Exploring the tropics of Jupiter's ocean moon Europe would be no walk on the beach.
Equatorial regions of the potentially life-supporting Europe, which has a huge ocean of salty liquid water beneath its icy shell, are probably studded with blades of ice up to 50 feet (15 meters) tall, a new study suggests.
This finding should be of interest to NASA, which is developing a lander mission that will hunt for signs of life on the 1,900-mile-wide (3,100 kilometer) satellite. [Photos: Europa, Mysterious Icy Moon of Jupiter]
"Clearly, the paper suggests very strongly that the tropics of Europe are going to be spiky, and it would be unwise to plan to land there without a specially adapted lander," lead lead author Dan Hobley, a lecturer in the School of Earth and Ocean Sciences at Cardiff University in Wales, told Space.com via email. "It would probably be safer to land further away from the equator!"
Here on Earth, exceptionally cold and dry conditions, such as those found in the Chilean Andes, can give rise to rows of jagged ice towers called "penitentes" (Spanish for "penitent," so named because they often look like people kneeling in penance).
The driving force behind penitent formation is sublimation, the transition of a material directly from solid to gas form. An initially smooth snowpack sublimates at different rates in different spots, causing small pits to form in some places. Sunlight bounces around in these pits, boosting sublimation further into the depths and eventually creating fields of spiky ice towers.
There's no reason to believe this process is restricted to our planet. Indeed, scientists think the "leaf terrain" spotted on Pluto by NASA's New Horizons spacecraft probably consists of penitents carved into methane ice.
Europe would seem to be a good bet for penitent gardens as well; Na alles, het is een koude, droge, virtueel luchtvrije wereld die helemaal in de ijs valt. So Hobley and his colleagues calculated sublimation rates around the surface of the Jupiter moon and then compared those with the rates of other erosional processes. These processes include bombardment by meteoroids and charged particles from Jupiter's powerful radiation belts.
The researchers found sublimation to be the dominant factor on equatorial Europe, the regions within 23 degrees of the moon's equator.
These are some serious putative penitents, too: Some fields could feature towers up to 50 feet (15 m) tall, spaced about 23 feet (7 m) ) separately, the scientists found. Lord on Earth, penitent heights typically range from 3 to 16 feet (1 to 5 m).
The size difference is basically a factor of time, "Hobley said." The Europe penitentes grow much (VERY!) Slower than de jordens eksempler, men på jorden, de kan være begrænset til en årstid eller måske to, indtil de smelter i sommer eller kommer i flere sneer, men på Europa, de er sat i solen for 50 millioner år. "
There are some observational support for the existence of Europe penitents as well, the researchers reported. For example, radar waves beamed that Europe from big Earth-based dishes such as Puerto Rico's Arecibo Observatory show signs of bouncing off multiple surfaces on the moon – a result that Hobley described as "really weird."
"People have tried to explain this before, but those explanations have come off in my opinion as pretty ad hoc, "he said." We have not explicitly modeled it but are pretty sure that penitents would do the trick – a lot of safety reflectors on cars, bikes, etc. work on the sam e principle of bouncing light between two sides of a cleft and firing it back out. "
We could get a look at the putative Europe penitents soon, if all goes according to plan. In the early to mid-2020s, NASA aims to launch a $ 2 billion mission called Europe Clipper, which will orbit Jupiter but study the ocean moon close to dozens of flybys.
Clipper will assess the habitability of Europe's ocean and also scout out potential touchdown sites for the lander, which will seek out signs of life that have bubbled up to the surface, or the very near subsurface, from the dark depths.
Scientists think there's a fair amount of interaction between Europe's surface and subsurface. For example, the moon's crust may harbor plates of ice, some of which dive beneath others in alien tectonic activity.
The new paper was published today (Oct. 8) in the journal Nature Geoscience.
Mike Wall's book about the search for alien life, "Out There," will be published on Nov. 13. Follow him on Twitter @michaeldwall and Google+. Follow us @Spacedotcom Facebook or Google+. Originally published on Space.com.