It’s hard to believe that nearly 35 years ago we conducted the first — and so far last — experiments to find life on Mars.
In 1976, two NASA Viking landers scooped up some orange Martian soil and attempted to incubate any native microorganisms that might be present. The results were ambiguous as best, and have been hotly debated ever since.
The Viking experiments were criticized as being too premature because in the 1970s we didn’t know very much about the Martian environment or its geological history. In fact, the Viking experiments may have actually killed exotic native life say some astrobiologists (Viking’s view of Mars is pictured below). We didn’t even know about the existence of extremophiles on Earth back then — tough microbes that adapt to hostile conditions that would normally kill us.
Before we send another biology experiment to Mars, says a team of researchers at the University of Padova, Italy, let’s build our own Martian environment in a lab and see what Earth life forms might survive. Call it a “goldfish bowl” for seeing if life can live on the edge.
Finding a life form able to survive in homemade Martian conditions may have a double payoff says the team, lead by Giuseppe Galletta. It might expand our understanding of the limits of environments where life can survive.
The experiments would also define the limits for how easy or hard it would be to accidentally contaminate Mars with Earth bugs.
The small Martian environment simulators they built (pictured top), called LISA and mini-LISA (Laboratorio Italiano Simulazione Ambienti), make an attempt at duplicating Martian surface conditions.
Inside the mini-Mars habitats, temperature ranges from a maximum of near-freezing in the tropical Martian summer to –200 degrees Fahrenheit (-130°C) in the harsh polar winter. Air pressure is kept at an anemic fraction of a percent of Earth’s surface pressure. The bottled atmosphere is 95 percent carbon dioxide with trace elements. Searing ultraviolet (UV) light floods the habitat.
What’s handy is there are no time limits on the experiments. The mini-Mars world is refueled with liquid nitrogen weekly to keep it chilly.
Experiments to date show that some bacteria strains can survive the freezing temperatures, low pressure and bone-dry atmosphere. Without water, the bacteria suspend their metabolism and build endospores, dormant non-reproductive structures with a thick wall for protecting DNA.
But UV light is a bug-killer after just a few minutes of exposure. When UV light is removed from the mini-lab — to simulate could happen during the night or in the shadow of rocks — the spores appears to remain stable, say the researchers. The spores become activated again when liquid water is added.
The team simulated the dust coverage that’s common on Mars by blowing on the samples with grains of volcanic ash from Etna Volcano eruptions, or red iron oxide dust used in industrial color production. This UV insulator allowed the bacterial to survive for longer periods.
Today we know that the Martian past environment was similar to early Earth’s. Fossil evidence shows that life on Earth appeared soon after the formation of the oceans, about 3.8 billion years ago. Similar conditions probably existed on Mars at the same time. Volcanoes spewed carbon dioxide into the atmosphere to create a greenhouse effect. This kept atmospheric pressure high enough to maintain liquid water on the surface.
But the volcanoes shut down, the atmosphere thinned, and surface water froze solid. Today the surface is more like a very cold desert that is blasted by intense solar ultraviolet radiation.
The awesome power of biological evolution tells us that any Martian microorganisms would have had time to adapt to the global deep-freeze. They could have moved to ecological niches, inches under the soil or deep under the surface where water could be present, along with warmer temperatures.
The discovery of water in the Martian permafrost by NASA’s Mars Phoenix Lander, and the suspected detection of methane in the Martian atmosphere from Earth-based observations, points to a potentially active Mars subsurface biosphere.
Whenever we do get around to sending another miniature biolab to the Red Planet, we’ll hopefully have a much better understanding of what to test for.
Image credits: University of Padova, NASA