A new test for life on other planets:

Discussion in 'Astronomy, Exobiology, & Cosmology' started by paddoboy, Jan 27, 2017.

  1. paddoboy Valued Senior Member

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    A new test for life on other planets
    January 27, 2017 by Andrew Good

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    Mono Lake, California, with salt pillars known as "tufas" visible. JPL scientists tested new methods for detecting chemical signatures of life in the salty waters here, believing them to be analogs for water on Mars or ocean worlds like Europa. Credit: Mono County Tourism.
    A simple chemistry method could vastly enhance how scientists search for signs of life on other planets.

    The test uses a liquid-based technique known as capillary electrophoresis to separate a mixture of organic molecules into its components. It was designed specifically to analyze for amino acids, the structural building blocks of all life on Earth. The method is 10,000 times more sensitive than current methods employed by spacecraft like NASA's Mars Curiosity rover, according to a new study published in Analytical Chemistry. The study was carried out by researchers from NASA's Jet Propulsion Laboratory, Pasadena, California.




    Read more at: https://phys.org/news/2017-01-life-planets.html#jCp
     
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  3. paddoboy Valued Senior Member

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    http://pubs.acs.org/doi/abs/10.1021/acs.analchem.6b04338

    Enhanced Resolution of Chiral Amino Acids with Capillary Electrophoresis for Biosignature Detection in Extraterrestrial Samples:

    Abstract

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    Amino acids are fundamental building blocks of terrestrial life as well as ubiquitous byproducts of abiotic reactions. In order to distinguish between amino acids formed by abiotic versus biotic processes it is possible to use chemical distributions to identify patterns unique to life. This article describes two capillary electrophoresis methods capable of resolving 17 amino acids found in high abundance in both biotic and abiotic samples (seven enantiomer pairs d/l-Ala, -Asp, -Glu, -His, -Leu, -Ser, -Val and the three achiral amino acids Gly, β-Ala, and GABA). To resolve the 13 neutral amino acids one method utilizes a background electrolyte containing γ-cyclodextrin and sodium taurocholate micelles. The acidic amino acid enantiomers were resolved with γ-cyclodextrin alone. These methods allow detection limits down to 5 nM for the neutral amino acids and 500 nM for acidic amino acids and were used to analyze samples collected from Mono Lake with minimal sample preparation.

     
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  5. paddoboy Valued Senior Member

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    Just to think, that only 20 or so years ago, we did not even have evidence for extra-solar planets!
     
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  7. paddoboy Valued Senior Member

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    https://en.wikipedia.org/wiki/Discoveries_of_exoplanets

    An exoplanet (extrasolar planet) is a planet located outside the Solar System. The first confirmed detection of exoplanets was announced in 1992, with two planets found orbiting a pulsar. The first confirmation of an exoplanet orbiting a main-sequence star was made in 1995, when a giant planet was found in a four-day orbit around the nearby star 51 Pegasi. Some exoplanets have been imaged directly by telescopes, but the vast majority have been detected through indirect methods such as the transit method and the radial-velocity method. As of January 22, 2017, astronomers have identified 3,565 such planets (in 2,675 planetary systems and 602 multiple planetary systems).[1] This is a list of the most notable discoveries.
     
  8. Ophiolite Valued Senior Member

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    The issue I have with the methodology is its strong geocentric bias:
    1. It assumes extraterrestrial life will make extensive use of amino acids.
    2. It assumes these will be pretty much the same amino acids as used by Earth life.
    3. It assumes the ratios of extraterrestrial biological amino acids will be pretty much the sames as ours.

    These positions seem overly presumptive. That said, this is clearly a major advance in detecting life forms similar to ours.
     
  9. exchemist Valued Senior Member

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    The way I read it, one of the chief advantages of the technique is to distinguish between the different enantiomers of each amino acid. If it is assumed that amino acids of biotic origin will exhibit handedness, i.e. one enantiomer will be present at a higher concentration than the other, as in terrestrial life, then this would be a signature of life. I can see that if such a difference were detected it would very strongly suggest that life was responsible. However the converse would presumably not be true, since we have no real reason to think that all possible biochemistries must exhibit handedness. We don't know why handedness arose in terrestrial life, though there are some tantalising ideas about how it could have come about, involving adsorption of molecules on certain inorganic crystals.
     
  10. exchemist Valued Senior Member

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    Paddo I think this belongs in a different thread. The technique you opened the thread with is an analytical technique that requires a spacecraft to be physically sampling the water on the planet. So unlike, say, spectroscopic techniques, this method can't be applied to planets in other solar systems.
     
