What is the thickness of the biosphere?

Question

In other words, what is the vertical distance between the deepest and highest point on Earth where life is found? Life has been discovered at the [bottom of the Mariana Trench](https://www.smithsonianmag.com/science-nature/nearly-8-miles-down-bacteria-thrive-in-the-oceans-deepest-trench-3298109/), 13 km below sea level. It's hard to get deeper than this, but I'm not sure if this really represents the bottom of the biosphere. Elsewhere at sea, microbes can be found [many kilometers below the sea floor](http://sciencenordic.com/live-bacteria-found-deep-below-seabed) -- would we expect to find life far below the Mariana Trench? In the other direction, the biosphere arguably reaches as high as 435 km, the maximum altitude of the International Space Station. If the ISS is disqualified, then that number would be much lower, but again I'm not sure exactly what it would be. The [highest recorded bird flight](https://sora.unm.edu/sites/default/files/journals/wilson/v086n04/p0461-p0462.pdf) clocks in at 11 km, though it's possible that microbes regularly get dragged up higher than this by wind.

Answer 1

I've done some research, and it definitely seems like the Marianas trench is the place deepest into the Earth that any life is known to live--I found a couple more sources besides yours that talk about bacteria ~2 miles below the surface (sources 1 and 2), but nothing about anything else as deep as the Trench. Your source indicates that the Trench bacteria are absolutely thriving, rather than barely hanging onto survival; that makes me think that there could easily be even more extremely thermophilic bacteria deep in the substrate at the bottom of the Trench. Perhaps someone will explore those depths in the future.

Furthermore, my research indicates that bacteria have been found abundantly as high up as ~6.2 km/10 miles (sources 3 and 4), and it's been theorized that they could live as high up as 50 km/30 miles (source 5). So the highest bird flight is definitely not the limit of the biosphere!

Bacteria seem to be the ultimate extremophiles of our planet, always found where nothing else can live. I hope that future research will reveal how high and how deep they can live, and I would be unsurprised if it was higher and deeper that we could ever have conceived.

Sources:

1. https://www.universetoday.com/851/bacteria-found-deep-underground/
2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC43253/
3. https://www.nature.com/news/high-flying-bacteria-spark-interest-in-possible-climate-effects-1.12310
4. https://www.latimes.com/science/la-xpm-2013-jan-28-la-sci-bacteria-in-the-atmosphere-20130129-story.html
5. https://www.livescience.com/41173-sky-high-microbes-how-far-up-can-life-exist.html