Water alteration of rocks and soils on Mars at the Spirit rover site in Gusev crater

Gusev crater was selected as the landing site for the Spirit rover because of the possibility that it once held a lake. Thus one of the rover's tasks was to search for evidence of lake sediments. However, the plains at the landing site were found to be covered by a regolith composed of olivine-rich basaltic rock and windblown 'global' dust. The analyses of three rock interiors exposed by the rock abrasion tool showed that they are similar to one another, consistent with having originated from a common lava flow. Here we report the investigation of soils, rock coatings and rock interiors by the Spirit rover from sol (martian day) 1 to sol 156, from its landing site to the base of the Columbia hills. The physical and chemical characteristics of the materials analysed provide evidence for limited but unequivocal interaction between water and the volcanic rocks of the Gusev plains. This evidence includes the softness of rock interiors that contain anomalously high concentrations of sulphur, chlorine and bromine relative to terrestrial basalts and martian meteorites; sulphur, chlorine and ferric iron enrichments in multilayer coatings on the light-toned rock Mazatzal; high bromine concentration in filled vugs and veins within the plains basalts; positive correlations between magnesium, sulphur and other salt components in trench soils; and decoupling of sulphur, chlorine and bromine concentrations in trench soils compared to Gusev surface soils, indicating chemical mobility and separation.     

Detection of regulatory variation in mouse genes

Functional polymorphism in genes can be classified as coding variation, altering the amino-acid sequence of the encoded protein, or regulatory variation, affecting the level or pattern of expression of the gene. Coding variation can be recognized directly from DNA sequence, and consequently its frequency and characteristics have been extensively described. By contrast, virtually nothing is known about the extent to which gene regulation varies in populations. Yet it is likely that regulatory variants are important in modulating gene function: alterations in gene regulation have been proposed to influence disease susceptibility and to have been the primary substrate for the evolution of species. Here, we report a systematic study to assess the extent of cis-acting regulatory variation in 69 genes across four inbred mouse strains. We find that at least four of these genes show allelic differences in expression level of 1.5-fold or greater, and that some of these differences are tissue specific. The results show that the impact of regulatory variants can be detected at a significant frequency in a genomic survey and suggest that such variation may have important consequences for organismal phenotype and evolution. The results indicate that larger-scale surveys in both mouse and human could identify a substantial number of genes with common regulatory variation.     

自我治疗:动物的生存特技

<正>鸟类、蜜蜂、蜥蜴、大象与黑猩猩等都拥有这样的生存技能——自我治疗。它们总会吃些植物来杀灭体内的寄生虫、细菌或病毒,以此缓解症状、预防疾病,或者纯粹是为了帮助消化。有些大脑只有图钉帽一样大的物种,都会不可思议地在需要的时候专门找来特定的植物吃下去,或用其他特殊方式对其加以利用。遛狗时你有看到过狗吃草吗?不用感到惊讶,那是一种自我治疗。狗如果吃草,那说明它可能肚     

Three unpublished letters to Charles Darwin: the solution to a ‘geometrico-geological’ problem

While Charles Darwin wrote his Observations on South America, he often sought the advice and help of other scientists in solving specific problems. Three letters that the Cambridge geologist and mathematician William Hopkins wrote to Darwin exemplify such aid. In these letters Hopkins was able to show Darwin how he could calculate the position of the sedimentary beds on the Chonos Archipelago, which Darwin had visited. In his first letter Hopkins sent a solution, part of which eluded Darwin. Darwin's letters to Hopkins have not yet been found, but two additional letters gave Darwin the solution he was looking for.