Fjordman’s latest science-related essay has been published at Vlad Tepes. Some excerpts are below:
I touched briefly upon the subject of astrobiology in my history of geology, Earth science and planetary science, but I will expand upon this here. The best-explored planet next to our own is without doubt Mars, which has been visited by several orbiters as well as by a number of robotic probes on the surface. The most successful ones to date have been the twin Mars Exploration Rovers Spirit and Opportunity from the United States. Originally intended for just a 90-day mission, the rovers landed on opposite sides of the planet in January 2004, but were still exploring the Martian surface as of 2010. The Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology in the USA, manages the rovers on behalf of NASA.
Next to Mars, the most promising candidates for primitive life in our immediate neighborhood might not be the planets but rather some of their natural satellites. Jupiter’s huge moon Ganymede is the largest moon in our Solar System. Like Saturn’s moon Titan it is larger in diameter than the innermost planet Mercury but has less mass. Ganymede is the only natural satellite in the Solar System known to possess a magnetosphere, which is suspected to be generated through convections within a liquid, iron-rich core, not too different from the Earth.
While it is the least massive of Jupiter’s major Galilean moons, Europa is one of the most interesting bodies in the entire Solar System for astrobiologists and is strongly suspected to harbor a subsurface liquid water ocean. The same could be true of Ganymede and possibly Callisto, although this is considered less likely. If water contains a little bit of ammonia this has an antifreeze effect that could enable liquid water to exist at temperatures significantly below those of liquid freshwater or even seawater here on Earth. With a diameter of over 4,800 km, Callisto is almost the size of Mercury. Unlike Io, Europa and Ganymede, Callisto does not experience much tidal heating and orbits beyond Jupiter’s main radiation belts. “ It is thought to be a long dead world, with a nearly complete absence of any geologic activity on its surface.” Any heat generated within it would have to come from radioactive decay alone.
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In contrast, the gravitational influence of Jupiter squeezes Europa as it orbits from one side of the planet to the other. This “tidal flexing” should keep its core molten and result in volcanic activity, just like at its neighbor Io which is closer to Jupiter. The downside is that Europa orbits within the unfriendly radiation environment of its planet’s powerful magnetosphere.
Io, the innermost of the Galilean moons, is the most volcanically active body in the Solar System, with volcanoes spewing out sulfur and sulfur dioxide (SO2) to a height of hundreds of kilometers. The heat is caused by massive tidal forces generated by Jupiter and its moons. Volcanism exists on other bodies, too, but not necessarily in the form of molten rock (lava).
The American probes Pioneer 10 and Pioneer 11, launched in 1972 and 1973, were the first spacecraft to visit Jupiter and Saturn in the Outer Solar System. NASA’s Galileo spacecraft orbited Jupiter from 1995 to 2003, sent pictures and data back to the Earth and dropped a probe into the Jovian atmosphere to sample its composition. It also found evidence of what could be an ocean on Europa. New research suggests that there may be plenty of oxygen available there, possibly great enough to support not only microorganisms but perhaps also “macrofauna,” or more complex organisms like fishes. Maybe Europa has hydrothermal vents like the ones we know from the ocean floors of our planet, although this remains pure speculation. Some scientists think the origin of life on Earth occurred at such volcanic vents.
Read the rest at Vlad Tepes.