Exploration of Jupiter disadvantages for colonization because of the severe radiation conditions prevailing in Jupiter's magnetosphere and the planet's particularly deep gravitational well. Jupiter would deliver about 36 Sv (3600 rem) per day to unshielded colonists at Io and about 5.4 Sv (540 rems) per day to unshielded colonists at Europa, which is a decisive aspect due to the fact that already an exposure to about 0.75 Sv over a period of a few days is enough to cause radiation poisoning, and about 5 Sv over a few days is fatal. Ganymede is the Solar System's largest moon and the Solar System's only
The Sands of Mars being kept secret from Earth. Gibson discovers that Spencer is his son. In the meantime, Spencer has formed an attachment to Irene, Hadfield’s daughter. Hadfield reveals that scientists have been working on "Project Dawn", which involves the ignition of the moon Phobos and its use as a second “sun” for Mars. It will burn for at least one thousand years and the extra heat, together with mass production of the oxygen-generating plants, will eventually – it is hoped – make the Martian atmosphere breathable for humans. Gibson finds himself so persuaded of the importance of Mars as a self-sufficient world