Posted on by Fraser Cain

Mars Was Once Suitable For Life

Image credit: NASA
Scientists have long been tantalized by the question of whether life once existed on Mars. Although present conditions on the planet would seem to be inhospitable to life, the data sent back over the past 10 months by NASA’s two exploration rovers, Spirit and Opportunity, showed a world that might once have been warmer and wetter — perhaps friendly enough to support microbial organisms.

Now a Cornell University-led Mars rover science team reports on the historic journey by the rover Opportunity, which is exploring a vast plain, Meridiani Planum, and concludes with this observation: “Liquid water was once present intermittently at the martian surface at Meridiani, and at times it saturated the subsurface. Because liquid water is a key prerequisite for life, we infer that conditions at Meridiani may have been habitable for some period of time in martian history.”

The article is one of 11 published this week (Dec. 3, 2004) in a special issue of the journal Science, authored by scientists connected with the Mars rover mission, several from Cornell and from the Jet Propulsion Laboratory in Pasadena, Calif., the mission’s manager. The issue covers Opportunity through its first 90 days of exploring its landing site of Eagle crater in Meridiani Planum. This was before the rover drove to and entered the large crater dubbed Endurance, from which it is now about to emerge.

Steve Squyres, Cornell professor of astronomy and leader of the rovers’ Athena science team, is the lead author of the main paper, “The Opportunity Rover’s Athena Science Investigation at Meridiani Planum, Mars.” In another paper, on which he is also the lead author, Squyres again refers to the geological record at Meridiani Planum as suggesting that conditions were suitable for “biological activity” for a period of time in the history of mars. In the article, “In Situ Evidence for an Ancient Aqueous Environment at Meridiani Planum, Mars,” he writes: “We cannot determine whether life was present or even possible in the waters at Meridiani, but it is clear that by the time the sedimentary rocks in Eagle crater were deposited, Mars and Earth had already gone down different environmental paths. Sample return of Meridiani rocks might well provide more certainty regarding whether life developed on Mars.”

The Mars rover mission is not designed to look for microbial life but to look for evidence of whether conditions were once right for life. As Squyres recently stated, “What we were seeking was rocks that were actually formed in liquid water so that we could read the record in those rocks, not just to say liquid water was on Mars but to learn something about what the environmental conditions were like, would they have been suitable for life and, importantly, do the minerals that were formed have the capability to preserve for long periods of time evidence of former life? That’s probably the single most important thing we have found: evidence for minerals at Meridiani that are the kinds of things that are very good at preserving evidence of ancient life for very long periods of time.”

Opportunity bounced down on Jan. 25, 22 days after its twin, the rover Spirit, landed on the opposite side of Mars in Gusev crater. Last August Science published a special issue on Spirit.

“This is the first peer-reviewed presentation of the data from Opportunity,” notes Jim Bell, Cornell associate professor of astronomy and the lead scientist for the rovers’ Pancam color imaging system.

Bell also is prominent in the special issue of Science , including his lead authorship of a paper, “Pancam Multispectral Imaging Results from the Opportunity Rover at Meridiani Planum.”

When Opportunity landed on the red planet last January, the robot geologist sent back images of its landing site that were unlike any of the other places where earlier lander probes and rovers had gone. Instead of rusty deserts of dusty soil and boulders strewn to the horizon, Opportunity had landed in a relatively small crater in a vast sea of sand nearly devoid of rocks. Fortunately, an intriguing outcrop of bedrock presented itself nearby, which scientists hoped would be a sample of the original crust underneath the layers of dust.

The scientists were not disappointed. Scattered among the outcrop rocks were large numbers of small, round mineral deposits that the Athena science team named “blueberries.” On Earth, such formations appear when large amounts of water course through rock layers, leaching out the iron-bearing minerals into small spherical rocks and granules. The rovers also detected large amounts of sulfate salt deposits. Enough evidence was collected by Opportunity in the two months it spent examining Eagle crater that the science team felt confident enough to announce in early March that liquid water had flowed over the crater’s rocks long ago, possibly for a long time. Following on this, the latest Science articles largely focus on Opportunity’s most important scientific and geological accomplishment: the discovery of evidence that liquid water once flowed through the region.

