When this journal was founded the telescope had only just been invented. Humankind knew of six planets including our own. The next three centuries added Uranus, Neptune and Pluto to the known list as well as the many moons, asteroids and comets that we know today. Discoveries such as that Earth was not the centre of the universe and that planets orbit the Sun were key steps in increasing the understanding of Man'place in space. But it is only in the latter part of the 20th century that we have been privileged to carry out in situ exploration of the planets, comets and the solar wind'realm and to begin to understand the special conditions on Earth that enabled life to start here.
In this article, we briefly review our current knowledge of the Solar System that we inhabit. The Sun itself, the planets, comets and asteroids are all discussed in general terms, together with the important discoveries from space missions which have led to our current views. For each of the bodies and for the interplanetary medium we present the current understanding of the physical properties and interrelationships and present questions for further study.
We describe the solar wind and the way that it interacts with the planets and comets that it encounters. The importance of the obstacle in the magnetized plasma flow is explored in particular detail. We identify the gaps in our knowledge in each case. What is in store for planetary exploration and discoveries in the next millennium? Already, a sequence of Mars exploration missions including sample return, a landing on a comet, further exploration of Saturn and the Jovian system and the first fly-by of Pluto are planned. We examine the major scientific questions to be answered and speculate on possible space exploration in the future.