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  • richardmitnick 2:20 pm on October 19, 2014 Permalink | Reply
    Tags: , , , , , , Venus   

    From astrobio.net: “Rediscovering Venus to Find Faraway Earths “ 

    Astrobiology Magazine

    Astrobiology Magazine

    Oct 19, 2014
    fa
    Contact:
    Lyndsay Meyer
    The Optical Society
    +1.202.416.1435
    lmeyer@osa.org

    New optical device designed to measure gravitational pull of a planet should speed the search for Earth-like exoplanets.

    Astronomers Chih-Hao Li and David Phillips of the Harvard-Smithsonian Center for Astrophysics want to rediscover Venus—that familiar, nearby planet stargazers can see with the naked eye much of the year.

    Granted, humans first discovered Venus in ancient times. But Li and Phillips have something distinctly modern in mind. They plan to find the second planet again using a powerful new optical device installed on the Italian National Telescope that will measure Venus’ precise gravitational pull on the sun. If they succeed, their first-of-its-kind demonstration of this new technology will be used for finding Earth-like exoplanets orbiting distant stars.

    Italian National Telescope Galileo
    Italian National Telescope Galileo Internal
    Galileo Italian National Telescope

    “We are building a telescope that will let us see the sun the way we would see other stars,” said Phillips, who is a staff scientist at the Harvard-Smithsonian Center for Astrophysics. He and Li, a research associate at the Center for Astrophysics, will describe the device in a paper to be presented at The Optical Society’s (OSA) 98th Annual Meeting, Frontiers in Optics, being held Oct. 19-23 in Tucson, Arizona, USA. Li is the lead author of the paper, which has 12 collaborators.

    Astronomers have identified more than 1,700 exoplanets, some as far as hundreds of light years away. Most were discovered by the traditional transit method, which measures the decrease in brightness when a planet orbiting a distant star transits that luminous body, moving directly between the Earth and the star. This provides information about the planet’s size, but not its mass.

    Li and Phillips are developing a new laser-based technology known as the green astro-comb for use with the “radial velocity method,” which offers complementary information about the mass of the distant planet.

    From this information, astronomers will be able to determine whether distant exoplanets they discover are rocky worlds like Earth or less dense gas giants like Jupiter. The method is precise enough to help astronomers identify Earth-like planets in the “habitable zone,” the orbital distance “sweet-spot” where water exists as a liquid.

    Better Precision with a Laser

    The radial velocity method works by measuring how exoplanet gravity changes the light emitted from its star. As exoplanets circle a star, their gravitation tugs at the star changing the speed with which it moves toward or away from Earth by a small amount. The star speeds up slightly as it approaches Earth, with each light wave taking a fraction of a second less time to arrive than the wave before it.

    To an observer on Earth, the crests of these waves look closer together than they should, so they appear to have a higher frequency and look bluer. As the star recedes, the crests move further apart and the frequencies seem lower and redder.

    astro
    The astro-comb calibrates the Italian National Telescope’s HARPS-Nspectrograph using an observation of the asteroid Vesta. The top figure is a colorizedversion of the raw HARPS-N spectrum, showing the astro-comb calibration dottedlines and the sun’s spectrum reflected off Vesta as mostly solid vertical lines.The middle figure shows the raw data converted to a very precise standard one-dimensionalplot of spectral intensity vs. wavelength. The very regular astro-comb calibrationspectrum is below below. Credit: David Phillips

    This motion-based frequency change is known as the Doppler shift. Astronomers measure it by capturing the spectrum of a star on the pixels of a digital camera and watching how it changes over time.

    Today’s best spectrographs are only capable of measuring Doppler shifts caused by velocity changes of 1 meter per second or more. Only large gas giants or “super-earths” close to their host stars have enough gravity to cause those changes.

    The new astro-comb Li, Phillips and their colleagues are developing, however, will be able to detect Doppler shifts as small as 10 centimeters per second—small enough to find habitable zone Earth-like planets, even from hundreds of light years away.

    “The astro-comb works by injecting 8,000 lines of laser light into the spectrograph. They hit the same pixels as starlight of the same wavelength. This creates a comb-like set of lines that lets us map the spectrograph down to 1/10,000 of a pixel. So if I have light on this section of the pixel, I can tell you the precise wavelength,” Phillips explained.

    “By calibrating the spectrograph this way, we can take into account very small changes in temperature or humidity that affect the performance of the spectrograph. This way, we can compare data we take tonight with data from the same star five years from now and find those very small Doppler shifts,” he said.

