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  • richardmitnick 1:00 pm on September 17, 2019 Permalink | Reply
    Tags: , , , , Extremophiles, Homestake Mining Company, James Whitlock and Carson Sharp, , , Ray Davis and the Solar Neutrino Experiment, RBCs-Rotating Biological Contactors, , Terry Mudder, The bacterium "pseudomonas paucimobilis mudlock", WWTP- $10 million Wastewater Treatment Plant   

    From Sanford Underground Research Facility: “The extremophiles that saved the waterways” 

    SURF logo
    Sanford Underground levels

    From Sanford Underground Research Facility


    Homestake Mining Company

    September 16, 2019
    Erin Broberg

    1
    James Whitlock, chemist for Homestake Mining Company in the 1970s and 80s, at his home in Spearfish, SD in 2019. Photo by Erin Broberg

    In the 1970s, while Ray Davis was underground taking data with the Solar Neutrino Experiment, another chemist was at work on the surface of Homestake Mining Company (Homestake).

    2
    The idea of housing physics research at Sanford Lab came long before its official conversion to a research facility. The first physics experiment came to Homestake Mine in the mid-1960s when Dr. Ray Davis, a chemist from Brookhaven National Lab, began building his solar neutrino experiment on the 4850 Level. Despite nearly three decades of counting neutrinos, Davis consistently found only one-third of the number predicted. This became known as the solar neutrino problem. Eventually the problem was solved through new understandings in neutrino physics. By the time Ray Davis received the Nobel Prize in Physics in 2002, the deep caverns of the mine were coveted for continued particle physics research.

    While Davis puzzled over the solar neutrino problem, chemist James Whitlock was working to clean up the waterways of the Black Hills. Although the transition of the facility to a full-fledged science laboratory was decades away, both researchers were forerunners in the fields of physics and biology, respectively, that would be studied there.

    An industrial waste crisis

    The Black Hills today are traced by clear-flowing creeks, dotted with lakes and awash with aquatic life. Just 50 years ago, however, the view from banks in the Black Hills was quite different.

    Then, America was facing an industrial waste crisis. Industries, including mining, manufacturing and even agriculture, were leaking waste into waterways, contaminating the nation’s underground water sources.

    In response, the Environmental Protection Agency was created in 1970, followed by the Clean Water Act in 1972, which introduced regulations that stymied the discharge of pollutants into the nation’s surface waters, including lakes, rivers, streams, wetlands and coastal areas. Industries were facing new regulations and desperately searching for ways to clean their waste and remain in operation.

    Many areas in Black Hills bore the mark of this environmental crisis. “I remember Whitewood Creek growing up, but I would’ve never called it a creek then,” said Whitlock, who grew up just 20 miles away in Spearfish.

    That’s because, for most of the 20th century, Whitewood Creek flowed through the South Dakota towns of Lead and Deadwood, clogged with tailings and laced with toxic chemicals. The creek was grey, thick as sludge and known locally as “Cyanide Creek.”

    Mining companies had long used cyanide to extract gold ore from crushed rock, releasing the tailings and chemicals into waterways. Whitewood Creek had become more than a local eyesore; full of pollutants, its path wound from the Northern Hills, pouring into the Cheyenne River, then the Missouri River and eventually the Mississippi River.

    By the time Whitlock began working as a biochemist at Homestake, the mine was searching for a way to reverse industrial impacts to the area. In 1977, Homestake completed a tailings dam in Grizzly Gulch where heavy tailings could settle out of the water instead of clogging the creek. This, however, was mostly a superficial solution.

    “The problem was, all of the cyanide and toxic metals were still flowing down the stream,” said Whitlock. “It looked cleaner, but from a toxicity standpoint, it wasn’t. There wasn’t any life.”

    Homestake turned to its team of chemists, which included Whitlock; Carson Sharp, chief chemist; and Terry Mudder, environmental engineer.

    “We tried chemical processes first,” said Whitlock. “But even if we were able to get rid of the cyanide with chemicals, the process itself created a leftover chemical soup that nothing could live in.”

    A living, breathing solution

    After a bleak meeting between Homestake officials and EPA lawyers, Whitlock sighed and turned to the EPA representative who sat next to him. “It’s too bad we never had time to try a biological option,” he said. The representative paused, yet said nothing. When the meeting reconvened, it was announced that Homestake had six months to find a biological option that would allow Homestake to continue operating.

    “I honestly don’t think anyone thought a biological solution would work,” said Whitlock. “I think both sides were buying time. It was a bit of a fluke, really.”

    Still, the team went to work, determined to use the allotted time to explore biological solutions.

    “When I was in graduate school, we didn’t have amino acid and DNA analyzers. One of the tests for identifying bacteria was that certain types could tolerate cyanide and some couldn’t,” said Whitlock. “I thought, well, if they can tolerate it, they have to have a mechanism that allows that.”

    The group discovered Whitewood Creek wasn’t completely lifeless. Certain extreme lifeforms were not only surviving in spite of the cyanide-laden water but had adapted to survive because of it. These extremophiles were using cyanide as an energy source.

    By slowly introducing these bacteria to higher concentrations of cyanide, the team developed a strain that could breakdown Homestake’s cyanide waste. The bacterium was dubbed “pseudomonas paucimobilis mudlock,” taking its last name from the scientists who developed it, Mudder and Whitlock.

    Although multiple tests proved that the cyanide was removed, the next challenge was convincing others that the novel process of using living organisms to treat a poisonous chemical problem was legitimate—and worth the construction of a multimillion-dollar wastewater treatment plant.

    Biological treatment was a novel idea at the time, especially to those outside the scientific community. Many officials within the EPA, and Homestake itself, were skeptical of this untried process. The team built a bioassay tank and filled it with biologically treated wastewater, then stocked it with trout, giving the skeptics visible proof of the microscopic change.

    “We showed that not only did the trout survive, but actually, with the warm water, their growth rate was a lot faster and they were actually healthier,” said Whitlock.

    Whitlock helped design the $10 million Wastewater Treatment Plant (WWTP) and the patented technology that would set nationwide trends, making Homestake an industry leader in wastewater treatment processes.

    3
    Present-day Waste Water Treatment Plant at Sanford Underground Research Facility. Photo by Matthew Kapust

    “In 1983, we got it in full-scale operation,” said Whitlock. “Within half a year, we did bioassessments on the stream—we started seeing organisms, fish coming upstream, and, within the first year or two, they caught a state record trout.”

    In 1985, the same Time Magazine article that decried the water crisis in America, ended with a segment entitled “Turning to New Technologies” that showcased Homestake’s patented design for wastewater treatment.

    How it works

    The defining feature of the WWTP were dozens of Rotating Biological Contactors, or RBCs, that housed millions of thriving bacteria.

