Magnetic Phase at the surface of Mars
A remarkable result from the Viking mission was the discovery that the martian soil is highly magnetic in the sense that the soil is attracted by a small permanent magnet. This result was remarkable in that similar looking red soils on Earth are rather seldom as magnetic as the soil found on Mars.
The martian soil -- at both landing sites -- adhered almost equally well to a strong and a weak permanent magnet attached to the Viking Lander backhoe. The strong magnet had a magnetic field and field gradient of 0.25 Tesla (T) and 100 Tm, respectively. The corresponding numbers for the weak magnet were 0.07 T and 30 Tm. Based on the returned pictures of the amount of soil clinging to the magnets, it was estimated that the particles in the martian dust contain between 1% and 7% of a strongly magnetic phase, most probably a ferrimagnetic oxide intimately dispersed throughout the soil. Limits for the spontaneous magnetization of the martian soil are: 1 Am(kg soil) 7 Am(kg soil).
The magnetic phase in the soil will contain information on the processes by which the soil has formed. If the magnetic phase contains the element titanium, i.e. if the phase is either titanomagnetite or titanomaghemite, the magnetic phase will have been inherited from the underlying basaltic rocks. If, however, the magnetic mineral has formed via precipitation in abundant liquid water, the mineral will be a rather pure iron oxide, perhaps containing some aluminium.
The ion responsible for the magnetic properties of oxides is often Fe, and spectroscopic studies have shown that Fe compounds are also the cause of the reddish colour of Mars. In a detailed study of the reflection spectrum of Mars at high spectral resolution during the favourable 1988 opposition, two essential facts were demonstrated. First, by a careful study of one of the crystal field absorption features (at 630 nm) it was clarified that at least some crystalline ferric oxide or oxyhydroxide minerals must be present on Mars. Next, the fact that the reflection spectrum falls off rather slowly in the blue end of the visible spectrum shows that most of the Fe seem to be present in compounds with a distribution of crystal fields at the Fe sites. These results point to the presence of amorphous iron compounds or (more likely) ultra small (d 10 nm) crystalline iron oxide particles (hematite). Such so called nanophase hematite particles are superparamagnetic. Superparamagnetic hematite is substantially more magnetic ( 4 Amkg) than bulk hematite particles ( = 0.4Amkg).
Various minerals have been suggested as the cause of the magnetism of the martian soil. Let us mention maghemite (g-Fe2O3), magnetite (Fe3O4), feroxyhite ( -FeOOH), superparamagnetic hematite (a-Fe2O3) and titanomaghemite. The magnetic phase in the martian soil may occur as discrete single phase ferrimagnetic particles. Alternatively, the magnetic phase may occur as part of composite multi-phase particles. In composite particles the magnetic phase(s) may occur as pigmentary ultra small particles dispersed throughout the volume of silicate (e.g. smectite clay) particles, or the magnetic phase may occur as a coating (precipitates or weathering rinds) on silicate (clay) particles.
If the magnetism of the soil is caused by superparamagnetic particles it will raise some questions. For example: What is the type of weathering on Mars that has led to the formation of a soil containing most of its iron in nanophase particles? Be that as it may, there can be no doubt that an identification of the magnetic phase in the soil of Mars will lead to a deeper insight into the history of the martian surface, including insight into the role of liquid water in the formation of the soil.
We will collect bottom sediment which should contain magnetotactic bacteria THINK ABOUT THE POSSIBILITIES SINCE WE ARE CLOSE TO THE MAGNETIC EQUATOR. The websites will provide the information about the collection and observation of magnetotactic bacteria that anyone near a lake or pond could collect.
http://quest.arc.nasa.gov/mars/teachers/tg/program3/3.3.html mars soil
The Teacher/ Scientists suggested that the expedition should examine the termite mounds for evidence of magnetic particles. Below is a description of apparent biomineralization in termites.
MAGNETITE BIOMINERALISATION IN TERMITES.
Barbara A Maher School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, U.K.
Experimental evidence exists for magnetoreception in termites, a major component of the soil macrofauna in many tropical countries. This preliminary study identifies for the first time the presence of biogenic ferrimagnets (magnetite?) in two species of termite (Nasutitermes exitiosus and Amitermes meridionalis), based on magnetic measurements of whole termite specimens and individual body sections, and analysis by electron microscopy of magnetically-extracted grains. The magnetic measurements indicate the presence of very small concentrations of magnetic material, with more magnetic grains in the thorax/abdomen region compared to the head. Magnetic interaction, due to clustering of grains, is also identified by the measurements. Analysis of magnetic extracts by transmission electron microscopy identifies the presence of uniquely ultrafine (10nm) and unidimensional grains of ferrimagnetic material, unequivocally distinct from any possible extraneous magnetite sources, such as ingested soil. Hence, this provides firm evidence for biogenic formation of this magnetic material by these two termite species. Such ultrafine grains would be superparamagnetic, ie. incapable of carrying a permanent magnetic moment, unless they were sited in clusters of interacting grains, when some remanence-carrying ability - and hence magnetotaxis - would be possible.
The species Amitermes meridionalis builds "magnetic mounds" near Darwin in the Northern Territory of Australia. These mounds are oriented in the north-south direction.