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  • richardmitnick 9:06 am on September 27, 2018 Permalink | Reply
    Tags: Asteroid Main Belt-between the orbits of the planets Mars and Jupiter, astrobio.net, , , , Between 33% and 35% of the asteroids in the Main Belt are members of families, BIM- Backward integration method, , Four extremely young asteroid families identified, Pericenter-the point at which an asteroid or comet comes closest to the Sun   

    From Astrobiology Magazine: “Four extremely young asteroid families identified” 

    Astrobiology Magazine

    From Astrobiology Magazine

    Sep 26, 2018

    1
    Brazilian researchers dated the families using a numerical simulation method to process current data to go back in time to the asteroid formation era (image: NASA)

    Sep 26, 2018
    1
    Brazilian researchers dated the families using a numerical simulation method to process current data to go back in time to the asteroid formation era (image: NASA)

    Four families of extremely young asteroids have been identified by researchers affiliated with São Paulo State University (UNESP) in Guaratinguetá, Brazil. An article on the discovery has been published in Monthly Notices of the Royal Astronomical Society.

    The group is led by Italian-born physicist Valerio Carruba, currently a professor in UNESP’s Mathematics Department.

    “We identified the new families by means of numerical simulation using the backward integration method (BIM), which is much more precise than other methods for dating asteroid families,” Carruba told Agência FAPESP. “But BIM only works for really young families that are less than 20 million years old. Until recently, only eight families had been studied by this method. We now know 13, almost a third of which were identified by our group.”

    The four families in question, all of which are less than 7 million years old, orbit between Mars and Jupiter as part of a grouping known as the Main Asteroid Belt.

    The key dating parameters used were the longitudes of the pericenter and ascending node. For a planet, comet or asteroid moving around the Sun in an elliptical orbit, the pericenter is the point at which it comes closest to the Sun. The ascending node is the point at which the orbit crosses from the southern side of a reference plane, typically the ecliptic plane, to the northern side.

    “When an asteroid family is formed, all the asteroids’ pericenters and ascending nodes are aligned, but as the family evolves, the alignment is lost owing to gravitational disturbances produced by planets and possibly by some massive asteroids,” Carruba explained. “Based on current data, BIM lets you go back in time using numerical simulation to reconstruct the setting in which the parameters were aligned and thereby date the asteroid family.”

    In addition to the four new families they themselves identified, the group studied 55 new families identified by other scientists. As well as dating the families, they established a diagram that, with considerable precision, distinguishes between families formed by collisional events and families formed by fission of a precursor body.

    When two asteroids collide, one or both may fragment, giving rise to a family with several objects. Fission, on the other hand, consists of the ejection of matter by a precursor body, either because it acquired very rapid rotation on its own axis and suffered a collision or because it recently expelled a secondary body that broke up.

    “One of the four families we identified was undoubtedly formed by a collisional event. Collision is very likely to have been the origin of another. The rest were identified very recently, and we need more studies to formulate a hypothesis regarding their formation,” Carruba said.

    Motion resonance

    The Main Belt is an extraordinary niche of asteroids, with more than 700 known objects. The number is rising steadily thanks to improving methods of detection, and can be estimated at roughly 1 million.

    2
    Asteroid Main Belt between Mars and Jupiter from American Museum of Natural History

    According to Carruba, the asteroids in the Main Belt are far from evenly distributed. Various different regions have formed within the belt owing to the highly complex gravitational interaction among so many bodies and, above all, to Jupiter’s powerful gravitational field.

    An important driver of this structure is a phenomenon known as “mean-motion resonance”, which occurs when two bodies orbiting a third have closely matched orbital periods related by a ratio of two small integers.

    The resonances create empty spaces in the radial distribution of the asteroids. They are called Kirkwood Gaps, in honor of US astronomer Daniel Kirkwood (1814-95), who identified and explained these asteroid-free zones in the Main Belt.

    “Between 33% and 35% of the asteroids in the Main Belt are members of families,” Carruba said. “There are over 120 recognizable families and dozens of less statistically significant groups. Large families comprise hundreds of members, whereas small families may have some ten members.”

    Estimates of the age of the asteroid families in the belt range from a few million to hundreds of millions of years. The origin of the oldest family has been dated to 4 billion years ago, so it participated in the first stage of the Solar System’s formation.

    See the full article here .


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  • richardmitnick 1:28 pm on September 12, 2018 Permalink | Reply
    Tags: astrobio.net, Astronomers witness birth of new star from stellar explosion, , , , ,   

    From Purdue University via Astrobiology Magazine: “Astronomers witness birth of new star from stellar explosion” 

    1

    Purdue University

    Astrobiology Magazine

    From Astrobiology Magazine

    Sep 12, 2018

    1
    Unlike most stellar explosions that fade away, supernova SN 2012au continues to shine today thanks to a powerful new pulsar. Credit: NASA, ESA, and J. DePasquale (STScI)

    The explosions of stars, known as supernovae, can be so bright they outshine their host galaxies. They take months or years to fade away, and sometimes, the gaseous remains of the explosion slam into hydrogen-rich gas and temporarily get bright again – but could they remain luminous without any outside interference?

    That’s what Dan Milisavljevic, an assistant professor of physics and astronomy at Purdue University, believes he saw six years after “SN 2012au” exploded.

    “We haven’t seen an explosion of this type, at such a late timescale, remain visible unless it had some kind of interaction with hydrogen gas left behind by the star prior to explosion,” he said. “But there’s no spectral spike of hydrogen in the data – something else was energizing this thing.”

