Hacker News Reader

Comment by GrantS | Hacker News Reader

The most interesting bit to me was learning why the mission involves orbiting Jupiter rather than orbiting Europa directly. Though the text doesn't make it clear, the video explains (starting at 0:59) that directly orbiting Europa would mean too much time spent in the most intense parts of Jupiter's radiation belts. Making 45 Europa fly-bys apparently avoids radiation-related issues and allows for making observations over an extended period of time to detect changes.

EDIT: The Wikipedia article on Jupiter's Magnetosphere [1] has great details on the impact of Jupiter's radiation on previous missions. For example, Pioneer 11 lost most of its images of Io, and Galileo had total data loss on three of its orbits.

[1] https://en.wikipedia.org/wiki/Magnetosphere_of_Jupiter#Explo...

View on HN

Does anyone know how this radiation affects the chance of life on the moon?

Not an expert, but in this specific case I suspect the radiation has no impact, because any life on Europa is most likely to exist tens of miles beneath the ice surface in the hypothesized warm oceans beneath.

The way I heard it described is that the ice is basically an atmosphere except it is solid instead of gaseous. It apparently provides similar benefits to our atmosphere like stabilizing temperature and shielding from radiation.

Cryosphere!

Does the "solid atmosphere" provide any unique benefits for Europa?

Do we have any information on the magnetosphere of Europa? I wonder how much protection it's providing, if any?

For comparison, Venus and Mars have magnetospheres that are smaller than their atmospheres, allowing the solar wind to blow away lighter molecules, such as water. Earth, by contrast, has a magnetosphere that's much larger, and provides significant protection.

phyugin, your comment is marked [dead] for some reason.

Real magnetospheres are created by an active core, which Venus, Mars and Europa don't have. Venus and Europa have induced magnetospheres, which are basically just the result of their ionospheres (the ionized upper atmosphere) interacting with the magnetism surrounding them (from the sun and jupiter respectively).

Mars is actually an interesting case because it used to have an active core (and hence a true magnetosphere) a long time ago but it has since died out. The latent magnetism still remaining in its iron rich crust is what protects it from the solar wind now and if you look at a 3d map from orbiting magnetometers it's all lumpy and not symmetrical in the least.

But yeah, anything below the ice in europa would be fine. Ice is an electric and thermal insulator so it doesn't even need an atmosphere to protect from dangerous radiation.

Under kilometers of ice? A non-issue.

Yep. I loved the sprinkler analogy. It's a nice solution (lots of sightseeing opportunities on an orbit that wide) and one that could only be made by very patient people.

I find it surprising we still have such a hard time shielding electronics from radiation in space. The issues the Mars rover teams have had to deal with (even with redundant systems) have been pretty crazy.

Jupiter's radiation belts are extremely strong. If you were on a spaceship orbiting around, say, Io, for example, you'd experience radiation sickness in a matter of minutes. And you'd die from radiation exposure within around a day, maybe two. That radiation environment is also very difficult for computers to cope with because it means that there is a constant rain of penetrating high-energy particles which can potentially interfere with electronic components.

Imagine a clock-work computer with exposed parts attempting to operate in an unrelenting rain of sand and gravel. That's the sort of environment that computing equipment has to deal with around Jupiter, in some ways it's surprising that they work at all.

There's a LOT of radiation in those belts around Jupiter - "Europa receives about 5.40 Sv of radiation per day.[19] (5.0 Sv is already considered lethal acute dose) from Jupiter's large radiation belts (10 times stronger than Earth's Van Allen radiation belts), and is a severe health threat to colonists without adequate radiation shielding. The satellite has only a very weak magnetosphere, which leaves it exposed to radiation by Jupiter and also the solar wind."

From Wikipedia https://en.wikipedia.org/wiki/Terraforming_of_Europa#Magneti...

Shielding electronics 'in space' is mostly solved. It does give headaches and increase costs. But orbiting Jupiter is another game entirely.

Reply on news.ycombinator.com