'The Spider' On Mercury: MESSENGER Spacecraft Streams Back Surprises

Daily Science Journal (Feb. 2, 2008) — The recent flyby of Mercury by NASA's MESSENGER spacecraft has given scientists an entirely new look at a planet once thought to have characteristics similar to those of Earth's moon. Researchers are amazed by the wealth of images and data that show a unique world with a diversity of geological processes and a very different magnetosphere from the one discovered and sampled more than 30 years ago.

The Spider: MESSENGER obtained high-resolution images of the floor of the Caloris basin on January 14, 2008. Near the center of the basin, this remarkable feature -- nicknamed "the spider" by the science team -- was revealed. A set of troughs radiating outward are interpreted to be the result of the breaking apart of the floor materials that filled the Caloris basin after its formation. Other troughs near the center form a polygonal pattern. An impact crater about 40 km (~25 miles) in diameter appears to be centered on "the spider." (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington)

After a journey of more than 2 billion miles and three and a half years, NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft made its first flyby on Jan. 14. MESSENGER is the first mission sent to orbit the planet closest to our sun. The spacecraft's cameras and other sophisticated, high-technology instruments collected more than 1,200 images and made other science observations. Data included the first up-close measurements of Mercury since the Mariner 10 spacecraft's third and final flyby on March 16, 1975.

"This flyby allowed us to see a part of the planet never before viewed by spacecraft, and our little craft has returned a gold mine of exciting data," said Sean Solomon, MESSENGER's principal investigator, Carnegie Institution of Washington. "From the perspectives of spacecraft performance and maneuver accuracy, this encounter was near-perfect, and we are delighted that all of the science data are now on the ground."

Unlike the moon, MESSENGER showed that Mercury has huge cliffs with structures snaking up hundreds of miles across the planet's face. These cliffs preserve a record of patterns of fault activity from early in the planet's history. The spacecraft also revealed impact craters that appear very different from lunar craters.

Instruments provided a topographic profile of craters and other geological features on the night side of Mercury. The spacecraft also discovered a unique feature that scientists dubbed "The Spider." This formation never has been seen on Mercury before and nothing like it has been observed on the moon. It lies in the middle of a large impact crater called the Caloris basin and consists of more than one hundred narrow, flat-floored troughs radiating from a complex central region.

"The Spider has a crater near its center, but whether that crater is related to the original formation or came later is not clear at this time," said James Head, science team co-investigator at Brown University, Providence, R.I.

Now that MESSENGER has shown scientists the full extent of the Caloris basin, its diameter has been revised upward from the Mariner 10 estimate of 800 miles to perhaps as large as 960 miles from rim to rim. The plains inside the Caloris basin are distinctive and more reflective than the exterior plains. Impact basins on the moon have opposite characteristics.

The magnetosphere and magnetic field of Mercury during the MESSENGER flyby appeared to be different from the Mariner 10 observations. MESSENGER found the planet's magnetic field was generally quiet but showed several signatures indicating significant pressure within the magnetosphere.

Magnetic fields like Earth's and their resulting magnetospheres are generated by electrical dynamos in the form of a liquid metallic outer core deep in the planet's center. Of the four terrestrial planets, only Mercury and Earth exhibit such a phenomenon. The magnetic field deflects the solar wind from the sun, producing a protective bubble around Earth that shields the surface of our planet from those energetic particles and other sources farther out in the galaxy. Similar variations are expected for Mercury's magnetic field, but the precise nature of its field and the time scales for internal changes are unknown. The next two flybys and the yearlong orbital phase will shed more light on these processes.

MESSENGER's suite of instruments also has provided insight into the mineral makeup of the surface terrain and detected ultraviolet emissions from sodium, calcium and hydrogen in Mercury's exosphere. The spacecraft explored the sodium-rich exospheric "tail," which extends more than 25,000 miles from the planet.

"We should keep this treasure trove of data in perspective. With two flybys to come and an intensive orbital mission to follow, we are just getting started to go where no one has been before," said project scientist Ralph McNutt of the Applied Physics Laboratory, Laurel, Md.

Adapted from materials provided by National Aeronautics and Space Administration.

Read the rest of this entry »

Could An Asteroid Hit Planet Earth, Again?

Daily Science Journal (Feb. 1, 2008) — Earth dodged a bullet today, when asteroid TU24 passed within 540,000 kilometers of our planet, which is just down the street on a galactic scale. Tomorrow, another asteroid – 2007 WD5 – will zip past Mars at a distance of only 26,000 kilometers away. Will we dodge the bullet the next time a near-Earth object (NEO) hurtles dangerously close to our home planet?

Asteroid impact on early Earth. Some scientists believe that impacts such as this during the Late Heavy Bombardment period, 4 billion years ago, may have delivered primitive life to Earth. (Credit: Copyright Don Davis)

To mark the 100th anniversary of the Tunguska event, when an exploding asteroid leveled 2000 square kilometers of Siberian forest, The Planetary Society today kicked off a year-long focus on Target Earth. The asteroid believed responsible for the cataclysm on June 30, 1908 became a fireball from the sky and knocked pine trees over like matchsticks near the Podkamennaya Tunguska River in Russia. Such an explosion today over more populated areas could lay waste an entire city.

“The solar system is a busy place,” said Louis Friedman, Executive Director of The Planetary Society. “In fact, we live in a dangerous neighborhood, and keeping track of NEOs is like organizing a Neighborhood Watch in our corner of space.”

Earth has been hit by NEOs many times in the past; ancient craters are still visible in landforms around the world. The famed Meteor Crater in Arizona and Canada’s Lake Manicouagan are only two examples.