    4
    Present-day Waste Water Treatment Plant at Sanford Underground Research Facility. Photo by Matthew Kapust

    Once it was pumped from the underground or received from the cyanide breakdown process, the water flowed through the slowly rotating RBCs. The slow rotation of the cylinders allowed the bacteria to alternate between contact with the water below and much-needed oxygen above.

    The first set of RBCs housed bacteria that broke down cyanide. “Cyanide is carbon and nitrogen, with a little triple bond between them. The bacteria didn’t actually eat the carbon or nitrogen. Instead, they are cutting that bond; that’s where they get their energy,” explained Whitlock.

    When the bond broke, carbon became CO2 and the nitrogen became ammonia, a toxic byproduct. The second set of RBCs housed bacteria that broke ammonia into nitrates, then further into nitrites, that could be discharged safely into the creek. The bacteria also absorbed suspended metals, including iron, silver, copper, lead and mercury.

    “The beautiful thing about using bacteria,” Whitlock noted, “is that you don’t have to pay them. They do the work for food, and the food is the waste you’re trying to get rid of anyway.”

    Over time, the bacteria even adapted to fluctuations in the wastewater, something that a chemical plant would be unable to cope with.

    “There were a thousand different types of bacteria in there, everything that comes out of the mine or the tailings impoundment,” said Whitlock. “If you only had a single chemical to break down cyanide, you’d be dead in the water from a single spill. But living organisms can adapt. We got so we hardly ever saw an upset.”

    Impacting future operations

    The WWTP continued to operate until 2002, when the declining cost of gold forced Homestake to close. Whitlock worked with Homestake for 13 years before leaving to become a consultant for similar industries trying to reduce waste. He married Carson Sharp in 1986. They traveled to Russia, Africa, Canada, Mexico and South America as waste treatment consultants before eventually returning to Spearfish.

    5
    The effluent of Sanford Underground Research Facility’s Waste Water Treatment Plant, originally designed by Homestake Mining Company, meets Gold Run Creek, which flows into Whitewood Creek. Photo by Matthew Kapust.

    When the facility reopened in 2007 and began to transition into a science facility, Whitlock worked for Sanford Underground Research Facility (Sanford Lab) for seven years to help rehabilitate the WWTP. Because no gold is being processed, the treatment plant uses fewer RBCs, treating only suspended metals and trace amounts of ammonia in water pumped from the underground workings. Using the technologies perfected by Homestake, the plant is still a leader in environmental responsibility, continuing to monitor the health of nearby creeks, counting fish and macro invertebrate populations.

    Epilogue

    Today, the field that was marked by skepticism is now a leader in industry. Biologists from around the world still come to the facility to study fascinating organisms, however, they focus on those that thrive underground. They gather samples from a number of levels and areas with different temperatures, chemical properties and geologic mineralogies.

    In Sanford Lab’s unique ecosystems, researchers have discovered extremophiles that have evolved to survive by consuming methane. Other microbes generate their own electricity with bioelectrochemical systems. Still others are being studied to understand how life could survive on other planets with similar stressors, like extreme heat, temperature, pressure, radiation and lack of sunlight.

    Researchers hope that these life forms, like the bacteria discovered in the 1970s, will lead to industry and medical advances, as well as environmental restoration.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    About us.
    The Sanford Underground Research Facility in Lead, South Dakota, advances our understanding of the universe by providing laboratory space deep underground, where sensitive physics experiments can be shielded from cosmic radiation. Researchers at the Sanford Lab explore some of the most challenging questions facing 21st century physics, such as the origin of matter, the nature of dark matter and the properties of neutrinos. The facility also hosts experiments in other disciplines—including geology, biology and engineering.

    The Sanford Lab is located at the former Homestake gold mine, which was a physics landmark long before being converted into a dedicated science facility. Nuclear chemist Ray Davis earned a share of the Nobel Prize for Physics in 2002 for a solar neutrino experiment he installed 4,850 feet underground in the mine.

    Homestake closed in 2003, but the company donated the property to South Dakota in 2006 for use as an underground laboratory. That same year, philanthropist T. Denny Sanford donated $70 million to the project. The South Dakota Legislature also created the South Dakota Science and Technology Authority to operate the lab. The state Legislature has committed more than $40 million in state funds to the project, and South Dakota also obtained a $10 million Community Development Block Grant to help rehabilitate the facility.

    In 2007, after the National Science Foundation named Homestake as the preferred site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL), the South Dakota Science and Technology Authority (SDSTA) began reopening the former gold mine.

    In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through the Lawrence Berkeley National Laboratory, agreed to support ongoing science operations at Sanford Lab, while investigating how to use the underground research facility for other longer-term experiments. The SDSTA, which owns Sanford Lab, continues to operate the facility under that agreement with Berkeley Lab.

    The first two major physics experiments at the Sanford Lab are 4,850 feet underground in an area called the Davis Campus, named for the late Ray Davis. The Large Underground Xenon (LUX) experiment is housed in the same cavern excavated for Ray Davis’s experiment in the 1960s.

    LBNL LZ project at SURF, Lead, SD, USA, will replace LUX at SURF

    In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive detector yet to search for dark matter—a mysterious, yet-to-be-detected substance thought to be the most prevalent matter in the universe. The Majorana Demonstrator experiment, also on the 4850 Level, is searching for a rare phenomenon called “neutrinoless double-beta decay” that could reveal whether subatomic particles called neutrinos can be their own antiparticle. Detection of neutrinoless double-beta decay could help determine why matter prevailed over antimatter. The Majorana Demonstrator experiment is adjacent to the original Davis cavern.

    LUX’s mission was to scour the universe for WIMPs, vetoing all other signatures. It would continue to do just that for another three years before it was decommissioned in 2016.

    In the midst of the excitement over first results, the LUX collaboration was already casting its gaze forward. Planning for a next-generation dark matter experiment at Sanford Lab was already under way. Named LUX-ZEPLIN (LZ), the next-generation experiment would increase the sensitivity of LUX 100 times.

    SLAC physicist Tom Shutt, a previous co-spokesperson for LUX, said one goal of the experiment was to figure out how to build an even larger detector.
    “LZ will be a thousand times more sensitive than the LUX detector,” Shutt said. “It will just begin to see an irreducible background of neutrinos that may ultimately set the limit to our ability to measure dark matter.”
    We celebrate five years of LUX, and look into the steps being taken toward the much larger and far more sensitive experiment.

    The recently assembled LUX-ZEPLIN xenon detector in the Surface Assembly Lab cleanroom at SURF

    Another major experiment, the Long Baseline Neutrino Experiment (LBNE)—a collaboration with Fermi National Accelerator Laboratory (Fermilab) and Sanford Lab, is in the preliminary design stages. The project got a major boost last year when Congress approved and the president signed an Omnibus Appropriations bill that will fund LBNE operations through FY 2014. Called the “next frontier of particle physics,” LBNE will follow neutrinos as they travel 800 miles through the earth, from FermiLab in Batavia, Ill., to Sanford Lab.

