This week, one of our first year MSc students, Madeline Walters, considers the recent discovery that penitentes (pictured above) extend the altitude range of habitable environments for terrestrial bacteria. What implications could this have for other planetary environments within our solar system on the cusp of habitability?
[ Image Credit: dreamX ]
By Madeline Walters
One way to look for life beyond Earth is to see in which extreme conditions life already exists. Spread over the high altitude, extremely cold and arid wilderness of the Atacama Desert in Chile, are strange ice formations which may be important for future investigations of life beyond our planet. A study led by researchers from the University of Colorado Boulder found that these spire-like formations, called penitentes, act as a home to microbial life forms. This discovery is important for astrobiological research and implies that life may be able to form elsewhere in the solar system in similar extreme conditions.
Snow algae is commonly found in icy areas in the cryosphere, however, not so commonly at extreme elevations in hyper-arid environments. The harshness of these environments show life can form in extreme temperatures and altitudes, environments which are similar to areas on other planets in the solar system. Structures similar to penitentes found on Earth have been identified on Pluto, and perhaps on Jupiter’s moon Europa (currently a heavy debate), which points out the possibility they could exist elsewhere in the Solar System as well. In order to see if we can find similar formations on planets such as Mars, where similar extreme conditions exist, we have to understand how penitentes form.
Incoming solar radiation hits areas of lower density snow, which causes melting and sublimation-the process in which a solid directly transitions to a gas without passing through a liquid state. Once the sublimating areas begin to form, these bowl-shaped depressions which are made of very reflective ices concentrate the incoming light at the center of the depression, self-illuminating and deepening the depressions. It is within these formations that life can be found hiding from the sun.
In March 2016, Steve Schmidt, a microbial ecologist at the University of Colorado Boulder, and his team discovered red smudges on meter-tall penitentes at an elevation of around 5,300 meters. After analyzing DNA sequences of these red smudges, it turned out the samples matched that of snow algae Chlamydomonas nivalis, which was previously found living in extreme conditions on Mount Kilimanjaro, the Swiss Alps, and Antarctica.
This algae was found to be red due to the color acting as a protective barrier for the organisms-it helps to reflect some of the incoming radiation, which is re-emitted and warms the surrounding area around the algae creating liquid water. The discovery of this life living in such an extreme environment poses an important question- does this mean life can form in similar conditions off-planet? Knowing the limits and extremities in which this kind of life can exist is important for answering that question. How much radiation can this algae withstand, and to which altitude and temperatures can they survive? Although penitentes have not been conclusively found on Mars, we can model their formation on the planet using what we know about how and where they form, as well as our knowledge of Mars’ atmosphere and climate and its dust and ice interactions to perhaps one day conclusively find these structures, and perhaps more, beyond Earth.
To learn more:
UC Boulder study article:
https://eos.org/articles/microbes-spotted-on-blades-of-ice-high-in-the-andes
Europa Debate:
Reply to: Penitente formation is unlikely on Europa | Nature Geoscience
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