Target Earth will focus on a variety of NEO projects supported by The Planetary Society, including the Apophis Mission Design Competition, the Gene Shoemaker Near Earth Object Grants, NEO mission advocacy, and a one-hour HD TV “Daily Planet” special on asteroids being produced by Discovery Canada.

In mid-to late February, the Society will announce the winners of the Apophis Mission Design Competition, which invited participants to compete for $50,000 in prizes by designing a mission to rendezvous with and "tag" a potentially dangerous near-Earth asteroid. The competition received 37 mission proposals from 19 countries on 6 continents.

Tagging may be necessary to track an asteroid accurately enough to determine whether it will impact Earth, thus helping space agencies to decide whether to mount a deflection mission to alter its orbit. Apophis is an approximately 400-meter NEO, which will come closer to Earth in 2029 than the orbit of our geostationary satellites – close enough to be visible to the naked eye. If Apophis passes through a several hundred-meter wide "keyhole" in 2029, it will impact Earth in 2036. While current estimates rate the probability of impact as very low, Apophis is being used as an example to enable design of a broader type of mission to any potentially dangerous asteroid.

"Target Earth encompasses The Planetary Society’s three-pronged approach to NEO research,” said Director of Projects Bruce Betts. "We fund researchers who discover and track asteroids, advocate greater NEO research funding by the government, and help spur the development of possible ways to avert disaster should a potentially dangerous asteroid be discovered."

The Society will call for another round of Shoemaker grant proposals in the summer of 2008. One past grant recipient, Roy Tucker from Arizona, co-discovered Apophis. Many other past recipients from around the world continue to discover, track, and characterize NEOs.

NASA currently has no plans to study methods of asteroid deflection, or how to tag an asteroid for precise tracking. NASA and the European Space Agency (ESA) have co-sponsored the Society’s Apophis competition and will study the best mission designs offered.

The $50,000 in prize money for the Apophis Mission Design competition was contributed by The Planetary Society's Chairman of the Board, Dan Geraci, together with donations from Planetary Society members around the world. Funding for the Gene Shoemaker NEO Grant program comes from Planetary Society members.

Adapted from materials provided by Planetary Society.

Read the rest of this entry »

Traces Of The Martian Past In The Terby Crater, Europe's Eye On Mars: First Spectacular Results From Mars Express

Daily Science Journal (Jan. 31, 2008) — The High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express has returned striking scenes of the Terby crater on Mars. The region is of great scientific interest as it holds information on the role of water in the history of the planet.

This false-colour image of Terby crater on Mars was derived from three HRSC colour channels and the nadir channel of the High Resolution Stereo Camera (HRSC) on board ESA's Mars Express orbiter. (Credit: ESA/DLR/FU Berlin (G. Neukum))

The image data was obtained on 13 April 2007 during orbit 4199, with a ground resolution of approximately 13 m/pixel. The Sun illuminates the scene from the west (from above in the image).

Terby crater lies at approximately 27° south and 74° east, at the northern edge of the Hellas Planitia impact basin in the southern hemisphere of Mars.

The crater, named after the Belgian astronomer Francois J. Terby (1846 – 1911), has a diameter of approximately 170 km. The scene shows a section of a second impact crater in the north.

Eye-catching finger-shaped plateaux extend in the north-south direction. They rise up to 2000 m above the surrounding terrain. The relatively old crater was filled with sediments in the past, which formed plateaux on erosion.

The flanks of the plateaux clearly exhibit layering of different-coloured material. Differences in colour usually indicate changes in the composition of the material and such layering is called ‘bedding’. Bedding structures are typical of sedimentary rock, which has been deposited either by wind or water. Different rock layers erode differently, forming terraces.

The valleys exhibit gullies, or channels cut in the ground by running liquid, mainly in the northern part of the image. These gullies and the rock-bedding structure indicate that the region has been affected by water.

The sediments in this region are interesting to study because they contain information on the role of water in the history of the planet. This is one of the reasons why Terby crater was originally short listed as one of 33 possible landing sites for NASA’s Mars Science Laboratory mission, planned for launch in 2009.

The colour scenes have been derived from the three HRSC colour channels and the nadir channel. The perspective views have been calculated from the digital terrain model derived from the HRSC stereo channels. The 3D anaglyph image was calculated from the nadir channel and one stereo channel, stereoscopic glasses are required for viewing.

Adapted from materials provided by European Space Agency.

----------------------------------------------------------------------------

Add On Article :

Europe's Eye On Mars: First Spectacular Results From Mars Express

ESA's Mars Express, successfully inserted into orbit around Mars on 25 December 2003, is about to reach its final operating orbit above the poles of the Red Planet. The scientific investigation has just started and the first results already look very promising, as this first close-up image shows.

Picture taken by the High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express orbiter on 14 January 2004 under the responsibility of the Principal Investigator Prof. Gerhard Neukum. It was processed by the Institute for Planetary Research of the German Aerospace Centre (DLR), also involved in the development of the camera, and by the Institute of Geosciences of the Freie Universität Berlin.

Although the seven scientific instruments on board Mars Express are still undergoing a thorough calibration phase, they have already started collecting amazing results. The first high-resolution images and spectra of Mars have already been acquired.

This first spectacular stereoscopic colour picture was taken on 14 January 2004 by ESA's Mars Express satellite from 275 km above the surface of Mars by the High Resolution Stereo Camera (HRSC). This image is available on the ESA Portal at: http://mars.esa.int

The picture shows a portion of a 1700 km long and 65 km wide swath which was taken in south-north direction across the Grand Canyon of Mars (Valles Marineris). It is the first image of this size that shows the surface of Mars in high resolution (12 metres per pixel), in colour, and in 3D. The total area of the image on the Martian surface (top left corner) corresponds to 120 000 km². The lower part of the picture shows the same region in perspective view as if seen from a low-flying aircraft. This perspective view was generated on a computer from the original image data. One looks at a landscape which has been predominantly shaped by the erosional action of water. Millions of cubic kilometres of rock have been removed, and the surface features seen now such as mountain ranges, valleys, and mesas, have been formed.

