NASA’s Chandra Observatory Searches for Trigger of Nearby Supernova

NASA - Chandra X-ray Observatory logo.

August 14, 2014

New data from NASA’s Chandra X-ray Observatory offer a glimpse into the environment of a star before it exploded earlier this year, and insight into what triggered one of the closest supernovas witnessed in decades.

The data gathered on the Jan. 21 explosion, a Type Ia supernova, allowed scientists to rule out one possible cause. These supernovas may be triggered when a white dwarf takes on too much mass from its companion star, immersing it in a cloud of gas that produces a significant source of X-rays after the explosion.

Image above: Supernova SN 2014J Explodes (unlabeled). Image Credit: NASA/CXC/SAO/R.Margutti et al.

Astronomers used NASA's Swift and Chandra telescopes to search the nearby Messier 82 galaxy, the location of the explosion, for such an X-ray source. However, no source was found, revealing the region around the site of the supernova is relatively devoid of material.

“While it may sound a bit odd, we actually learned a great deal about this supernova by detecting absolutely nothing,” said Raffaella Margutti of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts, who led the study. “Now we can essentially rule out that the explosion was caused by a white dwarf continuously pulling material from a companion star.”

This supernova, SN 2014J, could instead have been caused by the merger of two white dwarf stars, an event that should result in little or no X-rays after the explosion. Further observations could rule out or confirm other possible triggers.

 What Triggered This Supernova Explosion? Video Credits: NASA/CXC/A. Hobart.

“Being able to eliminate one of the main possible explanations for what caused SN 2014J to explode is a big step,” said CfA’s Atish Kamble, a co-author of the study. “The next step is to narrow things down even further.”

Type Ia supernovas are used as cosmic distance-markers, and have played a key role in the discovery of the universe’s accelerated expansion. At about 12 million light-years from Earth, SN 2014J and its host galaxy are close -- from a cosmic perspective. This offers scientists a chance to observe details that would be too hard to detect in more distant supernovas.

Image above: NASA’s Chandra X-ray Observatory is helping determine what caused SN 2014J, one of the closest supernovas discovered in decades. By comparing X-ray data taken before and after the stellar explosion, scientists can learn more about what set it off. Image Credit: NASA/SAO/CXC/R. Margutti et al.

“It’s crucial that we understand exactly how these stars explode because so much is riding on our observations of them for cosmology,” said co-author Jerod Parrent also from CfA. “SN 2014J might be a chance of a lifetime to study one of these supernovas in detail as it happens.”

The study of SN 2014J is similar to a study led by Margutti about another supernova, SN 2011fe, in the nearby galaxy M101.

This study was conducted by CfA’s Supernova Forensics Team, led by Alicia Soderberg. The results were published online and in the July 20 print issue of The Astrophysical Journal.

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.

For an additional interactive image, podcast, and video on the findings, visit: http://chandra.si.edu

For a preprint of the study results in The Astrophysical Journal, visit: http://arxiv.org/abs/1405.1488

For Chandra images, multimedia and related materials, visit: http://www.nasa.gov/chandra

Images (mentioned), Video (mentioned), Text, Credits: NASA / Felicia Chou / Chandra X-ray Center / Megan Watzke.

Best regards, Orbiter.ch

Stardust Team Reports Discovery of First Potential Interstellar Space Particles

NASA - Stardust Next Mission patch.

August 14, 2014

Seven rare, microscopic interstellar dust particles that date to the beginnings of the solar system are among the samples collected by scientists who have been studying the payload from NASA's Stardust spacecraft since its return to Earth in 2006. If confirmed, these particles would be the first samples of contemporary interstellar dust.

A team of scientists has been combing through the spacecraft's aerogel and aluminum foil dust collectors since Stardust returned in 2006.The seven particles probably came from outside our solar system, perhaps created in a supernova explosion millions of years ago and altered by exposure to the extreme space environment.

The research report appears in the Aug. 15 issue of the journal Science. Twelve other papers about the particles will appear next week in the journal Meteoritics & Planetary Science.

Image above: The largest interstellar dust track found in the Stardust aerogel collectors was this 35 micron-long hole produced by a 3 picogram mote that was probably traveling so fast that it vaporized upon impact. The other two likely interstellar dust grains were traveling more slowly and remained intact after a soft landing in the aerogel. Image Credit: Andrew Westphal, UC Berkeley.

