Are we close to discovering extraterrestrial life?
I'll start with the take-home message: I'm 50, and I fully expect the issue to be settled in my lifetime, with evidence regarded as conclusive by an overwhelming majority of scientists.
There are three good candidates:
- The James Webb telescope should be able to image exoplanets in enough detail to say whether they have atmospheres, and at least for the closer planets, tell whether they have atmospheres with the type of chemical imbalance that can, as far as we know, only be sustained by life. The molecular oxygen in Earth's atmosphere is such an imbalance; if all life went extinct, the oxygen would disappear on the timescale of 10,000 to 100,000 years (meaning that if we saw such an exoplanet, it is very probably full of life, with a low possibility that it was full of life until relatively recently). I expect this to happen inside a decade, two on the outside.
- Mars. It seems overwhelmingly likely that there will be a human mission to Mars inside 20 to 30 years; if there is or ever was life on Mars, the expedition is very likely to find out, as it will be a top priority.
- Enceladus or Europa. Missions to find life are still on the drawing board, but with recent discoveries about Enceladus' geysers, I would be very surprised if there wasn't a mission in 10 to 20 years. The thing there is that sampling the geysers is a piece of cake, relatively speaking: they spew water into space, all you have to do is to fly by with a scoop to collect it. If there's life in that water, it will be found.
Also, there should be an successor to the James Webb in orbit before I hand in my final notice; it will be able to look further and in more detail.
Then there are the "out of left field" possibilities; detection of an alien signal tops that list. Unlikely, but so well worth the effort that we'd be morons not to listen. I'm also all for investigating whether there's ever been any actual visit to Earth by aliens, Däniken-style; I consider it unlikely in the extreme, but hey, no harm in looking and we'll probably find out interesting archaeological things in the meanwhile.
TRAPPIST-1 planetary system
I saw that article when it first appeared, and I was appropriately blown away. But you have to remember that none of those amazing illustrations are photographs. The planets are much too far away for our best telescopes to see them in any amount of detail. What they see are moving dots. The pictures are imaginative depictions of what they might look like up close, based on pretty scanty data.
We're finding a growing number of planets that might support life, based on their size, their distance from the stars they orbit, and the nature of the stars themselves. That's pretty much all we know about them. It's going to a be a while yet before we can find out more, and as far as going there to see for ourselves, that's not even on the horizon because of the vast distances involved.
Our best bet for finding extraterrestrial life is right here in the solar system, and I don't expect it to be anything more than microbial. But that could happen fairly soon.
Maybe. Maybe not. But what difference will it make? If there were little green men in the solar system, wouldn't we have noticed them? Maybe that would change our perception. Microbes on other planets, eg Mars, possibly but why don't we just talk to the bacteria on Earth; it would gain just as valid an insight.
Alien civilisations elsewhere in the galaxy? Just saying ‘hello' is going to take four years to A. Centauri and another 4 years to get an answer; no doubt ‘hello'. Unless someone comes up with a way of transmitting messages way faster than the speed of light, we are always, effectively, going to be alone in the universe. The closest galaxy to us, moving on a collision course, is 2.5 billion years away from our greeting. We would be extinct before ever the reply came through!
We look for ‘evidence' because we, as a species, must. It is why we have perpetually ‘looked for' gods; alien civilizations merely satisfy that need in a different way. We cannot deal with the repercussions of our own consciousness!
Unfortunately we are looking for a needle in a haystack the size of Wales. I have participated in the SETI@Home programme, allowing spare CPU capacity of my PC to be used for processing raw data from SETI, but am well aware that any possible positive results might take decades or centuries to achieve.
Nevertheless, the fact that we are looking says much about us as a species, our positive outlook, inquisitive nature, determination and scientific tenacity. The greatest achievements in history were won at the cost of years of toil, sometimes the best part of a person's life.
Our ability to image extra-solar planets seems to be increasing almost weekly. Just a couple of years ago, we could only "infer" the presence of planets by the periodic dimming of the star as planets orbited it.
Now, we are able to tell more and more about these planets, and that will increase as more and better instruments go online. One potent indicator would be if we found free oxygen in the atmosphere of an extrasolar planet.
As far as we know, this is a potent indicator of life, if only plant life.