Photo courtesy NASA. Titan is the large figure in the background

By Ahmad A. Malik

NASA’s Cassini Mission has revealed that a mysterious cloud on the southern pole of Titan, Saturn’s largest moon, is composed of highly toxic cyanide gas. The discovery brings into question a slue of assumptions about the solar system’s second largest moon. 

The cloud, now 386,000 square miles large (roughly the size of Egypt), had been spotted growing since 2012 and baffled planetary astrophysicists. Through the Cassini Mission’s radar imaging of the planet, scientists have determined after two years of data analysis that the formation of this toxic bluish cloud over the moon’s southern pole is attributed to surprisingly low temperature in the upper reaches of the atmosphere. The cloud exists at a very high altitude of 180 miles, at which scientists previously believed that clouds couldn’t be formed since the temperature was predicted to be too high. Specifically, the cloud is made of hydrogen cyanide – a sort of ice-like substance. 

The formation of the massive cloud is in part due to the seasons changing on the solar system’s second largest moon. Titan’s dense atmosphere allows for climate changes similar to that of Earth’s, but instead of a 3-month cycle, it takes Titan seven years to invert. So as winter moves in to the Southern hemisphere of Titan, the temperature drops rapidly, allowing for the formation of icy clouds of hydrogen cyanide. This caught scientists by surprise, as they emphatically believed that hydrogen cyanide could not condense at this time or location on Titan. 

The polar atmosphere is now measured at minus 234 degrees Fahrenheit, about 180 degrees cooler than what was originally expected. When originally found in 2012, the cloud was only 30 square miles, and was referred to as a “transient figure,” by NASA. The Internet dubbed it the “Magic Island.” When Cassini returned two years later, it then found that the figure had more than doubled in size.

Any talk about a miscalculation or malfunction of NASA’s instruments was quickly ruled out after the second observation in 2012. The same area was empty in 2007, when Cassini radar imaged it.

“The fact that it’s still there shows that it isn’t just some artifact of the imaging system,” says Jason Hofgartner, the Cornell graduate student in charge of figuring out what the image represented. “Something is really happening on Titan.”

Titan is especially intriguing given its similarity to Earth. The moon has a larger volume than Mercury, the smallest planet in the solar system, though it is less massive. Titan’s atmosphere also resembles Earth’s, and it is the only celestial body with evidence of a stable body of liquid on its surface. Titan’s atmosphere has large amounts of nitrogen, just as Earth does, but also has large amounts of methane, unlike Earth. The climate features seasonal weather patterns and includes rivers, lakes and rainstorms.  

Cassini will return to Titan in 2015 to check up on the massive moon, and scientists will likely have their attention closely drawn to the cloud’s formation.