"These are the most challenging objects we will ever have in the lab for study, and it is a triumph that we have made as much progress in their analysis as we have," said Michael Zolensky, curator of the Stardust laboratory at NASA’s Johnson Space Center in Houston and coauthor of the Science paper.

Stardust was launched in 1999 and returned to Earth on Jan. 15, 2006, at the Utah Test and Training Range, 80 miles west of Salt Lake City. The Stardust Sample Return Canister was transported to a curatorial facility at Johnson where the Stardust collectors remain preserved and protected for scientific study.

Inside the canister, a tennis racket-like sample collector tray captured the particles in silica aerogel as the spacecraft flew within 149 miles of a comet in January 2004. An opposite side of the tray holds interstellar dust particles captured by the spacecraft during its seven-year, three-billion-mile journey.

Scientists caution that additional tests must be done before they can say definitively that these are pieces of debris from interstellar space. But if they are, the particles could help explain the origin and evolution of interstellar dust.

The particles are much more diverse in terms of chemical composition and structure than scientists expected. The smaller particles differ greatly from the larger ones and appear to have varying histories. Many of the larger particles have been described as having a fluffy structure, similar to a snowflake.

Two particles, each only about two microns (thousandths of a millimeter) in diameter, were isolated after their tracks were discovered by a group of citizen scientists. These volunteers, who call themselves "Dusters," scanned more than a million images as part of a University of California, Berkeley, citizen-science project, which proved critical to finding these needles in a haystack.

Image above: The largest interstellar dust track found in the Stardust aerogel collectors was this 35 micron-long hole produced by a 3 picogram speck of dust that was probably traveling so fast that it vaporized upon impact. The other two likely interstellar dust grains were traveling more slowly and remained in. Image Credit: UC Berkeley/Andrew Westphal.

A third track, following the direction of the wind during flight, was left by a particle that apparently was moving so fast -- more than 10 miles per second (15 kilometers per second) -- that it vaporized. Volunteers identified tracks left by another 29 particles that were determined to have been kicked out of the spacecraft into the collectors.

Four of the particles reported in Science were found in aluminum foils between tiles on the collector tray. Although the foils were not originally planned as dust collection surfaces, an international team led by physicist Rhonda Stroud of the Naval Research Laboratory searched the foils and identified four pits lined with material composed of elements that fit the profile of interstellar dust particles.

Three of these four particles, just a few tenths of a micron across, contained sulfur compounds, which some astronomers have argued do not occur in interstellar dust. A preliminary examination team plans to continue analysis of the remaining 95 percent of the foils to possibly find enough particles to understand the variety and origins of interstellar dust.

Supernovas, red giants and other evolved stars produce interstellar dust and generate heavy elements like carbon, nitrogen and oxygen necessary for life. Two particles, dubbed Orion and Hylabrook, will undergo further tests to determine their oxygen isotope quantities, which could provide even stronger evidence for their extrasolar origin.

Stardust Next spacecraft. Image Credit: NASA / JPL-Caltech

Scientists at Johnson have scanned half the panels at various depths and turned these scans into movies, which were then posted online, where the Dusters could access the footage to search for particle tracks.

Once several Dusters tag a likely track, Andrew Westphal, lead author of the Science article, and his team verify the identifications. In the one million frames scanned so far, each a half-millimeter square, Dusters have found 69 tracks, while Westphal has found two. Thirty-one of these were extracted along with surrounding aerogel by scientists at Johnson and shipped to UC Berkeley to be analyzed.

NASA's Jet Propulsion Laboratory, Pasadena, California, manages the Stardust mission for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, developed and operated the spacecraft.

For information about the Stardust mission on the Web, visit: http://www.nasa.gov/stardust

For information about NASA and agency programs on the Web, visit: http://www.nasa.gov/home

Images (mentioned), Text, Credits: NASA / J.D. Harrington / Johnson Space Center / William Jeffs.

Cheers, Orbiter.ch

NASA to Investigate Climate Impacts of Arctic Sea Ice Loss

 NASA - Wallops Flight Facility Center patch / NASA - ARISE Mission patch.

August 14, 2014

ARISE Arctic Mission Takes Shape

Video above:  Crews at NASA Goddard’s Wallops Flight Facility are hard at work integrating a suite of instruments into a C-130 aircraft in preparation for the start of the ARISE campaign later this month. ARISE, which stands for Arctic Radiation IceBridge Sea and Ice Experiment, will make simultaneous measurements of ice, clouds and levels of incoming and outgoing radiation, the balance of which determines the degree of climate warming. Video credit: NASA Goddard Space Flight Center.

