 In what environments is life believed to have emerged? Well, there are several ways to get at this question. One way is to look at phylogenetic trees. And this guy, Carl Woes, discovered the archaea in 1997, and with this technique of genetic sequencing, you can make trees like this in which the luca, the last universal common ancestor, the root of the tree of life, is hyperthermophilic. So, basically, you have hyperthermophiles at the base, then you have thermophiles, then you have mesophiles like us. And we are eukaryotes, and we don't like showers hotter than about 55 or 60 degrees. But these, the root of the tree of life, looks like they loved 90 or 100 degrees. Now, the two candidates for where life could have formed and emerged and be compatible with this thermophily is hydrothermal vents at spreading centers at the bottom of the ocean or at hot springs like Yellowstone hot springs in which you have very hot water coming up. And these are all bacteria that we're talking about. So, in hydrothermal vents, to have a closer look at where they are, they're all about these red dots. And they're the spreading centers where the plates are coming apart. And here's an example of some of the complex redox chemistry of 350 degrees centigrade water turning into 2 degrees centigrade. And that quick cooling provides a lot of energy. We call it redox energy for life forms that might be able to take advantage of it. Leads to all kinds of black smokers and white smokers where we think a pH gradient drives life. I should notice that at these hydrothermal vents, there is no UV radiation. There's no air. It's just water and rock. The other alternative scenario for the environment where life could have gotten started is in hot springs. They are at the surface. There you have sunshine. There's a picture. Here's a road just for scale. But it's on the surface and notice that there's air on top of this stuff. And that's not the same as for hydrothermal vents. There's no air down there. It's a little like Darwin's Warm Little Pond with UV. Here's a diagram of what we think. We think that the synthesis of life here. And then here's a whole diagram here in which life through wet and dry cycles can maybe create something useful inside of what they call gels and proto genotes. That's the hot spring model. Fresh water, not salt water. And wet and dry by evaporation, not by tides. And there's UV for this to drive this. So those two scenarios, there are two camps now. They're fighting with each other and maybe they should cooperate a little bit more. But maybe we'll find out some other new regime. But currently in 2021, those are the two scenarios where we think the two environments that are the best candidates we have so far for the origin of life.