    FNAL LBNE/DUNE from FNAL to SURF, Lead, South Dakota, USA


    LBNE

    U Washington Majorana Demonstrator Experiment at SURF

    The MAJORANA DEMONSTRATOR will contain 40 kg of germanium; up to 30 kg will be enriched to 86% in 76Ge. The DEMONSTRATOR will be deployed deep underground in an ultra-low-background shielded environment in the Sanford Underground Research Facility (SURF) in Lead, SD. The goal of the DEMONSTRATOR is to determine whether a future 1-tonne experiment can achieve a background goal of one count per tonne-year in a 4-keV region of interest around the 76Ge 0νββ Q-value at 2039 keV. MAJORANA plans to collaborate with GERDA for a future tonne-scale 76Ge 0νββ search.

    CASPAR at SURF


    CASPAR is a low-energy particle accelerator that allows researchers to study processes that take place inside collapsing stars.

    The scientists are using space in the Sanford Underground Research Facility (SURF) in Lead, South Dakota, to work on a project called the Compact Accelerator System for Performing Astrophysical Research (CASPAR). CASPAR uses a low-energy particle accelerator that will allow researchers to mimic nuclear fusion reactions in stars. If successful, their findings could help complete our picture of how the elements in our universe are built. “Nuclear astrophysics is about what goes on inside the star, not outside of it,” said Dan Robertson, a Notre Dame assistant research professor of astrophysics working on CASPAR. “It is not observational, but experimental. The idea is to reproduce the stellar environment, to reproduce the reactions within a star.”

     
  • richardmitnick 9:00 am on June 18, 2019 Permalink | Reply
    Tags: DeMMO The Deep Mine Microbial Observatory, Extremophiles, NASA Astrobiology's Exobiology program,   

    From Sanford Underground Research Facility: “NASA Exobiology studies extremophiles at Sanford Lab” 

    SURF logo
    Sanford Underground levels

    From Sanford Underground Research Facility

    June 17, 2019
    Erin Broberg

    Researchers with NASA’s Exobiology Program are in search of extremophiles deep below the earth’s surface.

    1
    Brittany Kruger and Lily Momper, researchers with NASA’s Exobiology Program, collect samples on the 2000 Level of Sanford Lab. Matthew Kapust

    It’s not all cleanrooms and Tyvek suits at Sanford Underground Research Facility (Sanford Lab). Sometimes, it’s muck boots and headlamps. Last week, visiting biologists stepped off the cage onto the 1700 Level of Sanford Lab. From there, the team motored via trolley through the drift, took ATVs down a ramp and walked a mile through shin-deep water by the light of their headlamps to reach a collection site on the 2000 Level.

    Researchers were in search of inhabitants that live deep below the earth’s surface.

    The project is part of NASA Astrobiology’s Exobiology program, which aims to understand the origin, evolution, distribution and future of life in the Universe. In an earlier phase of the project, Kruger’s team collected samples from other extreme environments, including wells near Death Valley, naturally-occurring springs in Northern California and deep ocean environments.

    “We are studying subsurface samples to learn how microbes are metabolizing and surviving in those locations to help us understand how life might be functioning on other planets that experience the same or similar stressors, like extreme heat, temperature, pressure, radiation and lack of sunlight,” said Brittany Kruger, field work coordinator and assistant research scientist with the DRI.

    Sanford Lab, with over 370 miles of shafts, drifts and ramps, serves the project as DeMMO, or the Deep Mine Microbial Observatory. The observatory is a network of boreholes that intersect fluid-filled fractures on the 800, 2000, 3950 and 4850 levels. Kruger’s team visits two to three times a year to collect samples from the various boreholes.

    “Each borehole we visit is very different in terms of microbiology,” said Kruger. “The differences are not only dependent upon depth, but also on the chemistry of the water that flows through the site.”

    Once Kruger and her team collect the samples, they spend hours processing them.

    “At each DeMMO borehole, we do a suite of both biological and chemical analyses sample collecting,” said Kruger. Some chemical analyses are completed in situ, while other samples are collected in bottles with preservative to be analyzed in a lab. The chemical analysis helps researchers understand the specific environment in which the microbes are living.

    “In terms of microbiology, we take a two-part approach,” Kruger explained. “We take raw water back to the lab to try to grow microbes from that water sample. We also filter the water to collect and concentrate cells.” By concentrating the cells, researchers can do a roll call via DNA analysis to understand which species are present and how the community is functioning.

    “With each sample, we are finding thousands of species. The vast majority overlap with samples we or others have collected elsewhere. That being said, every time we take a sample, we find many organisms that are completely undescribed in the science community and are only known by their DNA sequences. We don’t yet know what they do, how they eat or how they live.”

    By studying these organisms, researchers hope to better understand how these microbes live in such extreme environments.

    “There are components of each of the sites that can relate to environments in space,” explained Kruger. “For example, if we are able to sample the water coming out of the holes anaerobically, without letting oxygen influence them, then that’s much more representative of something you might find on Europa (a moon of Jupiter) or an icy world where there is plenty of water, but no oxygen.”

    With the initial phase of determining whether the underground environments are stable—both microbially and chemically—the team is diving into more technically driven scientific questions, with implications for life on earth, as well as potential life in space.

    “This research informs big-picture questions,” said Kruger. “As a whole, we are gaining a better understanding of subsurface microbiology.”

    Learn more about DeMMO at Sanford Lab.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    About us.
    The Sanford Underground Research Facility in Lead, South Dakota, advances our understanding of the universe by providing laboratory space deep underground, where sensitive physics experiments can be shielded from cosmic radiation. Researchers at the Sanford Lab explore some of the most challenging questions facing 21st century physics, such as the origin of matter, the nature of dark matter and the properties of neutrinos. The facility also hosts experiments in other disciplines—including geology, biology and engineering.

    The Sanford Lab is located at the former Homestake gold mine, which was a physics landmark long before being converted into a dedicated science facility. Nuclear chemist Ray Davis earned a share of the Nobel Prize for Physics in 2002 for a solar neutrino experiment he installed 4,850 feet underground in the mine.

    Homestake closed in 2003, but the company donated the property to South Dakota in 2006 for use as an underground laboratory. That same year, philanthropist T. Denny Sanford donated $70 million to the project. The South Dakota Legislature also created the South Dakota Science and Technology Authority to operate the lab. The state Legislature has committed more than $40 million in state funds to the project, and South Dakota also obtained a $10 million Community Development Block Grant to help rehabilitate the facility.

