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Origin & Evolution of Life: March 2012


A workshop to be held at the Space Telescope Science Institute in Baltimore MD, April 9-10, 2012.

The problem of the faint early Sun has been around for many years, and it boils down to this: We presume that the Sun started its life on the zero-age main sequence (ZAMS) with essentially the same mass that it has today, given the low flux of the solar wind, and we presume that our understanding of the physics of the Sun at that stage is reasonably good. Evolutionary models of the ZAMS Sun then predict that it had about 70% of its current luminosity.

That low luminosity is a problem when combined with what we know about the early atmosphere of the Earth because if the Earth's surface were to become covered in ice then the albedo would be high enough to prevent the young planet from recovering. The usual way out of this dead-end is to provide the early Earth with a reducing atmosphere that leads to a strong greenhouse effect, keeping the surface fairly toasty, or at least non-frozen.

We know the early Earth had liquid water on its surface, and we know that the young Mars did as well. Of course both planets may have had greenhouse atmospheres, but perhaps our understanding of the ZAMS Sun is incomplete.

The purpose of this workshop is to bring together scientists from a number of disciplines to discuss the state of knowledge of the young Sun and the young solar system. We will involve leading experts from geochemistry, geophysics, planetary science, solar physics, and stellar astronomy. Among the questions to be addressed are:

* How much do we know of the early Earth's atmosphere and the planet's surface?
* Was there a reducing atmosphere sufficient to produce a greenhouse effect?
* How much glaciation occurred at those early epochs?
* What other effects related to the Earth itself can account for liquid water?
* What limits can we set on the state at different times of the atmosphere and surface of early Mars?
* What limits on the state of the ZAMS Sun can be set from observing stars, from the solar system, and from the Sun itself?

Registration and abstract deadline: March 15, 2012
Registration fee: $100 until March 15, $150 after.

For more information: http://www.stsci.edu/institute/conference/faint-sun

A team of researchers from NAI's Montana State University Team has proposed a new path in the evolution of biological nitrogen fixation on Earth. Nitrogen is one of the most important elements for life on Earth, and astrobiologists have long been interested in its role in the history and evolution of life.

Nitrogen is abundant on our planet as an atmospheric gas. However, in order for Nitrogen to be accessible for life, it must be converted into other chemical forms. A key step in the global cycling of nitrogen is biological nitrogen fixation, which is accomplished via a protein known as 'nitrogenase.' Three forms of nitrogenase are known - all similar, but containing slightly different metallic complexes. Previously, scientists thought the most common nitrogenase found today (which contains the element molybdenum (Mo)) appeared later in life's evolution that the two lesser-found forms (containing vanadium (V) or iron(Fe)). The new study has revealed an evolutionary path that places Mo-dependent nitrogenase earlier than the V and Fe forms. The study is changing views of how this important biological pathway evolved through time - shedding light on the early history of life on Earth.

The study was published in the journal Frontiers in Microbiology under lead author Eric S. Boyd. The research was carried out as part of the NAI project "Evolution of Nitrogen Fixation, Photosynthesis, Hydrogen Metabolism, and Methanogenesis."

RNA Origins in Sheets of Clay

An example of the mineral montmorillonite (Pen for scale). This sample comes from the mineral collection of Brigham Young University Department of Geology, Provo, Utah. Photograph by Andrew Silver.

One popular hypothesis for the origin of life suggests that the nucleic acid, RNA, performed two important roles: RNA stored genetic information and also catalyzed the chemical reactions that helped get life started. A hurdle in this route to life is that we don't know how the first RNA molecules themselves were formed. A new study supported by the NASA Astrobiology Institute and led by James Ferris of NAI's New York Center for Astrobiology at Rensselaer Polytechnic Institute Team may further our understanding of the 'RNA world' hypothesis.

RNA molecules are built from smaller pieces (a.k.a. monomers). When pieced together to form RNA, these monomers must be 'activated' - in other words, they need to be switched 'on' and chemically ready to react with other molecules. This produces a strand of RNA that could be useful in the RNA world scenario.

A new study is shedding light on this step in the process. The research focuses on montmorillonite - a group of soft minerals that are usually found in the form of clay and occur naturally on Earth. Previous work has shown that activated nucleic acids can be formed when montmorillonite minerals are present to catalyze the reaction. However, not all montmorillonites are catalytic - and the new research is helping us understand why. The extent of catalysis depends on the magnitude of the negative charge between layers of montmorillonite minerals, the number of negatively charged ions that produce this charge, and also the pH at which the reaction occurs.

The study also reveals new characteristics of the RNA molecules formed by montmorillonite catalysis, and is beginning to unravel the mechanism by which montmorillonite helps RNA form.

Scientists are not sure if montmorillonite or nucleic acids were present on the early Earth, but it is possible. Additionally, the recent discovery of montmorillonite on Mars raises questions about whether or not a similar process could have occurred on the red planet.

The study, "The role of montmorillonite in its catalysis of RNA synthesis" was published in the journal Applied Clay Science under lead author Michael F. Aldersley and coauthors Prakash Joshi, Jonathan Price and James Ferris.

The NAI Origin of Life Focus Group will host monthly online seminars featuring talks by one established researcher and one early career researcher on topics that are both central to the origin of life and interesting to the broader scientific community. Please join us for this inaugural seminar and spread the word to your friends and colleagues.

Date/Time: Tuesday, March 6th, at 11-12:30pm Pacific Time

Featuring two presentations:

Steven Benner (Foundation for Applied Molecular Evolution, Distinguished Fellow) "Understanding the Chemistry Behind Origins"

Sara Imari Walker (Beyond Center @ Arizona State University, NASA Astrobiology Program Postdoctoral Fellow)

"Not Understanding the Physics of Origins"

Participation Instructions

The slides and audio/video for this meeting will be presented using Adobe Connect. To join the meeting, connect to: http://connect.arc.nasa.gov/oolseminar/