPL to send an emergency weekend command to conserve energy by deleting a planned radio transmission by Spirit. That saved enough charge in Spirit's batteries to prevent "what would likely have been a very serious situation," Callas said.
During the most recent global dust storm on Mars, in 2007, both of the rovers then operating on the planet -- Spirit and Opportunity -- were put into a power-saving mode for more than a week with minimal communication. The early-2010 ending of Spirit's mission was not related to a dust storm.
The same winds that raise Martian dust into the atmosphere can clear some of the dust that accumulates on the rovers. On Feb. 25, as the first back-to-back was spreading regionally, Opportunity experienced a significant cleaning of its solar panels that increased their energy output by more than 10 percent, adjusted for the clarity of the atmosphere. Dust-removing events typically clean the panels by only one or two percent. The Opportunity operations team has noticed over the years that a large dust-cleaning event often precedes dusty skies. Since Feb. 25, the atmosphere over Opportunity has become dustier, and some of the dust has already fallen back onto the solar panels.
"Before the first regional dust storm, the solar panels were cleaner than they were during the last four Martian summers, so the panels generated more energy," said JPL rover-power engineer Jennifer Herman. "It remains to be seen whether the outcome of these storms will be a cleaner or dirtier Opportunity. We have seen both results from dust storms in the past."
NASA's Curiosity rover, on Mars since 2012, uses a radioisotope thermoelectric generator for power instead of solar panels, so it doesn't face the same hazard from dust storms as Opportunity does. The possibility of observing the growth and life cycle of a regional or global storm offers a research opportunity for both missions, though. Scientists temporarily modified Curiosity's weather-monitoring regime last week in response to learning that a regional dust storm was growing.
"We'll keep studying this for weeks as the dust clears from the sky," said atmospheric scientist Mark Lemmon of Texas A&M University, College Station. Sky observations at multiple lighting angles can provide information about changes in the size distribution of suspended dust particles as additional dust is lifted into the sky and larger particles drop more quickly than smaller ones.

terça-feira, 28 de fevereiro de 2017

NASA WEB-Mid-infrared Of Saturn's Rings Shows Bright Cassini Division

Mid-infrared Of Saturn's Rings Shows Bright Cassini Division

Saturn View in The Mid-infrared
A team of researchers has succeeded in measuring the brightnesses and temperatures of Saturn's rings using the mid-infrared images taken by the Subaru Telescope in 2008.
The images are the highest resolution ground-based views ever made. They reveal that, at that time, the Cassini Division and the C ring were brighter than the other rings in the mid-infrared light and that the brightness contrast appeared to be the inverse of that seen in the visible light (Figure 1). The data give important insights into the nature of Saturn's rings.
The beautiful appearance of Saturn and its rings has always fascinated people. The rings consist of countless numbers of ice particles orbiting above Saturn's equator. However, their detailed origin and nature remain unknown. Spacecraft- and ground-based telescopes have tackled that mystery with many observations at various wavelengths and methods. The international Cassini mission led by NASA has been observing Saturn and its rings for more than 10 years, and has released a huge number of beautiful images.
Subaru Views Saturn
The Subaru Telescope also has observed Saturn several times over the years. Dr. Hideaki Fujiwara, Subaru Public Information Officer/Scientist, analyzed data taken in January 2008 using the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on the telescope to produce a beautiful image of Saturn for public information purposes. During the analysis, he noticed that the appearance of Saturn's rings in the mid-infrared part of the spectrum was totally different from what is seen in the visible light
Saturn's main rings consist of the C, B, and A rings, each with different populations of particles. The Cassini Division separates the B and A rings. The 2008 image shows that the Cassini Division and the C ring are brighter in the mid-infrared wavelengths than the B and A rings appear to be (Figure 1). This brightness contrast is the inverse of how they appear in the visible light, where the B and A rings are always brighter than the Cassini Division and the C ring (Figure 2).
"Thermal emission" from ring particles is observed in the mid-infrared, where warmer particles are brighter. The team measured the temperatures of the rings from the images, which revealed that the Cassini Division and the C ring are warmer than the B and A rings. The team concluded that this was because the particles in the Cassini Division and C ring are more easily heated by solar light due to their sparser populations and darker surfaces.
On the other hand, in the visible light, observers see sunlight being reflected by the ring particles. Therefore, the B and A rings, with their dense populations of particles, always seem bright in the visible wavelengths, while the Cassini Division and the C ring appear faint. The difference in the emission process explains the inverse brightnesses of Saturn's rings between the mid-infrared and the visible-light views.
Changing Angles Change the Brightnesses
It turns out that the Cassini Division and the C ring are not always brighter than the B and A rings, even in the mid-infrared. The team investigated images of Saturn's rings taken in April 2005 with COMICS, and found that the Cassini Division and the C ring were fainter than the B and A rings at that time, which is the same contrast to what was seen in the visible light (Figure 3).
The team concluded that the "inversion" of the brightness of Saturn's rings between 2005 and 2008 was caused by the seasonal change in the ring opening angle to the Sun and Earth. Since the rotation axis of Saturn inclines compared to its orbital plane around the Sun, the ring opening angle to the Sun changes over a 15-year cycle. This makes a seasonal variation in the solar heating of the ring particles. The change in the opening angle viewed from the Earth affects the apparent filling factor of the particles in the rings. These two variations - the temperature and the observed filling factor of the particles - led to the change in the mid-infrared appearance of Saturn's rings.
The data taken with the Subaru Telescope revealed that the Cassini Division and the C ring are sometimes bright in the mid-infrared though they are always faint in visible light. "I am so happy that the public information activities of the Subaru Telescope, of which I am in charge, led to this scientific finding," said Dr. Fujiwara. "We are going to observe Saturn again in May 2017 and hope to investigate the nature of Saturn's rings further by taking advantages of observations with space missions and ground-based telescopes."