The mystery of the missing deltas on Titan: None found even with new analysis
There are seas, lakes, and rivers on Saturn's moon Titan. However, with a few exceptions, no river deltas exist. That's not due to the research instruments.
False color image of the waters of Titan, the deltas are missing
(Image: NASA / JPL-Caltech / Agenzia Spaziale Italiana / USGS)
Although Saturn's moon Titan is the only celestial body in the solar system apart from Earth to have a liquid cycle on its surface, including lakes, seas and rivers, deltas are almost completely absent. This has now been confirmed by a research team led by planetologist Sam Birch of Brown University, without having an explanation for this. The research group simulated how the SAR radar instrument on Saturn's Cassini probe would have imaged such deltas if they existed there. The result was that deltas should be clearly visible. The fact that they are almost completely absent from the images therefore means that they really do not exist.
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Titan's surface is hidden under a dense atmosphere, so we only have insights into the surface thanks to the observations of the Cassini mission. Since then, we have known about the extensive liquid cycle, which is not based on water but on methane and ethane. These substances form huge bodies of water, but also rivers. It would therefore be reasonable to expect that deltas also exist there, as these structures are part of almost every river on Earth. We have also found traces of them on Mars. To find out whether we just don't see them on Titan, the research team simulated how Cassini would have imaged the deltas on Earth. These would therefore be clearly recognizable.
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Why there are no deltas on Titan despite the liquid cycle is still unclear, the team writes. The liquids present there should actually form such bottom structures. The liquid levels might fluctuate so much that possible deltas do not have time to form, and winds and tidal forces could also counteract them. However, further research is needed to answer these questions. The team also points to other mysteries, such as pits in the middle of seas and lakes and deep channels in the middle of bodies of water. Their origin is completely unclear. The work on the deltas is presented in the specialist journal JGR Planets.
(mho)