    As large stars explode, their interiors collapse down to a point at which all their particles become neutrons. If the resulting neutron star has a magnetic field and rotates fast enough, it may develop into a pulsar wind nebula.

    This is most likely what happened to SN 2012au, according to findings published in The Astrophysical Journal Letters.

    “We know that supernova explosions produce these types of rapidly rotating neutron stars, but we never saw direct evidence of it at this unique time frame,” Milisavljevic said. “This a key moment when the pulsar wind nebula is bright enough to act like a lightbulb illuminating the explosion’s outer ejecta.”

    SN 2012au was already known to be extraordinary – and weird – in many ways. Although the explosion wasn’t bright enough to be termed a “superluminous” supernova, it was extremely energetic and long-lasting, and dimmed in a similarly slow light curve.

    Milisavljevic predicts that if researchers continue to monitor the sites of extremely bright supernovae, they might see similar transformations.

    “If there truly is a pulsar or magnetar wind nebula at the center of the exploded star, it could push from the inside out and even accelerate the gas,” he said. “If we return to some of these events a few years later and take careful measurements, we might observe the oxygen-rich gas racing away from the explosion even faster.”

    Superluminous supernovae are a hot topic in transient astronomy. They’re potential sources of gravitational waves and black holes, and astronomers think they might be related to other kinds of explosions, like gamma ray bursts and fast radio bursts. Researchers want to understand the fundamental physics behind them, but they’re difficult to observe because they’re relatively rare and happen so far from Earth.

    Only the next generation of telescopes, which astronomers have dubbed “Extremely Large Telescopes,” will have the ability to observe these events in such detail.

    “This is a fundamental process in the universe. We wouldn’t be here unless this was happening,” Milisavljevic said. “Many of the elements essential to life come from supernova explosions – calcium in our bones, oxygen we breathe, iron in our blood – I think it’s crucial for us, as citizens of the universe, to understand this process.”

    For Purdue University
    Kayla Zacharias,
    765-494-9318
    kzachar@purdue.edu

    Source:
    Dan Milisavljevic
    765-494-3042
    dmilisav@purdue.edu

    See the full article here .

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  • richardmitnick 1:15 pm on September 9, 2018 Permalink | Reply
    Tags: astrobio.net, , , , Clearing-orbit requirement?, , International Astronomical Union, Neptune’s gravity influences its neighboring planet Pluto, Pluto a Planet? New Research Suggests Yes, Pluto is "more dynamic and alive than Mars” Metzger says, The only planet that has more complex geology is the Earth, The reason Pluto lost its planet status is not valid according to new research from the University of Central Florida, UCF planetary scientist Philip Metzger says that the definition of a planet should be based on its intrinsic properties rather than ones that can change such as the dynamics of a planet’s orbit, What is a Planet   

    From Astrobiology Magazine: “Pluto a Planet? New Research Suggests Yes” 

    Astrobiology Magazine

    From Astrobiology Magazine

    Sep 8, 2018

    1
    Credit: NASA

    The reason Pluto lost its planet status is not valid, according to new research from the University of Central Florida.

    In 2006, the International Astronomical Union, a global group of astronomy experts, established a definition of a planet that required it to “clear” its orbit, or in other words, be the largest gravitational force in its orbit.

    Since Neptune’s gravity influences its neighboring planet Pluto, and Pluto shares its orbit with frozen gases and objects in the Kuiper belt, that meant Pluto was out of planet status.

    However, in a new study published online Wednesday in the journal Icarus, UCF planetary scientist Philip Metzger, who is with the university’s Florida Space Institute, reported that this standard for classifying planets is not supported in the research literature.

    Metzger, who is lead author on the study, reviewed scientific literature from the past 200 years and found only one publication – from 1802 – that used the clearing-orbit requirement to classify planets, and it was based on since-disproven reasoning.

    He said moons such as Saturn’s Titan and Jupiter’s Europa have been routinely called planets by planetary scientists since the time of Galileo.

    “The IAU definition would say that the fundamental object of planetary science, the planet, is supposed to be a defined on the basis of a concept that nobody uses in their research,” Metzger says. “And it would leave out the second-most complex, interesting planet in our solar system.”

    “We now have a list of well over 100 recent examples of planetary scientists using the word planet in a way that violates the IAU definition, but they are doing it because it’s functionally useful,” he says.

    “It’s a sloppy definition,” Metzger says of the IAU’s definition. “They didn’t say what they meant by clearing their orbit. If you take that literally, then there are no planets, because no planet clears its orbit.”

    The planetary scientist says that the literature review showed that the real division between planets and other celestial bodies, such as asteroids, occurred in the early 1950s when Gerard Kuiper published a paper that made the distinction based on how they were formed.

    However, even this reason is no longer considered a factor that determines if a celestial body is a planet, Metzger says.

    Study co-author Kirby Runyon, with Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, says the IAU’s definition was erroneous since the literature review showed that clearing orbit is not a standard that is used for distinguishing asteroids from planets, as the IAU claimed when crafting the 2006 definition of planets.

    “We showed that this is a false historical claim,” Runyon says. “It is therefore fallacious to apply the same reasoning to Pluto.”

    Defining “Planet”

    Metzger says that the definition of a planet should be based on its intrinsic properties, rather than ones that can change, such as the dynamics of a planet’s orbit.

    “Dynamics are not constant, they are constantly changing,” Metzger says. “So, they are not the fundamental description of a body, they are just the occupation of a body at a current era.”

    Instead, Metzger recommends classifying a planet based on if it is large enough that its gravity allows it to become spherical in shape.

    “And that’s not just an arbitrary definition,” Metzger says. “It turns out this is an important milestone in the evolution of a planetary body, because apparently when it happens, it initiates active geology in the body.”

