Posted on by Fraser Cain

Planets Could Be Common Around Brown Dwarfs

Artist illustration of microscopic crystals surrounding a dusty disk. Image credit: NASA/JPL. Click to enlarge.
NASA’s Spitzer Space Telescope has spotted the very beginnings of what might become planets around the puniest of celestial orbs – brown dwarfs, or “failed stars.”

The telescope’s infrared eyes have for the first time detected clumps of microscopic dust grains and tiny crystals orbiting five brown dwarfs. These clumps and crystals are thought to collide and further lump together to eventually make planets. Similar materials are seen in planet-forming regions around stars and in comets, the remnants of our own solar system’s construction.

The findings provide evidence that brown dwarfs, despite being colder and dimmer than stars, undergo the same initial steps of the planet-building process.

“We are learning that the first stages of planet formation are more robust than previously believed,” said Dr. Daniel Apai, an astronomer at the University of Arizona, Tucson, and member of the NASA Astrobiology Institute’s Life and Planets Astrobiology Center. “Spitzer has given us the possibility to study how planets are built in widely different environments.”

The observations also imply that brown dwarfs might be good targets for future planet-hunting missions. Astronomers do not know if life could exist on planets around brown dwarfs.

Brown dwarfs differ from stars largely due to their mass. They lack the mass to ignite internally and shine brightly. However, they are believed to arise like stars, out of thick clouds of gas and dust that collapse under their own weight. And like stars, brown dwarfs develop disks of gas and dust that circle around them. Spitzer has observed many of these disks, which glow at infrared wavelengths.

Apai and his team used Spitzer to collect detailed information on the minerals that make up the dust disks of six young brown dwarfs located 520 light-years away, in the Chamaeleon constellation. The six objects range in mass from about 40 to 70 times that of Jupiter, and they are roughly 1 to 3 million years old.

The astronomers discovered that five of the six disks contain dust particles that have crystallized and are sticking together in what may be the early phases of planet assembling. They found relatively large grains and many small crystals of a mineral called olivine.

“We are seeing processed particles that are linking up and growing in size,” said Dr. Ilaria Pascucci, a co-author also of the University of Arizona. “This is exciting because we weren’t sure if the disks of such cool objects would behave the same way that stellar disks do.”

The team also noticed a flattening of the brown dwarfs’ disks, which is another sign that dust is gathering up into planets.

A paper on these findings appears online today in Science. Authors of the paper also include Drs. Jeroen Bouwman, Thomas Henning and Cornelis P. Dullemond of the Max Planck Institute for Astronomy, Germany; and Dr. Antonella Natta of the Osservatorio Astrofisico di Arcetri, Italy.

NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer mission for NASA’s Science Mission Directorate. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Spitzer’s infrared spectrograph, which made the observations, was built by Cornell University, Ithaca, N.Y. Its development was led by Dr. Jim Houck of Cornell. The NASA Astrobiology Institute, founded in 1997, is a partnership between NASA, 16 major U.S. teams and six international consortia.

For artist concepts, graphics and more information about Spitzer, visit http://www.spitzer.caltech.edu/spitzer/ . For more information about the NASA Astrobiology Institute, visit http://nai.arc.nasa.gov/ . For more information about NASA and agency programs on the Web, visit http://www.nasa.gov/home/ .

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Middle Latitude Clouds on Titan Are Familiar

Saturn’s Moon Titan. Image credit: NASA/JPL/SSI. Click to enlarge.
University of Arizona scientists say that the peculiar clouds at middle latitudes in Titan’s southern hemisphere may form in the same way as distinct bands of clouds form at Earth’s equator.

“Titan’s weather is very different from Earth’s,” said UA associate professor Caitlin Griffith. “If you walked past Titan’s minus-40-degree-latitude line, you might be showered with liquid natural gas. If you decided to visit Titan’s south pole, you might encounter a storm the size of a hurricane which also consists of methane, more commonly known as natural gas,” Griffith said. “Otherwise, don’t expect clouds on Titan.”

