Posted on by Fraser Cain

Mountain of Sky Survey Data Released

Image credit: SDSS
One of the largest astronomy catalogs ever compiled was released to the public today by the Sloan Digital Sky Survey (SDSS).

With photometric and spectroscopic observations of the sky gathered during the last two years, this second data release (DR2) offers six terabytes of images and catalogs, including two terabytes in an easy to use searchable database.

This public data release provides digital images and measured properties of more than 88 million celestial objects, as well as spectra and redshifts of over 350,000 objects. The data are available from the SDSS Web site (http://www.sdss.org/DR2) or from the SkyServer Web site more attuned to the general public (http://skyserver.sdss.org/).

The SDSS is the most ambitious astronomical survey ever undertaken. A consortium of more than 200 astronomers at 13 institutions around the world, the SDSS will map in detail one-quarter of the entire sky, determining the positions and brightnesses of several hundred million celestial objects. It will also measure the distances to approximately one million galaxies and quasars.

“Getting DR2 out to the broader astronomical community and to the general public will allow these data to be analyzed for projects limited only by the imagination and ingenuity of the user,” said Michael Strauss of Princeton University, scientific spokesperson for the SDSS.

Strauss explained that while members of the SDSS international collaboration have written more than 200 scientific papers with SDSS data, “we feel we’ve barely started. There is far more interesting science to be done and discoveries to be made with these data than we have time or people to do. This is why this data release is so important.” Public searchable data in the survey have doubled from June 2003 to today.

“Many external researchers are already using the data from earlier public releases”, explained Alex Szalay of the Johns Hopkins University, an architect of the SDSS’s data mining tools. In fact, researchers from outside of the consortium wrote roughly half of the SDSS-related papers presented at recent American Astronomical Society meetings. “This is a clear indication that we’ve kept our promise to the scientific community of getting them uniformly high quality data in a timely manner and in a searchable format.”

The first public data release from the SDSS in 2003 contained information on 50 million objects, including spectra and redshifts for almost 200,000 of these objects. The SDSS is an ongoing survey that recorded its first observations in May 1998 and is funded for operations through Summer 2005.

The 2.5-meter SDSS telescope is located at Apache Point Observatory in New Mexico and is operated by the Astrophysical Research Consortium. The telescope has two main instruments: an imaging camera, one of the largest ever built, and a spectrograph capable of recording data from 640 objects at a time. The camera creates images from digital scans through five filters: ultraviolet, green, red, and two infrared bands.

CATALOG OF RESULTS
Scientific findings and ground-breaking discoveries already achieved with the DR2 data from the most distant quasars, to the coolest stars, the properties of galaxies to the sizes of asteroids, the structure of the halo of our Milky Way and the large-scale structure of the universe.

DR2 consists of images from 3,324 square degrees of the Northern sky and more than 88 million galaxies, stars, and quasars. The survey is complete for objects as faint as 22.2 magnitude, three million times fainter than the faintest star that can be seen with the naked eye on a dark night.

In addition to images from the SDSS telescope, the DR2 includes the spectra, and therefore redshifts, of 260,000 galaxies, 36,000 quasars, and 48,000 stars, according to consortium member Mark Subbarao of the University of Chicago. The galaxy and quasar catalogs are the largest ever produced.

SEARCH REFINEMENTS
Jim Gray of Microsoft Corp. was part of the team working to make the observations accessible to the astronomical community and the public. The team developed several algorithms to efficiently search the complicated database.

“The SDSS is a BIG database with researchers making very complicated queries for spatial, color and space parameters,” explained Gray, a distinguished engineer in Microsoft’s Scaleable Servers Research Group and manager of Microsoft’s Bay Area Research Center.

“It has been very rewarding working with the SDSS. The people are very creative, enthusiastic, and bright. The SDSS has shown that we database folks need to do a better job in many ways,” Gray said. “For Microsoft, the SkyServer and Catalog Archive Server are an information-at-your-fingertips project we’ve helped develop for astronomers. I see them as archetypes of what all the sciences need.”

Ani Thakar, an SDSS astronomer from the Johns Hopkins University’s Center for Astrophysical Sciences, who has worked closely with Szalay and Gray on the SkyServer, said the DR2 database has a form-based Web page for imaging and spectroscopic queries.

“This gives astronomers the ability to extract detailed information from the database without having to learn a query language. We’ve also added a batch service that lets users submit queries that are likely to take a long time. They can come back later and pick up the results,” Thakar explained.

DR2 also offers enhanced querying and filtering options like image cutout and finding chart services. Users can cross-identify objects by uploading lists of object positions on the sky.

The SDSS anticipates releasing more data in its ongoing celestial census late this year.

