Posted on by Fraser Cain

Asteroid Bill Passes

Image credit: NASA
H.R. 912, the Charles “Pete” Conrad Astronomy Awards Act, named for the third man to walk on the moon, establishes awards to encourage amateur astronomers to discover and track near-earth asteroids. The bill directs the NASA Administrator to make awards, of $3,000 each, based on the recommendations of the Smithsonian Minor Planet Center. Earth has experienced several near misses with asteroids that would have proven catastrophic, and the scientific community relies heavily on amateur astronomers to discover and track these objects.

“Given the vast number of asteroids and comets that inhabit Earth’s neighborhood, greater efforts for tracking and monitoring these objects are critical. That is why I introduced H.R. 912, the Charles ‘Pete’ Conrad Astronomy Awards Act, which is a tribute to Pete Conrad for his tremendous contributions to the aerospace community over the last four decades,” said bill sponsor, Space and Aeronautics Subcommittee Chairman Dana Rohrabacher (R-CA). “Asteroids deserve a lot more attention from the scientific community. The first step is a thorough tracking of all sizeable Near Earth Objects, and H.R. 912 is a modest step towards this goal.”

Original Source: House Committee On Science News Release

Posted on by Fraser Cain

Landsat 5 Reaches 20 Years in Space

Image credit: NASA
March 1, 2004, marks the 20th anniversary of operations of the NASA/USGS ‘workhorse’ satellite, Landsat 5. Landsat 5, launched on March 1, 1984, continues to provide important observations of the landmass of the planet and has established a record for reliability in the civilian space fleet.

When Landsat 5 was launched from Vandenberg Air Base in California, expectations were for two years of effective operations, with a goal of three years of data collections. Instead, after 100,000 orbits and the acquisition of over 29 million images, Landsat 5 continues to operate successfully.

“The longevity and importance of the Landsat 5 mission is nothing short of incredible,” said Darrel Williams, Landsat 7 Project Scientist at NASA’s Goddard Space Flight Center. ” The imagery provided over it’s 20 year history has helped us to develop a far better understanding of the land surface features on our home planet, as well as how man has acted to modify those features. It has resulted in the creation of an unsurpassed “digital photo album” of Earth that will be repeatedly opened and reviewed by generations to come.”

Landsat 7 joined Landsat 5 in global observations in 1999. For four years the two earth observing satellites provided extensive, frequent coverage. “In May of 2003, Landsat 7 developed problems with the scan line corrector on the ETM+ sensor, stated Landsat Program manager Tracy Zeiler. “Since then, in addition to degraded Landsat 7 data, scientists have returned to relying on Landsat 5 observations. Landsat 5 has proven, again, to be a remarkably reliable source of information.”

The “workhorse” satellite continues to perform. While Landsat 5 continues to operate, Landsat Program managers are working on a replacement vehicle. The expected end-of -life, based on fuel reserves, is projected for early 2009. Until then, the NASA/USGS Landsat 5 will continue to provide records of a changing world.

For Additional Information on the Landsat Program, visit: http://landsat.gsfc.nasa.gov/

Original Source: NASA News Release

Posted on by Fraser Cain

Wallpaper: Hubble’s New Image of V838 Monocerotis

Image credit: Hubble
“Starry Night,” Vincent van Gogh’s famous painting, is renowned for its bold whorls of light sweeping across a raging night sky. Although this image of the heavens came only from the artist’s restless imagination, a new picture from NASA’s Hubble Space Telescope bears remarkable similarities to the van Gogh work, complete with never-before-seen spirals of dust swirling across trillions of miles of interstellar space.

This Hubble wallpaper, obtained with the Advanced Camera for Surveys on February 8, 2004, is Hubble’s latest view of an expanding halo of light around a distant star, named V838 Monocerotis (V838 Mon). The illumination of interstellar dust comes from the red supergiant star at the middle of the image, which gave off a flashbulb-like pulse of light two years ago. V838 Mon is located about 20,000 light-years away from Earth in the direction of the constellation Monoceros, placing the star at the outer edge of our Milky Way galaxy.

Called a light echo, the expanding illumination of a dusty cloud around the star has been revealing remarkable structures ever since the star suddenly brightened for several weeks in early 2002. Though Hubble has followed the light echo in several snapshots, this new image shows swirls or eddies in the dusty cloud for the first time. These eddies are probably caused by turbulence in the dust and gas around the star as they slowly expand away. The dust and gas were likely ejected from the star in a previous explosion, similar to the 2002 event, which occurred some tens of thousands of years ago. The surrounding dust remained invisible and unsuspected until suddenly illuminated by the brilliant explosion of the central star two years ago.

The Hubble telescope has imaged V838 Mon and its light echo several times since the star’s outburst in January 2002, in order to follow the constantly changing appearance of the dust as the pulse of illumination continues to expand away from the star at the speed of light. During the outburst event, the normally faint star suddenly brightened, becoming 600,000 times more luminous than our Sun. It was thus one of the brightest stars in the entire Milky Way, until it faded away again in April 2002. The star has some similarities to a class of objects called “novae,” which suddenly increase in brightness due to thermonuclear explosions at their surfaces; however, the detailed behavior of V838 Mon, in particular its extremely red color, has been completely different from any previously known nova.

Nature’s own piece of performance art, this structure will continue to change its appearance in coming years as the light from the stellar outburst continues to propagate outward and bounce off more distant black clouds of dust. Astronomers expect the echoes to remain visible for at least the rest of the current decade.