The HRSC is just one of the instruments to have collected exciting data. To learn more about the very promising beginning to ESA's scientific exploration of Mars, media representatives are invited to attend a press conference on Friday, 23 January 2004, at 11:00 CET at ESA's Space Operations Centre in Darmstadt, Germany, and in video-conference with the other ESA centres.

There, under the auspices of ESA Council Chair, Germany's Minister for Education and Research, Mrs Edelgard Bulmahn, ESA's Director of the Scientific Programme, Prof. David Southwood and the Principal Investigators of all instruments on board Mars Express will present the first data and preliminary results.

Also a spectacular, three-dimensional video sequence, featuring famous landmarks on the surface of Mars 'as seen through European eyes' will be unveiled for the first time on Friday 23 January.

Adapted from materials provided by European Space Agency.

Read the rest of this entry »

Mercury's Magnetosphere Fends Off Solar Wind

Daily Science Journal (Jan. 31, 2008) — The planet Mercury's magnetic field appears to be strong enough to fend off the harsh solar wind from most of its surface, according to data gathered in part by a University of Michigan instrument onboard NASA's MESSENGER spacecraft.

Departing shots: The top left image was taken when MESSENGER was about 34,000 kilometers (21,000 miles) from Mercury, and the bottom right image was snapped from a distance of about 400,000 kilometers (250,000 miles). Mercury and Earth are the only two terrestrial planets in the solar system with magnetospheres produced by an intrinsic magnetic field. (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington)

U-M's Fast Imaging Plasma Spectrometer (FIPS) on Jan. 14 took the first direct measurements of Mercury's magnetosphere to determine how the planet interacts with the space environment and the Sun.

The solar wind, a stream of charged particles, fills the entire solar system. It interacts with all planets, but bears down on Mercury, 2/3 closer than the Earth to the Sun.

Earth's magnetosphere is strong enough to protect us from the solar wind's radiation, but Mercury's magnetic field is comparatively weaker.

"From our magnetic measurements, we can tell that Mercury is managing to stand up to a lot of the solar wind and protect the surface of the planet, at least in some spots. Even though the magnetic field was weak, it was enough," said Thomas Zurbuchen, FIPS instrument project leader and a professor in the U-M Department of Atmospheric, Oceanic and Space Science.

Zurbuchen said scientists can tell Mercury is putting up a good fight because instruments detected a layer of much slower-moving magentospheric plasma around the planet.

It's possible that the magnetosphere shield has holes. Scientists found ions in the magnetosphere that may have been knocked off the surface by the solar wind at the poles, for example. The source and chemical composition of the ions is still unclear, Zurbuchen said. The particles could also be from the planet's thin atmosphere.

"Mercury's magnetosphere is more similar to Earth's than we might have thought," Zurbuchen said.

The spacecraft did find one major difference. Mercury has no Van Allen Belts, wing-shaped regions of energetic particles trapped by Earth's magnetic field.

"We flew through the region they would be in and they just weren't there," Zurbuchen said. "It could be that they're intermittent, but when we were there, they weren't."

Mercury and Earth are the only two terrestrial planets in the solar system with magnetospheres produced by an intrinsic magnetic field.

This was the first of three planned flybys of Mercury. MESSENGER is scheduled to enter orbit in 2011.

Adapted from materials provided by University of Michigan.

Read the rest of this entry »

Asteroid To Make Rare Close Flyby Of Earth January 29

Daily Science Journal (Jan. 25, 2008) — Scientists are monitoring the orbit of asteroid 2007 TU24. The asteroid, believed to be between 150 meters (500 feet) and 610 meters (2,000 feet) in size, is expected to fly past Earth on Jan. 29, with its closest distance being about 537,500 kilometers (334,000 miles) at 12:33 a.m. Pacific time (3:33 a.m. Eastern time). It should be observable that night by amateur astronomers with modest-sized telescopes.

The illustration from an amateur astronomer shows the asteroid's track on the sky for 3 days near the time of the close Earth approach as seen from the city of Philadelphia. (Credit: Dr. Dale Ireland, Silverdale, WA)

Asteroid 2007 TU24 was discovered by the NASA-sponsored Catalina Sky Survey on Oct. 11, 2007. Scientists at NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif., have determined that there is no possibility of an impact with Earth in the foreseeable future.

"This will be the closest approach by a known asteroid of this size or larger until 2027," said Don Yeomans, manager of the Near Earth Object Program Office at JPL. "As its closest approach is about one-and-a-half times the distance of Earth to the moon, there is no reason for concern. On the contrary, Mother Nature is providing us an excellent opportunity to perform scientific observations."

Asteroid 2007 TU24 will reach an approximate apparent magnitude 10.3 on Jan. 29-30 before quickly becoming fainter as it moves farther from Earth. On that night, the asteroid will be observable in dark and clear skies through amateur telescopes with apertures of at least 7.6 centimeters (3 inches). An object with a magnitude of 10.3 is about 50 times fainter than an object just visible to the naked eye in a clear, dark sky.

NASA detects and tracks asteroids and comets passing close to Earth. The Near Earth Object Observation Program, commonly called "Spaceguard," discovers, characterizes and computes trajectories for these objects to determine if any could be potentially hazardous to our planet.

Adapted from materials provided by NASA/Jet Propulsion Laboratory.

