Search Box

Friday, August 5, 2016

Bacteria Can Show Us When Earth's Magnetic Field Flipped

Bacteria Can Show Us When Earth's Magnetic Field Flipped

Like tiny compasses.

Fiona MacDonald | August 4, 2016

Most of us take Earth's magnetic field - and our faithful north and south poles - for granted. Like a giant bar magnet, the magnetic field is always there, protecting us from space radiation and helping migratory animals to navigate around the world.
But the planet's magnetic field hasn't always been like this, and it won't stay this way forever. In fact, the poles are already starting to shift, and researchers predict that at some point, they'll flip, just like they've done many times in the past.

"Scientists filled this container with water, groundwater bacteria, iron, food, and sand. Two years later, they found a reddish sludge, visible here, containing mineral crystals large enough to preserve a magnetic signature for billions of years." Source:
(Is the Earth’s magnetic field about to flip? February 5, 2009) Source:

<more at; related articles and links: (Bacteria Preserve Record of Earth's Magnetic Fields. 
Tiny yet stable magnetized particles created by microbes long ago could help scientists better determine the strength and orientation of ancient magnetic fields. August 1, 2016) and (Magnetic properties of iron minerals produced by natural iron- and manganese-reducing groundwater bacteria. Alexandra Abrajevitch, Lubov M. Kondratyeva, Evgeniya M. Golubeva, Kazuto Kodama and Rie S. Hori. Geophysical Journal International, Volume 206, Issue 2, pp. 1340-1351. [Abstract: Understanding the contribution of biogenic magnetic particles into sedimentary assemblages is a current challenge in palaeomagnetism. It has been demonstrated recently that magnetic particles produced through biologically controlled mineralization processes, such as magnetosomes from magnetotactic bacteria, contribute to the recording of natural remanent magnetization in marine and lacustrian sediments. Contributions from other, biologically induced, mineralization types, which are known from multiple laboratory experiments to include magnetic minerals, remain largely unknown. Here, we report magnetic properties of iron minerals formed by a community of iron- and manganese-reducing bacteria isolated from a natural groundwater deposit during a 2 yr long incubation experiment. The main iron phases of the biomineralized mass are lepidocrocite, goethite and magnetite, each of which has environmental significance. Unlike the majority of the previous studies that reported superparamagnetic grain size, and thus no remanence carrying capacity of biologically induced magnetite, hysteresis and first-order reversal curves measurements in our study have not detected significant superparamagnetic contribution. The biomineralized mass, instead, contains a mixture of single-domain to pseudo-single-domain and multidomain magnetite particles that are capable of carrying a stable chemical remanent magnetization. Isothermal remanent magnetization acquisition parameters and first-order reversal curves signatures of the biomineralized samples deviate from previously proposed criteria for the distinction of extracellular (biologically induced) magnetic particles in mixtures. Given its potential significance as a carrier of natural remanent magnetization, environmental requirements, distribution in nature and the efficiency in the geomagnetic field recording by biologically induced mineralization need comprehensive investigation.])>

No comments:

Post a Comment