Some Problems

For reference, see Sibylla.

Three Places Where A Spaceman Can Be In Danger
in space
on another planet
on "...an Earth grown strange..." (p. 76) in his absence

So he is not safe anywhere!

Problems on Sibylla
native species are poisonous and poison the soil
a field must be empty for years before it can grow a crop
diseases
stormwinds
long nights
strange seasons
shortages of trace elements
ultraviolet poverty
irradiation
the wrong gravity for fluid balances
geological instability
collapsing mines

Other Colonized Planets
Zion has worse wildlife.
Atlas is heavier.
Asgard has an ice age.
Lucifer is hotter.

But Sibylla alone has been attacked - so far.