Colonization of the outer Solar System the Solar System's gas giant planets for exploration and possibly mining of helium-3, which could have a very high value per unit mass as a thermonuclear fuel. The Jovian system in general has particular disadvantages for colonization, including its severe radiation environment and its particularly deep gravity well. Its radiation would deliver about 3,600 rems per day to unshielded colonists on Io and about 540 rems per day to unshielded colonists on Europa. Exposure to about 75 rems over a few days is enough to cause radiation poisoning, and about 500 rems over a few days is fatal. Jupiter itself,
Parker Solar Probe the early 2010s, plans for the "Solar Probe" mission were incorporated into a lower-cost "Solar Probe Plus". The redesigned mission uses multiple Venus gravity assists for a more direct flight path, which can be powered by solar panels. It also has a higher perihelion, reducing the demands on the thermal protection system. In May 2017, the spacecraft was renamed "Parker Solar Probe" in honor of astrophysicist Eugene Parker, coiner of the term "solar wind". The solar probe cost NASA US$1.5 billion. The launch rocket bore a dedication in memory of APL engineer Andrew A. Dantzler who had worked on the