Research

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. The organic geochemistry group 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.

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.

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. Recognising signals of habitability or habitation in the plumes and atmospheres of icy moons requires preparation on Earth. Life detection techniques must be adapted to deal with the specific and challenging conditions of the outer solar system.

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.

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.

RADIATION

Radiation has significant effects on organic matter. The radioelements uranium and thorium are found in sediments and can cause the polymerisation of hydrocarbons and their preservation over millions of years. Radiation generated organic residues can be recognised and interpreted using mass spectrometry and spectroscopy. The study of radiation-induced laboratory organic materials and geological residues can help to predicting changes in cometary organic matter and their potential remnants captured between lava layers on the Moon.

SPACE SPIN-OFFS

Preparing for space missions to planets and moons in our solar system is 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.

MASS EXTINCTIONS, THE CARBON CYCLE AND CLIMATE CHANGE

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.

ORGANIC PROXIES OF ENVIRONMENTAL CONDITIONS

Organisms are biochemically adapted to their environment. By examining the nature of organic matter a record of environmental conditions can be recognised. The remains of life can also be subjected to secondary processing that generates an environmental signature. Examples include plant spores that contain pigments to protect against UV light to act as proxies for location and atmospheric change, molecular ratios that are sensitive to soil acidity brought about by large scale volcanism, organic compounds that are sensitive to pressure and may act as paleobarometers, biological organic compositions that reflect life's remains subjected to hydrothermal processes, and molecular patterns that are characteristic of present-day pollution sources. Environmental records can be found in our present-day environments or rock layers deposited in the past.