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Dead stars surrounded by fields of dust from pulverized asteroids may seem to make up a forbidding and ominous picture, but researchers who studied six such star systems say the dust should actually fuel the optimism of people who dream of finding extraterrestrial life. The dust’s composition suggests that rocky planets like our own Earth may be common in the universe, researchers say, which ups the chance that life as we know it has evolved somewhere out there.

The dust in question was found surrounding small, dense white dwarf stars. As stars like our own sun near the end of their life, they puff up into red giants that consume their innermost planets and jostle the orbits of outer planets and asteroids. Eventually the stars blow off their outer layers and shrink down into white dwarfs. Occasionally, a perturbed asteroid will wander too close to the white dwarf, whose gravity rips the rocky body to shreds, forming debris [SPACE.com].

That debris is what researchers studied with NASA’s Spitzer Space Telescope. By viewing the stars through a spectrograph, which separates out light from different wavelengths, the scientists were able to observe the telltale signatures of certain chemicals in the light. Since that starlight is passing through the film of the asteroid debris, the light picked up signatures of the asteroids’ composition, too [Wired News]. Lead researcher Michael Jura announced at the ongoing American Astronomical Society meeting that the composition of the asteroid dust was remarkably similar to that of the rocky planets in our solar system.

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In another promising sign that primitive life could have once existed on the surface of Mars, researchers have found deposits of a mineral that suggest that the planet once had life-friendly bodies of liquid water. The mineral, carbonate, has previously been detected in only trace quantities on Mars, but new data from the Mars Reconnaissance Orbiter’s spectrometer shows deposits in a rock outcropping in a region of valleys called the Nili Fossae. Since acidic conditions can prevent carbonates from forming, the discovery suggests that the rocks were created in neutral-pH water that might have provided a cosy habitat for life [New Scientist].

Water ice currently exists on Mars, and over the past few years researchers have accumulated evidence of liquid lakes and streams in the planet’s distant past. Most evidence has pointed to a period when water on the planet’s surface formed clay-rich minerals, followed by a time of drier conditions, when salt-rich, acidic water affected much of the planet. These later conditions would have proven difficult for any Martian life — if it ever existed — to endure or to leave any traces for scientists to find. Because carbonates dissolve quickly in acid, finding them shows at least some areas of the planet escaped the acid bath [SPACE.com].

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The space probe Cassini, our emissary to Saturn and its fascinating satellites, has made several new discoveries that lend further credence to the idea that microbial life could evolve on the icy moon Enceladus or the moon Titan, with its lakes of methane. During a flyby of Enceladus Cassini snapped pictures of the moon’s surface and the cracks in its icy crust from which jets of water vapor routinely burst upward. The new pictures suggest that the cracks form when the crust splits and spreads apart in a way that is similar to the mid-ocean ridges central to the tectonic system on our own planet. On Earth the spreading of the sea floor is driven by molten rock; Nasa scientists speculate that the liquid beneath the south pole of Enceladus may be water. “Bit by bit, we’re accumulating the evidence that there is liquid water on Enceladus” [Telegraph], said Cassini scientist Carolyn Porco.

Enceladus is already known to have some of the fundamental chemistry required to make and sustain life. Liquid water currently is the major missing ingredient. Dr Porco commented: “We first discovered this region in early 2005 and now it’s nearly four years later, so it’s still kind of brand new; but already there are some of us who really want to go back with a spacecraft that focuses on the south pole of Enceladus and investigates whether or not it is a site of either pre-biotic or biotic processes” [BBC News].

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A sugar molecule essential to life as we know it has been found in the far reaches of the Milky Way, scientists report. Astronomers working with the IRAM radio dish array in France report the presence of glycolaldehyde—a simple sugar found in RNA—in a region of our galaxy known to churn out stars. The molecule appears to have formed with all of the other stuff that makes up planets, suggesting that many other worlds are seeded with some of life’s ingredients right from birth [ScienceNOW Daily News].

Glycoladehyde is a building block of ribose, a component of RNA. Many scientists believe RNA preceded DNA in vesting the earliest forms of life with reproductive capabilities; thus the finding of glycoladehyde has particular significance for those searching for extraterrestrial life. The astronomers detected radio and microwave signatures of glycolaldehyde within the core of what appears to be a coalescing disk of dust and gas in a star-forming region called G31.41+0.31, about 26,000 light-years away. The sugar molecule can apparently form in a simple reaction between carbon monoxide molecules and dust grains [ScienceNOW Daily News]. The astronomers believe the molecules they see are a few hundred thousand years old.

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When NASA’s Cassini spacecraft swooped past Saturn’s moon Enceladus last year, it got a close-up view of the water vapor and ice plumes that stream away from the small moon. After analyzing the data, researchers say the evidence suggests that the material in the plumes originates as liquid water trapped beneath the moon’s icy surface, which increases the possibility that microbial, extraterrestrial life could exist in the lakes. “We think liquid water is necessary for life and there is more evidence that there is liquid water there,” said lead researcher Candice Hansen…. Scientists are aware of only three places where liquid water exists near the surface of a planet or other body - Earth, Jupiter’s moon Europa and now Enceladus [Telegraph].

