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Project Progress

RESEARCH at UCLA is now focused on six main themes: (1) extrasolar planetary systems; (2) geobiology and geochemistry of early Earth and Mars; (3) evolution of Earth’s early life; (4) genomic evolution and the tree of life; (5) celestial influences on the terrestrial environment; and (6) exploration for life in the Solar System. Over the past year, some of these themes have grown significantly; the thrust of the last has been seriously compromised by the successive losses of both the Mars Climate Orbiter and the Mars Polar Lander.

Astronomy. Recent technical advances and discoveries have paved the way for an exciting new era in the detection and characterization of extra-Solar stellar systems. UCLA astronomers have been deeply involved in these advances by making observations in the infrared, of the dust, disks, and substellar companions of nearby young stars (Schneider et al., 1999; Wood et al., 1999; Telesco et al., 2000; Weinberger et al., 1999). New techniques include NIRSPEC infrared spectrometer â?? constructed at UCLA â?? at the Keck Observatory in Hawaii; the high-altitude SOFIA observatory which will make observations in the mid- and far infrared; and the adaptive optics (AO) capability the Keck II telescope (Wizinowich et al., 2000). These instruments and the Hubble Space Telescope will be used to observe nearby clusters of young stars such as the TW Hydrae and Tucanae Associations, discovered recently (Webb et al., 1999; Zuckerman and Webb, in press). This work has already led to the detection of a faint object that may prove to be a substellar companion,
1-2 times the mass of Jupiter (Lowrance et al., 1999). If this is confirmed it will be the first extra-Solar planet to have been directly imaged.
Geobiology and Geochemistry. A pioneering ion probe study of the carbon isotopic composition of in situ Precambrian microfossils will be published soon (House et al., in press). Standards are now being developed for an in depth study of Proterozoic acritarchs and other organically-preserved microfossils. In parallel with this work, the nature of the Hadean and early Archean environments is being explored through the use of geochemical tracers such as oxygen isotopes in ancient zircon crystals and the four isotopes of sulfur (32S, 33S, 34S, 36S) Archean and older sulfides and sulfates (see Field Expeditions). In future, this research will attempt to document the evolution of oxygen and sulfur isotopes in open ocean systems through the Archean with a view to obtaining information about atmospheric composition, sea water chemistry, and surface temperatures.

Paleobiology. Research is underway on Early Archean chert samples that are expected to contain microfossils (see Field Expeditions). Conical stromatolites from the same sedimentary sequences have been studied by X-ray computerized tomography in order to test numerical models for stromatolite growth being developed at UCLA. Research on ancient black smoker deposits associated with massive sulfide ores in deep-ocean environments have revealed a wealth of new fossils, including numerous vestimentiferan tube worms (Little and Cann, 1999; Little et al., 1999). Future work will focus on the microbial fossils associated with these Phanerozoic occurrences and a search for similar deposits in deep Precambrian time. Other discoveries in paleobiology include work on the importance of microbial mats in the stabilization of sands and the preservation of Precambrian soft-bodied organisms (Gehling, 1999, 2000), plus the role of trace fossils in the initial stages of the Cambrian Explosion (Jensen et al., 2000).

Genomics and Evolution. Achievements include the publication of a robust tree of life based on the protein-coding genes from a suite of microbial genomes, including yeast (Fitz-Gibbon and House, 1999). This massive analysis demonstrated that lateral gene transfer has not obliterated the phylogenetic signal in genome sequences and it provided strong support for the broad architecture of the rRNA tree. These issues will now be explored in depth by incorporating many additional genomes into the study and by using other methods of comparative sequence analysis. Understanding the degree and effects of lateral gene transfer is a central goal of the UCLA/MBL collaboration within NAI’s Evolutionary Genomics Focus Group.
Continuing inter-team research in microbial genomics and gene expression is discussed elsewhere. UCLA strongly supports the GEOPULSE initiative of the Penn State Astrobiology Research Center and will be contributing substantial resources to the further development of the UCLA component of that partnership. Within the Evolutionary Genomics Focus Group, planned research on early metazoan evolution will deal with the relationships of the most deeply branching metazoan groups â?? sponges, cnidarians, ctenophores â?? and their protistan relatives.
It has long been thought that the most deeply branching living eukaryotes, such as Giardia, lack organelles (mitochondria and chloroplasts) because they never had them. Recent work has shown that many of these amitochondriate protists have nuclear genes that have a mitochondrial origin, and in some cases, a mitochondrial function (e.g., Roger, 1999). At the same time, it has become clear that organelles known as hydrogenosomes may be best explained as mitochondrion-like bodies that have lost all their genes. Both of these ideas need to be tested because they have important implications for understanding the early history of eukaryotes and the way in which the eukaryote genome evolved. This work will be carried out at UCLA and at Dalhousie University using several recently discovered, hydrogenosome-bearing, anaerobic protists that are in culture at UCLA.
Planetary science. Two areas of great interest to Astrobiology are the effects of major impacts on the history of life and the effects of secular changes in Earth’s orbital parameters on climate and the evolution of the biosphere. The first is being investigated through the discovery and characterization of impact deposits in undisturbed sedimentary sequences. For example, thick spherule beds with anomalous iridium and chromium isotope ratios provide evidence for the frequency of devastating impacts in early Archean times (Anbar et al., in press; Shukolyukov et al., in press). In the second case, long numerical integrations of Solar System dynamics are being tested through the stratigraphic record of distinctive climatic events which are reflected in global changes in ocean chemistry. An unexpected outcome of this research has been the discovery of the sensitivity of orbital calculations to the ways in which some components of the system are approximated. As a result, we are rewriting the codes from first principles and plan to test and apply the results of long numerical integrations to problems on both Earth and Mars.

Solar System exploration. The sequential loss of the Mars Climate Orbiter (MCO) and Mars Polar Lander (MPL) has seriously disrupted the UCLA program in Astrobiology. However, the operations facility that was constructed in the Science and Technology Research Building (STRB) for the MPL mission, and the core personnel that ran that facility, are resources that should not be squandered at this stage. We are supporting this endeavor by providing modest bridging funds to allow graduate students who were brought on board to work on data from the MCO and MPL missions to develop new research projects, and to help with a transition to new experiments and missions. Planned work on MOC images of the polar layered deposits will combine image analysis with numerical studies of the eccentricity and obliquity of Mars.