Artists Impression of “Titanic” Icebergs
Credit : JPL
One of the most promising potential locations for eventual human settlement in the outer solar system is Saturn’s fascinating moon, Titan.
Bigger than innermost planet Mercury, half again as large as our own Moon, and second only to Ganymede in total size, Titan possesses a thick nitrogen atmosphere, which blankets a bizarre frigid landscape dominated by the hydrocarbons methane and ethane. Perhaps the most unusual feature however, is that the hydrocarbons exist in the form of a vast network of seas and large lakes, making it the only other planetary body in our solar system known to have stable liquids on its surface.
Eight years ago, on January 14, 2005, the European Space Agency built Huygens probe, carried to Titan by the Cassini spacecraft, became the first man-made spacecraft to land on a planetary body in the outer solar system. Based on descent analysis and some of the 350 pictures send back to Earth, it apparently landed in a dry area not far from the shoreline of one of the many seas.
Now, scientists studying data from the Cassini probe orbiting the Saturnian system have concluded that many of those seas likely contain floating “icebergs” of methane and ethane made buoyant by a small percentage of nitrogen “air” in their composition. According to the theory, the hydrocarbon ice could float or sink depending on seasonal variations in temperature. As Titan’s northern lakes warm slighty with the coming spring, Cassini’s radar should be able to detect first increased reflection as submerged ice comes to the surface, followed by a decrease as it melts into the seas.
While it is a truly cold world, -179 degrees Centigrade, the organic components comprising the surface environment mean it is a possible abode of microbial life. It is also a veritable planetary filling station for rocket fuel, which though far too distant to have any bearing on an Earth-Moon-Mars transportation infrastructure, at least offers a ready-made supply for local operations, particularly ascent and descent from Titan itself. Titan’s greatest asset however, may be what it doesn’t have, which is an abundance of fatal radiation due to both its thick atmosphere, as well as the overall weaker magnetic field of Saturn, meaning the entire system is not constantly awash in high doses of radiation like that found around Jupiter.
As compelling as Saturn’s system is, which contains at last 62 moons, most of which are tiny, but also the brilliantly reflective water ice world of Enceladus which is dominated by ice geysers shooting into space, it may be quite some time before we can build on the fantastical knowledge base provided by Cassini. Besides limited budgets and two very expensive flagship programs in SLS and JWST, the U.S. has allowed its capacity to produce nuclear fuel for space reactors, of the type which powers Cassini, and critical for missions beyond Mars, to fade to essentially nothing.
For all the talk of the importance of STEM education initiatives, it is difficult to reconcile the lack of any follow-up on a major success story such as provided by Cassini with the potential for engaging successive generations of engineers and scientists to dig deeper into the mysteries being revealed, particularly given the long time frame between any project start, transit time, and the arrival of the first bits of data.
While both NASA and the Department of Energy are working to develop a more efficient type of space reactor, the Advanced Stirling Radioisotope Generator, which would require fewer PU- 238 pellets but provide a higher yield, the need for renewed production is a real problem which is being studiously ignored by Congress.