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Mars exploration motivates the search for extraterrestrial life, the development of space technologies, and the design of human missions and habitations. Here, we seek new insights and pose unresolved questions relating to the natural history of Mars, habitability, robotic and human exploration, planetary protection, and the impacts on human society. Key observations and findings include:
– high escape rates of early Mars' atmosphere, including loss of water, impact present-day habitability;
– putative fossils on Mars will likely be ambiguous biomarkers for life;
– microbial contamination resulting from human habitation is unavoidable; and
– based on Mars' current planetary protection category, robotic payload(s) should characterize the local martian environment for any life-forms prior to human habitation.
Some of the outstanding questions are:
– which interpretation of the hemispheric dichotomy of the planet is correct;
– to what degree did deep-penetrating faults transport subsurface liquids to Mars' surface;
– in what abundance are carbonates formed by atmospheric processes;
– what properties of martian meteorites could be used to constrain their source locations;
– the origin(s) of organic macromolecules;
– was/is Mars inhabited;
– how can missions designed to uncover microbial activity in the subsurface eliminate potential false positives caused by microbial contaminants from Earth;
– how can we ensure that humans and microbes form a stable and benign biosphere; and
– should humans relate to putative extraterrestrial life from a biocentric viewpoint (preservation of all biology), or anthropocentric viewpoint of expanding habitation of space?
Studies of Mars' evolution can shed light on the habitability of extrasolar planets. In addition, Mars exploration can drive future policy developments and confirm (or put into question) the feasibility and/or extent of human habitability of space.
Experiments were conducted from 1989 to 1991 on two silt loam and two clay soils to determine the effect of herbicides applied to the previous crop on growth and yield of rice. All herbicides were applied preplant-incorporated at recommended rates adjusted as needed for soil texture. Rice was planted the following year. Imazaquin, imazethapyr, alachlor, metolachlor, clomazone, trifluralin, and atrazine did not injure rice the year following application. Norflurazon was the only herbicide to injure rice on silt loam soils, with injury at one silt loam location in one of two years. Norflurazon and fluometuron residues caused rice injury on clay soils, and chlorimuron residues caused injury in one year on a day soil. This chlorimuron carryover injury was from August-planted soybean but did not occur from June-planted soybean. Norflurazon, fluometuron, and chlorimuron temporarily reduced rice dry matter early in the season. No herbicide reduced either rough rice or percent head rice yield on any of the soils.
Introduction: Tobacco use is common among people who have been in prison. The relationship between social stressors, risky health behaviours, and smoking cessation has not been studied in people recently released from prison. Studying this relationship could yield information that guides strategic and cost-effective tobacco cessation interventions for an under-resourced population.
Methods: One hundred and forty-three smokers were interviewed 7 to 21 days after they had been released from USA prisons. Independent variables included employment status, housing security, relationship problems, educational achievement, risky drinking behaviour, recent drug use, history of drug dependence, and depression. The primary outcome was ‘trying to quit smoking.’ Data were analysed using Pearson chi-square tests and single and multivariable logistic regression models.
Results: Of those who had to quit smoking due to tobacco-free prison policies, 98% reported relapsing on tobacco after release. Trying to quit smoking was associated with the absence of risky drinking behaviour in the past 30 days (adjusted odds ratio [AOR] 6.44, 95% confidence interval [CI] 2.02–20.48).
Conclusions: The absence of risky drinking behaviour is associated with trying to quit smoking among people recently released from prison. Further research may determine whether interventions addressing risky alcohol use can reduce smoking relapse.
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