We know for sure that there is life on one planet because we are part of that life but Patrick Moore always says he wonders if there is ‘intelligent’ life even on this planet.
This is really a two part question, question one is, ‘is there life on any of the other planets in our Solar System?’ and question two is, ‘is there life on planets orbiting other stars ?’. Of course this poses the third question, ‘are there planets orbiting other stars ?’
Recently there has been much debate and even arguments over the microscopic ‘fossils’ found in a meteorite from Mars. The jury is still out on that question although it now seems likely that the microscopic worm like objects were not produced by life forms. There has also been a lot of debate about photographic evidence from Mars which appears to show gullies where water may have flowed in the last million or so years and possibly in the much more recent past. A number of orbiters and landers are planned to survey the most interesting sites in the next few years. It is even hoped that samples of the Martian soil can be brought back to Earth for study.
None of the other seven solar system planets can be expected to have or had life because they are either too hot or too cold. Life as we know it needs liquid water which can only exist at a small range of temperatures. Life also needs so sort of energy source like the light and heat from the Sun. However there is the possibility of life on one of Jupiter’s moons called Europa. Space probe surveys have indicated that Europa has a deep layer of liquid salty water under a thick layer of ice. Europa is heated by the enormous gravitational forces of Jupiter which stretches and squashes Europa causing powerful tidal forces. We know for deep sea studies on Earth that life can exist with no Sun light but driven by the heat from volcanic vents called ‘Black Smokers’. Some people even think that life on Earth may have begun around Black Smokers. It is possible that Europa may also have Black Smokers and therefore may also have life in the Great oceans under the ice. NASA has plans to send a probe to Europa to drill through the ice and search for life using a miniature submarine.
But what about other Solar Systems around other stars and could there be life on those planets ? Astronomers have only recently hade telescopes powerful enough to identify planets orbiting other stars and a few have been found. It is not yet possible to see these planets directly because the star is millions of times brighter than any planet and completely drowns out the light from the planet. However large planets have been detected through the wobbling of the star due to the orbiting planets. Nearly all the planets identified so far are large gas planets like Jupiter only larger and orbiting very close to the star. One has been found recently orbiting much further out so there might be smaller rocky Earth like planets further in. Bigger and more sensitive telescopes are planned to look for smaller planets and even to detect Oxygen which can only be maintained in a planet’s atmosphere as a by product of life.
One idea for detecting planets orbiting other stars is to use a number of large telescopes linked together to create a giant interferometer. This works by combining the light from the telescopes so that the light waves from the star are exactly half a wave out of phase. By doing this each set of waves will cancel out the light from the other and the light from the star will disappear. If there is a planet orbiting that star it should now be visible. The Very Large Telescope array in Chile will be the first telescope to put this idea into practice.
So the question is now ‘LIFE WHERE ARE YOU ?