Read the rest of this entry »

Flyby Of Mercury Coming Up In NASA's Messenger Mission

Daily Science Journal (Jan. 11, 2008) — NASA will point a power-packed $8.7 million University of Colorado at Boulder space instrument at some of the last unexplored terrain in the inner solar system when the MESSENGER spacecraft whips within 125 miles of Mercury's surface Jan. 14 at a mind-boggling 141,000 miles per hour.

Artist's concept of the NASA's MESSENGER spaceraft at Mercury. (Credit: NASA)

Launched in August 2004, MESSENGER has already flown by Venus twice and will make the first of three flybys of Mercury next week before finally settling into orbit around Mercury in 2011. The only other time Mercury was visited by a spacecraft was in 1974 and 1975, when NASA's Mariner 10 spacecraft made three flybys and mapped roughly 45 percent of the bizarre planet's hot, rocky surface, according to NASA.

The car-sized MESSENGER spacecraft is carrying seven instruments -- a camera, a magnetometer, an altimeter and four spectrometers. The Mercury Atmospheric and Surface Composition Spectrometer, or MASCS, built by CU-Boulder's Laboratory for Atmospheric and Space Physics, was miniaturized to weigh less than seven pounds.

During the flyby, the probe’s instruments will gather data essential to planning the MESSENGER mission’s orbital phase. MESSENGER’s scientific instruments will begin to address the mission goals of:

• mapping the elemental and mineralogical composition of Mercury’s surface;
• imaging globally the surface at a resolution of hundreds of meters or better;
• determining the structure of the planet’s magnetic field;
• measuring the planet’s gravitational field structure; and
• characterizing exospheric neutral particles and magnetospheric ions and electrons.

The instrument will make measurements of Mercury's surface and tenuous atmosphere, said LASP Senior Research Associate William McClintock, a MESSENGER co-investigator who led the MASCS instrument development team. MASCS breaks up light like a prism, and since each element and compound in the universe has a unique spectral "signature," scientists can determine the distribution and abundance of various minerals and gases on the planet's surface and its atmosphere.

"Believe it or not, scientists have only a vague idea today about the composition of Mercury's surface," said McClintock. "The instrument will make ultraviolet, visible and near infrared observations of the surface of Mercury, which together should tell us a lot more about the planet's composition, formation and evolution."

MESSENGER is slated to zip by Mercury at about 11:25 a.m. MST on Jan. 14 and take data and images for about 90 minutes, said LASP's Mark Lankton, program manager for MASCS. The data will be sent via NASA's Deep Space Network to the Applied Physics Laboratory at Johns Hopkins University -- which is managing the mission for NASA -- where mission scientists, including researchers and students at LASP's Space Technology Building at the CU Research Park, will access it electronically, he said.

The circuitous, 4.9 billion-mile-journey to Mercury requires more than seven years and 13 loops around the sun to guide it closer to Mercury's orbit. The craft is equipped with a large sunshade and heat-resistant ceramic fabric to protect it from the sun. More than half of the weight of the 1.2-ton spacecraft consists of propellant and helium.

"The LASP team is really spun up for this flyby," said Lankton. "It's very exciting, because this is the beginning of the science phase of the MESSENGER mission. It's a chance for us to make observations that have never been made before."

MASCS will scan Mercury's thin atmosphere -- known as the exosphere -- to determine its composition, and the spacecraft will fly through a comet-shaped cloud of sodium enveloping the planet during the flyby, said McClintock. "We will fly it right down the cloud's tail," he said. "Understanding how the cloud is replenished with sodium is one of the many pieces of this giant puzzle at Mercury we hope to solve."

LASP Director Daniel Baker, also a co-investigator on the MESSENGER mission, will be studying Mercury's magnetic field and its interaction with the solar wind, including violent "sub-storms" that occur in the planet's vicinity. The strong magnetic field on Mercury indicates it most likely has a liquid or molten core like that on Earth, Baker said.

Mercury is about two-thirds of the way nearer to the sun than Earth and is bombarded with 10 times the solar radiation, said Baker. Sandwiched by the sun and Mercury -- which has daytime temperatures of about 800 degrees Fahrenheit -- the MESSENGER spacecraft will "essentially be on a huge rotisserie," he said.

LASP's vast experience in space during the last several decades should serve the team well. "We are the only space lab in the world to design and build instruments that are either on the way to or have visited every planet in the solar system," Baker said. "Because of our successes, I view our scientists, engineers and support staff and students like a Super Bowl team. We have star players at every position."

Dozens of undergraduates and graduate students will be involved in analyzing data as information and images begin pouring back to Earth from MESSENGER, dubbed "the little spacecraft that could" by LASP scientists. "This mission is going to be a field day for students, not only at CU-Boulder, but for students all over the world," said Baker.

Adapted from materials provided by University of Colorado at Boulder.

Read the rest of this entry »

Astronomers Monitor Asteroid To Pass Near Mars

Daily Science Journal (Dec. 21, 2007) — Astronomers funded by NASA are monitoring the trajectory of an asteroid estimated to be 50 meters (164 feet) wide that is expected to cross Mars' orbital path early next year. Observations provided by the astronomers and analyzed by NASA's Near-Earth Object Office at the Jet Propulsion Laboratory in Pasadena, Calif., indicate the object may pass within 30,000 miles of Mars at about 6 a.m. EST (3 a.m. PST) on Jan. 30, 2008.

This artist rendering uses an arrow to show the predicted path of the asteroid on Jan. 30, 2008, and the orange swath indicates the area it is expected to pass through. Mars may or may not be in its path. (Credit: NASA/JPL)

"Right now asteroid 2007 WD5 is about half-way between Earth and Mars and closing the distance at a speed of about 27,900 miles per hour," said Don Yeomans, manager of the Near Earth Object Office at JPL. "Over the next five weeks, we hope to gather more information from observatories so we can further refine the asteroid's trajectory."

