Extraterrestrial life

I cannot imagine any news as exciting and profound as finding extraterrestrial life. If we find it---or should I say when we find it---we will finally have an undisputable proof that we are not alone and indeed our universe may be teeming with life.

In that context, the recent finding of a system of seven planets around a star called Trappist-1, which is “only” 40 light-years away, is quite significant. Three of these planets are orbiting in the so-called “Goldilocks” zone, not too far from the star they are circling to be frozen wasteland, and yet not too close that any water on it would boil and evaporate.  Like, earth, in other words. So, if we assume that water is necessary for any life to exist, and that is not too bad an assumption, there could be life on one or more of these planets. The problem is how can we know one way or another.

For many years, the plan was to listen to the electromagnetic signals coming form space and see if there is a pattern that would indicate that they are being sent by some intelligent creature. After listening for over 50 years (under a program called SETI---Search for Extraterrestrial Intelligence), we haven’t found any such signals. Also, many believe that this is not the way we will detect intelligence. Given how long universe has been around, it is highly unlikely that the extraterrestrial beings, if they exist, are at the same stage of civilization as us. They could be much more advanced, and don’t rely on electromagnetic signals for communications, or much more primitive.

So we need to find other methods. It would be great to send a probe to one of these exoplanets, but the distances are just too great. At 40 light years, it would take that many years for a probe travelling at the speed of light to reach there, and equal number of years to send back signal. That is absolutely minimum amount of time---the actual time would be much greater. We would all be dead by then.

There are stars that are not that far, and in fact a star only 4 light years away, Proxima Centauri, a companion of the more famous Alpha Centauri, has a planet worth examining. A very wealthy Russian entrepreneur is funding a project to investigate the feasibility of sending a series of probes to take a closer look at that planet. These probes would accelerate close to the speed of light using earth-based lasers and “light sails” that catch those beams and accelerate. Such an audacious endeavor is still considered an extremely challenging and expensive. Even for a billionaire.

Instead of going there, one can look at these candidate-for-harboring-life planets from here and see what is going on. Of course, one would need extremely powerful telescopes, like the James Webb Space Telescope currently under construction, and, besides, what would you look at? A very advanced civilization would construct something on a huge scale to, say, harvest energy from the star. Such a structure may be visible from great distances; otherwise we are out of luck. On the other hand, a spectroscopic analysis of these planets’ atmosphere may yield some tantalizing clues, in form of biosignature gases. That alone would not prove that life does exists, but indicate that life could exist.

My feeling is that in the short term, we are better off focusing on finding life closer by---on our fellow planets circling sun or one of their moons. Of the planets, Mars has the highest likelihood of harboring life. Even if nothing is alive now, finding evidence that life did exist in the past would be a great discovery.

Then there is the possibility of finding something currently alive on one of the moons circling Jupiter or Saturn. The two most likely candidates are Enceladus, circling Saturn, or Europa, which orbits Jupiter.

Europa has a crust of frozen water with a high probability of a liquid ocean underneath. Enceladus is similar but has become a more exciting target because Cassini spacecraft orbiting Saturn recently saw icy jets spewing from its surface, much like geysers. That indicates there may be liquid water underneath and hydrothermal vents. This is significant because on earth, hydrothermal vents are an important story in the emergence of life. At many locations in our ocean, scientists have found a whole new ecosystem that is based on energy from these vents and not sun. The same can be true on Enceladus.

To determine if life truly exists on Europa or Enceladus, we may need to drill through the icy surface and peek inside, which is hard to do. However, the icy plumes of Enceladus provide a simpler way. Collecting samples from the plume and testing for building blocks of life may give a strong indication of whether this planet harbors something alive.  Such a test may happen in our lifetimes---NASA is thinking of sending a probe as soon as within the next five years.

So, it is quite likely that we may discover that we are not alone, as soon as in the next few years. How great would that be?