Baking the Rover is Not an Option

November 20, 2008 / Posted by: Aaron Gronstal

NASA’s Mars Science Laboratory (MSL) is now being prepared for its 2009 voyage to Mars, where the rover will sniff about for traces of organic material. The mission is designed to accurately “see and taste” the martian environment like never before, and could determine if the building blocks of life are present at the planet’s surface. The problem is that many of the substances MSL is made from can release molecules that might interfere with experiments. Many steps had to be taken during the mission’s design and preparation in order to to address this issue of contamination.

Source: [Astrobiology Magazine]

Astrobiology Curriculum Pilot Kicks-Off Maine STEM Initiative

November 19, 2008 / Posted by: Daniella Scalice

The pilot-test of a NASA Astrobiology Institute (NAI)-supported curriculum entitled Astrobiology: An Integrated Science Approach helped kick-off the State of Maine’s new Science, Technology, Engineering, and Mathematics (STEM) Initiative. This initiative was the subject of a press conference given this week by Maine’s Governor, The Honorable John E. Baldacci.

The curriculum was developed with significant input from the NAI Team at NASA Ames Research Center led by Dave Des Marais, who spoke at the press conference. Much of the team’s research in astrobiology is captured in the curriculum.

Providing ninth grade students an interdisciplinary approach to science, this year-long, integrated curriculum covers the broad range of topics encompassed by astrobiology—cosmic and planetary evolution, the origin and evolution of life on Earth, and the potential for habitable worlds elsewhere in the Universe—within the context of science as inquiry.

This project has been a collaborative effort from the start. The curriculum was developed by TERC, an educational non-profit based in Cambridge, MA, with major support from NSF, and additional funds from NAI. Specialists from the Maine Space Grant Consortium and the University of Maine will evaluate the effectiveness of the curriculum in a sample of ten Maine schools. Co-funded by NAI and Lockheed Martin, the pilot evaluation plan will ask if a reform curriculum such as Astrobiology: An Integrated Science Approach engages students, improves their attitudes towards science in general, and promotes their consideration of STEM careers. The evaluation will compare attitudes and interests of students who have been exposed to the curriculum versus those in non-integrated science courses.

Carbonate Conundrum

November 17, 2008 / Written by: Henry Bortman

NASA’s Phoenix lander mission is now over, and scientists are analyzing the data collected from its various experiments. Phoenix’s discovery of carbonates in the frozen northern soil of Mars indicates the area once could have had liquid water. However, there is no way to tell if the carbonates formed locally, or if they came from somewhere else on the planet and blew in with the wind.

Source: [Astrobiology Magazine]

Seeing a Distant Planet

November 15, 2008 / Posted by: Aaron Gronstal

Astronomers have captured the first visible-light photograph of an extrasolar planet. The planet is about the size of Jupiter, and scientists believe that the system in which it resides could harbor more worlds.

Source: [Astrobiology Magazine]

Nov 16, 2008

hemanth said:

i just hope people will not jump to conclusions .

we still have our own solar system to discover …

Earth's Mineral Evolution

November 14, 2008 / Posted by: Aaron Gronstal

New research shows that minerals on Earth have co-evolved with life. Up to two thirds of known minerals can be linked to biological activity, highlighting the important connection between the biosphere and the geology of Earth.

Source: [Astrobiology Magazine]

A Divining Rod for Mars

November 13, 2008 / Written by: Michael Schirber

Mars may have water underground but exactly where it is located is not known. An instrument on the Mars Science Laboratory will use neutrons to help spy for the water.

Source: [Astrobiology Magazine]

Life's Boiling Point

November 12, 2008 / Written by: Michael Schirber

Some proteins can work above the boiling point of water, but these vital biomolecules may have a harder time evolving at high temperature. A new project is searching for the maximum temperature for protein-based life.

Source: [Astrobiology Magazine]

Nov 13, 2008

Nikola said:

Most of these proteins are isolated from achaea bacteria (the so called extremophiles). They are very interesting group of bacteria with specific and unique metabolic characteristics.

