From Gondwanaland, with love : the tale of how Boston got its rocks

Thesis (S.M. in Science Writing)--Massachusetts Institute of Technology, Dept. of Humanities, Graduate Program in Science Writing, 2006.Includes bibliographical references (leaves 26-27).The rocks on which the city of Boston was built did not form as part of North America. They formed about 600 million years ago, at the South Pole, as the northern coast of a supercontinent called Gondwanaland. Boston's journey from the South Pole to its current location traces the world's geologic history over that period of time, including the emergence of animal life as we know it, the formation and destruction of Pangaea, and the rise and fall of the dinosaurs. More than that, though: the history of our understanding of Boston's journey illustrates how geologists think about their world, and how their ideas have changed over the last 150 years in one of science's great revolutions.by Selby Cull.S.M.in Science Writin

The Water Cycle at the Phoenix Landing Site, Mars

The water cycle is critically important to understanding Mars system science, especially interactions between water and surface minerals or possible biological systems. In this thesis, the water cycle is examined at the Mars Phoenix landing site: 68.2N, 125.70W), using data from the Compact Reconnaissance Imaging Spectrometer for Mars: CRISM), High-Resolution Imaging Science Experiment: HiRISE), the Phoenix Lander Surface Stereo Imager: SSI), and employing non-linear spectral mixing models. The landing site is covered for part of the year by the seasonal ice cap, a layer of CO2 and H2O ice that is deposited in mid-fall and sublimates in mid-spring. During the mid-summer, H2O ice is deposited on the surface at the Phoenix landing site. CO2 ice forms at the site during fall. The onset date of seasonal ices varies annually, perhaps due to variable levels of atmospheric dust. During fall and winter, the CO2 ice layer thickens and sinters into a slab of ice, ~30 cm thick. After the spring equinox, the CO2 slab breaks into smaller grains as it sublimates. Long before all of the CO2 ice is gone, H2O ice dominates the near-infrared spectra of the surface. Additional H2O ice is cold-trapped onto the surface of the CO2 ice deposit during this time. Sublimation during the spring is not uniform, and depends on the thermal inertia properties of the surface, including depth of ground ice. All of the seasonal ices have sublimated by mid-spring; however, a few permanent ice deposits remain throughout the summer. These are small water ice deposits on the north-facing slopes of Heimdal Crater and adjacent plateaus, and a small patch of mobile water ices that chases shadows in a small crater near the landing site. During the late spring and early summer, the site is free of surface ice. During this time, the water cycle is dominated by vapor exchange between the subsurface water ice deposits and the atmosphere. Two types of subsurface ice were found at the Phoenix landing site: a pore water ice that appears to be in diffusive equilibrium with the atmosphere, and an almost pure water ice deposit that is apparently not in equilibrium. In addition to vapor and solid phases of the water cycle, there is strong evidence of a liquid phase. Patches of concentrated perchlorate salt are observed in trenches dug by the lander. Perchlorate is believed to form at the landing site through atmospheric interactions, which deposit the salts on the surface. The salts are then dissolved and translocated to the subsurface by thin films of liquid water. These thin films may arise due to perchlorate interactions with the atmospheric water vapor or seasonal ices. It is possible that the winter CO2 ice slab may act as a greenhouse cap, trapping enough heat for the underlying fall-deposited water ice to react with the perchlorate to form thin films of brines. Alternatively, the brines may form when summertime water vapor interacts with perchlorate on the surface, when temperatures rise above the perchlorate brine eutectic

Compositions of Subsurface Ices at the Mars Phoenix Landing Site

NASA\u27s Phoenix Lander uncovered two types of ice at its 2008 landing site on the northern plains of Mars: a brighter, slab-like ice that broke during Robotic Arm operations; and a darker icy deposit. Spectra from the Phoenix Surface Stereo Imager (SSI) are used to demonstrate that the brighter material consists of nearly pure water ice, which probably formed by migration and freezing of liquid water. The darker icy material consists of similar to 30 +/- 20 wt% ice, with the remainder composed of fine-grained soil, indicating that it probably formed as pore ice. These two types of ice represent two different emplacement mechanisms and periods of deposition

