The resulting atmosphere is truly nasty from our perspective: hotter than a self-cleaning oven, with a density about 10 percent that of water and a pressure about what you'd feel a half-mile down in the ocean. These planets have 10% of their mass being water (water accounts for only 0.05% of the Earth’s mass). Several planets have atmospheres, all with different characteristics: Venus: Its atmosphere is dense, consisting mainly of CO2 and a small amount of carbon monoxide. Atmosphere in other planets. It composed of 78% nitrogen, 21% oxygen, 0.9% argon, 0.03% carbon dioxide, and trace amounts of other gases. Like planet-sized magnets, the proto-planets had sufficient gravity to draw these two gaseous elements in from the solar nebula, the vast cloud of gas and dust that surrounded the sun early in the solar system's history. For astrophysicists, it's infinitely more complex than that. Major funding for NOVA is provided by the David H. Koch Fund for Science, the Corporation for Public Broadcasting, and PBS viewers. Mars still has an atmosphere, but its pressure is 100 times less than Earth's and it's almost entirely composed of CO
The Composition of a Planet can be determined by… A hundred years ago, things were very different in astronomy. Our solar system does not have any ice planets, as the only icy objects which have these characteristics are too small to be classified as planets. During that period, the so-called inner planets—Mercury, Venus, Earth, and Mars—all developed the same kind of air, a so-called primary atmosphere. Saturn's moon Titan belongs to a very select club within the solar system. Why just these four? Unlike the inner planets, there isn’t a clear point at which the atmosphere of Jupiter stops, and the liquid interior of the planet begins. Each of the planets has a different atmosphere, although there are clear similarities between the atmospheres of the four terrestrial planets and the four gas giant planets. The gas dwarf is similar in composition to the gas giant planets and only differs in size. There are two main categories of planets: Terrestrial Planets and Gas Giants. When that happened, perhaps within a few hundred million years after the formation of the inner planets, these gases escaped into space, leaving Earth and its three companions little more than balls of rock in space. These planets which were initially categorized as gas giants were established to be distinct in composition as they are primarily made up of carbon, sulfur, oxygen, and nitrogen instead of the hydrogen and helium found in gas giants. Atmospheric transmittance is characterized by the amount of blocked stellar light, here characterized by additional perceived planetary radius (eclipsing height) due to absorption in the atmosphere. Why not also Mercury, or Jupiter's biggest moons, or our own moon? Some types of Terrestrial Planets support life or meet the conditions necessary for terraforming. (Planets not to scale) In general, the surface temperatures decreases with increasing distance from the sun. It is one of only four "terrestrial" planets or moons—those with solid bodies, as opposed to those made largely of gas, like Jupiter and Saturn—that has a substantial atmosphere. So the volcanic activity that long ago died out, for instance, on our similarly sized moon has continued there. Such planets are believed to have a bigger habitable zone than Earth-like watery planets.
Jupiter is the first of the gas giants, and the largest planet in the solar system. While Earth, Mars, and Venus eventually got to the point where they could no longer embrace hydrogen and helium, they did have sufficient gravity and cool enough surface temperatures to retain heavier molecular-weight gases like carbon dioxide and water vapor.