Original Source: SDSS News Release

Posted on by Fraser Cain

Tracking Diseases from Space

Image credit: NASA
Last year more than a million people died of malaria, mostly in Sub-saharan Africa. Outbreaks of Dengue Fever, hantavirus, West Nile Fever, Rift Valley Fever, and even Plague still occasionally strike villages, towns, and whole regions. To the dozens or hundreds who suffer painful deaths, and to their loved ones, these diseases must seem to spring upon them from nowhere.

Yet these diseases are not without rhyme or reason. When an outbreak occurs, often it is because environmental conditions such as rainfall, temperatures, and vegetation set the stage for a population surge in disease-carrying pests. Mosquitoes or mice or ticks thrive, and the diseases they carry spread rapidly.

So why not watch these environmental factors and warn when conditions are ripe for an outbreak? Scientists have been tantalized by this possibility ever since the idea was first expressed by the Russian epidemiologist E. N. Pavlovsky in the 1960s. Now technology and scientific know-how are catching up with the idea, and a region-wide early warning system for disease outbreaks appears to be within reach.

Ronald Welch of NASA’s Global Hydrology and Climate Center in Huntsville, Alabama, is one of the scientists working to develop such an early warning system. “I have been to malarious areas in both Guatemala and India,” he says. “Usually I am struck by the poverty in these areas, at a level rarely seen in the United States. The people are warm and friendly, and they are appreciative, knowing that we are there to help. It feels very good to know that you are contributing to the relief of sickness and preventing death, especially the children.”

The approach employed by Welch and others combines data from high-tech environmental satellites with old-fashioned, “khaki shorts and dusty boots” fieldwork. Scientists actually seek out and visit places with disease outbreaks. Then they scrutinize satellite images to learn how disease-friendly conditions look from space. The satellites can then watch for those conditions over an entire region, country, or even continent as they silently slide across the sky once a day, every day.

In India, for example, where Welch is doing research, health officials are talking about setting up a satellite-based malaria early warning system for the whole country. In coordination with mathematician Jia Li of the University of Alabama at Huntsville and India’s Malaria Research Center, Welch is hoping to do a pilot study in Mewat, a predominantly rural area of India south of New Delhi. The area is home to more than 700,000 people living in 491 villages and 5 towns, yet is only about two-thirds the size of Rhode Island.

“We expect to be able to give warnings of high disease risk for a given village or area up to a month in advance,” Welch says. “These ‘red flags’ will let health officials focus their vaccination programs, mosquito spraying, and other disease-fighting efforts in the areas that need them most, perhaps preventing an outbreak before it happens.”

Outbreaks are caused by a bewildering variety of factors.

For the mosquito species that carries malaria in Welch’s study area, for example, an outbreak hotspot would have pools of stagnant water where adult mosquitoes can deposit their eggs to mature into new adults. These could be lingering puddles on dense, clay-like soil after heavy rains, swamplands located nearby, or even rain-filled buckets habitually left outside by villagers. A malaria hotspot would be warmer than 18?C, because in colder weather, the single-celled “plasmodium” parasite that actually causes malaria operates too slowly to go through its infection cycle before the host mosquito dies. But the weather mustn’t be too hot, or the mosquitoes would have to hide in the shade. The humidity must hover in the 55% to 75% range that these mosquitoes require for survival. Preferably there would be cattle or other livestock within the mosquitoes’ 1 km flight range, because these pests actually prefer to feed on the blood of animals.

If all of these conditions coincide, watch out!

Documenting some of these factors, such as soil type and local bucket-leaving habits, requires initial groundwork by researchers in the field, Welch notes. This information is plugged into a computerized mapping system called a Geographical Information Systems database (GIS). Fieldwork is also required to characterize how the local species of mosquito behaves. Does it bite people indoors or outdoors or both? Other factors, like the locations of cattle pastures and human dwellings, are inputted into the GIS map based on ultra-high resolution satellite images from commercial satellites like Ikonos and QuickBird, which can spot objects on the ground as small as 80 cm across. Then region-wide variables like temperature, rainfall, vegetation types, and soil moisture are derived from medium-resolution satellite data, such as from Landsat 7 or the MODIS sensor on NASA’s Terra satellite. (MODIS stands for MODerate-resolution Imaging Spectrometer.)

Scientists feed all of this information into a computer simulation that runs on top of a digital map of the landscape. Sophisticated mathematical algorithms chew on all these factors and spit out an estimate of outbreak risk.

The basic soundness of this approach for estimating disease risk has been borne out by previous studies. A group from the University of Nevada and the Desert Research Institute were able to “predict” historical rates of deer-mouse infection by the Sin Nombre virus with up to 80% accuracy, based only on vegetation type and density, elevation and slope of the land, and hydrologic features, all derived from satellite data and GIS maps. A joint NASA Ames / University of California at Davis study achieved a 90% success rate in identifying which rice fields in central California would breed large numbers of mosquitoes and which would breed fewer, based on Landsat data. Another Ames project predicted 79% of the high-mosquito villages in the Chiapas region of Mexico based on landscape features seen in satellite images.