  11. Ophiolite Valued Senior Member

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    Yes, I should have read more carefully and not jumped to a concussion. The word "chiral" is even in the title. I'm not sure why I decided on talking about ratios. I suppose because chirality is a simple ratio.

    My reservations about the methodology remain though: excellent for detecting Earth like life, possibly useless for detecting true aliens.

    I was at the University of Glasgow when Cairns-Smith was doing his early thinking on the role of clays in abiogenesis. I kick myself on a regular basis for not having sought him out to discuss his ideas!
     
  12. exchemist Valued Senior Member

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    Did he work on chirality? I am aware of some recent work by Hazen - thanks to another poster on this forum actually, on different adsorption preference of minerals with chiral surfaces (calcite being one I seem to recall), but I thought that was all very recent. But I have always been attracted to the idea that mineral adsorption might have played a role. One does need something to enable the formation of long chain molecules in spite of the entropy reduction involved and the competing processes at work.
     
  13. paddoboy Valued Senior Member

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    I agree.....I often myself use the phrase, "life as we know it"
     
  14. paddoboy Valued Senior Member

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    OK, I see....my booboo.

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  15. paddoboy Valued Senior Member

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    A few papers on extra solar planets, their characteristics, and their suitability for life.....
    https://arxiv.org/ftp/arxiv/papers/0911/0911.2936.pdf
    Exoplanet Characterization and the Search for Life:

    Abstract:
    Over 300 extrasolar planets (exoplanets) have been detected orbiting nearby stars. We now hope to conduct a census of all planets around nearby stars and to characterize their atmospheres and surfaces with spectroscopy. Rocky planets within their star’s habitable zones have the highest priority, as these have the potential to harbor life. Our science goal is to find and characterize all nearby exoplanets; this requires that we measure the mass, orbit, and spectroscopic signature of each one at visible and infrared wavelengths. The techniques for doing this are at hand today. Within the decade we could answer long-standing questions about the evolution and nature of other planetary systems, and we could search for clues as to whether life exists elsewhere in our galactic neighborhood.
     
  16. paddoboy Valued Senior Member

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    https://arxiv.org/pdf/1404.0641.pdf

    Age Aspects of Habitability

    Abstract

    A habitable zone of a star is defined as a range of orbits within which a rocky planet can support liquid water on its surface. The most intriguing question driving the search for habitable planets is whether they host life. But is the age of the planet important for its habitability? If we define habitability as the ability of a planet to beget life, then probably it is not. After all, life on Earth has developed within only 800 Myr after its formation — the carbon isotope change detected in the oldest rocks indicates the existence of already active life at least 3.8 Gyr ago. If, however, we define habitability as our ability to detect life on the surface of exoplanets, then age becomes a crucial parameter. Only after life had evolved sufficiently complex to change its environment on a planetary scale, can we detect it remotely through its imprint on the atmosphere — the so-called biosignatures, out of which the photosynthetic oxygen is the most prominent indicator of developed (complex) life as we know it. Thus, photosynthesis is a powerful biogenic engine that is known to have changed our planets global atmospheric properties. The importance of planetary age for the detectability of life as we know it follows from the fact that this primary process, photosynthesis, is endothermic with an activation energy higher than temperatures in habitable zones, and is sensitive to the particular thermal conditions of the planet. Therefore, the onset of photosynthesis on planets in habitable zones may take much longer time than the planetary age. The knowledge of the age of a planet is necessary for developing a strategy to search for exoplanets carrying complex (developed) life — many confirmed potentially habitable planets are too young (orbiting Population I stars) and may not have had enough time to develop and/or sustain detectable life. In the last decade, many planets orbiting old (9–13 Gyr) metal-poor Population II stars have been discovered. Such planets had had enough time to develop necessary chains of chemical reactions and may carry detectable life if located in a habitable zone. These old planets should be primary targets in search for the extraterrestrial life.
     
  17. paddoboy Valued Senior Member

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    https://arxiv.org/ftp/arxiv/papers/0906/0906.2263.pdf

    Deciphering Spectral Fingerprints of Habitable Extrasolar Planets

    Abstract:

    In this paper we discuss how we can read a planet’s spectrum to assess its habitability and search for the signatures of a biosphere. After a decade rich in giant exoplanet detections, observation techniques have now reached the ability to find planets of less than 10 MEarth (so called Super-Earths) that may potentially be habitable. How can we characterize those planets and assess if they are habitable? The new field of extrasolar planet search has shown an extraordinary ability to combine research by astrophysics, chemistry, biology and geophysics into a new and exciting interdisciplinary approach to understand our place in the universe. The results of a first generation mission will most likely result in an amazing scope of diverse planets that will set planet formation, evolution as well as our planet in an overall context.
     

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