Exploration

How do planets sustain life? We explore this question by examining the evolution of Earth as an inhabited world, and the habitability of worlds beyond our own.

Fundamental Investigations into How Planets Sustain Life

How do planets sustain life? We explore this question by examining the evolution of Earth as an inhabited world, and the habitability of worlds beyond our own.

Ongoing Efforts

O2 in Earth’s Atmosphere and Oceans
Shark Bay, Western Australia. Ancestors of the stromatolites at Shark Bay caused the rise of O2 in Earth’s atmosphere.

In Shark Bay, Western Australia, ancestors of the stromatolites caused the rise of O2 in Earth’s atmosphere.

Until about halfway through its history, Earth’s atmosphere was devoid of O2. The transition to a modern, O2-rich atmosphere – beginning with the so-called “Great Oxidation Event” that occurred ~ 2.4 billion years ago – was one of the most profound transitions the planet has undergone. While it was caused by life and paved the way for life like ours, we do not understand why it happened when it happened. Nor do we fully understand the causes and consequences of later variations in ocean and atmosphere O2.

In our research, we: seek evidence of the earliest “whiffs” of O2 to learn when photosynthesis began to pump O2 into the environment; examine the interactions between biological production and geological consumption of O2; and develop new “redox proxy” methods to examine changes in O2 in the environment through time.

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Life on Other Worlds

Ultimately, the best way to advance our understanding of how planets sustain life is to search for life beyond Earth, be it on other planets or moons in the Solar System or on “exoplanets” that are being rapidly discovered orbiting other stars. Whether life is ubiquitous or rare, this search teaches us what makes a planet habitable. It will also provide powerful information about the probability of the origin of life, which is one of the most profound open questions in all of science.

Cassini completes first Enceladus flyby.

Cassini completes first Enceladus flyby.

Our efforts to understand O2 in Earth’s atmosphere, described above, are directly relevant because  the search for life on exoplanets centers on the search for O2, which could constitute a biosignature. Our other work in this area includes: exploration of concepts to search for extant and extinct life on Mars; and development of a mission to return samples from Saturn’s moon, Enceladus, which may be the most accessible extraterrestrial habitable environment in the Solar System.

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Elements and Evolution
RNA

RNA – Ribonucleic Acid

Living things are made up of a distinct subset of chemical elements from the Periodic Table. These include C, H, O, N, P, and S – the major elements in DNA, RNA, proteins, and cellular structures – as well as a host of trace elements, such as Fe, Cu, Zn, and Mo, that are important enzyme cofactors. The abundances of many of these elements in the oceans and at Earth’s surface change with time, in large part as a consequence of changes in O2. The abundances may also differ on other Earth-like planets, as a consequence of variations in element abundances among the stars.

We are interested in the complex relationships between the chemical requirements of life and these variations in environmental abundances, leading us to: examine the “plasticity” of life’s use of particular elements; determine the compositions of organisms in extreme environments; assess the effects of environmental element variations on biological evolution in Earth’s past; and consider the consequences for life on other planets.

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