The sustainability of habitability on terrestrial planets: Insights, questions, and needed measurements from Mars for understanding the evolution of Earth-like worlds

What allows a planet to be both within a potentially habitable zone and sustain habitability over long geologic time? With the advent of exoplanetary astronomy and the ongoing discovery of terrestrial-type planets around other stars, our own solar system becomes a key testing ground for ideas about what factors control planetary evolution. Mars provides the solar system's longest record of the interplay of the physical and chemical processes relevant to habitability on an accessible rocky planet with an atmosphere and hydrosphere. Here we review current understanding and update the timeline of key processes in early Mars history. We then draw on knowledge of exoplanets and the other solar system terrestrial planets to identify six broad questions of high importance to the development and sustaining of habitability (unprioritized): (1) Is small planetary size fatal? (2) How do magnetic fields influence atmospheric evolution? (3) To what extent does starting composition dictate subsequent evolution, including redox processes and the availability of water and organics? (4) Does early impact bombardment have a net deleterious or beneficial influence? (5) How do planetary climates respond to stellar evolution, e.g., sustaining early liquid water in spite of a faint young Sun? (6) How important are the timescales of climate forcing and their dynamical drivers? Finally, we suggest crucial types of Mars measurements (unprioritized) to address these questions: (1) in situ petrology at multiple units/sites; (2) continued quantification of volatile reservoirs and new isotopic measurements of H, C, N, O, S, Cl, and noble gases in rocks that sample multiple stratigraphic sections; (3) radiometric age dating of units in stratigraphic sections and from key volcanic and impact units; (4) higher-resolution measurements of heat flux, subsurface structure, and magnetic field anomalies coupled with absolute age dating. Understanding the evolution of early Mars will feed forward to understanding the factors driving the divergent evolutionary paths of the Earth, Venus, and thousands of small rocky extrasolar planets yet to be discovered

Fire hazards of exterior wall assemblies containing combustible components

The Fire Protection Research Foundation has funded a research project on “fire hazards of exterior wall assemblies containing combustible composites”. This paper presents preliminary findings from the project. In particular, statistics relating to exterior wall fires have been reviewed. Exterior wall fires appear to account for somewhere between 1.3% and 3% of structure fires in the selected property types investigated. Fires involving combustible exterior wall assemblies are low frequency events however the resulting consequences in terms of extent of fire spread and injuries and fatalities can be large as demonstrated by selected fire incident case studies. An overview of this project and it's further work is provided

Fire hazards of exterior wall assemblies containing combustible components

The Fire Protection Research Foundation has funded a research project on “fire hazards of exterior wall assemblies containing combustible composites”. This paper presents preliminary findings from the project. In particular, statistics relating to exterior wall fires have been reviewed. Exterior wall fires appear to account for somewhere between 1.3% and 3% of structure fires in the selected property types investigated. Fires involving combustible exterior wall assemblies are low frequency events however the resulting consequences in terms of extent of fire spread and injuries and fatalities can be large as demonstrated by selected fire incident case studies. An overview of this project and it's further work is provided

Characterization of the larval hemolymph proteome.

<p>(A) Workflow of the analyses. Hemolymph samples from fed and starved larvae were digested in solution. Tryptic peptides were separated by isoelectric focusing for complexity reduction. Peptides were analyzed using microcapillary liquid chromatography–electrospray ionization–tandem MS (µLC-ESI-MS/MS). SEQUEST spectral search was performed for peptide spectrum matching. (B) Venn diagram illustrating the number of gene models detected in hemolymph from fed and starved larvae, respectively.</p

Effects of starvation on hemolymph proteome.

<p>The magnitude versus amplitude (MA) plot shows the log2 fold change of the expression of the identified <i>D. melanogaster</i> proteins in the starved versus fed condition against the mean normalized spectral count. The top 10% differentially expressed proteins are highlighted, including 50 up-regulated proteins (red dots) and 22 down-regulated proteins (green dots). Protein identifiers are shown for selected proteins discussed in the text. Unambiguous protein identifications by class 1a, 1b, and 3a peptides are shown as full circles. Protein groups identified by class 2a or 2b peptides (which unambiguously imply a gene model) are shown as open circles, ambiguous identifications by 3b peptides are shown as open diamonds (the respective identifiers are listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0067208#pone.0067208.s002" target="_blank">Table S2</a>).</p

Starvation-associated protein abundance changes in larval hemolymph.

a)<p>Change in transcript levels during development in rich medium was estimated based on expression profiling data from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0067208#pone.0067208-Burmester2" target="_blank">[77]</a>. For transcript levels around the time when starvation was started (early) the values observed at L2 and L3/12hours were averaged. For transcript levels around the time of hemolymph collection (late) the values at L3/puff stage 1–2 were used. The given values correspond to log2(early/late).</p

Summary of identified spectra, peptides, proteins and estimated FDR levels.

a)<p>According to our peptide classification scheme <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0067208#pone.0067208-Qeli1" target="_blank">[38]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0067208#pone.0067208-Grobei1" target="_blank">[46]</a>, class 1a peptides unambiguously identify a single unique protein sequence encoded by a unique transcript. Class 1b peptides also unambiguously identify a unique protein sequence encoded by several transcripts of the same gene model with identical coding region and differences in the 5′ and/or 3′ untranslated regions. Class 2a peptides identify a subset and class 2b peptides all protein sequences encoded by a gene model. Class 3a peptides unambiguously identify one protein sequence, but this sequence could be encoded by several gene models from distinct loci (e.g. histones). Finally, class 3b peptides can be derived from different protein sequences encoded by several gene models from distinct loci and have the least information content.</p>b)<p>For protein groups identified by class 2a or 2b peptides (a gene model identification) all possible protein accessions are listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0067208#pone.0067208.s001" target="_blank">Table S1</a>.</p>c)<p>The minimal number of additional protein identifications by 3b peptides is shown.</p>d)<p>Based on the total hits in target and decoy databases (DB), the FDR was estimated at the spectra, peptide and protein level.</p

Abundance of larval serum proteins.

<p>Hemolymph was isolated from fed (f) and starved (s) larvae (see Fig. 1). Proteins in samples of 10, 3.3, 1.7 or 1 µl hemolymph were resolved by SDS-PAGE and stained with Coomassie Blue. The position of the major larval serum proteins (LSPs) is indicated by an arrowhead. Position and size (kDa) of molecular weight markers (m) are indicated on the right side.</p