Titan’s weather forecast has remained the same for years, and that baffles scientists. They don’t understand why clouds a thousand miles long stretch over the temperate latitude.

“Imagine how curious it would be if beyond Earth’s poles, clouds existed only at the latitude that crosses New Zealand, Argentina and Chile,” Griffith said. “Furthermore, Henry Roe (of the California Institute of Technology) and his colleagues find that most of these peculiar clouds bunch up at zero degrees and 90 degrees longitude, analogous to Earth longitudes southwest and southeast of the Cape of Good Hope,” she added.

The highly localized nature of the clouds suggests that they have something to do with Titan’s surface, Griffith said. Scientists think ice volcanoes must be venting methane — the gas that condenses as clouds — into Titan’s hazy, mostly nitrogen atmosphere. Otherwise, the moon’s atmospheric methane would have vanished billions of years ago because methane is destroyed by ultraviolet sunlight.

Griffith, Paulo Penteado and Robert Kursinski of UA’s Lunar and Planetary Lab studied the origin of the clouds by analyzing cloud height and thickness using images from Cassini’s visual and infrared mapping spectrometer (VIMS). This instrument is among a suite of instruments on the Cassini spacecraft orbiting Saturn. It measures light at 256 different wavelenghts. Griffith is a member of the UA-based VIMS team, headed by Robert Brown of UA’s Lunar and Planetary Lab. Griffith and her colleagues analyzed images that gave them a 3-D view of the cloud and a six-frame movie that shows how it evolved over three hours.

“The structure of the clouds turns out to be complicated,” Griffith said. “We detected not one region, but many regions of cloud formation. Each long cloud consists of a number of vigorous storms where clouds rise to 40 kilometers altitude (25 miles) in a couple of hours and dissipate in the next half hour. The rate of cloud ascent and dissipation suggests that we are witnessing the formation of convective clouds, likely similar to thunderstorms, that disappear through rainfall.

“Over the next several hours we see the clouds form long tails, indicating that strong westerly winds stretch out the clouds and carry the particles downwind a thousand kilometers (more than 600 miles). This detailed look into the structure of these clouds reveals that the clouds evolve from a number of small active cloud formation centers lined up like an uneven string of beads long 40 degrees south latitude. These localized storms cause a healthy rain, and very long clouds, once the wind has stretched them out.”

Griffith argues that it’s improbable that many ice volcanoes, all aligned at 40 degrees south latitude, are forming these clouds. In addition, the scientists estimate that the cloud activity at zero degrees longitude, if volcanic, does not appear to spew out enough methane to create the mid-latitude cloud band. Smaller clouds actually lie upwind of the main cloud at zero degrees longitude, they note. The team also conclude that the clouds aren’t obviously caused by Saturn’s tidal pull on Titan’s atmosphere. They also don’t find evidence that mountains and lakes might cause mountain clouds or marine clouds, Griffith said.

“We believe that it’s no coincidence that Titan’s south polar cap of smog extends from the pole to 40 degrees south latitude — exactly where the methane cloud band appears,” Griffith said. The researchers suggest that global circulation may cause the air to rise at this latitutude on Titan, much as clouds form in a band around the Earth’s equator and rain on the Caribbean islands. “Such rising air would cut off air from the south polar region from mixing with the rest of the moon’s atmosphere, causing smog to build up and form a cap over the pole,” Griffith added.

Theoretical modeling supports the UA team’s conclusion, Griffith said. Pascal Ranou and his group in Paris studied Titan’s circulation with an elaborate and complicated general circulation model. His model predicts that solar heating naturally creates rising air on Titan at 40 degrees south latitude.

The next mystery is why Titan’s southern mid-latitude clouds are bunched at zero degrees longitude. There’s no evidence yet that volcanoes, mountain ranges or Saturn’s tides are involved, Griffith said. “What’s causing the bunching is unclear, and likely involves unknown features on Titan’s still largely unexplored surface,” Griffith said.