NASA detects and tracks asteroids and comets passing close to Earth. The Near Earth Object Observation Program, commonly called "Spaceguard," plots the orbits of these objects to determine if any could be potentially hazardous to our planet.

Asteroid 2007 WD5 was first discovered on Nov. 20, 2007, by the NASA-funded Catalina Sky Survey and put on a "watch list" because its orbit passes near Earth. Further observations from both the NASA-funded Spacewatch at Kitt Peak, Ariz., and the Magdalena Ridge Observatory in New Mexico gave scientists enough data to determine that the asteroid was not a danger to Earth, but could potentially impact Mars. This makes it a member of an interesting class of small objects that are both near Earth objects and "Mars crossers."

Because of current uncertainties about the asteroid's exact orbit, there is a 1-in-75 chance of 2007 WD5 impacting Mars. If this unlikely event were to occur, it would be somewhere within a broad swath across the planet north of where the Opportunity rover is located.

"We estimate such impacts occur on Mars every thousand years or so," said Steve Chesley, a scientist at JPL. "If 2007 WD5 were to thump Mars on Jan. 30, we calculate it would hit at about 30,000 miles per hour and might create a crater more than half-a-mile wide." The Mars Rover Opportunity is exploring a crater approximately this size right now.

Such a collision could release about three megatons of energy. Scientists believe an event of comparable magnitude occurred here on Earth in 1908 in Tunguska, Siberia, but no crater was created. The object was disintegrated by Earth's thicker atmosphere before it hit the ground, although the air blast devastated a large area of unpopulated forest.

NASA and its partners will continue to track asteroid 2007 WD5 and will provide an update in January when further information is available. For more information on the Near Earth Object program, visit: http://neo.jpl.nasa.gov/.

Adapted from materials provided by NASA/Jet Propulsion Laboratory.

Read the rest of this entry »

Mars Express: Hummocky And Shallow Maunder Crater , One Mars Orbiter Takes First Photos Of Other Orbiters

Daily Science Journal (Oct. 17, 2007) — The High Resolution Stereo Camera (HRSC) on ESA’s Mars Express orbiter has obtained pictures of the Noachis Terra region on Mars, in particular, the striking Maunder crater.

The above image shows the striking Maunder crater located in the region of Noachis Terra on Mars. The crater lies at 50° South and 2° East. The High Resolution Stereo Camera (HRSC) on ESA's Mars Express orbiter took pictures of the Noachis Terra region during orbits 2412 and 2467 on 29 November and 14 December 2005 respectively, with a ground resolution of approximately 15 metres per pixel. (Credit: ESA/DLR/FU Berlin (G. Neukum))

Maunder crater lies at 50° South and 2° East, approximately in the center of Noachis Terra.

The impact crater, named after the british astronomer Edward W. Maunder (1851-1928), is located halfway between Argyre Planitia and Hellas Planitia on the southern Highlands of Mars.

With a diameter of 90 kilometres and a depth of barely 900 metres, the crater is not one of the largest impact craters on Mars at present, but it used to be much deeper. It has since been filled partially with large amounts of material.

The west of the crater experienced a major slope failure, during which a large landslide transported loose material eastward, to the inner parts of the crater. The edges of the crater rim that collapsed exhibit gullies which might be associated with the mass transport of the material.

The transition zone from the western rim of the crater to the rather smooth crater floor on the eastern edge shows hummocky terrain. Such terrain exhibits small, irregularly-shaped hills and valleys. The hummocky terrain in the Maunder crater was formed by deposition of landslide debris.

In the east, the crater floor is bounded by a trough, approximately 700 metres deep. The trough may be associated with a landslide on the western edge of the crater. Some gullies can be seen on the upper edge of the trough which is possible evidence for water seepage.

The small, 500 to 2500-metre long, dark features on the crater floor are eye-catching. These features are called Barchan dunes, one of the most abundant dune forms in arid environments. Dunes of this kind are also found on Earth, for example in the West-African Namib desert.

The colour scenes have been derived from the three HRSC-colour channels and the nadir channels. The perspective views have been calculated from the digital terrain model derived from the HRSC stereo channels. The anaglyph image was calculated from the nadir channels and two stereo channels, stereoscopic glasses are required for viewing. The 3-D (anaglyph) picture has been put together from several individual 3-D images of different scenes, enhancing the view over larger areas.

Adapted from materials provided by European Space Agency.

---------------------------------------------------------------------------

Add On Article :

One Mars Orbiter Takes First Photos Of Other Orbiters

Photographs from NASA's Mars Global Surveyor spacecraft released today are the first pictures ever taken of a spacecraft orbiting a foreign planet by another spacecraft orbiting that planet.

This view is an enlargement of an image of NASA's Mars Odyssey spacecraft taken by the Mars Orbiter Camera aboard NASA's Mars Global Surveyor while the two spacecraft were about 90 kilometers (56 miles) apart. (Image courtesy of NASA/Jet Propulsion Laboratory)

The new images of the European Space Agency's Mars Express and NASA's Mars Odyssey are available on the Internet from NASA at http://www.nasa.gov/vision/universe/solarsystem/mgs-images.html and from Malin Space Science Systems, the San Diego company that built and operates the camera, at http://www.msss.com/mars_images/moc/2005/05/19/index.html.

Mars Global Surveyor has been orbiting Mars since 1997, Mars Odyssey since 2001. Both are managed for NASA by the Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif. Mars Express has been in orbit since late 2003.

Mars Express was passing about 155 miles away when the Mars Orbiter Camera on Mars Global Surveyor photographed it on April 20. The next day, the camera caught Mars Odyssey passing 56 to 84 miles away.