Perfect predictions will likely never be possible. Like weather, the phenomenon of human disease is too complicated. But these encouraging results suggest that reasonably accurate risk estimates can be achieved by combining old-fashioned fieldwork with the newest in satellite technologies.

“All of the necessary pieces of the puzzle are there,” Welch says, offering the hope that soon disease outbreaks that seem to come “from out of nowhere” will catch people off guard much less often.

Original Source: NASA Science Story

Posted on by Fraser Cain

Astronomers Find a Second Pluto

Image credit: NASA/JPL
NASA-funded researchers have discovered the most distant object orbiting Earth’s Sun. The object is a mysterious planet-like body three times farther from Earth than Pluto.

“The Sun appears so small from that distance that you could completely block it out with the head of a pin,” said Dr. Mike Brown, California Institute of Technology, Pasadena, Calif., associate professor of planetary astronomy and leader of the research team. The object, called “Sedna” for the Inuit goddess of the ocean, is 13 billion kilometers (8 billion miles) away, in the farthest reaches of the solar system.

This is likely the first detection of the long-hypothesized “Oort cloud,” a faraway repository of small icy bodies that supplies the comets that streak by Earth. Other notable features of Sedna include its size and reddish color. After Mars, it is the second reddest object in the solar system. It is estimated Sedna is approximately three-fourths the size of Pluto. Sedna is likely the largest object found in the solar system since Pluto was discovered in 1930.

Brown, along with Drs. Chad Trujillo of the Gemini Observatory, Hawaii, and David Rabinowitz of Yale University, New Haven, Conn., found the planet-like object, or planetoid, on Nov. 14, 2003. The researchers used the 48-inch Samuel Oschin Telescope at Caltech’s Palomar Observatory near San Diego. Within days, telescopes in Chile, Spain, Arizona and Hawaii observed the object. NASA’s new Spitzer Space Telescope also looked for it.

Sedna is extremely far from the Sun, in the coldest know region of our solar system, where temperatures never rise above minus 240 degrees Celsius (minus 400 degrees Fahrenheit). The planetoid is usually even colder, because it approaches the Sun only briefly during its 10,500-year solar orbit. At its most distant, Sedna is 130 billion kilometers (84 billion miles) from the Sun, which is 900 times Earth’s solar distance.

Scientists used the fact that even the Spitzer telescope was unable to detect the heat of the extremely distant, cold object to determine it must be less than 1,700 kilometers (about 1,000 miles) in diameter, which is smaller than Pluto. By combining available data, Brown estimated Sedna’s size at about halfway between Pluto and Quaoar, the planetoid discovered by the same team in 2002.

The elliptical orbit of Sedna is unlike anything previously seen by astronomers. However, it resembles that of objects predicted to lie in the hypothetical Oort cloud. The cloud is thought to explain the existence of certain comets. It is believed to surround the Sun and extend outward halfway to the star closest to the Sun. But Sedna is 10 times closer than the predicted distance of the Oort cloud. Brown said this “inner Oort cloud” may have been formed by gravity from a rogue star near the Sun in the solar system’s early days.

“The star would have been close enough to be brighter than the full moon, and it would have been visible in the daytime sky for 20,000 years,” Brown explained. Worse, it would have dislodged comets farther out in the Oort cloud, leading to an intense comet shower that could have wiped out some or all forms of life that existed on Earth at the time.

Rabinowitz said there is indirect evidence that Sedna may have a moon. The researchers hope to check this possibility with NASA’s Hubble Space Telescope. Trujillo has begun to examine the object’s surface with one of the world’s largest optical/infrared telescopes, the 8-meter (26-foot) Frederick C. Gillett Gemini Telescope on Mauna Kea, Hawaii. “We still don’t understand what is on the surface of this body. It is nothing like what we would have predicted or what we can explain,” he said.

Sedna will become closer and brighter over the next 72 years, before it begins its 10,500-year trip to the far reaches of the solar system. “The last time Sedna was this close to the Sun, Earth was just coming out of the last ice age. The next time it comes back, the world might again be a completely different place,” Brown said.

NASA’s Jet Propulsion Laboratory, Pasadena, Calif, manages the Spitzer Space Telescope. For more information about the research and images on the Internet, visit http://www.spitzer.caltech.edu/Media/releases/ssc2004-05. For information about NASA on the Internet, visit http://www.nasa.gov.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Background on the Rover Airbag System

Image credit: NASA/JPL
Here I was: 26 years old, I had never worked on a flight project before, and all eyes were on me. Every time I walked by the Pathfinder project office, Tony Spear, the project manager, would throw his arm around me and announce, “Hey everybody, the whole mission is riding on this guy right here.”

