A world shrouded in mystery due to thick clouds that can't be seen in the visible spectrum, is the largest moon of the planet. When NASA's Pioneer 11 flew past Titan in 1979 it was obvious that this was the case. The cameras on all three spaceships were unable to penetrate the thick clouds of Titan, but the data from the first spaceship suggested that it might be the first body other than Earth.
It wasn't until the NASA's Cassini spacecraft had its first encounter with Titan in October 2004 that the secrets of the largest moon in the solar system were exposed. There is a world of liquid methane and ethane lakes, sand dunes encircling the equator, and evidence for an internal ocean. In December 2004, the European Space Agency's Huygens probe was released by Cassini. After entering the atmosphere and descending through the thick atmosphere, Huygens was able to land on the surface in January 2005 for an additional one hour and 10 minutes. Data from the descent and post-touchdown images revealed rounded rocks and a suite of onboard instruments gave us a better idea of the atmosphere. Even though the mission ended in September of last year, scientists are still analyzing the data and picures that were found on the largest moon of the planet.
Liquid methane and ethane are not the same as liquid water on Earth, but they are similar to the rivers, lakes, and seas of Titan. Sand dunes on Earth are made of silicate-based substances, but on Titan they are made of hydrocarbons. The water cycle on Earth is linked to the atmosphere and oceans by a seasonal liquid transport cycle.
A new model for the transport cycle on Titan was shown in a recent study.
The new model adds a unifying framework that allows us to understand how all of these environments work together.
While similar processes on Earth helped form the dunes, plains, and labyrinth terrains on Titan, the sediments on the largest moon are composed of solid organic compounds, as opposed to silicate-derived rocks found on Earth, Mars, and Venus. Scientists have been puzzled by the ability for these organic compounds to grow and be transported around Titan.
The answer was found by studying the ooids, which are small, spherical grains most often found in shallow tropical seas. These ooids form when calcium carbonate is pulled from the water column and attached to a grain. The growth of these ooids is slowed as the grains are smashed together by waves and storms. The research team suggests that the two competing mechanisms form a constant grain size, which could be happening on Titan. The study shows that Titan is not that different from Earth.
Titan has been seen as a potential analogue to Earth for a number of reasons. Earth's landscapes have lakes, rivers, and fields of sand dunes. In our study, we proposed a unifying hypothesis to explain how the observed distribution of Titan's landscapes may be generated by a global sedimentary cycle. Once we get to explore the moon in situ, we will be able to decipher any record of the past. The history of Titan's surface and atmosphere can be better understood by looking at the geology of the rocks.
NASA's upcoming mission to deliver an 8-bladed helicopter to Titan hopes to further uncover the mysteries of the largest moon in the solar system.
Lapôtre said that any observations made by Dragonfly will be revolutionary. The only other thing we have seen of Titan's surface was at low resolution. High-resolution ground observations of organic sand grains blown by winds as well as constraints on their chemical composition will help test our hypothesis.
In 2034, Dragonfly will arrive at Titan. During its baseline mission, this helicopter will sample and examine dozens of promising sites around the icy moon and advance our search for the building blocks of life.
What more secrets will be unlocked about this alien? This is why we science, because only time will tell.
As always, keep doing science and looking up.
NASA, European Space Agency, National Oceanic and Atmospheric Administration, and Geophysical Research Letters are some of the sources.
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