| VOYAGER | 1977 US space programme consisting of two unmanned probes sent to study Jupiter, Saturn, Uranus and Neptune (7) |
| GALILEO | Orbiter launched in 1989 to study Jupiter and its moons |
| VIKING | Either of two unmanned American spacecraft that reached Mars in 1976 (6) |
| GASGIANT | One of the four planets in our solar system that are composed chiefly of hydrogen and helium, namely Jupiter, Saturn, Uranus and Neptune (3,5) |
| JOVIAN | Jupiter, Saturn, Uranus, and Neptune are often referred to as the ___ planets |
| SURVEYOR | Any of a series of seven uncrewed U.S. space probes sent to the Moon between 1966 and 1968 to photograph and study the lunar surface. (8) |
| MARINER | The name for any of a series of ten uncrewed U.S. space probes sent to the vicinities of Venus, Mars, and Mercury between 1962 and 1973. The first was launched July 22, 1962, but was destroyed shortly |
| OUTER | Like the planets Jupiter, Saturn, Uranus and Neptune |
| ORBS | Jupiter, Saturn, Uranus and Neptune |
| SOLARSYSTEM | Sun, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto (5,6) |
| APOLLO | God of light and US space programme (6) |
| RIGHT | 'The ---', 1983 film about the development of the US space programme (5) |
| STUFF | 'The ---', 1983 film about the development of the US space programme (5) |
| GASGIANTS | Planets Jupiter, Saturn, Uranus and Neptune with an atmosphere consisting of hydrogen and the element described in 1 Down (3,6) |
| PIONEER | NASA space programme whose tenth and eleventh probes made the first flybys of Jupiter (1973) |
| GODS | Turn detective and see Jupiter, Saturn and Mars, perhaps (4) |
| NASA | Independent agency of the executive branch of the US government responsible for the civilian space programme |
| GREEN | 1985 PGA Championship and 1977 US Open Championship winner (6,5) (see 17A) |
| HUBERT | 1985 PGA Championship and 1977 US Open Championship winner (6,5) (see 25A) |
| HUBERTGREEN | 1985 PGA Championship and 1977 US Open Championship winner |