All three spacecraft are moving at almost 7,000 miles per hour, and at 62 miles distance the field-of-view of the Mars Orbiter Camera is only 830 yards across. If timing had been off by only a few seconds, the images would have been blank.

The images were obtained by the Mars Global Surveyor operations teams at Lockheed Martin Space Systems, Denver; JPL and Malin Space Science Systems.

Adapted from materials provided by NASA/Jet Propulsion Laboratory.

Read the rest of this entry »

Mars: Impact Craters In Tyrrhena Terra Clearly Imaged , Water Ice In Crater At Martian North Pole

Daily Science Journal (Aug. 2, 2007) — The High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express obtained images of the Tyrrhena Terra region on Mars.

Tyrrhena Terra, perspective view. (Credit: ESA/DLR/FU Berlin (G. Neukum))

On 10 May 2007, the pictures of the region located at 18° South and 99° East were taken during orbit number 4294 with a ground resolution of approximately 15 metres per pixel.

Tyrrhena Terra is part of the ancient, heavily cratered southern Martian highlands. The region is located north of Hellas Planitia, the largest impact basin on Mars. The image scene exhibits three impact craters, located at the eastern border of Tyrrhena Terra with Hesperia Planum.

The western part of the scene is dominated by a 35 kilometre-wide and approximately 1000 metre-deep impact crater with an extremely steep rim. The rim rises up to 400 metres above the surrounding plains.

The crater is surrounded by multiple layers of material ejected during the impact. These so called ‘ejecta blankets’ spread up to a distance of 50 kilometres around the crater.

Their round, lobate appearance hints at possible ice- and water-rich subsurface material.

The raised feature in the centre of the crater most likely originated from the elastic rebound of compressed subsurface material after the impact. This feature is called 'central peak' or 'central uplift'. This is comparable to what happens when a drop of water hits a puddle.

Another, 18 kilometre-long and approximately 750 metre-deep impact crater, in all likelihood a ‘double impact crater’, is located south of the large crater.

These ‘double impact craters’ develop when two objects, possibly part of the same fragmented object, hit the surface almost simultaneously.

The impact that formed the larger northern crater, which displays an intact crater wall, occurred after the double-impact crater was formed. The ejecta from this later impact has reshaped the double-impact crater.

The northern part has been filled by ejecta and the material is present even at the bottom of the crater, in the direction of the point of impact (towards the larger, neighbouring crater).

The colour scenes have been derived from the three HRSC colour channels and the nadir channel. The perspective views have been calculated from the Digital Terrain Model derived from the HRSC stereo channels. The anaglyph images were calculated by putting together data from the nadir channel and one stereo channel. The black and white high-resolution images were derived from the nadir channel which provides the highest level of detail.

Adapted from materials provided by European Space Agency.

--------------------------------------------------------

Add On Article :

Water Ice In Crater At Martian North Pole

New images, taken by the High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express spacecraft, show a patch of water ice sitting on the floor of an unnamed crater near the Martian north pole.

Perspective view of crater with water ice - looking east. (Credits: ESA/DLR/FU Berlin (G. Neukum))

The HRSC obtained these images during orbit 1343 with a ground resolution of approximately 15 metres per pixel. The unnamed impact crater is located on Vastitas Borealis, a broad plain that covers much of Mars's far northern latitudes, at approximately 70.5° North and 103° East.

The crater is 35 kilometres wide and has a maximum depth of approximately 2 kilometres beneath the crater rim. The circular patch of bright material located at the centre of the crater is residual water ice.

This white patch is present all year round, as the temperature and pressure are not high enough to allow sublimation of water ice.

It cannot be frozen carbon dioxide since carbon dioxide ice had already disappeared from the north polar cap at the time the image was taken (late summer in the Martian northern hemisphere).

There is a height difference of 200 metres between the crater floor and the surface of this bright material, which cannot be attributed solely to water ice.

It is probably mostly due to a large dune field lying beneath this ice layer. Indeed, some of these dunes are exposed at the easternmost edge of the ice.

Faint traces of water ice are also visible along the rim of the crater and on the crater walls. The absence of ice along the north-west rim and walls may occur because this area receives more sunlight due to the Sun’s orientation, as highlighted in the perspective view.

The colour images were processed using the HRSC nadir (vertical view) and three colour channels. The perspective views were calculated from the digital terrain model derived from the stereo channels.

The 3D anaglyph images were created from the nadir channel and one of the stereo channels. Stereoscopic glasses are needed to view the 3D images Image resolution has been decreased for use on the internet.

Adapted from materials provided by European Space Agency.

Read the rest of this entry »

Computer Models Suggest Planetary And Extrasolar Planet Atmospheres

Daily Science Journal (Jun. 21, 2007) — The world is abuzz with the discovery of an extrasolar, Earth-like planet around the star Gliese 581 that is relatively close to our Earth at 20 light years away in the constellation Libra.

Artist's impression of the five-Earth mass planet, Gliese 581 c, found in the habitable zone around the red dwarf Gliese 581, with the instrument HARPS on the ESO 3.6-m telescope. (Credit: European Southern Observatory)

Bruce Fegley, Jr., Ph.D., professor of earth and planetary sciences in Arts & Sciences at Washington University in St. Louis, has worked on computer models that can provide hints to what comprises the atmosphere of such planets and better-known celestial bodies in our own solar system.

New computer models, from both Earth-based spectroscopy and space mission data, are providing space scientists compelling evidence for a better understanding of planetary atmospheric chemistry. Recent findings suggest a trend of increasing water content in going from Jupiter (depleted in water), to Saturn (less enriched in water than other volatiles), to Uranus and Neptune, which have large water enrichments.

