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  • richardmitnick 5:40 pm on November 18, 2018 Permalink | Reply
    Tags: "New Arecibo Observatory Message Challenge Announced", Arecibo message 1974, Astrobiology Magazine, , , ,   

    From Astrobiology Magazine: “New Arecibo Observatory Message Challenge Announced” 

    Astrobiology Magazine

    From Astrobiology Magazine

    Nov 18, 2018

    In 1974, the Arecibo Observatory made history by beaming the most powerful radio message into deep space ever made.

    This radio message was transmitted toward the globular cluster M13 using the Arecibo telescope in 1974. Image Credit Arne Nordmann (norro) Wikipedia

    The famous Arecibo Message was designed by the AO 74’s staff, led by Frank Drake, and with the help of the astronomer and famed science communicator Carl Sagan. It contained information about the human race and was intended to be our intergalactic calling card.

    Frank Drake with his Drake Equation. Credit Frank Drake

    Carl Sagan NASA/JPL

    “Our society and our technology have changed a lot since 1974,” says Francisco Cordova, the director of the NSF-funded Arecibo Observatory. “So, if we were assembling our message today, what would it say? What would it look like? What one would need to learn to be able to design the right updated message from the earthlings? Those are the questions we are posing to young people around the world through the New Arecibo Message – the global challenge.”

    1
    NAIC Arecibo Observatory operated by University of Central Florida, Yang Enterprises and UMET, Altitude 497 m (1,631 ft).

    The NSF-funded facility, which is home to the largest fully operational radar telescope on the planet, will launch its online competition later today on the 44th anniversary of the original Arecibo message. Check out the observatory’s website after 1 p.m. for details and today’s Google doodle for more information about the first message.

    But this will be no simple task. In order to get started, teams of up to 10 students in grades kindergarten through college, must decode various clues that will be released online. Like a Chinese puzzle box, teams must learn about Space Sciences, break coded messages and solve brain-puzzles to qualify, get instructions, register and then submit their entries. Arecibo will post its first puzzle on its website and social media channels this afternoon (Nov. 16).

    This challenge gives teams nine months to complete their designs. A winner will be announced during the Arecibo Observatory Week activities planned for 2019, which includes the special celebration of the 45thanniversary of the original Arecibo Message.

    “We have quite a few surprises in store for participants and we will be sharing more details as the competition progresses,” Cordova says. “We can’t wait to see what our young people across the globe come up with.”

    The Arecibo Observatory is operated by the University of Central Florida (UCF) in partnership with Sistema Ana G. Mendez Universidad Metropolitana and Yang Enterprises Inc., under a cooperative agreement with the National Society of Sciences (NSF). The planetary radar program is supported by NASA’s Near Earth Object Observation Program.

    See the full article here .


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  • richardmitnick 12:41 pm on November 4, 2018 Permalink | Reply
    Tags: Astrobiology Magazine, , , , , New Insights on Comet Tails Are Blowing in the Solar Wind   

    From Astrobiology Magazine: “New Insights on Comet Tails Are Blowing in the Solar Wind” 

    Astrobiology Magazine

    From Astrobiology Magazine

    Nov 3, 2018

    1
    Comet McNaught over the Pacific Ocean. Image taken from Paranal Observatory in January 2007. Credits: ESO/Sebastian Deiries

    ESO VLT at Cerro Paranal in the Atacama Desert, •ANTU (UT1; The Sun ),
    •KUEYEN (UT2; The Moon ),
    •MELIPAL (UT3; The Southern Cross ), and
    •YEPUN (UT4; Venus – as evening star).
    elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo

    Engineers and scientists gathered around a screen in an operations room at the Naval Research Laboratory in Washington, D.C., eager to lay their eyes on the first data from NASA’s STEREO spacecraft. It was January 2007, and the twin STEREO satellites — short for Solar and Terrestrial Relations Observatory — which had launched just months before, were opening their instruments’ eyes for the first time.

    NASA/STEREO spacecraft

    Artist’s conceptual drawing of the two STEREO spacecraft in orbit around the sun.

    First up: STEREO-B. The screen blinked, but instead of the vast starfield they expected, a pearly white, feathery smear — like an angel’s wing — filled the frame. For a few panicky minutes, NRL astrophysicist Karl Battams worried something was wrong with the telescope. Then, he realized this bright object wasn’t a defect, but an apparition, and these were the first satellite images of Comet McNaught. Later that day, STEREO-A would return similar observations.

    Comet C/2006 P1 — also known as Comet McNaught, named for astronomer Robert McNaught, who discovered it in August 2006 — was one of the brightest comets visible from Earth in the past 50 years. Throughout January 2007, the comet fanned across the Southern Hemisphere’s sky, so bright it was visible to the naked eye even during the day. McNaught belongs to a rarefied group of comets, dubbed the Great Comets and known for their exceptional brightness.

    Setting McNaught apart further still from its peers, however, was its highly structured tail, composed of many distinct dust bands called striae, or striations, that stretched more than 100 million miles behind the comet, longer than the distance between Earth and the Sun. One month later, in February 2007, an ESA (European Space Agency) and NASA spacecraft called Ulysses would encounter the comet’s long tail.

    NASA/ESA Ulysses

    “McNaught was a huge deal when it came because it was so ridiculously bright and beautiful in the sky,” Battams said. “It had these striae — dusty fingers that extended across a huge expanse of the sky. Structurally, it’s one of the most beautiful comets we’ve seen for decades.”

    2
    An illustration of the six-tailed Great Comet of 1744, observed before sunrise on March 9, 1744, from Les Comètes, by Amédée Guillemin. Credits: Paris Observatory

    How exactly the tail broke up in this manner, scientists didn’t know. It called to mind reports of another storied comet from long ago: the Great Comet of 1744, which was said to have dramatically fanned out in six tails over the horizon, a phenomenon astronomers then couldn’t explain. By untangling the mystery of McNaught’s tail, scientists hoped to learn something new about the nature of comets — and solve two cosmic mysteries in one.

