Could There be Hydrogen Breathing Aliens?
To date over 4000 known exoplanets have been discovered. Finding these is a first step to identifying potentially habitable worlds and so where the search for extra-terrestrial life begins.
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If you are looking for life outside our solar system, it makes sense to try and identify worlds similar to our own. After all, we know that life can develop on Earth, so looking for Earth like planets gives us the best chance of finding life that is similar to us elsewhere. Or does it?
Detecting exoplanets
NASA’s K2 spacecraft and its predecessor Kepler have founds thousands of these potential homes for life. Although within The Milky Way, they tend to be many hundreds of light years away and so it is unlikely that we will visit them any time soon, or that any extraterrestrial life will make it here either.
“Right now we know, for the first time, that small planets are very common”
But as Sara Seager, a professor at the Massachusetts Institute of Technology and an exoplanet research pioneer has said, “Right now we know, for the first time, that small planets are very common.” So, while there is little chance of paying a visit, further study of these many exoplanets might find evidence of life and that would be a profound discovery.
Planets are found in a number of ways, a method by which many have been detected is by observing them traversing the star that they are orbiting. And by measuring the length and the frequency of the orbit, estimations can be made about the size of the planet and its distance from its parent star.
The transit method also allows scientists to discover the composition of the planet’s atmosphere by analyzing the light that passes through it. This spectral analysis has led to the discovery of among, other things, water vapor and methane, both potential signs of life.
But for life as we know it to exist elsewhere water is not the only prerequisite. The life that we know about on our own planet also requires an atmosphere rich in oxygen.
But there is also the possibility of life that is not like that on Earth.
What about hydrogen?
A new paper in Nature Astronomy argues that we should broaden the search from planets that have atmospheres similar to our own and include those that have an atmosphere rich in hydrogen.
Hydrogen is the lightest of gases and so escapes easily from the atmosphere. So for a planet to be able to maintain a hydrogen atmosphere it would have to be much more massive than the Earth — between two and ten times as big.
It could also be further away from its home star as, although the further way it is from its source of energy the colder it will tend to be, the greenhouse effect of a hydrogen atmosphere would keep the planet warmer than an oxygen rich atmosphere.
Both of these factors increase the number of prospective planets.
On Earth it is know that micro-organisms can live in a hydrogen rich environment, so the concept of hydrogen breathing life is entirely feasible.
Finding signs of life of any variety is going to be tricky and taking these new ideas into account may mean that the number of candidate planets for life could double. So NASA has its work cut out.
Reference
Seager, S., Huang, J., Petkowski, J.J. et al. Laboratory studies on the viability of life in H 2-dominated exoplanet atmospheres. Nat Astron (2020). https://doi.org/10.1038/s41550-020-1069-4
Originally published at http://mralanjones.blogspot.com.
