Polygonal cracks in the seasonal semi-translucent CO2 ice layer in Martian polar areas

In this paper, we use morphological and numerical methods to test the hypothesis that seasonally formed fracture patterns in the Martian polar regions result from the brittle failure of seasonal CO2 slab ice. The observations by the High Resolution Imaging Science Experiment (HiRISE) of polar regions of Mars show very narrow dark elongated linear patterns that are observed during some periods of time in spring, disappear in summer and re-appear again in the following spring. They are repeatedly formed in the same areas but they do not repeat the exact pattern from year to year. This leads to the conclusion that they are cracks formed in the seasonal ice layer. Some of models of seasonal surface processes rely on the existence of a transparent form of CO2 ice, so-called slab ice. For the creation of the observed cracks the ice is required to be a continuous media, not an agglomeration of relatively separate particles like a firn. The best explanation for our observations is a slab ice with relatively high transparency in the visible wavelength range. This transparency allows a solid state green-house effect to act underneath the ice sheet raising the pressure by sublimation from below. The trapped gas creates overpressure and the ice sheet breaks at some point creating the observed cracks. We show that the times when the cracks appear are in agreement with the model calculation, providing one more piece of evidence that CO2 slab ice covers polar areas in spring.

Creating a public tool to assess and promote transparency in global land deals: the experience of the Land Matrix

The Beta version of the Land Matrix (Land Matrix 2012) was launched in April 2012 as a tool to promote public participation in building a constantly evolving database on large-scale land deals, and making the data visible and understandable. The aim of the Land Matrix partnership is to promote transparency and open data in decisionmaking over land and investment, as a step towards greater accountability. Since its launch, the Land Matrix has attracted a high degree of attention, and stirred some controversy. It provides valuable lessons on the challenges and benefits of promoting open data on practices that are often shrouded in secrecy. This paper critically examines the ongoing efforts by the Land Matrix partnership to build a public tool to promote greater transparency in decision-making over land and investment at a global level. It intends to provoke discussion of the extent to which such a tool can ultimately promote greater transparency and be a step towards greater accountability and improved decision-making. It will present the Land Matrix and its value addition, before detailing the challenges it encountered related to the measurement of the largescale land acquisition phenomenon. It will then specify how it intends to address these issues in order to establish a dynamic and participatory tool for open development.