    Pluto, for instance, has an underground ocean, a multilayer atmosphere, organic compounds, evidence of ancient lakes and multiple moons, he says.

    “It’s more dynamic and alive than Mars,” Metzger says. “The only planet that has more complex geology is the Earth.”

    See the full article here .

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  • richardmitnick 2:36 pm on August 5, 2018 Permalink | Reply
    Tags: astrobio.net, , , , , Scientists identify exoplanets where life could develop as it did on Earth,   

    From U Cambridge via Astrobiology Magazine: “Scientists identify exoplanets where life could develop as it did on Earth” 

    U Cambridge bloc

    From University of Cambridge

    Astrobiology Magazine

    From Astrobiology Magazine

    Aug 4, 2018
    1
    Artist’s concept depicting one possible appearance of the planet Kepler-452b. Credit: NASA Ames/JPL-Caltech/T. Pyle

    Scientists have identified a group of planets outside our solar system where the same chemical conditions that may have led to life on Earth exist.

    The researchers, from the University of Cambridge and the Medical Research Council Laboratory of Molecular Biology (MRC LMB), found that the chances for life to develop on the surface of a rocky planet like Earth are connected to the type and strength of light given off by its host star.

    Their study, published in the journal Science Advances, proposes that stars which give off sufficient ultraviolet (UV) light could kick-start life on their orbiting planets in the same way it likely developed on Earth, where the UV light powers a series of chemical reactions that produce the building blocks of life.

    The researchers have identified a range of planets where the UV light from their host star is sufficient to allow these chemical reactions to take place, and that lie within the habitable range where liquid water can exist on the planet’s surface.

    “This work allows us to narrow down the best places to search for life,” said Dr Paul Rimmer, a postdoctoral researcher with a joint affiliation at Cambridge’s Cavendish Laboratory and the MRC LMB, and the paper’s first author. “It brings us just a little bit closer to addressing the question of whether we are alone in the universe.”

    The new paper is the result of an ongoing collaboration between the Cavendish Laboratory and the MRC LMB, bringing together organic chemistry and exoplanet research. It builds on the work of Professor John Sutherland, a co-author on the current paper, who studies the chemical origin of life on Earth.

    In a paper published in 2015, Professor Sutherland’s group at the MRC LMB proposed that cyanide, although a deadly poison, was in fact a key ingredient in the primordial soup from which all life on Earth originated.

    In this hypothesis, carbon from meteorites that slammed into the young Earth interacted with nitrogen in the atmosphere to form hydrogen cyanide. The hydrogen cyanide rained to the surface, where it interacted with other elements in various ways, powered by the UV light from the sun. The chemicals produced from these interactions generated the building blocks of RNA, the close relative of DNA which most biologists believe was the first molecule of life to carry information.

    In the laboratory, Sutherland’s group recreated these chemical reactions under UV lamps, and generated the precursors to lipids, amino acids and nucleotides, all of which are essential components of living cells.

    “I came across these earlier experiments, and as an astronomer, my first question is always what kind of light are you using, which as chemists they hadn’t really thought about,” said Rimmer. “I started out measuring the number of photons emitted by their lamps, and then realised that comparing this light to the light of different stars was a straightforward next step.”

    The two groups performed a series of laboratory experiments to measure how quickly the building blocks of life can be formed from hydrogen cyanide and hydrogen sulphite ions in water when exposed to UV light. They then performed the same experiment in the absence of light.

    “There is chemistry that happens in the dark: it’s slower than the chemistry that happens in the light, but it’s there,” said senior author Professor Didier Queloz, also from the Cavendish Laboratory. “We wanted to see how much light it would take for the light chemistry to win out over the dark chemistry.”

    The same experiment run in the dark with the hydrogen cyanide and the hydrogen sulphite resulted in an inert compound which could not be used to form the building blocks of life, while the experiment performed under the lights did result in the necessary building blocks.

    The researchers then compared the light chemistry to the dark chemistry against the UV light of different stars. They plotted the amount of UV light available to planets in orbit around these stars to determine where the chemistry could be activated.

    They found that stars around the same temperature as our sun emitted enough light for the building blocks of life to have formed on the surfaces of their planets. Cool stars, on the other hand, do not produce enough light for these building blocks to be formed, except if they have frequent powerful solar flares to jolt the chemistry forward step by step. Planets that both receive enough light to activate the chemistry and could have liquid water on their surfaces reside in what the researchers have called the abiogenesis zone.

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    Diagram of confirmed exoplanets within the liquid water habitable zone (as well as Earth). Credit: Paul Rimmer

    Among the known exoplanets which reside in the abiogenesis zone are several planets detected by the Kepler telescope, including Kepler 452b, a planet that has been nicknamed Earth’s ‘cousin’, although it is too far away to probe with current technology. Next-generation telescopes, such as NASA’s TESS and James Webb Telescopes, will hopefully be able to identify and potentially characterise many more planets that lie within the abiogenesis zone.

    Of course, it is also possible that if there is life on other planets, that it has or will develop in a totally different way than it did on Earth.

    “I’m not sure how contingent life is, but given that we only have one example so far, it makes sense to look for places that are most like us,” said Rimmer. “There’s an important distinction between what is necessary and what is sufficient. The building blocks are necessary, but they may not be sufficient: it’s possible you could mix them for billions of years and nothing happens. But you want to at least look at the places where the necessary things exist.”

    According to recent estimates, there are as many as 700 million trillion terrestrial planets in the observable universe. “Getting some idea of what fraction have been, or might be, primed for life fascinates me,” said Sutherland. “Of course, being primed for life is not everything and we still don’t know how likely the origin of life is, even given favourable circumstances – if it’s really unlikely then we might be alone, but if not, we may have company.”

