Scientists have found that detecting a pertinent sign of life on other planets may be more difficult to do from Earth.
Artist's impression of the surface of Proxima b [Image by ESO/M. Kornmesser]
We’re not really in a position to be sending humans to other planets--at least not yet. Having astronauts visit Mars is becoming more and more of a possibility, one that has a high probability of materializing within the next couple of decades. However, the search for alien life has been going on in earnest for a long time, and the inability to travel to other planets won’t stop us.
Thus, we have to rely on methods of remote observation to figure out if a particular planet does host life. The problem, however, is when those signs are difficult to detect or observe from Earth. Right now, scientists detect life on other planets by looking at the presence of certain atmospheric compounds that may be produced by living things. However, a new study has found that certain things may be blocking equipment on Earth from detecting those compounds.
Artist's impression of Proxima b [Image by ESO/M. Kornmesser]
On Earth, living things produce ozone, a compound molecule and an oxygen variety. These molecules rise to the atmosphere and form the ozone layer, which keeps us and all other living things on Earth safe from the sun’s ultraviolet rays. If there is an ozone layer on another planet as well, this may indicate that there is life on the surface, safe from a host star’s potential UV radiation.
Thus, researchers looked at two planets that may be quite similar to Earth: Proxima b and TRAPPIST-1d. Both planets are not only possibly Earth-like, but they also orbit within the habitable zone of their host stars, which are both red dwarfs. Proxima b orbits Proxima Centauri, the closest star to our sun, while TRAPPIST-1d is part of the fascinating family of planets that orbit the star TRAPPIST-1.
While these tidbits of information are promising, researchers have also found some discouraging things about the planets. The planets orbit their stars in just 25 days or less, and they are tidally locked to stars. This means that one side of the planets perpetually faces their host, with one planetary side perpetually in day and the other in night.
This tidal locking, according to researchers has caused an interesting effect in the ozone of the planets. The planets’ airflow may go from the poles to the equator, thus causing all the ozone to gather in the equatorial region.
Artist's impression of TRAPPIST-1d [Image by NASA/JPL-Caltech]
This is a problem for observers on Earth. If all the ozone in these planets is concentrated on the equator, we would not be able to observe it from here. However, the researchers are trying to stay optimistic. "Absence of traces of ozone in future observations does not have to mean there is no oxygen at all,” says lead researcher Ludmila Carone. “It might be found in different places than on Earth, or it might be very well hidden."
If these planets do have their ozone layer concentrated around their equator, this means that the rest of the planet is unprotected from the host stars’ UV rays, which are potentially harmful to living things.
"We all knew from the beginning that the hunt for alien life will be a challenge," Carone said. "As it turns out, we are only just scratching the surface of how difficult it really will be."
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