Evidence for a New Root of the Tree of Life

November 10, 2008 / Written by: James A. Lake

A new root of the tree of life is providing evidence for a last common ancestor that is very different from the traditional one. This root provides a new perspective on the habitats of early life, including the evolution of methanogenesis, membranes, and thermophily; and the speciation of major prokaryotic taxa.

Using indels, insertions and deletions, within paralogous genes our laboratory has obtained evidence for a new root to the tree of life in a series of recent papers (Lake et al., 2007; Servin et al., 2008; Skophammer et al., 2006; Skophammer et al., 2007). Through the analysis of indels present in 17 genes and their paralogous outgroups involved in diverse functions, including protein synthesis, DNA synthesis, heat shock responses, and nucleotide and amino acid synthesis, the root has been localized to a eubacterial branch of the tree between the clade consisting of the Actinobacteria and the double membrane (Gram negative) prokaryotes and the clade consisting of the Archaea and the Firmicutes.

Since these results, summarized in the figure, exclude the root from the archaeal- firmicute-clade, methanogenesis is excluded as a primitive prokaryotic metabolism. Mapping the phylogenetic distributions of genes involved in peptidoglycan- and lipid-synthesis onto this rooted tree implies that the ether archaeal lipids are not primitive, and that the ancestral prokaryotic population consisted of organisms enclosed by a single, ester-linked lipid membrane, covered by a peptidoglycan layer. These results explain the similarities previously noted by others between the pathways of lipid synthesis in Bacteria and Archaea (Boucher et al., 2004). Our results also imply that the last common ancestor was not hyperthermophilic, although moderate thermophily cannot be excluded, consistent with the results of others (Galtier et al., 1999; Miller and Lazcano, 1995; Philippe and Forterre, 1999).

Figure. The root of the prokaryotic/eukaryotic ring of life. Included are the double-membrane eubacteria (D), the Firmicutes (F), the Actinobacteria (A), the Archaea (R) and the eukaryotes (K). The regions from which the root is excluded are circled. They are labeled with the name of the relevant indel that excludes them and corresponds to the double-membrane prokaryotes (Lake et al. 2007), the Archaebacteria, and the Eukaryotes (Skophammer et al. 2006), the combined clade of the Firmicutes plus the Archaebacteria, (Skophammer et al. 2007), and the Actinobacteria, (Servin et al. 2008).

Publications

Boucher, Y., M. Kamekura, and W. Doolittle. 2004. Origins and evolution of isoprenoid lipid biosynthesis in archaea. Molecular Microbiology 52:515-527.

Galtier, N., N. Tourasse, and M. Gouy. 1999. A nonhyperthermophilic common ancestor to extant life forms. Science 283:220-221.

Lake, J. A., C. W. Herbold, M. C. Rivera, J. A. Servin, and R. G. Skophammer. 2007. Rooting the Tree of Life using Non-ubiquitous Genes. Mol. Biol. Evol. 24:130-136.

Miller, S. L., and A. Lazcano. 1995. The origin of life — did it occur at high temperatures? Journal of Molecular Evolution 41:689-692.

Philippe, H., and P. Forterre. 1999. The rooting of the universal tree of life is not reliable. Journal of Molecular Evolution 49:509-523.

Servin, J. A., C. W. Herbold, R. G. Skophammer, and J. A. Lake. 2008. Evidence excluding the root of the tree of life from the Actinobacteria. Mol. Biol. Evol. 25:1-4.

Skophammer, R. G., C. W. Herbold, M. Rivera, J. A. Servin, and J. A. Lake. 2006. Evidence that the root of the tree of life is not within the Archaea. Mol. Biol. Evol. 23:1648-1651.

Skophammer, R. G., J. A. Servin, C. W. Herbold, and J. A. Lake. 2007. Evidence for a Gram positive, Eubacterial Root of the Tree of Life. Mol. Biol. Evol. 24:1761-1768.