Our task was to design and build airbags for Pathfinder’s landing on Mars an approach that had never been used on any mission. Airbags may seem like a simple, low-tech product, but it was eye-opening to discover just how little we knew about them. We knew that the only way to find out what we needed to learn was to build prototypes and test them. We just didn’t know how ignorant we were going to be.

Airbags seemed like a crazy idea to a lot of people. Nobody ever said that, mind you, but there seemed to be a widespread feeling that the airbags weren’t going to work. “We’ll let you guys go off and fool around until you fall flat on your faces.” That was the unspoken message I received day after day.

Everyone’s main fear about using these giant airbags was that the lander would be buried in an ocean of fabric when the airbags deflated. I began the search for a solution by building scale models of the airbags and lander, and I played with them in my office for a couple of months.

I built the models out of cardboard and plastic, and taped them up with packing tape I got from the hardware store and ribbon from the fabric store. I used a small raft inflator that I had at home to pump up my model airbags. Over and over again, I filled the miniature airbags and then let them deflate, watching what happened.

I fooled around with a dozen or more approaches before I finally came up with something that I thought worked. Slowly but surely, I came up with the idea of using cords that zigzag through belt loops inside the airbags. Pull the cords a certain way, and the cords would draw in all of the fabric and contain it. Wait to open the lander until after all of the airbags had retracted, and the fabric would be tucked neatly underneath.

Testing on another scale
Once we built large-scale models to conduct drop tests, we started by doing simple vertical drops, first at 30 feet, and then up to 70 feet. The bags performed well, although the way they bounced like a giant ball was interesting to observe. People began to realize that the concept might just be reasonably sound. But we still had our doubters. Even after we had the mechanics figured out for the airbags, a big question remained: What about the rocky Martian terrain?

Landing on Mars, we had to accept whatever Mother Nature gave us. The Pathfinder wouldn’t have a landing strip. To simulate conditions on Mars, we brought in large lava rocks the size of a small office desk. They were real lava rocks that our geologists had gone out and picked; if you tried to handle one of them, you would cut up your hands.

The more landscape simulations we tested, the more we started tearing up the airbags. Things were not looking good. Once again, we realized that this was an area that we just didn’t understand. The challenge was to protect the bladder layer, essentially the inner tube of the airbag system, with as little fabric as possible because the project could not afford to just throw mass at the problem. We tried material after material heavy duty Kevlars and Vectrans among them applying them in dozens of different configurations to the outside of the airbag.

Ultimately, we knew that we could just throw on more and more material and come up with a reasonably performing airbag system, but the weight of that solution would have come at the expense of something else another component of Pathfinder would have to be sacrificed. We weren’t, however, going to Mars just to land there and take a few pictures. We wanted to go there and do science and we needed instruments to do that science. So there was a lot of motivation to come up with the lowest-mass, highest-performance airbag system that we could.

5, 4, 3, 2, 1
Each test became like a ritual, because it took between eight and ten hours to prepare the system including transporting the airbags into the vacuum chamber, getting all of the instrumentation wired up, raising the airbags up to the top of the chamber, making sure all the rocks were in the right place, and preparing the nets.

The vacuum chamber where we did the drop tests used so much power that we were only able to test in the middle of the night. Once the doors of the vacuum chamber were closed, it took three or four hours just to pump down the chamber. At that point, everybody either broke for dinner or went to relax for a while, before coming back at midnight or whatever the appointed hour was. Then we had another 45 minutes of going over all of the instrumentation, going through checklists, and then ultimately the countdown.

The last 30 seconds of the countdown were excruciating. All of that anticipation, and then the whole impact lasted less than one second.

When we finished a drop test, we knew right away whether it was a success or failure. Brian Muirhead, the flight systems manager, was always insistent that I call him immediately-no matter how late it was. At 4 a.m., I would call him at his home and have to give him the news, “Brian, we failed another test.”

Each test was followed by a high-pressure rush to figure out what went wrong, what test to run next, how to fix the extensively damaged bags, and how to simultaneously incorporate whatever new “experimental fix” we came up with. As a team, we agreed upon a course of action, usually in a surly, sleep-deprived mood over a greasy breakfast at a local diner. Then the ILC Dover folks would figure out any new patterns that needed to be generated as well as the detailed engineering to ensure the seams and stitch designs could handle the test loads. Our hero was our lead sewer, who incidentally sewed Neil Armstrong and Buz Aldren’s moon suits. She worked under less-than-ideal conditions while we slept and turned our sometimes unusual ideas into reality. Usually by the next day we were ready to do it all over again.

Tony Spear and Brian understood the challenges we were facing. They knew we had a solid team working on this, and I always kept them informed on the technical progress. They were always understanding, but that’s not to say they were always happy.

