Half an hour away from our hotel, we realized we had taken with us the key to another car which our colleagues needed. So, we turned around to return the key. During the hour that followed, driving over familiar roads, we discussed the scientific story that is emerging here.
Part of our purpose in making this trip was to look for hypoliths, which are stones colonized on their undersides by cyanobacteria. It turns out that the Emirates aren’t good hypolith territory. There is too much sand, and not enough of the right kind of stones. We haven’t seen any, except a few very small ones near Jebel Hafeet.
But the salt-loving bacteria that live in the sabkhas here are excellent and interesting. We humans can drink water that is only about 1/10th as salty as seawater, but seawater itself still feels “fresh” to some of these bacteria. They can live in water that is a lot saltier than seawater.
The sabkhas have groundwater a few feet underneath them that is probably fairly fresh. It appears that the groundwater wicks upwards and evaporates at the ground surface, leaving behind layers of salt crust and brine. In the top layers, cyanobacteria and halophilic bacteria thrive, protected from ultraviolet light and from drying out by the top centimeter of salt crust. The translucent salt crust acts like a greenhouse window.
The pink halophilic bacteria grow in the uppermost layer, with the green algae and cyanobacteria just below them. Lower down there is a dark layer of bacteria.
Mars probably has salt flats like this. Nothing can live on the surface of Mars because of the harsh ultraviolet light. But, a centimeter of salt crust is all it takes to block the ultraviolet light, while allowing plenty of visible light to be transmitted. So, this kind of environment is a good place to look for life on Mars.
None of this makes good photographs, so enjoy the photos I am putting here of us (with Annie at the wheel, as always) stuck in a camel herd.