ABSTRACT

Microorganisms have inhabited the Earth for 3.4 billion years of its history, and they are key for the evolution of its major geochemical cycles and the composition of its atmosphere. Planets and moons explored thus far in our solar system harbor extreme environmental conditions where it is more likely to find microorganisms than any other form of life. When searching for habitable exoplanets, one has to consider the boundaries of the habitable zone, in particular at its inner-edge where so-called “desert worlds” might be found, and its evolution over space and time.

We are interested in the microbial ecology of extreme environments on Earth as proxy for extra-terrestrial environments at the dry limits for life. We use a combination of geochemistry, physiology, and molecular methods to determine the biotic and abiotic factors that control microbial colonization and diversity in some of the driest deserts on Earth. We found that under extreme water deficit, rapid thermal fluctuation, and high solar radiation fluxes, soils contain little biomass, but flourishing microbial communities are found inside translucent rocks. Those ecological niches in the Atacama Desert and the Dry Valleys of Antarctica can be considered environmental refuges for life and might provide guidance for where to best search for past or present life.

About the Speaker:

Jocelyne DiRuggiero is a faculty member in the department of Biology at Johns Hopkins University. She obtained her Ph.D. at the University Claude Bernard in Lyon, France, before moving to the United States on a Fulbright Fellowship. She was a faculty at the University of Maryland before moving to Johns Hopkins University (JHU) 6 years ago. She is the co-founder of the Institute for Planets and Life at JHU and the chair of the Astrobiology Lecture Series. Dr. DiRuggiero’s scientific interests are in the areas of extremophiles and their adaptations to environmental stresses, and the ecology of microorganisms inhabiting extreme environments.