2001 Annual Science Report
University of California, Los Angeles Reporting | JUL 2000 – JUN 2001
Executive Summary — UCLA (dm)
Research at UCLA continues to be 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 planetary environments; and (6) exploration for life in the Solar System. Over the past year, activities of NAI Focus Groups have allowed us to explore several of these themes in conjunction with partners across the Astrobiology community. Mission-oriented achievements include the selection of the Artemis project (David Paige, PI) as one of ten Scout mission concepts. These accomplishments are developed more fully below.
Song, Zuckerman and their colleagues are targeting the youngest and nearest stars in their search for dusty disks and directly observable planets. Telescopic observations of about 300 candidate objects, mostly at Siding Spring Observatory, Australia, have revealed a sizeable group of 10 million year-old southern stars (the b Pictoris moving group) that are near enough to enable advanced coronographic and adaptive optic methods to detect and image cooling giant planets when comparable facilities become available in the southern hemisphere. This result dramatically exceeds expectations of only a year ago. In a parallel study, Jura and Chen recently reported the probable detection of a massive population of asteroids around a nearby star. Looking forward to the first science flights of the SOFIA airborne infrared telescope in 2004, astronomers are beginning to explore astrobiological applications such as the detection and characterization of organics in the interstellar medium and nearby accretion disks.
Geobiology and Geochemistry.
Excitement in geochemistry comes from discoveries, made by Farquhar and his collaborators at UC San Diego, of a record of atmospheric mass-independent isotope effects recorded in modern and ancient sedimentary rocks. Lyons has developed a photochemical model for oxygen isotopes that implicates ozone, rather than peroxide, as the influential molecule and also predicts large D17O anomalies in upper atmosphere nitrates. The recent discovery of nitrate particles in the Earth’s polar stratosphere suggests that this study will have unexpected and important spinoff applications for present-day atmospheric chemistry. In the more complex and less well understood sulfur system, important progress has been made in developing new techniques and standards for multi-collector ion microprobe analysis of 32S, 33S, 34S, and tentatively 36S, in both sulfides and sulfates (Mojzsis, McKeegan, Lyons, Runnegar, and collaborators). Work on 3.5 Ga old samples from Western Australia provides strong support for the Farquhar hypothesis that sulfur cycling during the Archean was greatly influenced by shortwave ultraviolet radiation in an anoxic atmosphere. This research imposes severe constraints on ideas about bacterial sulfur metabolism during early Earth history. Similarly, the discovery of 4.3-4.4 Ga detrital zircons from Western Australia have already led to the inference of an ocean-scale hydrosphere interacting with the crust by that time (Mojzsis, Harrison). The ambitious plan now is to obtain sufficient quantities of these Hadean zircons (10,000?) to investigate significant environmental questions such as the age of the atmosphere (using 136Xe derived from extinct 244Pu) and rates of crustal recycling on the early Earth (Harrison).
Following the pioneering study of ion microprobe measurements of the carbon isotope composition of individual Precambrian microfossils reported last year (House and colleagues), this technique has been used to measure the carbon isotopic compositions of cells targeted by fluorescent in-situ hybridization (FISH) within novel microbial consortia (House, McKeegan, and collaborators). This work led to unexpected collaborations among scientists of the Monterey Bay Aquarium Research Institute, the Woods Hole Oceanographic Institution, and the PennState and UCLA teams. Importantly, it also led to the identification of archeal microorganisms responsible for anaerobic methane oxidation.
Metamorphic terranes on Akilia Island, Greenland, are thought to contain both the oldest sediments and the oldest evidence for biological activity (Mojzsis, Harrison, McKeegan, and collaborators). Since these interpretations depend on strongly contested geologic observations, Manning, Mojszis, Harrison, and colleagues mapped the Akilia outcrop at a scale of 1:250 and confirmed the great antiquity of crucial sample sites. Ion probe depth-profiling of a selected zircon crystal then provided unequivocal evidence for a >3.83 Ga age for both the sedimentary rocks and the organic matter they contain.