Back to the drawing board
We said, “Okay, let’s start doing analysis, computer modeling of the airbags and the impact against the rocks.” At the same time, we expanded our test program to understand how to optimize this airbag abrasion layer.

It turned out that the time, money, and effort we expended on the computer modeling didn’t pay off. Though we ran the most sophisticated programs available back in 1993 and 1994, the results didn’t help us design the abrasion layer. We had to rely on our prototypes.

After doing dozens of drop tests, looking at the data, and studying what was happening, we started to realize that a single layer of heavy material wasn’t the solution. Multiple layers of lightweight material might prove stronger.

We were forced to decide on the final abrasion layer design in order to meet our scheduled Qualification drop tests. In spacecraft terms, this is supposed to be the last test that you run in order to qualify your final design. By the time you get to that point, there is supposed to be no question whatsoever that you have a fully functioning system that meets all of the mission requirements. It is supposed to be a check-the-box process that the system is ready for flight. The problem was that at that point we had still only experienced partial success; we’d never had that A+, 100% grade on any of our drop tests.

Flying in to watch that last drop test, my plane was delayed. One of my colleagues at the test facility called and asked me, “Do you want us to wait for you?” I told him, “No, go ahead.”

When I got to the facility, the test crew wasn’t there. I went into the control room and ran into the guy who processes the videotapes. “So what happened?” I asked him. “Did you guys do the test?” He pointed at a VCR and said, “The video is in there. Just go ahead and press play.”

So, I hit play. Down comes the airbag in the video it hits the platform and explodes catastrophically. My heart sank. We weren’t going to make it. But then I realized that there was something strangely familiar about the video I had just watched. In an instant it came to me; they had put in the videotape from our worst drop test. The practical joke could mean only one thing: We had had a successful drop test, and were finally good to go.

Original Source: NASA/JPL Story

Posted on by Fraser Cain

Atlas III Launches MBSAT Satellite

Image credit: ILS
An International Launch Services (ILS) Atlas III rocket blasted off early this morning, successfully orbiting the MBSAT satellite for Space Systems/Loral (SS/L). This was the 70th consecutive successful flight of an Atlas vehicle, and the second launch of the year conducted by ILS, a Lockheed Martin (NYSE: LMT) joint venture.

Liftoff was at 12:40 a.m. EST, and the SS/L 1300 model satellite separated from the rocket 29 minutes later. SS/L built the satellite and contracted with ILS to deliver it in orbit for Mobile Broadcasting Corp (MBCO) of Japan and SK Telecom of Korea. The state-of-the-art satellite will deliver digital multimedia information services such as CD-quality audio, MPEG-4 video and data to mobile users throughout Japan and Korea.

?This is a landmark launch for the Atlas team,? said ILS President Mark Albrecht. ?The Atlas rocket has a perfect record over more than a decade, but we?ll never get complacent. We still take it one launch at a time, and that discipline and dedication is what has given us the world?s most reliable vehicle.?

This was the fifth flight for the Atlas III vehicle, is one of three Atlas models currently being flown. It is a transitional vehicle between the Atlas II series that has been flying since 1991, and the powerful Atlas V, which made its debut successfully in 2002. The Atlas II, III and V families have achieved 100 percent success since mid-1993.

Albrecht noted that this is the 21st SS/L-built satellite launched by ILS vehicles, which include not only the Atlas family but also the Russian-built Proton rocket. ILS is a joint venture of Lockheed Martin, which builds the Atlas rocket, and Khrunichev State Research and Production Space Center, which builds the Proton vehicles. ILS, based in McLean, Va., markets and manages all missions for Atlas and commercial missions on Proton. ILS offers the broadest range of launch services in the world along with products with the highest reliability in the industry.

Original Source: ILS News Release

Posted on by Fraser Cain

Help Support Universe Today

I’ve had several generous offers from readers wondering how they could donate money to help me maintain Universe Today; which, as you know is pretty much a labour of love. I’ve felt a little uncomfortable about the idea, but a few of you have been very persistent. 🙂

So, I’ve gone ahead and set up with Paypal so you can donate money to Universe Today. If you feel that this website and newsletter are of value to you, and you want to contribute, just click this link which will take you to a form where you can donate money with your credit card. Universe Today has always, and will always be free. This is totally voluntary, and I leave it up to you to contribute only if it’s something you want to do. Knowing me, I’ll probably just use additional funds to hire some additional writers.

Thanks for all your support and kindness, I really appreciate it.

Fraser Cain
Publisher
Universe Today

P.S. People have also been wanting updated pictures of Chloe and Logan. Here’s Chloe with her favorite alien brainsucker hat.

Posted on by Fraser Cain

Cassini Sees Clumps in Saturn’s Rings

Image credit: NASA/JPL
Clumps seemingly embedded within Saturn’s narrow, outermost F ring can be seen in these two Cassini narrow angle camera images taken on Feb. 23, 2004 from a distance of 62.9 million kilometers (39 million miles). The images were taken nearly two hours apart using the camera’s broadband green filter, centered at 568 nanometers. Image scale is 377 kilometers (234 miles) per pixel.

