Colin Dundas from the Astrogeology Science Center in Flagstaff, Arizona, and colleagues reported in a recent issue of the journal Science their discovery of huge ice cliffs on Mars. The cliffs seem to consist of nearly pure water ice, which is believed to have been deposited by snowfall during periods in the past when the Martian axis was more tilted toward Earth. Dundas thinks the snow later compacted into the massive layered and fractured ice sheets we see today.
Some of the ice cliffs have an astounding thickness of more than 100 meters, and are close to the surface—just one or two meters deep—which makes them, in principle, accessible using today’s lander and rover technology. The European Space Agency’s ExoMars rover, for example, which is scheduled to launch in 2020, has a drill that should be able to reach the deposits.
One problem, however: The reported ice cliffs are located at about 55 degrees latitude, which is above the 50-degree line normally set as a limit for NASA or ESA missions that rely on solar power. But the science team led by Dundas thinks there may be other ice-rich deposits at lower-latitude sites, such as Arcadia or Utopia Planitia.
Getting a sample from these ice cliffs would have tremendous potential for astrobiology. First, we would get scientific insight into environmental conditions during a time in the Martian past when the climate was more benign and there was relatively frequent precipitation. If life was present during those times at those locations, it should be nicely frozen in place. The handling of such a preserved sample would be easy—you would only have to melt it and analyze the contents in a watery solution, something we do in laboratories on Earth millions of times every day.
Ice cliffs would also be a great resource for future human colonists. Easily accessible water was one of the requirements for a suitable landing site as discussed during NASA’s First Human Landing Site Workshop at the Johnson Space Center in 2015. Again, the problem here is that the ice cliffs discovered to date are a bit too far north or south for power arrays to receive sufficient sunlight. Not only that, but night temperatures at these locations are at least 50 degrees below what even the hardiest Alaskans are used to.
But finding similar ice cliffs in warmer latitudes on Mars is probably only a matter of time. If so, world space agencies may want to consider sites near these cliffs for future Mars landings, whether for robotic life detection and sample return missions, or human expeditions.