December 25, 2012 in Science
[- = condense] [+ = expand] [x = multiply by previous diameter]
Great Red Spot is currently condensing, once it is pushed out of the Jovian atmosphere it will begin to expand again: Io -1.18x Europa +1.7x Ganymede -1.09x Callisto +1.07x Titan -1.9x Triton +2.5x Mars +1.87x Earth -1.05x Venus -2.48x Mercury
“It’s not clear yet why the storm is shrinking, but after 300 years of hanging in there, the spot is in no danger of disappearing anytime soon, Asay-Davis said. It continues to kick up winds that routinely exceed 300 mph.
“We find that the Red Spot has been shrinking but not slowing down,” Asay-Davis told SPACE.com.
There is a balance of energy flowing in and out of the storm, either as it mixes with the surrounding atmosphere, consumes smaller storms, or when energy is radiated into space, he explained.”
“Io, the innermost large satellite of Jupiter, has the highest rate of volcanic activity of any body in the solar system. Europa and Ganymede have been largely resurfaced by mechanisms that probably involved flooding of the surface by water. A preliminary evaluation of the rate of cratering by comet impact suggests that the entire surface of Io may be no older than a million years and that the surface of Europa is less than 100 million years old.”
“The combined effects of satellite expansion, its associated tensile stress, rapid formation of near surface partial melt, and tidal stress due to an eccentric orbit may be responsible for creating Ganymede’s unique surface features.”
Video Credits: Neal Adams
“Callisto is more heavily cratered than even the oldest terrain on Ganymede, and the surface of Callisto probably records a longer geologic history than that of Ganymede.”
“Saturn’s moon Titan ripples with mountains, and scientists have been trying to figure out how they form. The best explanation, it turns out, is that Titan is shrinking as it cools, wrinkling up the moon’s surface like a raisin.”
“The estimated cratering rate on Triton by ecliptic comets is used to put an upper limit of ∼50 Myr on the age of the more heavily cratered terrains, and of ∼6 Myr for the Neptune-facing cantaloupe terrain. If the vast majority of cratering is by planetocentric debris, as we propose, then the surface everywhere is probably less than 10 Myr old. Although the uncertainty in these cratering ages is at least a factor ten, it seems likely that Triton’s is among the youngest surfaces in the Solar System”
Video Credits: Neal Adams
“Europe’s Venus Express orbiter suggests that some of the planet’s surface is made of granite, which on Earth needs water and plate tectonics to form”
“Mercury’s tectonic history is unlike that of any other terrestrial planet. On the surface of Mercury, the most prominent features produced by tectonic forces are long, rounded, lobate scarps or cliffs, some over a kilometer in height and hundreds of kilometers in length. These giant scarps are believed to have formed as Mercury cooled and the entire planet contracted on a global scale.”