Galactic Neighbours

A recent article in the National Geographic magazine about aliens rekindled my interest in the hunt for extraterrestrial life. This topic will always be interesting especially for those who follow space technology and space exploration. Mankind will always be curious to know if he has any neighbors intelligent or otherwise.

The hunt for aliens is not new. Man has been curious about extraterrestrial life since the time he discovered space. Ground based telescopes were the  main weapons in this hunt till the end of the last century. Powerful as they are, they sit beneath layers of earth’s atmosphere. Dust particles, clouds, limit their capability. However all that changed with the launch of the Kepler spacecraft by NASA. This craft carried a telescope which is stationed in space. Thus all the clutter of earth’s atmosphere has been done away with. Since its launch in March 2009 the telescope has helped to discover more than 2000 planets orbiting their stars. Kepler will be replaced by the more powerful and advanced James Webb telescope.

The process of hunting for intelligent life got a boost when SETI (Search for Extra Terrestrial Intelligence)  program was started exclusively to hunt for aliens. Various universities and institutions launched SETI programs. But funding has always been an issue and recently NASA was instructed by the Congress to distance itself from SETI and not use valuable funds to search for the so called ‘ little green people’. But SETI is here to stay and would continue its work, funds or no funds.

The aim is to look for planets in the so called ‘Goldilocks’ zone meaning the planets are at the right distance from their sun to nurture life. Too close and they will be too hot to support life, too far away and they will be too cold.

Some conditions need to be satisfied if life is to thrive on any planet. Apart from the distance from its sun which is crucial, scientists say, a process known as abiogenesis has to happen. The chemicals which are needed for life to sustain should be available in the right proportions. I remember the episode of Cosmos in which Carl Sagan stands next to a vessel which contains some murky liquid. He says that the liquid has all the elements or chemicals needed to start life. The essential chemicals are there, but life has not started in the vessel. Abiogenesis is what makes life happen.

That brings us to the next condition, that of time. Life as we know it on earth has taken millions of years to evolve. The ideal conditions have to prevail for that time. Any break means the process of evolution goes back to zero. An interesting observation here is that the distances in space are huge. Light sometimes takes thousands or even million years to reach us from faraway stars or planets. So when we observe distant stars or planets we are essentially looking into their past. There is a possibility that by the time light from a distant planet reaches us, life on it may have evolved further.  

Also the life has to be intelligent enough. They must have evolved enough to have technology which helps them to communicate. For egg. If they have discovered radio waves so much the better. It would indeed be difficult to find a colony of single celled amoebas on some planet say, 50 light years away. Finding a less evolved civilization would be very difficult  but may be not impossible.  

New technology could have a solution to the above problem as well. New sensors on spacecraft slated to be launched in the next decade will be advanced enough to look for telltale signatures of specific gases. As we know, living creatures on earth give out various gases like carbon dioxide, oxygen, methane etc. The advanced sensors will look for these gases in atmospheres surrounding distant planets. These observations will give astronomers vital clues regarding presence of life.    

Scientists are also facing another big hurdle in this endeavor. The sheer number of star systems out there. There are millions of suns with many more millions of planets around them. Then there are planets which are drifters. They are not attached to any star system. Finding life would be like looking for a  needle in a haystack. Only this haystack is really huge.

As we look into the future, the hunt for aliens can only get more interesting. That there is life out there somewhere, is now a given. The odds are stacked against we being alone in the known universe. The scope of this search is increasing exponentially as technology gets more advanced. We just have to keep looking to learn who our neighbors are. Finding them will change us for ever.