Original Source: Hubble News Release

Posted on by Mark Mortimer

Book Review: Sojourner, An Insider’s View of the Mars Pathfinder Mission

Sojourner was one of the first of NASA’s and JPL’s mandated faster, better, and cheaper projects. Before this mandate, a mission’s reliability was paramount and costs were correspondingly high. Sojourner’s predecessor, the Cassini mission, costed close to $1 billion. On the other hand, the Mars Pathfinder (Sojourner and the lander) mission had a total budget of $171 million. The Sojourner rover itself was capped at $25 million for design, parts, development, assembly, tests, and all operations during the mission. In spite of this, or perhaps because of this, there is a lot of evidence of solid managerial support, coupled with the workers’ nearly desperate attempts to scrounge resources and time. The book is a compendium of the problem definitions, the trial solutions, and the convergence to a workable solution that Mr. Mishkin and his colleagues faced for more than 10 years. Nevertheless, the skill, belief, and perseverance of many people made Sojourner faster, better, cheaper, and most importantly successful.

Sojourner’s design roots extended to the Lunar Surveyor Vehicle prototype that was planned for the moon but never used. This robot, nearly trashed, was resurrected by a JPL tinkerer with an interest in locomotion, vehicle suspension, and autonomous direction finding. From this beginning, serendipity plays its part as fortuitous events led to this rover, or one of its offspring, being demonstrated at the right time and before the right people to ensure that funding continued. Earth itself is a daunting realm for autonomous rovers, but Mars was a totally new territory. The temperature range was large, 110F over the duration of a day. The terrain was rough and unpredictable, sand could capture a wheel, or a ledge may roll the rover. Most of all, the 20 minute communications made direct control impossible. The first part of the book largely deals with tackling and overcoming this. It describes getting a solution to accommodate an acceptable body size, an optimal number of wheels, a forgiving suspension, and a safe guidance system. The later part of the book largely deals with the challenges of integrating the many prototypes, their unit testing, and the ensuing system testing.

In addition to designing a robotic rover, the book provides a glimpse of the challenges that face anyone taking on the role of a systems engineer. This role is to balance the needs, requirements, and expectations of all the players of a project so that there is a working solution. The solution is not necessarily optimal for anyone as everyone’s needs often directly conflict with others. The result is that no one is totally satisfied or completely happy. Mr. Mishkin displays a lot of the personality of his colleagues and himself as trade-offs are made, deals are done, and the rover comes together. This lends a wonderful human touch to what otherwise might be a somewhat dry and technical book. In accomplishing his goal Mr. Mishkin received some of the best words of praise for a systems engineer which are, “When you work on a job, things happen. Things get done”.

Though this book is enjoyable to read, it is difficult to classify. There is a lot of discussion on the technical aspects of resolving issues that arose in designing Sojourner, but there is too little to recommend it as a design reference. The challenges of being a systems engineer in a large project comes out loud and clear, but there is little to offer a new systems engineer on lessons learned. There is a lot of detail on the bugs, errors, and complications that needed correcting, but it is not really a comprehensive story of Sojourner. Further, there is no presentation of the scientific results. In the end, this book is exactly what it was meant to be, the personal memoirs of a technical expert from an exciting and challenging project.

I enjoyed seeing the historical thread that the Sojourner project wove amongst people and events. I particularly liked how it connected the lunar rover project of the 1950’s up to the start of the Spirit and Opportunity projects. As well, I could easily grasp the intangible value of team spirit, mutual support, and a work ethic that goes beyond a pay cheque. This is a book for engineers, especially those with an interest in robotics or space exploration. A person contemplating being a systems engineer would also enjoy reading this book to see the amazingly good things to which serendipity can lead.

Review by Mark Mortimer

Read more about the book at Amazon.com

Posted on by Fraser Cain

The Moon and Jupiter – Side By Side

Image credit: NASA
Lately Earth and Jupiter have been approaching one another, and this week the two worlds are only 400 million miles apart. That’s what astronomers call “a close encounter.”

400 million miles is close–on the vast scale of the solar system. Consider Pluto. It’s nearly ten times farther away than Jupiter. Or Saturn. The ringed planet is 800 million miles away. Nevertheless, Saturn looks wonderful right now, and Jupiter is even better.

400 million miles makes Jupiter ten times brighter than Saturn, and twenty-five times brighter than a 1st magnitude star. It outshines everything else in the sky except Venus, the Moon and the Sun.

See for yourself.

Step outside after sunset any night this week and look east. Jupiter is that very bright “star” near the horizon–not to be confused with even brighter Venus in the west. By 9 p.m. Jupiter will be high in the eastern sky, simply dazzling.

On March 4th, the date of closest approach, and March 5th, Jupiter will appear right beside the full Moon in the constellation Leo. So you won’t need a sky map to find Jupiter, just look for the Moon.

If you have a telescope, point it at Jupiter. Even a small ‘scope will reveal Jupiter’s rust-colored cloud belts and its four largest moons. Io, Europa, Callisto and Ganymede look like a dim line of stars straddling the giant planet. Sometimes only two or three moons are visible. That’s because one or two of them are behind Jupiter. Look again later or perhaps tomorrow. The missing moons will come out of hiding as they circle their planet.

The four “Galilean satellites”–so named because they were first observed by Galileo Galilei in 1610–are among the weirdest worlds in the solar system. Io looks like a pizza, and it has active volcanoes that spew sulfurous snow. Europa and Callisto are icy places, hiding, perhaps, the biggest oceans in the solar system beneath their frozen crusts. Ganymede is simply big–larger than Pluto and Mercury, and almost as wide as Mars. If it orbited the sun instead of Jupiter, Ganymede would be considered a full-fledged planet.