    In 2007, after the National Science Foundation named Homestake as the preferred site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL), the South Dakota Science and Technology Authority (SDSTA) began reopening the former gold mine.

    In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through the Lawrence Berkeley National Laboratory, agreed to support ongoing science operations at Sanford Lab, while investigating how to use the underground research facility for other longer-term experiments. The SDSTA, which owns Sanford Lab, continues to operate the facility under that agreement with Berkeley Lab.

    The first two major physics experiments at the Sanford Lab are 4,850 feet underground in an area called the Davis Campus, named for the late Ray Davis. The Large Underground Xenon (LUX) experiment is housed in the same cavern excavated for Ray Davis’s experiment in the 1960s.

    LBNL LZ project at SURF, Lead, SD, USA, will replace LUX at SURF

    In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive detector yet to search for dark matter—a mysterious, yet-to-be-detected substance thought to be the most prevalent matter in the universe. The Majorana Demonstrator experiment, also on the 4850 Level, is searching for a rare phenomenon called “neutrinoless double-beta decay” that could reveal whether subatomic particles called neutrinos can be their own antiparticle. Detection of neutrinoless double-beta decay could help determine why matter prevailed over antimatter. The Majorana Demonstrator experiment is adjacent to the original Davis cavern.

    LUX’s mission was to scour the universe for WIMPs, vetoing all other signatures. It would continue to do just that for another three years before it was decommissioned in 2016.

    In the midst of the excitement over first results, the LUX collaboration was already casting its gaze forward. Planning for a next-generation dark matter experiment at Sanford Lab was already under way. Named LUX-ZEPLIN (LZ), the next-generation experiment would increase the sensitivity of LUX 100 times.

    SLAC physicist Tom Shutt, a previous co-spokesperson for LUX, said one goal of the experiment was to figure out how to build an even larger detector.
    “LZ will be a thousand times more sensitive than the LUX detector,” Shutt said. “It will just begin to see an irreducible background of neutrinos that may ultimately set the limit to our ability to measure dark matter.”
    We celebrate five years of LUX, and look into the steps being taken toward the much larger and far more sensitive experiment.

    Another major experiment, the Long Baseline Neutrino Experiment (LBNE)—a collaboration with Fermi National Accelerator Laboratory (Fermilab) and Sanford Lab, is in the preliminary design stages. The project got a major boost last year when Congress approved and the president signed an Omnibus Appropriations bill that will fund LBNE operations through FY 2014. Called the “next frontier of particle physics,” LBNE will follow neutrinos as they travel 800 miles through the earth, from FermiLab in Batavia, Ill., to Sanford Lab.

    FNAL LBNE/DUNE from FNAL to SURF, Lead, South Dakota, USA


    LBNE

    U Washington Majorana Demonstrator Experiment at SURF

    The MAJORANA DEMONSTRATOR will contain 40 kg of germanium; up to 30 kg will be enriched to 86% in 76Ge. The DEMONSTRATOR will be deployed deep underground in an ultra-low-background shielded environment in the Sanford Underground Research Facility (SURF) in Lead, SD. The goal of the DEMONSTRATOR is to determine whether a future 1-tonne experiment can achieve a background goal of one count per tonne-year in a 4-keV region of interest around the 76Ge 0νββ Q-value at 2039 keV. MAJORANA plans to collaborate with GERDA for a future tonne-scale 76Ge 0νββ search.

    LBNL LZ project at SURF, Lead, SD, USA

    CASPAR at SURF


    CASPAR is a low-energy particle accelerator that allows researchers to study processes that take place inside collapsing stars.

    The scientists are using space in the Sanford Underground Research Facility (SURF) in Lead, South Dakota, to work on a project called the Compact Accelerator System for Performing Astrophysical Research (CASPAR). CASPAR uses a low-energy particle accelerator that will allow researchers to mimic nuclear fusion reactions in stars. If successful, their findings could help complete our picture of how the elements in our universe are built. “Nuclear astrophysics is about what goes on inside the star, not outside of it,” said Dan Robertson, a Notre Dame assistant research professor of astrophysics working on CASPAR. “It is not observational, but experimental. The idea is to reproduce the stellar environment, to reproduce the reactions within a star.”

     
  • richardmitnick 12:50 pm on May 28, 2019 Permalink | Reply
    Tags: "The Message of Really, “Kimberley” formation of Gale Crater on Mars taken by NASA’s Curiosity rover, Ethiopia’s Danakil Depression, Extremophiles, , Really Extreme Life"   

    From Many Worlds: “The Message of Really, Really Extreme Life” 

    NASA NExSS bloc

    NASA NExSS

    Many Words icon

    From Many Worlds

    May 28, 2019
    Marc Kaufman

    1
    Hydrothermal system at Ethiopia’s Danakil Depression, where uniquely extreme life has been found in salt chimneys and surrounding water. The yellow deposits are a variety of sulphates and the red areas are deposits of iron oxides. Copper salts color the water green. (Felipe Gomez/Europlanet 2020 RI)

    Ethiopia’s Dallol volcano and hot springs have created an environment about as hostile to life as can be imagined.

    Temperatures in the supersaturated water reach more than 200 degrees F (94 C) and are reported to approach pure acidity, with an extraordinarily low pH of 0.25. The environment is also highly salty, with salt chimneys common.

    Yet researchers have just reported finding ultra-small bacteria living in one of the acidic, super-hot salt chimneys. The bacteria are tiny — up to 20 times smaller than the average bacteria — but they are alive and in their own way thriving.

    In the world of extremophiles, these nanohaloarchaeles order bacteria are certainly on the very edge of comprehension. But much the same can be said of organisms that can withstand massive doses of radiation, that survive deep below the Earth’s surface with no hint of life support from the sun and its creations, that keep alive deep in glacier ice and even floating high in the atmosphere. And as we know, spacecraft have to be well sterilized because bacteria (in hibernation) aboard can survive the trip to the moon or Mars.

    Not life it is generally understood. But the myriad extremophiles found around the globe in recent decades have brought home the reality that we really don’t know where and how life can survive; indeed, these extremophiles often need their conditions to be super-severe to succeed.

    And that’s what makes them so important for the search for life beyond Earth. They are proof of concept that some life may well need planetary and atmospheric conditions that would have been considered utterly uninhabitable not long ago.

    2
    Montage from the Dallol site: (A) the sampling site, (B) the small chimneys (temperature of water 90 ºC. (C) D9 sample from a small chimney in (A). (D-L) Scanning Electron Microscope and (M-O) Scanning Transmission Electron Microscope images of sample D9 showing the morphologies of ultra-small microorganisms entombed in the mineral layers. (Gomez et al/Europlanet 2020 Research Infrastructure)

    The unusual and extreme life and geochemistry of Dallol has been studied by a team led by Felipe Gómez from Astrobiology Center in Spain.