    A key difference between studying comets in 1744 and 2007 is, of course, our ability to do so from space. In addition to STEREO’s serendipitous sighting, another mission, ESA/NASA’s SOHO — the Solar and Heliospheric Observatory — made regular observations as McNaught flew by the Sun. Researchers hoped these images might contain their answers.

    ESA/NASA SOHO


    ESA/NASA SOHO

    Now, years later, Oliver Price, a planetary science Ph.D. student at University College London’s Mullard Space Science Laboratory in the United Kingdom, has developed a new image-processing technique to mine through the wealth of data. Price’s findings — summarized in a recently published Icarus paper — offer the first observations of striations forming, and an unexpected revelation about the Sun’s effect on comet dust.

    Comets are cosmic crumbs of frozen gas, rock and dust left over from the formation of our solar system 4.6 billion years ago — and so they may contain important clues about our solar system’s early history. Those clues are unlocked, as if from a time capsule, every time a comet’s elliptical orbit brings it close to the Sun. Intense heat vaporizes the frozen gases and releases the dust within, which streams behind the comet, forming two distinct tails: an ion tail carried by the solar wind — the constant flow of charged particles from the Sun — and a dust tail.

    Understanding how dust behaves in the tail — how it fragments and clumps together — can teach scientists a great deal about similar processes that formed dust into asteroids, moons and even planets all those billions of years ago. Appearing as one of the biggest and most structurally complex comets in recent history, McNaught was a particularly good subject for this type of study. Its brightness and high dust production made it much easier to resolve the evolution of fine structures in its dust tail.

    Price began his study focusing on something the scientists couldn’t explain. “My supervisor and I noticed weird goings-on in the images of these striations, a disruption in the otherwise clean lines,” he said. “I set out to investigate what might have happened to create this weird effect.”

    The rift seemed to be located at the heliospheric current sheet, a boundary where the magnetic orientation, or polarity, of the electrified solar wind changes directions. This puzzled scientists because while they have long known a comet’s ion tail is affected by the solar wind, they had never seen the solar wind impact dust tails before.

    NASA Dynamic Solar System – the actual effects of climate change. Heliospheric current sheet and interplanetary magnetic field

    5
    The Sun’s magnetic field, which is embedded in the solar wind, permeates the entire solar system. The current sheet — where the magnetic field changes polarity —spirals out from near the solar equator like a wavy skirt around a ballet dancer’s waist. Credits: NASA’s Goddard Space Flight Center

    Dust in McNaught’s tail — roughly the size of cigarette smoke — is too heavy, the scientists thought, for the solar wind to push around. On the other hand, an ion tail’s miniscule, electrically charged ions and electrons easily sail along the solar wind. But it was difficult to tell exactly what was going on with McNaught’s dust, and where, because at roughly 60 miles per second, the comet was rapidly traveling in and out of STEREO and SOHO’s view.

    “We got really good data sets with this comet, but they were from different cameras on different spacecraft, which are all in different places,” Price said. “I was looking for a way to bring it all together to get a complete picture of what’s happening in the tail.”

    His solution was a novel image-processing technique that compiles all the data from different spacecraft using a simulation of the tail, where the location of each tiny speck of dust is mapped by solar conditions and physical characteristics like its size and age, or how long it’d been since it’d flown off the head, or coma, of the comet. The end result is what Price dubbed a temporal map, which layers information from all the images taken at any given moment, allowing him to follow the dust’s movements.

    The temporal maps meant Price could watch the striations form over time. His videos, which cover the span of two weeks, are the first to track the formation and evolution of these structures, showing how dust fragments topple off the comet head and collapse into long striations.

    But the researchers were most excited to find that Price’s maps made it easier to explain the strange effect that drew their attention to the data in the first place. Indeed, the current sheet was the culprit behind the disruptions in the dust tail, breaking up each striation’s smooth, distinct lines. For the two days it took the full length of the comet to traverse the current sheet, whenever dust encountered the changing magnetic conditions there, it was jolted out of position, as if crossing some cosmic speed bump.

    “It’s like the striation’s feathers are ruffled when it crosses the current sheet,” University College London planetary scientist Geraint Jones said. “If you picture a wing with lots of feathers, as the wing crosses the sheet, lighter ends of the feathers get bent out of shape. For us, this is strong evidence that the dust is electrically charged, and that the solar wind is affecting the motion of that dust.”

    Scientists have long known the solar wind affects charged dust; missions like Galileo, Cassini and Ulysses [above] watched it move electrically charged dust through the space near Jupiter and Saturn. But it was a surprise for them to see the solar wind affect larger dust grains like those in McNaught’s tail — about 100 times bigger than the dust seen ejected from around Jupiter and Saturn — because they’re that much heavier for the solar wind to push around.

    NASA/Galileo 1989-2003

    NASA/ESA/ASI Cassini-Huygens Spacecraft

    With this study, scientists gain new insights into long-held mysteries. The work sheds light on the nature of striated comet tails from the past and provides a crucial lens for studying other comets in the future. But it also opens a new line of questioning: What role did the Sun have in our solar system’s formation and early history?

    “Now that we see the solar wind changed the position of dust grains in McNaught’s tail, we can ask: Could it have been the case that early on in the solar system’s history, the solar wind played a role in organizing ancient dust as well?” Jones said.

    See the full article here .


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  • richardmitnick 9:05 pm on October 23, 2018 Permalink | Reply
    Tags: Astrobiology Magazine, , , , , Planetary nebula M3-1, The two stars are so close together that they cannot be resolved from the ground so instead the presence of the second star is inferred from the variation of their observed combined brightness – mos, Two stars in a binary pair that complete an orbit around each other in a little over three hours   

    From Astrobiology Magazine:’Ultra-close stars discovered inside a planetary nebula” 

    Astrobiology Magazine

    From Astrobiology Magazine

    Oct 23, 2018

    1
    An image obtained with the Hubble Space Telescope of the planetary nebula M3-1, the central star of which is actually a binary system with one of the shortest orbital periods known. Credit: David Jones – IAC

    NASA/ESA Hubble Telescope

    An international team of astronomers have discovered two stars in a binary pair that complete an orbit around each other in a little over three hours, residing in the planetary nebula M3-1. Remarkably, the stars could drive a nova explosion, an entirely unexpected event based on our current understanding of binary star evolution. The team, led by David Jones of the Instituto Astrofisica de Canarias and the Universidad de La Laguna, report their findings in Monthly Notices of the Royal Astronomical Society: Letters.

