Imperial College London

ProfessorMarkSephton

Faculty of EngineeringDepartment of Earth Science & Engineering

Head of the Department of Earth Science and Engineering
 
 
 
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Contact

 

+44 (0)20 7594 6542m.a.sephton Website

 
 
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Assistant

 

Ms Daphne Salazar +44 (0)20 7594 7401

 
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Location

 

G30 (via G28)Royal School of MinesSouth Kensington Campus

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Summary

 

Overview

Organic matter is a sensitive indictor of life and the environments in which it exists. There are many applications for organic-based methods and a selection is described below. The work occurs within the Imperial College Organic Geochemistry group.

Organic matter in meteorites

It is widely considered that the earliest living organisms arose from simple prebiotic organic compounds  by a process of chemical evolution. The Earth-based record of pre-biotic chemical evolution has been obliterated by geological processing. However, remains of the materials that were involved in the construction of the Earth are preserved in ancient asteroids, fragments of which are naturally-delivered to the Earth as meteorites. Carbonaceous chondrites are a particularly primitive class of meteorite that contain many of the compound classes utilised by life. Chondritic organic matter represents pre-life organic chemistry that has been frozen in time. By fully understanding the reactions that led to its origin we can extrapolate forward and appreciate how life itself began. Our meteorite work takes place within the Impacts and Astromaterials Research Centre.

Life detection on Mars

The quest to determine whether life existed, or still exists, on Mars is underway with a number of missions both active and being planned in the next few decades. Yet detection of organic matter on Mars is unlikely to be straightforward. The National Aeronautics and Space Administration Viking I and II missions in 1976 detected no organic compounds above a threshold of a few parts per billion. Subsequent missions have yet to find a single indigenous organic molecule on the Red Planet. New instrument packages are required to search for trace levels of specific organic molecules. Imperial is part of efforts to develop instruments and techniques for life detection on Mars. The challenge of designing activities and producing equipment to firm deadlines inspires scientific endeavour. Preparing for missions to Mars is expected to be a scientifically fruitful adventure. Advances made during the lead up to space missions have numerous terrestrial applications and the spin-off benefits from space mission research and development are legendary.

Unconventional hydrocarbons

Utilizable energy resources are essential to the global economy. Conventional crude oil is a staple energy resource and accounts for over 35% of the world’s energy consumption. Recently the demand for oil is focusing scientific attention on unconventional hydrocarbon deposits. Imperial College Organic Geochemistry activities involve research into both conventional and unconventional petroleum deposits. Unique approaches are provided by endeavours associated with space missions. Elegant solutions are effectively transferred between scientific fields and can help to meet society’s demand for energy.

Mass extinctions

Layers of rocks contain a chemical testimony of environmental change through time.These changes are most dramatic during events known as mass extinctions where substantial percentages of species disappear. The big five mass extinctions are the end Ordovician, Late Devonian, end Permian, end Triassic, and end Cretaceous. At times of mass extinctions rock chemistries tellingly display distinct perturbations. Specifically, the organic remains of the organisms that lived and died during the events are entombed in rocks and can be extracted and analysed using organic geochemical methods. Interpreting these molecular fossils allows us to reconstruct the environments in which these organisms prevailed and thereby understand the causes and consequences of the extinction events. The biggest of the mass extinctions occurred at the end of the Permian. Understanding the end Permian catastrophe helps us to put the current human disturbance of our environment in geological context. Our extinction work has been summarised by the National Geographic MagazineI,Science and the BBC.

Organic proxies of environmental change

Organisms are biochemically adapted to their environment. By examining the nature of organic matter through time a record of changing environments can be constructed. For instance plant spores contain pigments that protect their genetic cargo from mutation by UV light. By tracking the pigment contents of spores collected over hundreds of years trends in the amount of UV penetrating to the Earth’s surface can be established. Other environmental records are contained in rock matrices deposited in layers at regular intervals. Examining these layers and studying the diagnostic molecules present allows the generation of data that can reflect changing environmental conditions.

Forensic science

The type of carbon in the body’s molecules is present as two stable isotopes (carbon-13 and carbon-12). The ratio of these stable isotopes reflects the carbon ing ested as part of any diet. Drugs manufactured in the lab contain ver y different ratios, allowing the two sources of molecules to be distinguished by scientific instruments. For drug cheats in athletics, you are what you eat plus a little bit of what you might inject. Conventional techniques, however, struggle to analyse molecules such as steroids in their natural form. We develop new approaches that delicately strip molecules of their analytically troublesome parts preparing them for carbon isotope analysis. Producing easy-to-handle molecules without destroying their carbon source signal opens up the whole of the body’s molecules to intense scientific scrutiny. A description of our forensic research is available in a recently published review. The work has appeared in a news article in The Times.

Research Staff

Watson,JS

Montgomery,WB

Court,RW

Research Student Supervision

Zafar,R, Organic-inorganic interactions at mineral-water interfaces

Zenteno,D, Meteorites and their gases

Luong,D, ExoMars and Beyond: A lab-based Mars mission

Mustafa,K, Shale gas in Poland

Gordon,PR, A new organic survey instrument for Mars

Sarney,A, Petrographic assessment of gas host sites in shales

Wright,MC, Stable isotope ratio indicators of gas adsorption and release mechanisms

Lewis,JM, Investigating abiotic gases on Earth and Mars