@Scott: Cell membranes serve to keep the components of an organism together. Hi Paul Once an area is covered in ice, the high reflectivity of ice tends to keep it that way. On Titan, I doubt whether they freeze seasonally at all — if methane ice occurred anywhere, you’d expect it at the north and south poles, but they are exactly where those big liquid lakes are found. similar manner to methanogenesis: The overall reaction for respiration, where hydrogen is inhaled and methane Abstract available. gives you respiration. in Biology 0 A new type of methane-based, oxygen-free life form that can metabolize and reproduce similar to life on Earth has been modeled by a team of Cornell University researchers. REU��΄2��7�ifF�e Questions to answer 1. So which is really the better gas for intelligent life forms? That makes hydrogen only ten times better, per atmospheric weight fraction, at energy delivery. My guess is that most hydrocarbon free radicals should have a low enough dipole moment to dissolve, and peroxides seem a decent guess as to the sort of chemicals that might be involved in generating them in intermediate metabolism. Methane-ethane based life would operate at approximately -160° C. The primary solvent would be a mixture of methane, CH4 , and ethane, C2H6. With an average surface temperature of a brisk -297 degrees Fahrenheit (about 90 kelvins) and a diameter just less than half of Earth’s, Titan boasts methane clouds and fog, as well as rainstorms and plentiful lakes of liquid methane. McKay’s work suggests that such active M-dwarfs would dissociate atmospheric molecules on a Titan-like world, making the place more and more smoggy and reducing the surface temperature. Water has some properties that make it an ideal solvent for life, so it seems amazingly coincidental that it is the most common accessible liquid medium in our universe (metallic and liquid molecular hydrogen seem inaccessible to me). reducing environment can therefore be summed up on one equation: where reading to the right gives you photosynthesis and reading to the left Its great abilities as a solvent, high heat capacity and wide temperature range seem indisputably useful. is the light in the image from a long exposure ( is it really a lot darker)? It would be hard for life – as we know it – to begin in an environment where seasonal changes are as severe as a change of state of the environment. If you were a writer of very hard science fiction, it would still be allowable to have our first astronauts to that moon greeted by a large enthusiastic group of natives. FrankH suggested that life on Titan could be mistaken for a rock… %PDF-1.5 3 Possible answers include: Mosquitoes carry diseases such as malaria, Murray Valley encephalitis and Ross River Virus. Does this open the possibility of a photosynthetically driven biosphere, of which the hydrogen absorption only represents a small proportion to the biological activity? If so the high availability of this powerful oxidant in the local food would absolve us of the need for metabolic rates to be limited by hydrogen uptake. I bugs me that above I wrote that “If you were a writer of very hard science fiction, it would still be allowable to have our first astronauts to that moon greeted by a large enthusiastic group of natives”, yet the likely surface hydrogen concentration, as indicated by that reverse hydrogen flow data should only be about 0.5%. What I’m really interested in is whether there is any chance that methane-based multicellular life could exist. At normal levels they are necessary for life because they trap heat and keep Earth the perfect temperature for living things. Firstly, in anaerobic metabolism on Earth, hydrogen is rare, and so the difference in energy available to organisms of aerobic v anaerobic metabolism here is very great. Sulfur compounds are a waste product for some organisms on Earth. q��T�cx�rD�E��-�K�Y���f� To remove this guilt by association, I note that reducing formaldehyde (I’m unsure what carbohydrate extraterrestrial biochemistry will utilise, and methanal is the simplest carbohydrate with the most data) with hydrogen releases fully a third the power of its oxidation with oxygen. That makes future probes of Titan all the more interesting, and adds to the desirability of a long-term presence on the moon, either through a surface rover or an aerostat that could range high over the surface and give us a highly-focused look. Release of the methane gas 9. Free interactive exercises to practice online or download as pdf to print. I would suggest that scientific precision in the use of these terms to express what one actually means is always helpful in aiding communication. �J�]��Ҩ����"�D.�H�~�DYHv�A����J*�k���9���+�9/A������ҧ,�SbpLx���-*q�k��ޓY[�� v`^W�(|cVm�#��"㚎����:>���&�;�v=�ڡ��c3�.E�߂���l� and catalytic flexibility of proteins, It’s intriguing, of course, that with methane we get the ‘triple point’ that allows a material to exist in liquid, solid or gaseous form at a particular temperature and pressure. �ԅ�w��?�YV��`1�� Perhaps then, we can still entertain the possibility of being greeted with wild enthusiasm. 2 0 obj But the fact that Titan does show signs of such depletion isn’t necessarily indicative of life, for these signs are themselves dependent on atmospheric models that are still in play, and in any case we know little about other processes that could mimic the same characteristics without implications for life.