    The samples were collected during a field trip to the Dallol volcano and the Danakil Depression in northern Ethiopia in January 2017, which was funded by the Europlanet 2020 Research Infrastructure (RI). The results were published this week in the journal, Scientific Reports.

    The area is consistently one of the hottest in the world, both because of its near-equatorial location, the Dallol volcano and hot springs, and that much of it is below sea level.

    Its psychedelic appearance comes from the condensation of superheated water saturated with various salts, including silver chloride, zinc iron sulphide, manganese dioxide and normal rock-salt.

    The team collected samples of the thin layers of salt deposits from the wall of a yellow chimney stack and a bluish pool of water surrounding the outcrop (above.)

    The samples were brought in sterile, sealed vials to state-of-the-art facilities in Spain, where they were analyzed using a range of techniques, including electron microscopy, chemical analysis and DNA sequencing.

    The team identified tiny, spherical structures within the salt samples that had a high carbon content, demonstrating an unambiguously biological origin.

    “This is an exotic, multi-extreme environment, with organisms that need to love high temperature, high salt content and very low pH in order to survive,” Gómez said. And love it they do, raising the most interesting question of whether they adapted to the conditions or emerged from them.

    Just last month, the same international team published a review in the journal Astrobiology describing the close parallels between the Dallol area and the hydrothermal environments found on Mars — including the Gusev Crater, where NASA’s Spirit Mars Exploration Rover landed in .

    As is the norm in the effort to understand life in extreme conditions and astrobiology generally, they focused on the geology and geochemistry of the site that gave rise to the extreme life.

    “The physical and compositional features of the Dallol deposits, their mineralogies, sedimentary and alteration features, and their location in a region of basaltic volcanism of planetary-scale importance, are testament to the novelty of this extreme environment and its ability to host life-forms and to preserve biosignatures,” they wrote.

    “It is therefore also a reliable analog to ancient martian environments and habitats. Deep investigation of the characteristics of this unique geological site will improve our understanding of the limits of life on Earth and inform the search for life on Mars.”

    3
    A view from the “Kimberley” formation of Gale Crater on Mars taken by NASA’s Curiosity rover. The mission has confirmed the long-ago presence of large amounts of water on the planet, as well as organic compounds needed for life. Curiosity was not equipped to be a life detection mission, but the follow-up Mars 2020 rover mission will be. The colors are adjusted so that rocks look approximately as they would if they were on Earth, to help geologists interpret the rocks. day, or sol, of the mission. (NASA/JPL-Caltech/MSSS)

    While this summation is surely accurate, it is also true that findings like these tell a larger story that goes well beyond Mars. Because the discovery of such a vast number and variety of extremophiles on Earth is one of the key factors that has led many space scientists and astrobiologists to conclude that life beyond Earth is likely.

    If life can survive such unusual and extreme conditions on Earth, logic says that this flexibility would no doubt be present on other potentially habitable planets and moons.

    Other major factors pointing to the plausibility of life beyond Earth are now broadly accepted:

    We now know there are billions upon billions of stars in our own Milky Way galaxy, and that most of them have planets orbiting them. The Kepler Space Telescope was crucial to reaching that consensus through its survey of one small bit of the distant sky.
    The most common planets are small and rocky ones, and some of them are within the habitable zones of their host star. This means the planet can at least sometimes support liquid water; in other words that it is neither too hot (close to its star) or too cold (far from its star.) Liquid water is considered to be essential to assemble and support life.
    The physics and chemistry of the cosmos appear to be consistent with what exists on Earth.

    None of this means any particular planet will support life since there are many other factors at play, such as how circular or elliptical the planet’s orbit might be, as well as the presence and composition of an atmosphere and a protective magnetic field. But our increasingly better understanding of exoplanets, solar systems and extreme life has brought legions of scientists into that hunt for extraterrestrial life — and they have found many ways to move forward as well as to avoid errors.

    3
    An overview of the past, present, and future of research on remotely detectable biosignatures from an Astrobiology journal paper by NASA NExSS participants. Research historically has focused on cataloguing lists of substances or physical features that yield spectral signatures as indicators of potential life on exoplanets. Recent progress has led to an understanding of how environmental context is critical to interpret signatures of nonliving planets that may mimic some effects of biota. Exoplanet observing telescopes in the near future hold promise to provide direct spectral imaging that can chemically characterize rocky planets in the habitable zone of their parent star. Anticipating these capabilities, the field should seek to develop frameworks to utilize widespread but sparse data to deliver quantitative assessments of whether or not a given planet has life. (Aaron Gronstal)

    While the Dallol discoveries (and others like them) are encouraging, they are sobering as well. Finding these creatures here on Earth has been very difficult, so imagine how challenging it will be to detect the presence of comparable microbial life on now desiccated Mars or a distant planet.

    Indeed, it would be impossible because their small numbers and limited metabolism don’t provide enough of a chemical biosignature to be detected even by telescopes and spectrographs a million times more powerful than what we have now. In terms of exoplanets, what is needed is a planet where plentiful life is providing a strong global biosignature of some kind.

    That ups the ante quite a bit in the search for life beyond Earth. But there are a vast multitude of planets out there, and a logic to the possibility that some have enough life on them for us to some day detect it.

    See the full article here .


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    About Many Worlds
    There are many worlds out there waiting to fire your imagination.

    Marc Kaufman is an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer, and is the author of two books on searching for life and planetary habitability. While the “Many Worlds” column is supported by the Lunar Planetary Institute/USRA and informed by NASA’s NExSS initiative, any opinions expressed are the author’s alone.

    This site is for everyone interested in the burgeoning field of exoplanet detection and research, from the general public to scientists in the field. It will present columns, news stories and in-depth features, as well as the work of guest writers.

    About NExSS

    The Nexus for Exoplanet System Science (NExSS) is a NASA research coordination network dedicated to the study of planetary habitability. The goals of NExSS are to investigate the diversity of exoplanets and to learn how their history, geology, and climate interact to create the conditions for life. NExSS investigators also strive to put planets into an architectural context — as solar systems built over the eons through dynamical processes and sculpted by stars. Based on our understanding of our own solar system and habitable planet Earth, researchers in the network aim to identify where habitable niches are most likely to occur, which planets are most likely to be habitable. Leveraging current NASA investments in research and missions, NExSS will accelerate the discovery and characterization of other potentially life-bearing worlds in the galaxy, using a systems science approach.
    The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

    President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

    Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

    NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

     
  • richardmitnick 10:42 am on November 13, 2017 Permalink | Reply
    Tags: A Johns Hopkins biologist has deputized an army of "citizen scientists" to collect samples out in the field, , Extremophiles, , The cosmos is too vast and too crowded with the hundreds of billions or perhaps trillions of galaxies filled with stars and planets for there not to be life out there somewhere, We found some colonization and are working now to upload it all to the Rockiology website   

    From Hopkins: “Johns Hopkins researcher enlists citizen scientists to track down rocks harboring earthly ‘extraterrestrials'” 

    Johns Hopkins
    Johns Hopkins University

    Nov 9, 2017
    Arthur Hirsch

    1
    To collect and examine rocks that could house microbes, a Johns Hopkins biologist has deputized an army of “citizen scientists” to collect samples out in the field. Image credit: Darci J. Harland

    In a small New Mexico town called Truth or Consequences, a pair of homeschooled brothers are on the hunt for extraterrestrials.

