Mapa Detalhado de Ganimedes

Eu gosto mais da lua Gamimedes, por diversas razões…. entre as quais incluo uma dose menos intensa de radiação letal.

Hiding from Jupiter’s Radiation
http://www.astrobio.net/news-exclusive/hiding-from-jupiters-radiation/

The project—led by Louise Prockter of John Hopkins University as part of NASA’s Exobiology and Evolutionary Biology program—will identify dead zones where radiation would likely fry any interesting chemical compounds, as well as possible safe havens that might harbor material expelled from the ocean below

Radiation menace

Assuming the ocean contains biologically-useful compounds and that some of these find their way to the surface, they may not survive very long there.

“It is unlikely that any big molecules will be found in exposed regions,” says Chris Paranicas, also from Johns Hopkins University.

Radiation in the form of high-energy electrons and ions continuously bombard the top layers of Europa’s icy crust. This deadly dose is due to the fact that Europa—along with the three other Galilean moons (Io, Ganymede and Callisto)—orbits within Jupiter’s radiation belts.

These belts are much like Earth’s Van Allen belts but bigger, since Jupiter’s magnetic field is ten times stronger than Earth’s. Electrons and ions from the solar wind become trapped in the magnetic field and spiral down onto Jupiter’s poles to create impressive auroras.

The radiation in Jupiter’s belts is a million times more intense than in Earth’s belts. <———–

For this reason, spacecraft—such as the Galileo orbiter—have typically tried to spend as little time as possible inside the belts. Although the radiation is generally well-understood, no one has yet figured out precisely what the effect is on Jupiter’s moons.

For such mixing to happen, the same geological process that brings oceanic material up to the surface must also be shuttling surface material down to the ocean.

Safe havens

If this complicated procedure was taking place on Europa, it would be hard to verify since the radiation would destroy all evidence for it on the surface of the moon.

However, all is not lost.

The radiation belts are rotating around Jupiter faster than Europa does. This results in the radiation predominantly striking the trailing hemisphere of the moon—which is always the same portion of the moon since Europa is locked in a synchronous orbit around Jupiter. Moreover, there is a constant stream of micrometeorites landing on the leading hemisphere. These tiny rocks form a regolith layer up to 3 meters thick that could protect oceanic material from incoming radiation.

“Optimizing the search for interesting [molecular] species requires looking for young areas that aren’t heavily irradiated,” Carlson says. “The leading hemisphere is still heavily bombarded and won’t provide pristine samples by itself, but some regions may provide effective topographic shielding.”

One of the goals of the project is to pinpoint these protected regions.

Patterson thinks the boundary between trailing and leading hemispheres may be a good target.

Here, enough radiation may hit to see some of the positive effects, while enough regolith may be present to shield out most of the negative effects.

http://en.wikipedia.org/wiki/Louise_Prockter