Field work in the Bangemall Basin, Western Australia, allowed Gehling, Runnegar, and collaborators to observe and sample numerous horizons of Mesoproterozoic megafossils that are preserved in exactly the same way as the soft-bodied Ediacarans of the terminal Proterozoic. Preliminary work suggests the possibility that these megafossils, previously thought to be eukaryotic algae, may be novel microbial consortia, but the large collection will not be studied in detail until later in 2001. Research continues on understanding early Archean conical stromatolites from Western Australia using the differential calculus of interface physics (Jögi, Runnegar). As realistic simulations in 2+1 dimensions require sizeable grids (> 210 nodes), much time has been devoted to developing codes for massively parallel supercomputers. Some of this work will be done in collaboration with the Spanish Centro de Astrobiología (Pérez-Mercader).
Molecular techniques are increasingly being used to understand early animal evolution. In addition to the massive metazoan genome sequencing effort being proposed by the Evolutionary Genomics Focus Group, Jacobs, Gates, and colleagues used engrailed gene expression in mollusks to suggest that the skeletons of all bilateral animals have a common origin, an idea that bears on the nature of the Cambrian Explosion. Additional work on genes involved in intercellular signaling, as well as neural and sensory development in cnidarian flatworms, is throwing light on the origins of sense organs and, hence, on nervous systems.
Genomics and Evolution.
Fitz-Gibbon and House are extending their whole-genome analyses based on the presence or absence of protein-coding genes as phylogenetic markers. This computationally formidable task has now been extended to include 26 published genomes. They are investigating the effects of lateral gene transfer and the statistical effects of adding partial gene sequences. The latter work has an important bearing on the utility of expressed sequence tags (ESTs) for phylogenetic analysis and it complements collaborative work within the Evolutionary Genomics Focus Group on horizontal gene transfer (Lake, Rivera, Riley). An intermediate target is understanding, at the genomic level, the evolution of the eukaryotic cell (Lake). Complementary research on deeply-branching, free-living, and pathogenic protists is aimed at understanding the evolution of the eukarotic cell in the context of anaerobic and aerobic energy production by means of organelles (Johnson, Roger, Silberman). A large number of new rRNA gene sequences have been obtained and the organisms are now being searched for genes targeted to organelles, including those organelles that may have been lost.
Kyte recently participated in an Antarctic expedition aboard the Polarstern, a research ship operated by the German Alfred Wegener Institute for Polar and Marine Research. Two of the seven weeks of the cruise were devoted to geophysical and geological exploration of an area in the Bellingshausen Sea which is the only known site of an asteroid impact into a deep-ocean basin. At least 15 of the cores recovered contain ejecta from this Tertiary-age impact, and they will be used to understand the processes and environmental effects of an oceanic event of this scale.
Additional insight into large impacts within the habitable zone may come from long numerical integrations of Solar System dynamics (Varadi, Ghil, Runnegar). Integrations involving different conditions point to a chaotic perturbation of the inner Solar System at or near the Cretaceous-Tertiary (K-T) boundary, 65 million years ago. Varadi and colleagues are exploring the possibility, using asteroids as test particles, that this chaotic transition may have nudged the K-T impactor into an Earth-crossing orbit. In a different study, W. Moore has developed a mission-testable, end-member model for heat production within Europa that has important implications for the possibility of maintaining life in Europa’s subsurface ocean.
NASA has selected the Artemis multi-Scout mission as one of ten potential payloads for launch in 2007. The study team is led by UCLA (Paige, PI), and includes as partners TRW and JPL. The plan is to send an orbiter carrying three or more small landers which will be targeted to a wide range of latitudes, including the polar regions. The landers will incorporate miniaturized versions of Mars Polar Lander instruments, with the additional capability of detecting organic compounds, plus a nanorover.
NAI Focus Groups. UCLA team members are active participants in the majority of NAI focus groups (FG). Paige is an active member of the Mars FG; Jacobs, Lake (co-Chair), and Runnegar are deeply involved in the Evolutionary Genomics FG; W. Moore is working closely with the Europa FG; Kyte and Ward are candidate co-Chairs for the proposed Impacts FG; and team members have substantial interests in the AstroMaterials, Mission to Early Earth, and EcoGenomics focus groups.