    Planetary nebulae are the glowing shells of gas and dust formed from the outer layers of stars like our own Sun, which they throw off during the final stages of their evolution. In many cases, interaction with a nearby companion star plays an important role in the ejection of this material and the formation of the elaborate structures seen in the resulting planetary nebulae.

    The planetary nebula M3-1 is located in the constellation of Canis Major, at a distance of roughly 14,000 light years. M3-1 was a firm candidate to host a binary central star, as its structure with prominent jets and filaments is typical of these binary star interactions.

    Using the telescopes of the European Southern Observatory (ESO) [no telescopes identified] in Chile, Jones’s team looked at M3-1 over a period of several years. In the process they discovered and studied the binary stars in the centre of the nebula.

    ESO/Cerro LaSilla, 600 km north of Santiago de Chile at an altitude of 2400 metres.


    ESO VLT at Cerro Paranal in the Atacama Desert, •ANTU (UT1; The Sun ),
    •KUEYEN (UT2; The Moon ),
    •MELIPAL (UT3; The Southern Cross ), and
    •YEPUN (UT4; Venus – as evening star).
    elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo

    “We knew M3-1 had to host a binary star, so we set about acquiring the observations required to prove this and to relate the properties of the nebula with the evolution of the star or stars that formed it” says Brent Miszalski, researcher at the Southern African Large Telescope, and co-author of the study.

    The two stars are so close together that they cannot be resolved from the ground, so instead the presence of the second star is inferred from the variation of their observed combined brightness – most obviously by periodic eclipses of one star by the other which produce marked drops in the brightness.

    “When we began the observations, it was immediately clear that the system was a binary” explains Henri Boffin, researcher at the European Southern Observatory in Germany. “We saw that the apparently single star at the centre of the nebula was rapidly changing in brightness, and we knew that this must be due to the presence of a companion star.”

    The team discovered that the central star of the planetary nebula M3-1 has one of the shortest orbital period binary central stars known to date, at just over three hours. The ESO observations also show that the two stars – most likely a white dwarf with a low-mass main sequence companion – are almost touching.

    As a result, the pair are likely to undergo a so-called nova eruption, the result of the transfer of material from one star to the other. When this reaches a critical mass, a violent thermonuclear explosion takes place and the system temporarily increases in brightness by up to a million times.

    “After the various observing campaigns in Chile, we had enough data to begin to understand the properties of the two stars – their masses, temperatures and radii” says Paulina Sowicka, a PhD student at the Nicolas Copernicus Astronomical Center in Poland. “It was a real surprise that the two stars were so close together and so large that they were almost touching one another. A nova explosion could take place in just a few thousand years from now.”

    Theory suggests that binary stars should be well separated after the formation of a planetary nebula. It should then take a long time before they begin to interact again and events such as novae become possible.

    In 2007, astronomers observed a different nova explosion, known as Nova Vul 2007, inside another planetary nebula.

    Jones comments: “The 2007 event was particularly difficult to explain. By the time the two stars are close enough for a nova, the material in the planetary nebula should have expanded and dissipated so much that it’s no longer visible.”

    The new event adds to the conundrum, adds Jones: “In the central stars of M3-1, we’ve found another candidate for a similar nova eruption in the relatively near future.”

    The team now hope to carry out further study of the nebula and others like it, helping to shed light on the physical processes and origins of novae and supernovae, some of the most spectacular and violent phenomena in the Universe.

    See the full article here .


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  • richardmitnick 9:44 am on August 19, 2018 Permalink | Reply
    Tags: "Discovery of a structurally ‘inside-out’ planetary nebula, Astrobiology Magazine, , , , , , Planetary nebula HuBi   

    From Astrobiology Magazine: “Discovery of a structurally ‘inside-out’ planetary nebula” 

    Astrobiology Magazine

    From Astrobiology Magazine

    Aug 18, 2018

    1
    Planetary nebula HuBi 1 (left) and another planetary nebula Abell39 (right, 6800 light years away from our solar system). (HuBi 1 image adopted from Guerrero, Fang, Miller Bertolami, et al., 2018, Nature Astronomy, tmp, 112. Image credit for Abell39: The 3.5m WIYN Telescope, National Optical Astronomical Observatory, NSF.)

    NOAO WIYN 3.5 meter telescope interior


    NOAO WIYN 3.5 meter telescope at Kitt Peak, AZ, USA, Altitude 2,096 m (6,877 ft)

    The Instituto de Astrofísica de Andalucía (IAA-CSIC) in Spain, the Laboratory for Space Research (LSR) of the University of Hong Kong (HKU), and an International team comprising scientists from Argentina, Mexico and Germany have discovered the unusual evolution of the central star of a planetary nebula in our Milky Way. This extraordinary discovery sheds light on the future evolution, and more importantly, the ultimate fate of the Sun.

    The discovery of a structurally ‘inside-out’ planetary nebula — the ionized material that surrounds a white dwarf — was just reported online in Nature Astronomy. This is also the eighth research paper produced by HKU LSR with its international collaborators in the Nature journals since 2017.

    The research team believes this inverted ionization structure of the nebula is resulted from the central star undergoing a ‘born-again’ event, ejecting material from its surface and creating a shock that excites the nebular material.

    Planetary nebulae are ionized clouds of gas formed by the hydrogen-rich envelopes of low- and intermediate-mass stars ejected at late evolutionary stages. As these stars age, they typically strip their outer layers, forming a ‘wind’. As the star transitions from its red giant phase to become a white dwarf, it becomes hotter, and starts ionizing the material in the surrounding wind. This causes the gaseous material closer to the star to become highly ionized, while the gas material further out is less so.

