A thousand miles or so from the Earth’s North pole lies our planet’s largest uninhabited island, Devon Island. Devon Island is the largest uninhabited island on Earth, with a surface area of approximately 66,800 km2. Its geology presents two major provinces: a thick (presently 1. 3 km) subhorizontal sequence of Paleozoic (Cambrian to Devonian) marine sedimentary rocks dominated by carbonates (dolomite and limestone) forming part of the Arctic Platform; and a Precambrian crystalline (gneissic) basement lying unconformably under the stack of marine sediments, forming part of the Canadian Shield.
The Paleozoic sediments present a gentle dip of approximately 4 towards the west. The flat-topped plateau characterizing much of Devon Island’s surface is an old erosional surface (peneplain) exposing sediments of increasing age towards the east. Devon Island is home to one of the highest-latitude impact structures known on Earth, Haughton Crater. At 20 kilometers in diameter the crater formed 23 million years ago, at the beginning of the Miocene, when an asteroid or a comet collided with our planet. Little imagination is required to believe oneself on Mars when exploring Devon Island.
Many features and sites there are strikingly reminiscent of the Martian landscape, from barren rocky blockfields to intricate valley networks, from precipitous winding canyons to recent gully systems on their slopes. We come here to understand whether this resemblance is merely a coincidence or whether there are common underlying causes. Did some of the processes that shaped Devon Island also operate on Mars? The object that struck Devon Island was perhaps 1 kilometer (0. 6 mile) in diameter. Coming in at cosmic speeds, the impactor delivered a pulse of energy equivalent to 100 million kilotons of TNT.
In so doing, it produced a blinding flash of light followed by a monumental air blast that flattened the surroundings, obliterating almost all life several hundred kilometers around. As the impactor itself blended into the target rocks and vanished as a superheated gas, a colossal shock wave expanded into the subsurface. Rocks were crushed, melted, vaporized, and ejected. Soon, a gaping crater 20 kilometers (12. 4 miles) wide and 1. 7 kilometers (1 mile) deep appeared, only to shallow out moments later as its unstable walls collapsed inwards.
As the dust cleared, a smoldering hole filled with a vast pool of chunky molten carbonates appeared. Haughton Crater was born. Early research efforts at Haughton focused on studies of the crater itself with investigations into a possible Mars analog angle remaining unexplored. I approached Chris McKay at NASA Ames Research Center to do just that. With his visionary support, I obtained in 1997 a grant from the National Research Council to visit Haughton Crater. As a result, a four-person team traveled to Devon Island in August of that year.
Comprising this initial field party were James W. Rice, Jr. (at that time based at NASA Ames, now at Arizona State University), John W. Schutt (chief field guide for the U. S. Antarctic Search for Meteorites program), Aaron Zent (NASA Ames), and myself. The site proved interesting beyond our wildest dreams. Not just one, but several features were found that might serve as potential Mars analogs. The ground-ice on Devon Island and indeed across the high Arctic represents an important repository of freshwater and, as suggested by known examples from Siberia, might even trap a biological record covering several million years.
Recent neutron spectrometry data from the Mars Odyssey spacecraft provide startling possible evidence that ground-ice is abundantly present at shallow depth in the Martian subsurface (within the top few meters), particularly at high latitudes. While the findings of the orbiterOs science team remain preliminary, it appears that ground-ice might also be found at shallow depth at low latitudes in specific areas. If confirmed, this could have important implications both for the search for life on Mars and for planning future human endeavors on the planet.
Our studies of ground-ice on Devon could help plan for these exciting activities. Networks of channels found on Devon Island bear similarities to the so-called Martian small valley networks. On Mars, most of these features date back to the end of the “Heavy Bombardment” (a period of high impact rates early in the history of the solar system). Some of these features are also found on more recent Martian terrains such as the flanks of relatively young volcanoes. The classical interpretation of the Martian small valley networks is that they are the result of liquid water runoff flowing across the Martian surface.
This is thought to have occurred not in the form of gigantic floods (as in the case of the Martian outflow channels), but rather, as more modest trickles. The small valley networks are thought to have formed from the action of either localized rainfall, groundwater or ground-ice release, or from various forms of mud flows. All of these interpretations require a fairly warm climate on Mars for liquid water to flow (without freezing) over distances of tens to hundreds of kilometers.
There are many other features on Devon Island with eerily similar counterparts on Mars, including vast canyons and small gullies. In the end, it is perhaps not any single parallel that should impress, but the convergence of so many in a single small area of our planet. Without loosing sight of the fact that no single Mars analog on Earth can be considered ideal (it depends a lot on what one wants to study), Devon Island has come to be described by many as, and granted with much exaggeration, “Mars on Earth”.