    The research was funded by the Kavli Foundation and the Simons Foundation.

    See the full article here .

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    U Cambridge Campus

    The University of Cambridge (abbreviated as Cantab in post-nominal letters) is a collegiate public research university in Cambridge, England. Founded in 1209, Cambridge is the second-oldest university in the English-speaking world and the world’s fourth-oldest surviving university. It grew out of an association of scholars who left the University of Oxford after a dispute with townsfolk. The two ancient universities share many common features and are often jointly referred to as “Oxbridge”.

    Cambridge is formed from a variety of institutions which include 31 constituent colleges and over 100 academic departments organised into six schools. The university occupies buildings throughout the town, many of which are of historical importance. The colleges are self-governing institutions founded as integral parts of the university. In the year ended 31 July 2014, the university had a total income of £1.51 billion, of which £371 million was from research grants and contracts. The central university and colleges have a combined endowment of around £4.9 billion, the largest of any university outside the United States. Cambridge is a member of many associations and forms part of the “golden triangle” of leading English universities and Cambridge University Health Partners, an academic health science centre. The university is closely linked with the development of the high-tech business cluster known as “Silicon Fen”.

     
    • stewarthoughblog 7:04 pm on August 5, 2018 Permalink | Reply

      Some very interesting science here, but very speculative to set a “abiogenesis zone” based on the paucity of habitable factors, even admitting this is the best possible at this time.

      Abiogenesis is a myth, like Darwin’s “warm little ponds,” Oparin-Haldane primordial soup, and Miller-Urey test tube goo. If there is no clue how naturalistically life developed on Earth, it is a matter of faith, not objective science, to believe it is relatively easily generated on the basis of the factors delineated here.

      Like

  • richardmitnick 12:54 pm on August 2, 2018 Permalink | Reply
    Tags: astrobio.net, , , , , , , Life on moon Titan   

    From Astrobiology Magazine via EarthSky: “Where to look for life on Titan” 

    http://www.astrobio.net/

    1

    From EarthSky

    August 2, 2018
    Paul Scott Anderson

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    Saturn’s largest moon Titan as seen by the Cassini spacecraft. This world’s liquid methane and ethane rivers, lakes and seas might support some kind of life, and scientists now think they know the best places to look. Image via NASA/JPL-Caltech.

    NASA/ESA/ASI Cassini-Huygens Spacecraft

    NASA’s Cassini spacecraft and ESA’s Huygens lander showed that Saturn’s large moon Titan mimics Earth in many ways. But Titan displays different kinds of chemistry in a far colder environment. Given the similarities, the question of life inevitably arises: could Titan support some kind of simple life? Given the differences, scientists ponder the best places to look for Titan life. In late July 2018, a new study published in the peer-reviewed journal Astrobiology and reported on in Astrobiology Magazine suggests the best places on Titan to look for evidence of life.

    Titan is a geological wonderland for planetary scientists. It has rivers, lakes and seas of actual liquid – not water, but the hydrocarbons methane and ethane – and it has mountain ranges, possible ice volcanoes (aka cryovolcanoes) and vast hydrocarbon dunes. There is also evidence for a subsurface ocean of water, similar to those believed to lie beneath the surface of Jupiter’s moon Europa and Saturn’s moon Enceladus.

    Perhaps surprisingly, the research team, led by Catherine Neish, a planetary scientist specializing in impact cratering at the University of Western Ontario, suggested that the best locations to look for life on Titan would not be the lakes or seas. Instead, the new work shows a better place to look would be within impact craters and cryovolcanoes on Titan.

    The scientists reason that these areas are where water ice in Titan’s crust could temporarily melt into a liquid. Water is still the only solvent known to be able to support life as we know it.

    2
    A large, fairly young crater on Titan, about 25 miles (40 km) in diameter. Such craters could temporarily melt frozen water in the crust, providing an environment for pre-biotic or biotic molecules to form. Image via NASA/JPL-Caltech.

    Various studies have suggested that liquid methane and ethane could support life. But Saturn’s moon Titan – some nine astronomical units farther from the sun than Earth – is very cold, with surface temperatures hovering around -300 degrees Fahrenheit (–179 degrees Celsius). Methane and ethane do remain liquid at Titan’s surface temperature, but it’s too cold there for biochemical processes, at least as far as we know (although that, too, is a matter of debate).

    Titan’s surface is also covered with tholins, which are large, complex organic molecules produced when gases are subjected to cosmic radiation. When mixed with liquid water, tholins can produce amino acids, which are, essentially, life’s building blocks. According to researcher Morgan Cable at NASA’s Jet Propulsion Laboratory in Pasadena, California:

    “When we mix tholins with liquid water, we make amino acids really fast. So any place where there is liquid water on Titan’s surface or near its surface could be generating the precursors to life – biomolecules – that would be important for life as we know it, and that’s really exciting.”

    The temperatures on Titan’s surface are too cold for liquid water, so where could it be found? The answer is Titan’s craters and cryovolcanoes. The processes involved with both of these geologic features can melt water ice into liquid, even if only temporarily.

    But that might be enough for more complex organic molecules like amino acids to form.

    3
    Sotra Facula is a possible cryovolcano on Titan, one of the few candidates known. Image via NASA/JPL–Caltech/USGS/University of Arizona.

    4
    Another view of Sotra Facula. This image was built from radar topography with infrared colors overlaid on top. Image via NASA/JPL–Caltech/USGS/University of Arizona.