Griffith, Kursinki and Penteado are publishing an article on their research in the Oct. 21 issue of Science.

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, Calif., manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The Visual and Infrared Mapping Spectrometer team is based at The University of Arizona in Tucson.

Original Source: University of Arizona News Release

Posted on by Fraser Cain

Final Titan 4 Launches

Final Titan 4 lifting off. Image credit: Lockheed Martin. Click to enlarge.
The United States Air Force and Lockheed Martin (LMT:NYSE) closed out a proud five-decade history today with the final launch of a Titan IV B rocket carrying a critical national security payload for the National Reconnaissance Office (NRO). All eyes were on Space Launch Complex 4 East as the nation’s heavy-lift workhorse thundered off the pad to deliver its final payload to space and retire from service.

“Today’s spectacular launch is a fitting way to say goodbye to Titan,” said G. Thomas Marsh, executive vice president of Lockheed Martin Space Systems Company. “The Lockheed Martin employees who have given their utmost efforts to the program over the years join with our Air Force and NRO customers, and the many other organizations that make up the Titan team, in expressing our great pride in this service to our country’s space program.”

Today’s launch was the last launch for the Titan IV and the culmination of a long evolution from the original Titan I intercontinental ballistic missile. In all, 39 Titan IVs have been launched – 12 Titan IVs have been launched from Vandenberg Air Force Base on the West Coast plus 27 more from the Cape Canaveral Air Force Station, Fla. The final Titan IV mission from Cape Canaveral was launched successfully April 29, 2005.

Col. Michael T. Baker, director, Launch Programs, Space and Missile Systems Center, Air Force Space Command, said, “The members of the System Program Office are extremely proud to be part of this historic launch. I am particularly honored to lead this SPO since Titan has been a part of my career since 1981. We have been confident from the beginning that the Titan team would deliver one final mission success for the nation.”

Following the Space Shuttle Challenger tragedy in 1986, when assured access to space became critical for the U.S. government, the Titan IV was developed as the booster used to launch the nation’s largest, heaviest and most critical payloads. Titan initial IV A design was followed by Titan IV B with a new generation of large solid rocket motors, state-of-the-art guidance and electronics and a new ground processing system.

“Today’s launch marks the end of an NRO Titan era but the beginning of the Titan Legend that will live on in the history of America’s space program,” said Col. Chip Zakrzewski, National Reconnaissance Office mission director.

Lockheed Martin Space Systems Company built the Titan IVs near Denver, Colo., under contract to the U.S. government. As prime contractor and systems integrator, the company built the first and second stages and provides overall program management and launch services. Other members of the Titan IV contractor team and their responsibilities include: GenCorp Aerojet Propulsion Division, Sacramento, Calif., liquid rocket engines; Alliant Techsystems, Magna, Utah, solid rocket motor upgrade; The Boeing Company, Huntington Beach, Calif., payload fairing; and Honeywell Space Systems, Clearwater, Fla., advanced guidance.

Original Source: Lockheed Martin News Release

Posted on by Fraser Cain

Hubble Gazes at the Moon

Hubble’s view of the Moon. Image credit: Hubble. Click to enlarge.
NASA is using the unique capabilities of the Hubble Space Telescope for a new class of scientific observations of the Earth’s moon.

Hubble’s resolution and sensitivity to ultraviolet light have allowed the telescope to search for important oxygen-bearing minerals on the moon. Since the moon does not have a breathable atmosphere, minerals, such as ilmenite (titanium and iron oxide), may be critical for a sustained human lunar presence. Ilmenite is a potential source of oxygen for breathing or to power rockets.

The new Hubble observations are the first high-resolution, ultraviolet images ever acquired of the moon. The images provide scientists with a new tool to study mineral variations within the lunar crust. As NASA plans future expeditions to the moon, such data, in combination with other measurements, will help ensure the most valuable sites are targeted for robotic and human missions.

