Posted on by Fraser Cain

Saturn’s Eerie Southern Lights

Saturn’s auroral emissions. Image credit: NASA/JPL/University of Colorado. Click to enlarge
New images of Saturn obtained by a University of Colorado at Boulder-led team on June 21 using an instrument on the Cassini spacecraft show auroral emissions at its poles similar to Earth’s Northern Lights.

Taken with the Ultraviolet Imaging Spectrograph aboard the Cassini orbiter, the two UV images, invisible to the human eye, are the first from the Cassini-Huygens mission to capture the entire “oval” of the auroral emissions at Saturn’s south pole. They also show similar emissions at Saturn’s north pole, according to CU-Boulder Professor Larry Esposito, principal investigator of the UVIS instrument built at CU-Boulder’s Laboratory for Atmospheric and Space Physics, and Professor Wayne Pryor of Central Arizona College, a UVIS team member and former CU graduate student.

In the false-color images, blue represents aurora emissions from hydrogen gas excited by electron bombardment, while red-orange represents reflected sunlight. The images show that the aurora lights at the polar regions respond rapidly to changes in the solar wind, said the researchers. Previous images have been taken closer to the equator, making it difficult to see the polar regions.

Major changes in the emissions inside the Saturn south-pole aurora are evident by comparing the two images, which were taken about one hour apart, they said. The brightest spot in the left aurora fades, and a bright spot appears in the middle of the aurora in the second image.

Made by slowly scanning the UVIS instrument across the planet, the images also contain more than 2,000 wavelengths of spectral information within each picture element. Researchers will use the wavelength information to study Saturn’s auroras, gases, and hazes and their changing distributions.

The UVIS observation team includes researchers from CU-Boulder, NASA’s Jet Propulsion Laboratory, Central Arizona College and the University of Southern California.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini- Huygens mission for NASA’s Space Science Mission Directorate in Washington, D.C.

More information on the Cassini-Huygens mission is available at the following Web sites: http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini.

Original Source: CU-Boulder News Release

Posted on by Fraser Cain

Mars Express Preparing to Look Underground

Artist’s impression of MARSIS deployment complete. Image credit: ESA Click to enlarge
MARSIS, the sounding radar on board ESA?s Mars Express spacecraft, is collecting the first data about the surface and the ionosphere of Mars.

The radar started its science operations on 4 July 2005, after the first phase of its commissioning was concluded on the same day. Due to the late deployment of MARSIS, it was decided to split the commissioning, originally planned to last four weeks, into two phases, one of which has just ended and the second one to be started by December this year.

This has given the instrument the chance to start scientific observations earlier than initially foreseen, while still in the Martian night. This is the environmental condition favourable to subsurface sounding, because the ionosphere is more ?energised? during the daytime and disturbs the radio signals used for subsurface observations.

From the beginning of the commissioning, the two 20-metre long antenna booms have been sending radio signals towards the Martian surface and receiving echoes back. ?The commissioning phase confirmed that the radar is working very well, and that it can be operated at full power without interfering with any of the spacecraft systems,? says Roberto Seu, Instrument Manager for MARSIS, from the University of Rome ?La Sapienza?, Italy.

MARSIS is a very complex instrument, capable of operating at different frequency bands. Lower frequencies are best suited to probe the subsurface and the highest frequencies are used to probe shallow subsurface depths, while all frequencies are suited to study the surface and the upper atmospheric layer of Mars.

?During the commissioning we have worked to test all transmission modes and optimise the radar performance around Mars,? says Prof. Giovanni Picardi, Principal Investigator for MARSIS, University of Rome ?La Sapienza?. ?The result is that since we have started the scientific observations in early July, we are receiving very clean surface echoes back, and first indication about the ionosphere.?

The MARSIS radar is designed to operate around the orbit ?pericentre?, when the spacecraft is closer to the planet?s surface. In each orbit, the radar has been switched on for 36 minutes around this point, dedicating the central 26 minutes to subsurface observations and the first and last five minutes of the slot to active ionosphere sounding.

Using the lower frequencies, MARSIS has been mainly investigating on the northern flat areas between 30? and 70? latitudes, at all longitudes. ?We are very satisfied about the way the radar is performing. In fact, the surface measurements taken so far match almost perfectly with the existing models of the Mars topography,? said Prof. Picardi. Thus, these measurements provided an excellent test.

