Hematite Spherules on Mars

In 2004, the observation of large amounts of hematite spherules on Mars by the NASA’s Mars Exploration Rover “Opportunity,” which landed in Eagle crater on Meridiani Planum, created tremendous excitement among the scientific community. The discovery of hematite was significant as it suggests past presence of water on Mars. Furthermore, the hematite spherules were widely suggested to be concretions that formed by precipitation of aqueous fluids. Among the various observed mysteries of Martian hematite spherules, also known as “blueberries,” one regarding to their size limit was very puzzling. All of the millions of blueberries observed on Mars were smaller than 6.2 mm in diameter. Because the concretions on Earth are not limited in size, the formation of the Martian blueberries became difficult to explain. In this chapter, we will discuss the observed properties of Martian hematite spherules and explain why a cosmic spherule formation mechanism provides a possible solution to the puzzling observations on Mars

Enhancement of the Anti-Stokes Fluorescence of Hollow Spherical Carbon Nitride Nanostructures by High Intensity Green Laser

Fluorescence spectra of graphitic (g-C3N4) and spherical (s-C3N4) modifications of carbon nitride were measured as a function of green pulsed (6 ns-pulse) laser intensity. It was found that the intensity of the laser increases the maximum of the fluorescence shifts towards the anti-Stokes side of the fluorescence for s-C3N4 spherical nanoparticles. This phenomenon was not observed for g-C3N4 particles. The maximum of the anti-Stokes fluorescence in s-C3N4 nanoparticles was observed at 480 nm. The ratio of the intensity of the anti-Stokes peak (centered at 480 nm) to that of the Stokes peak (centered at 582 nm) was measured to be I484/582 = 6.4 × 10−3 at a low level of intensity (5 mW) of a green pulsed laser, whereas it rose to I484/582 = 2.27 with a high level of laser intensity (1500 mW)

Cryogenic Minerals in Hawaiian Lava Tubes: A Geochemical and Microbiological Exploration

The Mauna Loa volcano, on the Island of Hawaii, has numerous young lava tubes. Among them, two at high altitudes are known to contain ice year-round: Mauna Loa Icecave (MLIC) and the Arsia Cave. These unusual caves harbor cold, humid, dark, and biologically restricted environments. Secondary minerals and ice were sampled from both caves to explore their geochemical and microbiological characteristics. The minerals sampled from the deep parts of the caves, where near freezing temperatures prevail, are all multi-phase and consist mainly of secondary amorphous silica SiO2, cryptocrystalline calcite CaCO3, and gypsum CaSO4·2H2O. Based on carbon and oxygen stable isotope ratios, all sampled calcite is cryogenic. The isotopic composition of falls on the global meteoric line, indicating that little evaporation has occurred. The microbial diversity of a silica and calcite deposit in the MLIC and from ice pond water in the Arsia Cave was explored by analysis of ∼50,000 small subunit ribosomal RNA gene fragments via amplicon sequencing. Analyses reveal that the Hawaiian ice caves harbor unique microbial diversity distinct from other environments, including cave environments, in Hawaii and worldwide. Actinobacteria and Proteobacteria were the most abundant microbial phyla detected, which is largely consistent with studies of other oligotrophic cave environments. The cold, isolated, oligotrophic basaltic lava cave environment in Hawaii provides a unique opportunity to understand microbial biogeography not only on Earth but also on other planets