    Seeing Green

    Li and his co-researchers pioneered the astro-comb several years ago, but it only worked with infrared and blue light. Their new version of the astro-comb lets astronomers measure green light—which is better for finding exoplanets.

    “The stars we look at are brightest in the green visible range, and this is the range spectrographs are built to handle,” Phillips said.

    Building the green astro-comb was a challenge, since the researchers needed to convert red laser light to green frequencies. They did it by making small fibers that convert one color of light to another.

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    A slowly rotating planet is not guaranteed to be habitable, as is evident when looking at the inhospitable Venus. Credit: NASA/JPL/Caltech

    “Red light goes in and green light comes out,” Phillips said. “Even though I see it every day and understand the physics, it looks like magic.”

    The researchers plan to test the green astro-comb by pointing it at our sun, analyzing its spectrum to see if they can find Venus and rediscover its characteristic period of revolution, its size, its mass and its composition.

    “We know a lot about Venus, and we can compare our answers to what we already know, so we are more confident about our answers when we point our spectrographs at distant stars,” Li said.

    The Harvard-Smithsonian team is installing this device on the High-Accuracy Radial Velocity Planet Searcher-North (HARPS-N), a new spectrograph designed to search for exoplanets using the Italian National Telescope.

    “We will look at the thousands of potential exoplanets identified by the Kepler satellite telescope by the transit method. Together, our two methods can tell us a lot about those worlds,” Li said.

    And, because he will have already discovered Venus, he will be more certain of the answers.

    See the full article here.

    NASA

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  • richardmitnick 9:43 am on September 16, 2014 Permalink | Reply
    Tags: , , , , , , Venus   

    From astrobio.net: “NASA Research Helps Unravel Mysteries Of The Venusian Atmosphere” 

    Astrobiology Magazine

    Astrobiology Magazine

    NASA Research Helps Unravel Mysteries Of The Venusian Atmosphere
    Sep 15, 2014
    Source: NASA
    Karen C. Fox NASA’s Goddard Space Flight Center, Greenbelt, Md.

    two
    Earth and Venus – worlds apart. Credits: Earth: NASA; Venus: Magellan Project/NASA/JPL

    Underscoring the vast differences between Earth and its neighbor Venus, new research shows a glimpse of giant holes in the electrically charged layer of the Venusian atmosphere, called the ionosphere. The observations point to a more complicated magnetic environment than previously thought – which in turn helps us better understand this neighboring, rocky planet.

    Planet Venus, with its thick atmosphere made of carbon dioxide, its parched surface, and pressures so high that landers are crushed within a few hours, offers scientists a chance to study a planet very foreign to our own. These mysterious holes provide additional clues to understanding Venus’s atmosphere, how the planet interacts with the constant onslaught of solar wind from the sun, and perhaps even what’s lurking deep in its core.

    “This work all started with a mystery from 1978,” said Glyn Collinson, a space scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who is first author of a paper on this work in the Journal of Geophysical Research. “When Pioneer Venus Orbiter moved into orbit around Venus, it noticed something very, very weird – a hole in the planet’s ionosphere. It was a region where the density just dropped out, and no one has seen another one of these things for 30 years.”

    NASA Pioneer Venus Orbiter
    NASA/Pioneer Venus Orbiter

    Until now.


    New research shows giant holes in Venus’ atmosphere – which serve as extra clues for understanding this planet so different from our own. Image Credit: NASA’s Goddard Space Flight Center/G. Duberstein

    Collinson set out to search for signatures of these holes in data from the European Space Agency’s Venus Express. Venus Express, launched in 2006, is currently in a 24-hour orbit around the poles of Venus. This orbit places it in much higher altitudes than that of the Pioneer Venus Orbiter, so Collinson wasn’t sure whether he’d spot any markers of these mysterious holes. But even at those heights the same holes were spotted, thus showing that the holes extended much further into the atmosphere than had been previously known.

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    ESA/Venus Express

    The observations also suggested the holes are more common than realized. Pioneer Venus Orbiter only saw the holes at a time of great solar activity, known as solar maximum. The Venus Express data, however, shows the holes can form during solar minimum as well.

    Interpreting what is happening in Venus’s ionosphere requires understanding how Venus interacts with its environment in space. This environment is dominated by a stream of electrons and protons – a charged, heated gas called plasma — which zoom out from the sun. As this solar wind travels it carries along embedded magnetic fields, which can affect charged particles and other magnetic fields they encounter along the way. Earth is largely protected from this radiation by its own strong magnetic field, but Venus has no such protection.