Compositions of Subsurface Ices at the Mars Phoenix Landing Site

NASA\u27s Phoenix Lander uncovered two types of ice at its 2008 landing site on the northern plains of Mars: a brighter, slab-like ice that broke during Robotic Arm operations; and a darker icy deposit. Spectra from the Phoenix Surface Stereo Imager (SSI) are used to demonstrate that the brighter material consists of nearly pure water ice, which probably formed by migration and freezing of liquid water. The darker icy material consists of similar to 30 +/- 20 wt% ice, with the remainder composed of fine-grained soil, indicating that it probably formed as pore ice. These two types of ice represent two different emplacement mechanisms and periods of deposition

Validating automated screening for psychological distress by means of computer touchscreens for use in routine oncology practice

The aim of the study was to confirm the validity of using touchscreen computers for screening for clinically significant levels of distress among cancer patients in routine oncology practice. The Hospital Anxiety and Depression Scale (HADS), EORTC Quality of Life questionnaire (QLQ-C30), Mental Health Inventory-MHI5 and a Concerns Checklist were administered via touchscreen computer to 172 chemotherapy out-patients, twice, 2–4 weeks apart. A standard psychiatric interview (Present State Examination – PSE) was conducted within a week of the second assessment. On interview, 23% of patients were identified as ‘cases’. Using the available data (questionnaires, sociodemographic details, self-reported past psychiatric history), the best screening strategy combined scores from MHI-5 and HADS from a single time-point with the following rules: if MHI-5 < 11 = non-case; if MHI-5 ≥ 11 then use HADS; then, if HADS ≥ 9 = ‘case’ (sensitivity 85%; specificity 71%; misclassification rate 26%; positive predictive value 47%). The computerized screening system enabled data to be collected, scored, collated and reported in real time to identify patients who warrant further clinical assessment. It offers the potential for improving ‘case’ detection in routine oncology practice while reducing the burden of questions put to ‘non-cases’. Further work is needed to develop optimal choice of screening questions for this purpose. © 2001 Cancer Research Campaign http://www.bjcancer.co

Seasonal Ice Cycle at the Mars Phoenix Landing Site: 2. Postlanding CRISM and Ground Observations

The combination of ground observations from the Mars Phoenix Lander and orbital data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) provided a detailed view of the formation of late summer surface water ice at the landing site and surrounding regions. CRISM observations of the landing site during and immediately after Phoenix operations were analyzed to track the seasonal and diurnal ice cycles during the late spring to late summer, and a nonlinear mixing model was used to estimate grain sizes and relative abundances of water ice and dust. The surface around the Phoenix landing site was ice-free from late spring through midsummer, although transient patches of mobile ices were observed in an 85 m diameter crater to the northeast of the landing site. At the ∼10 km diameter Heimdal Crater, located ∼10 km east of the landing site, permanent patches of water ice were observed to brighten during the late spring and darken during the summer, possibly as fine-grained water ice that was cold trapped onto the ice during late spring sintered into larger grains or finally sublimated, exposing larger-grained ice. CRISM spectra first show evidence of widespread ice during the night at solar longitude (Ls) ∼ 109°, ∼9 sols before Phoenix’s Surface Stereo Imager detected it. CRISM spectra first show evidence of afternoon surface ice and water ice clouds after Ls ∼ 155°, after Phoenix operations ended

Seasonal Ice Cycle at the Mars Phoenix Landing Site: 2. Postlanding CRISM and Ground Observations