Like the coverage given to Spirit in the August issue of Science , the latest edition contains several foldouts with big color panoramas and images from Opportunity’s region of exploration.

Original Source: Cornell News Release

Posted on by Fraser Cain

Greenland Glacier Speeds Up

When people talk about something moving at a glacial pace, they are referring to speeds that make a tortoise look like a hare. While it is all relative, glaciers actually flow at speeds that require time lapses to recognize. Still, researchers who study Earth’s ice and the flow of glaciers have been surprised to find the world’s fastest glacier in Greenland doubled its speed between 1997 and 2003.

The finding is important for many reasons. For starters, as more ice moves from glaciers on land into the ocean, it raises sea levels. Jakobshavn Isbrae is Greenland’s largest outlet glacier, draining 6.5 percent of Greenland’s ice sheet area. The ice stream’s speed-up and near-doubling of ice flow from land into the ocean has increased the rate of sea level rise by about .06 millimeters (about .002 inches) per year, or roughly 4 percent of the 20th century rate of sea level increase.

Also, the rapid movement of ice from land into the sea provides key evidence of newly discovered relationships between ice sheets, sea level rise and climate warming.

The researchers found the glacier’s sudden speed-up also coincides with very rapid thinning, indicating loss of ice of up to 15 meters (49 feet) in thickness per year after 1997. Along with increased rates of ice flow and thinning, the thick ice that extends from the mouth of the glacier into the ocean, called the ice tongue, began retreating in 2000, breaking up almost completely by May 2003.

The NASA-funded study relies on data from satellites and airborne lasers to derive ice movements. The paper appears in this week’s issue of the journal Nature.

“In many climate models glaciers are treated as responding slowly to climate change,” said Ian Joughin, the study’s lead author. “In this study we are seeing a doubling of output beyond what most models would predict. The ice sheets can respond rather dramatically and quickly to climate changes.” Joughin conducted much of this research while working at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. Joughin is currently a glaciologist at the Applied Physics Laboratory at the University of Washington, Seattle.

The researchers used satellite and other data to observe large changes in both speeds and thickness between 1985 and 2003. The data showed that the glacier slowed down from a velocity of 6700 meters (4.16 miles) per year in 1985 to 5700 meters (3.54 miles) per year in 1992. This latter speed remained somewhat constant until 1997. By 2000, the glacier had sped up to 9400 meters (5.84 miles) per year, topping out with the last measurement in spring 2003 at 12,600 meters (7.83 miles) per year.

“This finding suggests the potential for more substantial thinning in other glaciers in Greenland,” added Waleed Abdalati, a coauthor and a senior scientist at NASA’s Goddard Space Flight Center, Greenbelt, Md. “Other glaciers have thinned by over a meter a year, which we believe is too much to be attributed to melting alone. We think there is a dynamic effect in which the glaciers are accelerating due to warming.”

Airborne laser altimetry measurements of Jakobshavn’s surface elevation, made previously by researchers at NASA’s Wallops Flight Facility, showed a thickening, or building up of the glacier from 1991 to 1997, coinciding closely with the glacier’s slow-down. Similarly, the glacier began thinning by as much as 15 meters (49 feet) a year just as its velocity began to increase between 1997 and 2003.

The acceleration comes at a time when the floating ice near the glacier’s calving front has shown some unusual behavior. Despite its relative stability from the 1950’s through the 1990s, the glacier’s ice tongue began to break apart in 2000, leading to almost complete disintegration in 2003. The tongue’s thinning and breaking up likely reduced any restraining effects it had on the ice behind it, as several speed increases coincided with losses of sections of the ice-tongue as it broke up. Recent NASA-funded research in the Antarctic Peninsula showed similar increases in glacier flow following the Larson B ice shelf break-up.

Mark Fahnestock, a researcher at the University of New Hampshire, Durham, N.H., was also a co-author of this study.

