 NASA has speculated on the feasibility of mining the atmospheres of the outer planets , particularly for helium @-@ 3 , an isotope of helium that is rare on Earth and could have a very high value per unit mass as thermonuclear fuel . Factories stationed in orbit could mine the gas and deliver it to visiting craft . However , the Jovian system in general poses particular 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 . 
 NASA <a href='been_done' title='1'><mark>has</mark></a> speculated on the feasibility of mining the atmospheres of the outer planets , particularly for helium @-@ 3 , an isotope of helium <a href='null_relcl' title='2'><mark>that</mark></a><a href='drop_aux' title='3'><mark>is</mark></a>rare on Earth and could have a very high value per unit mass as thermonuclear fuel . Factories stationed in orbit could mine the gas and deliver it to visiting craft . However , the Jovian system in general poses particular disadvantages for colonization because of the severe radiation conditions prevailing in Jupiter <a href='null_genetive' title='4'><mark>'s</mark></a>magnetosphere and the planet <a href='null_genetive' title='5'><mark>'s</mark></a>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 <a href='drop_aux' title='6'><mark>is</mark></a>a decisive aspect due to the fact that already an exposure to about 0 @.@ 75 Sv over a period of a few days <a href='drop_aux' title='7'><mark>is</mark></a>enough to cause radiation poisoning , and about 5 Sv over a few days <a href='drop_aux' title='8'><mark>is</mark></a>fatal . 
NASA done speculated on the feasibility of mining da atmospheres of tdaouter planets , particularly for helium @-@ 3 , an isotope of helium rare on Earth and could have a very high value per unit mass as thermonuclear fuel . Factories stationed in orbit could mines thdaas and deliver it to visiting craft . However , thedavian system in general poses particular disadvantages for colonization because of the daere radiation conditions prevailing in Jupiter  magnetosphere and the pdaet  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 a decisive aspect due to the fact dat already an exposure to bou 0 @.@ 75 Sv over a period of a few days enough to cuz radiation poisoning , and about 5 Sv over a few dayz fatal .