The core of the F ring is about 50 kilometers (31 miles) wide, and from Cassini’s current distance, is not fully resolvable. Contrast has been greatly enhanced, and the images have been magnified, to aid visibility of the F Ring and the clump features.

The images show clumps as they revolve about the planet. Like all particles in Saturn’s ring system, these features orbit the planet in the same direction in which the planet rotates. This direction is clockwise as seen from Cassini’s southern vantage point below the ring plane. Two clumps in particular, one of them extended, can be seen in the upper part of the F ring in the image on the left, and in the lower part of the ring in the image on the right. Other knot-like irregularities in the ring’s brightness can also be seen in the right hand image.

Clumps such as these were first seen when the two Voyager spacecraft flew past Saturn in 1980 and 1981. It is not certain what causes these features, though several theories have been proposed, including meteoroid bombardment and inter-particle collisions in the F ring.

The Voyager data suggest that while the clumps change very little and can be tracked as they orbit for 30 days or more, no identified clump survived from the Voyager 1 flyby to the Voyager 2 flyby nine months later. Thus, scientists have only a rough idea of the lifetime of clumps in Saturn’s rings – a mystery that Cassini may help to answer.

The small dot at center right in the second image is one of Saturn’s small moons, Janus (181 kilometers, 112 miles across). Janus was discovered by ground-based astronomers in 1966, and was first resolved by the Voyager 1 spacecraft in 1980. The moon shares almost the same orbit with another small satellite, Epimetheus. Janus and Epimetheus, both thought to consist mostly of porous ices, play a role in maintaining the outer edge of Saturn’s A ring.

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 Office of Space Science, Washington, D.C. The imaging team is based at the Space Science Institute, Boulder, Colorado.

For information about the Cassini-Huygens mission, http://saturn.jpl.nasa.gov and the Cassini imaging team home page, http://ciclops.org.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Spirit Sees the Earth

Image credit: NASA/JPL
Consistently highly rated among those memorable ‘money-shots’ from the current Mars’ surface exploration is a view looking back towards the Earth. On Thursday, the Spirit rover team released the banner image showing the Earth as a tiny gray dot in the martian sky near the horizon.

The history of such views backwards towards the home planet, Terra Firma, have captivated the imagination for a generation of astronomers. This glimpse from the surface of another planet offers an unrivalled perspective that stretches beyond just seeing our home as one of many planets, or the only pale blue dot in our solar system.

As Carl Sagan’s widow, Anne Druyan , described this perspective image to Astrobiology Magazine, such earth views make “us look at this tiny planet, at the pale blue dot, and to see it in its real context, in its actual circumstances, in its true tininess. I don’t know anyone who’s able to really see that one-pixel Earth and not feel like they want to protect the Earth; that we have much more in common with each other than we’re likely to have with anyone anywhere else.”

The evocative phrase describing the Earth as a ‘pale blue dot’ was coined by Carl Sagan after seeing our planet as a single pixel. The view was taken from the departing Voyager spacecraft. The entire earth could be encompassed as a flicker of light. The first image of Earth ever taken from another planet that actually shows our home as a planetary disk was captured by the Mars Orbital Camera on May 8th.

One question that might be answerable from such a world-view is could a scientist on Mars identify from such a perspective that the Earth harbored life. In 1993, a team of researchers inspired by Carl Sagan, used an Earth fly-by of the Galileo spacecraft on its way to Jupiter to catch a glimpse of how the Earth might appear from afar. For astrobiologists, Sagan’s results were surprising.

Rather than seeing the Earth as an obvious candidate for life, the Galileo pictures gave surprisingly few clues of the biological potential of our own planet.

From afar, how Galileo missed the obvious signs of terrestrial life as we would have expected to see them, was at first disconcerting to the scientific community, because future missions aim to observe more distant extrasolar planets and detect what would be visible in the spectra–the ‘pale blue dot’ scenario.

One answer may lie in the fact that the spacecraft made its observations while still quite close to the Earth.

“The spectrograph was designed to look at small areas of Jupiter, so the field of view of the spectrograph was quite small,” said Nick Woolf of Arizona, in earlier discussions with the Astrobiology Magazine.

“Also, since the surface brightness of Jupiter [the Gaileo’s intended visual target] is far less than the Earth, the spectrograph detectors saturated except when the spectrograph was pointed at the darkest area of Earth – a cloud-free section of sea,” Woolf noted. The cloud-free sea is considered very dark relative to the dominance of bright clouds in a global picture of Earth. Thus it should come as no surprise that Galileo was successful in only imaging a relatively dark and lifeless planet, mainly because its design was not intended to look at Earth, but to probe Jupiter instead.