Original Source: NASA News Release

Posted on by Fraser Cain

Wallpaper: Saturn’s Rings in Black and White

This close-up of the lit side of Saturn’s outer B ring and the Cassini Division looks something like a phonograph record. There are subtle, wavelike patterns, hundreds of narrow features resembling a record’s ‘grooves’ and a noticeable abrupt change in overall brightness beyond the dark gap near the right. To the left of the gap is the outer B ring with its sharp edge maintained by a strong gravitational resonance with the moon Mimas. To the right of the Huygens Gap are the plateau-like bands of the Cassini Division. The narrow ringlet within the gap is called the Huygens ringlet.

The image was taken in visible light with the Cassini spacecraft narrow angle camera on Oct. 29, 2004, at a distance of about 819,000 (509,000 miles) from Saturn. The image scale is 4.5 kilometers (2.8 miles) per pixel.

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 Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

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

Posted on by Mark Mortimer

Book Review: Centauri Dreams

First a bit of a background. We’ve a long way to go. Alpha Centauri is 4.3 light years away (about 13 zeros after the one when considering kilometres). Voyager 1, the fastest man made object, is speeding at 3.6 AU’s per year (about 8 zeros after the one in kilometres per year). Were a person to be on it, some 100,000 years would pass before entering Alpha Centauri’s solar system. This won’t happen as Voyager 1 travels another path, but this is the problem in a nutshell, it’s too far for today’s chemically driven rockets. With most people expecting a return on investment well within ten years then there would be little support in waiting thousands of generations for payback. Given this impracticality Gilster presents options and methods that might reduce the travel time to within one generation.

The first chapter sets the background of who’s doing what, where they are keeping themselves busy and, sometimes, when their activities first appear upon the scene. Scores of researchers’ names arise, especially physicists, mathematicians and astronomers, but a sprinkling of other esoteric specialists such as Internet designers, clearly demonstrates the broad response to this challenge. NASA’s programs and facilities predominate. CERN appears as does the Brookhaven National Laboratory. Early visionaries from the 1800’s and even earlier make a brief appearance. Applicable science fiction stories from the early 1900’s get noted, while the predominance of technically valid work dates from about 1960 on. This shows that on the whole, considerable thought and work has gone into advancing concepts for high speed interstellar travel.

Five chapters follow and represent the real meat of this book. These look at different methods of getting a useful payload to our neighbouring stars and they focus on well known and lesser known means of propulsion. Antimatter, sails, ramjets and fusion runways get their dues. Field-drives, providing force from the interaction of matter and fields get an honourable mention. Each chapter clearly and simply describes the methods of the chosen propulsion and the state (or technical level) of the research. Interviews with today’s investigators provide a superb insider’s view of activities. If you’re looking to identify locations for grad studies, there is a bonus as key investigating sites get identified alongside. Exciting sections detail the latest in experiments and technical investigations. The Planetary Society’s solar sail lifts off soon, antimatter is getting expansive new containers, lasers push model crafts up against Earth’s gravitational pull and a mini-magentospheric plasma propulsion prototype undergoes testing. Each of these might answer the riddle about how we propel ourselves at near light speed but as pointed out, the breakthrough technology may yet be around the corner.

One chapter seems a little bit like a lost child. This deals with communication and guidance. Of course these issues will need to be addressed, but it seems a bit early to be worrying about setting up extra-planetary webs or designing their communication protocol for that real long distance feeling. The guidance/navigation portion seems equally out of place. As the propulsion method so drastically constrains the mission, this discussion is preemptive. Still, as the title states, this book plans for interstellar exploration, hence communication and guidance are relevant and their consideration is warranted.

And yes, the title says it all. Alpha Centauri is a dreamers destination but dreams are only the beginning. Imagination gets us out of the constraints of everyday thinking and planning will see that effort gets well applied. As depicted within the book, many people share this dream. Some are incredibly lucky and can make it their life’s work. Others contribute directly in their part time or indirectly whether through related research, writing fiction or, as Gilster is undertaking, performing outreach activities. The link from imagination, to serious consideration and eventual trials constantly arises as either a sign of humanity’s adaptability or perhaps a sign of genetic coding. Nevertheless, time and again, imaginations are shown to conceive of the knowledge that thrusts plans out of the realm of fiction and into the laboratory where researchers make it reality.