    Studying the planetary nebula HuBi 1 (17,000 light years away and nearly 5 billion years ahead of our solar system in evolution), however, Dr Martín Guerrero et al. found the reverse: HuBi 1’s inner regions are less ionized, while the outer regions more so. Analysing the central star, with the participation of top theoretical astrophysicists, the authors found that it is surprisingly cool and metal-rich, and is evolved from a low-mass progenitor star which has a mass 1.1 times of the Sun.

    The authors suggest that the inner nebula was excited by the passage of a shockwave caused by the star ejecting matter unusually late in its evolution. The stellar material cooled to form circumstellar dust, obscuring the star; this well explains why the central star’s optical brightness has diminished rapidly over the past 50 years. In the absence of ionizing photons from the central star, the outer nebula has begun recombining — becoming neutral. The authors conclude that, as HuBi 1 was roughly the same mass as the Sun, this finding provides a glimpse of a potential future for our solar system.

    Dr Xuan Fang, co-author of the paper and a postdoctoral fellow at the HKU LSR and Department of Physics, said the extraordinary discovery resolves a long-lasting question regarding the evolutionary path of metal-rich central stars of planetary nebulae. Dr Fang has been observing the evolution of HuBi 1 early since 2014 using the Spanish flagship telescope Nordic Optical Telescope and was among the first astrophysicists to discover its inverted ionization structure.


    Nordic Optical telescope, at Roque de los Muchachos Observatory, La Palma in the Canary Islands, Spain, Altitude 2,396 m (7,861 ft)

    He said: “After noting HuBi 1’s inverted ionization structure and the unusual nature of its central star, we looked closer to find the reasons in collaboration with top theoretical astrophysicists in the world. We then came to realize that we had caught HuBi 1 at the exact moment when its central star underwent a brief ‘born-again’ process to become a hydrogen-poor [WC] and metal-rich star, which is very rare in white dwarf stars evolution.”

    Dr Fang, however, said the discovery would not alter the fate of the Earth. He remarked: “Our findings suggest that the Sun may also experience a ‘born-again’ process while it is dying out in about 5 billion years from now; but way before that event, our earth will be engulfed by the Sun when it turns into a superhot red giant and nothing living will survive.”

    HKU LSR Acting Director Professor Quentin Parker is exceptionally pleased with the findings of this international collaboration. He said: “I am delighted by this latest important contribution by Dr Xuan Fang who played a key role in this very unusual discovery of the international project. This exciting result in the area of evolved stars adds to several other impressive findings that members of the LSR have been producing over the last two years in astrophysics and planetary science research. It demonstrates yet again that the universe still has surprises for us. The LSR has an excellent and growing reputation in late-stage stellar evolution, high energy astrophysics, and planetary sciences and I expect this to continue.”

    See the full article here .


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  • richardmitnick 5:21 pm on December 18, 2017 Permalink | Reply
    Tags: Astrobiology Magazine, , , , , Major compositional differences between Earth and Mars, Mars And Earth May Not Have Been Early Neighbors   

    From astrobio.net: “Mars And Earth May Not Have Been Early Neighbors” 

    Astrobiology Magazine

    Astrobiology Magazine

    Mars And Earth May Not Have Been Early Neighbors.

    Dec 18, 2017
    Joelle Renstrom

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    A global view of Mars. Credit: NASA.

    A study published in the journal Earth and Planetary Science Letters posits that Mars formed in what today is the Asteroid Belt, roughly one and a half times as far from the Sun as its current position, before migrating to its present location.

    The assumption has generally been that Mars formed near Earth from the same building blocks, but that conjecture raises a big question: why are the two planets so different in composition? Mars contains different, lighter, silicates than Earth, more akin to those found in meteorites. In an attempt to explain why the elements and isotopes on Mars differ widely from those on Earth, researchers from Japan, the United States and the United Kingdom ran simulations to gain insights into the Red Planet’s movement within the Solar System.

    Even though the study’s simulations suggested that the most probable explanation is that Mars formed near Earth, that model doesn’t account for the compositional differences between the two planets. Thus, researchers paid particular attention to simulations consistent with the so-called Grand Tack model, which suggests that Jupiter played a major role in the formation and final orbital architecture of the inner planets. The theory holds that a newly-established Jupiter plowed a large concentration of mass towards the Sun, which contributed to the formation of Earth and Venus, while simultaneously pushing material away from Mars, accounting for the planet’s small mass (roughly 11 percent that of Earth) and the difference between the two planets’ compositions.

    In Grand Tack simulations, the researchers gleaned additional insight into Mars’ formation. A small percentage of the simulations suggested that Mars formed much farther from the Sun than it is now and that Jupiter’s gravitational pull pushed Mars into its current position.

    University of Colorado Geological Sciences professor Stephen Mojzsis, a co-author of the study, isn’t concerned by the low probability of this scenario taking place.

    “Low probability means one of two things: that we don’t have a better physical mechanism to explain Mars’ formation or in the enormous panoply of possibilities we ended up with one that is relatively rare,” he says, noting that the latter seems to be the best conclusion.

    Mojzsis also keeps such terms in perspective. “Keep in mind that rare is relative,” when it comes to space, he says, and rare outcomes do happen. What are the chances that Earth would cross orbits with the asteroid that hit the Yucatan and rendered the dinosaurs extinct?

    “Given enough time, we can expect these events,” Mojzsis says. “For example, you’ll eventually get double sixes if you roll the dice enough times. The probability is 1/36 or roughly the same as we get for our simulations of Mars’ formation.”

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    A model of our current solar system.Credit: NASA/JPL

    One implication of Mars forming farther away from the Sun is that the planet would have been colder than originally thought—perhaps too cold for liquid water or to sustain life. This theory would seem to challenge the idea that Mars was once far warmer and wetter than it is now. Mojzsis argues that there’s plenty of time in Mars’ early history for it to have been both colder and farther away and at times for for it to have experienced warm, wet periods.

    “Mars’ formation in the Asteroid Belt took place very early in Mars’ history, well before the crust stabilized and the atmosphere was established,” he says. In a paper he co-authored last year, Mojzsis concludes that late in Mars’ planetary formation it was bombarded by asteroids that formed the planet’s countless craters. Such large impacts could “melt the cryosphere and Mars’ crust to densify Mars’ atmosphere and to restart the hydrologic cycle,” Mojzsis says.

