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Exploring the tropics of Jupiter's moon ocean, Europa, would not be a walk on the beach.
The equatorial regions of the potentially vital Europa, home to a huge ocean of salty liquid water under its icy shell, are probably dotted with ice sheets up to 15 meters high, according to a new study.
This discovery is likely to interest NASA, which is developing a landing mission that will look for signs of life on the 1,900 km wide (3,100 km) satellite. [Photos: Europa, Mysterious Icy Moon of Jupiter]
"It is clear that the document very strongly suggests that the tropics of Europe are going to be spiked, and it would be unwise to plan the landing without a specially adapted lander," said the senior author of the report. Study, Dan Hobley, lecturer at the School of Earth. Ocean Sciences of Cardiff University in Wales, told Space.com by email. "It would probably be safer to land further from the equator!
Here on Earth, unusually cold and dry conditions, such as those encountered in the Chilean Andes, can give rise to rows of jagged ice towers called "penitents" (in Spanish "penitent", so named because they often look like people kneeling in penance).
The driving force behind the penitential formation is sublimation, the direct transition of a material from the solid form to the gaseous form. An initially smooth snowpack sublimates at different speeds depending on the location, causing small holes in some areas. Sunlight bounces into these pits, stimulating sublimation farther into the depths and eventually creating fields of ice towers on the cob.
Blade-shaped ice towers, called penitents, are present on Earth in some high, dry, cold tropical regions – notably the Chilean Andes, as can be seen here.
Credit: ESO
There is no reason to believe that this process is limited to our planet. Indeed, scientists believe that the "blade terrain" spotted on Pluto by NASA's New Horizons satellite is probably made up of penitents carved in methane ice.
Europa would seem to be a good bet for penitent gardens; After all, it's a cold, dry and virtually airless world completely covered in ice. Thus, Hobley and his colleagues calculated sublimation rates on the surface of Jupiter's moon, and then compared them to those of other erosion processes. These processes include meteorite bombardment and charged particles from Jupiter's powerful radiation belts.
The researchers found that sublimation was the dominant factor in equatorial Europe, the regions within 23 degrees of the lunar equator. And the study team determined that sublimation had probably dug penitents in the ice.
They are also some serious putative penitents: some fields could include towers up to 15 m high, spaced about 7 m, have discovered the scientists. Here on Earth, penitent heights generally range from 3 to 16 feet (1 to 5 m).
The size difference "is basically a time factor," said Hobley. "Penitential Europa are growing a lot (MUCH!) Slower than Earth's examples, but on Earth, they could be limited to one season or maybe two until they melt in summer or get covered with snow, but they are sitting at the growing sun for 50 million years ".
The researchers also reported the existence of a number of observations concerning the existence of penitentes Europa. For example, the radar waves sent to Europa by large Earth-based antennas, such as the Puerto Rico Arecibo Observatory, are showing signs of rebound on several surfaces of the moon – a result that Hobley has described as "really strange".
Pluto's "blade terrain", seen here by NASA's New Horizons spacecraft when flying over the dwarf planet through the spacecraft in 2015, is consistent with the characteristics of ice towers called penitents.
Credit: NASA / Applied Physics Laboratory, Johns Hopkins University / Southwest Research Institute
"People have already tried to explain this before, but these explanations have become (in my opinion) quite pretty," he said. "We have not explicitly modeled it, but we are pretty sure that the penitents would do business – many safety reflectors on cars, motorcycles, and so on."
We could take a look at the putative penitent Europa soon, if all goes as planned. In the early or mid-2020s, NASA plans to launch a $ 2 billion mission called Europa Clipper, which will orbit Jupiter but will closely study the ocean moon over dozens of overflights.
Clipper will evaluate the livability of the Europa ocean and will also look for potential landing sites for the LG, which will look for signs of life that have surfaced to the surface, or very close to the surface, from the dark depths.
Scientists believe that there is a lot of interaction between the surface and the basement of Europa. For example, the crust of the moon may contain patches of ice, some of which plunge under other tectonic activities.
The new article was published today (October 8) in the journal Nature Geoscience.
Mike Wall's book on the quest for extra-terrestrial life, "Out There," will be released on November 13th. Follow him on Twitter @michaeldwall and Google+. follow us @Spacedotcom, Facebook or Google+. Originally posted on Space.com.
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