The combination of ground observations from the Mars Phoenix Lander and orbital data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) provided a detailed view of the formation of late summer surface water ice at the landing site and surrounding regions. CRISM observations of the landing site during and immediately after Phoenix operations were analyzed to track the seasonal and diurnal ice cycles during the late spring to late summer, and a nonlinear mixing model was used to estimate grain sizes and relative abundances of water ice and dust. The surface around the Phoenix landing site was ice-free from late spring through midsummer, although transient patches of mobile ices were observed in an 85 m diameter crater to the northeast of the landing site. At the ∼10 km diameter Heimdal Crater, located ∼10 km east of the landing site, permanent patches of water ice were observed to brighten during the late spring and darken during the summer, possibly as fine-grained water ice that was cold trapped onto the ice during late spring sintered into larger grains or finally sublimated, exposing larger-grained ice. CRISM spectra first show evidence of widespread ice during the night at solar longitude (Ls) ∼ 109°, ∼9 sols before Phoenix’s Surface Stereo Imager detected it. CRISM spectra first show evidence of afternoon surface ice and water ice clouds after Ls ∼ 155°, after Phoenix operations ended

Seasonal H2O and CO2 Ice Cycles at the Mars Phoenix Landing Site: 1. Prelanding CRISM and HiRISE Observations

The condensation, evolution, and sublimation of seasonal water and carbon dioxide ices were characterized at the Mars Phoenix landing site from Martian northern midsummer to midspring (Ls ∼ 142° – Ls ∼ 60°) for the year prior to the Phoenix landing on 25 May 2008. Ice relative abundances and grain sizes were estimated using data from the Compact Reconnaissance Imaging Spectrometer for Mars and High Resolution Imaging Science Experiment aboard Mars Reconnaissance Orbiter and a nonlinear mixing model. Water ice first appeared at the Phoenix landing site during the afternoon in late summer (Ls ∼ 167°) as an optically thin layer on top of soil. CO2 ice appeared after the fall equinox. By late winter (Ls ∼ 344°), the site was covered by relatively pure CO2 ice (∼30 cm thick), with a small amount of ∼100 μm diameter water ice and soil. As spring progressed, CO2 ice grain sizes gradually decreased, a change interpreted to result from granulation during sublimation losses. The combined effect of CO2 sublimation and decreasing H2O ice grain sizes allowed H2O ice to dominate spectra during the spring and significantly brightened the surface. CO2 ice disappeared by early spring (Ls ∼ 34°) and H2O ice by midspring (Ls ∼ 59°). Spring defrosting was not uniform and occurred more rapidly over the centers of polygons and geomorphic units with relatively higher thermal inertia values

Seasonal H2O and CO2 Ice Cycles at the Mars Phoenix Landing Site: 1. Prelanding CRISM and HiRISE Observations

The condensation, evolution, and sublimation of seasonal water and carbon dioxide ices were characterized at the Mars Phoenix landing site from Martian northern midsummer to midspring (Ls ∼ 142° – Ls ∼ 60°) for the year prior to the Phoenix landing on 25 May 2008. Ice relative abundances and grain sizes were estimated using data from the Compact Reconnaissance Imaging Spectrometer for Mars and High Resolution Imaging Science Experiment aboard Mars Reconnaissance Orbiter and a nonlinear mixing model. Water ice first appeared at the Phoenix landing site during the afternoon in late summer (Ls ∼ 167°) as an optically thin layer on top of soil. CO2 ice appeared after the fall equinox. By late winter (Ls ∼ 344°), the site was covered by relatively pure CO2 ice (∼30 cm thick), with a small amount of ∼100 μm diameter water ice and soil. As spring progressed, CO2 ice grain sizes gradually decreased, a change interpreted to result from granulation during sublimation losses. The combined effect of CO2 sublimation and decreasing H2O ice grain sizes allowed H2O ice to dominate spectra during the spring and significantly brightened the surface. CO2 ice disappeared by early spring (Ls ∼ 34°) and H2O ice by midspring (Ls ∼ 59°). Spring defrosting was not uniform and occurred more rapidly over the centers of polygons and geomorphic units with relatively higher thermal inertia values