Detecting Earth like planets
With current technology, we really struggle to detect small rocky worlds, currently only a handful have been found, and of those, even smaller number turns out to be within a hospitable zone. This isn't because they don't exist, they just fall below our limits of detection using all the techniques we currently have.
However, with a new group of telescopes coming online this decade, things could change, and that has already began to have an impact on research, not just looking at the old data in new ways (although, that will always be happening), but designing new analysis tools for the new sets of data we are about to get.
The James Webb Telescope will be able to monitor near infra red wavelengths so sensitively, that it can begin to pick out the actual atmosphere of planets as they transit their star.
In the past, we'd only see this as a dip of star light, but with the improved sensitivity, we may be able to also pick up on the actual chemicals in the planet's atmosphere.
Add to that the Nancy Grace Roman Space Telescope, with the ability to be 100 times more detailed than Hubble currently is ! You can see how both working in tandem are going to be bringing datasets we could currently only dream of.
A team at MIT in the United States has already been hard at work trying to work out what to actually look for. You see, terms like "Earth like" don't really help much, but yet we use them in various contexts to mean anything from a similar size in a good spot for liquid water, to a planet just like Earth with lots of life on it. These are very much not the same thing, under the first definition, Venus would be an Earth like planet, at 450'c on the surface and raining sulfuric acid, I beg to differ !
So, the team at MIT began to categorise things to search for in an atmosphere that may be significant. You'll win no awards for guessing Oxygen appeared on their list, but so did CO2, H2 and N2, all things which existed in the Earths early atmosphere, as well as Methane, but the one marker they found which they believe could really identify a biological process (as often geological processes can produce much the same output) was Isoprene (C5H8) which was fairly unique to biological processes here on Earth.
But here strikes the big problem, when we are looking for Earth like planets, we are not looking for life, but, Earth like life ! It's a reasonable assumption, that the only example of life we have can be assumed to hold some form of universal truth, but often this later turns out, like planetary systems, that we are the outlier and everything else is busy look for other things quite unlike us.
Source : https://phys.org/news/2021-04-astronomers-isoprene-atmosphere-alien-world.html