    While many scientists are beginning to embrace the idea of planetary migration, studies such as this raise additional questions regarding the planets and their histories. What is Venus’ composition and how does it compare to that of Earth? Confirmation of similarities between Venus and Earth would circumstantially support the idea that, in the Grand Tack theory, Jupiter pushed material in-system to form Earth and Venus. It would also support researchers’ theories about the formation of planets in the inner Solar System, including Mars. However, the lack of any samples, even meteorites, from Venus makes it difficult to answer that question. NASA and the Russian space agency Roscosmos have proposed the joint Venera-D mission that would send an orbiter to Venus around 2025, which may yield some clues to the planet’s composition.

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    NASA Roscomos Venera-D probe

    Mojzsis also points out that one of the problems we face is trying to understand how the giant planets formed. Jupiter, Saturn, Uranus, and Neptune couldn’t have formed where they now reside because the Outer Solar System didn’t have enough mass early on to account for these giant worlds, he says.

    It could be that the giant planets formed close together and then later moved away by the influence of their gravitational interactions. Such a theory isn’t unique to our Solar System. “We understand from direct observations via the Kepler Space Telescope and earlier studies that giant planet migration is a normal feature of planetary systems,” Mojzsis says. “Giant planet formation induces migration, and migration is all about gravity, and these worlds affected each other’s orbits early on.”

    Mojzsis’ recent work also focuses on how Jupiter ended up in its current position and how its formation corresponds with the dispersal of gas and dust from the Sun’s planet-forming disc. Little by little, scientists are gaining a greater understanding of the Solar System’s history—and of the nature of planetary formation in our galactic neighborhood.

    Mojzsis’ work was supported in part by NASA’s Exobiology and Evolutionary Biology Program and by the John Templeton Foundation-FfAME origins project.

    See the full article here .

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  • richardmitnick 9:59 am on October 18, 2015 Permalink | Reply
    Tags: , , Astrobiology Magazine, Zircons   

    From astrobio.net: “Study questions dates for cataclysms on early moon, Earth” 

    Astrobiology Magazine

    Astrobiology Magazine

    Oct 18, 2015
    No Writer Credit

    1
    The deformed lunar zircon at center was brought from the moon by Apollo astronauts. The fractures characteristic of meteorite impact are not seen in most lunar zircons, so the ages they record probably reflect heating by molten rock, not impact. Photo: Apollo 17/Nicholas E. Timms

    Phenomenally durable crystals called zircons are used to date some of the earliest and most dramatic cataclysms of the solar system. One is the super-duty collision that ejected material from Earth to form the moon roughly 50 million years after Earth formed. Another is the late heavy bombardment, a wave of impacts that may have created hellish surface conditions on the young Earth, about 4 billion years ago.

    Both events are widely accepted but unproven, so geoscientists are eager for more details and better dates. Many of those dates come from zircons retrieved from the moon during NASA’s Apollo voyages in the 1970s.

    A study of zircons from a gigantic meteorite impact in South Africa, now online in the journal Geology, casts doubt on the methods used to date lunar impacts. The critical problem, says lead author Aaron Cavosie, a visiting professor of geoscience and member of the NASA Astrobiology Institute at the University of Wisconsin-Madison, is the fact that lunar zircons are “ex situ,” meaning removed from the rock in which they formed, which deprives geoscientists of corroborating evidence of impact.

    “While zircon is one of the best isotopic clocks for dating many geological processes,” Cavosie says, “our results show that it is very challenging to use ex situ zircon to date a large impact of known age.”

    Although many of their zircons show evidence of shock, “once separated from host rocks, ex situ shocked zircons lose critical contextual information,” Cavosie says.

    The “clock” in a zircon occurs as lead isotopes accumulate during radioactive decay of uranium. With precise measurements of isotopes scientists can calculate, based on the half life of uranium, how long lead has been accumulating.

    If all lead was driven off during asteroid impact, the clock was reset, and the amount of accumulated lead should record exactly how long ago the impact occurred.

    Studies of lunar zircons have followed this procedure to produce dates from 4.3 billion to 3.9 billion years ago for the late heavy bombardment.

    2
    This highly shocked zircon, from the Vredefort Dome in South Africa, shows thin, red bands that are a hallmark of meteorite impact. Uranium-lead dating from this zircon matched the age of the rocks exposed at Vredefort, not the more recent age of impact (2 billion years). Credit: Aaron Cavosie

    To evaluate the assumption of clock-resetting by impact, Cavosie and colleagues gathered zircons near Earth’s largest impact, located in South Africa and known to have occurred 2 billion years ago. The Vredefort impact structure is deeply eroded, and approximately 90 kilometers across, says Cavosie, who is also in the Department of Applied Geology at Curtin University in Perth, Australia. “The original size, estimated at 300 kilometers diameter, is modeled to result from an impactor 14 kilometers in diameter,” he says.

    1
    Vredefort Dome

    The researchers searched for features within the zircons that are considered evidence of impact, and concluded that most of the ages reflect when the zircons formed in magma. The zircons from South Africa are “out of place grains that contain definitive evidence of shock deformation from the Vredefort impact,” Cavosie says. “However, most of the shocked grains do not record the age of the impact but rather the age of the rocks they formed in, which are about 1 billion years older.”

    The story is different on Earth, says zircon expert John Valley, a professor of geoscience at UW-Madison. “Most zircons on Earth are found in granite, and they formed in the same process that formed the granite. This has led people to assume that all the zircons were reset by impact, so the ages they get from the Moon are impact ages. Aaron is saying to know that, you have to apply strict criteria, and that’s not what people have been doing.”

    The accuracy of zircon dating affects our view of Earth’s early history. The poorly understood late heavy bombardment, for example, likely influenced when life arose, so dating the bombardment topped a priority list of the National Academy of Sciences for lunar studies. Did the giant craters on the moon form during a brief wave or a steady rain of impacts? “It would be nice to know which,” Valley says.