    Between craters and cryovolcanoes, it would seem that craters would be the most ideal location for pre-biotic or biotic chemistry to occur. As Neish explained:

    “Craters really emerged as the clear winner for three main reasons. One, is that we’re pretty sure there are craters on Titan. Cratering is a very common geologic process and we see circular features that are almost certainly craters on the surface.’

    Neish also noted that craters would produce more liquid water melt than a cryovolcano, so any water would remain liquid for a longer period of time. She also added:

    “The last point is that impact craters should produce water that’s at a higher temperature than a cryovolcano.”

    Warmer water would allow for faster chemical reaction rates, which would help in the creation of prebiotic or even biotic molecules. The largest known craters on Titan are Sinlap (70 miles/112 kms in diameter), Selk (56 miles/90 kms) and Menrva (244 miles/392 kms). These would be the primary locations to look for biomolecules.

    David Grinspoon at the Planetary Science Institute isn’t convinced yet, however. He commented:

    “We don’t know where to search even with results like this. I wouldn’t use it to guide our next mission to Titan. It’s premature.”

    5
    Titan is well-known for its lakes and seas of liquid methane/ethane, such as Ligiea Mare, shown here. Image via NASA/JPL-Caltech/ASI/Cornell.

    So what about cryovolcanoes? They haven’t actually been confirmed yet to exist on Titan, and if they do, they are more rare than craters (even though craters are also relatively rare on Titan). The most likely feature to be a cryovolcano is a mountain with a caldera on top called Sotra Facula. Other than that, they seem to be few and far between. As Neish said:

    “Cryovolcanism is the harder thing to do and there is very little evidence of it on Titan.”

    6
    Diagram illustrating how biosignatures could also be transported from the subsurface ocean to the surface of Titan. Image via Athanasios Karagiotas/Theoni Shalamberidze.

    There is also, of course, a possible subsurface ocean of water on Titan, but, if it exists, it is deep below the moon’s surface and inaccessible to any robotic probes in the near future. For now, we can only imagine what might be in that alien abyss.

    The methane/ethane lakes and seas should still be explored too; they are the only other known bodies of liquid on the surface of another moon or planet in the solar system. Methane-based life could theoretically exist in such environments, so it would obviously be a good idea to look, at least.

    Bottom line: Titan is a world that is eerily similar to Earth in some ways, yet still uniquely alien. Whether it supports any kind of life is still a big question, but researchers now think they know the best places to search for it.

    See the full article here .


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    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

     
  • richardmitnick 10:37 am on June 8, 2018 Permalink | Reply
    Tags: , Archaean period, astrobio.net, , Did plate tectonics set the stage for life on Earth?, , Great Oxidation Event (GOE), Neoproterozoic Oxygen Event,   

    From Astrobiology Magazine: “Did plate tectonics set the stage for life on Earth?” 

    Astrobiology Magazine

    From Astrobiology Magazine

    Jun 7, 2018
    Lisa Kaspin-Powell

    The tectonic plates of the world were mapped in 1996, USGS.

    A new study suggests that rapid cooling within the Earth’s mantle through plate tectonics played a major role in the development of the first life forms, which in turn led to the oxygenation of the Earth’s atmosphere. The study was published in the March 2018 issue of Earth and Planetary Science Letters.

    Scientists at the University of Adelaide and Curtin University in Australia, and the University of California at Riverside, California, USA, gathered and analyzed data on igneous rocks from geological and geochemical data repositories in Australia, Canada, New Zealand, Sweden and the United States. They found that over the 4.5 billion years of the Earth’s development, rocks rich in phosphorus accumulated in the Earth’s crust. They then looked at the relationship of this accumulation with that of oxygen in the atmosphere.

    Phosphorus is essential for life as we know it. Phosphates, which are compounds containing phosphorus and oxygen, are part of the backbones of DNA and RNA as well as the membranes of cells, and help control cell growth and function.

    To find out how the level of phosphorus in the Earth’s crust has increased over time, the scientists studied how rock formed as the Earth’s mantle cooled. They performed modeling to find out how mantle-derived rocks changed composition as a consequence of the long-term cooling of the mantle.

    Their results suggest that during an early, hotter period in Earth’s history – the Archaean period between four and 2.5 billion years ago – there was a larger amount of molten mantle. Phosphorus would have been too dilute in these rocks. However, over time, the Earth cooled sufficiently, aided by the onset of plate tectonics, in which the colder outer crust of the planet is subducted back into the hot mantle. With this cooling, partial mantle melts became smaller.

    As Dr. Grant Cox, an earth scientist at the University of Adelaide and a co-author of the study, explains, the result is that “phosphorus will be concentrated in small percentage melts, so as the mantle cools, the amount of melt you extract is smaller but that melt will have higher concentrations of phosphorus in it.”

    1
    A cross section of the Earth, showing the exterior crust, the molten mantle beneath it and the core at the center of the planet. Image credit: NASA/JPL-Université Paris Diderot – Institut de Physique du Globe de Paris.

    Phosphorus’ role in the oxidation of Earth

    The phosphorus was concentrated and crystallized into a mineral called apatite, which became part of the igneous rocks that were created from the cooled mantle. Eventually, these rocks reached the Earth’s surface and formed a large proportion of the crust. When phosphorus minerals derived from the crust mixed with the water in lakes, rivers and oceans, apatite broke down into phosphates, which became available for development and nourishment of primitive life.

    The scientists estimated the mixing of elements from the Earth’s crust with seawater over time. They found that higher levels of bio-essential elements parallel major increases in the oxygenation of the Earth’s atmosphere: the Great Oxidation Event (GOE) 2.4 billion years ago, and the Neoproterozoic Oxygen Event, 800 million years ago, after which oxygen levels were presumed to be high enough to support multicellular life.