Sometimes you can see dark spots creeping across Jupiter. These are shadows cast by the four big moons. Sky & Telescope magazine publishes a schedule of shadow crossings, so you can find out when to look. The crossings are fun to watch through a telescope.

Another thing to look for is Jupiter’s Great Red Spot–a cyclone twice the size of Earth, and at least 100 years old. It swirls across Jupiter’s middle approximately every 10 hours. Again, check Sky & Telescope for viewing times.

First-time observers of Jupiter, squinting through the eyepiece of a small telescope, don’t always believe what they see. The giant planet looks slightly squashed. Is there something wrong with the optics? No, Jupiter really is flattened. The giant planet, 11 times wider than Earth, spins on its axis in only 9 hours and 55 minutes. Speedy rotation gives Jupiter an equatorial bulge. The “squash” is real.

So is the pizza moon, the giant cyclone, the alien oceans. They’re all just 400 million miles away. This is a close encounter you won’t want to miss.

Original Source: NASA Science Story

Posted on by Fraser Cain

Sulfur Could Support Martian Life

Image credit: NASA/JPL
During Tuesday’s NASA mission briefing on progress with the rover at Meridiani Planum, Mars Exploration Rover (MER) principal invesigator, Steve Squyres introduced not just startling new water evidence, but another new piece to the bigger astrobiological puzzle: water and sulfur. “With this quantity of sulfate [up to forty percent sulfur salts at some places near the Opportunity landing site], you kind of have to have water involved.”

But water is just the first puzzle piece in any future biological picture for the red planet, according to mission scientists. This sentiment was underscored by considering just a few of the puzzle pieces still missing. Time for instance is one element yet to be considered. “We know that the essential major and minor biogenic elements exist on Mars,” wrote Rocco Mancinelli , a SETI Institute scientist, “The primary factor in determining if life could have arisen on Mars lies in determining if liquid water existed on its surface for sufficient time. The history of water lies within the mineralogy of the rocks.”

Habitability and Energy
But now that some local portions of Mars show mineralogical promise of just such water at least temporarily ‘soaked’ into their geological record, what other key ingredients might be needed next, particularly to have supported a convincing case for ancient habitability? The tough question begs for a comparison to what microbiologists know about life on Earth, so one must begin with a simpler experiment: How would a hardy Earth microbe survive today on Mars?

Not particularly well, according to most microbiologists. The compound problems of low temperatures, low pressures, and scarce energy are multifold on today’s Mars, even when ‘today’ is taken to include the last tens of millions of years in Mars’ meteorological history.

Compared to the Earth’s average temperature of 15 C (59 F), Mars globally has an average temperature of -53 C (-63.4 F). While transient temperatures do occasionally rise above water’s freezing point in the equatorial regions around both landing sites, most biological scenarios need a booster shot of basic warmth. A habitable case for the red planet usually posits a long-lost Mars–one that was both wetter and warmer than what might seem hostile to even the hardiest lifeforms known today.

The Next Generation of Better Microbes, Desulfotomaculum
But once a water source is identified, perhaps the bigger immediate problem on Mars is the very thin and unbreathable atmosphere, one that is a mere one percent of Earth’s sea level pressure. If exposed on the surface, a microbe on Mars today would quickly dessicate and freeze. That is, unless it could pull off some kind of hibernation once the environment turned extreme to its favored biology. A promising microbial candidate must evolve some means to sporulate, as it would prove a big plus to hibernate during long periods whenever Martian weather turned inhospitable.

Scientists intrigued by ancient–and so far, local– water evidence uncovered near the Opportunity site have posed the speculative question: would spore-forming, sulfate-reducing bacteria offer a new model organism for the next generation of Mars’ microbe hunters?

According to one veteran Viking and MER science team member, Benton Clark, one such candidate has been a leading contender for weathering the harsh martian conditions that could otherwise fatally stress a microbe. Clark, of Lockheed Martin in Denver, said “I’ve always had a favorite organism, Desulfotomaculum, which is an organism that can live off sulfate, as we find in these rocks.”

Since 1965, when the spore-former was first discovered and classified, its biology has offered some of the best extremes for microbial survivability. Living without sunlight while forming spores when the weather gets cold or dry could make this hardy organism a model to consider among future planetary scientists.

Primitive Solar Energy Independence
Loosely, the name Desulfotomaculum means a ‘sausage’ that reduces sulfur compounds. It is a rod-shaped organism; the Latin, -tomaculum, means ‘sausage’. Desulfotomaculum is an anaerobe, meaning it does not require oxygen. Terrestrially, it is found in soil, water, and geothermal regions, and in the intestines of insects and animal rumens. Its lifecycle depends on reducing sulfur compounds like magnesium sulfate (or epsom salts) to hydrogen sulfide.

The sulfur-metabolizing microbes use a very primitive form of energy generation: their chemical action is as important as their immediate habitat. From what we know about conditions on the early Earth, it was probably hot, and there was a lot of ultraviolet (UV). It was a reducing atmosphere, so things like hydrogen sulfide as an inorganic source of energy are probably what was available to use. On Earth, some Desulfotomaculum species grow optimally at 30-37 C but can grow at other temperatures depending on which of the nearly 20 species of Desulfotomaculum is being cultured.

