For the Greeks and many who followed them, the Earth was unique at the center of the Universe. The heavens were imagined to be made of a totally different, ethereal substance. Less that a half century ago it was still fashionable to describe the moon as made of blue cheese! Many thought that unlikely, yet others still thought contrary evidence was slim.
We have now come a long way in a short time interval. Since 1960 the Soviet Union and the United States have sent instruments to the moon and the United States has sent humans to collect rock samples and make observations. Instrumented probes have been sent to Mars, Venus, Mercury, and then to some of the the outer planets. In recent years probes to do chemical analysis have even been sent to some of the moons of Jupiter and Saturn. Much has been learned about the chemistry and history of our neighboring planets and their moons. Searches for planets orbiting other stars have begun to catalog findings.
But investigations starting a hundred years earlier with the spectral studies by Bunsen and Kirchhoff and later applied by astronomers showed that the entire universe is made from the same eight dozen or so elements discovered here on earth. Later after Rutherford demonstrated that heavier atoms can be fused together from lighter ones and Lise Meitner used Einstein's E = mc2 to explain that very massive atoms fission apart to form lighter ones, an explanation of how atoms are synthesized in stars was proposed. While the most spectacular demonstrations of the correctness of those explanations were the awesome explosions of atomic and Hydrogen bombs, more thorough verification has been done in the world's high energy accelerators. In particular, a number of the latest elements have been created at GSI in Darmstadt, Germany, adding even more details to our understanding of how nature manufactures atoms.
But the most significant conclusion of these newer fields of chemistry is that the entire knowable cosmos is composed of elements identical to those we have here on earth. The compositions are not in the same proportions everywhere because those are governed by the local gravity. (The Earth, being small compared to stars, has not been able to hold on to a proportionate amount of Hydrogen and Helium). New evidence about the still poorly understood dark matter and dark energy extends but doesn't contradict this conclusion. It is still a matter of conjecture, but many scientists believe that similar chemistry throughout the universe makes the possibility of life elsewhere in the universe highly probable. But the enormous size of the universe and the apparent limitations caused by the speed of light, the universal speed limit, could make any two way communication impossible.
If you are interested of recent information about the Planets and the more distant Universe, access that via Daniel Fischer's Cosmic Mirror or his index page.