    With their mom and a small group of other families, Caleb, 10, and Corban, 6, scour the scrubby desert ground at the base of nearby Turtle Back Mountain, searching for certain kinds of rocks that could be home to microorganisms so resilient and so tough that they might be able to survive outside their rock hosts and live on other planets or moons.

    2
    Corban Harland, 6, inspects a rock, looking for the telltale green haze that indicates the presence of microbes called extremophiles.
    Image credit: Darci J. Harland

    These citizen scientists were deputized by Johns Hopkins biologist Jocelyne DiRuggiero—who specializes in astrobiology, or the study of the origins, evolution, and distribution of life in the universe—through her crowdsourcing research project, Rockiology. DiRuggiero believes that rocks in deserts and other extreme locations around the world could be home to single-cell microbes that may shed light on whether life could exist outside of our planet.

    After all, suggests DiRuggiero, the cosmos is too vast and too crowded with the hundreds of billions or perhaps trillions of galaxies filled with stars and planets for there not to be life out there somewhere.

    But the hunt begins at home.

    To learn more about these microbes, named extremophiles for the extreme conditions in which they live, DiRuggiero needs to collect samples. To gather those samples, she needs help reaching the most dry, barren places on Earth: deserts, dry valleys in Antarctica, places that resemble other planets.

    “We can go to some places and collect rocks, but we can’t go everywhere,” said DiRuggiero, an associate research professor in the Department of Biology in the Krieger School of Arts and Sciences. “We try to be creative and conserve resources.”

    That’s where sleuths like Caleb, Corban, and their mom, Darci J. Harland, come in. While scouting for home-school projects, Harland came across the Rockiology website, which features instructions on what sort of rocks the researchers are seeking, what characteristics to look for, and how to send in photos of the rocks—and perhaps eventually the rocks themselves—along with information on where they were found.


    Video: David Schmelick and Deirdre Hammer

    “I’ve always enjoyed getting kids out into the field to collect data, not just talking about it,” said Harland, who is a former public school science and English teacher and university professor of education. “And what better way to do that than to collect data for an actual scientist who needs your help?”

    Locations that are potentially rich with extremophile-housing rocks are very dry, very salty, or both. The Atacama desert in Chile, for instance, with its expanses of desolate, reddish terrain—cracked in some spots, littered with stones in others, and broken with jagged cliffs and rock formations—could easily pass for Mars.

    DiRuggiero has conducted several rock-collecting expeditions there, discovering a number of Atacama sodium chloride rocks that have been “colonized,” as she likes to put it, by microbes. In the exposed innards of a cracked rock, the colonies give away their position in a faint green haze on the white surface. There the creatures find refuge from the more dry, sunny, and windy conditions in the desert.

    So far Harland, her sons, and other homeschool families have taken basic lessons in rocks, extremophiles, and DiRuggiero’s work, and they have embarked on sample-gathering expeditions to Turtle Back Mountain.

    “We found some colonization and are working now to upload it all to the Rockiology website,” Harland said in an email. “Being able to communicate with the scientist on this project has been very rewarding both for me and for the students. They were careful in their data collection, knowing it was ‘for real.'”

    Microbes that can live in a salt rock might help a scientist learn something about creatures living in, say, briny water. That could be significant for astrobiologists wondering about the prospect of liquid water on Mars, which could be a sign that the place could support life. If water exists there as a liquid it is likely to be very salty, perhaps toxic.

    The hunt goes on for more information about extremophiles, the search party now expanded to include anyone who signs on for citizen Rockiology.

    See the full article here .

    Please help promote STEM in your local schools.
    STEM Icon

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    Johns Hopkins Campus

    The Johns Hopkins University opened in 1876, with the inauguration of its first president, Daniel Coit Gilman. “What are we aiming at?” Gilman asked in his installation address. “The encouragement of research … and the advancement of individual scholars, who by their excellence will advance the sciences they pursue, and the society where they dwell.”

    The mission laid out by Gilman remains the university’s mission today, summed up in a simple but powerful restatement of Gilman’s own words: “Knowledge for the world.”

    What Gilman created was a research university, dedicated to advancing both students’ knowledge and the state of human knowledge through research and scholarship. Gilman believed that teaching and research are interdependent, that success in one depends on success in the other. A modern university, he believed, must do both well. The realization of Gilman’s philosophy at Johns Hopkins, and at other institutions that later attracted Johns Hopkins-trained scholars, revolutionized higher education in America, leading to the research university system as it exists today.

     
  • richardmitnick 6:27 am on November 2, 2017 Permalink | Reply
    Tags: , , , , , , Earth-sized alien worlds are out there. Now astronomers are figuring out how to detect life on them, Exobiology, Extremophiles, , NASA Deep Space Climate Observatory, NASA HabEx, , , ,   

    From Science: “Earth-sized alien worlds are out there. Now, astronomers are figuring out how to detect life on them” 

    ScienceMag
    Science Magazine

    Nov. 1, 2017
    Daniel Clery

    Stephen Kane spends a lot of time staring at bad pictures of a planet. The images are just a few pixels across and nearly featureless. Yet Kane, an astronomer at the University of California, Riverside, has tracked subtle changes in the pixels over time. They are enough for him and his colleagues to conclude that the planet has oceans, continents, and clouds. That it has seasons. And that it rotates once every 24 hours.

    He knows his findings are correct because the planet in question is Earth.

    1
    An image from the Deep Space Climate Observatory satellite (left), degraded to a handful of pixels (right), is a stand-in for how an Earth-like planet around another star might look through a future space telescope.
    (LEFT TO RIGHT) NASA EPIC TEAM; STEPHEN KANE

    Kane took images from the Deep Space Climate Observatory satellite, which has a camera pointing constantly at Earth from a vantage partway to the sun, and intentionally degraded them from 4 million pixels to just a handful.