A new NASA field campaign will begin flights over the Arctic this summer to study the effect of sea ice retreat on Arctic climate. The Arctic Radiation IceBridge Sea and Ice Experiment (ARISE) will conduct research flights Aug. 28 through Oct. 1, covering the peak of summer sea ice melt.

ARISE is NASA's first Arctic airborne campaign designed to take simultaneous measurements of ice, clouds and the levels of incoming and outgoing radiation, the balance of which determines the degree of climate warming. The campaign team will fly aboard NASA’s C-130 aircraft from Thule Air Base in northern Greenland the first week and from Eielson Air Force Base near Fairbanks, Alaska, through the remainder of the campaign.

In recent years the Arctic has experienced increased summer sea ice loss. Scientists expect the exposure of more open water to sunlight could enhance warming in the region and cause the release of more moisture to the atmosphere. Additional moisture could affect cloud formation and the exchange of heat from Earth’s surface to space. Researchers are grappling with how these changes in the Arctic affect global climate.

"A wild card in what's happening in the Arctic is clouds and how changes in clouds, due to changing sea-ice conditions, enhance or offset warming," said Bill Smith, ARISE principal investigator at NASA's Langley Research Center in Hampton, Virginia.

ARISE was planned over the last year to take advantage of NASA’s existing capabilities for gathering data about ongoing changes in the Arctic. Satellites provided some information about clouds and the energy balance in the Arctic, but the multiple instruments flown during ARISE should provide further insight.

"The clouds and surface conditions over the Arctic as we observe them from satellites are very complex," Smith said. "We need more information to understand how to better interpret the satellite measurements, and an aircraft can help with that."

The array of instruments on ARISE should help scientists better observe how sea ice loss is affecting Arctic cloud formation and therefore the balance of incoming and outgoing radiation. Low-level clouds typically reflect more sunlight and offset warming, while higher clouds are typically less reflective and act to trap more heat in the atmosphere.

Image above: NASA’s C-130 aircraft will carry scientists over the Arctic starting this month from northern Greenland and Fairbanks, Alaska. Image Credit: NASA.

“It’s a complex business, but it depends on a lot of things we can, in fact, measure,” said Hal Maring, program manager for radiation sciences in the Earth Science Division at NASA Headquarters in Washington.

ARISE researchers will fly survey missions that target different cloud types and surface conditions, such as open water, land ice and sea ice. The missions will be timed to fly under the orbit paths of key satellite instruments, such as the Clouds and the Earth’s Radiant Energy Systems (CERES) instruments on multiple NASA satellites. Each morning, mission planners will look at satellite timings and weather forecasts to design flight plans that meet the most objectives of the campaign.

The NASA C-130, based at the Wallops Flight Facility in Virginia, will carry instruments that measure solar (incoming) and infrared (outgoing) radiation, ice surface elevation and cloud properties such as cloud particle size. This will be the first time that many of these instruments, including the mission's laser altimeter, have flown together.

The ARISE campaign is a joint effort of the Radiation Sciences, Cryospheric Sciences and Airborne Sciences programs of the Earth Science Division in NASA's Science Mission Directorate in Washington.

NASA monitors Earth's vital signs from land, air and space with a fleet of satellites and ambitious airborne and ground-based observation campaigns. NASA develops new ways to observe and study Earth's interconnected natural systems with long-term data records and computer analysis tools to better see how our planet is changing. The agency shares this unique knowledge with the global community and works with institutions in the United States and around the world that contribute to understanding and protecting our home planet.

To learn more about NASA's Earth science activities in 2014, visit: http://www.nasa.gov/earthrightnow

Image (mentioned), Video (mentioned), Text, Credits: NASA / Steve Cole.

Greetings, Orbiter.ch

Watching the Winds Where Sea Meets Sky

NASA logo.

August 14, 2014

Image above: The SeaWinds scatterometer on NASA's QuikScat satellite stares into the eye of 1999's Hurricane Floyd as it hits the U.S. coast. The arrows indicate wind direction, while the colors represent wind speed, with orange and yellow being the fastest. NASA/JPL-Caltech.

The ocean covers 71 percent of Earth's surface and affects weather over the entire globe. Hurricanes and storms that begin far out over the ocean affect people on land and interfere with shipping at sea. And the ocean stores carbon and heat, which are transported from the ocean to the air and back, allowing for photosynthesis and affecting Earth's climate. To understand all these processes, scientists need information about winds near the ocean's surface.

