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Missione Europa 18.11.15

La gelida luna di Giove con il suo gigantesco oceano sotto la superficie di ghiaccio è uno dei luoghi del Sistema Solare potenzialmente in grado di sostenere la vita.
Ars Technica racconta i piani della NASA per esplorare Europa nel prossimo decennio.

First, the bad news. Adding a lander to the Clipper will require additional technical work and necessitate a launch delay until late 2023. At that time, the massive Space Launch System rocket NASA is developing could deliver it to Jupiter in 4.6 years. Once there, the lander would separate from the Clipper, parking in a low-radiation orbit.

The Clipper would then proceed to reconnoiter Europa, diving into the harsh radiation environment to observe the moon and then zipping back out into cleaner space to relay its data back to Earth. Over a three-year period, the Clipper would image 95 percent of the world at about 50 meters per pixel and three percent at a very high resolution of 0.5 meters per pixel. With this data, scientists could find a suitable landing site.

The JPL engineers have concluded the best way to deliver the lander to Europa's jagged surface is by way of a sky crane mechanism, like the one successfully used in the last stage of Curiosity's descent to the surface of Mars. With four steerable engines and an autonomous system to avoid hazards, the lander would be lowered to the moon's surface by an umbilical cord.

Although the SLS rocket has been designed to lift as much as 70 tons into low-Earth orbit, it can only propel a small fraction of that across the 800 million kilometers of space to Jupiter, and fuel and the Clipper will consume most of that mass. The engineers have calculated they can spare a total of about 510 kg for the sky crane and lander, and of the 230 kg lander, about 20 to 30 kg can be given over to scientific instruments. That may seem slight, but it's equivalent to what the Spirit and Opportunity rovers had to work with on Mars.

That payload would contain a mass spectrometer to identify any complex biological molecules. The engineers are also trying to add a second type of spectrometer, based on Raman scattering, to provide independent confirmation of any significant findings. "Honestly," Culberson said, "if you're going to go all that way to determine if there's life on another world, why wouldn't you double-check it?"

To gather samples for the spectrometers, the lander will have a scooper and sampling arm with at least one set of counter-rotating saw blades that could penetrate to a depth of about 10 cm. At Europa's low surface temperatures, its ice is harder than steel.