Is there anybody out there?
The question of whether or not there is another life or even intelligent life in the universe is one of the most fundamental questions that we can ask ourselves. It is also one that we might be able to answer in our lifetime, thanks to advances in astronomy and technology. Currently, we are trying to answer the question from two angles:
Can we find microbial or simple lifeforms in our solar system? This includes places like Mars, Europa, and Enceladus, which have all been shown to have the potential to support life.
Can we detect biosignatures in exoplanets? Biosignatures are chemical or physical signs of life, and they can be detected in the atmospheres of exoplanets.
For the former, this search involves a painstaking and comprehensive step-by-step approach to the environments in our solar system that might be habitable today (e.g., Mars, Europa, or Enceladus) or in the past (e.g., Mars), and look for tell-tale signs of microbial or simple life, be they biosignatures or direct imaging (fossils). The pace of progress here is significantly constrained by the challenges of sending robotic probes through interplanetary space, the vast distances these probes have to cross, and the high costs associated with each mission. The Mars Sample Return is a case in point. In other words, progress is slow.
For the latter, it is more of a numbers game. Once new earth or space-based telescopes are up and running, say the James Webb Space Telescope or future very large Earth-based observatories (see post on Feb 1, 2022), they can search for biosignatures in distant atmospheres within a relatively short space of time. So, if I had to give my 2 cents, I'd say that the likelihood of finding biosignatures on exoplanets in the coming decade is greater than finding biosignatures in our solar system.
But there is a school of thought that recommends ditching the whole bio-signature search altogether to focus instead entirely on technosignatures, the scientific evidence of past or present technology.
There are a few reasons why searching for technosignatures is considered to be better than searching for biosignatures for finding life in outer space.
Technosignatures are more unambiguous. Biosignatures can be ambiguous, as they can be produced by non-biological processes. For example, methane is a biosignature, but it can also be produced by non-biological processes such as volcanic activity. Technosignatures, on the other hand, are much more likely to be produced by intelligent life. For example, a signal from a radio telescope or a laser beam would be a clear indication of intelligent life.
Technosignatures are easier to detect. Biosignatures are often very faint and difficult to detect. For example, the presence of oxygen in a planet's atmosphere is a biosignature, but it is very difficult to measure the amount of oxygen in a distant planet's atmosphere. Technosignatures, on the other hand, can be much more powerful and easier to detect. For example, a radio signal from a distant civilization could be detected by a relatively small telescope.
Technosignatures are more likely to persist. Biosignatures can be destroyed by natural processes, such as asteroid impacts or volcanic eruptions. Technosignatures, on the other hand, are more likely to persist for long periods. For example, a radio signal from a distant civilization could continue to be detected for billions of years.
Technosignatures will be amplified by multiple sources. Given how we view our technological progress, it makes sense to believe that once an alien species has reached a technological threshold, they or their technology will expand in their solar system and beyond, implying that a single technologically advanced species, while potentially far rarer than simple lifeforms, will have a larger footprint overall. In other words, even if these events are extremely rare, they only have to occur once to be easily detectable.
In addition to the reasons mentioned above, searching for technosignatures can also tell us more about the nature of intelligent life. For example, if we were to detect a radio signal from a distant civilization, we could learn about their technology, their culture, and their values. This information could help us to better understand our place in the universe and our relationship with other intelligent beings.
This is an interesting take on the search for life in our solar system, which of course brings us back to Fermi's paradox: 'If there are technologically advanced aliens out there, then where is everybody?'
Whoever is right though, there is no doubt that the search for extraterrestrial life is picking up pace. What are your thoughts on this topic? I'd love to hear them.
As always, onwards and upwards