    Even before the GOE, from approximately 3.5 to 2.5 billion years ago, some of the earliest life forms possibly generated oxygen through photosynthesis. However, during that time, most of this oxygen reacted with iron and sulfur in igneous rocks. To understand how these reactions affected oxygen levels in the atmosphere over a period of four billion years, the scientists measured the amounts of sulfur and iron in igneous rocks, and figured out how much oxygen had reacted. They compared all of these events with changes in levels of atmospheric oxygen. The scientists found that decreases in sulfur and iron along with increases in phosphorus paralleled the Great Oxidation Event and the Neoproterozoic Oxygen Event.

    An explosion of life

    All of these events support a scenario in which the cooling of the Earth’s mantle led to the increase of phosphorus-rich rocks in the Earth’s crust. These rocks then mixed with the oceans, where phosphorus-containing minerals broke down and leached into the water. Once phosphorus levels in seawater were high enough, primitive life forms thrived and their numbers increased, so they could generate enough oxygen that most of it reached the atmosphere. Oxygen reached levels sufficient to support multicellular life.

    Dr. Peter Cawood, a geologist at Monash University inMelbourne, Australia, comments to Astrobiology Magazine that, “it’s intriguing to think that the [oxygen] on which we depend for life owes its ultimate origin to secular decreases in mantle temperature, which are thought to have decreased from some 1,550 degrees Celsius some three billion years ago to around 1,350 degrees Celsius today.”

    Could a similar scenario be playing out on a possible exo-Earth? With the Kepler discoveries of a growing number of possibly Earth-like planets, could any of these support life? Cawood suggests that the finding is potentially significant for the development of aerobic life (i.e. life that evolves in an oxygen-rich environment) on exoplanets. “This is provided that [phosphorus] within the igneous rocks on the surface of the planet is undergoing weathering to ensure its bio-availability,” says Cawood. “Significantly, the phosphorus content of igneous rocks is highest in those rocks low in silica [rocks formed by rapid cooling] and rocks of this composition dominate the crusts of Venus and Mars and likely also on exoplanets.”

    Cox concludes by saying that, “This relationship [between rising oxygen levels and mantle cooling] has implications for any terrestrial planet. All planets will cool, and those with efficient plate tectonic convection will cool more rapidly. We are left concluding that the speed of such cooling may affect the rate and pattern of biological evolution on any potentially habitable planet.”

    The research was supported by the NASA Astrobiology Institute (NAI) element of the NASA Astrobiology Program, as well as the National Science Foundation Frontiers in Earth System Dynamics Program and the Australian Research Council.

    See the full article here .


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    • stewarthoughblog 2:45 am on June 12, 2018 Permalink | Reply

      Interesting science relative to chemical and geologic observation of early Earth conditions. But, the continuous overly optimistic speculation about origin of life,OoL, in this case based on molecular formation and migration which are such a minuscule aspect of OoL origination suggests a level of desperation of naturalists to find any positive aspects of the present chaotic mess of naturalistic OoL..

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  • richardmitnick 12:38 pm on May 20, 2018 Permalink | Reply
    Tags: astrobio.net, , , ,   

    From Astrobiology Magazine: “How primordial life on Earth might have replicated itself” 

    Astrobiology Magazine

    From Astrobiology Magazine

    May 20, 2018

    1
    Liquid brine containing replicating RNA molecules is concentrated in the cracks between ice crystals, as seen with an electron microscope. Credit: Philipp Holliger, MRC LMB

    Scientists have created a new type of genetic replication system which demonstrates how the first life on Earth – in the form of RNA – could have replicated itself. The scientists from the Medical Research Council (MRC) Laboratory of Molecular Biology say the new RNA utilises a system of genetic replication unlike any known to naturally occur on Earth today.

    A popular theory for the earliest stages of life on Earth is that it was founded on strands of RNA, a chemical cousin of DNA. Like DNA, RNA strands can carry genetic information using a code of four molecular letters (bases), but RNA can be more than a simple ‘string’ of information. Some RNA strands can also fold up into three-dimensional shapes that can form enzymes, called ribozymes, and carry out chemical reactions.

    If a ribozyme could replicate folded RNA, it might be able to copy itself and support a simple living system.

    Previously, scientists had developed ribozymes that could replicate straight strands of RNA, but if the RNA was folded it blocked the ribozyme from copying it. Since ribozymes themselves are folded RNAs, their own replication is blocked.

    Now, in a paper published today in the journal eLife, the scientists have resolved this paradox by engineering the first ribozyme that is able to replicate folded RNAs, including itself.

    Normally when copying RNA, an enzyme would add single bases (C, G, A or U) one at a time, but the new ribozyme uses three bases joined together, as a ‘triplet’ (e.g. GAU). These triplet building blocks enable the ribozyme to copy folded RNA, because the triplets bind to the RNA much more strongly and cause it to unravel – so the new ribozyme can copy its own folded RNA strands.

    The scientists say that the ‘primordial soup’ could have contained a mixture of bases in many lengths – one, two, three, four or more bases joined together – but they found that using strings of bases longer than a triplet made copying the RNA less accurate.

    Dr Philipp Holliger, from the MRC Laboratory of Molecular Biology and senior author on the paper, said: “We found a solution to the RNA replication paradox by re-thinking how to approach the problem – we stopped trying to mimic existing biology and designed a completely new synthetic strategy. It is exciting that our RNA can now synthesise itself.