“These observations of the moon have been a challenging and highly successful technological achievement for NASA and the Hubble team, since the telescope was not originally designed for lunar observations,” said Jennifer Wiseman, program scientist for the Hubble at NASA Headquarters. “The images will inform both scientific studies of lunar geology and future decisions on further lunar exploration,” she said.

Hubble’s Advanced Camera for Surveys snapped ultraviolet and visible light images of known geologically diverse areas on the side of the moon nearest Earth. These included the Aristarchus impact crater and the adjacent Schroter’s Valley. Hubble also photographed the Apollo 15 and 17 landing sites, where astronauts collected rock and soil samples in 1971 and 1972.

Scientists are comparing the properties of the rock and soil samples from the Apollo sites with the new Hubble images, and the Aristarchus region, which neither humans nor robotic spacecraft have visited. The Hubble observations of Aristarchus crater and Schroter’s Valley will help refine researchers’ understanding of the diverse, scientifically interesting materials in the region and to unravel their full resource potential.

“Our initial findings support the potential existence of some unique varieties of oxygen-rich glassy soils in both the Aristarchus and Apollo 17 regions. They could be well-suited for visits by robots and human explorers in efforts to learn how to live off the land on the moon,” said Jim Garvin, chief scientist at NASA’s Goddard Space Flight Center, Greenbelt, Md. Garvin is principal investigator for the project.

“While it will require many months before fully quantitative results can be developed, we already have evidence that these new observations will improve the precision by which we can understand materials such as ilmenite to help better inform exploration decisions,” Garvin said.

Hubble’s lunar observation analysis team included colleagues from Goddard and Cornell University, Ithaca, N.Y.; Brown University, Providence, R.I.; Northwestern University, Evanston, Ill.; the University of Pittsburgh.; and the University of Hawaii, Manoa.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. The Space Telescope Science Institute in Baltimore conducts Hubble science operations. It is operated for NASA by the Association of Universities for Research in Astronomy, Inc., Washington, under contract with Goddard.

Original Source: Hubble News Release

Posted on by Fraser Cain

Mars Will Be Closest on October 29/30

Mars on October 17?18, 2005, as recorded by Sky & Telescope assistant editor Sean Walker. Image credit: Sky and Telescope. Click to enlarge.
Look east late these evenings and you’ll see a big, fiery yellow “star” shining much brighter than any other. This is the planet Mars, and it’s passing unusually close to Earth during late October and early November 2005. Anyone can see it ? no matter how little you know about the stars or how badly light-polluted your sky may be.

During mid- to late October, look for Mars glaring low in the east after 8 p.m. local daylight-saving time. In November, it’s there in view as early as 6 p.m. standard time. Later in the evening, Mars climbs higher into better view and shifts over to the southeast. There’s nothing else nearly as bright that you can confuse it with.

Mars will be its closest to Earth on the night of October 29?30, passing 43.1 million miles (69.4 million kilometers) from our planet around 11:25 p.m. on the 29th Eastern Daylight Time. However, Mars will look just about as big and brilliant for a couple of weeks before and after that date.

Mars is at opposition (opposite the Sun in our sky) on November 7th. This means it rises at sunset, is up all night, and sets at sunrise.

This is the nearest that Mars has come since its record-breaking close approach in August 2003. At that time it passed by at a distance of only 34.7 million miles (55.8 million kilometers), the closest it had come in nearly 60,000 years. But for amateur telescope users, now is still a very special time. The planet will reach an apparent diameter of 20.2 arcseconds (the angular size of a penny seen at a distance of 620 feet), offering an usually detailed view of its surface. That compares with 25.1 arcseconds in August 2003 (the angular size of a penny at 500 feet), and only 15.9 arcseconds at Mars’s next swing-by, in December 2007 (a penny at 800 feet).

In fact, not until the summer of 2018 will Mars again come as close to Earth as it is right now (this statement remains true until mid-November).