The scientific reason to concentrate the first data analysis on flat regions lies in the fact that the subsurface layers here are in principle easier to identify, but the question is still tricky. ?As the radar is appearing to work so well for the surface, we have good reasons to think that the radio waves are correctly propagating also below the surface,? added Prof. Picardi.

?The biggest part of our work just started, as we now have to be sure that we clearly identify and isolate those echoes that come from the subsurface. To do this, we have to carefully screen all data and make sure that signals that could be interpreted as coming from different underground layers are not actually produced by surface irregularities. This will keep us occupied for a few more weeks at least.?

The first ionospheric measurements performed by MARSIS have also revealed some interesting preliminary findings. The radar responds directly to the number of charged particles composing the ionosphere (plasma). This has shown to be higher than expected at times.

?We are now analysing the data to find out if such measurements may result from sudden increases of solar activity, like the one observed on 14 July, or if we have to make new hypotheses. Only further analysis of the data can tell us,? said Jeffrey Plaut, Co-Principal Investigator, from NASA Jet Propulsion Laboratory, Pasadena, USA.

MARSIS will continue send signals to hit the surface and penetrate the subsurface until the middle of August, when the nighttime portion of the observations will have almost ended. After that, observation priority will be given to other Mars Express instruments that are best suited to work during daytime, such as the HRSC camera and the OMEGA mapping spectrometer.

However, MARSIS will continue surface and ionospheric investigations during daytime, with the ionospheric sounding being reserved for more than 20% percent of all Mars Express orbits, in all possible Sun illumination conditions.

In December 2005, the Mars Express orbit pericentre will enter the nighttime again. By then, the pericentre will have moved closer to the South pole, allowing MARSIS to restart optimal probing of the subsurface, this time in the southern hemisphere.

Original Source: ESA Portal

Posted on by Fraser Cain

Discovery and ISS Will Be Visible in the Southeast US

Discovery’s ground track on August 6th. Image credit: Chris Peat and Heavens Above. Click to enlarge
If you live in south Florida, central Texas or near the Mississippi River Delta, you’re in for a treat. This weekend the space shuttle Discovery and the International Space Station (ISS) are going to orbit over your part of the country. Shining like very bright stars, the two ships will glide in tandem across the sky–a lovely sight.

That’s the good news. The bad news is that you have to wake up before dawn to see them, but they’re worth waking up for.

The flybys commence on Saturday morning, August 6th, at 05:50 a.m. CDT when the pair can be seen from New Orleans, Mobile, Biloxi and surrounding areas. Discovery will have just undocked from the ISS about three hours earlier. This means the two ships will be separated, but still close together. Side by side apparitions of two bright spaceships are rare and beautiful.

“Based on their predicted separation of 7 km, their angular separation should be 1o–only twice the diameter of a full moon,” says independent satellite tracking expert Ted Molczan.

Which ship is which? The brighter light is the shuttle. Although Discovery is smaller than the ISS, its super-white top reflects more sunlight. Both ships should be easy to see in the deep-blue dawn sky.

Bonus: Discovery and the ISS, coincidentally, pass close to the planet Mars. If you’re an early riser, you’ve probably noticed Mars shining high in the sky before sunrise. If you haven’t noticed Mars yet, you will on August 6th. Discovery and the ISS will lead you right to the red planet: sky map.

August 7th should be a good morning, too, with flybys over south Florida, parts of Texas and Oklahoma. By then, says Molczan, “the two ships will be more than 250 km apart; the ISS would trail Discovery by 30 seconds or so — still worth observing, but not as spectacular as on August 6th.” Miami and Dallas are favored with particularly good apparitions: the two spaceships will be bright and, once again, close to Mars when they pass overhead.

Finally, on the morning of August 8th, the shuttle is due to land at the Kennedy Space Center. Reentry won’t be visible from much of the United States. The shuttle’s intended trajectory takes it over the Yucatan Peninsula and the Gulf of Mexico.

To the unaided eye, Discovery and the ISS are compact points of light. You can’t actually discern, e.g., the wings of the shuttle or the station’s vast solar arrays.

