Article on the discovery of 51 Pegasi b, 20 years (!) ago

Short of getting a radio signal with video proof (that couldn't have been faked on Earth) sent from the exoplanet, I don't think there's a way to be 100% sure of any alien life on any exoplanet.

If it would take way too long to send an actual probe, it's all guessing.

On Friday, November 18th, 2016 at 6:31 pm, KarmaJolt said:

We can - at least theoretically - interfer a fair bit of information about an exoplanet. And what is possible with current technology is not going to be the final word on the issue. I actually expect that in the future, we'll have reasonably good estimates on bulk properties of exoplanets and, if we're being lucky, atmospheric composition. As I said, atmospheric composition is a possible indicator for the makeup of a planet. The problem is that for planets that are more massive than Earth, and less massive than say, Neptune, you have a broad range of overlap for different planet types, inculding:

- 'gas giants' (more accurate would be 'fluid giant', the big point is that Neptune and Uranus have an interior of fluids, or 'ice', surrounded by an envelope of gas, whereas the gas giants proper like Jupiter and Saturn have a mantle of metallic, high pressure hydrogen).

- 'water planets' (rocky or metallic core, surrounded by a rocky mantle, surrounded by a very deep, planet-wide ocean, with the deeper parts possibly consisting of exotic high-pressure types of ice).

- failed gas giants with an envelope of helium (and little or no hydrogen).

- carbon planets (planets that have more carbon than oxygen, which would yield a geochemistry dominated by silico-carbides as opposed to silicon oxides as on Earth. These planets would be super-rich in hydrocarbons but bereft of liquid water due to the scarcity of oxygen).

- actual earth analogues (with a metallic core and a rocky mantle), but substantially larger than earth.

Unless we have more data, many planets discovered so far that are significantly more massive than Earth (say, five to ten times its mass) could fall in any one of these cathegories.

Yes indeed, Doitsujin, we could tell a lot about exoplanets from analyzing the atmospheric elemental signatures - but that's assuming we can do that accurately. We can get a much better picture using the Kepler than we can from, say, ground equipment.

I'm no expert in this but it's my understanding that we can't get a really good spectrum analysis of exoplanets right now. It's too hard to differentiate light from its respective star.

As technology gets better, I would imagine some kind of high resolution, advanced form of radio imaging to take off and even be able to view extremely distant objects in high detail.

Unless we figure out how to create wormholes or travel faster than the speed of light (which is impossible without an infinite amount of energy), actually visiting or migrating to other Earth-like planets (or any exoplanets) is impossible within a reasonable amount of time.

I'm of the belief that, long-term, humans will be more likely to terraform sections of Mars or build moon bases if we need to leave Earth as a species. As disturbing as it seems, we are stuck on Earth (at least in terms of where we can live and grow food) for the foreseeable future.

If we were to migrate to an Earth-like exoplanet, we would not only have to be 100% positive that humans could survive on it but we would have to figure out how to survive for thousands of years aboard a migration ship. In this case, humans would be more likely to live aboard space colonies instead of other planets.