Moreover, this year skywatchers at the latitudes of North America and Europe have a big advantage they didn’t have in 2003. That year Mars was far south in the sky and never got very high for telescope users at mid-northern latitudes. But this time Mars is farther north and rises higher during the night, affording a sharper, cleaner view in a telescope through Earth’s blurry atmosphere.

Telescope Tips
Good as this fall’s showing is, surface details on Mars are always a pretty tough target in a telescope. To begin with, Mars is only about half the size of Earth. Even at its closest, under high magnification it will appear as only a surprisingly small, bright ball with some subtle dark markings, possible white clouds around its edges, and perhaps a tiny remnant of the white South Polar Cap shrunken in the warmth of the Martian summer. The brightest yellow areas are deserts covered by fine, windblown dust. The darker markings are terrain displaying more areas of bare rock or darker sand and dust. Mars rotates every 24? hours, so you can see it turning in just an hour or two of watching.

To see much detail on Mars, several things all have to be working in your favor. You?ll need at least a moderately large telescope with high-quality optics. (For the lowdown on how to select a telescope wisely, see Sky & Telescope’s article “Choosing Your First Telescope”.) And you?ll need to wait until Mars rises high in the sky, well above the thick, murky layers of Earth’s atmosphere near the horizon. Moreover, the atmospheric “seeing” must be good. This is the astronomer?s term for the constant fuzzing and shimmering of highly magnified telescopic images due to the tiny heat waves that are always rippling through the atmosphere. The seeing changes from night to night and sometimes from moment to moment.

More about Mars and its unusual close approach appears in the September issue of Sky & Telescope and in the November/December 2005 issue of Night Sky, our new bimonthly magazine for beginners

Original Source: Sky and Telescope News Release

Posted on by Fraser Cain

Hurricane Wilma Becomes a Record Setting Cat 5

Satellite view of Hurricane Wilma. Image credit: NASA/NOAA. Click to enlarge.
In the early morning hours of Wednesday, October 19 in the warm Caribbean waters, Hurricane Wilma strengthened from a Category 2 hurricane to the most intense Hurricane 5 hurricane on record.

Hurricanes are measured by factors such as atmospheric pressure, winds and storm surge. Wilma’s atmospheric pressure at 8 a.m. EDT measured 882 millibars. The previous record was 888 millibars set in 1988 by Hurricane Gilbert that moved through the Gulf of Mexico.

At 8 a.m. Wednesday, October 19, Wilma was packing maximum sustained winds of 175 mph (280 km/hr) with higher gusts. Wilma’s center was located near latitude 17.2 north and longitude 82.8 west or about 340 miles (550 km) southeast of Cozumel, Mexico. Wilma is moving toward the west-northwest near 8 mph (13 km/hr). A turn toward the northwest is expected during the next 24 hours.

According to the National Hurricane Center, Wilma is a potentially catastrophic Category 5 hurricane on the Saffir-Simpson scale. Fluctuations in intensity are common in hurricanes this intense and are likely during the next 24 hours.

Wilma is a smaller storm than Katrina. Wilma’s hurricane force winds extend outward to 15 miles (30 km) from the center and tropical storm force winds extend outward up to 160 miles (260 km).

Based on data from dropsondes, instruments that are dropped into the storm from Hurricane Hunter planes that fly over it, and flight-level data from an Air Force plane, Wilma’s minimum central pressure is estimated to be 882 millibars (26.05 inches). This is the lowest pressure on record for a hurricane in the Atlantic basin.

Rainfall by Wilma is expected to be high. Wilma is expected to produce storm total accumulations of 10 to 15 inches with local amounts near 25 inches in mountainous terrain across Cuba through Friday. Additional rainfall accumulations of 5 to 10 inches, with local amounts of 15 inches, are possible across the Cayman Islands, Swan Island and Jamaica through Thursday.

From Honduras northward to the Yucatan peninsula of Mexico through Thursday, storm total accumulations of 4 to 6 inches, with isolated amounts of 8 to 12 inches are possible.