On the frigid, dry planet so far from the Sun, anything that metabolizes successfully would also benefit from some novel pathways other than photosynthesis to produce energy. Surprisingly while certain kinds of radiation hazards on Mars can be treacherous, the lack of UV sunlight itself is an immediate problem. What kind and intensity of sunlight might be most useful to common green or chlorophyll-rich life on Earth? Or when might a microbe thrive only with helpful shade from soil coverage or a dark rocky overhang. Doing without direct sunlight might be a Martian norm.

“[Desulfotomaculum] needs some hydrogen to go with that, but [sulfur] is its energy source. It can work independent of the sun,” said Clark. “The reason I like the latter organism is because it can form spores as well, so it can hibernate over these interim times on Mars between the warmer spells and the differences in [solar] obliquity that we know about.”

“So in addition to physical evidence of fossils,” said Clark, “you can have chemical evidence. It turns out that sulfur is one of those tracers that work out quite well in isotopic fractionation. When living organisms process sulfur, they tend to fractionate isotopes differently from geological or mineralogical ways…So there are organisms and isotopic ways to look for it. To do the isotopic analysis, you’re probably going to have the samples back on Earth.”

Preserving Life
MIT geologist, John Grotzinger, took up the challenging question of how a future mission planner might begin to formulate an overall biological strategy. After successfully landing near this kind of outcrop at the Opportunity site, can a future Mars’ mission look for evidence of fossil life? “The answer to this question is very simple. On Earth, which is the only experience that we have, finding fossils preserved in ancient rocks is very rare. You have to do everything you can to optimize the situation for their preservation.”

From the outset of the Opportunity mission, Andrew Knoll, a Harvard paleontologist and member of the MER science team told Astrobiology Magazine that, “The real question that one wants to keep in mind when thinking about Meridiani is: What, if any, signatures of that biology actually get preserved in diagenetically stable rocks? ..If water is present on the Martian surface for 100 years every 10 million years, that’s not very interesting for biology. If it’s present for 10 million years, that’s very interesting.”

“You worry first about preservation,” emphasized Grotzinger. “You target your strategy to optimize preservation. If something was there, these [conditions can be] ideal for time capsules…but it is something of a challenge. …We want to urge caution in interpreting these results at this point.”

“Stay tuned,” concluded Squyres.

Original Source: NASA/Astrobiology Magazine

Posted on by Fraser Cain

The Asteroid that Almost Hit

Image credit: NASA
For a few hours on January 13, 2004, astronomers thought a 30-meter wide asteroid might hit the Earth. The asteroid AL00667 seemed to be on a direct course for the Northern Hemisphere, due to strike in less than two days.
A 30-meter asteroid is larger than a tennis court. An asteroid of this size would have broken up in the atmosphere, creating a one-megaton blast. If it exploded high enough, the asteroid probably wouldn’t have caused any damage. The shock wave from the blast would have become a sonic boom by the time it reached the ground. But an explosion lower in the atmosphere could have caused considerable damage.

Astronomers who knew about the asteroid believed an impact was not likely, but they couldn’t rule out the possibility, either. So they faced a dilemma – should they warn others about something that could end up passing us by?

President Bush was preparing to make a speech at NASA headquarters the next day. He planned to talk about sending a man back to the moon and then on to Mars, but news of an approaching asteroid may have caused him to make a very different kind of announcement.

The asteroid, which has since been renamed 2004 AS1, actually passed by at about 12 million kilometers away, or 32 times the Earth-moon distance. The asteroid also turned out to be 10 times larger than first thought (about 300 meters wide – or about the height of the Eiffel Tower).

Some recent news reports say that Clark Chapman, an astronomer with the Southwest Research Institute, was moments away from calling President Bush and warning him about the asteroid. Chapman, however, adamantly denies this.

“It is absurd to think that any of us in the loop would have called the White House,” states Chapman. “Hell, we wouldn’t even have gotten through. All I was thinking about was recommending to Don Yeomans, who is in charge of JPL’s [the Jet Propulsion Laboratory’s] Near Earth Object Program office, that he inform people at NASA. It would have had to go through several layers of hierarchy before it got to anyone who would have been in a position to go higher than NASA. And Yeomans says that he wouldn’t have acted on my advice, preferring to wait for further confirmation of the object.”

The difference between the initial estimates and the final result highlights the difficulty of monitoring the skies for small Near Earth Objects (NEOs). For 2004 AS1, astronomers knew the asteroid could be either big and far away, or small and close by.

“It’s rather like noticing something in the sky out of your car window that appears to be moving along with you,” explains Alan Harris of the Space Science Institute. “It could be a bird close to your car flying along at close to the same speed, or it could be a plane in the distance that only seems to be pacing your car.”

Over the next few weeks after January 13, the asteroid came even closer to Earth, but it still passed many times farther away than the moon. There are many asteroids that routinely pass much closer to the Earth, says Harris, and asteroids the size and distance of 2004 AS1 are “a dime a dozen.”

“I think we all realized the odds were in favor of the larger, more distant object, rather than a real impactor on its way in,” says Harris.

Chapman first discussed these events in a paper presented on February 22 at the Planetary Defense workshop for the American Institute of Aeronautics and Astronautics (AIAA).

“Just last month, perhaps the most surprising impact prediction ever came and went, this time out of the view of the round-the-clock news media,” said Chapman. “It illustrates how an impact prediction came very close to having major repercussions, even though — with hindsight — nothing was ever, in reality, threatening to impact.”