NASA's ISS-RapidScat, launching to the International Space Station this fall, will watch those winds with a tried and true instrument called a scatterometer. Since satellite scatterometers began collecting data in the 1970s, their soundings have become essential to our understanding of Earth's ocean winds.

NASA's ISS-RapidScat on the International Space Station

Scatterometers send microwave pulses to Earth's surface at an angle. A smooth ocean surface reflects most of the energy like a mirror, away from the satellite, but strong waves scatter some of the signal back toward the spacecraft. From the strength of this backscatter, scientists can estimate the speed and direction of wind at the ocean's surface.

"Before scatterometers, we could only measure ocean winds on ships, and sampling from ships is very limited," said Timothy Liu of NASA's Jet Propulsion Laboratory in Pasadena, California, who led the science team for NASA's QuikScat mission.

Scatterometry began to emerge during World War II, when scientists realized wind disturbing the ocean's surface caused noise in their radar signals. NASA included an experimental scatterometer in its first space station in 1973 and again when it launched its SeaSat satellite in 1978. During its three-month life, SeaSat's scatterometer provided scientists with more individual wind observations than ships had collected in the previous century.

A JPL team then designed a mission called NSCAT, the NASA Scatterometer. When the Japanese spacecraft carrying NSCAT failed in 1997, engineers rushed to complete JPL's SeaWinds scatterometer instrument, already in development. In just a year, JPL engineers finished the SeaWinds scatterometer, and Ball Aerospace & Technologies Corporation created a satellite from another project's leftover parts. NASA named the expedited mission "QuikScat."

"We had to build the SeaWinds instrument using spare parts and do it very fast," Liu said. "It was only meant to be a gap-filler. But then it lasted for 10 years."

From 1999 until 2009, QuikScat collected 400,000 measurements over 90 percent of Earth's surface daily. Researchers used the data to improve weather forecasts, monitor typhoons and hurricanes, design shipping routes and place ocean fisheries. Scientists also found that SeaWinds could measure snow cover, identify icebergs floating near Antarctica and track the shrinking of the Amazon rainforest.

The number of scatterometers in space grew drastically during QuikScat's decade. "It used to be, we were the only game in town. Now there's an international array of scatterometers up there," Liu said.

QuikScat provided its full range of data until its antenna stopped spinning in 2009, significantly reducing the amount of Earth's surface it measured. But the data it continues to collect are now used to calibrate measurements from other satellites.

"We tipped QuikScat slightly so it was at the same angle as the Indian scatterometer, OSCAT, and continued to do that throughout the whole OSCAT mission," said JPL's Phil Callahan, the data products manager for QuikScat. Cross-calibrating new instruments like OSCAT with existing ones ensures that the new data can be combined seamlessly with the old, allowing researchers to examine long-term trends.

When NASA's ISS-RapidScat mission begins collecting data this fall, it will add data to the same archive.

"OSCAT stopped working earlier this year, so RapidScat's presence is very important," said Howard Eisen, the RapidScat project manager at JPL. "We can transfer the calibration standard from QuikScat to RapidScat, which can then pass it on to future scatterometers, making a continuous, 15-plus year record."

As with QuikScat, JPL engineers built RapidScat in less than two years. The mission combines new industrial-grade hardware and older inherited hardware used to develop and test QuikScat, and was developed for just $26 million. QuikScat will calibrate the new mission as well.

Also as with QuikScat, RapidScat is meant to be a "gap-filler" on its two-year mission. Another scatterometer from the Indian Space Research Organization is scheduled to join RapidScat in orbit in the next two years. RapidScat will be the last scatterometer built from SeaWinds materials, but likely not the last in a growing record of Earth's winds over the ocean.

"Including RapidScat, we've gotten three scatterometers and more than 10 years of data from the SeaWinds project," Callahan said.

For more information about ISS-RapidScat, visit: http://winds.jpl.nasa.gov/missions/RapidScat/

ISS-RapidScat is one of five new NASA missions launching in 2014. NASA monitors Earth's vital signs from land, air and space with a fleet of satellites and ambitious airborne and ground-based observation campaigns. NASA develops new ways to observe and study Earth's interconnected natural systems with long-term data records and computer analysis tools to better see how our planet is changing. The agency shares this unique knowledge with the global community and works with institutions in the United States and around the world that contribute to understanding and protecting our home planet.

