Abstract - The Earth-Moon system has unique chemical and isotopic signatures compared to other planetary bodies; any successful model for the origin of the Earth-Moon system has to satisfy these chemical and isotopic constraints. The Moon is substantially depleted in volatile elements such as potassium compared to the Earth and the bulk solar composition, and it has long been thought to be the result of a catastrophic Moon-forming Giant Impact. Volatile element depleted bodies like the Moon were expected to be enriched in heavy ...

Abstract:

Signatures of sulfur isotope mass-independent fractionations (S-MIF) in Archean sulfate and sulfide minerals have been considered as the most convincing evidence for early anoxic atmosphere, and constrain the atmospheric oxygen level to less than a few ppm until before 2.3 Ga [1] [2]. Despite the critical importance in understanding early evolutionary history of atmospheric oxygen and biosphere, the source reaction(s) and physical mechanism of S-MIF are poorly constrained.  Detailed mechanistic understanding of physical origin of MIF is expected to provide critical...

Abstract - We have recently reported the synthesis of bifacial peptide nucleic acid (bPNA), a peptide that uses triazine heterocycles to interface with polypyrimidines. Triazines readily form from prebiotic reaction conditions, raising the intriguing possibility of their role as informational precursors to the native bases. Bifacial PNA engages two oligo T/U strands simultaneously to form a unique triple stranded structure. Thus, bifacial PNA binding is an associative operation, bringing together non-interacting poly-T/U strands to form a bPNA triplex hybrid. We demonstrate...

Abstract: 

Many environments in space contain very low temperature mixed molecular ices that are exposed to ionizing radiation in the form of cosmic rays and high-energy photons.  While traditional chemistry would not be expected to occur at the temperatures typical of these ices (T < 50 K), ionizing radiation can break bonds in the original molecules in the ices to form highly reactive ions and radicals.  These ions and radicals are subsequently free to react despite the low temperatures of the original ices.  Laboratory experiments, many of them carried out...

Abstract: 

"We have bombarded chiral halocamphor molecules in the gas phase with low-energy (< 1 eV), longitudinally-spin-polarized electrons, and investigated dissociative electron attachment (DEA) reactions:       

e- + HA → H- + A,

where H is a halogen atom (Br or I) and A is the residual camphor fragment.  We observe that for a given target handedness, the total DEA cross section depends on the helicity of the incident electron.  In the case of iodocamphor at the lowest...

The NASA Kepler Mission demonstrated that planets larger than Earth yet smaller than Neptune are a commonplace in the galaxy. Until recently, we knew nothing about their masses and, by inference, their compositions.  I report on what we've learned from the first 3 years of the HARPS-N survey, which aims to understand the transition from rocky planets, composed of rock and iron, to Neptune-like worlds, which have accreted an envelope of primordial H/He gas. I will explain the role of the NASA Transiting Exoplanet Survey Satellite (TESS), scheduled for launch in 2017.

Abstract: 

The next frontier in exoplanet research is discovering, characterizing and understanding small exoplanets (sizes below 4 Earth radii), allowing a detailed comprehension of this region of parameter space where planets like our own Earth reside. Advancements in this area of research will lead to an understanding of the diversity and composition of these planets, estimates of the true occurrence rate of rocky worlds with the potential of accommodating liquid water on their surfaces, and help advance planet formation theories struggling to understand how these planets...

Abstract: Chemical reactions leading to the amplification of enantiomeric excess may have played a part in the processes that lead to the homochirality of the biomolecular building blocks of life on Earth.  The surfaces of inorganic materials that probably predate the formation of complex organic molecules on Earth can serve to concentrate organic species simply by adsorption.  Such surfaces can also serve as sites for amplification of enantiomeric excess among chiral adsorbates. While there are common minerals with chiral bulk structures and, therefore, chiral surfaces...

Abstract: How did molecules on the early Earth assemble into storehouses of
information (RNA) and machinery (proteins) surrounded by a membrane?  The
membrane is the most readily explained component because prebiotic fatty
acids (such as decanoic acid) self-assemble in water into vesicles.
However, bare fatty acid vesicles flocculate in the presence of salt
water.  Major questions in the Origins of Life field have therefore
included how the four bases and the sugar in RNA...

Encounters with the strange and the familiar: searching for Life in the Saturn System” . The Cassini-Huygens mission to Saturn has discovered two places in the Saturn system where life may occur, and they each have very different things to teach us. The small moon Enceladus has jets of material that shoot water, salts, and organics into space, all measured by Cassini. With the indirect detection of a liquid water ocean beneath the surface, Enceladus may well host life and the jets provide a simple mechanism for detecting it. Titan, cold and devoid of liquid water on its surface...

Our goal is to understand how protocells developed signaling mechanisms that allowed them to communicate and coordinate their actions. The capability to respond to signals, move, and assemble into cohesive colonies would have significantly improved the protocells’ survivability and enhanced their functionality. Early protocells lacked complex biochemical machinery and thus, communication was most likely driven by fundamental physical/chemical mechanisms, including diffusion of molecules across the membrane. In this context, it is worth considering the behavior of primitive organisms, such...

Abstract:Primitive cells consisting of a self-replicating nucleic acid genome encapsulated within a self-replicating membrane would have depended upon a rich, complex and variable environment to drive their reproduction. I will describe simple and robust pathways for the coupled growth and division of primitive cell membranes composed of fatty acids and related single-chain amphiphiles. I will also discuss recent progress towards the efficient and accurate chemical replication of RNA. Chemical template-copying generally proceeds best at low...

Abstract - 

Finding just one example of a biosphere beyond the solar system would
not only place real constraints on life's cosmic abundance and
origins, but also allow us to place the Earth in proper context. To do
this we need to search for astronomically visible, surface dominant,
living systems. One step towards this is the process of evaluating the
physical and biological environments of a diversity of rocky worlds to
understand their climatological states. Along the way we need to
better constrain the orbital behavior of observed exoplanetary
...