    “The question of what resets the zircon clock has always been very complicated. For a long time people have been saying if zircon is really involved in a major impact shock, its age will be reset, so you can date the impact. Aaron has been saying, ‘Yes, sometimes, but often what people see as a reset age may not really be reset.’ Zircons are the gift that keep on giving, and this will not change that, but we need to be a lot more careful in analyzing what that gift is telling us.”

    See the full article here .

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  • richardmitnick 8:26 am on October 7, 2015 Permalink | Reply
    Tags: , , , Astrobiology Magazine, Plant life   

    From astrobio.net: “Ancient alga knew how to survive on land before it left water & evolved into first plant” 

    Astrobiology Magazine

    Astrobiology Magazine

    1
    Closterium strigosum is one of the green algae the scientists analyzed. Credit: Michael Melkonian

    A team of scientists led by Dr Pierre-Marc Delaux (John Innes Centre / University of Wisconsin, Madison) has solved a long-running mystery about the first stages of plant life on earth.

    The team of scientists from the John Innes Centre, the University of Wisconsin – Madison and other international collaborators, has discovered how an ancient alga was able to inhabit land, before it went on to evolve into the world’s first plant and colonise the earth.

    Up until now it had been assumed that the alga evolved the capability to source essential nutrients for its survival after it arrived on land by forming a close association with a beneficial fungi called arbuscular mycorrhiza (AM), which still exists today and which helps plant roots obtain nutrients and water from soil in exchange for carbon.

    The previous discovery of 450 million year old fossilised spores similar to the spores of the AM fungi suggests this fungi would have been present in the environment encountered by the first land plants. Remnants of prehistoric fungi have also been found inside the cells of the oldest plant macro-fossils, reinforcing this idea.

    However, scientists were not clear how the algal ancestor of land plants could have survived long enough to mediate a quid pro quo arrangement with a fungi. This new finding points to the alga developing this crucial capability while still living in the earth’s oceans!

    Dr Delaux and colleagues analysed DNA and RNA of some of the earliest known land plants and green algae and found evidence that their shared algal ancestor living in the Earth’s waters already possessed the set of genes, or symbiotic pathways, it needed to detect and interact with the beneficial AM fungi.

    The team of scientists believes this capability was pivotal in enabling the alga to survive out of the water and to colonise the earth. By working with the fungi to find sustenance, the alga was able to buy time to adapt and evolve in a very different and seemingly infertile environment.

    Dr Delaux said: “At some point 450 million years ago, alga from the earth’s waters splashed up on to barren land. Somehow it survived and took root, a watershed moment that kick-started the evolution of life on earth. Our discovery shows for the first time that the alga already knew how to survive on land while it was still in the water. Without the development of this pre-adapted capability in alga, the earth could be a very different place today.

    “This finding has filled a gap in our collective knowledge about the origins of life on earth. None of this would have been possible without the dedication of a world-wide team of scientists including a tremendous contribution from the 1KP initiative led by Gane KS Wong .”

    Professor Jean-Michel Ané, from the University of Wisconsin said: “The surprise was finding the mechanisms in algae which allow plants to interact with symbiotic fungi. Nobody has studied beneficial associations in these algae.”

    See the full article here .

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  • richardmitnick 11:33 am on August 23, 2015 Permalink | Reply
    Tags: , , Astrobiology Magazine,   

    From astrobio.net: “As Ice Age ended, greenhouse gas rise was lead factor in melting of Earth’s glaciers” 

    Astrobiology Magazine

    Astrobiology Magazine

    Aug 23, 2015
    No Writer Credit

    1
    Improved dating methods reveal that the rise in carbon dioxide levels was the primary cause of the simultaneous melting of glaciers around the globe during the last Ice Age. The new finding has implications for rising levels of man-made greenhouse gases and retreating glaciers today. Courtesy: NSF

    A fresh look at some old rocks has solved a crucial mystery of the last Ice Age, yielding an important new finding that connects to the global retreat of glaciers caused by climate change today, according to a new study by a team of climate scientists.

    For decades, researchers examining the glacial meltdown that ended 11,000 years ago took into account a number of contributing factors, particularly regional influences such as solar radiation, ice sheets and ocean currents.

    But a reexamination of more than 1,000 previously studied glacial boulders has produced a more accurate timetable for the pre-historic meltdown and pinpoints the rise in carbon dioxide – then naturally occurring – as the primary driving factor in the simultaneous global retreat of glaciers at the close of the last Ice Age, the researchers report in the journal Nature Communications.

    “Glaciers are very sensitive to temperature. When you get the world’s glaciers retreating all at the same time, you need a broad, global reason for why the world’s thermostat is going up,” said Boston College Assistant Professor of Earth and Environmental Sciences Jeremy Shakun. “The only factor that explains glaciers melting all around the world in unison during the end of the Ice Age is the rise in greenhouse gases.”

    The researchers found that regional factors caused differences in the precise timing and pace of glacier retreat from one place to another, but carbon dioxide was the major driver of the overall global meltdown, said Shakun, a co-author of the report “Regional and global forcing of glacier retreat during the last deglaciation.”

    “This is a lot like today,” said Shakun. “In any given decade you can always find some areas where glaciers are holding steady or even advancing, but the big picture across the world and over the long run is clear – carbon dioxide is making the ice melt.”

    While 11,000 years ago may seem far too distant for a point of comparison, it was only a moment ago in geological time. The team’s findings fix even greater certainty on scientific conclusions that the dramatic increase in manmade greenhouse gases will eradicate many of the world’s glaciers by the end of this century.

    “This has relevance to today since we’ve already raised CO2 by more than it increased at the end of the Ice Age, and we’re on track to go up much higher this century — which adds credence to the view that most of the world’s glaciers will be largely gone within the next few centuries, with negative consequences such as rising sea level and depleted water resources,” said Shakun.

    The team reexamined samples taken from boulders that were left by the retreating glaciers, said Shakun, who was joined in the research by experts from Oregon State University, University of Wisconsin-Madison, Purdue University and the National Center for Atmospheric Research in Boulder, Colo.