    2
    NASA Deep Space Climate Observatory

    The images are a glimpse into a future when telescopes will be able to just make out rocky, Earth-sized planets around other stars. Kane says he and his colleagues are trying to figure out “what we can expect to see when we can finally directly image an exoplanet.” Their exercise shows that even a precious few pixels can help scientists make the ultimate diagnosis: Does a planet harbor life?

    Finding conclusive evidence of life, or biosignatures, on a planet light-years away might seem impossible, given that space agencies have spent billions of dollars sending robot probes to much closer bodies that might be habitable, such as Mars and the moons of Saturn, without detecting even a whiff of life. But astronomers hope that a true Earth twin, bursting with flora and fauna, would reveal its secrets to even a distant observer.

    Detecting them won’t be easy, considering the meager harvest of photons astronomers are likely to get from such a tiny, distant world, its signal almost swamped by its much brighter nearby star. The new generation of space telescopes heading toward the launch pad, including NASA’s mammoth James Webb Space Telescope (JWST), have only an outside chance of probing an Earth twin in sufficient detail.

    NASA/ESA/CSA Webb Telescope annotated

    But they will be able to sample light from a range of other planets, and astronomers are already dreaming of a space telescope that might produce an image of an Earth-like planet as good as Kane’s pixelated views of Earth. To prepare for the coming flood of exoplanet data, and help telescope designers know what to look for, researchers are now compiling lists of possible biosignatures, from spectral hints of gases that might emanate from living things to pigments that could reside in alien plants or microbes.

    There is unlikely to be a single smoking gun. Instead, context and multiple lines of evidence will be key to a detection of alien life. Finding a specific gas—oxygen, say—in an alien atmosphere isn’t enough without figuring out how the gas could have gotten there. Knowing that the planet’s average temperature supports liquid water is a start, but the length of the planet’s day and seasons and its temperature extremes count, too. Even an understanding of the planet’s star is imperative, to know whether it provides steady, nourishing light or unpredictable blasts of harmful radiation.

    “Each [observation] will provide crucial evidence to piece together to say if there is life,” says Mary Voytek, head of NASA’s astrobiology program in Washington, D.C.

    In the heady early days following the discovery of the first exoplanet around a normal star in 1995, space agencies drew up plans for extremely ambitious—and expensive—missions to study Earth twins that could harbor life. Some concepts for NASA’s Terrestrial Planet Finder and the European Space Agency’s Darwin mission envisaged multiple giant telescopes flying in precise formation and combining their light to increase resolution. But neither mission got off the drawing board. “It was too soon,” Voytek says. “We didn’t have the data to plan it or build it.”

    Instead, efforts focused on exploring the diversity of exoplanets, using both ground-based telescopes and missions such as NASA’s Kepler spacecraft.

    NASA/Kepler Telescope

    Altogether they have identified more than 3500 confirmed exoplanets, including about 30 roughly Earth-sized worlds capable of retaining liquid water. But such surveys give researchers only the most basic physical information about the planets: their orbits, size, and mass. In order to find out what the planets are like, researchers need spectra: light that has passed through the planet’s atmosphere or been reflected from its surface, broken into its component wavelengths.

    Most telescopes don’t have the resolution to separate a tiny, dim planet from its star, which is at least a billion times brighter. But even if astronomers can’t see a planet directly, they can still get a spectrum if the planet transits, or passes in front of the star, in the course of its orbit. As the planet transits, starlight shines through its atmosphere; gases there absorb particular wavelengths and leave characteristic dips in the star’s spectrum.

    Astronomers can also study a transiting planet by observing the star’s light as the planet’s orbit carries it behind the star.

    Planet transit. NASA/Ames

    Before the planet is eclipsed, the spectrum will include both starlight and light reflected from the planet; afterward, the planet’s contribution will disappear. Subtracting the two spectra should reveal traces of the planet.

    Teasing a recognizable signal from the data is far from easy. Because only a tiny fraction of the star’s light probes the atmosphere, the spectral signal is minuscule, and hard to distinguish from irregularities in the starlight itself and from absorption by Earth’s own atmosphere. Most scientists would be “surprised at how horrible the data is,” says exoplanet researcher Sara Seager of the Massachusetts Institute of Technology in Cambridge.

    In spite of those hurdles, the Hubble and Spitzer space telescopes, plus a few others, have used these methods to detect atmospheric gases, including sodium, water, carbon monoxide and dioxide, and methane, from a handful of the easiest targets.

    NASA/ESA Hubble Telescope

    NASA/Spitzer Infrared Telescope

    Most are “hot Jupiters”—big planets in close-in orbits, their atmospheres puffed up by the heat of their star.

    3
    In an artist’s concept, a petaled starshade flying at a distance of tens of thousands of kilometers from a space telescope blocks a star’s light, opening a clear view of its planets. NASA/JPL.

    The approach will pay much greater dividends after the launch of the JWST in 2019. Its 6.5-meter mirror will collect far more light from candidate stars than existing telescopes can, allowing it to tease out fainter exoplanet signatures, and its spectrographs will produce much better data.

    4
    https://jwst.nasa.gov/mirrors.html

    And it will be sensitive to the infrared wavelengths where the absorption lines of molecules such as water, methane, and carbon monoxide and dioxide are most prominent.

    Once astronomers have such spectra, one of the main gases that they hope to find is oxygen. Not only does it have strong and distinctive absorption lines, but many believe its presence is the strongest sign that life exists on a planet.

    Oxygen-producing photosynthesis made Earth what it is today. First cyanobacteria in the oceans and then other microbes and plants have pumped out oxygen for billions of years, so that it now makes up 21% of the atmosphere—an abundance that would be easily detectable from afar. Photosynthesis is evolution’s “killer app,” says Victoria Meadows, head of the NASA-sponsored Virtual Planet Laboratory (VPL) at the University of Washington in Seattle. It uses a prolific source of energy, sunlight, to transform two molecules thought to be common on most terrestrial planets—water and carbon dioxide—into sugary fuel for multicellular life. Meadows reckons it is a safe bet that something similar has evolved elsewhere. “Oxygen is still the first thing to go after,” she says.

    Fifteen years ago, when exoplanets were new and researchers started thinking about how to scan them for life, “Champagne would have flowed” if oxygen had been detected, Meadows recalls. But since then, researchers have realized that things are not that simple: Lifeless planets can have atmospheres full of oxygen, and life can proliferate without ever producing the gas. That was the case on Earth, where, for 2 billion years, microbes practiced a form of photosynthesis that did not produce oxygen or many other gases. “We’ve had to make ourselves more aware of how we could be fooled,” Meadows says.

    To learn what a genuine biosignature might look like, and what might be a false alarm, Meadows and her colleagues at the VPL explore computer models of exoplanet atmospheres, based on data from exoplanets as well as observations of more familiar planets, including Earth. They also do physical experiments in vacuum chambers. They recreate the gaseous cocktails that may surround exoplanets, illuminate them with simulated starlight of various kinds, and see what can be measured.

