3 ms·

Radiation levels on Europa's surface are about 5 Sv in 24 hours, which is a massive dose; for reference, this is enough to kill 50% of humans exposed to it and

Radiation levels on Europa's surface are about 5 Sv in 24 hours, which is a massive dose; for reference, this is enough to kill 50% of humans exposed to it and make the survivors extremely ill. It is also extremely cold (-171C mean) and near-vacuum (100 nanopascal). If there is life in Europa and it bears any resemblance whatsoever to the biology we know, it simply couldn't exist on the surface. Even the hardiest single-celled organisms here, which have also had 4.5B years to evolve into uncontested niches, could barely survive a limited exposure to these factors.

1970-01-01 2y ago
Check out https://en.wikipedia.org/wiki/Radiosynthesis_(metabolism) https://en.wikipedia.org/wiki/Radiosynthesis_(metabolism) I do assume this extreme level of cold and vacuum can also be acclimated in those 4.x billion years
- ericbarrett 2y ago
  Right, this is a possibility—but complex life doing so, in vacuum, at 100K? All I'm saying is, knowing what we know about chemistry, it seems extremely unlikely. I'd be ecstatic to be proven wrong empirically, but it doesn't make sense to start our search there.
lizknope 2y ago
I found this table. I picked out a few data points https://en.wikipedia.org/wiki/Sievert#Dose_examples https://en.wikipedia.org/wiki/Sievert#Dose_examples 5–10 μSv: One set of dental radiographs 10–30 mSv: Single full-body CT scan 80 mSv: 6-month stay on the International Space Station 1 Sv: Maximum allowed radiation exposure for NASA astronauts over their career 5 Sv: Calculated dose from the neutron and gamma ray flash, 1.2 km from ground zero of the Little Boy fission bomb, air burst at 600 m 5.1 Sv: Fatal acute dose to Harry Daghlian in 1945 criticality accident He died 25 days later 54 Sv: Fatal acute dose to Boris Korchilov in 1961 after a reactor cooling system failed on the Soviet submarine K-19 which required work in the reactor with no shielding He died 6 days later

1970-01-01 2y ago

Check out https://en.wikipedia.org/wiki/Radiosynthesis_(metabolism) https://en.wikipedia.org/wiki/Radiosynthesis_(metabolism) I do assume this extreme level of cold and vacuum can also be acclimated in those 4.x billion years

ericbarrett 2y ago
Right, this is a possibility—but complex life doing so, in vacuum, at 100K? All I'm saying is, knowing what we know about chemistry, it seems extremely unlikely. I'd be ecstatic to be proven wrong empirically, but it doesn't make sense to start our search there.

lizknope 2y ago

I found this table. I picked out a few data points https://en.wikipedia.org/wiki/Sievert#Dose_examples https://en.wikipedia.org/wiki/Sievert#Dose_examples 5–10 μSv: One set of dental radiographs 10–30 mSv: Single full-body CT scan 80 mSv: 6-month stay on the International Space Station 1 Sv: Maximum allowed radiation exposure for NASA astronauts over their career 5 Sv: Calculated dose from the neutron and gamma ray flash, 1.2 km from ground zero of the Little Boy fission bomb, air burst at 600 m 5.1 Sv: Fatal acute dose to Harry Daghlian in 1945 criticality accident He died 25 days later 54 Sv: Fatal acute dose to Boris Korchilov in 1961 after a reactor cooling system failed on the Soviet submarine K-19 which required work in the reactor with no shielding He died 6 days later