    Each boulder has been exposed to cosmic radiation since the glaciers melted, an exposure that produces the isotope Beryllium-10 in the boulder. Measuring the levels of the isotope in boulder samples allows scientists to determine when glaciers melted and first uncovered the boulders.

    Scientists have been using this process called surface exposure dating for more than two decades to determine when glaciers retreated, Shakun said. His team examined samples collected by multiple research teams over the years and applied an improved methodology that increased the accuracy of the boulder ages.

    The team then compared their new exposure ages to the timing of the rise of carbon dioxide concentration in the atmosphere, a development recorded in air bubbles taken from ice cores. Combined with computer models, the analysis eliminated regional factors as the primary explanations for glacial melting across the globe at the end of the Ice Age. The single leading global factor that did explain the global retreat of glaciers was rising carbon dioxide levels in the air.

    “Our study really removes any doubt as to the leading cause of the decline of the glaciers by 11,000 years ago – it was the rising levels of carbon dioxide in the Earth’s atmosphere,” said Shakun.

    Carbon dioxide levels rose from approximately 180 parts per million to 280 parts per million at the end of the last Ice Age, which spanned nearly 7,000 years. Following more than a century of industrialization, carbon dioxide levels have now risen to approximately 400 parts per million.

    “This tells us we are orchestrating something akin to the end of an Ice Age, but much faster. As the amount of carbon dioxide continues to increase, glaciers around the world will retreat,” said Shakun.

    See the full article here.

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  • richardmitnick 2:08 pm on July 29, 2015 Permalink | Reply
    Tags: , , Astrobiology Magazine,   

    From astrobio.net: “‘Carbon sink’ detected underneath world’s deserts” 

    Astrobiology Magazine

    Astrobiology Magazine

    Jul 29, 2015
    No Writer Credit

    1
    Scientists followed the journey of water through the Tarim Basin from the rivers at the edge of the valley to the desert aquifers under the basin. They found that as water moved through irrigated fields, the water gathered dissolved carbon and moved it deep underground. Credit: Yan Li

    The world’s deserts may be storing some of the climate-changing carbon dioxide emitted by human activities, a new study suggests. Massive aquifers underneath deserts could hold more carbon than all the plants on land, according to the new research.

    Humans add carbon dioxide to the atmosphere through fossil fuel combustion and deforestation. About 40 percent of this carbon stays in the atmosphere and roughly 30 percent enters the ocean, according to the University Corporation for Atmospheric Research. Scientists thought the remaining carbon was taken up by plants on land, but measurements show plants don’t absorb all of the leftover carbon. Scientists have been searching for a place on land where the additional carbon is being stored—the so-called “missing carbon sink.”

    The new study suggests some of this carbon may be disappearing underneath the world’s deserts – a process exacerbated by irrigation. Scientists examining the flow of water through a Chinese desert found that carbon from the atmosphere is being absorbed by crops, released into the soil and transported underground in groundwater—a process that picked up when farming entered the region 2,000 years ago.

    Underground aquifers store the dissolved carbon deep below the desert where it can’t escape back to the atmosphere, according to the new study.

    The new study estimates that because of agriculture roughly 14 times more carbon than previously thought could be entering these underground desert aquifers every year. These underground pools that taken together cover an area the size of North America may account for at least a portion of the “missing carbon sink” for which scientists have been searching.

    “The carbon is stored in these geological structures covered by thick layers of sand, and it may never return to the atmosphere,” said Yan Li, a desert biogeochemist with the Chinese Academy of Sciences in Urumqi, Xinjiang, and lead author of the study accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union. “It is basically a one-way trip.”

    Knowing the locations of carbon sinks could improve models used to predict future climate change and enhance calculations of the Earth’s carbon budget, or the amount of fossil fuels humans can burn without causing major changes in the Earth’s temperature, according to the study’s authors.

    Although there are most likely many missing carbon sinks around the world, desert aquifers could be important ones, said Michael Allen, a soil ecologist from the Center for Conservation Biology at the University of California-Riverside who was not an author on the new study.

    If farmers and water managers understand the role heavily-irrigated inland deserts play in storing the world’s carbon, they may be able to alter how much carbon enters these underground reserves, he said.

    “This means [managers] can take practical steps that could play a role in addressing carbon budgets,” said Allen.

    2
    Researchers gathered groundwater flowing under the desert sands. The amount of carbon carried by this underground flow increased quickly when the Silk Road, which opened the region to farming, began 2,000 years ago. Credit: Yan Li

    Examining desert water

    To find out where deserts tucked away the extra carbon, Li and his colleagues analyzed water samples from the Tarim Basin, a Venezuela-sized valley in China’s Xinjiang region. Water draining from rivers in the surrounding mountains support farms that edge the desert in the center of the basin.

    The researchers measured the amount of carbon in each water sample and calculated the age of the carbon to figure out how long the water had been in the ground.

    The study shows the amount of carbon dioxide dissolved in the water doubles as it filters through irrigated fields. The scientists suggest carbon dioxide in the air is taken up by the desert crops. Some of this carbon is released into the soil through the plant’s roots. At the same time, microbes also add carbon dioxide to the soil when they break down sugars in the dirt. In a dry desert, this gas would work its way out of the soil into the air. But on arid farms, the carbon dioxide emitted by the roots and microbes is picked up by irrigation water, according to the new study.

    In these dry regions, where water is scarce, farmers over-irrigate their land to protect their crops from salts that are left behind when water used for farming evaporates. Over-irrigating washes these salts, along with carbon dioxide that is dissolved in the water, deeper into the earth, according to the new study.

    Although this process of carbon burial occurs naturally, the scientists estimate that the amount of carbon disappearing under the Tarim Desert each year is almost 12 times higher because of agriculture. They found that the amount of carbon entering the desert aquifer in the Tarim Desert jumped around the time the Silk Road, which opened the region to farming, begin to flourish.

    After the carbon-rich water flows down into the aquifer near the farms and rivers, it moves sideways toward the middle of the desert, a process that takes roughly 10,000 years.