How about looking through a telescope?

It’s not easy, but it can be done. The two spaceships move slowly across the sky, taking about five minutes to cross from horizon to horizon. With a little practice, you can train a small telescope on the pair and manually track them. Then you can see their outlines. The space station’s T-shaped solar arrays are eye-catching; people who have seen them are impressed by their eerie copper color.

If you’ve never seen a shuttle flyby before, however, don’t spend precious minutes fumbling with a telescope. Look up and, using nothing but your eyes, simply enjoy the view.

Original Source: NASA News Release

Posted on by Fraser Cain

Astronauts Remember Columbia Crew

Discovery’s heat shielding tiles. Image credit: NASA Click to enlarge
Space Shuttle Discovery?s heat shield is cleared for the return to Earth early Monday after mission managers decided today that a fourth spacewalk to deal with a puffed out thermal blanket is unnecessary. Wind tunnel tests overnight at NASA?s Ames Research Center in California showed little chance of any significant debris coming from the blanket at supersonic speeds. Further engineering analysis showed any debris released from the blanket was unlikely to hit structures on Discovery.

Thursday?s Mission Management Team decision put to rest the work that was being done to assess the health of the thermal protection system. The tiles and reinforced carbon-carbon on Discovery?s wings and nose were cleared earlier for entry.

Discovery and International Space Station crewmembers Thursday delivered a moving tribute to members of the Columbia crew and others, astronauts and cosmonauts, who lost their lives in the human exploration of space.

Each crewmember, in red shirt with Columbia’s STS-107 mission patch spoke during the tribute as the docked spacecraft flew over the southern Indian Ocean approaching a sunset. Station Science Officer John Phillips said: “To the crew of Columbia, as well as the crews of Challenger, Apollo 1, Soyuz 1 and 11, and to those who have courageously given so much, we now offer our enduring thanks.?

Mission Specialist Soichi Noguchi of the Japan Aerospace Exploration Agency repeated Phillips’ words in Japanese during the tribute, and Station Commander Sergei Krikalev spoke them in Russian. For the text of the tribute, please see:

http://www.nasa.gov/returntoflight/crew/sts114_exp11_tribute.html

After their successful Wednesday spacewalk, Discovery and Station crewmembers continued transfer activities, mostly packing the Multi-Purpose Logistic Module Raffaello with items from the Station. The pressurized cargo carrier is to be unberthed Friday from the Station’s Unity Node and returned to Discovery’s cargo bay for the trip back to Earth.

Pilot Jim Kelly and Mission Specialist Wendy Lawrence attached the Station’s Canadarm2 to Raffaello in preparation for its unberthing.

Discovery Commander Eileen Collins, spacewalking Mission Specialist Steve Robinson and Mission Specialist Charlie Carmada talked with reporters from the Associated Press and NBC. A little later Collins and Noguchi spoke with Japanese Prime Minister Junichiro Koizumi, Japanese astronaut Mamoru Mohri and others, including Japanese students.

Crewmembers had an hour together for a common meal, then the seven Discovery astronauts had the afternoon off. The Station crew spent about two hours preparing equipment for the unberthing of Raffaello.

Original Source: NASA News Release

Posted on by Fraser Cain

Space Shuttle Cleared for Landing

Discovery in orbit. Image credit: NASA Click to enlarge
Space Shuttle mission managers today completed their assessment of Discovery’s fitness to handle the rigors of re-entry into the atmosphere.

“We have cleared Discovery to re-enter,” said Wayne Hale, chairman of the Mission Management Team (MMT), during a news conference at NASA’s Johnson Space Center, Houston.

The MMT determined the Orbiter’s heat shield and other systems are in good shape. They also decided a spacewalk is unnecessary to repair damage to a thermal blanket on Discovery’s outer skin.

Earlier this week, Discovery (STS-114) mission managers determined two components of the Shuttle’s Thermal Protection System, tile and Reinforced Carbon-Carbon, were fit for re-entry and landing. Today, the MMT cleared the final element: thermal blankets. One blanket is slightly torn and billowing in orbit.