Definitions

Indels – deletions or insertions of amino acids in a protein sequence.

paralogous genes – if a gene in an organism is duplicated to occupy two different positions in the same genome, then the two copies are paralogous.

Outgroup – if three or more groups of organisms are compared, and all but one of them are more closely related to each other than any single one of them is to the last, the latter group is known as the outgroup. The evolutionary conclusion from this is that the outgroup branched from the parent group before the other two groups branched from each other.

Clade – a taxonomic group comprising a single common ancestor and all the descendants of that ancestor.
Actinobacteria – a group of Gram-positive bacteria with high G+C ratio.

Firmicutes – a division of bacteria, most of which have Gram-positive cell wall structure. It includes bacilli, clostridia and mollicutes.

peptidoglycan – a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of Bacteria.

On the Origins of Biological Homochirality

November 10, 2008 / Written by: Sandra Pizzarello

Carbonaceous chondrites meteorites contain abundant organic material with structures as diverse as kerogen-like macromolecules and simpler soluble compounds ranging from polar amino acids and polyols to nonpolar hydrocarbons. Some of these compounds have identical counterparts in the terrestrial biosphere and it has been proposed that their exogenous delivery by meteorite and comet might have seeded the early Earth with biomolecule precursors prior to the onset of life.

One central problem in experimental prebiotic chemistry has been that synthetic processes relevant to molecular evolution, such as the formose reaction, result in complex mixture of compounds. In view of this, to explain the origin of chemically homogeneous polymers as RNA remains a daunting problem. The chemistry of meteorites, seemingly also a result of abiotic random processes, represent a significant exception in that some of its chiral amino acids show enantiomeric excesses of the same configuration as protein amino acids. Recent analyses of pristine Antarctic meteorites suggest that aldehydes may have carried such asymmetry during parent body reactions as well.

Because chiral homogeneity, which is essential to extant life, was probably an attribute necessary to the origin and/or development of life and meteoritic amino acids represents the only natural example of molecular asymmetry measured so far outside the biosphere, it appears reasonable to propose that such chiral trait may constitute a link between abiotic and prebiotic chemistry.

Experiments involving non-racemic amino acids of the type found in meteorites have shown that these compounds could have been suited to aid molecular evolution. For example, they can act as asymmetric catalysts and transfer their asymmetry to other prebiotic building blocks such as sugars. Also, small peptides of three to four residues of these amino acids readily form 3 ₁₀ helixes, which are themselves chiral and may be capable of a selective amplification of enantiomeric excesses upon further uptake of amino acids. In addition, non-racemic meteoritic amino acids lack an α-H and do not racemize in water, i.e., could have preserved their asymmetry through aqueous environments in early molecular evolution and avoided what Bada and Miller referred to as the “catastrophe of racemization” for racemizable protein amino acids.

About the Author

Sandra Pizzarello was born in Venice (Italy) in 1933 and studied in nearby Padua, where she obtained a Doctorate in Biological Sciences. After a brief fellowship, she “stayed home” to raise a family of four children and it took fifteen years. She moved to the US with this group and joined the Chemistry and Biochemistry Department of Arizona State University in 1977, where she still is Research Professor and Professor Emeritus. Her research has been devoted to the study of the organic material in carbonaceous chondrite meteorites, with emphasis on the molecular, isotopic, and chiral characterization of their soluble compounds. More recently, she has focused on the study of the non-racemic amino acids of meteorites, with compound specific isotopic analyses as well as model syntheses that would mimic their prebiotic catalytic activity and reactions. At the last ISSOL meeting in Florence, Sandra delivered the John Oro Lecture and was awarded Silver Medal of ISSOL.

Titan's Triple Threat

The Cassini-Huygens mission has given us our best view yet of Titan, but this moon of Saturn still remains shrouded in mystery. A proposed future mission takes a three-tiered approach – using an orbiting spacecraft, a surface probe, and a hot air balloon — to further explore the enigmatic moon.

Source: [Astrobiology Magazine]