The hint comes in the form of a ratio. All elements have a certain number of known isotopes — variants of that element with the same number of protons that differ in their number of neutrons. The ratio of one isotope to another isotope is a crucial diagnostic tool.
In planetary atmospheres and surface materials, the amount of one isotope relative to another isotope is closely tied to the conditions under which materials form. Any change in the ratio will allow scientists to deduce an age for that material...
"When we looked closely at how this ratio could evolve with time, we found that it was impossible for it to change significantly," Mandt said in a press release. "Titan's atmosphere contains so much nitrogen that no process can significantly modify this tracer even given more than four billion years of Solar System history."
Altogether, data beamed back from numerous missions suggest that no place on the moon would be a pleasant place to live, at least compared with Earth. Lunar days stretch for about 14 Earth days with average temperatures of 253 degrees Fahrenheit (123 degrees Celsius), while lunar nights also last 14 Earth days (due to the moon's rotation) and maintain a frigid cold of minus 387 degrees Fahrenheit (minus 233 degrees Celsius).
"About the only place we could build a base that wouldn't have to deal with these extremes is, oddly enough, near the lunar poles," said Rick Elphic, project scientist for NASA's LADEE probe, which studied the moon's atmosphere and dust environment before performing a planned crash into the natural satellitein April 2014. These areas likely store vast amounts of water-ice and enjoy low levels of light from the sun for several months at a time.