Between a Rock and a Hard Place

Charly Stamper

Charly completed a PhD in experimental petrology. She used to make pretend volcanoes; now she works in renewable energy. Charly tweets at @C_Stamper.

Science snap (#12): Purple bacteria

KT Cooper is a PhD student in the School of Earth Sciences at the University of Bristol. A carbonate geochemist by training, she has just returned from a three-month secondment to Houston, Texas, USA working with Exxon Mobil.

The world of microbiology is weird, wonderful and also quite multi-colourful. Purple bacteria, a particular hue of microbe which holds a special place in my heart, have just taken the spotlight when it comes to the search for life on other planets. These bacteria were known to dominate life on the early Earth, around 3 Ga ago, and can survive on land and in water.

Water sample full of purple bacteria taken from a blue hole on North Andros as part of my PhD research, courtesy of Didi Ooi

They produce their energy through photosynthesis, like plants, and it has been suggested they could be used to harvest solar energy (highly efficient solar panels could utilise the bacteria’s natural ability to adapt to varying light intensities). They also have a highly reflective nature and it is this that has been proposed to be used in the hunt for life on other planets.

An extensive research effort exists to investigate how Earth might look like from distant observers so that we maybe able to identify other planets out there that could harbour life. Many different remote sensing and imaging techniques are being used but the research is not only focused on the Earth as it is now, but also as how it may have looked in a more primitive state. Computer models have been used to investigate if the Earth were covered in purple bacteria how this may be imaged from space. This research hopes to help identify life, albeit less little green men and more really little purple bacteria, on other planets.

Using garnet geochemistry to investigate the lithospheric mantle beneath northern Tanzania

Sorcha McMahon is a third year PhD student in the School of Earth Sciences at the University of Bristol. Sorcha is investigating how strange igneous rocks called carbonatites may have formed, using both natural samples and high-pressure experiments.

As part of my undergraduate MSci course at the University of Cambridge, I carried out a project investigating a collection of thin sections from peridotite xenoliths from northern Tanzania. The main aim of this research was to constrain the petrogenetic evolution of the lithospheric mantle beneath the East African Rift (EAR) and adjacent Tanzanian Craton. Techniques employed included the electron microprobe (EMPA) and LA-ICP-MS to characterise the major and trace element contents of constituent minerals in garnet-bearing lherzolite and harzburgite mantle xenoliths. For the first time globally, we found ultra-depleted pyrope garnets from Lashaine peridotites displaying rare earth element (REE) patterns similar to those of hypothetical garnets proposed to have formed in the subcontinental lithospheric mantle prior to any metasomatism*.

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What’s up in Bolivia?

James Hickey is a PhD student in the School of Earth Sciences at the University of Bristol. A geophysicist and volcanologist by trade, his PhD project is focussed on attempting to place constraints on volcanic unrest using integrated geodetic modelling.

To many, Bolivia is just an unassuming landlocked country in South America, perhaps most famous for its coca tea obsession and ‘gap yah’ alpaca wool sweaters. But to a number of enthused volcanologists it is a near-perfect playground. In the southwest of the country, sitting at 6008 m above sea level (ASL), Uturuncu volcano is inflating, and inflating over an unprecedented scale.

Uturuncu Volcano in the background with a gravimeter and campaign GPS setup in front. Image credit: James Hickey.

Uturuncu Volcano in the background with a gravimeter and campaign GPS setup in front. Image credit: James Hickey.

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An ode to metamorphism

On finding out my ‘profession’, there’s one fact that people proudly announce to me on a regular basis: “I know the three rock types: sedimentary, igneous and metamorphic!”. What usually emerges from deeper probing is that most people are comfortable with the concept of sediments and magma, but metamorphism is a bit of an enigma. Like the mysterious stranger, lurking in a dark forgotten corner, it is true to say that for most people, this holds even throughout undergraduate geology courses.

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