The feasibility of using an L1 positioned dust cloud as a method of space-based geoengineering

In this paper a method of geoengineering is proposed involving clouds of dust placed in the vicinity of the L1 point as an alternative to the use of thin film reflectors. The aim of this scheme is to reduce the manufacturing requirement for space-based geoengineering. It has been concluded that the mass requirement for a cloud placed at the classical L1 point, to create an average solar insolation reduction of 1.7%, is 7.60x1010 kg yr−1 whilst a cloud placed at a displaced equilibrium point created by the inclusion of the effect of solar radiation pressure is 1.87x1010 kg yr−1. These mass ejection rates are considerably less than the mass required in other unprocessed dust cloud methods proposed and are comparable to thin film reflector geoengineering requirements. Importantly, unprocessed dust sourced in-situ is seen as an attractive scheme compared to highly engineered thin film reflectors. It is envisaged that the required mass of dust can be extracted from captured near Earth asteroids, whilst stabilised in the required position using the impulse provided by solar collectors or mass drivers used to eject material from the asteroid surface

Use of orbiting reflectors to decrease the technological challenges of surviving the lunar night

In this paper the feasibility of using lunar reflectors to decrease the technological challenges of surviving the lunar night is investigated. This is achieved by attempting to find orbits in the two-body problem where the argument of periapsis is constantly Sun-pointing to maximise the time spent by the reflectors over the night-side of the Moon. Using these orbits the ability of reflectors of varying sizes to provide sufficient illumination to a target point on the surface is determined for scenarios where a latitude band is constantly illuminated and a scenario where a specific point is tracked. The optimum masses required for these far-term scenarios are large. However, a nearer-term scenario using low altitude orbits suggest that the effective duration of the lunar night can be reduced by up to 50% using a set of 300 parabolic reflectors of 100m radius with a total system mass of 370 tonnes. A system is also demonstrated that will allow a partial illumination of the craters in the Moon’s polar region for a mass up to 700kg

Geo-engineering using dust grains in heliotropic elliptical orbits

This paper examines the concept of a Saturn-like Earth ring comprised of dust grains to offset global warming. A new family of non-Keplerian periodic orbits, under the effects of solar radiation pressure and the Earth’s oblateness J2 perturbation, is selected to increase the lifetime of the passive cloud of particles and, thus, increase the efficiency of this geo-engineering strategy. An analytical model is used to predict the evolution of the dust due to solar-radiation pressure and the J2 effect. The attenuation of the solar radiation can then be calculated from the ring model. In comparison to circular orbits, eccentric orbits yield a more stable environment for small grain sizes and therefore achieve higher efficiencies when the orbital decay of the material is considered. Moreover, the special orbital dynamics experienced by high area-to-mass ratio objects, influenced by solar radiation pressure and the J2 effect, ensure the ring will maintain a permanent heliotropic shape, with dust spending the largest portion of time on the Sun facing side. It is envisaged that small dust grains can be released with an initial Δv to enter an eccentric orbit with Sun-facing apogee. Finally, an estimate of 5.94x1011 kg is computed as the total mass required to offset the effects of global warming

Chromatin dynamics during interphase and cell division:similarities and differences between model and crop plants

Genetic information in the cell nucleus controls organismal development, responses to the environment and finally ensures own transmission to the next generations. To achieve so many different tasks, the genetic information is associated with structural and regulatory proteins, which orchestrate nuclear functions in time and space. Furthermore, plant life strategies require chromatin plasticity to allow a rapid adaptation to abiotic and biotic stresses. Here, we summarize current knowledge on the organisation of plant chromatin and dynamics of chromosomes during interphase and mitotic and meiotic cell divisions for model and crop plants differing as to the genome size, ploidy and amount of genomic resources available. The existing data indicate that chromatin changes accompany most (if not all) cellular processes and that there are both shared and unique themes in the chromatin structure and global chromosome dynamics among species. Ongoing efforts to understand the molecular mechanisms involved in chromatin organisation and remodeling have, together with the latest genome editing tools, potential to unlock crop genomes for innovative breeding strategies and improvements of various traits

Macro-scale space systems for geoengineering

There are many pressures facing the future of human presence on the Earth. These are the effects of a changing climate and the finite resources of Earth. This thesis sets out several space-based scenarios that can be implemented to reduce these pressures, namely space-based geoengineering to offset the effect of a warming climate and the use of orbiting reflectors to reduce the challenges of human exploration of the Moon. Several dust cloud based geoengineering methods are investigated, with the aim of improving on the previously held view that these methods are extremely costly and far-term. These include an initially static dust cloud located in the vicinity of the L₁ position, a dust cloud created by ejection from the L₁ point, a dust cloud anchored at L₁ by the mass of a large, captured, near-Earth asteroid and an Earth ring. For all of these concepts the orbital dynamics and other contributing factors were considered to determine the mass of dust required to sustain the dust cloud, which is used as the main benchmark of feasibility. As well as this, the engineering feasibility of each concept is considered with a consideration also of the effect each method has on the climate. From this analysis it is concluded that the dust cloud ejected from the vicinity of the L₁ point is the most feasible concept.There are many pressures facing the future of human presence on the Earth. These are the effects of a changing climate and the finite resources of Earth. This thesis sets out several space-based scenarios that can be implemented to reduce these pressures, namely space-based geoengineering to offset the effect of a warming climate and the use of orbiting reflectors to reduce the challenges of human exploration of the Moon. Several dust cloud based geoengineering methods are investigated, with the aim of improving on the previously held view that these methods are extremely costly and far-term. These include an initially static dust cloud located in the vicinity of the L₁ position, a dust cloud created by ejection from the L₁ point, a dust cloud anchored at L₁ by the mass of a large, captured, near-Earth asteroid and an Earth ring. For all of these concepts the orbital dynamics and other contributing factors were considered to determine the mass of dust required to sustain the dust cloud, which is used as the main benchmark of feasibility. As well as this, the engineering feasibility of each concept is considered with a consideration also of the effect each method has on the climate. From this analysis it is concluded that the dust cloud ejected from the vicinity of the L₁ point is the most feasible concept