During the very last year of what he himself described “as the best [eighteen] years of his life” spent at the University of Padua, Galileo first observed the heavens with a telescope. In order to appreciate the marvel and the true significance of those observations we must appreciate both the intellectual climate in Europe and the critical intellectual period through which Galileo himself was passing at the time those observations were made. Through his studies on motion Galileo had come to have serious doubts about the Aristotelian concept of nature. What he sensed was lacking was a true physics. He was very acute, therefore, when he came to sense the significance of his observations of the moon, of the phases of Venus, of the moons of Jupiter and of the Milky Way. The preconceptions of the Aristotelians were crumbling before his eyes. He had remained silent long enough, over a three month period, in his contemplations of the heavens. It was time to organize his thoughts and tell what he had seen and what he thought it meant. It was time to publish! In so doing he would become one of the pioneers of modern science. For the first time in over 2,000 years new significant observational data had been put at the disposition of anyone who cared to think, not in abstract preconceptions but in obedience to what the universe had to say about itself.

Let me first express my warmest acknowledgements to Cesare Barbieri for having taken the initiative of convening this symposium. These two days offered a unique opportunity to celebrate the scientific achievements and the legacy of Galileo Galilei. It allowed not only celebrating the scientist but also the philosopher and the human being. It was a fantastic journey in the past, present and future exploration of our universe and a fantastic retrospection into the Renaissance world which no better city than Padova would be able to offer. During these two days we could listen to a well balanced and well prepared set of excellent papers and presentations. All participants should be congratulated for their very active interactions during the discussions in the aula and also during coffee and lunch breaks.

In the first part of this paper we briefly discuss some historical constraints useful for understanding when Galileo for the first time aimed his telescope to the Moon which most probably was the first astronomical object observed by the Scientist. In the second part we discuss the dates of the observations on which the etchings, published in the Sidereus Nuncius, are based. It results that the five etchings refer to observations performed in December 1609 and January 1610. The measurement of the position, of some peculiar structures of the lunar surface clearly represented by Galileo in the etchings, shows that he was very careful in trying to produce a faithful graphical rendering of what he was observing.

The review contains the most recent data on near-Earth objects such as their sizes and densities, rotation and shapes, taxonomy and mineralogy, optical properties and structure of their surfaces, binary systems among the NEOs and internal structure of asteroids and comets constituted the NEO population.

By the beginning of 2010 the total number of natural satellites and multiple systems in the Solar System was equal to 350, including: 168 satellites of large planets, 119 multiple asteroids (including main-belt and near-Earth asteroids, Mars-crossers and Jupiter Trojan asteroids) and 63 multiple transneptunian and Kuiper-belt objects. Meanwhile, we cannot count precisely how many moons in total have been discovered to date due to the deficiency of accepted definitions.

We present the various activities and infrastructure dedicated to educational scientific and technological outreach of the MCT/Laboratório Nacional de Astrofísica, Brazil and how useful they are in diminishing the scientific illiteracy of the layman, the young, the senior citizens and the handicapped. We also explore the future endeavors and commitments that scientists and educators are to face in order to bring enlightenment.

Recent studies have demonstrated the benefits of using electrodynamic tethers (EDT) for the exploration of the inner region of the Jovian system. Intense planetary magnetic field and reasonable environmental plasma density make the electrodynamic interaction of the conductive tether with the plasmasphere strong. The interaction is responsible for a Lorentz force that can be conveniently used for propellantless maneuvers and extraction of electrical power for on board use. Jupiter and the four Galilean Moons represent an exceptional gravitational environment for the study of the orbital dynamics of an EDT. The dynamics of such a system was analyzed using a 3-body model, consisting of the planet plus one of its moons (Io in this work) and the EDT itself. New and interesting features appear, like for example the possibility to place the tether in equilibrium with respect to a frame co-rotating with the moon at points that do not coincide with the classical Lagrangian points for non-null electrodynamic forces.

The discovery of Io and her fellow Medicean Stars clearly altered the course of science as a whole. It is equally clear that the discovery of Io's tidal heating has altered the course of planetary science. One of the most directly observable consequences of Io's tidal heating is the prodigious escape of a ton per second of volcanically-supplied gases. I will review how studies of Io's escaping atmosphere since 1972 have advanced our deep understanding of Io itself, and helped formulate our perspective on planetary evolution in our solar system and beyond.

A comparison of the Jovian and Saturnian rings is made by reviewing the recent advances in planetary spacecraft exploration and theoretical study. Two main issues are addressed, namely, the different structures of these two planetary ring systems and the water ice composition of the Saturnian rings. It is suggested that answers might be found by invoking tidal capture of Trans-Neptunian Objects with highly differentiated structures even though catastrophic breakup of pre-existing satellites in the ring regions remains a real possibility. Erosion mechanisms such as meteoroid impact, photo-sputtering, orbital instability of charged dust particles and thermal evaporation acting at different time scales could lead to the preservation of the Saturnian ring system but not the Jovian ring system of large mass originally.

Galileo's work had a profound influence on our understanding of the question of “other worlds” and the possibility of other intelligent life in the universe. When he saw the Moon with its mountains, and Jupiter with its moons, he implicitly recognized that these were physical places and thus could themselves be possible abodes for life. But some ancient and medieval scholars had already suggested as much, though without the empirical backing that Galileo's observations provided. Thus perhaps an even more important influence on the development of these ideas is that Galileo made them popular with the educated public, rather than merely the speculations of specialists. By inciting the popular imagination to take seriously the possibility of other worlds, he engaged subsequent generations of philosophers and storytellers to explore the possibilities and implications of life on those worlds.

Galileo's support to the Copernican theory was decisive for the revolutionary astronomical discoveries he achieved in 1610. We trace the origins of Galileo's conversion to the Copernican theory, discussing in particular the Dialogo de Cecco di Ronchitti da Bruzene in perpuosito de La Stella Nuova. Later developments of Galileo's works are briefly treated.