Overview
Organic matter is a sensitive indicator 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.
MISSIONS TO MARS
The quest to determine whether life existed, or still exists, on Mars is underway with a number of high profile missions both active and planned. When life appeared on the early Earth conditions on early Mars were relatively similar which provides encouragement that life may have also appeared on the red planet. Yet detection of the organic signatures of life on Mars is unlikely to be straightforward. Mars is a harsh planet with an oxidising surface, a thin atmosphere and a high flux of radiation. Imperial is part of efforts to meet the challenges of Mars and help attempts to detect life in situ and to return samples to Earth for more detailed study. Professor Sephton is a Science team member for the NASA Mars 2020 Perseverance Rover mission.
Watch & Read: Mars 2020 Perseverance Rover NASA Overview, ITV News Launch, ESA Team Selection, ESA Blog.
MARS STUDIES ON EARTH
Missions to Mars, although highly rewarding, are expensive and time consuming. Preparing for Mars by studying similar rocks and environments on Earth is a valuable step. These Mars-like sites on Earth are known as Mars analogues. Our investigations of Mars analogues allow us to design the best instruments, develop the most appropriate analytical methods and to recognise the best rocks to sample once operating on Mars. Mars analogues can occur at all scales, from small-scale streams and sediments to large-scale deserts and ice caps.
Watch & Read: Acid Streams VOA News, Sky News, Independent, Chemistry World, BBC Earth.
ASTROBIOLOGY OF ICY MOONS
The icy moons of the outer Solar System present the possibility of subsurface water, habitable conditions, and possibly life. Access to evidence that may reveal the conditions for, and presence of, life on the icy moons can be assisted by plumes that eject material from the subsurface into space. The NASA Europa Clipper mission will attempt to sample the plumes from the icy moon of Jupiter. Recognising signals of habitability or habitation in the plumes and atmospheres of icy moons requires preparation on Earth. Our common life detection techniques must be adapted to deal with the specific and challenging conditions of the outer solar system. Professor Sephton is a Science team member for the NASA Europa Clipper mission which will study Jupiter's icy moon.
Watch & Read: Life Detection How to Detect Life on Icy Moons, Mass Spectra Fingerprints of Icy Moon Bacteria, Hydrothermally Processed Markers of Life.
PLANETARY PROTECTION
Planetary protection involves the prevention of transferring biological organisms to other locations in our solar system or the transport of similar entities to Earth in during sample-return missions. Contamination control involves minimizing the contributions of organic contaminants that may interfere with life-detection missions while contamination knowledge involves the identification and chemical characterisation of any potential organic contamination to assist its recognition should it appear during operations. While planetary protection is a relatively well established area the number of techniques available for organic contamination control and knowledge are less well developed. We investigate new monitoring techniques to protect the accuracy of organic detection methods on space missions.
Watch & Read: Planetary Protection in the Outer Solar System PPOSS Website, Organic Monitoring Methods Astrobiology Paper, ExoMars Rosalind Franklin Rover.
Organic matter in meteorites
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.
Watch & Read: Meteorite methane BBC, Independent. Meteorite Greenhouse Gases BBC, Wall Street Journal, Discover Magazine. Winchcombe meteorite Winchcombe investigations, Winchcombe amino acids and PAH, "Star Tar" in the Winchcombe meteorite.
SPACE SPIN-OFFS
Preparing for space 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. Examples include the transfer of knowledge from meteorites to shale gas and from Mars missions to heavy oil.
Watch & Read: Mars Extraction Methods The Engineer.
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. 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.
Watch & Read: Permian Extinction National Geographic Magazine. Catastrophic Permian Soil Erosion BBC. Permian Acid Rain Smithsonian Magazine, NBC News.
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 ingested as part of any diet. Drugs manufactured in the lab contain very 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.
Watch & Read: Detecting Drug Abuse ACI Paper.