[LINK] "Resolving the Mysteries of Titan’s Weather"

[rfmcdonald]

Centauri Dreams' summary of the latest findings concerning the moon Titan's lakes. Why are the lakes concentrated in the north pole, not the south?

Titan can a frustrating place for meteorologists to understand because during the course of a year some things happen that, in the early days of research, didn’t make a lot of sense. The moon’s equator, for example, is an area where little rain is supposed to fall, but when the Huygens probe arrived, it saw evidence of rain runoff in the terrain. Later, storms were found occurring in the area that did not fit then current models of circulation. The new three-dimensional model simulates Titan’s atmosphere for 135 of its years, which converts to 3000 Earth years. And it produces intense equatorial rains during Titan’s vernal and autumnal equinoxes.

According to the researchers, rain is indeed rare at low latitudes, but as Schneider says, “When it rains, it pours.” And the equatorial regions aren’t the only venue on Titan that the new model addresses. Titan’s methane lakes cluster around the poles, and it has been established by Cassini’s unceasing labors that more lakes exist in the northern than the southern hemisphere. According to Schneider, methane collects in lakes near the poles because sunlight is weak enough in those regions that little methane evaporates.

As to why more lakes are found in the northern hemisphere, let me quote from the Caltech press release on this work:

Saturn’s slightly elongated orbit means that Titan is farther from the sun when it’s summer in the northern hemisphere. Kepler’s second law says that a planet orbits more slowly the farther it is from the sun, which means that Titan spends more time at the far end of its elliptical orbit, when it’s summer in the north. As a result, the northern summer is longer than the southern summer. And since summer is the rainy season in Titan’s polar regions, the rainy season is longer in the north.