The MMT considered the results of overnight testing at NASA’s Ames Research Center, Moffett Field, Calif. Engineers ran samples of torn thermal blankets through wind tunnels at velocities many times faster than the speed of sound. Tests showed it was highly unlikely the blanket would tear off or strike the Orbiter. Other analyses showed the blankets would still protect Discovery from re-entry heat.

Based on the analysis of the blankets and considering the risks of a fourth spacewalk, mission managers decided the torn blanket did not need repair. “We’ve assessed this risk to the very best of our knowledge, and we believe the risk is small,” Hale said.

New imaging capabilities developed after the Space Shuttle Columbia accident allowed mission managers to see and analyze the torn thermal blanket. Data from the images were used to re-create blanket samples for the wind tunnel tests. “I think it’s remarkable we have capability to look at these small things in flight,” Hale said.

Discovery is set to land Monday, Aug. 8 at NASA’s Kennedy Space Center, Fla. The first opportunity for Commander Eileen Collins to land the Space Shuttle is at 4:46 a.m. EDT.

For information about STS-114 on the Web, visit:
http://www.nasa.gov/returntoflight

Original Source: NASA News Release

Posted on by Fraser Cain

Massive Asteroids Transformed the Earth’s Surface

Asteroid. Image credit: NEAR Click to enlarge
A cluster of at least three asteroids between 20 and 50 kilometres across colliding with Earth over 3.2 billion years ago caused a massive change in the structure and composition of the earth?s surface, according to new research by ANU earth scientists.

According to Dr Andrew Glikson and Mr John Vickers from the Department of Earth and Marine Sciences at ANU, the impact of these asteroids triggered major earthquakes, faulting, volcanic eruption and deep-seated magmatic activity and interrupted the evolution of parts of the Earth?s crust.

The research extends the original discovery of extraterrestrial impact deposits, discovered in South Africa by two US scientists, D.R. Lowe and G.R. Byerly, identifying their effects in the Pilbara region in Western Australia.

?Our findings are further evidence that the seismic aftershocks of these massive impacts resulted in the abrupt termination of an over 300 million years-long evolutionary stage dominated by basaltic volcanic activity and protracted accretion of granitic plutons,? Dr Glikson said.

The identification of impact ejecta ? materials ejected by the hitting asteroid ? is based on unique minerals and chemical and isotopic compositions indicative of extraterrestrial origin, including iridium anomalies.

The impact ejecta from the Barberton region in the eastern Transvaal indicate the formation of impact craters several hundred kilometres in diameter in oceanic regions of the earth, analogous to the lunar maria basins (large dark impressions on the surface of the moon). The seismic effects of the impacts included vertical block movements, exposure of deep-seated granites and onset of continental conditions on parts of the earth surface.

In the Pilbara, the formation of fault escarpments and fault troughs is represented by collapse of blocks up to 250-metres wide and 150-metres high, buried canyons and a major volcanic episode 3240 million years ago.

?The precise coincidence of the faulting and igneous activity with the impact deposits, coupled with the sharp break between basaltic crust and continental formations, throws a new light on the role of asteroid impacts in terrestrial evolution,? Dr Glikson said.

Preliminary indications suggest that at about the same time the Moon was also affected by asteroid impacts and by resurgent volcanic activity.

Dr Glikson and Mr Vickers will continue to investigate the extent and effects of large asteroid impacts by studying early terrains in other parts of the world, including India and Canada.

Original Source: ANU News Release

Posted on by Mark Mortimer

Book Review: Cold Dark Matter

Brett’s main character is Morgan O’Brien. She’s a principal investigator based in Ottawa, Ontario and who works for the fictitious National Council of Science and Technology. The plot revolves about a death at the Canadian telescope in Hawaii coupled with a loss of important record books. O’Brien is implored by a friend to investigate, for personal reasons. The story begins in Hawaii with much of the action centring about the telescope and its ancillary buildings as well as the related personnel. After many hooks and twists in the plot, O’Brien returns to Ottawa, timed naturally to amplify the contrasts in weather. There she chases down more leads and journeys through downtown streets and the cottage country in the north of the Gatineaus. The action extends up the government chain to another fictitious unit, a civilian security force attached to the Prime Minister’s Office. From there, and after dancing through some risque steps, O’Brien pounces upon the very unexpected but plausible resolution.