The Lincoln Near Earth Asteroid Research (LINEAR) observatories in New Mexico sends routine nightly observations to the Minor Planet Center (MPC) in Cambridge, Massachusetts. On January 13, when the MPC received the LINEAR data, they performed the usual computations, and five objects were automatically highlighted as being of potential interest. One of these objects was the asteroid that was initially named AL00667.

Information about the five objects was posted on the publicly accessible NEO Confirmation Page (NEOCP). This data is posted so that amateur and professional asteroid astronomers can follow up on the LINEAR observations each night.

The MPC didn’t notice right away that one of their highlighted objects appeared to have an interesting trajectory. But Reiner Stoss, an amateur astronomer in Germany, saw that AL00667 was predicted to get 40 times brighter over the next day. He shared this information on Yahoo’s Minor Planet Mailing List (MPML). Another amateur observer, Richard Miles in England, noticed the same thing and even took images of the predicted area in the sky (although he found nothing).

Harris was monitoring the MPML mailing list at the time, and his quick calculations indicated that the asteroid could strike as soon as one day. He hurriedly contacted his colleagues, including Don Yeomans and NASA Ames Research Center’s David Morrison, who is chair of the International Astronomical Union’s Working Group on NEOs.

The word on the potential asteroid threat was out, and members of the MPML swapped anxious speculations while the scientists swapped a flurry of e-mails and additional calculations. Steven Chesley, a researcher at JPL, sent an e-mail several hours later saying that after looking at all the available data, he estimated the asteroid had a 25 percent chance of striking the Northern Hemisphere as soon as the following night, or as late as a few days later.

To determine whether the asteroid really posed a threat to Earth, more observations were needed. But Mother Nature wasn’t cooperating. Heavy cloud cover obscured much of the night skies in both Europe and North America.

Finally, thanks to clearer skies over Colorado, amateur astronomer Brian Warner was able to use a 20-inch aperture telescope to look for the asteroid. His search covered a broader area of sky than had been searched by Miles, and it covered the entire area that the asteroid should have been within to be on a collision course with Earth. The asteroid wasn’t there, meaning it wasn’t going to strike us after all.

Chapman says part of the problem that night was that the LINEAR data was not as accurate as usual. He thinks the inaccuracy of this data may have been due to the cloudy conditions. The light from the waning quarter moon also may have been a factor.

There is a protocol set in place to prepare for a large asteroid impact, but no such plans exist for smaller asteroids that can catch us off guard. Larger asteroids would be noticed long before they approached Earth, and we would have years if not decades to make plans. But smaller asteroids can seemingly come out of nowhere, giving us much less time to plan.

If a small asteroid was going to strike the Earth in just a few days, both Chapman and Harris say there would not be enough time to deflect or destroy the asteroid. Instead, scientists would try to determine exactly where the asteroid was to hit so that the area could be evacuated, if necessary. But Chapman admits that it is not easy to figure out exactly where a small asteroid will strike the Earth.

“In the case of the 30-meter body, the danger zone would be no larger than a few tens of miles across,” says Chapman. “It is hardly certain that we would be able to predict ground-zero that accurately.”

There are thought to be more than 300,000 nearby small asteroids (asteroids about 100 meters across). Such asteroids should statistically hit Earth once every few thousand years. The most recent such asteroid strike occurred in 1908, when an asteroid measuring about 60 meters in diameter hit Russia. The “Tunguska” bolide exploded in the atmosphere and flattened about 700 square miles of Siberian forest.

Large (1 kilometer or greater) asteroids are far more rare and infrequent. There are only about 1,100 nearby large asteroids, and they are predicted to strike the Earth every half million years or so. But when these asteroids strike, they can cause catastrophic changes in the global climate. Asteroids that cause mass extinctions are thought to be 10 kilometers or greater in diameter.

The Spaceguard Survey was established to track large asteroids and comets that might pose a direct threat to Earth. So far, the Spaceguard Survey has found about half of these NEOs, and they expect to find the majority of them by 2008. The Spaceguard Survey telescopes also occasionally find smaller asteroids, such as the one discovered the night of January 13.

Although there are no current plans to establish a program to track the numerous small NEOs, Chapman says there have been proposals to do so. Such surveys would be able to track asteroids in the 150 to 500 meter range, and would find even smaller asteroids as well.

Original Source: Astrobiology Magazine

Posted on by Fraser Cain

Adaptive Optics Reveal Massive Star Formation

Image credit: UC Berkeley
University of California, Berkeley, astronomers have taken advantage of a recently mounted laser guide star system at UC’s Lick Observatory to obtain sharp, twinkle-free images of the faint dusty disks of distant massive stars. The images clearly show that stars two to three times larger than the sun form in the same way as solar-type stars – inside a swirling spherical cloud that collapses into a disk, like that from which the sun and its planets emerged.

The yellow laser beam piercing the heavens over Lick Observatory became operational on the 10-foot Shane telescope last year, expanding use of the telescope’s “rubber mirror” system, called adaptive optics, to the entire nighttime sky. The addition of the laser makes Lick the only observatory to provide a laser guide star for routine use.

The UC Berkeley team and its colleagues at UC Santa Cruz’s Center for Adaptive Optics and Lawrence Livermore National Laboratory (LLNL) report their results in the Feb. 27 issue of the journal Science.

“The paradigm for stars like our sun is gravitational collapse of a cloud to a protostar and a pancake-like accretion disk, but there’s some mass at which this can’t work – the luminosity of the star becomes sufficient to disrupt the disk, and it falls apart as fast as it pulls together,” said James R. Graham, professor of astronomy at UC Berkeley. “Our data show that the standard model paradigm still works for stars two to three times as massive as the sun.”

