Terrestrial planet from the original solar nebula. The Solar System has four terrestrial planets: Mercury, Venus, Earth, and Mars. Only one terrestrial planet, Earth, is known to have an active hydrosphere. During the formation of the Solar System, there were probably many more terrestrial planetesimals, but most merged with or were ejected by the four terrestrial planets. Dwarf planets, such as Ceres, Pluto and Eris, and small Solar System bodies are similar to terrestrial planets in the fact that they do have a solid surface, but are, on average, composed of more icy materials (Ceres, Pluto and Eris have densities of 2.17,
Solar hot water in Australia rebates are offered at the present, however the Queensland government in 2007 announced the phasing-out of electric hot water systems commencing in 2010. From 2010, Queenslanders who need to replace their household hot water system due to breakdown will no longer be able to install electric systems, and will instead have to choose from gas, solar or heat pump options. Prior to this, the Queensland government had already banned the installation of electric hot water systems in newly constructed houses; a law which came into effect on 1 March 2006. The ban on electric hot water systems was repealed on