Why do scientists believe there are oceans on dwarf planets? Sciences

For a long time, Earth was thought to be the only planet in our solar system with an ocean, but apparently there is Underground oceans even on the most incredible icy bodies.

🪐🌙 In fact, icy moons and dwarf planets in the outer solar system appear to contain liquid oceans beneath layers of thick ice.

Recent research suggests that there may be oceans inside objects beyond Pluto.

This is surprising, because the surface temperature of these objects is much lower than -200 degrees Celsius.

Seventy years ago, it seemed plausible that Venus' hot atmosphere concealed a global ocean. But this idea was discarded in 1962, when the Mariner 2 spacecraft passed by Venus and discovered that its surface was too hot to contain liquid water.

It didn't take long for us to realize thisWhatever ocean existed on Venus, as well as on Mars, disappeared billions of years ago Due to major changes in their climate.

The revolution in thinking that paved the way for our new view of the solar system's oceans dates back to a 1979 paper by astrophysicist Stan Bell.

He predicted that Jupiter's inner moon, Io, would be so hot inside that it could be volcanically active.

a The heat source that makes this possible is the effect of gravity – Repeated tidal force interaction between Io and Jupiter's nearby moon Europa.

Europa completes exactly one orbit for every two orbits of Io. Io therefore passes Europa every two orbits, where it is regularly and repeatedly “pulled” by Europa's tidal force, preventing Io's orbit from becoming circular.

This means that The distance from Io to Jupiter is constantly changing -Hence, the intensity of Jupiter's (much stronger) tidal force, which actually distorts Io's shape.

Repeatedly distorting the tides inside it cause Io to heat up by internal friction, as if you bent a stiff wire back and forth several times, then touched the newly bent part with its lip (try this with a coat hanger or a paper clip). You will be able to feel the heat.

Bell's predictions of tidal warming were confirmed just a week after publication, when Voyager-1, which made the first advanced flyby of Jupiter, sent back images of erupting volcanoes on Io.

Io is a rocky world that does not contain any form of water, so it may appear to have nothing to do with oceans. However, the tidal interaction between Jupiter, Io, and Europa works in both directions. Europa is also heated by tides, not only by Io, but also by the next moon, Ganymede.

👉 There is now very good evidence that there is a 100 km deep ocean between Europe's ice sheet and its rocky interior.. Ganymede may have up to three or four layers of liquid, sandwiched between layers of ice.

In these cases, the heat that prevents liquid water from freezing may be caused mainly by tides.

There is, too Evidence of a region of salty liquid water inside Callisto, Jupiter's distant moon. This is unlikely to be due to tidal heating, but rather due to heat released by the decay of radioactive elements.

Saturn It has a relatively small icy moon (radius 504 km) called Enceladus. The inner ocean is thanks to tidal heating resulting from interaction with the larger MoonDione called. We are so certain that this ocean exists because Enceladus' icy crust is oscillating in a way that is only possible because this layer is not fixed within the solid interior.

In addition, the Cassini probe collected samples of water and remaining components of this inner ocean. Their measurements indicate that the ocean water on the surface of Enceladus must have interacted with the hot rocks beneath the ocean floor, and this is what happened. The chemistry there seems well suited to sustaining microbial life.

Surprisingly, even for moons that should not have tidal heating, and for celestial bodies that are not moons, Evidence for the existence of inland oceans continues to mount. The list of worlds that may have, or once did, inner oceans includes several of Uranus' moons, such as Ariel, Triton, Neptune's largest moons, and Pluto.

The closest inner ocean to the Sun may be located within the dwarf planet Ceres, although it may already be largely frozen, or may consist only of briny liquid.

What particularly fascinates me are the indications that there are oceanic worlds far beyond Pluto. The findings come from recently published results from the James Webb Space Telescope, which monitored the ratios of different isotopes (atoms with different numbers of particles called neutrons in their cores) in the frozen methane covering Eris and Makemake, two much smaller and smaller dwarf planets farther away. From Pluto.

The authors state that their observations are Evidence of chemical reactions between inland ocean water and the rocky ocean floorand also from very modern, perhaps even current, water columns.

The authors suggest that the heat generated by the decay of radioactive elements in rocks is enough to explain how these inner oceans are kept warm enough to avoid freezing.

You might wonder if all this could increase our chances of finding alien life.

Sorry to spoil the party, but several papers were presented at this year's Lunar and Planetary Science Conference in Houston (March 11-15) that state: The rocks beneath Europa's ocean floor must have been too strong to break to form the kinds of hot springs (hydrothermal fissures) on the ocean floor that fueled microbial life in Earth's early days..

It is possible that other subsurface oceans are equally inhospitable. But even now, there is still hope.

* David Rothery is Professor of Planetary Earth Sciences at the Open University.

This article was originally published on the academic news site The Conversation and is republished here under a Creative Commons license. Read the original version here (in English).