“Without adaptive optics, we’d see only a big fuzzy blob from the ground and would be unable to detect any of the fine structure around the sources,” added UC Berkeley graduate student Marshall D. Perrin. “Our observations provide strong support for an emerging view that low and intermediate mass stars form in a similar manner.”

An adaptive optics system, which removes the blurring effects of atmospheric turbulence, was added to Lick’s Shane telescope in 1996. However, like all other telescopes with adaptive optics today, including the twin 10-meter Keck Telescopes in Hawaii, the Lick telescope has had to rely upon bright stars in the field of view to provide the reference needed to remove the blur. Only about one to 10 percent of the objects in the sky are sufficiently near a bright star for such a “natural” guide star system to work.

The sodium dye laser, developed by ace laser scientists Deanna M. Pennington and Herbert Friedman of LLNL, finally completes the adaptive optics system so that astronomers can use it to view any part of the sky, whether or not a bright star is nearby.

Strapped to the bore of the Lick telescope, the laser shines a narrow beam about 60 miles through the turbulent zone into the upper atmosphere, where the laser light stimulates sodium atoms to absorb and re-emit light of the same color. The sodium comes from micrometeorites that flame out and evaporate as they enter the Earth’s atmosphere.

The yellow glowing spot created in the atmosphere is equivalent to a 9th magnitude star – about 40 times fainter than the human eye can see. Nevertheless, it provides a steady light source just as effective as a bright distant star.

“We use that light to measure the turbulence in the atmosphere over our telescope hundreds of times per second, and then use that info to shape a special flexible mirror in such a way that when the light, both from the laser and the target you are looking at, bounces off it, the effects of the turbulence are removed,” said Claire Max, a professor of astronomy and astrophysics at UC Santa Cruz, deputy director of the Center for Adaptive Optics and a researcher at LLNL who has been working for more than 10 years to develop a laser guide star system.

In one of the first tests of this system, Graham and Perrin turned the telescope on rare, young, massive stars called Herbig Ae/Be stars that are fuzzy from the ground and typically too faint to be imaged by natural guide star adaptive optics. Herbig Ae/Be stars, with masses between 1.5 and 10 times that of the sun and probably less than 10 million years old, are thought to be the beginnings of massive stars – stars that will end up like the hot, Type A stars Sirius and Vega. Herbig Ae/Be stars were cataloged years ago by UC Santa Cruz astronomer George Herbig, now at the University of Hawaii.

The most massive of the Herbig Ae/Be stars are of great interest because they are the ones that undergo supernova explosions that seed the galaxy with heavy atoms, making solid planets and even life possible. They also trigger star formation in nearby clouds.

What the astronomers saw was very similar to the known picture of T Tauri stars, which are the formative stages of stars up to 50 percent bigger than our sun and up to 100 million years old. Images of the two Herbig Ae/Be stars clearly show a dark line bisecting each star, caused by a disk blocking the star’s bright glare, and a glowing spherical halo of dust and gas enveloping the star and disk. In each star, two jets of gas and dust can be seem emerging from the poles of the accretion disk.

The two stars, catalogued as LkH( 198 and LkH( 233 (Lick hydrogen-alpha sources), are 2,000 and 3,400 light years away, respectively, in a distant region of the Milky Way galaxy.

“Material from the protostellar cloud cannot fall directly into the infant star, so it first lands in an accretion disk and only moves inward to fall onto the star after it has shed its angular momentum,” Perrin explained. “That process of angular momentum transfer, along with the evolution of magnetic fields, leads to the launching of the bipolar outflows. These outflows eventually clear away the envelope, leaving a newborn star surrounded by an accretion disk. Over a few million years, the rest of the material in the disk is accreted, leaving only the young star behind.”

Perrin added that the Hubble Space Telescope has provided “very clear-cut, unambiguous images of disks and outflows around T Tauri stars,” confirming theories about the formation of stars like our sun. But, due to the relative rarity of Herbig Ae/Be stars, such clear data for those stars has been lacking until now, he said.

Astronomers have proposed that very massive stars form from the collision of two or more stars, or in a turbulent cloud unlike the swirling accretion disk. Interestingly, a third star imaged the same night by Graham and Perrin turned out to be two sun-like stars with a ribbon of gas and dust between them, looking suspiciously like one star capturing matter from the other.

Graham hopes to photograph more massive Herbig Ae/Be stars to see if the standard star formation model extends to even larger stars. The detailed images of the Herbig Ae/Be stars owe as much to the new laser guide star system as to a near-infrared imaging polarimeter built by Perrin and added to the Berkeley Near Infrared Camera (IRCAL) already mounted on the telescope.

“Without a polarimeter, light from the stars largely obscures the structures around them,” Perrin said. “The polarimeter separates unpolarized starlight from polarized scattered light from the circumstellar dust, which increases the detectability of that dust. Now that we’ve developed this technique at Lick, it will be possible to extend it to the 10-meter Keck telescopes as the laser guide star system there becomes operational.”

The polarimeter splits the light from the image into its two polarizations using a new type of birefringent crystal made of lithium, yttrium and fluorine (LiYF4), an improvement over the calcite crystals used to date.
Many other groups are developing lasers to be used as guide stars, but Max’s group has been ahead of its competitors since first demonstrating the concept in the early 1990s at Livermore. Since then, she and colleagues have been perfecting the laser and the software that allows the mirror – in the case of Lick’s 120-inch telescope, a 3-inch secondary mirror inside the main telescope – to be flexed just right to remove the twinkle from stars.