It is not often that I have the pleasure of reading a book partly based in my own city of Ottawa. Because of this, I had a pleasantly warm feeling while reading the passages based on regions I frequent. More important though, I could also easily evaluate the authenticity of its contents. Given this, Alex Brett’s done great work in describing the national capital region, its weather, geography and some of its more colourful elements. Because of this, I expect similar accuracy for the surroundings in Hawaii and the FrancoCanadian telescope though I have been to neither. The sprinkles of astronomical facts and events appear equally reasonable hence lending credence to the assertion that Brett has done her homework.

Apart from the facts, the real substance of a work of fiction are the characters and the plot. Brett points out that all characters are imaginary. Its hard not to believe otherwise as, aside from the investigator, most characters have only a superficial development. We get to know of their jobs and work conditions, what their homes look life from the outside and in, but there is very little about who they are. This is particularly challenging with the guilty party, as they seem to have quite a minor role and presence, yet they wind up being the cause for all the trials and tribulations. The personality of the investigator on the other hand does come through clearly. As is perhaps typical of the genre, she imbibes an amazing amount of caffeine, pushes her body through unbelievable physical challenges and appears to be able to survive with nearly no sleep. Actually, aside from being female, there is not too much differentiating this P.I. from others of the same genre. In many ways, I preferred reading the description of her assistant, a much more complex and intriguing individual with a checkered background and a very likely challenging future.

In addition to the characters, the plot is the driver for mystery aficionados. It must be readily believable yet not entirely obvious. Here, Brett delivers. Connections and twists keep the reader guessing but not frustrated. And like any good mystery, the ending is quite unexpected though not unreasonable given the clues in the story and the setting within the book. I particularly liked seeing a focal point for the crime being technical information rather than the commonly prescribed hard currency.

For a pleasant distraction via a light murder mystery, this book is fine. The plot and main character are constantly moving. The scenes are quite busy and realistic. There’s enough suspense and distractions to keep one guessing right up to the end. One ready improvement would be to reduce the simple diction of present person, past tense. Too often sentences begin with, ‘I felt, I started, I smiled, I read…’. Because of this, the reading feels prescriptive rather than emotive. This prevented me from being fully absorbed as I felt I was reading a newspaper review rather than being a participant in the action.

A good mystery brings together believable characters in a plausible but dastardly scenario. The desire to answer whodunit should be continually fed without giving away too much. Alex Brett’s murder mystery Cold Dark Matter keeps the reader guessing while having great fun playing through observatories in Hawaii and alternate bar scenes in Ottawa. It’s just the thing to have at hand while waiting for the sun to set and the evening’s observing to begin.

Read more reviews, or purchase a copy online from Amazon.com.

Review by Mark Mortimer.

Posted on by Fraser Cain

Hubble Sees a Field of Galaxies

Group of galaxies captured by Hubble. Image credit: Hubble Click to enlarge
Gazing deep into the universe, NASA’s Hubble Space Telescope has spied a menagerie of galaxies. Located within the same tiny region of space, these numerous galaxies display an assortment of unique characteristics. Some are big; some are small. A few are relatively nearby, but most are far away. Hundreds of these faint galaxies have never been seen before until their light was captured by Hubble.

This image represents a typical view of our distant universe. In taking this picture, Hubble is looking down a long corridor of galaxies stretching billions of light-years distant in space, corresponding to looking billions of years back in time. The field shown in this picture covers a relatively small patch of sky, a fraction of the area of the full moon, yet it is richly populated with a variety of galaxy types.

A handful of large fully formed galaxies are scattered throughout the image. These galaxies are easy to see because they are relatively close to us. Several of the galaxies are spirals with flat disks that are oriented edge-on or face-on to our line of sight, or somewhere in between. Elliptical galaxies and more exotic galaxies with bars or tidal tails are also visible.

Many galaxies that appear small in this image are simply farther away. These visibly smaller galaxies are so distant that their light has taken billions of years to reach us. We are seeing these galaxies, therefore, when they were much younger than the larger, nearby galaxies in the image. One red galaxy to the lower left of the bright central star is acting as a lens to a large galaxy directly behind it. Light from the farther galaxy is bent around the nearby galaxy’s nucleus to form a distorted arc.