    Over the past few years, VPL researchers have used such models to identify nonbiological processes that could make oxygen and produce a “false positive” signal. For example, a planet with abundant surface water might form around a star that, in its early years, surges in brightness, perhaps heating the young planet enough to boil off its oceans. Intense ultraviolet light from the star would bombard the resulting water vapor, perhaps splitting it into hydrogen and oxygen. The lighter hydrogen could escape into space, leaving an atmosphere rich in oxygen around a planet devoid of life. “Know thy star, know thy planet,” recites Siddharth Hegde of Cornell University’s Carl Sagan Institute.

    Discovering methane in the same place as oxygen, however, would strengthen the case for life. Although geological processes can produce methane, without any need for life, most methane on Earth comes from microbes that live in landfill sites and in the guts of ruminants. Methane and oxygen together make a redox pair: two molecules that will readily react by exchanging electrons. If they both existed in the same atmosphere, they would quickly combine to produce carbon dioxide and water. But if they persist at levels high enough to be detectable, something must be replenishing them. “It’s largely accepted that if you have redox molecules in large abundance they must be produced by life,” Hegde says.

    Some argue that by focusing on oxygen and methane—typical of life on Earth—researchers are ignoring other possibilities. If there is one thing astronomers have learned about exoplanets so far, it is that familiar planets are a poor guide to exoplanets’ huge diversity of size and nature. And studies of extremophiles, microbes that thrive in inhospitable environments on Earth, suggest life can spring up in unlikely places. Exobiology may be entirely unlike its counterpart on Earth, and so its gaseous byproducts might be radically different, too.

    But what gases to look for? Seager and her colleagues compiled a list of 14,000 compounds that might exist as a gas at “habitable” temperatures, between the freezing and boiling points of water; to keep the list manageable they restricted it to small molecules, with no more than six nonhydrogen atoms. About 2500 are made of the biogenic atoms carbon, nitrogen, oxygen, phosphorus, sulfur, and hydrogen, and about 600 are actually produced by life on Earth. Detecting high levels of any of these gases, if they can’t be explained by nonbiological processes, could be a sign of alien biology, Seager and her colleagues argue.


    A. CUADRA/SCIENCE

    Light shining through the atmospheres of transiting exoplanets is likely to be the mainstay of biosignature searches for years to come. But the technique tends to sample the thin upper reaches of a planet’s atmosphere; far less starlight may penetrate the thick gases that hug the surface, where most biological activity is likely to occur. The transit technique also works best for hot Jupiters, which by nature are less likely to host life than small rocky planets with thinner atmospheres. The JWST may be able to tease out atmospheric spectra from small planets if they orbit small, dim stars like red dwarfs, which won’t swamp the planet’s spectrum. But these red dwarfs have a habit of spewing out flares that would make it hard for life to establish itself on a nearby planet.

    To look for signs of life on a terrestrial planet around a sunlike star, astronomers will probably have to capture its light directly, to form a spectrum or even an actual image. That requires blocking the overwhelming glare of the star. Ground-based telescopes equipped with “coronagraphs,” which precisely mask a star so nearby objects can be seen, can now capture only the biggest exoplanets in the widest orbits. To see terrestrial planets will require a similarly equipped telescope in space, above the distorting effect of the atmosphere. NASA’s Wide Field Infrared Survey Telescope (WFIRST), expected to launch in the mid-2020s, is meant to fill that need.

    NASA/WFIRST

    Even better, WFIRST could be used in concert with a “starshade”—a separate spacecraft stationed 50,000 kilometers from the telescope that unfurls a circular mask tens of meters across to block out starlight. A starshade is more effective than a coronagraph at limiting the amount of light going into the telescope. It not only blocks the star directly, but also suppresses diffraction with an elaborate petaled edge. That reduces the stray scattered light that can make it hard to spot faint planets. A starshade is a much more expensive prospect than a coronagraph, however, and aligning telescope and starshade over huge distances will be a challenge.

    Direct imaging will provide much better spectra than transit observations because light will pass through the full depth of the planet’s atmosphere twice, rather than skimming through its outer edges. But it also opens up the possibility of detecting life directly, instead of through its waste gases in the atmosphere. If organisms, whether they are plants, algae, or other microbes, cover a large proportion of a planet’s surface, their pigments may leave a spectral imprint in the reflected light. Earthlight contains an obvious imprint of this sort. Known as the “red edge,” it is the dramatic change in the reflectance of green plants at a wavelength of about 720 nanometers. Below that wavelength, plants absorb as much light as possible for photosynthesis, reflecting only a few percent. At longer wavelengths, the reflectance jumps to almost 50%, and the brightness of the spectrum rises abruptly, like a cliff. “An alien observer could easily tell if there is life on Earth,” Hegde says.

    There’s no reason to assume that alien life will take the form of green plants. So Hegde and his colleagues are compiling a database of reflectance spectra for different types of microbes. Among the hundreds the team has logged are many extremophiles, which fill marginal niches on Earth but may be a dominant life form on an exoplanet. Many of the microbes on the list have not had their reflectance spectra measured, so the Cornell team is filling in those gaps. Detecting pigments on an exoplanet surface would be extremely challenging. But a tell-tale color in the faint light of a distant world could join other clues—spectral absorption lines from atmospheric gases, for example—to form “a jigsaw puzzle which overall gives us a picture of the planet,” Hegde says.

    None of the telescopes available now or in the next decade is designed specifically to directly image exoplanets, so biosignature searches must compete with other branches of astronomy for scarce observing time. What researchers really hanker after is a large space telescope purpose-built to image Earth-like alien worlds—a new incarnation of the idea behind NASA’s ill-fated Terrestrial Planet Finder.

    The Habitable Exoplanet Imaging Mission, or HabEx, a mission concept now being studied by NASA, could be the answer. Its telescope would have a mirror up to 6.5 meters across—as big as the JWST’s—but would be armed with instruments sensitive to a broader wavelength range, from the ultraviolet to the near-infrared, to capture the widest range of spectral biosignatures. The telescope would be designed to reduce scattered light and have a coronagraph and starshade to allow direct imaging of Earth-sized exoplanets.

    Such a mission would reveal Earth-like planets at a level of detail researchers can now only dream about—probing atmospheres, revealing any surface pigments, and even delivering the sort of blocky surface images that Kane has been simulating. But will that be enough to conclude we are not alone in the universe? “There’s a lot of uncertainty about what would be required to put the last nail in the coffin,” Kane says. “But if HabEx is built according to its current design, it should provide a pretty convincing case.”

    4
    NASA HabEx: The Planet Hunter

    See the full article here .

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