With an eye to the eventual greening of Mars, Scientists in Mexico are examining Pine trees living on the side of a volcano to see how they cope with the adverse conditions. The snow-capped Pico de Orizaba is not only a dormant volcano but also Mexico's tallest mountain, so the Trees that cling to the side are a hardy breed. Learning how they survive may give clues as to how to one day cultivate plants on Mars, but first we'll need to warm the planet up. Scientist Rafael Navarro-Gonzalez of Mexico City's UNAM University thinks the idea is not necessarily the stuff of science fiction. Global warming here on Earth gives a clue to the process required. If we can introduce highly insulating gases like methane or nitrous oxide in sufficient volume, we could heat Mars. If we can raise the temperature to 41 degrees Fahrenheit from the present minus 67 F, this would match temperatures where trees grow at 13,780 feet on Pico de Orizaba. NASA scientist Chris McKay believes we might see Trees on Mars within 100 years, and sees them as a vital component of any terraforming effort, since Trees are the major "engines of the biosphere."