Stars twinkle all about us at night. Perhaps maliciously inviting or teasing like a temptress, either way they remain today too far to fathom visiting today. Science fiction had imaginaries who gave detailed if somewhat fanciful means of propulsion between the stars. Paul Gilster in Centauri Dreams: Imagining and Planning Interstellar Exploration shows that real science is advancing technologies that could make this trip practical. The plans of the scientists and other technical may soon bear fruit and future generations of humans would have a much better and more exciting life amongst the stars.

Read more reviews online or order your own copy from Amazon.com.

Review by Mark Mortimer

Posted on by Fraser Cain

Would We Mistake Signals from ET?

Researchers from the University of Michigan think that the current programs to search for extraterrestrial intelligence (SETI) might not be able to distinguish signals from the noise of nearby stars. They showed how an efficient message sent through radio waves is nearly indistinguishable from the ordinary thermal radiation coming from stars. If extraterrestrial civilizations have been transmitting for a long time, they’ll probably have optimized their communications to save power, and so we won’t recognize it when we hear it.

If ET ever phones home, chances are Earthlings wouldn’t recognize the call as anything other than random noise or a star.

New research shows that highly efficient electromagnetic transmissions from our neighbors in space would resemble the thermal radiation emitted by stars.

University of Michigan physicist Mark Newman, along with biologist Michael Lachmann and computer scientist Cristopher Moore, have extended the pioneering 1940s research of Claude Shannon to electromagnetic transmissions in a paper published last month in the American Journal of Physics called, “The Physical Limits of Communication, or Why any sufficiently advanced technology is indistinguishable from noise.” Lachmann is at the Max Planck Institute in Leipzig, Germany; Moore is at the University of New Mexico in Albuquerque.

Shannon showed that a message transmitted with optimal efficiency is indistinguishable from random noise to a receiver unfamiliar with the language in the message. For example, an e-mail message whose first few letters are AAAAA contains little information because the reader can easily guess what probably comes next?another A. The message is totally non-random. On the other hand, a message beginning with a sequence of letters like RPLUOFQX contains a lot of information because you cannot easily guess the next letter.

Paradoxically, however, the same message could just be a random jumble of letters containing no information at all; if you don’t know the code used for the message you can’t tell the difference between an information-rich message and a random jumble of letters.

Newman and his collaborators have shown that a similar result holds true for radio waves.

When electromagnetic waves are used as the transmission medium, the most information efficient format for a message is indistinguishable from ordinary thermal radiation?the same kind of radio waves that are emitted by hot bodies like stars. In other words, an efficiently coded radio message coming from outer space would look no different from a normal star in the sky.

So, suppose an alien in space decided to pick up signs of Earth life. It would have a pretty easy time of it, since our radio and television signals are zigzagging all over the place and are inefficiently coded and easily distinguishable from stars.

But say a human tries to tune into extraterrestrial life.

“People do this, and when they do, they are looking for non-random stuff,” Newman said. “But what if (the aliens) have gotten it down? With a few hundred years practice at doing this, you’d have discovered the most efficient way to encode your radio messages. So to us, their communication would look just like another star, a hot object.”

After all, Newman said, in the universe’s 12 billion-year history, it’s likely that extraterrestrials?if they exist?have communicated with each other longer than our paltry 80-year history of radio broadcasting. “In which case, they’ve probably gotten very good at this by now.”

Said Newman: “Our message is that, even for the people who do believe this, they’re probably wasting their time. If they did pick up a signal from little green men, it would probably look like a star to them and they would just pass over it and move on to the next thing.”

Original Source: UMich News Release

Posted on by Fraser Cain

Dusty Universe is a Mystery

Image credit: NASA/JPL/UA
Astronomers who think they know how the very early universe came to have so much interstellar dust need to think again, according to new results from the Spitzer Space Telescope.

In the last few years, observers have discovered huge quantities of interstellar dust near the most distant quasars in the very young universe, only 700 million years after the cosmos was born in the Big Bang.

“And that becomes a big question,” said Oliver Krause of the University of Arizona Steward Observatory in Tucson and the Max Planck Institute for Astronomy in Heidelberg. “How could all of this dust have formed so quickly?”