Watches and warnings have been posted throughout the region. A hurricane watch is in effect for the east coast of the Yucatan Peninsula from Cabo Catoche to Punta Gruesa. A hurricane watch is also in effect for Cuba in the provinces of Matanzas westward through Pinar del Rio and for the Isle of Youth. A hurricane watch means that hurricane conditions are possible within the watch area, generally within 36 hours.

Tropical storm warnings are up for Honduras from the Honduras/Nicaragua border westward to Cabo Camaron. A tropical storm warning and a hurricane watch remain in effect for the Cayman Islands.

Current forecast models project Wilma making landfall in southwest Florida on Saturday, Oct. 22 or Sunday, Oct. 23. All residents in the Florida Keys and the Florida peninsula should closely monitor the progress of extremely dangerous Hurricane Wilma. Story credit: Rob Gutro, NASA

Original Source: NASA News Release

Posted on by Mark Mortimer

Book Review: Mammoth Book of Space Exploration Disasters

Humans and high speed vehicles have been getting together for a long time. The need for added speed keeps us experimenting. From two horse chariots to four horse, or galleons to schooners, we keep finding ways of getting ourselves moving faster and further. Rocket power swiftly followed the advent of planes, giving us freedom from the grip of land. Then ballistic missiles sent us past the slight friction of our atmosphere and into the near complete emptiness of space. With every advent of new technology and speed, there were flaws and errors. A chariot wheel fractures and dumps the drivers onto the ground. This may lead to no more than a bruised ego. But, when a thin ring of rubber fails on a rocket, the results are much more disastrous. Sad as this may be, one of humanity’s common traits is a greater interest in failures than successes. Hence, though we have made many successful flights into space, it is the failures that interest most people, even a long time after the event and it is this trait that gets treated with this book.

To satisfy this interest, Richard Lawrence has compiled a collection of stories, narrations and articles. These cover the time from planes using rockets in 1953 to the launch of the Rosetta mission in 2004. There is Neville Duke an early air speed record holder who describes rocket flight. Chuck Yeager powers through a description of his first transition through the sound barrier. Buzz Aldrin depicts Apollo 11’s landing, while Lovell repaints his sojourn in Apollo 13. As well, Lawrence with Bryan Burrough, provide their own rendition of the time a Progress supply vessel crashes into the Mir space station. These and others in the collection bring back to life many of the most memorable crises of humans and rocketry.

In addition to the events themselves, the styles of the presentations show the maturation of the technology. The early stories usually refer to only one person who was fully integrated with the craft and often referred to it as an extension of themselves. Later narrations, in particular the very dry excerpts from the commission’s report on the Challenger and Columbia accidents, show the remote controlled nature of flight even to the associated communications. Exceptions do occur though as Jerry Linenger eloquently echos his feelings of almost uncontrollable terror while dangling in the void of space at the end of a boom extending from the Mir station.

In editing, Richard Lawrence chose an excellent collection of narrations covering humans and rocketry. By selecting first hand accounts, or very well placed second hand accounts, he continually places the reader directly at the event. He provides clarification by adding a few paragraphs before each selection to aid the reader in understanding the situation. Though these articles represent a quite superficial and somewhat negative view of humanity’s progress with rocketry, as indicated by the sensationalist title, still many youths might be pleasantly swayed by much of the emotional delivery. That is except for the very dry and bureaucratic style of the selections for the Challenger and Columbia accidents. Certainly there are other thoughtful, technically accurate and strongly emotional narrations for these.

For many good and bad reasons, people contentedly place themselves into perilous situations. Perhaps this is the nature of humanity, to offer your singular service for the greater good. In the book edited by Richard Russell Lawrence entitled Space Exploration and Disasters, there are many stories of people striving to do their best against some astounding challenges. And, as often seen, people were able to adapt, apply innovative thinking and respond successfully.

