It’s nothing new to hear about rain, sea, and organic matter on Saturn’s largest moon, Titan. The difference with Earth is that these liquid deposits are made of methane, and not water.
But now, researchers at the University of Arizona have found an unexpected feature: an ice sheet that covers almost half the surface of the natural satellite. The details of this discovery are described in the journal Nature Astronomy.
The origin of Titan’s large amount of methane is unknown, and the presence of ice makes it even more puzzling: Scientists have defined the ice mass as a long ‘corridor’ that covers 40% of Titan’s mass , which does not match any of the surface characteristics or subsurface measurements.
The Earth went through an icy period called Snowball Earth , from which it was freed because volcanic activity began to release gases such as methane, carbon dioxide into the atmosphere … But Titan does not seem to have volcanic activity, and the presence There is no explanation for so much methane. Now, the discovery of ice makes everything even more incomprehensible.
Three orientations of the globe of Titan. Mapped in blue, the icy corridor. Credit: NASA / JPL-Caltech / Space Science Institute.
One hypothesis is that the methane could be being supplied by subsurface deposits that irrigate methane into the atmosphere. Previous studies of Titan indicate the presence of a region called Sotra, which looks like a cryo-volcano, with icy flow characteristics.
There is no explanation for the presence of methane on Titan except for the evaporation of methane from the polar lakes. But lakes contain only a third of the methane in the atmosphere and will soon be depleted.
Since past studies indicate that Titan is currently not volcanically active, the ice corridor is likely a holdover from the past. The researchers describe how the icy corridor is currently eroding, which could be an indicator of organic material.
Titan could harbor amino acids, key ingredients for life
The team’s analysis also indicates a diversity of organic material in certain regions. Although they have not been found, laboratory simulations of Titan’s atmosphere show that it is possible for biologically interesting compounds, such as amino acids, to form. Remember that amino acids are essential molecules that make up proteins and that they play a key role in almost all biological processes.
Does this mean that life could thrive on Titan? We cannot assure you. Research leader Caitlin Griffith has made the following statements: “Both Titan and Earth followed different evolutionary paths, and both ended up with atmospheres and surfaces rich in organic matter. But it is not clear if in Titan and the Earth the richness in organic matter is common, or if they are two different worlds among the worlds that could exist, also with the presence of organic matter “.
Method
The science team analyzed tens of thousands of spectral images taken from the upper surface layer using the Cassini spacecraft’s visible and infrared mapping spectrometer.
The researchers compared their results with previous studies, including those obtained from the Huygens probe, which landed on Titan in 2005. The comparison validated both the technique and the results.
The next step is to explore the polar regions where the methane seas meet.
More information : A corridor of exposed ice-rich bedrock across Titan’s tropical region, Nature Astronomy (2019). DOI: 10.1038 / s41550-019-0756-5.