Astronomers know two processes that form the dust, Krause said. One, old sun-like stars near death generate dust. Two, infrared space missions have revealed the dust is produced in supernovae explosions.

“The first process takes several billion years,” Krause noted. “Supernovae explosions, by contrast, produce dust in much less time, only about 10 million years.”

So when astronomers reported detecting submillimeter emission from massive amounts of cold interstellar dust in the supernova remnant Cassiopeia A last year, some considered the mystery solved. Type II supernovae like ‘Cas A’ likely produced the interstellar dust in the very early universe, they concluded. (Type II supernovae come from massive stars that blow apart in huge explosions after their cores collapse.)

Krause and colleagues from UA’s Steward Observatory and the Max Planck institute in Heidelberg have now discovered that the detected submillimeter emission comes not from the Cas A remnant itself but from the molecular cloud complex known to exist along the line of sight between Earth and Cas A. They report the work in the Dec. 2 issue of Nature.

Cas A is the youngest known supernova remnant in our Milky Way. It is about 11,000 light years away, behind the Perseus spiral arm clouds that are roughly 9,800 light years away. Krause suspects that the Perseus clouds explain why late 17th century astronomers didn’t report observing the brilliant Cas A outburst around A.D. 1680. Cas A is so close to Earth that the supernova should have been the brightest stellar object in the sky, but dust in the Perseus clouds eclipsed the view.

The Arizona and German team mapped Cas A at 160-micron wavelengths using the ultra-heat-sensitive Multiband Imaging Photometer (MIPS) aboard the Spitzer Space Telescope. These long wavelengths are the most sensitive to cold interstellar dust emission. They then compared the results with maps of interstellar gas previously made with radio telescopes. They found that the dust in these interstellar clouds account for virtually all the emission at 160 microns from the direction of Cas A.

Minus the emission from this dust, there is no evidence for large amounts of cold dust in Cas A, the team concludes.

“Astronomers will have to go on searching for the source of the dust in the early universe,” UA Steward Observatory astronomer and Regents’ Professor George Rieke said. Rieke is principal investigator for the Spitzer Space Telescope’s MIPS instrument and a co-author of the Nature paper.

“Solving this riddle will show astronomers where and how the first stars formed, or perhaps indicate there is some non-stellar process that can produce large amounts of dust,” Rieke said. “Either way, (finding the source of the dust) will reveal what went on at the formative stage for stars and galaxies, an epoch that is nearly unobserved in any other way.”

Authors of the Nature article, “No cold dust within the supernova remnant Cassiopeia A,” are Oliver Krause, Stephan M. Birkmann, George H. Rieke, Dietrich Lemke, Ulrich Klaas, Dean C. Hines and Karl D. Gordon.

Birkmann, Lemke and Klaas are with the Max Planck Institute for Astronomy in Heidelberg. Krause, Rieke, and Gordon are with the University of Arizona Steward Observatory. Hines is with the Space Science Institute in Boulder, Colo.

Original Source: UA News Release

Posted on by Fraser Cain

Sun Could Have Traded With Another Star

A hit TV program like “Antiques Roadshow” lures viewers with its universal appeal. Who wouldn’t want to find secret riches in their attic or basement? But rare paintings and heirloom jewelry aren’t the only valuable items waiting to be discovered. Cosmic treasures also lay hidden in the vast realm of outer space. Among the most highly prized of those treasures are planets that formed around other stars.

Astronomers have just gained an important clue to guide their hunt for extrasolar worlds. And that clue points to the unlikeliest of places – our own backyard.

“It’s possible that some of the objects in our solar system actually formed around another star,” says astronomer Scott Kenyon (Smithsonian Astrophysical Observatory).

How did these adopted worlds join our solar family? They arrived through an interstellar trade that took place more than 4 billion years ago when a wayward star brushed past our solar system. According to calculations made by Kenyon and astronomer Benjamin Bromley (University of Utah) and published in the Dec. 2, 2004, Nature, the Sun’s gravity plucked asteroid-sized objects from the visiting star. At the same time, the star pulled material from the outer reaches of our solar system into its grasp.

“There may not have been an equal exchange, but there was certainly an exchange,” says Bromley.

