Underrated Ideas in Biotech (#8) Or, how to terraform Mars using genetically-engineered microbes. Mars is an inhospitable planet, located about seven months away by rocketship. It is drier than almost any environment on Earth and has exceedingly "low pressure, freezing temperatures, and high salt concentrations," according to an @AsimovPress article by @StorkDevon. But if we could engineer a microbe to survive on the planet, we could wait for that microbe to divide and then use it to create greenhouse gases that warm the planet, make oxygen for humans to breathe, and even exploit soil nitrates to thicken the atmosphere. Such a microbe would make it far easier for humans to live on Mars. This is not a new idea, but using modern biotech tools to actually do it probably is. There are zero known microbes on Earth that could survive on Mars. This is because, on Mars, they'd have to contend with five major challenges simultaneously: Extreme radiation, a high level of toxins (2 ppb perchlorate is toxic to humans; water on Mars is likely salty brine with perchlorate concentrations of 15-50%), freezing temperatures, lack of atmosphere and a lack of bioavailable water. On Earth, species usually evolve ways to deal with one or two of these, but not all of them at the same time. Bioavailable water is the biggest bottleneck here. Mars is a desiccant; it sucks moisture out of things. "If one dumped an entire lake onto Mars, some of the water would evaporate in the low-pressure atmosphere and condense at the frigid poles. Mars’ salty soil would absorb the rest, binding the water molecules tightly enough that they would be unable to evaporate," Stork writes. "The lower limit of water activity for existing lifeforms is 0.585. This record is held by Aspergillus penicillioides, a fungus that can live upon dust...All liquid water on Mars has a water activity below 0.5. There are no known lifeforms that could survive in this water, as the high salt concentration would quickly suck the liquid out of cells." Pioneer Labs, a nonprofit research group, is trying to engineer a microbe that could survive on Mars. They are doing this by taking microbes from Earth and evolving them to withstand more extreme environments. For example: They took some E. coli and put them in increasingly salty liquids. The cells naturally mutated and, after 1 month of selections, could withstand 2-3% higher salt concentrations than baseline. One could also evolve cells by engineering them with thousands of different genes and then using large assays to figure out which confer a useful phenotype or, perhaps, by using AI to design new genes. At some point, though, Pioneer Labs will need to figure out solutions to each bottleneck I've mentioned and then aggregate those traits, or genes, or mechanisms, into a single microbe. Even if they don't succeed, they are publishing a ton of useful basic research about how life adapts to new environments. It's worth following their blog online.