The 11- to 12-watt laser is a sodium dye laser tuned to the frequency that will excite the cold sodium atoms in the atmosphere. The dye laser is pumped by a green neodymium YAG laser, a bigger brother to the readily available green milliwatt laser pointers.

“The reason we can now do science with the laser guide star system is that its reliability and usability is so much improved,” Graham said. “The laser opens up adaptive optics to a much larger community.”

“I think it’s going to be a workhorse instrument at Lick,” added Max. “The laser itself and adaptive optics system hardware are pretty stable and pretty robust. What’s going to happen now is that people are going to do astronomy with it, they’re going to develop new techniques to observe with it, try it on new types of objects. In the typical way, a good astronomer will come and do things with your instrument that you never imagined.”

Max and her colleagues have tested an identical laser guide star system at the Keck Telescopes in Hawaii, but it is not yet ready for routine use, she said.
“The Keck is using the same technology we have at Lick,” Max said. “I expect to see this general technology used on most telescopes, but with different kinds of lasers. People are inventing new types of lasers right and left, so I think that game remains to settle out.”

Other authors of the Science paper, aside from Graham, Perrin, Max and Pennington, are affiliated with the National Science Foundation’s Center for Adaptive Optics, centered at UC Santa Cruz: assistant research astronomer Paul Kalas of UC Berkeley, James P. Lloyd of the California Institute of Technology, Donald T. Gavel of UC Santa Cruz’s Laboratory for Adaptive Optics, and Elinor L. Gates of the UC Observatories/Lick Observatory.

The observations and development of the laser guide star were funded by the National Science Foundation and the U.S. Department of Energy.

Original Source: UC Berkeley News Release

Posted on by Fraser Cain

Water Once Drenched Regions of Mars

Image credit: NASA/JPL
Scientists have concluded the part of Mars that NASA’s Opportunity rover is exploring was soaking wet in the past.

Evidence the rover found in a rock outcrop led scientists to the conclusion. Clues from the rocks’ composition, such as the presence of sulfates, and the rocks’ physical appearance, such as niches where crystals grew, helped make the case for a watery history.

“Liquid water once flowed through these rocks. It changed their texture, and it changed their chemistry,” said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the science instruments on Opportunity and its twin, Spirit. “We’ve been able to read the tell-tale clues the water left behind, giving us confidence in that conclusion.”

Dr. James Garvin, lead scientist for Mars and lunar exploration at NASA Headquarters, Washington, said, “NASA launched the Mars Exploration Rover mission specifically to check whether at least one part of Mars ever had a persistently wet environment that could possibly have been hospitable to life. Today we have strong evidence for an exciting answer: Yes.”

Opportunity has more work ahead. It will try to determine whether, besides being exposed to water after they formed, the rocks may have originally been laid down by minerals precipitating out of solution at the bottom of a salty lake or sea.

The first views Opportunity sent of its landing site in Mars’ Meridiani Planum region five weeks ago delighted researchers at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., because of the good fortune to have the spacecraft arrive next to an exposed slice of bedrock on the inner slope of a small crater.

The robotic field geologist has spent most of the past three weeks surveying the whole outcrop, and then turning back for close-up inspection of selected portions. The rover found a very high concentration of sulfur in the outcrop with its alpha particle X-ray spectrometer, which identifies chemical elements in a sample. “The chemical form of this sulfur appears to be in magnesium, iron or other sulfate salts,” said Dr. Benton Clark of Lockheed Martin Space Systems, Denver. “Elements that can form chloride or even bromide salts have also been detected.”

At the same location, the rover’s Moessbauer spectrometer, which identifies iron-bearing minerals, detected a hydrated iron sulfate mineral called jarosite. Germany provided both the alpha particle X- ray spectrometer and the Moessbauer spectrometer. Opportunity’s miniature thermal emission spectrometer has also provided evidence for sulfates.

On Earth, rocks with as much salt as this Mars rock either have formed in water or, after formation, have been highly altered by long exposures to water. Jarosite may point to the rock’s wet history having been in an acidic lake or an acidic hot springs environment.

The water evidence from the rocks’ physical appearance comes in at least three categories, said Dr. John Grotzinger, sedimentary geologist from the Massachusetts Institute of Technology, Cambridge: indentations called “vugs,” spherules and crossbedding.

Pictures from the rover’s panoramic camera and microscopic imager reveal the target rock, dubbed “El Capitan,” is thoroughly pocked with indentations about a centimeter (0.4 inch) long and one-fourth or less that wide, with apparently random orientations. This distinctive texture is familiar to geologists as the sites where crystals of salt minerals form within rocks that sit in briny water. When the crystals later disappear, either by erosion or by dissolving in less-salty water, the voids left behind are called vugs, and in this case they conform to the geometry of possible former evaporite minerals.

Round particles the size of BBs are embedded in the outcrop. From shape alone, these spherules might be formed from volcanic eruptions, from lofting of molten droplets by a meteor impact, or from accumulation of minerals coming out of solution inside a porous, water-soaked rock. Opportunity’s observations that the spherules are not concentrated at particular layers in the outcrop weigh against a volcanic or impact origin, but do not completely rule out those origins.

Layers in the rock that lie at an angle to the main layers, a pattern called crossbedding, can result from the action of wind or water. Preliminary views by Opportunity hint the crossbedding bears hallmarks of water action, such as the small scale of the crossbedding and possible concave patterns formed by sinuous crestlines of underwater ridges.