Review by Mark Mortimer

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

Posted on by Fraser Cain

Future Space Missions Will Explore at Many Levels

Spirit’s view of Mars. Image credit: NASA/JPL. Click to enlarge.
Remote-sensing orbiters, probes, landers and rovers are returning astonishing discoveries about our solar system. But some of the most exciting geological and potentially astrobiological places in our family of planets and moons are dangerous and difficult to explore.

University of Arizona, California Institute of Technology, and U.S. Geological Survey Flagstaff researchers propose a novel space mission concept for finding and exploring the most scientifically important surfaces and subsurfaces throughout the solar system.

These next-generation robotic missions will simultaneously explore distant locales at several levels – from orbit, from the air and on the ground – to home in on important geology, hydrology, climate and possibly astrobiology in distant worlds, said James M. Dohm of The University of Arizona. Dohm, a planetary geologist in UA’s department of hydrology and water resources, has mapped Mars at local to global scales. He is involved with autonomous long-range roving, sensor web and orbiting spacecraft experiments.

Wolfgang Fink, a visiting associate at Caltech, Dohm and others discuss the new mission concept in an article, “Next-generation robotic planetary reconnaissance missions: A paradigm shift,” to be published in Elsevier?s journal of Planetary and Space Science (http://www.elsevier.com/, go to Article in Press link). They spearheaded a team effort that includes Mark Tarbell, who is Fink’s associate in Caltech’s Visual and Autonomous Exploration Systems Research Lab; Trent Hare of the U.S. Geological Survey office in Flagstaff; and Victor Baker, Regents’ Professor of the UA departments of hydrology and water resources, planetary sciences and geosciences.

The new mission concept would feature orbiting spacecraft, blimps and balloons at planets or moons with sufficient atmospheres, such as Titan, and numerous simple, deployable mobile and immobile ground sensors. These spaceborne, airborne, and ground agents would be programmed to look smartly at the environment and interact with each other, offering a true “tier-scalable” perspective needed for a science-driven mission, Dohm said.

“We are now at an optimal window in time when spacecraft and airborne units can coordinate with ground-based sensors, especially since much of the technology is already available,” said Fink, a physicist and an expert in imaging systems, autonomous control and space mission science analysis systems. “Even technology not currently available — software, primarily — is quite attainable.”

?It’s important to look at layers and layers of evidence, not just one type,” Dohm said.

For example, Fink said, a rover with feature-recognition software can look for a unique rock that could contain a critical piece of the history of Mars. “If you add an airborne perspective, you also see what?s on the other side of the hill at the same time, and you know the rover’s exact field location as well,” he said. The orbiter has the global picture of what’s going on and commands the airborne and ground tiers below it.

The orbiter in a tier-scalable mission is equipped with current information about the surface, atmosphere and other features of its destination. Its sensor suite might include optical and thermal cameras, spectrometers, and ground-penetrating radar. These instruments would collect information on areas that the orbiter’s software recognizes as possible interesting targets given the overall mission science goals.

“The orbiter can deploy the airborne agents for a closer look,” Fink said. “The orbiter also can command the airborne agents to safely deploy ground agents to the prime targets. The airborne agents help detect and confirm prime targets.”

“The ground agents can measure information such as heat or moisture,” Dohm said. “Or they can sample or collect diverse rocks and, in the case of Mars, possible near-surface water. There could be numerous lightweight, expendable sensors, so that even if you lost a few, you’d still have mission.”

The sensors send information back to their respective airborne probes, and ultimately to the orbiting spacecraft. Based on this new information, the orbiter sends new commands that drive the mission.

“The spaceborne, airborne, and ground agents all work together as a field geologist,” Dohm said. “They analyze information to form a working hypothesis.” They would be ideal for exploring Valles Marineris, the expansive canyon system of Mars, or Europa’s putative ice-covered ocean, he added.

