I'm a software developer, no formal astro-physics education, but would like to pose some questions/hypotheticals regarding interplanetary travel, and/or dynamic positioning of Earth orbiting objects using extraterrestrial fuel sources. 1. Asteroid-based hitch-hiking to other planets. Hypothetically, could an Earth-launched spacecraft a) attach to a small asteroid (to be identified in advance), b) use its own rocket fuel to alter the orbit of the asteroid such that it would be drawn into a steeper solar orbit, resulting in a slingshot trajectory which would carry it past a target planet, where it would disconnect from the asteroid, and go into orbit over the target planet? In theory, converting the potential energy of the asteroid's current stable solar orbit, into a free-ride to a distant planet using less on-board propellant than it would otherwise use going direct? 2. Restoring multi-year sea-ice in the Arctic. At the moment (March, 2018) the Arctic ice-cap has (over four decades or so) lost roughly 80% of the multi-year sea-ice, which determines the annual minimum albedo of the polar cryosphere. During periods when little or no multi-year ice is restored (such as we're in now), this locks in an increase in the amount of solar energy which is absorbed by Arctic seas & winds-aloft (rather than being reflected back into space), which in-turn raises water temperatures -- causing primordially sequestered shallow sea-bed methane-hydrates to melt, which in-turn may accelerate summer snow-melt on the Greenland ice-sheet, and cause anaerobic methane generation on Arctic land-masses due to warming of perma-frost. Since methane is a very potent greenhouse gas (greater than CO2) this could (theoretically) lead to a feed-back loop, resulting in a catastrophic release of methane into our atmosphere. Question: Is there a plausible way to deploy what amounts to an orbiting 'solar-shade', permanently positioned to cast a shadow over the Arctic, thereby enabling the restoration of some of the multi-year sea-ice which has been lost? Assuming such a structure could even be assembled, I believe it would require daily re-positioning, hence a design which would benefit from either the use of solar-wind, or some other extraterrestrial fuel source. It seems to me, while we cannot be certain current warming trends will continue, and/or that primordial methane-hydrates will actually make it into the atmosphere, climate scientists estimate the potential amount of sequestered methane release at 1000-5000 gigatons in the Arctic alone, compared to an accumulated total of 400-500 gigatons of carbon emissions over the last 200-300 years from anthropogenic sources. Given the remarkable advances in recoverable booster-rocket technology we're witnessing from SpaceX and others, I would argue that in terms of our priorities for applying those new technologies: containing a potentially existential threat to our biosphere here on Earth, should take precedence over landing humans on Mars. At a minimum, I would hope the scientific community in general (and the United States in particular) should act immediately to quantify the threat posed by Arctic methane releases which are already under way. Hoping this forum is an appropriate one for these subjects.