The images obtained to date are not adequate for a definitive answer. So scientists plan to maneuver Opportunity closer to the features for a better look. “We have tantalizing clues, and we’re planning to evaluate this possibility in the near future,” Grotzinger said.

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.

For information about NASA and the Mars mission on the Internet, visit http://www.nasa.gov. Images and additional information about the project are also available at http://marsrovers.jpl.nasa.gov and http://athena.cornell.edu.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Black Holes Maintain Their Information

Image credit: NASA
Stephen Hawking and Kip Thorne may owe John Preskill a set of encyclopedias.

In 1997, the three cosmologists made a famous bet as to whether information that enters a black hole ceases to exist — that is, whether the interior of a black hole is changed at all by the characteristics of particles that enter it.

Hawking?s research suggested that the particles have no effect whatsoever. But his theory violated the laws of quantum mechanics and created a contradiction known as the ?information paradox.?

Now physicists at Ohio State University have proposed a solution using string theory, a theory which holds that all particles in the universe are made of tiny vibrating strings.

Samir Mathur and his colleagues have derived an extensive set of equations that strongly suggest that the information continues to exist — bound up in a giant tangle of strings that fills a black hole from its core to its surface.

The finding suggests that black holes are not smooth, featureless entities as scientists have long thought.

Instead, they are stringy ?fuzzballs.?

Mathur, professor of physics at Ohio State, suspects that Hawking and Thorne won?t be particularly surprised by the outcome of the study, which appears in the March 1 issue of the journal Nuclear Physics B.

In their wager, Hawking, professor of mathematics at the University of Cambridge, and Thorne, professor of theoretical physics at Caltech, bet that information that enters a black hole is destroyed, while Preskill — also a professor of theoretical physics at Caltech — took the opposite view. The stakes were a set of encyclopedias.

?I think that most people gave up on the idea that information was destroyed once the idea of string theory rose to prominence in 1995,? Mathur said. ?It?s just that nobody has been able to prove that the information survives before now.?

In the classical model of how black holes form, a supermassive object, such as a giant star, collapses to form a very small point of infinite gravity, called a singularity. A special region in space surrounds the singularity, and any object that crosses the region?s border, known as the event horizon, is pulled into the black hole, never to return.

In theory, not even light can escape from a black hole.

The diameter of the event horizon depends on the mass of the object that formed it. For instance, if the sun collapsed into a singularity, its event horizon would measure approximately 3 kilometers (1.9 miles) across. If Earth followed suit, its event horizon would only measure 1 centimeter (0.4 inches).

As to what lies in the region between a singularity and its event horizon, physicists have always drawn a blank, literally. No matter what type of material formed the singularity, the area inside the event horizon was supposed to be devoid of any structure or measurable characteristics.

And therein lies the problem.

?The problem with the classical theory is that you could use any combination of particles to make the black hole — protons, electrons, stars, planets, whatever — and it would make no difference. There must be billions of ways to make a black hole, yet with the classical model the final state of the system is always the same,? Mathur said.

That kind of uniformity violates the quantum mechanical law of reversibility, he explained. Physicists must be able to trace the end product of any process, including the process that makes a black hole, back to the conditions that created it.

If all black holes are the same, then no black hole can be traced back to its unique beginning, and any information about the particles that created it is lost forever at the moment the hole forms.

?Nobody really believes that now, but nobody could ever find anything wrong with the classical argument, either,? Mathur said. ?We can now propose what went wrong.?

In 2000, string theorists named the information paradox number eight on their top-ten list of physics problems to be solved during the next millennium. That list included questions such as ?what is the lifetime of a proton?? and ?how can quantum gravity help explain the origin of the universe??

Mathur began working on the information paradox when he was an assistant professor at the Massachusetts Institute of Technology, and he attacked the problem full time after joining the Ohio State faculty in 2000.

With postdoctoral researcher Oleg Lunin, Mathur computed the structure of objects that lie in-between simple string states and large classical black holes. Instead of being tiny objects, they turned out to be large. Recently, he and two doctoral students — Ashish Saxena and Yogesh Srivastava — found that the same picture of a ?fuzzball? continued to hold true for objects more closely resembling a classic black hole. Those new results appear in Nuclear Physics B.

According to string theory, all the fundamental particles of the universe — protons, neutrons, and electrons — are made of different combinations of strings. But as tiny as strings are, Mathur believes they can form large black holes through a phenomenon called fractional tension.

Strings are stretchable, he said, but each carries a certain amount of tension, as does a guitar string. With fractional tension, the tension decreases as the string gets longer.

Just as a long guitar string is easier to pluck than a short guitar string, a long strand of quantum mechanical strings joined together is easier to stretch than a single string, Mathur said.

So when a great many strings join together, as they would in order to form the many particles necessary for a very massive object like a black hole, the combined ball of string is very stretchy, and expands to a wide diameter.

When the Ohio State physicists derived their formula for the diameter of a fuzzy black hole made of strings, they found that it matched the diameter of the black hole event horizon suggested by the classical model.

Since Mathur?s conjecture suggests that strings continue to exist inside the black hole, and the nature of the strings depends on the particles that made up the original source material, then each black hole is as unique as are the stars, planets, or galaxy that formed it. The strings from any subsequent material that enters the black hole would remain traceable as well.

That means a black hole can be traced back to its original conditions, and information survives.

This research was supported in part by the U.S. Department of Energy.

Original Source: Ohio State University News Release