For more information about NASA's Earth science activities in 2014, visit: http://www.nasa.gov/earthrightnow

Images, Text, Credits: NASA / JPL / Alan Buis, written by Rosalie Murphy.

Best regards, Orbiter.ch

Launch of WorldView 3 on Atlas V 401 from Vandenberg

ULA - Atlas 5 flight 401 / WorldView 3 launch poster.


Aug 14, 2014

Launch of WorldView 3 on Atlas V 401 from Vandenberg

A commercial satellite, WorldView 3, was successfully launched today, August 13th 2014 at 18:30 UTC from Vandenberg Air Force Base in California on a Atlas V 401 rocket.

This was the 48th launch of an Atlas V rocket. WorldView 3 is an Earth imaging satellite with an ability to see an object as small as 31cm for the American company Digital Globe. This will be the most powerful commercial Earth imaging satellite in orbit.

Launch of WorldView 3 on Atlas V 401 from Vandenberg

WorldView-3 will enhance Digital Globe’s industry-leading constellation and will further support customers across a variety of industries, such as agriculture, mining, and oil and gas. For more information about the WorldView-3 satellite, visit http://worldview3.digitalglobe.com/.

WorldView-3 satellite

WorldView-3 will be the 10th of 15 planned missions ULA is slated to launch in 2014, and ULA's 86th since the company formed in 2006.

The United Launch Alliance Atlas V is provided by Lockheed Martin Commercial Launch Services.

For more information about United Launch Alliance (ULA). visit: http://www.ulalaunch.com

Images, Video, Text, Credits: ULA / Digital Globe.

Greetings, Orbiter.ch

Monitoring Meteor Showers from Space

ISS - International Space Station patch.

August 13, 2014

Those who enjoy the spectacle of the Perseids, Geminids or other annual meteor showers likely aren’t thinking about where these shooting stars originated or whether they might pose a danger. Scientists, however, think about such things and will use the vantage point of a special window on the International Space Station to learn more about the composition and behavior of meteors and their parent bodies. The Meteor investigation will help scientists better understand the asteroids and comets crossing Earth’s orbit and how these celestial objects have affected our planet. It also could help protect spacecraft and Earth from potential collisions with this celestial debris.

The investigation, which will launch to the station on Orbital Sciences' third commercial resupply flight, will spend two years recording meteor showers using a special camera installed in the station’s Window Observational Research Facility (WORF). The camera is programmed to record predictable showers, and its continuous measurement of meteor interactions with Earth’s atmosphere could spot unpredicted ones as well.

Image above: Mock-up camera mounted in the Window Observational Research Facility (WORF) simulator at Johnson Space Center. Image Credit: Southwest Research Institute.

Space-based viewing of meteor showers offers many advantages over traditional observation by ground- or aircraft-based instruments. Viewing from the station is not affected by weather or interference from Earth’s atmosphere. Instruments on Earth are also limited to short periods of observation time and viewing field, but the camera aboard the station will record for roughly 560 minutes every day. That is the amount of time the station is in darkness as it orbits Earth 16 times a day.

Partners in the Meteor investigation include the Center for the Advancement of Science in Space (CASIS), Southwest Research Institute (SwRI) in San Antonio and Japan’s Planetary Exploration Research Center (PERC) at Chiba Institute of Technology.

Once installed, the Meteor system will operate mostly on its own. Michael Fortenberry, principal investigator for Meteor and an engineer with SwRI, explains that the crew will only need to adjust the lens focus and change out hard drives that store high-resolution video collected by the camera. A software program will identify and separate video clips that likely include meteors, and those can be further analyzed later on the ground. Scientists can use these images to glean information such as the size of a particle of meteoric dust based on its flight path and light curve.

Image above: Location of the Window Observational Research Facility (WORF) in the Destiny Module. Image Credit: NASA.

Going beyond identifying meteors and monitoring their activity, the instrument has the additional capability to help classify their chemical composition. A device on the camera called a diffraction grating separates light passing through it into different wavelengths or colors, known as spectra, just as a prism does. The device will record spectra of light emitted for specific meteoroids, which investigators can use to determine the abundance of several elements in the meteoroids or meteor dust.

“From previous observation on the ground, we already know the parent body for these meteors,” explains Meteor co-investigator Tomoko Arai, Ph.D., a staff scientist at PERC. “The spectral information will tell us more about these parent bodies and help us understand their materials.”

