Astrobiology

  • Article
    | Open Access

    The search for life in the universe is difficult due to issues with defining signatures of living systems. Here, the authors present an approach based on the molecular assembly number and tandem mass spectrometry that allows identification of molecules produced by biological systems, and use it to identify biosignatures from a range of samples, including ones from outer space.

    • Stuart M. Marshall
    • , Cole Mathis
    •  & Leroy Cronin
  • Article
    | Open Access

    The evolution of multicellular life is hypothesized to have been promoted by rising oxygen levels. Through experimental evolution and modeling, Bozdag et al. demonstrate that our planet’s first oxygenation would have strongly constrained, not promoted, the evolution of multicellular life.

    • G. Ozan Bozdag
    • , Eric Libby
    •  & William C. Ratcliff
  • Article
    | Open Access

    Determining the origins of life on Earth is confounded by the fact that the sources of nutrients necessary to create early life forms remain mysterious. Here the authors show that lightning strikes could have supplied a major source of essential phosphorus on early Earth.

    • Benjamin L. Hess
    • , Sandra Piazolo
    •  & Jason Harvey
  • Article
    | Open Access

    This manuscript tackles the origin of organic molecules in carbonaceous meteorites. Identifying hexamethylenetetramine in three carbonaceous meteorites, the authors propose formation from ammonia and formaldehyde by photochemical and thermal reactions in the interstellar medium, followed by the incorporation into planetary systems.

    • Yasuhiro Oba
    • , Yoshinori Takano
    •  & Shogo Tachibana
  • Article
    | Open Access

    In the habitable zone concept, a planet’s carbon dioxide-water greenhouse maintains surface liquid water. Here, the authors estimate how many Earthlike exoplanets are needed to detect a relationship between stellar flux and the atmospheric carbon dioxide predicted by carbon cycle modeling.

    • Owen R. Lehmer
    • , David C. Catling
    •  & Joshua Krissansen-Totton
  • Article
    | Open Access

    Rare earth elements are used in electronics, but increase in demand could lead to low supply. Here the authors conduct experiments on the International Space Station and show microbes can extract rare elements from rocks at low gravity, a finding that could extend mining potential to other planets.

    • Charles S. Cockell
    • , Rosa Santomartino
    •  & René Demets
  • Article
    | Open Access

    Formation of peptide bonds in cold gas-phase environments might represent a prebiotic synthesis route of polypeptides. Here, the authors show the formation of up to tetra-peptide species in the collision of He2+ ions, with kinetic energies typical for solar wind ions, with cold β-alanine clusters.

    • Patrick Rousseau
    • , Dariusz G. Piekarski
    •  & Bernd A. Huber
  • Article
    | Open Access

    Mars has long been thought to contain organic compounds, but the origins and plausibility are debated. Here the authors employ a new technique to assess organic nitrogen compounds in a Martian meteorite, concluding that these compounds are indeed likely to originate from the Red Planet.

    • Mizuho Koike
    • , Ryoichi Nakada
    •  & Atsuko Kobayashi
  • Article
    | Open Access

    The formation of nucleobases can take place in extraterrestrial environments. Here the authors show the simultaneous synthesis of three purine nucleobases and three pyrimidine from interstellar ice analogues that suggest the evolution from molecular clouds to stars and planets provide suitable environment for nucleobase synthesis in space.

    • Yasuhiro Oba
    • , Yoshinori Takano
    •  & Akira Kouchi
  • Article
    | Open Access

    Cyanide is thought to be crucial for the origin of life. Here, the authors showed that iron cyanocarbonyl complexes are present in meteorites and propose that these compounds were a source of free cyanide on early Earth and served as precursors to the active sites of ancient hydrogenases.

    • Karen E. Smith
    • , Christopher H. House
    •  & Michael P. Callahan
  • Article
    | Open Access

    Red beds contain reduction spheroids that formed underground millions of years ago and whose origin remains poorly constrained. Here the authors use uranium isotopes to identify ancient fingerprints of bacteria in these features, confirming that they were produced by subsurface life in the geological past.

    • Sean McMahon
    • , Ashleigh v. S. Hood
    •  & Stephen Bowden
  • Article
    | Open Access

    Many methanogenic archaea use H2 and CO2 to produce methane. Here, Taubner et al. show that Methanothermococcus okinawensis produces methane under conditions extrapolated for Saturn’s icy moon, Enceladus, and estimate that serpentinization may produce sufficient H2 for biological methane production.

    • Ruth-Sophie Taubner
    • , Patricia Pappenreiter
    •  & Simon K.-M. R. Rittmann
  • Article
    | Open Access

    Significant amounts of different perchlorate salts have been discovered on the surface of Mars. Here, the authors show that magnesium perchlorate has a major impact on water structure in solution, providing insight into how an aqueous fluid might exist under the sub-freezing conditions present on Mars.

    • Samuel Lenton
    • , Natasha H. Rhys
    •  & Lorna Dougan
  • Article
    | Open Access

    The Eridania basin on Mars was once the site of a vast inland sea. Here, the authors show that the most ancient materials in the Eridania basin were formed in a deep-water hydrothermal setting and may be an analogue for early environmental conditions on Earth.

    • Joseph R. Michalski
    • , Eldar Z. Noe Dobrea
    •  & Javier Cuadros
  • Article
    | Open Access

    Large variations in insolation experienced by circumbinary planets raise the question of the habitability of such planets. Here, the authors show that while the changing insolation does not radically affect habitability, it does impact on the planet’s climate and on the interpretation of future observations.

    • Max Popp
    •  & Siegfried Eggl
  • Article
    | Open Access

    Extremophiles on Earth are known to respire methane, and the potential existence of methane on Mars indicates similar organisms could survive there. Here, the authors present data from Martian meteorites confirming the presence of methane, indicating that a habitat capable of supporting organisms exists on Mars.

    • Nigel J. F. Blamey
    • , John Parnell
    •  & Roberta L. Flemming