The Thick Atmosphere of Saturn's Titan May Thin with the Sun's 11-Year Solar Cycle

Saturn's moon, Titan, is the only moon in the solar system that has an atmosphere as thick of the Earth's. Now, scientists have discovered that Titan's atmosphere may fluctuate according to the sun's 11-year solar cycle.

The researchers analyzed data from 41 flybys of Titan by NASA's Cassini spacecraft, some at altitudes of less than 621 miles. The scientists found that the amount of methane in the atmosphere varied wildly over time. It dipped from mid-2006 to 2008, then gradually recovered for two years. It then crashed to roughly half of its 2006 peak by 2011.

What's more interesting is that these changes correspond neatly to the 11-year solar cycle, in which the sun's rotation gradually wound up its magnetic field into contorted coils, giving rise to flares and sunspots that emit ultraviolet and X-ray light. Upon reaching Titan, this powerful radiation can tear methane molecules apart.

The scientists believe that the methane destruction occurred from 2006 to 2008 during the last phases of the previous solar maximum. Upon reaching solar minimum in 2008, the sun allowed Titan's methane to recover its levels. Then as the sun ramped up activity again, the methane levels declined.

Models also revealed that during solar maximum, the broken-down methane remnants combine to form heavier hydrocarbons. These rain down through the atmosphere. During solar minimum, in contrast, the replenishment of methane comes from Titan's lower atmospheric layers.

The findings reveal a bit more about Saturn's moon and its atmosphere.

The findings are published in the Journal of Geophysical Research: Space Physics.

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