Researchers identified four distinct jets within the plume where the water vapor appears to be traveling faster than 1,300 miles per hour. Such high speeds imply that the jets are fed by pressurised water vapour that shoots through narrow openings - which act like rocket nozzles - in the moon’s icy surface. The simplest way to generate such pressures is by evaporating a reservoir of liquid water that lies close to the moon’s surface [New Scientist], researchers say.

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For the first time, carbon dioxide has been detected in the atmosphere of an exoplanet, astronomers working with the Hubble Space Telescope report. Although the Jupiter-sized planet, which closely orbits the star HD 189733 about 63 light-years from Earth, is much too hot to support life, scientists are hailing the discovery as an exciting technical achievement. “In that context, the carbon dioxide measurement constitutes a dress rehearsal …for our long-term goal of trying to detect signs of life or signs of habitability on terrestrial-mass planets or super Earths in the habitable zone,” [Science News] says Mark Swain of NASA’s Jet Propulsion Laboratory.

Researchers deduced the presence of carbon dioxide by measuring the planet’s light spectrum with the Hubble’s Near Infrared Camera and Multi-Object Spectrometer (NICMOS). To isolate the light spectrum coming from the planet, researchers used a method known as “secondary transit.” This involves recording the light spectrum of the planet and its star, and then measuring the spectrum of the star alone while the planet is hidden behind it. The difference of the two spectra is the spectrum of the light coming directly from the planet [Nature News]. Unlike previous measurements that focused on the mid-infrared range, NICMOS took measurements in the near-infrared range, enabling detection of the carbon dioxide signature.

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New data from NASA’s Mars Odyssey orbiter supports the long-debated theory that Mars once (or twice) had vast frozen oceans on its surface. The location of certain mineral deposits suggests massive erosion and ancient shorelines. A group of researchers now believes Mars had at least two oceans - one about three and a half billion years ago that was 20 times the size of the Mediterranean and a smaller one about two billions years ago. “These were not like the oceans we know,” says [researcher Victor] Baker. “These were transient bodies that existed long enough to accumulate sediment”, but were not present for billions of years of geologic history, as Earth’s oceans have been [New Scientist].

The Mars Odyssey orbiter identified the mineral deposits using a gamma-ray spectrometer, which can detect elements a third of a metre below Mars’s surface. It found enriched potassium, thorium and iron, lying in shoreline-type patterns, where researchers already suspected water used to lie [Canwest News Service]. Until now, however, their suspicions were mainly based on geographical features such as smooth plains surrounded by higher, more rugged terrain. The new data, to be published in Planetary and Space Science, shows minerals heavily concentrated in the soil below the proposed shoreline and less concentrated above, suggesting erosion of sediments into a large body of water. But study coauthor James Dohm says the new evidence isn’t a smoking gun: “It’s consistent with this ocean potential - it doesn’t confirm it, necessarily,” Dohm said. “I think it’s a significant piece of the puzzle” [Tucson Citizen].

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Opal has been detected on Mars by NASA’s Mars Reconnaissance Orbiter (MRO), an encouraging sign that water may have existed on the planet as recently as two billion years ago. The opal, a hydrated silicate, is the youngest hydrated mineral yet to be found on the 4.5 billion-year-old planet and significantly widens the window of time that Mars is believed to have supported water. “This is an exciting discovery because it extends the time range for liquid water on Mars, and the places where it might have supported life,” [SPACE.com] said team leader Scott Murchie.

Hydrated minerals require water to form and two types have been found on the Red Planet before. The oldest hydrated materials are clay-like phyllosilicates, which formed more than 3.5 billion years ago when volcanic rocks bathed for long periods of time in water. Later, hydrated sulfates formed when salty and occasionally acidic water evaporated [Discovery News]. The newly found hydrated silicates, described in Geology [subscription required], appeared even later, as acidic liquid water slowly altered materials created from volcanic activity and meteorite impacts. Team member Ralph Milliken explains that the water “was there long enough to alter some of the rocks…. It wasn’t an overnight process” [SPACE.com].

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Almost two miles beneath the earth’s surface in a South African goldmine, researchers have found a new species of bacteria that lives in total isolation from any other organism. The discovery offers the first known example of an ecosystem that isn’t a complex web of different life forms, but is instead hosts just one self-sufficient species. The bacteria, Desulforudis audaxviator, is able to extract all its food and energy directly from the surrounding water and rocks, and researchers say the independent microbe offers a glimpse of the shape life could take on other planets.

Researchers wanted to know what organisms were living in the mine’s deep fissures, a habitat completely devoid of light and oxygen, so they analyzed the genes present in a water sample to determine what species lived there. They filtered a total of 5,600 liters of mine water to get their sample, which gave other microbes plenty of opportunities to make themselves known. Of the DNA sequences obtained from this sample, over 99.9 percent were from this single species; over half of the remainder were obvious contaminants from their own lab [Ars Technica].