"The farther out you go in the solar system, the more water you find," said Fegley.

Fegley provided an overview of comparative planetary atmospheric chemistry at the 233rd American Chemical Society National Meeting, held March 25-29, 2007, in Chicago. Fegley and Katharina Lodders-Fegley, Ph.D., research associate professor of earth and planetary sciences, direct the university's Planetary Chemistry Laboratory.

"The theory about the Gas Giant planets (Jupiter, Saturn, Uranus, and Neptune) is that they have primary atmospheres, which means that their atmospheres were captured directly from the solar nebula during accretion of the planets," Fegley said.

Gas Giants

He said that Jupiter has more hydrogen and helium and less carbon, nitrogen and oxygen than the other Gas Giant planets, making its composition closer to that of the hydrogen- and helium-rich sun. The elements hydrogen, carbon and oxygen are predominantly found as water, the gases molecular hydrogen and methane and in the atmospheres of the Gas Giant planets.

"Spectroscopic observations and interior models show that Saturn, Uranus and Neptune are enriched in heavier elements," he said. "Jupiter, based on observations from the Galileo Probe, is depleted in water. People have thought that Galileo might just have gone into a dry area. But Earth-based observations show that the carbon monoxide abundance in Jupiter's atmosphere is consistent with the observed abundances of methane, hydrogen and water vapor. This pretty much validates the Galileo Probe finding."

The abundances of these four gases are related by the reaction CH4+H20 = CO+3H2. Thus, observations of the methane, hydrogen and CO abundances can be used to calculate the water vapor abundance. Likewise, Earth-based observations of methane, hydrogen and carbon monoxide in Saturn's atmosphere show that water is less enriched than methane.

In contrast, observations of methane, hydrogen and carbon monoxide in the atmospheres of Uranus and Neptune show that water is greatly enriched in these two planets. Although generally classed with Jupiter and Saturn, Uranus and Neptune are water planets with relatively thin gaseous envelopes.

"On the other hand, the terrestrial planets Venus, Earth and Mars have secondary atmospheres formed afterwards by outgassing — heating up the solid material that was accreted and then releasing the volatile compounds from it," Fegley said. "That then formed the earliest atmosphere."

He said that by plugging in models he's done on the outgassing of chondritic materials and using photochemical models of the effects of UV sunlight, he and his collaborator Laura Schaefer, a research assistant in the Washington University Department of Earth and Planetary Sciences, can speculate on the atmospheric composition of Earth-like planets in other solar systems.

"With new theoretical models we are able to surmise the outgassing of materials that went into forming the planets, and even make predictions about the atmospheres of extrasolar terrestrial planets," he said.

"Because the composition of the galaxy is relatively uniform, most stars are like the sun — hydrogen-rich with about the same abundances of rocky elements — we can predict what these planetary atmospheres would be like," Fegley said. "I think that the atmospheres of extrasolar Earth-like plants would be more like Mars or Venus than the Earth."

Fegley said that photosynthesis accounts for the oxygen in Earth's atmosphere; without it, the Earth's atmosphere would consist of nitrogen, carbon dioxide and water vapor, with only small amounts of oxygen. Oxygen is 21 percent of Earth's atmosphere; in contrast, Mars has about one-tenth of one percent made by UV sunlight destroying carbon dioxide.

"I see Mars today as a great natural laboratory for photochemistry; Venus is the same for thermochemistry, and Earth for biochemistry," he said. "Mars has such a thin atmosphere compared to Earth or Venus. UV light can penetrate all the way down to the Martian surface before it's absorbed. That same light on Earth is mainly absorbed in the ozone layer in the lower Earth stratosphere. Venus is so dense that light is absorbed by a cloud layer about 45 kilometers or so above the Venusian surface."

Adapted from materials provided by Washington University in St. Louis.

Read the rest of this entry »

Panel Will Study Mars Global Surveyor Events , Are You Ready For Mars?

Daily Science Journal (Jun. 16, 2007) — NASA has formed an internal review board to look more in-depth into why NASA's Mars Global Surveyor went silent in November 2006 and recommend any processes or procedures that could increase safety for other spacecraft.

Artist's concept of Mars Global Surveyor. (Image credit: NASA/JPL)

Mars Global Surveyor launched in 1996 on a mission designed to study Mars from orbit for two years. It accomplished many important discoveries during nine years in orbit. On Nov. 2, the spacecraft transmitted information that one of its arrays was not pivoting as commanded. Loss of signal from the orbiter began on the following orbit.

Mars Global Surveyor has operated longer at Mars than any other spacecraft in history and for more than four times as long as the prime mission originally planned.

The Jet Propulsion Laboratory, Pasadena, Calif., manages Mars Global Surveyor for the NASA Science Mission Directorate, Washington. JPL is a division of the California Institute of Technology in Pasadena. Lockheed Martin Space Systems, Denver, developed and operates the spacecraft.

Information about the mission is available on the Internet at: http://www.nasa.gov/mission_pages/mgs/index.html.

Adapted from materials provided by NASA/Jet Propulsion Laboratory.

---------------------------------------

Add On Article :

Are You Ready For Mars?

ESA’s Mars Express probe is scheduled to arrive at Mars at Christmas: the Beagle 2 lander is expected to touch down on the surface of the Red Planet on the night of 24 to 25 December. Launched on 2 June 2003 from Baikonur (Kazakhstan) on board a Russian Soyuz launcher operated by Starsem, the European probe – built for ESA by a European team of industrial companies led by Astrium – carries seven scientific instruments that will perform a series of remote-sensing experiments designed to shed new light on the Martian atmosphere, the planet’s structure and its geology. In particular, the British-made Beagle 2 lander, named after the ship on which Charles Darwin explored uncharted areas of the Earth in 1830, will contribute to the search for traces of life on Mars through exobiology experiments and geochemistry research. On Christmas Eve the Mars Express orbiter will be steered on a course taking it into an elliptical orbit, where it will safely circle the planet for a minimum of almost 2 Earth years. The Beagle 2 lander - which will have been released from the mother craft a few days earlier (on 19 December) – instead will stay on a collision course with the planet. It too should also be safe, being designed for atmospheric entry and geared for a final soft landing due to a sophisticated system of parachutes and airbags.