A spectroscope that might detect infrared or visible light looking back on Earth or outwards to other planets might focus mainly on four gases that are found in Earth’s atmosphere and linked to life:

* Water vapor A baseline sign, indicating the presence of liquid water, a requirement of known life.
* Carbon dioxide Can be created by biological and non-biological processes. Because it is necessary for photosynthesis, it would indicate the possible presence of green plants.
* Methane Considered suggestive of life, it also can be made both by biological and non-biological processes.
* Molecular oxygen (O2) – or its proxy, ozone (O3). The most reliable indicator of the presence of life, but still not conclusive.

Unless molecular oxygen in the atmosphere is constantly replenished by photosynthesis, it is quickly consumed in chemical reactions, in the atmosphere, on land and in seawater. So the presence of a large amount of oxygen in an extrasolar planet’s atmosphere would be a sign that it might host an ecosystem like present-day Earth’s.

An additional oxygen-related biosignature is the possibility of detecting green plants that make oxygen. Chlorophyll reflects near-infrared light very strongly, a phenomenon known as the “red edge” because the light is just beyond the range of colors human eyes can see. (If humans could see the red edge, plants would look red instead of green.) Near-infrared cameras would have no trouble picking up this distinctive signal.

Not only are earth-views aesthetically interesting, while offering a chance to test remote sensing scenarios, the rovers more practically depend on a daily sky view to navigate. The rover design does not possess any intrinsic way of knowing its orientation as north or south for instance, because Mars doesn’t offer a strong magnetic field that might typically give a compass reading. So scientists point the rover’s mobile panoramic camera to do a sun sighting daily, which also provides today’s orientation. Navigating by stars on Mars is also possible although the rovers’ solar power arrays typically are put into electronic sleep-modes at night to conserve power.

Spirit imaged stars on March 11, 2004, after it awoke during the martian night for a communication session with NASA’s Mars Global Surveyor orbiter. This image is an eight-second exposure. Longer exposures were also taken. The images tested the capabilities of the rover for night-sky observations. Scientists will use the results to aid planning for possible future astronomical observations from Mars.

Original Source: NASA Astrobiology Magazine

Posted on by Fraser Cain

Santa Ana Winds Stimulate Marine Environment

Image credit: NASA/JPL
Southern California’s legendary Santa Ana winds wreak havoc every year, creating hot, dry conditions and fire hazards. Despite their often-destructive nature, a study of the “Devil Winds,” conducted using data from NASA’s Quick Scatterometer (Quikscat) spacecraft and its SeaWinds instrument shows the winds have some positive benefits.

“These strong winds, which blow from the land out into the ocean, cause cold water to rise from the bottom of the ocean to the top, bringing with it many nutrients that ultimately benefit local fisheries,” said Dr. Timothy Liu, a senior research scientist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., and Quikscat project scientist. Santa Ana consequences include vortices of cold water and high concentrations of chlorophyll 400 to 1,000 kilometers (248 to 621 miles) offshore.

Liu and Dr. Hua Hu of the California Institute of Technology, Pasadena, in a paper published last year in Geophysical Research Letters, revealed satellite observations of the Santa Ana effects on the ocean during three windy days in February 2003. According to the findings, Quikscat was able to identify the fine features of the coastal Santa Ana wind jets. It identified location, strength and extent, which other weather prediction products lack the resolution to consistently show, and moored ocean buoys lack sufficient coverage to fully represent.

Quikscat’s high-resolution images of air-sea interaction were used to measure wind forces on the ocean. Other satellites and instruments, like the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and the Advanced Very High Resolution Radiometer, onboard a National Oceanic and Atmospheric Administration polar orbiting weather satellite, were used to measure the temperature and biological production of the ocean surface, which respond to the wind.

The latter instrument showed sea surface temperatures dropped four degrees Celsius (seven degrees Fahrenheit) during the February 2003 Santa Anas. That was a sign that upwelling had occurred, meaning, deep cold water moved up to the ocean surface bringing nutrients. Images from SeaWiFS confirmed the increased biological productivity by measuring chlorophyll concentrations in the surface water. It went from negligible, in the absence of winds, to very active biological activity (more than 1.5 milligrams per cubic meter) in the presence of the winds.

“There really is no other system that can monitor Santa Ana winds over the entire oceanic region,” Liu said. “Scatterometers such as Quikscat have a large enough field of view and high enough resolution to easily identify the details of coastal winds, which can affect the transportation, ecology and economy of Southern California.”

High pressure develops inland when cold air is trapped over the mountains, driving the dry, hot and dusty Santa Anas (also called Santanas and Devil’s Breath) at high speeds toward the coast. The winds, occurring in fall, winter and spring, can reach 113 kilometers (70 miles) per hour. They happen at any time of day and usually reach peak strength in December. Telltale signs on the coast include good visibility inland, unusually low humidity and an approaching dark brown dust cloud.