Sprinkled among the thousands of galaxies in this image are at least a dozen foreground stars that reside in our Milky Way Galaxy. The brightest of these foreground stars is the red object in the center of the image. The stars are easily discernable from galaxies because of their diffraction spikes, long cross-hair-like features that look like they are emanating from the centers of the stars. Diffraction spikes are an image artifact caused by starlight traveling through the telescope’s optical system.

This image is a composite of multiple exposures of a single field taken by the Advanced Camera for Surveys. The image, taken in September 2003, was a bonus picture, taken when one of the other Hubble cameras was snapping photos for a science program. This image took nearly 40 hours to complete and is one of the longest exposures ever taken by Hubble.

Original Source: Hubble News Release

Posted on by Fraser Cain

Cassini’s Zips Past the Death Star

The great eye of Mimas. Image credit: NASA/JPL/SSI Click to enlarge
The great eye of Saturn’s moon Mimas (MY-muss), a 130-kilometer-wide (80-mile) impact crater called Herschel, stares out from the battered moon in this raw image taken by the Cassini spacecraft during a flyby on Aug. 2.

The Herschel crater is the moon’s most prominent feature, and the impact that formed it probably nearly destroyed Mimas. Cassini flew by Mimas at 62,700 kilometers (38,800 miles) above the moons surface, bringing it closer to the little moon than ever before.

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Astronaut Successfully Plucks Out Filler From Shuttle’s Belly

The Expedition 11 and STS-114 crewmembers. Image credit: NASA Click to enlarge
Despite days of anticipation and intense planning, space-walking astronaut Steve Robinson made it look easy as he gently pulled two protruding gap fillers from between thermal protection tiles on Discovery’s underside Wednesday morning.

“It looks like this big patient is cured,” Robinson told delighted flight controllers.

Fellow spacewalker Soichi Noguchi of the Japan Aerospace Exploration Agency helped Robinson with preparations, and from a perch near the end of a Space Station truss acted as observer and communication relay station between Robinson and astronaut Andy Thomas aboard Discovery. Thomas was the onboard coach and monitor for Robinson and Noguchi throughout the 6-hour 1-minute spacewalk. Discovery Pilot Jim Kelly and Mission Specialist Wendy Lawrence operated the Station’s Canadarm2, which moved Robinson to and from the worksite. Today’s spacewalk, the third of the mission, began at 3:48 a.m. CDT and concluded at 9:49 a.m.

Deputy Space Shuttle Program Manager Wayne Hale, in Wednesday?s afternoon briefing, said ?The crew demonstrated consummate professionalism and coolness beyond belief. They [the gap fillers] came out just as we thought they would. It looked easy but was not, which is a tribute to the crew and the team on the ground that planned it, so we?re proud of that.?

Gap fillers like those Robinson removed today are thin, coated Nextel fabric. The protruding gap fillers were identified in photos taken by Station crewmembers using telephoto lenses as Discovery did a slow back flip about 600 feet below before docking.

During the spacewalk Noguchi and Robinson, helped by the Station’s robotic arm, installed an external stowage platform outside the station that will be used to house spare parts. Noguchi also installed another Materials International Space Station Experiment (MISSE). Like its predecessors, MISSE 5 exposes samples of various materials to the harsh space environment for several months.

In other activities, Kelly worked with Mission Specialist Charlie Camarda on an inspection of the repair demonstration tiles in Discovery’s cargo bay. Using the Orbiter Boom Sensor System, they looked at tiles brought up for an experimental repair by Robinson and Noguchi on the mission’s first spacewalk Saturday.

Station crewmembers, Commander Sergei Krikalev and NASA Science Officer John Phillips, continued to stow equipment and supplies on the Station and Shuttle. Discovery Commander Eileen Collins operated shuttle systems and supervised activities.

Hale also said the only part of Discovery?s heat shield not yet cleared for entry is a bulging thermal blanket below the Shuttle commander?s window. Managers will meet Thursday morning to review tests to help determine whether the blanket might pose a concern for entry.

The next STS-114 mission status report will be issued Thursday morning, or earlier, if events warrant.

Original Source: NASA News Release