On arrival, the Mars Express mission control team will report on the outcome of the spacecraft's delicate orbital insertion manoeuvre. It will take some time for Mars Express to manoeuvre into position to pick communications from Beagle 2. Hence, initially, other means will be used to check that Beagle 2 has landed: first signals from the Beagle 2 landing are expected to be available throughout Christmas Day, either through pick-up and relay of Beagle 2 radio signals by NASA’s Mars Odyssey, or by direct pick-up by the Jodrell Bank radio telescope in the UK. Mars Express will then pass over Beagle 2 in early January 2004, relaying data and images back to Earth. The first images from the cameras of Beagle 2 and Mars Express are expected to be available between the end of the year and the beginning of January 2004.

Adapted from materials provided by European Space Agency.

Read the rest of this entry »

Scientists Gear Up For Mercury Mission Flyby Of Venus

Daily Science Journal (Jun. 5, 2007) — University of Colorado at Boulder researchers will scan Venus during a spacecraft flyby this week using an $8.7 million instrument they designed and built for NASA's MESSENGER Mission, launched in 2004 and speeding toward Mercury.

An artists rendition of NASA's MESSENGER spacecraft, which will make its first flyby of Mercury in 2008. (Credit: Image courtesy of University of Colorado at Boulder)

Built by CU-Boulder's Laboratory for Atmospheric and Space Physics, the instrument will make measurements of the thick clouds and shrouded surface of Venus during the June 5th flyby, said LASP Senior Research Associate William McClintock, a mission co-investigator who led the CU-Boulder instrument development team. Known as the Mercury Atmospheric and Surface Composition Spectrometer, or MASCS, the instrument will compare the atmosphere of Venus with data from other spacecraft that have visited the planet in the past four decades.

"This is our first opportunity for a close flyby of a solar system object with MESSENGER, and we should be able to tell if the atmosphere of Venus has been changing in recent years, " said McClintock. "As importantly, we are using Venus as a test case to learn more about our instrument performance in preparation for the spacecraft's ultimate destination of Mercury."

Carrying seven instruments, MESSENGER will be the first spacecraft ever to orbit Mercury and the first to return data from the hot, rocky planet in more than 30 years. The circuitous, 4.9 billion mile journey to Mercury, which requires more than seven years and 13 loops around the sun, is using the gravity of Venus during its flyby this week to guide it closer to Mercury's orbit.

MESSENGER will make its first flyby of Mercury in January 2008, zipping by it again at a top speed of 141,000 miles per hour in October 2008 before flying by a third time in September 2009 and finally settling into orbit in March 2011. "This is a mission that requires some patience," said Mark Lankton, LASP's program manager for the MASCS instrument. "We are anticipating a brief symphony of action at Venus, and we have a lot of data to take in a hurry."

Dozens of CU-Boulder undergraduate and graduate students will be involved in data analysis from MESSENGER in the coming years, said Lankton.

MASCS's ultraviolet and visible spectrometer will be looking at the cloud composition of Venus. While the surface of Venus is hot enough to melt lead and its atmosphere is filled with noxious carbon dioxide gases and acid rain, Earth and Venus were virtual twins at birth, scientists believe.

The miniaturized MASCS instrument, which took more than three years to develop, weighs less than seven pounds and was built to last, said McClintock. "Many space instruments have a lifetime of only three to four years," he said. "But we knew we had to make this one robust enough to work for more than a decade under harsh conditions."

The MESSENGER spacecraft is about the size of a small economy car and is equipped with a semi-cylindrical thermal shade to protect it from the sun. More than half of the weight of the 1.2-ton spacecraft consists of propellant and helium. "We like to call it the little spacecraft that could," said McClintock.

"This event at Venus will be a very good tune-up for our first flyby of Mercury next January," said LASP Director Daniel Baker, also a co-investigator on the MESSENGER team. "The first encounter with Mercury will be extremely valuable, as it will essentially double the amount of information we now have about the planet."

A space physicist, Baker is interested in the magnetic field of Mercury and its interaction with the solar wind, including "substorms" associated with Mercury's magnetic field that occur in the planet's vicinity. Understanding Mercury's surface, tenuous atmosphere and magnetic field are the keys to understanding the evolution of the inner solar system, he said.

Mercury was visited only once before by a spacecraft, in 1974 and 1975, when NASA's Mariner 10 spacecraft made three flybys and mapped roughly 45 percent of the planet's rocky surface at the time.

MASCS will probe the mineral composition of Mercury's surface, the distribution of gases in its tenuous atmosphere and the workings of a giant, comet-like sodium gas cloud enveloping the planet, said McClintock. The researchers also hope to determine if Mercury ever had volcanoes on its surface and if the permanently shadowed craters at Mercury's poles contain water-ice.

MESSENGER is equipped with a large sunshield and heat-resistant ceramic fabric because Mercury is about two-thirds of the way nearer to the sun than Earth and is bombarded with 10 times the solar radiation. Sandwiched by the sun and Mercury -- which has daytime temperatures of about 800 degrees Fahrenheit -- the spacecraft will "essentially be on a huge rotisserie," said Baker.

Adapted from materials provided by University of Colorado at Boulder.

Read the rest of this entry »