    “These triplets of bases seem to represent a sweet spot, where we get a nice opening up of the folded RNA structures, but accuracy is still high. Notably, although triplets are not used in present-day biology for replication, protein synthesis by the ribosome – an ancient RNA machine thought to be a relic of early RNA-based life – proceeds using a triplet code.

    “However, this is only a first step because our ribozyme still needs a lot of help from us to do replication. We provided a pure system, so the next step is to integrate this into the more complex substrate mixtures mimicking the primordial soup – this likely was a diverse chemical environment also containing a range of simple peptides and lipids that could have interacted with the RNA.”

    The experiments were conducted in ice at -7°C, because the researchers had previously discovered that freezing concentrates the RNA molecules in a liquid brine in tiny gaps between the ice crystals. This also is beneficial for the RNA enzymes, which are more stable and function better at cold temperatures.

    Dr Holliger added: “This is completely new synthetic biology and there are many aspects of the system that we have not yet explored. We hope in future, it will also have some biotechnology applications, such as adding chemical modifications at specific positions to RNA polymers to study RNA epigenetics or augment the function of RNA.”

    Dr Nathan Richardson, Head of Molecular and Cellular Medicine at the MRC, said: “This is a really exciting example of blue skies research that has revealed important insights into how the very beginnings of life may have emerged from the ‘primordial soup’ some 3.7 billion years ago. Not only is this fascinating science, but understanding the minimal requirements for RNA replication and how these systems can be manipulated could offer exciting new strategies for treating human disease.”

    See the full article here .

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  • richardmitnick 8:00 am on March 9, 2018 Permalink | Reply
    Tags: astrobio.net, , , ,   

    From astrobio.net: “Photosynthesis originated a billion years earlier than we thought, study shows” 

    Astrobiology Magazine

    Astrobiology Magazine

    Mar 7, 2018
    https://www.elsevier.com

    1
    This plate is a culture of Synechocystis sp. PCC 6803, a type of unicellular Cyanobacteria. Credit: Elsevier

    Ancient microbes may have been producing oxygen through photosynthesis a billion years earlier than we thought, which means oxygen was available for living organisms very close to the origin of life on earth. In a new article in Heliyon, a researcher from Imperial College London studied the molecular machines responsible for photosynthesis and found the process may have evolved as long as 3.6 billion years ago.

    The author of the study, Dr. Tanai Cardona, says the research can help to solve the controversy around when organisms started producing oxygen – something that was vital to the evolution of life on earth. It also suggests that the microorganisms we previously believed to be the first to produce oxygen – cyanobacteria – evolved later, and that simpler bacteria produced oxygen first.

    “My results mean that the process that sustains almost all life on earth today may have been doing so for a lot longer than we think,” said Dr. Cardona. “It may have been that the early availability of oxygen was what allowed microbes to diversify and dominate the world for billions of years. What allowed microbes to escape the cradle where life arose and conquer every corner of this world, more than 3 billion years ago.”

    Photosynthesis is the process that sustains complex life on earth – all of the oxygen on our planet comes from photosynthesis. There are two types of photosynthesis: oxygenic and anoxygenic. Oxygenic photosynthesis uses light energy to split water molecules, releasing oxygen, electrons and protons. Anoxygenic photosynthesis use compounds like hydrogen sulfide or minerals like iron or arsenic instead of water, and it does not produce oxygen.

    2
    This image is the crystal structure of Photosystem I (PDB ID: 1JB0). Credit: Elsevier

    Previously, scientists believed that anoxygenic evolved long before oxygenic photosynthesis, and that the earth’s atmosphere contained no oxygen until about 2.4 to 3 billion years ago. However, the new study suggests that the origin of oxygenic photosynthesis may have been as much as a billion years earlier, which means complex life would have been able to evolve earlier too.

    Dr. Cardona wanted to find out when oxygenic photosynthesis originated. Instead of trying to detect oxygen in ancient rocks, which is what had been done previously, he looked deep inside the molecular machines that carry out photosynthesis – these are complex enzymes called photosystems. Oxygenic and anoxygenic photosynthesis both use an enzyme called Photosystem I. The core of the enzyme looks different in the two types of photosynthesis, and by studying how long ago the genes evolved to be different, Dr. Cardona could work out when oxidative photosynthesis first occurred.

    He found that the differences in the genes may have occurred more than 3.4 billion years ago – long before oxygen was thought to have first been produced on earth. This is also long before cyanobacteria – microbes that were thought to be the first organisms to produce oxygen – existed. This means there must have been predecessors, such as early bacteria, that have since evolved to carry out anoxygenic photosynthesis instead.

    “This is the first time that anyone has tried to time the evolution of the photosystems,” said Dr. Cardona. “The result hints towards the possibility that oxygenic photosynthesis, the process that have produced all oxygen on earth, actually started at a very early stage in the evolutionary history of life – it helps solve one of the big controversies in biology today.”

    One surprising finding was that the evolution of the photosystem was not linear. Photosystems are known to evolve very slowly – they have done so since cyanobacteria appeared at least 2.4 billion years ago. But when Dr. Cardona used that slow rate of evolution to calculate the origin of photosynthesis, he came up with a date that was older than the earth itself. This means the photosystem must have evolved much faster at the beginning – something recent research suggests was due to the planet being hotter.

    “There is still a lot we don’t know about why life is the way it is and how most biological process originated,” said Dr. Cardona. “Sometimes our best educated guesses don’t even come close to representing what really happened so long ago.”

    Dr. Cardona hopes his findings may also help scientists who are looking for life on other planets answer some of their biggest questions.

    See the full article here .

