...and, no, it's not from a crashed flying saucer.

https://www.bbc.com/news/articles/c39jj9vkr34o
https://en.wikipedia.org/wiki/K2-18b

Someday -- possibly soon -- we will have solid evidence for life elsewhere in our galaxy, and this is how it will likely happen. An alien craft won't land in the White House lawn. And it probably won't be a repeating radio signal that could only have an intelligent source.

Instead, astronomers will announce the evidence for hydrogen and, possibly, water vapor in the atmosphere of yet another exoplanet. There will be a debate over whether this was a good signal, or maybe it contained noise from the host star's solar activity. Page 8 news.

Later, a different instrument confirms water vapor and adds other interesting gases, such as methane and carbon dioxide. Discussion picks up. Given the planet's size and distance from its star, could it have an ocean? Is it more likely a gas giant, with a thick atmosphere? Would liquid water (essential for life as we know it) only exist at depth, perhaps under a thick layer of ice? Is the planet tidally locked to its star, with a boiling sunny side and frozen night side? Could life survive the UV and X-ray radiation so close to a red dwarf star? Page 3 news.

Then, another look reveals the presence of biomarkers -- compounds that are almost always produced biologically. This is where we are now with K2-18b. The news in the last 24 hours is that dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) have been detected in K2-18b's atmosphere. On Earth, DMS and DMDS are only produced naturally by phytoplankton and bacteria. We know DMS *can* be produced in other ways, since it has also been detected in at least one comet. But comets are frozen relics from the formation of a solar system. In the warmth of K2-18b's atmosphere (very similar to Earth's temperature), DMS and DMDS are unstable. That they are in detectable quantities means that something is actively producing them. The debate now is, other than life...what?

Stay tuned.