A Close Brush
Kenyon and Bromley reached this surprising conclusion while working to explain the mystery object Sedna, a world almost as large as Pluto but located much farther from the Sun. Sedna’s discovery in 2003 puzzled astronomers because of its unusual orbit – a 10,000-year-long oval whose closest approach to the Sun, 70 astronomical units, is well beyond the orbit of Neptune. (One astronomical unit, abbreviated A.U., is the average distance between the Earth and the Sun, or about 93 million miles.)

Understanding Sedna is a challenge because its orbit is far away from the gravitational influence of other planets in our solar system. However, the gravity of a passing star can pull objects beyond the orbit of Neptune, in the Kuiper Belt, into orbits like Sedna’s. Kenyon and Bromley have performed detailed computer simulations to show how this stellar fly-by likely took place.

The fly-by must have met two key requirements. First, the star must have stayed far enough away that it did not disrupt Neptune’s nearly circular orbit. Second, the encounter must have happened late enough in our solar system’s history that Sedna-like objects had time to form within the Kuiper Belt.

Kenyon and Bromley suggest that the near-collision occurred when our Sun was at least 30 million years old, and probably no more than 200 million years old. A fly-by distance of 150-200 A.U. would be close enough to disrupt the outer Kuiper Belt without affecting the inner planets.

According to the simulations, the passing star’s gravity would sweep clear the outer solar system beyond about 50 A.U., even as our Sun’s gravity pulled some of the alien planetoids into its grasp. The model explains both the orbit of Sedna and the observed sharp outer edge of our Kuiper Belt, where few objects reside beyond 50 A.U.

“A close fly-by from another star solves two mysteries at once. It explains both the orbit of Sedna and the outer edge of the Kuiper Belt,” says Bromley.

A Crowded Birthplace
But where did such a star come from, and where did it go? Since the fly-by happened more than 4 billion years ago, any suspects have long since escaped the Sun’s neighborhood. There is no practical way to find the culprit today.

The visitor’s origin may seem equally mystifying because the Sun currently lives in a sparse region of the Milky Way. Our closest neighbor is a distant 4 light-years away, and stellar close encounters are correspondingly rare. However, a near-collision would be much more likely for a young Sun if it were born in a dense star cluster, as recent evidence suggests.

“We believe that 90 percent of all stars form in clusters with a few hundred to a few thousand members,” says astronomer Charles Lada (Harvard-Smithsonian Center for Astrophysics). “The denser the cluster, the more likely the chance for an encounter between member stars.”

“This work is an important piece of evidence that the Sun formed in near proximity to other stars,” he adds.

Searching for Adopted Worlds
Kenyon and Bromley’s simulations indicate that thousands or possibly millions of alien Kuiper Belt Objects were stripped from the passing star. However, none have yet been positively identified. Sedna is probably homegrown, not captured. Among the known Kuiper Belt Objects, an icy rock dubbed 2000 CR105 is the best candidate for capture given its unusually elliptical and highly inclined orbit. But only the detection of objects with orbits inclined more than 40 degrees from the plane of the solar system will clinch the case for the presence of extrasolar planets in our backyard.

Kenyon and Bromley’s next goal is to estimate the sky density of captured objects so that they can make a survey to find such adopted worlds.

“In principle, large telescopes like the MMT Telescope [a joint Smithsonian/University of Arizona observatory] can find them if they’re numerous enough,” says Kenyon.

The calculations reported here were made using about 3,000 cpu-days of computer time at the supercomputing center at the Jet Propulsion Laboratory, Pasadena, Calif.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

Original Source: Harvard CfA News Release

Posted on by Fraser Cain

Knots in Saturn’s Rings

An intriguing knotted ringlet within the Encke Gap is the main attraction in this Cassini image. The Encke Gap is a small division near the outer edge of Saturn’s rings that is about 300 kilometers (190 miles) wide. The tiny moon Pan (20 kilometers, or 12 miles across) orbits within the gap and maintains it. Many waves produced by orbiting moons are visible.

The image was taken in visible light with the Cassini spacecraft narrow angle camera on Oct. 29, 2004, at a distance of about 807,000 kilometers (501,000 miles) from Saturn. The image scale is 4.5 kilometers (2.8 miles) per pixel.