The Quikscat satellite, launched in June 1999, operates in a Sun- synchronous, 800-kilometer (497-mile) near-polar orbit. It circles Earth every 100 minutes and takes approximately 400,000 daily measurements over 93 percent of the planet’s surface. It passes over Southern California about twice a day, skipping a day every three or four days.

Quikscat is part of an integrated Earth observation system managed by NASA’s Office of Earth Science. The NASA enterprise is dedicated to understanding the Earth as an integrated system and applying Earth System Science to improve prediction of climate, weather, and natural hazards using the unique vantage point of space.

For information about NASA programs on the Internet, visit:

http://www.nasa.gov.

For information about Quikscat and SeaWinds on the Internet, visit:

http://winds.jpl.nasa.gov.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Spirit at the Edge of Bonneville Crater

Image credit: NASA/JPL
NASA’s Spirit has begun looking down into a crater it has been approaching for several weeks, providing a view of what’s below the surrounding surface.

Spirit has also been looking up, seeing stars and the first observation of Earth from the surface of another planet. Its twin, Opportunity, has shown scientists a “mother lode” of hematite now considered a target for close-up investigation.

“It’s been an extremely exciting and productive week for both of the rovers,” said Spirit Mission Manager Jennifer Trosper at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

Dr. Chris Leger, a rover driver at JPL, said, “The terrain has been getting trickier and trickier as we’ve gotten close to the crater. The slopes have been getting steeper and we have more rocks.” Spirit has now traveled a total of 335 meters (1,099 feet).

Spirit’s new position on the rim of the crater nicknamed “Bonneville” offers a vista in all directions, including the crater interior. The distance to the opposite rim is about the length of two football fields, nearly 10 times the diameter of Opportunity’s landing-site crater halfway around the planet from Spirit.

Initial images from Spirit’s navigation camera do not reveal any obvious layers in “Bonneville’s” inner wall, but they do show tantalizing clues of rock features high on the far side, science-team member Dr. Matt Golombek of JPL said at a news briefing today. “This place where we’ve just arrived has opened up, and it’s going to take us a few days to get our arms around it.?

Scientists anticipate soon learning more about the crater from Spirit’s higher-resolution panoramic camera and the miniature thermal emission spectrometer, both of which can identify minerals from a distance. They will use that information for deciding whether to send Spirit down into the crater.

From the crater rim and during martian nighttime earlier today, Spirit took pictures of stars, including a portion of the constellation Orion. Shortly before dawn four martian days earlier, it photographed Earth as a speck of light in the morning twilight. The tests of rover capabilities for astronomical observations will be used in planning possible studies of Mars’ atmospheric characteristics at night. Those studies might include estimating the amounts of dust and ice particles in the atmosphere from their effects on starlight, said Dr. Mark Lemmon, a science team member from Texas A&M University, College Station.

Opportunity has been looking up, too. It has photographed Mars’ larger moon, Phobos, passing in front of the Sun twice in the past week, and Mars’ smaller moon, Deimos, doing so once.

Opportunity’s miniature thermal emission spectrometer has taken upward-looking readings of the atmospheric temperature at the same time as a similar instrument, the thermal emission spectrometer on NASA’s Mars Global Surveyor orbiter, took downward-pointed readings while passing overhead. “They were actually looking directly along the same path,” said science team member Dr. Michael Wolff of the Martinez, Ga., branch of the Space Science Institute, Boulder, Colo. The combined readings give the first full temperature profile from the top of Mars’ atmosphere to the surface.?

When pointed at the ground, Opportunity’s miniature thermal emission spectrometer has checked the abundance of hematite in all directions from the rover’s location inside its landing-site crater. This mineral, in its coarse-grained form, usually forms in a wet environment. Detection of hematite from orbit was the prime factor in selection of the Meridiani Planum region for Opportunity’s landing site.

“The plains outside our crater are covered with hematite,” said Dr. Phil Christensen of Arizona State University, Tempe, lead scientist for the instrument. “The rock outcrop we’ve been studying has some hematite. Parts of the floor of the crater, interestingly enough, have virtually none.” The pattern fits a theory that the crater was dug by an impact that punched through a hematite-rich surface layer, he said. One goal for Opportunity’s future work is to learn more about that surface layer to get more clues about the wet past environment indicated by sulfate minerals identified last week in the crater’s outcrop.

Christensen said that before Opportunity drives out of the crater in about 10 days, scientists plan to investigate one area on the inner slope of the crater that he called “the mother lode of hematite.”

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA’s Office of Space Science, Washington, D.C. Images and additional information about the project are available from JPL at http://marsrovers.jpl.nasa.gov and from Cornell University at http://athena.cornell.edu.

Original Source: NASA/JPL News Release