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  • richardmitnick 8:50 pm on February 20, 2018 Permalink | Reply
    Tags: , astrobio.net, , PLANTS COLONIZED THE EARTH 100 MILLION YEARS EARLIER THAN PREVIOUSLY THOUGHT   

    From Astrobiology Magazine: “PLANTS COLONIZED THE EARTH 100 MILLION YEARS EARLIER THAN PREVIOUSLY THOUGHT” 

    Astrobiology Magazine

    Astrobiology Magazine

    Feb 20, 2018

    1

    For the first four billion years of Earth’s history, our planet’s continents would have been devoid of all life except microbes.

    All of this changed with the origin of land plants from their pond scum relatives, greening the continents and creating habitats that animals would later invade.

    The timing of this episode has previously relied on the oldest fossil plants which are about 420 million years old.

    New research, published in the journal Proceedings of the National Academy of Sciences USA, indicates that these events actually occurred a hundred million years earlier, changing perceptions of the evolution of the Earth’s biosphere.

    Plants are major contributors to the chemical weathering of continental rocks, a key process in the carbon cycle that regulates Earth’s atmosphere and climate over millions of years.

    The team used ‘molecular clock’ methodology, which combined evidence on the genetic differences between living species and fossil constraints on the age of their shared ancestors, to establish an evolutionary timescale that sees through the gaps in the fossil record.

    Dr Jennifer Morris, from the University of Bristol’s School of Earth Sciences and co-lead author on the study, explained: “The global spread of plants and their adaptations to life on land, led to an increase in continental weathering rates that ultimately resulted in a dramatic decrease the levels of the ‘greenhouse gas’ carbon dioxide in the atmosphere and global cooling.

    “Previous attempts to model these changes in the atmosphere have accepted the plant fossil record at face value – our research shows that these fossil ages underestimate the origins of land plants, and so these models need to be revised.”

    Co-lead author Mark Puttick described the team’s approach to produce the timescale. He said: “The fossil record is too sparse and incomplete to be a reliable guide to date the origin of land plants. Instead of relying on the fossil record alone, we used a ‘molecular clock’ approach to compare differences in the make-up of genes of living species – these relative genetic differences were then converted into ages by using the fossil ages as a loose framework.

    “Our results show the ancestor of land plants was alive in the middle Cambrian Period, which was similar to the age for the first known terrestrial animals.”

    One difficulty in the study is that the relationships between the earliest land plants are not known. Therefore the team, which also includes members from Cardiff University and the Natural History Museum, London, explored if different relationships changed the estimated origin time for land plants.

    Leaders of the overall study, Professor Philip Donoghue and Harald Schneider added: “We used different assumptions on the relationships between land plants and found this did not impact the age of the earliest land plants.

    “Any future attempts to model atmospheric changes in deep-time must incorporate the full range of uncertainties we have used here.”

    See the full article here .

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  • richardmitnick 2:19 pm on January 8, 2017 Permalink | Reply
    Tags: astrobio.net, Scientists Offer Sharper Insight into Pluto’s Bladed Terrain   

    From astrobio.net: “Scientists Offer Sharper Insight into Pluto’s Bladed Terrain” 

    Astrobiology Magazine

    Astrobiology Magazine

    Jan 6, 2017
    No writer credit

    1
    The bladed terrain of Pluto’s informally named Tartarus Dorsa region, imaged by NASA’s New Horizons spacecraft in July 2015. Credits: NASA/JHUAPL/SwRI

    NASA/New Horizons spacecraft
    NASA/New Horizons spacecraft

    Using a model similar to what meteorologists use to forecast weather and a computer simulation of the physics of evaporating ices, scientists have found evidence of snow and ice features on Pluto that, until now, had only been seen on Earth.

    Formed by erosion, the features, known as “penitentes,” are bowl-shaped depressions with blade-like spires around the edge that rise several hundreds of feet.

    The research, led by John Moores of York University, Toronto, and done in collaboration with scientists at the Johns Hopkins University Applied Physics Laboratory and NASA Goddard Space Flight Center, indicates that these icy features may also exist on other planets where environmental conditions are similar.

    The identification of these ridges in Pluto’s informally named Tartarus Dorsa area suggests that the presence of an atmosphere is necessary for the formation of penitentes – which Moores says would explain why they have not previously been seen on other airless icy satellites or dwarf planets. “But exotic differences in the environment give rise to features with very different scales,” he adds. “This test of our terrestrial models for penitentes suggests that we may find these features elsewhere in the solar system, and in other solar systems, where the conditions are right.”

    The research team, which also includes York’s Christina Smith, Anthony Toigo of APL and Scott Guzewich of Goddard Space Flight Center, compared its model to ridges on Pluto imaged by NASA’s New Horizons spacecraft in 2015. Pluto’s ridges are much larger – more than 1,600 feet (about 500 meters) tall and separated by two to three miles (about three to five kilometers) – than their Earthly counterparts.

    “This gargantuan size is predicted by the same theory that explains the formation of these features on Earth,” says Moores. “In fact, we were able to match the size and separation, the direction of the ridges, as well as their age: three pieces of evidence that support our identification of these ridges as penitentes.”

    Moores says though Pluto’s environment is very different from Earth’s — it is much colder, the air much thinner, the sun much dimmer and the snow and ice on the surface are made from methane and nitrogen instead of water — the same laws of nature apply. He adds that both NASA and APL were instrumental in the collaboration that led to this new finding; both provided background information on Pluto’s atmosphere using a model similar to what meteorologists use to forecast weather on Earth. This was one of the key ingredients in Moores’ own models of the penitentes, without which this discovery would not have been made.

    The findings appear this week in the journal Nature.

    See the full article here .

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