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 Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

For more information about the Cassini-Huygens mission, visit 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

Interview with Michiel Min

Michiel Min is a research student at the Astronomical Institute, University of Amsterdam, who carried out much of the data analysis behind the current ESO release, see: Ingredients are There to Make Rocky Planets. Michiel was able to talk with Universe Today in between his studies.

Universe Today: Do your findings help to explain the origin of our own solar system in better detail?

Michiel Min: The timescale of planet formation is still under debate. Our findings provide evidence that the small dust grains are already growing after a billion years. Our observations do provide a unique view of the building blocks of planets. It is clear from our findings that the building blocks of Earth-like planets, close to the star, are crystals (crystalline silicates), while the building blocks of the planets further out, are amorphous silicates. Also we see that the growth of dust grains seems to go easier closer to the star.

Have your observations provided an answer as to how these planetary systems around giant stars may have formed?

The main reason that only giant planets in close orbits have been found has to do with the way of detecting these systems. Taking into account the gravitational pull of the planet on the star does this. Most likely, these planetary systems formed in a similar way as our own solar system. However, in these systems, most likely, the planet has moved inwards due to friction in the disk. If a planet forms very close to the star, it is more likely that it will be a rockier, earth-like planet since its atmosphere will greatly evaporate. Detecting smaller, earth-like planets directly is very hard. At the moment, planet-finders like Darwin are being build to search, in a very clever way, for the signal of Earth-like planets. Our findings give us a look in the birthplace of these planets.

So, how close would a giant planet need to be to its parent star for its atmosphere not to evaporate away?

This depends all on the mass of the planet itself and the temperature of the star. Most likely, giant planets only form at distances beyond ~5 AU [750 million kilometres] around a solar type star. But this is only a very rough number. If one considers for example Pluto, which is a rocky planet that formed quite far away, it is clear that there is not a simple answer to this.

Michiel, could you please say a little about yourself, and how you became interested in astronomy?

Yes, I am a PhD student at the University of Amsterdam. I will finish my PhD in April 2005. I have always been interested in science and how nature works. I studied physics in Amsterdam, at the Free University. After this, I got interested in astronomy because it is one of the few fields in physics where you meet all the extremes of nature. I think this provides a unique challenge for the mind. The study of planetary systems is one of the most down-to-earth subjects in astronomy. It is directly related to our own Earth. I think the question ‘what created this planet?’ is fascinating. Also, the question how planetary systems form, can provide us with an answer to how unique our own solar system is, and how easy one forms a planet like the Earth around other stars.

Looking toward the future, how long do you think it will be before astronomers have the technical ability to detect earth-like planets?

There are currently two project running to make instruments for detecting planets: DARWIN (ESA) and Terrestrial Planet Finder (NASA). Both missions are planned for launch in the year 2014. Both these missions should be able to detect Earth-like planets.

I think we are in a very exciting time in that respect. Our findings imply that all the materials to form Earth-like planets are available in the regions where liquid water can exist. Also, the process of dust growth has started its way to forming larger bodies. In my opinion, this implies that it is very likely that the planet finders of ESA and NASA will detect planets around solar type stars. Our understanding of Venus, the Earth and Mars, puts nice constraints on the conditions we can expect on these planets, and if these conditions support the possibility of life. Therefore I hope, and think, the question if our solar system is unique or not, will be answered in the coming 10-15 years.

This research project was a collaboration with the Astronomical Institute of the University of Amsterdam, The Netherlands (NOVA PR) and the Max-Planck-Institute f?r Astronomie (Heidelberg, Germany (MPG PR). The Amsterdam team consists of Roy van Boekel, Michiel Min, Rens Waters, Carsten Dominik and Alex de Koter.

By Science Correspondent Richard Pearson.

Posted on by Fraser Cain

Youngest Galaxy Found

Scientists using NASA’s Hubble Space Telescope have measured the age of what may be the youngest galaxy ever seen in the universe. By cosmological standards it is a mere toddler seemingly out of place among the grown-up galaxies around it. Called I Zwicky 18, it may be as young as 500 million years old (so recent an epoch that complex life had already begun to appear on Earth). Our Milky Way galaxy by contrast is over 20 times older, or about 12 billion years old, the typical age of galaxies across the universe. This “late-life” galaxy offers a rare glimpse into what the first diminutive galaxies in the early universe look like.

