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Comment by belter | Hacker News Reader

Not optimistic about the possibility of life in Europe. Tenuous atmosphere so little protection from the Sun. Also radiation is maybe too strong. Europa receives around 600 rem of radiation per day.

It's so much radiation it shines:

"Europa Glows: Radiation Does a Bright Number on Jupiter's Moon"

https://www.nasa.gov/feature/jpl/europa-glows-radiation-does...

I say we land on Titan: "Let's Colonize Titan"

https://blogs.scientificamerican.com/guest-blog/lets-coloniz...

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> Not optimistic about the possibility of life in Europe.

Is that a typo or a comment on the current political situation?

Anyway, a couple of meters of water would block all radiation, and the energy source would be tidal forces from Jupyter, not the Sun (which is what would also keep the core warm enough for liquid water. Also why Io has intense volcanic activity).

Yeah Freudian slip... Not optimistic about life on Europa and the continuation of life in Europe.

Obviously not on the surface in the vacuum and frozen ice but down in the liquid interior you're protected from the radiation by all those kilometres of water. On Earth we had kemosynthetic life for hundreds of millions of years before photosynthesis was evolved so the lack of sunlight isn't a problem, provided Europa has undersea vents or the equivalent. Scientists seem to think it has some volcanism down there but of course More Research Is Needed.

One theory for the formation of cell membranes actually relies on hydrothermal vents.

Yeah. And I'd say that anybody wanting to think about life on other planets ought to read Nick Lane's book about the early evolution of life on ours.

> It's so much radiation it shines

I'll continue to believe that this is bioluminescence.

How well does water shield radiation like this? For much of it (electrons, UV photons) a thin film on the surface could be enough protection. A layer of salty ice should be more than sufficient, I would think.

Water shields extremely well. I don't think we'll find living things on the surface, but the oceans are what is exciting, especially possibly hydrothermal vents, which have lots of life on Earth. A surface mission would be looking for signs of life, not life.

All that ice and water is what would protect life, not an atmosphere. Europe has huge warm water oceans, in some estimates more water than Earth. It may have hydrothermal vents from tidal heating, providing everything required for life. Or so the story goes.

Both Europa and Titan are technically ocean worlds, but the likelihood of Titan containing life is much lower I think, given it is so cold that methane is the main surface liquid.

>I say we land on Titan

I think many scientists would agree: If there is life on any world in the Solar System, we should not land there.

Colonial powers across the world, old and new: "hold my beer!"

Its such an unbelievable sad topic. Especially since its quite clear that nobody will be stopped by this consideration. Just think of the drilling into the ocean below the Antarctic ice. Contamination is carelessly accepted by opportunistic bureaucrats.

The new report from the National Academies [1] is recommending Enceladus.

[1]: https://nap.nationalacademies.org/read/26522/chapter/2

Life on europa id always discussed under ice, which is thick enoufh to block all radiation

True, but without light it's even harder. Of course we have seen life here around thermal vents but did it originate without light?

Light is not needed. Life on Earth got along fine without photosynthesis for hundreds of millions of years, and the hypothesis that life first appeared on Earth on the seafloor around thermal vents is quite plausible, even if we might never know for sure.

Life was also around here when the earth was a snow ball covered in ice.

Yes, although I think it's still debated whether there actually were any "total snowball" events or whether even the most severe ones still had open ocean near the equator.

> Europa receives around 600 rem of radiation per day.

Fragile nucleic acids may not be the heritable information storage mechanism of extraterrestrial life.

I share your cynicism, though.

Should be "Not optimistic about the possibility of life on Europa." but the first statement also true...

We are landing on Titan. Why not both?

There is definitely life there.

I visited once, and the residents were friendly. Europe is quite nice.

While there is life there. There is an Orc threatening.

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