David Summers

David Summers
Senior Research Scientist

Dave Summers investigates a wide range of chemical reactions that are either needed for life to begin, that may affect whether life can exist, or that might be used by scientists to recognize life elsewhere. For example he is looking at the reactions of nitrogen in the atmosphere of ancient Mars. Where did it go? Could it have provided nitrogen for the start of life on Mars?

It may be that vesicles, water filled “soap bubbles” that look something like cells, may have been important in the origin of life. Dave is looking at what reactions may occur inside these vesicles, and how they may related to things like the start of photosynthesis.

Life shows a preference for using the lighter isotope of carbon – carbon-12 – rather than the slightly heavier carbon-13 when it makes stuff out of carbon dioxide. Can we use this as a test for whether compounds were made by life? Or might inorganic reactions do the same thing? Dave is doing the hard work of examining how this same preference for lighter carbon might also be exhibited by completely inorganic reactions. By understanding how this can happen, he may keep future space missions from stumbling over a false claim of extraterrestrial biology. He is also interested in how we can test for such compounds as proteins or fatty acids to detect life, both in the lab and robotic missions. Dave doesn’t just assume we’ll just “know life when we see it.” He wants a better test than that.

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We propose a feasibility study for a small spaceborne mid-Infrared telescope/spectrometer designed to detect and characterize the delivery and survival of extraterrestrial organic matter to the atmosphere (and hence to the Earth). This instrument would detect the dilute levels of organics present in the upper atmosphere by using astronomical mid-infrared light sources along a viewing path that grazes the Earth atmosphere at an altitude of 80 to 100 km (where meteoritic debris is known to accumulate). This would provide a very long path length and allow, for the first time, the detection and characterization of the material that meteors are delivering by the detection of the mid-IR absorbances in the molecular bands. This would provide the first measurement of the amounts of delivery and the types of compounds being delivered and allow characterization of the amounts/types of prebiotic molecules that would become available for the origin of life. It would also provide a better understanding of the organics being formed in solar nebula.

Lipids and the Origin and Evolution of Life

This work will support experiments designed to better understand the how lipids relate to the origin of life. It looks at events leading up to the origin of life (prebiotic chemistry) and at the subsequent evolution of life after the last common ancestor, LUCA (and hence, at how one might extrapolate back from current life toward the LUCA). This coop will include work on the formation of amphiphilic vesicles and the role they may have played in supporting and containing chemistry and the origin of life. It also includes studying the use of lipids in microorganisms and how such usage evolved and how that information can be linked to the study of biogeochemical analysis of samples containing lipids as biosignatures.

Microbial Contamination Detection at Very Low Levels by [125] I Radiolabeling

The goal of this projects is to develop a new and more sensitive method for the determination of bioburdens for planetary protection purposes.