The galaxy is a member of a catalog of 30,000 nearby galaxies that Swiss astronomer Fred Zwicky assembled in the 1930’s by photographing the entire northern sky. Though astronomers have long suspected that this galaxy was a youngster, due to its primordial chemical makeup, Hubble’s exquisite sensitivity allowed astronomers to do a reliable census of the total stellar population in the galaxy. This allowed them to reliably identify the oldest stars inhabiting the galaxy, thereby setting an upper limit on the galaxy’s age.

The baby galaxy managed to remain in an embryonic state as a cold gas cloud of primeval hydrogen and helium for most of the duration of the universe’s evolution. As innumerable galaxies blossomed all over space this late-bloomer did not begin active star formation until some 13 billion years after the Big Bang, and went through a sudden first starburst only some 500 million years ago.

Located only 45 million light-years away ? much closer than other young galaxies in the nearly 14 billion light-year span of the universe ? I Zwicky 18 might represent the only opportunity for astronomers to study in detail the building blocks from which galaxies are formed. It remains a puzzle why the gas in the dwarf galaxy, in contrast to that in other galaxies, took so long ? nearly the age of the universe ? to collapse under the influence of gravity to form its first stars.

“I Zwicky 18 is a bona fide young galaxy,” said Trinh Thuan, professor of astronomy at the University of Virginia, who co-authored the study with Yuri Izotov from the Kiev Observatory. “This is extraordinary because one would expect young galaxies to be forming only around the first billion years or so after the Big Bang, not some 13 billion years later. And young galaxies were expected to be very distant, at the edge of the observable universe, but not in the local universe,” Izotov said.

The finding, reported in the December 1 issue of the Astrophysical Journal, provides a new insight into how galaxies first formed. The galaxy I Zwicky 18 offers a glimpse of what the early Milky Way may have looked like 13 billion years ago. Another set of Hubble observations by a different team give a slightly older age of 1 billion years to the galaxy, still keeping it a comparative newborn. Goran Ostlin of Stockholm Observatory, and Mustapha Mouhcine of the University of Nottingham, used Hubble’s Near Infrared Camera and Multi-Object Spectrometer to find a population of cool red stars, which are slightly older than the stars seen by the Advanced Camera for Surveys Camera. The results are to be published in Astronomy & Astrophysics.

To prove that I Zwicky 18 is a new galaxy, Thuan and Izotov needed to show that it was devoid of stars from the first several billion years after the Big Bang, the period when a large fraction of stars in the universe were formed. Though astronomers had suspected that the galaxy was exceptionally young, they had to wait for Hubble to provide the needed sensitivity to detect whether or not older stars, faint red giants, existed within the dwarf galaxy. Hubble’s Advanced Camera for Surveys needed a very long exposure, requiring 25 telescope orbits to look for the faintest stars in the galaxy. The presence of old stars in the galaxy would have indicated that the galaxy itself was old, like all other known galaxies in the universe.

Large galaxies such as the Milky Way are thought to grow hierarchically, with smaller galaxies merging into bigger galaxies, like tributaries merging into large rivers. I Zwicky 18 is prototypical of this early population of small dwarf galaxies. “These building block dwarf galaxies are too faint and too small to be studied without the most sensitive instruments even in the local universe, let alone in the far reaches of the cosmos,” Thuan said.

Further evidence for the youth of I Zwicky 18 is the fact that its interstellar gas is “nearly pristine,” Thuan said, and composed mostly of hydrogen and helium, the primary two light elements created in the Big Bang, during the first three minutes of the universe’s existence. The dwarf galaxy includes only a sprinkling of the other heavier elements such as carbon, nitrogen, or oxygen that are created later as stars develop. The near absence of such heavy elements suggests that much of the primordial gas in the dwarf galaxy has not managed to form stars that subsequently manufacture heavy elements.

Original Source: Hubble News Release