The camera is scheduled to record all 12 known major showers. Secondary targets include minor meteor showers and periods with little or no identified regular activity. Observation of de-orbiting spacecraft and other targets also will be made. “There is a chance we could find new minor meteor showers, or observe meteors from an unexpected source like Comet Ison,” says Fortenberry.

Image above: A Perseid meteor streaks through the Earth's atmosphere, as seen and photographed by astronaut Ron Garan while aboard the International Space Station on August 13, 2011. Image Credit: NASA.

Meteors are created by the disintegration of comets or asteroids orbiting the sun. Those that enter Earth's atmosphere heat up and burn, causing the visible streak we see during a shower. Although the exact number of meteors entering the atmosphere varies during each event, some major showers can produce a peak of more than 100 visible meteors per hour.

Some meteor-producing bodies have the potential to create meteors so large that they do not burn up completely on their trip through Earth’s atmosphere and actually strike the surface. This investigation will collect much more data than was previously possible about what already hits our planet. This data will be correlated with information from other sensors and analysis to determine how many meteors are entering the atmosphere and their characteristics. Those characteristics will help scientists better understand which parent bodies might create meteors that pose a threat to Earth, along with their physical and chemical makeup. In addition, data on orbital debris, both natural and man-made, can be used to time and position spacecraft to keep them safe from collisions in space.

The WORF provides a stable platform for hand-held photography and other research activities at the U.S. Laboratory Science Window, the highest optical-quality window ever installed on a human space vehicle. The Window enables the use of high-resolution cameras from inside the station rather than outside, where instruments are subject to the vacuum and extreme temperatures of space.

The Meteor investigation adds to other monitoring of meteors on orbit, such as through Crew Earth Observations (CEO). So the next time you enjoy a meteor shower, rest easy knowing that these scientists are keeping an eye on things.

Related links:

Center for the Advancement of Science in Space (CASIS): http://www.iss-casis.org/

Southwest Research Institute (SwRI): http://www.swri.org/

Japan Planetary Exploration Research Center (PERC): http://www.perc.it-chiba.ac.jp/en/about/mission-of-perc.html

Crew Earth Observations (CEO): http://www.nasa.gov/mission_pages/station/research/news/EyeLevel_Perseid.html

Geminids or other annual meteor showers: http://www.nasa.gov/topics/solarsystem/features/watchtheskies/#.U-uMsbGanpt

For more information about the International Space Station (ISS), visit: http://www.nasa.gov/mission_pages/station/main/index.html

Images (mentioned), Text, Credits: NASA Johnson Space Center / Melissa Gaskill.

Greetings, Orbiter.ch

Tall Boulder Rolls Down Martian Hill, Lands Upright

NASA - Mars Reconnaissance Orbiter (MRO) patch.

August 13, 2014

A track about one-third of a mile (500 meters) long on Mars shows where an irregularly shaped boulder careened downhill to its current upright position, seen in a July 3, 2014, image from the High Resolution Imaging Science Experiment (HiRISE) camera aboard NASA's Mars Reconnaissance Orbiter.

Image above: The track left by an oblong boulder as it tumbled down a slope on Mars runs from upper left to right center of this image. The boulder came to rest in an upright attitude at the downhill end of the track. The HiRISE camera on NASA's Mars Reconnaissance Orbiter recorded this view on July 14, 2014. Image Credit: NASA/JPL-Caltech/Univ. of Arizona.

The shadow cast by the rock in mid-afternoon sunlight reveals it is about 20 feet (6 meters) tall. In the downward-looking image, the boulder is only about 11.5 feet (3.5 meters) wide.  It happened to come to rest with its long dimension vertical.  The trail it left on the slope has a pattern that suggests the boulder couldn't roll smoothly or straight due to its shape.

Artist's view of NASA's Mars Reconnaissance Orbiter. Image Credit: NASA/JPL-Caltech

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate in Washington. HiRISE, one of six science instruments on the orbiter, is operated by the University of Arizona, Tucson. The instrument was built by Ball Aerospace & Technologies Corp., Boulder, Colorado.

For more information about the Mars Reconnaissance Orbiter, which has been studying Mars from orbit since 2006, visit: http://www.nasa.gov/mro

For more information about HiRISE, visit: http://www.uahirise.org/

Images (mentioned), Text, Credits: NASA / JPL / Guy Webster.

Best regards, Orbiter.ch