What we know... 
These two images of the same spot on Mars taken years apart, show the formation of a bright gully on the wall
of a crater. One possibility is that this gully formed by the eruption of water or brine to the surface. This image indicates that the subsurface of Mars is likely very different from the surface and provides additional evidence for the importance of subsurface exploration on Mars, such as that to be conducted by Inukshuk. If the gully formed from water erupting onto the surface, studying Mars
analogue sites such as East German Creek in Manitoba, will help us
better understand how such features might form on Mars.
The Inukshuk Canadian Mars lander is designed to give us a glimpse of what lurks beneath the Martian surface. We know that the surface of Mars (the parts that we have seen from previous landers) is covered in rocks and wind-blown dust.
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| This image shows a Mars analogue site located in west-central Manitoba (East German Creek). The site is heavily stained by iron oxides, giving it a red, Mars-like appearance. There are a number of very salty springs at the site that bring various dissolved minerals to the surface. Some of the springs also contain mats of floating algae, while other nearby springs are barren. By studying Mars analogue sites (a number of which are located in Canada), Canadian scientists can gain a better understanding of what sorts of science experiments are best for looking for signs of life on Mars. |
The surface of Mars is an inhospitable place. The Martian atmosphere is composed almost totally of carbon dioxide and is very thin, less than 1% of the atmospheric pressure of the Earth’s surface. Temperatures on Mars are extreme, ranging from as low as -150º C in the middle of a winter’s night near the poles to a more hospitable 20º C in the middle of summer at the equator. Mars also does not have a protective ozone layer, so the Sun’s ultraviolet light reaches the surface of the planet.
In spite of these extreme conditions, most scientists believe that if life ever did evolve on Mars it might still survive by migrating to “oases” where conditions are not as extreme and where hardy microbes could survive, probably in a state of “suspended animation”. Scientists have found hardy bacteria and other simple life forms, what we call “extremophiles”, living in some pretty nasty environments: in the bottom of the ocean around hydrothermal vents, in springs that are saltier than the ocean, at the Earth’s surface around geysers, and even inside rocks in the high Canadian Arctic where temperatures rarely exceed 0º C. Canada is one of the leaders in research on Mars analogue environments – studying the diversity and extremity of terrestrial environments where life thrives.
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| The McMurdo dry valleys in Antarctica are a good terrestrial analogue of Mars because they rarely get above 0°C and yet harbour life. |
Mars scientists are gathering increasing evidence that early in Mars history conditions on the planet were much more Earth-like. The oldest parts of Mars contain some areas that are covered in clay minerals. Clay minerals are important signposts to conditions on early Mars because: (1) they contain water; (2) they likely formed in standing bodies of water; and (3) life may have required the presence of clays to bring together the organic molecules that led to the evolution of life.
At present however, any organic molecules or bioorganisms that may be sitting on the Martian surface would not survive for long. The temperature swings, temperature extremes, low atmospheric pressure, and intense ultraviolet bombardment all conspire to make things difficult for any organisms sitting on the Martian surface. Therefore, in order for organisms to survive, they would need to migrate to the subsurface. Just beneath the surface, organisms would be protected from ultraviolet radiation, and temperature swings would be less. Conditions would still be difficult but not as bad as at the surface.
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McMurdo rock rinds: life manages to survive in the harsh environment of Antarctica's dry valleys. One adaptation strategy is to colonize the interior of rocks, just below the surface. In this way they |
Given all these factors, most scientists believe that our best chance of finding life on Mars is to look beneath the surface. The Inukshuk mission is designed to do just this: drill a series of holes down to about 1 metre around the Inukshuk landing site (which will likely be targeted for the scientifically most interesting oldest terrains on Mars).
The Inukshuk lander will have a number of unique instruments and capabilities. It will be equipped with a floating aerostat that will give a bird’s eye view of the area around the rover (from a height of about 5-10 metres). This view will help the rover avoid hazards such as big rocks and sand dunes, help the mission scientists to identify interesting features that the rover could investigate close-up, and pick locations at which to drill.
Since conditions between the surface and near-subsurface can vary dramatically and that any life that exists on Mars may be in a precarious condition (ideally adapted to its habitat but unable to survive at the surface), the Inukshuk rover will investigate the subsurface in situ; in other words, we will take the instruments to the samples rather than bringing the samples to the instruments. To do this, we will equip the driller with windows that will allow us to look at the sides of the drill hole as we drill down. In this way, we do not need to bring samples to the surface, where they might undergo unwanted changes. This rationale applies to both searching for subsurface organisms or biomolecules, as well as mapping the subsurface geology. As was the case for organisms, many minerals could undergo changes when removed from the subsurface and exposed to the harsher surface conditions.
The overall goal of the Inukshuk mission is to characterize the surface and subsurface around the landing site, to look for signs of past or present life and to determine whether subsurface conditions were ever favourable for life.
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