<P> Another way to create a Martian atmosphere would be to import methane or other hydrocarbons, which are common in Titan's atmosphere and on its surface; the methane could be vented into the atmosphere where it would act to compound the greenhouse effect . </P> <P> Because long - term climate stability would be required for sustaining a human population, the use of especially powerful fluorine - bearing greenhouse gases, possibly including sulfur hexafluoride or halocarbons such as chlorofluorocarbons (or CFCs) and perfluorocarbons (or PFCs), has been suggested . These gases are proposed for introduction because they produce a greenhouse effect many times stronger than that of CO . This can conceivably be done by sending rockets with payloads of compressed CFCs on collision courses with Mars . When the rockets crash onto the surface they would release their payloads into the atmosphere . A steady barrage of these "CFC rockets" would need to be sustained for a little over a decade while Mars changes chemically and becomes warmer . However, their lifetime due to photolysis would require an annual replenishing of 170 kilotons, and they would destroy any ozone layer . </P> <P> In order to sublimate the south polar CO glaciers, Mars would require the introduction of approximately 0.3 microbars of CFCs into Mars's atmosphere . This is equivalent to a mass of approximately 39 million metric tons . This is about three times the amount of CFC manufactured on Earth from 1972 to 1992 (when CFC production was banned by international treaty). Mineralogical surveys of Mars estimate the elemental presence of fluorine in the bulk composition of Mars at 32 ppm by mass vs. 19.4 ppm for the Earth . </P> <P> A proposal to mine fluorine - containing minerals as a source of CFCs and PFCs is supported by the belief that because these minerals are expected to be at least as common on Mars as on Earth, this process could sustain the production of sufficient quantities of optimal greenhouse compounds (CF SCF, CF OCF OCF, CF SCF SCF, CF OCF NFCF, C F N) to maintain Mars at' comfortable' temperatures, as a method of maintaining an Earth - like atmosphere produced previously by some other means . </P>

Name two major ways in which earth is unlike any other planet