In the seventeenth and eighteenth centuries it became possible to believe in the existence of life on other planets on scientific grounds. Once the Earth was no longer the center of the universe according to Copernicus, once Galileo had aimed his telescope at the Moon and found it a rough globe with mountains and seas, the assumption of life on other planets became much less far-fetched. In general there were no actual differences between Earth and Venus, since both planets orbited the Sun, were of similar size, and possessed mountains and an atmosphere. If there is life on Earth, one may ponder why it could not also exist on Venus. In the extraterrestrial life debate of the seventeenth and eighteenth centuries, the Moon, our closest celestial body, was the prime candidate for life on other worlds, although a number of scientists and scholars also speculated about life on Venus and on other planets, both within our solar system and beyond its frontiers. Venusians: the Planet Venus in the 18th-Century Extraterrestrial Life Debate (PDF), from The Journal of Astronomical Data (JAD) Volume 19, somewhat via NPR and their mention of amateur astronomer Thomas Dick's estimations of the populations of the other planets in our solar system (Archive.org online view of Celestial scenery, or, The Wonders of the planetary system displayed, 1845).
The United Stated Geological Survey has finished a six-year effort to map the surface of Jupiter's moon Io. [more inside]
At least three million tons of fishlike creatures could theoretically live and breathe on Europa, according to Professor Richard Greenberg of the University of Arizona in Tucson. Greenberg recently presented his findings to the Division for Planetary Sciences, American Astronomical Society (PDF, Google quick view). Greenberg has written about potential life on Europa before, but his recent calculations suggest that the concentrations of oxygen would be great enough to support not only microorganisms, but also more complex animal-like organisms which have greater oxygen demands. [more inside]
Saturn's enigmatic moon Titan holds on to its mysteries. Radar images reveal quite a bit of variation but no clear interpretation. The hazy atmosphere prevents the sudden shock of discovery that characterized the Voyager and Galileo flybys of the moons of Jupiter, revealing little more than fuzzy Rorschach blobs. With less than 1% of the surface mapped, researchers suspect that Titan has a young surface shaped by processes that have yet to be revealed.
NASA's Official 'Galileo Dies' Page. Galileo is set to crash into Jupiter on Sunday. Responsible for many great images and tons of information, Galileo served well. Find a complete history of the Galileo mission here. Also, don't forget to watch the End of Mission webcast this Sunday at approx. 2 PM EST here.
Swan song for a great explorer. Tomorow, the Galileo explorer will make a flyby of Jovian moon Amalthea ending pehaps the geatest unmanned mission in NASA history. Galileo telemetry may not survive the flyby having already receieved much more radiation than it was designed for. Even if it does survive, this will be its final orbit scheduled to crash into Jupiter in September of next year. In spite of antenna difficulties, the spacecraft returned many beautiful images of Jupiter's moons, along with coverage of the Shoemaker-Levy collision and the first atmospheric probe to decend into Jupiter's weather.