In the case of Valles Marineris, for instance, Dohm said, the orbiting spacecraft would deploy sensors that would transmit weather conditions back to the spacecraft. If the sensors give the spacecraft a good weather report – no high winds, for example – the spacecraft would then release the balloons or blimps. These airborne agents would start their searches for targets important to mission goals, collecting and adding new information as they go and deploying ground agents at promising candidate sites. The ground agents would collect and return data to the higher-level airborne probes, or the orbiter, or both. “If the goal at Valles Marineris was to find possible water seeps or near-surface water, a drill rig might even be deployed at the most promising site,” Dohm said.

Fink and Dohm say the new concept needs further design, testing and ground-truthing in diverse Earth environments. They envision field camps for international researchers for designing and testing possible tier-scalable reconnaissance systems.

Intelligent, science-driven robotic space missions are a decade or two in the future, they will be international, and they will have significant corporate and private sponsorship, Dohm and Fink predict.

Original Source: University of Arizona News Release

Posted on by Fraser Cain

Cassini’s Closeup View of Dione

Dione perched in front of Saturn. Image credit: NASA/JPL/SSI. Click to enlarge.
Sitting in the tranquility of space is the pale moon Dione, looking as if it’s posing for a painter. The moon is set against the stunning backdrop of Saturn, adorned in gold and draped with hues of blue.

Breathtaking views and a movie of the icy world are now available at http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini .

During the Cassini spacecraft’s only close flyby of the grayish moon, on Oct. 11, 2005, the spacecraft came within 500 kilometers (310 miles) of the surface.

Like most of its counterparts in the Saturnian system, Dione shows a heavily cratered surface. It has a signature style all its own that includes streaky terrains dominating one whole side of the moon. The fine latitudinal streaks appear to crosscut everything and appear to be the youngest feature type in this region of Dione. These striking cracks and fractures are caused by tectonic activity.

“Dione seems to be an older sibling of Enceladus,” said Dr. Bonnie Buratti, scientist on the Cassini visual and infrared mapping spectrometer team at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “We think that the cracked features of Dione may be the older version of the tiger stripes on Enceladus. Enceladus is the up-and-coming moon, complete with a recently active history, while Dione is the older, more mature moon.”

The Cassini infrared spectrometer team is working on compositional maps of the moon’s surface.

As it departed its encounter with Saturn?bfs moon Dione, Cassini sailed above an unreal landscape blasted by impacts. The rising Sun throws craters into sharp contrast and reveals steep crater walls.
Multiple generations of fractures are visible on Dione. Numerous fine, roughly parallel grooves run across the terrain and are interrupted by the larger, irregular, bright fractures. In several places, fractures postdate some deposits in the bottoms of craters.

The Cassini ultraviolet imaging spectrograph team reports the detection of water ice on the surface of Dione and also finds striking brightness variations across the surface. This could be the result of cracks and fractures in the ice. “The ice in the fractures appears to be different than in the surrounding terrain. This may be due to the grain size variations,” said Dr. Amanda Hendrix, Cassini scientist at JPL.

As on other Saturnian moons, rockslides on Dione may reveal cleaner ice, while the darker materials accumulate in areas of lower topography, such as crater floors and the bases of scarps.

Scientists on the Cassini fields and particles instruments note that early results do not support the presence of an atmosphere. Dione orbits Saturn within the broad, tenuous E-ring. Hence, scientists will be looking to see if Dione, like Enceladus, is a source of material in the E-ring. They also seek to learn whether the E-ring is affecting Dione’s surface. Over the coming months, scientists will begin to piece together a more detailed story of Dione.

Following the rendezvous with Dione, Cassini captured its best views ever of the tiny moon Telesto. “Telesto was too small in Voyager images to see detail on the surface. Cassini has given us the best views of the potato-shaped chunk of ice,” said Dr. Candice Hansen, Cassini scientist at JPL. Early results indicate the entire moon, roughly 24 kilometers across (15 miles), is ice.

Next up for Cassini, on Oct. 28, is a close pass of Titan, Saturn’s largest moon. During this pass Cassini’s powerful radar will be pointed to image the Huygens probe landing site and surrounding terrain.

Original Source: NASA/JPL/SSI News Release