    Any carbon dissolved in the water stays underground as it makes its way through the aquifer to the center of the desert, where it remains for thousands of years, according to the new study.

    Estimating carbon storage

    Based on the various rates that carbon entered the desert throughout history, the study’s authors estimate 20 billion metric tons (22 billion U.S. tons) of carbon is stored underneath the Tarim Basin desert, dissolved in an aquifer that contains roughly 10 times the amount of water held in the North American Great Lakes.

    The study’s authors approximate the world’s desert aquifers contain roughly 1 trillion metric tons (1 trillion U.S. tons) of carbon—about a quarter more than the amount stored in living plants on land.

    Li said more information about water movement patterns and carbon measurements from other desert basins are needed to improve the estimate of carbon stored underneath deserts around the globe.

    Allen said the new study is “an early foray” into this research area. “It is as much a call for further research as a definitive final answer,” he said.

    See the full article here.

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  • richardmitnick 9:18 am on July 23, 2015 Permalink | Reply
    Tags: astrobio, Astrobiology Magazine, ,   

    From astrobio.net: “Mini-Neptunes Might Host Life Under Right Conditions” 

    Astrobiology Magazine

    Astrobiology Magazine

    Jul 23, 2015
    Amanda Doyle

    1
    Artist’s impression of Roche lobe overflow in a planet. Credit: NASA/GSFC/Frank Reddy

    M-dwarfs, which are cooler than our sun, have habitable zones closer to the stars. As such, any habitable planets orbiting these stars would transit frequently, making the chances of discovery better.

    It sounds promising for astrobiology, yet life on a planet orbiting close to an M-drawf would face hazardous conditions. These stars are extremely active in their early years, and any nearby planet would likely get blasted with high energy radiation that would make it hard for life to take hold.

    Also, such close orbiting planets are unlikely to have water. In the proto-planetary disc that surrounds a young star, ices can only condense at a far enough distance where it is cool. This is what allows gas giants to become so massive, as they can accrete ice as well as gas and dust. With this increased core mass, they can then sweep up hydrogen and helium to create an extensive gas envelope.

    The boundary beyond which ice can form is known as the “snow line,” and planets forming in the habitable zones of some M-dwarfs are so far inside the snow line that they are devoid of water.

    2
    The dashed lines in the image show the Roche lobes of a star and a planet. As a mini-Neptune migrates inwards, the increasing effects of the star’s gravity can cause the planet’s atmosphere to extend beyond the Roche lobe. When this happens, the atmosphere is no longer gravitationally bound to the planet. Credit: Swinburne University of Technology

    But what if a gas giant migrated into the habitable zone? Astronomer Rodrigo Luger of the University of Washington, along with colleagues, have found that a certain kind of planet called a mini-Neptune with its atmosphere removed could, in fact, become a viable planet to life.

    A mini-Neptune is a gaseous planet that is up to ten times the mass of the Earth. Such a planet would be engulfed in a thick atmosphere of gas and then would need to lose its envelope before becoming a water-rich world.

    The research has been published in the journal Astrobiology.

    Losing an atmosphere

    There are two ways in which a mini-Neptune could evict its atmosphere. The first is via a process known as hydrodynamic escape. Extreme radiation from the host star in the form of x-ray and ultraviolet rays bombard the planet, causing the atmosphere to heat up. The upper atmosphere then expands, forcing the gas to accelerate to supersonic speeds. This hydrodynamic wind is fast enough for the atmosphere to escape into space.

    The second way for a mini-Neptune to shed its cloak of gas is for the atmosphere to become so extended that it is no longer gravitationally bound to the planet. The area around a star or planet where material is gravitationally bound is known as the Roche lobe. Once gas reaches the edge the of this teardrop-shaped lobe it can escape, and this is known as Roche lobe overflow. Roche lobe overflow couldn’t occur during planet formation, as it simply wouldn’t accrete the material in the first place. However, a planet migrating inwards will start to feel the effects of the star’s gravity more and more, and this can trigger the overflow.

    From mini-Neptunes to water worlds

    3
    Artist’s impression of a water world, with very few continents showing above the water. Credit: a1Star.com

    Once the initial atmosphere is gone, the solid core left behind becomes a terrestrial planet. Assuming that a secondary atmosphere could form through a process such as volcanic outgassing, this core could become habitable, earning it the name “habitable evaporated core” (HEC).

    The computer simulations run by Luger and colleagues showed that a mini-Neptune with a core mass similar to that of Earth would be the most likely candidate to become a habitable evaporated core. If the core mass was greater than twice the mass of the Earth, it could not become an evaporated core.

    Assuming that the composition of a proto-planetary disc surrounding an M-dwarf is similar to that of our Solar System, then a habitable evaporated core would likely have a lot of water since it would have formed beyond the snow line. These planets would therefore become water worlds, with little or no exposed continents.

    “While water is great for life, this could be tricky for supporting a biosphere, since high pressure ices can form at the bottom of the ocean and interrupt the carbon cycle on these planets,” explains Luger. “But we still have no idea how chemical cycling occurs on water worlds, so we can’t rule out life on these planets just yet.”

    Spot the difference

    If an Earth-mass planet is detected in the habitable zone of an M-dwarf, how will astronomers know if it is a “native” planet, which is dry and barren, or a habitable evaporated core? The key to telling them apart is in their different compositions.

    4
    A mini-Neptune compared to the size of the Earth. The core of a mini-Neptune can be similar in mass to that of the Earth. Once the hydrogen and helium envelope has been stripped, a water-rich habitable evaporated core is left behind. Credit: Geoff Marcy

    “The easiest way to (potentially) distinguish a HEC from an in-situ Earth would be density,” says Luger. “HECs will have much lower bulk densities due to their higher water fraction.”

    Measurements of the radius and mass of a planet will reveal the density, however we are still a few years away from achieving this precision. With the launch of the James Webb Space Telescope in 2018, it might be possible to detect signatures in the atmosphere of a planet which would reveal it to be an evaporated core.

    NASA Webb Telescope
    NASA/Webb

    See the full article here.

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