An architecture program for the robotic exploration of Venus
To date, most space exploration has focused on the solar system beyond Earth's orbit while the inner solar system between Earth and the Sun has received only limited attention. In this region, Venus, with a similar size and mass to Earth but with a very different environment, is probably the most interesting body. The most notable feature of Venus is the extreme runaway greenhouse effect. This phenomenon is considered a potential fate for the Earth in the future. Exploring Venus could help mitigate this threat. However, the environment of Venus is sufficiently challenging as to preclude the possibility of physical human presence for the foreseeable future. Consequently, robot-mediated exploration is required
Reassessing the possibility of life on venus: proposal for an astrobiology mission.
With their similar size, chemical composition, and distance from the Sun, Venus and Earth may have shared a similar early history. Though surface conditions on Venus are now too extreme for life as we know it, it likely had abundant water and favorable conditions for life when the Sun was fainter early in the Solar System. Given the persistence of life under stabilizing selection in static environments, it is possible that life could exist in restricted environmental niches, where it may have retreated after conditions on the surface became untenable. High-pressure subsurface habitats with water in the supercritical liquid state could be a potential refugium, as could be the zone of dense cloud cover where thermoacidophilic life might have retreated. Technology based on the Stardust Mission to collect comet particles could readily be adapted for a pass through the appropriate cloud layer for sample collection and return to Earth.
Life and the Evolution of Earth's Atmosphere
Harvesting light to produce energy and oxygen (photosynthesis) is the signature of all land plants. This ability was co-opted from a precocious and ancient form of life known as cyanobacteria. Today these bacteria, as well as microscopic algae, supply oxygen to the atmosphere and churn out fixed nitrogen in Earth's vast oceans. Microorganisms may also have played a major role in atmosphere evolution before the rise of oxygen. Under the more dim light of a young sun cooler than today's, certain groups of anaerobic bacteria may have been pumping out large amounts of methane, thereby keeping the early climate warm and inviting. The evolution of Earth's atmosphere is linked tightly to the evolution of its biota.