Was Titan's “magic island” caused by the organic compound “pumice”? | sorae universe portal website

Saturn satelliteTitan“It has a vast lake of liquid methane on its surface. In the lake there are several islands, some of which are temporarily observed and then disappear.Magic Island(Magic Islands)” have also been found. It is not yet known how the magical island will appear.

A research team led by Xinting Yu of the University of Texas at San Antonioporous massWe have studied the conditions under which methane floats in the lake, and shown that it meets the conditions necessary to be observed as a magic island. This is similar to imaginary islands made of pumice that appear temporarily in the Earth's oceans, then sink and eventually disappear.

■”الجزيرة السحرية” في بحيرة تيتان

القمر الصناعي زحلتيتان“أسنان،الجسم السماوي الوحيد غير الأرض الذي لوحظ أن سطحه مغطى بالسائل.يكون. بمعنى آخر، تيتان هو جرم سماوي يشبه الأرض، حيث أنه يتمتع بغلاف جوي سميك وتغيرات في الطقس والفصول. ومع ذلك، فإن متوسط ​​درجة حرارة تيتان يصل إلى -180 درجة مئوية، والسائل الموجود على سطحه ليس ماء بل مركب عضوي يتكون بشكل رئيسي من الميثان.

Titan's surface has been partially mapped. There are lakes of different sizes, including the Kraken Sea, which is larger than the total area of ​​the Japanese archipelago, and islands have also been found in some of the lakes. These islands may be real islands that exist permanently, or they may appear for only a few hours or a few weeks and then disappear. Temporary island-like structures are called “imaginary islands” or “suspicious islands” on Earth, while on Titan they are called “imaginary islands” or “suspicious islands.”Magic Island(Magic Islands).

Titan's terrain has only been observed by radar, so we don't know much about the magic island's true identity other than that it's something that tends to reflect radio waves. Previous predictions have suggested theories such as “reflection from waves in the lake”, “clumps of organic compounds floating in the lake”, “turbidity caused by organic compounds in the lake water”, and “resulting bubbles”. With nitrogen gas.”

The true identity of the Magic Island is the organic compound “pumice”

Yu and his colleagues wondered whether Titan's magic islands could be solid organic compounds floating in a methane lake, and whether the types and shapes of solid organic compounds produced in Titan's low-temperature environment might be similar to those floating in a methane lake. .

First, simple calculations showed that any type of organic compound would drown in a lake of methane. This is because all solid organic compounds are denser than liquid methane, and methane has a lower surface tension. On the other hand, it was also revealed that methane actually contains a large amount of dissolved organic compounds, so the organic compounds that come into contact with the methane lake do not dissolve and disappear.

Therefore, Yu and his colleagues discovered that the masses of organic compounds have low density.Taking into account the possibility that it has a porous structure like a sponge.an act. Even pieces of organic compounds that might sink may float in a methane lake because their density decreases if there are many voids inside them. Capillary action occurring in porous materials increases surface tension, thus providing additional buoyant forces. Moreover, even if a mass floats on a lake, over time, methane seeps into the voids, increasing its density and sinking, which explains the temporary existence of the Magic Island.

These properties are quite similar to pumice found on Earth. If you simply calculate the composition of pumice stone, you will find that its density is higher than that of seawater, so it is less likely to float in seawater. However, the voids actually reduce its density, allowing it to float in seawater. Pumice rafts formed from large-scale ejected pumice, such as the Fukutoko Okanoba eruption that occurred in 2021, look like islands. Over time, the pumice stone gradually absorbs seawater and sinks.

As a result of calculations by Yu et al., when the porosity is 25 to 60% and the diameter is several millimeters or more,The organic compound pumice can float in a methane lake long enoughIt has been shown that this pumice may have formed on the surface of the Earth. Organic compounds that initially fall to the Earth's surface in small, complex-shaped masses, such as snow, form porous masses. Eventually, as it flows like a glacier under its own weight, the mass of the lake shore will rise above the surface of the lake, break up due to waves and tidal activity and become like a floating iceberg. This corresponds to the age of the Magic Island ranging from a few hours to a few weeks.

■ Will this research solve other mysteries about Titan?

Titan's environment is unique in that it changes rapidly over a short period of time, and at the same time it is difficult to observe because it is far from Earth, and there are still many mysteries. The magical island that appears in the methane lake is just one example.

Another mystery surrounding Titan is that the surface of the lake is very smooth. Although they are much smaller than Earth's lakes, Titan's lakes are expected to contain a small amount of wave and tidal activity. However, radar observations only measured smaller changes than expected. Yu and others point out that this is because the methane lake is covered by a thin layer of organic compound ice, which is similar to the process of forming magic islands, so it may be a related phenomenon, I think so.

source

• Xinting Yu, et al. “The fate of simple organic materials on Titan's surface: a theoretical perspective”. (Geophysical Research Letters)
• Lisa Lester. “Titan’s ‘magic islands’ are likely honeycomb-shaped hydrocarbon icebergs.” (American Geophysical Union)

Written by Riri Aya