    What Venus does have, however, is an ionosphere, a layer of the atmosphere filled with charged particles. The Venusian ionosphere is bombarded on the sun-side of the planet by the solar wind. Consequently, the ionosphere, like air flowing past a golf ball in flight, is shaped to be a thin boundary in front of the planet and to extend into a long comet-like tail behind. As the solar wind plows into the ionosphere, it piles up like a big plasma traffic jam, creating a thin magnetosphere around Venus – a much smaller magnetic environment than the one around Earth.

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    Venus Express aerobraking. Credit: ESA

    Venus Express is equipped to measure this slight magnetic field. As it flew through the ionospheric holes it recorded a jump in the field strength, while also spotting very cold particles flowing in and out of the holes, though at a much lower density than generally seen in the ionosphere.

    The Venus Express observations suggest that instead of two holes behind Venus, there are in fact two long, fat cylinders of lower density material stretching from the planet’s surface to way out in space. Collinson said that some magnetic structure probably causes the charged particles to be squeezed out of these areas, like toothpaste squeezed out of a tube.

    The next question is what magnetic structure can create this effect? Imagine Venus standing in the middle of the constant solar wind like a lighthouse erected in the water just off shore. Magnetic field lines from the sun move toward Venus like waves of water approaching the lighthouse. The far sides of these lines then wrap around the planet leading to two long straight magnetic field lines trailing out directly behind Venus. These lines could create the magnetic forces to squeeze the plasma out of the holes.

    But such a scenario would place the bottom of these tubes on the sides of the planet, not as if they were coming straight up out of the surface. What could cause magnetic fields to go directly in and out of the planet? Without additional data, it’s hard to know for sure, but Collinson’s team devised two possible models that can match these observations.

    In one scenario, the magnetic fields do not stop at the edge of the ionosphere to wrap around the outside of the planet, but instead continue further.

    “We think some of these field lines can sink right through the ionosphere, cutting through it like cheese wire,” said Collinson. “The ionosphere can conduct electricity, which makes it basically transparent to the field lines. The lines go right through down to the planet’s surface and some ways into the planet.”

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    Venus cloud tops. Credit: ESA/MPS/DLR/IDA

    In this scenario, the magnetic field travels unhindered directly into the upper layers of Venus. Eventually, the magnetic field hits Venus’ rocky mantle – assuming, of course, that the inside of Venus is like the inside of Earth. A reasonable assumption given that the two planets are the same mass, size and density, but by no means a proven fact.

    A similar phenomenon does happen on the moon, said Collinson. The moon is mostly made up of mantle and has little to no atmosphere. The magnetic field lines from the sun go through the moon’s mantle and then hit what is thought to be an iron core.

    In the second scenario, the magnetic fields from the solar system do drape themselves around the ionosphere, but they collide with a pile up of plasma already at the back of the planet. As the two sets of charged material jostle for place, it causes the required magnetic squeeze in the perfect spot.

    Either way, areas of increased magnetism would stream out on either side of the tail, pointing directly in and out of the sides of the planet. Those areas of increased magnetic force could be what squeezes out the plasma and creates these long ionospheric holes.

    Scientists will continue to explore just what causes these holes. Confirming one theory or the other will, in turn, help us understand this planet, so similar and yet so different from our own.

    See the full article here.

    NASA

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  • richardmitnick 8:49 am on July 15, 2014 Permalink | Reply
    Tags: , , , , , , Venus   

    From Forbes: “New Venus NASA Missions Could Lift Planet’s Hellish Veil” 

    forbes

    7/15/2014
    Bruce Dorminey

    If Mars is mysterious, Venus is truly scary. Long called Earth’s twin, it’s only four months away via unmanned probe and lies more than 70 percent of Earth’s distance from the Sun.

    But with surface pressures and temperatures high enough to melt lead and crush steel, why is Venus so hauntingly different from Earth? And when did it go bad?

    “Venus and Earth are virtually identical twins; they’re almost the same size,” said Robert Herrick, a planetary geophysicist at the University of Alaska in Fairbanks. “But Venus is completely uninhabitable; we really don’t understand how that dichotomy came about.”

    The European Space Agency’s (ESA) Venus Express orbiter has spent the last eight years trying to dissect its hellish atmosphere and surface. But now with dwindling fuel, by year’s end the spacecraft is expected to make its final plunge into Venus’ toxic atmosphere.
    Scale representations of Venus and the Earth s…

    ESA Venus Express
    ESA/Venus Express

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    Scale representations of Venus and the Earth shown next to each other. Venus is only slightly smaller. (Photo credit: Wikipedia)

    While Venus Express has made scientific progress, planetary scientists say, a few major puzzles have yet to be solved.