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Our sun, which lies 26,000 light years from the center of the the Milky Way, may have been born in a different part of the galaxy and later migrated to its current position, about halfway towards the galaxy’s outer edge. A new study defies the conventional wisdom that stars spend their entire lifespans in the same galactic region, and calls into question astronomers’ theory that galaxies have certain fixed “habitable zones” where life is more likely to evolve.

“Our view of the extent of the habitable zone is based in part on the idea that certain chemical elements necessary for life are available in some parts of a galaxy’s disk but not others,” said [lead researcher] Rok Roskar…. “If stars migrate, then that zone can’t be a stationary place” [Astrobiology Magazine].

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The Cassini spacecraft that has been busily exploring Saturn and its moons swooped to within 30 miles of the tiny moon Enceladus yesterday, and has already begun sending back images of the fissures near the moon’s south pole. The icy moon, which is about 310 miles wide, has tantalized scientists with geyser-like eruptions of icy water vapor that were first spotted in 2005…. The eruptions produce a halo of frozen water vapor and gas that replenishes Saturn’s E-ring as Enceladus circles the planet [SPACE.com].

The Cassini took images of the fissures, which scientists call the moon’s “tiger stripes,” in the infrared spectrum as well, to gain further information about the temperatures in the vents; previous studies had shown temperatures there can reach a relatively balmy -135 degrees Fahrenheit, which is 200 degrees Fahrenheit warmer than the rest of the moon. While the material sprayed out of the fissures consists of frozen water vapor, scientists disagree on whether an internal ocean of [liquid] water, life’s crucial ingredient, hides within the tiny moon [USA Today].

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NASA’s Cassini spacecraft has discovered a liquid lake the size of Earth’s Lake Ontario on the south pole of Titan, Saturn’s largest moon. Researchers say that Cassini’s instruments reveal that the chilly reservoir … Titan, is composed of a key component of crude oil — liquid ethane [Science News].

The new find supports the common belief that Titan is a promising place to look for extraterrestrial life. Some astrobiologists have speculated that life could develop in the moon’s hydrocarbon lakes, although it would have to be substantially different from known life on Earth, which requires liquid water [Wired News].

The Cassini orbiter has racked up a number of accomplishments since it began investigating Saturn and its moons in 2004, but its most exciting missions have focused on Titan, where the thick nitrogen and methane atmosphere resembles the atmosphere that existed on primordial Earth.

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Mars wasn’t always the cold, dry, and dusty planet that NASA’s rovers and landers are currently exploring. By mapping the mineral composition of wide swaths of the planet’s surface, researchers have discovered that parts of Mars once coursed with liquid water, which increases the possibility that it supported microbial life.

Using NASA’s Mars Reconnaissance Orbiter, researchers searched for traces of phyllosilicates, or clay-like minerals that preserve a record of water’s interaction with rocks. They found phyllosilicates in thousands of places, in valleys, dunes and craters in the ancient southern highlands, pointing to an active role by water in Mars’s earliest geological era, the Noachian period, 4.6 to 3.8 billion years ago [AFP].

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It is considered by many engineers and scientists as the “Holy Grail” of robotic red planet exploration: a Mars Return Sample mission [SPACE.com]. Now, an international group of researchers from NASA and the European Space Agency (ESA) have produced a report explaining how they could get a robotic explorer to scoop up rocks from the Martian surface, and then bring them back to Earth to let humans touch a piece of Mars.

Scientists say it would cost between $4.5 billion and $8 billion and would require the cooperation of several space agencies, but they also say there’s no reason not to do it.

The Soviet Union successfully returned rocks to Earth from the Moon during robotic missions in the 1970s. But since then, such complex sample-return missions have been regarded as prohibitively complicated and expensive [ABC News]. Now, space agencies say that bringing rocks back from Mars would serve as an intermediary step on the path to sending a manned expedition to our neighbor planet. Says researcher Monica Grady: “If you can’t bring a rock back you are not going to be able to bring people back” [The Guardian]. NASA and the ESA are expected to decide whether to pursue the mission in November.

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The Mars Phoenix Lander may deserve a Nobel Prize by the time it’s through. Just a week after the robot explorer took the first pictures of water ice on the on Mars, NASA scientists have a new announcement: The Phoenix has analyzed a scoop of soil, and found that the Martian dirt has the necessary ingredients to support plant life. Researchers say the soil they tested is slightly alkaline, not harshly acidic as feared, and that it contains the mineral nutrients potassium, magnesium, and sodium.

“There’s nothing about it that would preclude life. In fact, it seems very friendly,” said mission scientist Samuel P. Kounaves of Tufts University. “We were flabbergasted.” Kounaves said that the soil was similar to what people would find in their back yards on Earth and that if organic material was added, “you could probably grow asparagus, but not strawberries” [The Washington Post].

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