Energy and Materials for the Start of Life
“There is another way. It’s heresy.”
With the proliferation of extrasolar planet discoveries in recent years, increasing attention has been focused on how these systems came to be. Alan Boss, formation theorist at DTM, looked at the conventional beliefs on the topic and described his own theories with his talk, “Building the Solar System.” The generally accepted model for giant planet formation is core accretion, in which comet-size particles “bang” together, eventually accreting into planetary cores. This model is very slow, so slow that it takes longer to grow a core than the lifetime of the nebular gas from which our solar system and giant planet atmospheres formed. To deal with this wrinkle and others, Boss described his disk instability model. It requires only about 1,000 years for the beginning of core formation—plenty of time for the gas to remain and be assimilated into atmospheres. Boss discussed the physics involved: small instabilities in the disk cause the gas and dust to break up, forming first spiral arms and then clumps, which could then turn into planets. He also explained how the gravitational effects from a newly formed Jupiter and Saturn could have sped up the formation of the terrestrial planets. Finally, he mentioned that the UV radiation process in the protoplanetary disk could have yielded the prebiotic chemistry leading to later life.
Nature's Catalysts (from upper left to lower right: Pyrite FeS2, Sphalerite ZnS, Chalco-Pyrite CuFeS2).
George Cody described his work suggesting that base metals could have provided the catalyst needed in the emergence of life.
(Courtesy George Cody.)
“I drew the short straw, so I have to talk about the origin of life.”
George Cody of the
Geophysical Lab described the work he has been doing on the emergence of
protometabolism, before the advent of RNA. For life as we know it to emerge
there has to be a viable route for elements such as carbon, nitrogen, and
phosphorus to be metabolized by organisms. His presentation, “Carbon,
Minerals, and the Origins of Life,” began with a summary of when and
where life arose on Earth. The oldest known crystal contains evidence that
the planet was hospitable to life as early as 4.4 billion years ago. Other
evidence suggests that hyperthermophilic organisms, such as those that live
in high-temperature conditions at deep-sea vents, could have been the earliest
life forms. Cody explained that for such creatures to arise, an emergence
from a world of chemistry to one of biology would have had to take place
and some kind of catalyst would have been required to promote sophisticated
carbon and nitrogen fixation. His research in mineral catalysis under deep-sea
conditions has shown that base metals, such as iron, nickel, and cobalt,
which would have been readily available in the deep-sea environment, could
have provided the catalyst needed in a protometabolism. He ended his talk
with a caution that complex organic chemistry doesn’t necessarily equal
life. 
Andrew Steele discussed Martian meteorites, such as ALH84001, and how they are being analyzed to determine the source of their organics.
(Courtesy Andrew Steele.)
Martians, Martians everywhere, or are they?
Andrew Steele,
the newest Staff Member at GL, gave a lesson on detecting extraterrestrial
life and recognizing frauds. His talk, “How to Spot a Martian,”
explored techniques that have been used to search for life on Martian
meteorites, described their results, and predicted what the future holds
in this area. Steele showed a spectacular array of images that made it
clear that it isn’t just the structure of fossil remains that can
indicate the presence of microbial life. The biochemistry, chemistry,
and context of the samples must be considered too. He pointed out that
meteorites are subject to contamination by organisms on the Earth and
described the five techniques that are used now to unravel what a sample
contains. Of eight meteorites that have been analyzed, terrestrial organisms
and organics have been found on all of them, including one bacterium that
normally lives in the human eyebrow. Steele also discussed technical advances
that are on the horizon, including technology developed for DNA analysis
such as fluorescent probes and protein chips. He ended his talk by saying
that meteorites will continue to be important sources of information,
but that robotic missions to various celestial bodies and manned missions
to Mars would significantly advance the search.
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(Courtesy Arthur Grossman.)
“Let there be light.”
Maybe God
created life and the creationists are right, said Arthur Grossman of Plant
Biology as he introduced his talk, “The Diverse Responses of Photosynthetic
Organisms to Light.” As the audience blanched, he pointed out the
simplicity and paradoxical nature of the entire seven-day affair and then
eased into the serious part of the presentation. Grossman described the
dual nature of light—its particle and wave properties—and then
talked about its biological duality with respect to photosynthetic organisms.
Plants need light for photosynthesis and carbon fixation, but too much
can lead to death as a result of photo-oxidative processes. How then do
plants regulate their light intake? Grossman described research on light
energy use in cyanobacteria, green algae, and vascular plants. He presented
some fascinating images from experiments that demonstrate how cyanobacteria
move to and from light to regulate their light intake, and how they can
optimize the light-collection machinery relative to the wavelengths of
light in the environment. He also showed how plants can bend toward light
under low light conditions and change leaf orientation and chloroplast
position within cells under high light intensity to minimize light absorbance.
But despite these strategies, plants may still absorb dangerous amounts
of light energy. Grossman talked about how excess absorbed light energy
can be efficiently dissipated as heat through a process that occurs within
the light-harvesting structures themselves. He concluded by saying that
specific photoreceptors and intracellular redox conditions supply the
signals that allow photosynthetic organisms to acclimate to different
light environments, and that morphological, physiological, biochemical,
and biosynthetic changes must work in concert to cope with light’s
dual nature.