    Larry Esposito, a planetary scientist at the University of Colorado at Boulder, says the most puzzling things are: How did Venus go bad? How did the high-wind dynamics of the atmosphere arise on Venus? What is its surface made of? And does Venus still have volcanic activity?

    Venus Express took infrared images of the planet’s surface and found that its biggest volcanoes do indeed indicate lava flow there within the last 250,000 years.

    “Venus Express also detected a sudden increase in sulfur dioxide; the same thing that comes out of unscrubbed coal-powered plants on earth,” said Esposito. “But on Venus Express, it was interpreted as a possible real-time volcanic eruption.”

    One explanation is that Venus undergoes giant volcanic eruptions every few decades. But how do these putative eruptions contribute to Venus’ ongoing dense, noxious atmosphere?

    Calculations of surface-atmosphere interactions indicate that the planet’s atmospheric sulfur should be “sopped up” by the surface in a few tens of millions of years, says Kevin Baines, a planetary scientist at NASA JPL and the University of Wisconsin at Madison. Baines says this means if the present cloudy atmosphere is typical and ongoing, then there must be active volcanism to resupply the atmosphere with sulfur. He notes that “a hot atmosphere” may “soften” the surface, allowing increased sulfur emission.

    One of a handful of potential Venus mission proposals — each vying for a slot in NASA’s Discovery-class mission program — could help clear up Venus’ remaining mysteries.

    A proposed VASE (Venus Atmosphere and Surface Explorer) mission might skim the clouds and on a final landing even get data from the surface, says Mark Bullock, a planetary scientist at the Southwest Research Institute in Boulder, and a VASE definition team member.

    But Bullock says “if you really want to understand this you have to put lots of balloons in the atmosphere to understand how the surface and the atmosphere interact.”

    As for why Venus ultimately became so inhospitable?

    The short answer is that as the Sun increases in luminosity, the inner edge of our solar system’s habitable zone also continually moves outward; thus, long ago, Venus simply became too hot to hold onto its liquid water.

    This loss, says Baines, was likely caused by the “ravaging solar wind” and the effects of ultraviolet photons “ripping water molecules into hydrogen and oxygen,” which in turn led to the escape of Venus’ hydrogen into space.

    “To me, the main puzzle is when did Venus lose its oceans,” said Bullock. “The paradigm is that Venus lost its oceans up to 600 million years after its formation. But there is absolutely no data which contradicts the possibility that Venus was actually Earth-like for billions of years.”

    Could Earth suffer a similar fate?

    “Earth is definitely on a path to a Venus-like condition and anthropogenic carbon emissions are the beginning of it,” said Bullock. “That’s dramatic, but there’s no question that Earth will go in that direction.”

    As for finding proof of Venus’ ancient lakes or seas, Baines says a surface lander that sampled rocks and found water-bearing materials or materials that could only be formed in standing water would clinch that.

    However, Bullock says there are also people who think it may not ever have had an ocean and its water was always steam.

    In terms of our geological understanding of Venus, Herrick says we’re where we were with Mars three decades ago. NASA’s 1990s Magellan mission to Venus was only able to see things several football fields across and larger. But he says a newer generation of Synthetic Aperture Radars (SAR)s is capable of giving researchers much better images.

    For a planet with a dense atmosphere, like Venus, Herrick says synthetic aperture radar would image the surface and researchers would interpret the black and white image results very much like images from planets with more transparent atmospheres.

    A proposed RAVEN (Radar at Venus) mission would compare a new radar-imaging orbiter focused on understanding Venus’ geology as well as identifying future potential landing sites. One of its goals would be to definitively determine whether Venus has continents and whether such putative continents are composed of granitic rock, as here on Earth.

    “We don’t know that the high-lying regions on Venus are actually like Earth’s continents,” said Esposito. “We haven’t identified granite yet on Venus and don’t know its major surface rock types.”

    Venus doesn’t have Earth-styled plate tectonics, says Herrick, but he says we don’t have enough high-resolution topography information to understand how Venus is releasing its heat.

    NASA will put out a Discovery mission Announcement of Opportunity this September. By year’s end, the agency is expected to then pick three to five proposals for further study. Conceivably, one or more of a handful of competing Venus mission proposals may ultimately chosen and see launch as early as 2020.

    As for longer range Venus missions?

    “New missions that orbit the planet for decades,” said Baines, “may allow us to complete the picture of what happened to Venus to convert it from a verdant oasis to a (non)living hell.”

     
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