Origin & Evolution of Life: July 2010

Abstract Submission Deadline: August 10, 2010

2010 Geological Society of America National Meeting: T110, Mountain Formation and Landscape Evolution in the Solar System: Implications for the Origin of Life.

Organizers: Joseph Kula, Suzanne L. Baldwin

Session Summary: Terrestrial mountain formation in the solar system is related to thermal decay, tectonics, and impact events. The processes and timescales of landscape evolution will be explored with implications for the origin and search for life.

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A NASA Astrobiology Institute-funded study led by Chris Dupont of the J. Craig Venter Institute indicates that environmental availability of trace elements over Earth's history influenced the selection of elements used by life as biological evolution progressed. Their results show that environmental concentrations of trace metals influenced which types of metal-binding proteins evolved, and the relative timing of their evolution.

The study implies that the geochemistry of the Archean ocean (>2.5 billion years ago) influenced both the evolution of metal-binding protein architectures and the selection of elements by the ancestors of modern Archaea and Bacteria (simple single cell organisms). Specifically, low Zn, Mo, and Cu concentrations in the Archean ocean likely prevented the widespread emergence and diversification of Eukaryotic life (including plants, animals, and fungi) until the oceans became oxic, relatively late in Earth's history. The study also revealed that although modern Archaea and Bacteria still predominantly use ancient metal-binding protein structures, most Eukaryotes use both early- and late- evolving structures. The paper appears in the May 24 Early Edition of PNAS.

Source: NAI Newsletter

Join us for the second in a series of NASA Astrobiology Postdoctoral Program (NPP) seminars!

Date/Time: Monday, July 12th, 11am Pacific Time
Title: "Impact Bombardments on Early Earth and Mars: Implications for Habitability"
Speaker: Oleg Abramov, University of Colorado, Boulder

Abstract: Lunar rocks and impact melts, lunar and asteroidal meteorites, and an ancient martian meteorite record thermal metamorphic events with ages that group around and/or do not exceed 3.9 Gyr. That such a diverse suite of solar system materials share this feature is interpreted to be the result of a post-primary-accretion cataclysmic spike in the number of impacts commonly referred to as the late heavy bombardment (LHB). We report numerical models constructed to probe the degree of thermal metamorphism in the crust in the effort to recreate the effect of the LHB on the Earth and Mars; outputs were used to assess habitable volumes of crust for possible near-surface and subsurface primordial microbial biospheres. Our analysis shows that there is no plausible situation in which the habitable zone was fully sterilized on Earth and Mars, at least since the termination of primary accretion of the planets and the postulated impact origin of the Moon. Our results explain the root location of hyperthermophilic bacteria in the phylogenetic tree for 16S small-subunit ribosomal RNA, and bode well for the persistence of microbial biospheres even on planetary bodies strongly reworked by impacts. In fact, on Mars, the LHB may have been very beneficial for habitability by generating widespread hydrothermal activity, releasing water vapor into atmosphere, and likely temporarily changing global climate to a warmer and wetter state.

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Source: NAI Newsletter